-This is Info file bashref.info, produced by Makeinfo-1.64 from the
-input file ./bashref.texi.
+This is bashref.info, produced by makeinfo version 4.11 from
+/Users/chet/src/bash/src/doc/bashref.texi.
This text is a brief description of the features that are present in
-the Bash shell.
+the Bash shell (version 4.0, 28 October 2008).
-This is Edition 2.0, last updated 19 May 1997,
-of `The GNU Bash Reference Manual',
-for `Bash', Version 2.01.
+ This is Edition 4.0, last updated 28 October 2008, of `The GNU Bash
+Reference Manual', for `Bash', Version 4.0.
-Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
+ Copyright (C) 1988-2008 Free Software Foundation, Inc.
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
+ Permission is granted to make and distribute verbatim copies of this
+manual provided the copyright notice and this permission notice are
+preserved on all copies.
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
+ Permission is granted to copy, distribute and/or modify this
+ document under the terms of the GNU Free Documentation License,
+ Version 1.2 or any later version published by the Free Software
+ Foundation; with no Invariant Sections, with the Front-Cover texts
+ being "A GNU Manual", and with the Back-Cover Texts as in (a)
+ below. A copy of the license is included in the section entitled
+ "GNU Free Documentation License".
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Foundation.
+ (a) The FSF's Back-Cover Text is: You are free to copy and modify
+ this GNU manual. Buying copies from GNU Press supports the FSF in
+ developing GNU and promoting software freedom."
+
+
+INFO-DIR-SECTION Basics
+START-INFO-DIR-ENTRY
+* Bash: (bash). The GNU Bourne-Again SHell.
+END-INFO-DIR-ENTRY
\1f
File: bashref.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
Bash Features
*************
- This text is a brief description of the features that are present in
-the Bash shell.
-
- This is Edition 2.0, last updated 19 May 1997, of `The GNU Bash
-Reference Manual', for `Bash', Version 2.01.
+This text is a brief description of the features that are present in
+the Bash shell (version 4.0, 28 October 2008).
- Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
+ This is Edition 4.0, last updated 28 October 2008, of `The GNU Bash
+Reference Manual', for `Bash', Version 4.0.
Bash contains features that appear in other popular shells, and some
features that only appear in Bash. Some of the shells that Bash has
* Menu:
* Introduction:: An introduction to the shell.
-
* Definitions:: Some definitions used in the rest of this
manual.
-
* Basic Shell Features:: The shell "building blocks".
-
-* Bourne Shell Features:: Features similar to those found in the
- Bourne shell.
-
-* Csh Features:: Features originally found in the
- Berkeley C-Shell.
-
-* Korn Shell Features:: Features originally found in the Korn
- Shell.
-
+* Shell Builtin Commands:: Commands that are a part of the shell.
+* Shell Variables:: Variables used or set by Bash.
* Bash Features:: Features found only in Bash.
-
-* Job Control:: A chapter describing what job control is
- and how Bash allows you to use it.
-
-* Using History Interactively:: Chapter dealing with history expansion
- rules.
-
+* Job Control:: What job control is and how Bash allows you
+ to use it.
* Command Line Editing:: Chapter describing the command line
editing features.
-
+* Using History Interactively:: Command History Expansion
* Installing Bash:: How to build and install Bash on your system.
-
* Reporting Bugs:: How to report bugs in Bash.
-
-* Builtin Index:: Index of Bash builtin commands.
-
-* Reserved Word Index:: Index of Bash reserved words.
-
-* Variable Index:: Quick reference helps you find the
- variable you want.
-
-* Function Index:: Index of bindable Readline functions.
-
-* Concept Index:: General index for concepts described in
- this manual.
+* Major Differences From The Bourne Shell:: A terse list of the differences
+ between Bash and historical
+ versions of /bin/sh.
+* GNU Free Documentation License:: Copying and sharing this documentation.
+* Indexes:: Various indexes for this manual.
\1f
File: bashref.info, Node: Introduction, Next: Definitions, Prev: Top, Up: Top
-Introduction
-************
+1 Introduction
+**************
* Menu:
* What is Bash?:: A short description of Bash.
-
* What is a shell?:: A brief introduction to shells.
\1f
File: bashref.info, Node: What is Bash?, Next: What is a shell?, Up: Introduction
-What is Bash?
-=============
+1.1 What is Bash?
+=================
- Bash is the shell, or command language interpreter, that will appear
-in the GNU operating system. The name is an acronym for the
-`Bourne-Again SHell', a pun on Steve Bourne, the author of the direct
-ancestor of the current Unix shell `/bin/sh', which appeared in the
-Seventh Edition Bell Labs Research version of Unix.
+Bash is the shell, or command language interpreter, for the GNU
+operating system. The name is an acronym for the `Bourne-Again SHell',
+a pun on Stephen Bourne, the author of the direct ancestor of the
+current Unix shell `sh', which appeared in the Seventh Edition Bell
+Labs Research version of Unix.
- Bash is an `sh'-compatible shell that incorporates useful features
-from the Korn shell `ksh' and the C shell `csh'. It is ultimately
+ Bash is largely compatible with `sh' and incorporates useful
+features from the Korn shell `ksh' and the C shell `csh'. It is
intended to be a conformant implementation of the IEEE POSIX Shell and
-Tools specification (IEEE Working Group 1003.2). It offers functional
-improvements over `sh' for both interactive and programming use.
+Tools portion of the IEEE POSIX specification (IEEE Standard 1003.1).
+It offers functional improvements over `sh' for both interactive and
+programming use.
- While the GNU operating system will include a version of `csh', Bash
-will be the default shell. Like other GNU software, Bash is quite
-portable. It currently runs on nearly every version of Unix and a few
-other operating systems - independently-supported ports exist for OS/2
-and Windows NT.
+ While the GNU operating system provides other shells, including a
+version of `csh', Bash is the default shell. Like other GNU software,
+Bash is quite portable. It currently runs on nearly every version of
+Unix and a few other operating systems - independently-supported ports
+exist for MS-DOS, OS/2, and Windows platforms.
\1f
File: bashref.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
-What is a shell?
-================
+1.2 What is a shell?
+====================
- At its base, a shell is simply a macro processor that executes
-commands. A Unix shell is both a command interpreter, which provides
-the user interface to the rich set of Unix utilities, and a programming
-language, allowing these utilitites to be combined. The shell reads
-commands either from a terminal or a file. Files containing commands
-can be created, and become commands themselves. These new commands
-have the same status as system commands in directories like `/bin',
-allowing users or groups to establish custom environments.
-
- A shell allows execution of Unix commands, both synchronously and
-asynchronously. The "redirection" constructs permit fine-grained
-control of the input and output of those commands, and the shell allows
-control over the contents of their environment. Unix shells also
-provide a small set of built-in commands ("builtins") implementing
-functionality impossible (e.g., `cd', `break', `continue', and `exec'),
-or inconvenient (`history', `getopts', `kill', or `pwd', for example)
-to obtain via separate utilities. Shells may be used interactively or
-non-interactively: they accept input typed from the keyboard or from a
-file. All of the shell builtins are described in subsequent sections.
+At its base, a shell is simply a macro processor that executes
+commands. The term macro processor means functionality where text and
+symbols are expanded to create larger expressions.
+
+ A Unix shell is both a command interpreter and a programming
+language. As a command interpreter, the shell provides the user
+interface to the rich set of GNU utilities. The programming language
+features allow these utilities to be combined. Files containing
+commands can be created, and become commands themselves. These new
+commands have the same status as system commands in directories such as
+`/bin', allowing users or groups to establish custom environments to
+automate their common tasks.
+
+ Shells may be used interactively or non-interactively. In
+interactive mode, they accept input typed from the keyboard. When
+executing non-interactively, shells execute commands read from a file.
+
+ A shell allows execution of GNU commands, both synchronously and
+asynchronously. The shell waits for synchronous commands to complete
+before accepting more input; asynchronous commands continue to execute
+in parallel with the shell while it reads and executes additional
+commands. The "redirection" constructs permit fine-grained control of
+the input and output of those commands. Moreover, the shell allows
+control over the contents of commands' environments.
+
+ Shells also provide a small set of built-in commands ("builtins")
+implementing functionality impossible or inconvenient to obtain via
+separate utilities. For example, `cd', `break', `continue', and
+`exec') cannot be implemented outside of the shell because they
+directly manipulate the shell itself. The `history', `getopts',
+`kill', or `pwd' builtins, among others, could be implemented in
+separate utilities, but they are more convenient to use as builtin
+commands. All of the shell builtins are described in subsequent
+sections.
While executing commands is essential, most of the power (and
complexity) of shells is due to their embedded programming languages.
Like any high-level language, the shell provides variables, flow
control constructs, quoting, and functions.
- Shells have begun offering features geared specifically for
-interactive use rather than to augment the programming language. These
-interactive features include job control, command line editing, history
-and aliases. Each of these features is described in this manual.
+ Shells offer features geared specifically for interactive use rather
+than to augment the programming language. These interactive features
+include job control, command line editing, command history and aliases.
+Each of these features is described in this manual.
\1f
File: bashref.info, Node: Definitions, Next: Basic Shell Features, Prev: Introduction, Up: Top
-Definitions
-***********
+2 Definitions
+*************
- These definitions are used throughout the remainder of this manual.
+These definitions are used throughout the remainder of this manual.
`POSIX'
A family of open system standards based on Unix. Bash is
- concerned with POSIX 1003.2, the Shell and Tools Standard.
+ primarily concerned with the Shell and Utilities portion of the
+ POSIX 1003.1 standard.
`blank'
A space or tab character.
rather than by an executable program somewhere in the file system.
`control operator'
- A `word' that performs a control function. It is a `newline' or
- one of the following: `||', `&&', `&', `;', `;;', `|', `(', or `)'.
+ A `token' that performs a control function. It is a `newline' or
+ one of the following: `||', `&&', `&', `;', `;;', `|', `|&', `(',
+ or `)'.
`exit status'
- The value returned by a command to its caller.
+ The value returned by a command to its caller. The value is
+ restricted to eight bits, so the maximum value is 255.
`field'
A unit of text that is the result of one of the shell expansions.
`operator'
A `control operator' or a `redirection operator'. *Note
- Redirections::, for a list of redirection operators.
+ Redirections::, for a list of redirection operators. Operators
+ contain at least one unquoted `metacharacter'.
`process group'
A collection of related processes each having the same process
group ID.
`process group ID'
- A unique identifer that represents a `process group' during its
+ A unique identifier that represents a `process group' during its
lifetime.
`reserved word'
A synonym for `exit status'.
`signal'
- A mechanism by which a process may be notified by the kernal of an
+ A mechanism by which a process may be notified by the kernel of an
event occurring in the system.
`special builtin'
A shell builtin command that has been classified as special by the
- POSIX.2 standard.
+ POSIX standard.
`token'
A sequence of characters considered a single unit by the shell.
It is either a `word' or an `operator'.
`word'
- A `token' that is not an `operator'.
+ A sequence of characters treated as a unit by the shell. Words
+ may not include unquoted `metacharacters'.
\1f
-File: bashref.info, Node: Basic Shell Features, Next: Bourne Shell Features, Prev: Definitions, Up: Top
+File: bashref.info, Node: Basic Shell Features, Next: Shell Builtin Commands, Prev: Definitions, Up: Top
-Basic Shell Features
-********************
+3 Basic Shell Features
+**********************
- Bash is an acronym for `Bourne-Again SHell'. The Bourne shell is
-the traditional Unix shell originally written by Stephen Bourne. All
-of the Bourne shell builtin commands are available in Bash, and the
-rules for evaluation and quoting are taken from the POSIX 1003.2
-specification for the `standard' Unix shell.
+Bash is an acronym for `Bourne-Again SHell'. The Bourne shell is the
+traditional Unix shell originally written by Stephen Bourne. All of
+the Bourne shell builtin commands are available in Bash, The rules for
+evaluation and quoting are taken from the POSIX specification for the
+`standard' Unix shell.
- This chapter briefly summarizes the shell's "building blocks":
+ This chapter briefly summarizes the shell's `building blocks':
commands, control structures, shell functions, shell parameters, shell
expansions, redirections, which are a way to direct input and output
from and to named files, and how the shell executes commands.
* Menu:
* Shell Syntax:: What your input means to the shell.
-* Simple Commands:: The most common type of command.
-* Pipelines:: Connecting the input and output of several
- commands.
-* Lists:: How to execute commands sequentially.
-* Looping Constructs:: Shell commands for iterative action.
-* Conditional Constructs:: Shell commands for conditional execution.
-* Command Grouping:: Ways to group commands.
+* Shell Commands:: The types of commands you can use.
* Shell Functions:: Grouping commands by name.
-* Shell Parameters:: Special shell variables.
-* Shell Expansions:: How Bash expands variables and the various
+* Shell Parameters:: How the shell stores values.
+* Shell Expansions:: How Bash expands parameters and the various
expansions available.
* Redirections:: A way to control where input and output go.
* Executing Commands:: What happens when you run a command.
* Shell Scripts:: Executing files of shell commands.
\1f
-File: bashref.info, Node: Shell Syntax, Next: Simple Commands, Up: Basic Shell Features
+File: bashref.info, Node: Shell Syntax, Next: Shell Commands, Up: Basic Shell Features
-Shell Syntax
-============
+3.1 Shell Syntax
+================
* Menu:
* Shell Operation:: The basic operation of the shell.
-
* Quoting:: How to remove the special meaning from characters.
-
* Comments:: How to specify comments.
+ When the shell reads input, it proceeds through a sequence of
+operations. If the input indicates the beginning of a comment, the
+shell ignores the comment symbol (`#'), and the rest of that line.
+
+ Otherwise, roughly speaking, the shell reads its input and divides
+the input into words and operators, employing the quoting rules to
+select which meanings to assign various words and characters.
+
+ The shell then parses these tokens into commands and other
+constructs, removes the special meaning of certain words or characters,
+expands others, redirects input and output as needed, executes the
+specified command, waits for the command's exit status, and makes that
+exit status available for further inspection or processing.
+
\1f
File: bashref.info, Node: Shell Operation, Next: Quoting, Up: Shell Syntax
-Shell Operation
----------------
+3.1.1 Shell Operation
+---------------------
- The following is a brief description of the shell's operation when it
+The following is a brief description of the shell's operation when it
reads and executes a command. Basically, the shell does the following:
- 1. Reads its input from a file (*note Shell Scripts::.), from a string
+ 1. Reads its input from a file (*note Shell Scripts::), from a string
supplied as an argument to the `-c' invocation option (*note
- Invoking Bash::.), or from the user's terminal.
+ Invoking Bash::), or from the user's terminal.
2. Breaks the input into words and operators, obeying the quoting
- rules described in *Note Quoting::. Tokens are separated by
+ rules described in *note Quoting::. These tokens are separated by
`metacharacters'. Alias expansion is performed by this step
- (*note Aliases::.).
+ (*note Aliases::).
- 3. Parses the tokens into simple and compound commands.
+ 3. Parses the tokens into simple and compound commands (*note Shell
+ Commands::).
- 4. Performs the various shell expansions (*note Shell Expansions::.),
+ 4. Performs the various shell expansions (*note Shell Expansions::),
breaking the expanded tokens into lists of filenames (*note
- Filename Expansion::.) and commands and arguments.
+ Filename Expansion::) and commands and arguments.
- 5. Performs any necessary redirections (*note Redirections::.) and
+ 5. Performs any necessary redirections (*note Redirections::) and
removes the redirection operators and their operands from the
argument list.
- 6. Executes the command (*note Executing Commands::.).
+ 6. Executes the command (*note Executing Commands::).
7. Optionally waits for the command to complete and collects its exit
- status.
+ status (*note Exit Status::).
\1f
File: bashref.info, Node: Quoting, Next: Comments, Prev: Shell Operation, Up: Shell Syntax
-Quoting
--------
+3.1.2 Quoting
+-------------
* Menu:
* Double Quotes:: How to suppress most of the interpretation of a
sequence of characters.
* ANSI-C Quoting:: How to expand ANSI-C sequences in quoted strings.
-
* Locale Translation:: How to translate strings into different languages.
Quoting is used to remove the special meaning of certain characters
treatment for special characters, to prevent reserved words from being
recognized as such, and to prevent parameter expansion.
- Each of the shell `metacharacters' (*note Definitions::.) has
-special meaning to the shell and must be quoted if they are to
-represent themselves. There are three quoting mechanisms: the ESCAPE
-CHARACTER, single quotes, and double quotes.
+ Each of the shell metacharacters (*note Definitions::) has special
+meaning to the shell and must be quoted if it is to represent itself.
+When the command history expansion facilities are being used (*note
+History Interaction::), the HISTORY EXPANSION character, usually `!',
+must be quoted to prevent history expansion. *Note Bash History
+Facilities::, for more details concerning history expansion.
+
+ There are three quoting mechanisms: the ESCAPE CHARACTER, single
+quotes, and double quotes.
\1f
File: bashref.info, Node: Escape Character, Next: Single Quotes, Up: Quoting
-Escape Character
-................
+3.1.2.1 Escape Character
+........................
- A non-quoted backslash `\' is the Bash escape character. It
-preserves the literal value of the next character that follows, with
-the exception of `newline'. If a `\newline' pair appears, and the
-backslash is not quoted, the `\newline' is treated as a line
-continuation (that is, it is effectively ignored).
+A non-quoted backslash `\' is the Bash escape character. It preserves
+the literal value of the next character that follows, with the
+exception of `newline'. If a `\newline' pair appears, and the
+backslash itself is not quoted, the `\newline' is treated as a line
+continuation (that is, it is removed from the input stream and
+effectively ignored).
\1f
File: bashref.info, Node: Single Quotes, Next: Double Quotes, Prev: Escape Character, Up: Quoting
-Single Quotes
-.............
+3.1.2.2 Single Quotes
+.....................
- Enclosing characters in single quotes preserves the literal value of
-each character within the quotes. A single quote may not occur between
-single quotes, even when preceded by a backslash.
+Enclosing characters in single quotes (`'') preserves the literal value
+of each character within the quotes. A single quote may not occur
+between single quotes, even when preceded by a backslash.
\1f
File: bashref.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
-Double Quotes
-.............
+3.1.2.3 Double Quotes
+.....................
- Enclosing characters in double quotes preserves the literal value of
-all characters within the quotes, with the exception of `$', ``', and
-`\'. The characters `$' and ``' retain their special meaning within
-double quotes. The backslash retains its special meaning only when
+Enclosing characters in double quotes (`"') preserves the literal value
+of all characters within the quotes, with the exception of `$', ``',
+`\', and, when history expansion is enabled, `!'. The characters `$'
+and ``' retain their special meaning within double quotes (*note Shell
+Expansions::). The backslash retains its special meaning only when
followed by one of the following characters: `$', ``', `"', `\', or
-`newline'. A double quote may be quoted within double quotes by
-preceding it with a backslash.
+`newline'. Within double quotes, backslashes that are followed by one
+of these characters are removed. Backslashes preceding characters
+without a special meaning are left unmodified. A double quote may be
+quoted within double quotes by preceding it with a backslash. If
+enabled, history expansion will be performed unless an `!' appearing in
+double quotes is escaped using a backslash. The backslash preceding
+the `!' is not removed.
The special parameters `*' and `@' have special meaning when in
-double quotes (*note Shell Parameter Expansion::.).
+double quotes (*note Shell Parameter Expansion::).
\1f
File: bashref.info, Node: ANSI-C Quoting, Next: Locale Translation, Prev: Double Quotes, Up: Quoting
-ANSI-C Quoting
-..............
+3.1.2.4 ANSI-C Quoting
+......................
- Words of the form `$'STRING'' are treated specially. The word
-expands to STRING, with backslash-escaped characters replaced as
-specifed by the ANSI C standard. Backslash escape sequences, if
-present, are decoded as follows:
+Words of the form `$'STRING'' are treated specially. The word expands
+to STRING, with backslash-escaped characters replaced as specified by
+the ANSI C standard. Backslash escape sequences, if present, are
+decoded as follows:
`\a'
alert (bell)
`\\'
backslash
+`\''
+ single quote
+
`\NNN'
- the character whose `ASCII' code is NNN in octal
+ the eight-bit character whose value is the octal value NNN (one to
+ three digits)
+
+`\xHH'
+ the eight-bit character whose value is the hexadecimal value HH
+ (one or two hex digits)
-The result is single-quoted, as if the dollar sign had not been present.
+`\cX'
+ a control-X character
+
+The expanded result is single-quoted, as if the dollar sign had not
+been present.
\1f
File: bashref.info, Node: Locale Translation, Prev: ANSI-C Quoting, Up: Quoting
-Locale-Specific Translation
-...........................
+3.1.2.5 Locale-Specific Translation
+...................................
- A double-quoted string preceded by a dollar sign (`$') will cause
-the string to be translated according to the current locale. If the
+A double-quoted string preceded by a dollar sign (`$') will cause the
+string to be translated according to the current locale. If the
current locale is `C' or `POSIX', the dollar sign is ignored. If the
string is translated and replaced, the replacement is double-quoted.
+ Some systems use the message catalog selected by the `LC_MESSAGES'
+shell variable. Others create the name of the message catalog from the
+value of the `TEXTDOMAIN' shell variable, possibly adding a suffix of
+`.mo'. If you use the `TEXTDOMAIN' variable, you may need to set the
+`TEXTDOMAINDIR' variable to the location of the message catalog files.
+Still others use both variables in this fashion:
+`TEXTDOMAINDIR'/`LC_MESSAGES'/LC_MESSAGES/`TEXTDOMAIN'.mo.
+
\1f
File: bashref.info, Node: Comments, Prev: Quoting, Up: Shell Syntax
-Comments
---------
+3.1.3 Comments
+--------------
- In a non-interactive shell, or an interactive shell in which the
+In a non-interactive shell, or an interactive shell in which the
`interactive_comments' option to the `shopt' builtin is enabled (*note
-Bash Builtins::.), a word beginning with `#' causes that word and all
-remaining characters on that line to be ignored. An interactive shell
-without the `interactive_comments' option enabled does not allow
+The Shopt Builtin::), a word beginning with `#' causes that word and
+all remaining characters on that line to be ignored. An interactive
+shell without the `interactive_comments' option enabled does not allow
comments. The `interactive_comments' option is on by default in
-interactive shells.
+interactive shells. *Note Interactive Shells::, for a description of
+what makes a shell interactive.
+
+\1f
+File: bashref.info, Node: Shell Commands, Next: Shell Functions, Prev: Shell Syntax, Up: Basic Shell Features
+
+3.2 Shell Commands
+==================
+
+A simple shell command such as `echo a b c' consists of the command
+itself followed by arguments, separated by spaces.
+
+ More complex shell commands are composed of simple commands arranged
+together in a variety of ways: in a pipeline in which the output of one
+command becomes the input of a second, in a loop or conditional
+construct, or in some other grouping.
+
+* Menu:
+
+* Simple Commands:: The most common type of command.
+* Pipelines:: Connecting the input and output of several
+ commands.
+* Lists:: How to execute commands sequentially.
+* Compound Commands:: Shell commands for control flow.
+* Coprocesses:: Two-way communication between commands.
\1f
-File: bashref.info, Node: Simple Commands, Next: Pipelines, Prev: Shell Syntax, Up: Basic Shell Features
+File: bashref.info, Node: Simple Commands, Next: Pipelines, Up: Shell Commands
-Simple Commands
-===============
+3.2.1 Simple Commands
+---------------------
- A simple command is the kind of command you'll encounter most often.
-It's just a sequence of words separated by `blank's, terminated by one
-of the shell control operators (*note Definitions::.). The first word
-generally specifies a command to be executed.
+A simple command is the kind of command encountered most often. It's
+just a sequence of words separated by `blank's, terminated by one of
+the shell's control operators (*note Definitions::). The first word
+generally specifies a command to be executed, with the rest of the
+words being that command's arguments.
- The return status (*note Exit Status::.) of a simple command is its
-exit status as provided by the POSIX.1 `waitpid' function, or 128+N if
-the command was terminated by signal N.
+ The return status (*note Exit Status::) of a simple command is its
+exit status as provided by the POSIX 1003.1 `waitpid' function, or
+128+N if the command was terminated by signal N.
\1f
-File: bashref.info, Node: Pipelines, Next: Lists, Prev: Simple Commands, Up: Basic Shell Features
+File: bashref.info, Node: Pipelines, Next: Lists, Prev: Simple Commands, Up: Shell Commands
-Pipelines
-=========
+3.2.2 Pipelines
+---------------
- A `pipeline' is a sequence of simple commands separated by `|'.
+A `pipeline' is a sequence of simple commands separated by one of the
+control operators `|' or `|&'.
The format for a pipeline is
- [`time' [`-p']] [`!'] COMMAND1 [`|' COMMAND2 ...]
+ [`time' [`-p']] [`!'] COMMAND1 [ [`|' or `|&'] COMMAND2 ...]
-The output of each command in the pipeline is connected to the input of
-the next command. That is, each command reads the previous command's
-output.
+The output of each command in the pipeline is connected via a pipe to
+the input of the next command. That is, each command reads the
+previous command's output. This connection is performed before any
+redirections specified by the command.
+
+ If `|&' is used, the standard error of COMMAND1 is connected to
+COMMAND2's standard input through the pipe; it is shorthand for `2>&1
+|'. This implicit redirection of the standard error is performed after
+any redirections specified by the command.
The reserved word `time' causes timing statistics to be printed for
-the pipeline once it finishes. The `-p' option changes the output
-format to that specified by POSIX. The `TIMEFORMAT' variable may be
-set to a format string that specifies how the timing information should
-be displayed. *Note Bash Variables::, for a description of the
-available formats.
+the pipeline once it finishes. The statistics currently consist of
+elapsed (wall-clock) time and user and system time consumed by the
+command's execution. The `-p' option changes the output format to that
+specified by POSIX. The `TIMEFORMAT' variable may be set to a format
+string that specifies how the timing information should be displayed.
+*Note Bash Variables::, for a description of the available formats.
+The use of `time' as a reserved word permits the timing of shell
+builtins, shell functions, and pipelines. An external `time' command
+cannot time these easily.
+
+ If the pipeline is not executed asynchronously (*note Lists::), the
+shell waits for all commands in the pipeline to complete.
- Each command in a pipeline is executed in its own subshell. The exit
-status of a pipeline is the exit status of the last command in the
-pipeline. If the reserved word `!' precedes the pipeline, the exit
-status is the logical NOT of the exit status of the last command.
+ Each command in a pipeline is executed in its own subshell (*note
+Command Execution Environment::). The exit status of a pipeline is the
+exit status of the last command in the pipeline, unless the `pipefail'
+option is enabled (*note The Set Builtin::). If `pipefail' is enabled,
+the pipeline's return status is the value of the last (rightmost)
+command to exit with a non-zero status, or zero if all commands exit
+successfully. If the reserved word `!' precedes the pipeline, the exit
+status is the logical negation of the exit status as described above.
+The shell waits for all commands in the pipeline to terminate before
+returning a value.
\1f
-File: bashref.info, Node: Lists, Next: Looping Constructs, Prev: Pipelines, Up: Basic Shell Features
+File: bashref.info, Node: Lists, Next: Compound Commands, Prev: Pipelines, Up: Shell Commands
-Lists of Commands
-=================
+3.2.3 Lists of Commands
+-----------------------
- A `list' is a sequence of one or more pipelines separated by one of
-the operators `;', `&', `&&', or `||', and optionally terminated by one
-of `;', `&', or a `newline'.
+A `list' is a sequence of one or more pipelines separated by one of the
+operators `;', `&', `&&', or `||', and optionally terminated by one of
+`;', `&', or a `newline'.
Of these list operators, `&&' and `||' have equal precedence,
followed by `;' and `&', which have equal precedence.
+ A sequence of one or more newlines may appear in a `list' to delimit
+commands, equivalent to a semicolon.
+
If a command is terminated by the control operator `&', the shell
-executes the command in the BACKGROUND in a subshell. The shell does
-not wait for the command to finish, and the return status is 0 (true).
-Commands separated by a `;' are executed sequentially; the shell waits
-for each command to terminate in turn. The return status is the exit
-status of the last command executed.
+executes the command asynchronously in a subshell. This is known as
+executing the command in the BACKGROUND. The shell does not wait for
+the command to finish, and the return status is 0 (true). When job
+control is not active (*note Job Control::), the standard input for
+asynchronous commands, in the absence of any explicit redirections, is
+redirected from `/dev/null'.
- The control operators `&&' and `||' denote AND lists and OR lists,
-respectively. An AND list has the form
- COMMAND && COMMAND2
+ Commands separated by a `;' are executed sequentially; the shell
+waits for each command to terminate in turn. The return status is the
+exit status of the last command executed.
-COMMAND2 is executed if, and only if, COMMAND returns an exit status of
-zero.
+ AND and OR lists are sequences of one or more pipelines separated by
+the control operators `&&' and `||', respectively. AND and OR lists
+are executed with left associativity.
+
+ An AND list has the form
+ COMMAND1 && COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 returns an exit status
+of zero.
An OR list has the form
- COMMAND || COMMAND2
+ COMMAND1 || COMMAND2
-COMMAND2 is executed if and only if COMMAND returns a non-zero exit
+COMMAND2 is executed if, and only if, COMMAND1 returns a non-zero exit
status.
The return status of AND and OR lists is the exit status of the last
command executed in the list.
\1f
-File: bashref.info, Node: Looping Constructs, Next: Conditional Constructs, Prev: Lists, Up: Basic Shell Features
+File: bashref.info, Node: Compound Commands, Next: Coprocesses, Prev: Lists, Up: Shell Commands
-Looping Constructs
-==================
+3.2.4 Compound Commands
+-----------------------
+
+* Menu:
+
+* Looping Constructs:: Shell commands for iterative action.
+* Conditional Constructs:: Shell commands for conditional execution.
+* Command Grouping:: Ways to group commands.
+
+ Compound commands are the shell programming constructs. Each
+construct begins with a reserved word or control operator and is
+terminated by a corresponding reserved word or operator. Any
+redirections (*note Redirections::) associated with a compound command
+apply to all commands within that compound command unless explicitly
+overridden.
+
+ Bash provides looping constructs, conditional commands, and
+mechanisms to group commands and execute them as a unit.
+
+\1f
+File: bashref.info, Node: Looping Constructs, Next: Conditional Constructs, Up: Compound Commands
+
+3.2.4.1 Looping Constructs
+..........................
- Note that wherever you see a `;' in the description of a command's
-syntax, it may be replaced indiscriminately with one or more newlines.
+Bash supports the following looping constructs.
- Bash supports the following looping constructs.
+ Note that wherever a `;' appears in the description of a command's
+syntax, it may be replaced with one or more newlines.
`until'
The syntax of the `until' command is:
until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
- Execute CONSEQUENT-COMMANDS as long as the final command in
- TEST-COMMANDS has an exit status which is not zero.
+ Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+ status which is not zero. The return status is the exit status of
+ the last command executed in CONSEQUENT-COMMANDS, or zero if none
+ was executed.
`while'
The syntax of the `while' command is:
while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
- Execute CONSEQUENT-COMMANDS as long as the final command in
- TEST-COMMANDS has an exit status of zero.
+ Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+ status of zero. The return status is the exit status of the last
+ command executed in CONSEQUENT-COMMANDS, or zero if none was
+ executed.
`for'
The syntax of the `for' command is:
for NAME [in WORDS ...]; do COMMANDS; done
- Execute COMMANDS for each member in WORDS, with NAME bound to the
- current member. If `in WORDS' is not present, `in "$@"' is
- assumed.
-
- The `break' and `continue' builtins (*note Bourne Shell Builtins::.)
+ Expand WORDS, and execute COMMANDS once for each member in the
+ resultant list, with NAME bound to the current member. If `in
+ WORDS' is not present, the `for' command executes the COMMANDS
+ once for each positional parameter that is set, as if `in "$@"'
+ had been specified (*note Special Parameters::). The return
+ status is the exit status of the last command that executes. If
+ there are no items in the expansion of WORDS, no commands are
+ executed, and the return status is zero.
+
+ An alternate form of the `for' command is also supported:
+
+ for (( EXPR1 ; EXPR2 ; EXPR3 )) ; do COMMANDS ; done
+ First, the arithmetic expression EXPR1 is evaluated according to
+ the rules described below (*note Shell Arithmetic::). The
+ arithmetic expression EXPR2 is then evaluated repeatedly until it
+ evaluates to zero. Each time EXPR2 evaluates to a non-zero value,
+ COMMANDS are executed and the arithmetic expression EXPR3 is
+ evaluated. If any expression is omitted, it behaves as if it
+ evaluates to 1. The return value is the exit status of the last
+ command in LIST that is executed, or false if any of the
+ expressions is invalid.
+
+
+ The `break' and `continue' builtins (*note Bourne Shell Builtins::)
may be used to control loop execution.
\1f
-File: bashref.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Basic Shell Features
+File: bashref.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Compound Commands
-Conditional Constructs
-======================
+3.2.4.2 Conditional Constructs
+..............................
`if'
The syntax of the `if' command is:
[else ALTERNATE-CONSEQUENTS;]
fi
- Execute CONSEQUENT-COMMANDS only if the final command in
- TEST-COMMANDS has an exit status of zero. Otherwise, each `elif'
- list is executed in turn, and if its exit status is zero, the
- corresponding MORE-CONSEQUENTS is executed and the command
- completes. If `else ALTERNATE-CONSEQUENTS' is present, and the
- final command in the final `if' or `elif' clause has a non-zero
- exit status, then execute ALTERNATE-CONSEQUENTS.
+ The TEST-COMMANDS list is executed, and if its return status is
+ zero, the CONSEQUENT-COMMANDS list is executed. If TEST-COMMANDS
+ returns a non-zero status, each `elif' list is executed in turn,
+ and if its exit status is zero, the corresponding MORE-CONSEQUENTS
+ is executed and the command completes. If `else
+ ALTERNATE-CONSEQUENTS' is present, and the final command in the
+ final `if' or `elif' clause has a non-zero exit status, then
+ ALTERNATE-CONSEQUENTS is executed. The return status is the exit
+ status of the last command executed, or zero if no condition
+ tested true.
`case'
The syntax of the `case' command is:
- `case WORD in [ ( PATTERN [| PATTERN]...) COMMANDS ;;]... esac'
+ `case WORD in [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]... esac'
- Selectively execute COMMANDS based upon WORD matching PATTERN.
- The `|' is used to separate multiple patterns.
+ `case' will selectively execute the COMMAND-LIST corresponding to
+ the first PATTERN that matches WORD. If the shell option
+ `nocasematch' (see the description of `shopt' in *note The Shopt
+ Builtin::) is enabled, the match is performed without regard to
+ the case of alphabetic characters. The `|' is used to separate
+ multiple patterns, and the `)' operator terminates a pattern list.
+ A list of patterns and an associated command-list is known as a
+ CLAUSE.
+
+ Each clause must be terminated with `;;', `,&', or `;;&'. The
+ WORD undergoes tilde expansion, parameter expansion, command
+ substitution, arithmetic expansion, and quote removal before
+ matching is attempted. Each PATTERN undergoes tilde expansion,
+ parameter expansion, command substitution, and arithmetic
+ expansion.
+
+ There may be an arbitrary number of `case' clauses, each terminated
+ by a `;;', `;&', or `;;&'. The first pattern that matches
+ determines the command-list that is executed.
Here is an example using `case' in a script that could be used to
describe one interesting feature of an animal:
esac
echo " legs."
+ If the `;;' operator is used, no subsequent matches are attempted
+ after the first pattern match. Using `;&' in place of `;;'
+ causes execution to continue with the COMMAND-LIST associated with
+ the next clause, if any. Using `;;&' in place of `;;' causes the
+ shell to test the patterns in the next clause, if any, and execute
+ any associated COMMAND-LIST on a successful match.
+
+ The return status is zero if no PATTERN is matched. Otherwise, the
+ return status is the exit status of the COMMAND-LIST executed.
+
+`select'
+ The `select' construct allows the easy generation of menus. It
+ has almost the same syntax as the `for' command:
+
+ select NAME [in WORDS ...]; do COMMANDS; done
+
+ The list of words following `in' is expanded, generating a list of
+ items. The set of expanded words is printed on the standard error
+ output stream, each preceded by a number. If the `in WORDS' is
+ omitted, the positional parameters are printed, as if `in "$@"'
+ had been specified. The `PS3' prompt is then displayed and a line
+ is read from the standard input. If the line consists of a number
+ corresponding to one of the displayed words, then the value of
+ NAME is set to that word. If the line is empty, the words and
+ prompt are displayed again. If `EOF' is read, the `select'
+ command completes. Any other value read causes NAME to be set to
+ null. The line read is saved in the variable `REPLY'.
+
+ The COMMANDS are executed after each selection until a `break'
+ command is executed, at which point the `select' command completes.
+
+ Here is an example that allows the user to pick a filename from the
+ current directory, and displays the name and index of the file
+ selected.
+
+ select fname in *;
+ do
+ echo you picked $fname \($REPLY\)
+ break;
+ done
+
`((...))'
(( EXPRESSION ))
- The EXPRESSION is evaluated according to the rules described below
- (*note Arithmetic Evaluation::.). If the value of the expression
- is non-zero, the return status is 0; otherwise the return status
- is 1. This is exactly equivalent to
+ The arithmetic EXPRESSION is evaluated according to the rules
+ described below (*note Shell Arithmetic::). If the value of the
+ expression is non-zero, the return status is 0; otherwise the
+ return status is 1. This is exactly equivalent to
let "EXPRESSION"
+ *Note Bash Builtins::, for a full description of the `let' builtin.
+
+`[[...]]'
+ [[ EXPRESSION ]]
+
+ Return a status of 0 or 1 depending on the evaluation of the
+ conditional expression EXPRESSION. Expressions are composed of
+ the primaries described below in *note Bash Conditional
+ Expressions::. Word splitting and filename expansion are not
+ performed on the words between the `[[' and `]]'; tilde expansion,
+ parameter and variable expansion, arithmetic expansion, command
+ substitution, process substitution, and quote removal are
+ performed. Conditional operators such as `-f' must be unquoted to
+ be recognized as primaries.
+
+ When the `==' and `!=' operators are used, the string to the right
+ of the operator is considered a pattern and matched according to
+ the rules described below in *note Pattern Matching::. If the
+ shell option `nocasematch' (see the description of `shopt' in
+ *note The Shopt Builtin::) is enabled, the match is performed
+ without regard to the case of alphabetic characters. The return
+ value is 0 if the string matches (`==') or does not match
+ (`!=')the pattern, and 1 otherwise. Any part of the pattern may
+ be quoted to force it to be matched as a string.
+
+ An additional binary operator, `=~', is available, with the same
+ precedence as `==' and `!='. When it is used, the string to the
+ right of the operator is considered an extended regular expression
+ and matched accordingly (as in regex3)). The return value is 0 if
+ the string matches the pattern, and 1 otherwise. If the regular
+ expression is syntactically incorrect, the conditional
+ expression's return value is 2. If the shell option `nocasematch'
+ (see the description of `shopt' in *note The Shopt Builtin::) is
+ enabled, the match is performed without regard to the case of
+ alphabetic characters. Any part of the pattern may be quoted to
+ force it to be matched as a string. Substrings matched by
+ parenthesized subexpressions within the regular expression are
+ saved in the array variable `BASH_REMATCH'. The element of
+ `BASH_REMATCH' with index 0 is the portion of the string matching
+ the entire regular expression. The element of `BASH_REMATCH' with
+ index N is the portion of the string matching the Nth
+ parenthesized subexpression.
+
+ Expressions may be combined using the following operators, listed
+ in decreasing order of precedence:
+
+ `( EXPRESSION )'
+ Returns the value of EXPRESSION. This may be used to
+ override the normal precedence of operators.
+
+ `! EXPRESSION'
+ True if EXPRESSION is false.
+
+ `EXPRESSION1 && EXPRESSION2'
+ True if both EXPRESSION1 and EXPRESSION2 are true.
+
+ `EXPRESSION1 || EXPRESSION2'
+ True if either EXPRESSION1 or EXPRESSION2 is true.
+ The `&&' and `||' operators do not evaluate EXPRESSION2 if the
+ value of EXPRESSION1 is sufficient to determine the return value
+ of the entire conditional expression.
- The `select' construct, which allows users to choose from a list of
-items presented as a menu, is also available. *Note Korn Shell
-Constructs::, for a full description of `select'.
\1f
-File: bashref.info, Node: Command Grouping, Next: Shell Functions, Prev: Conditional Constructs, Up: Basic Shell Features
+File: bashref.info, Node: Command Grouping, Prev: Conditional Constructs, Up: Compound Commands
-Grouping Commands
-=================
+3.2.4.3 Grouping Commands
+.........................
- Bash provides two ways to group a list of commands to be executed as
-a unit. When commands are grouped, redirections may be applied to the
+Bash provides two ways to group a list of commands to be executed as a
+unit. When commands are grouped, redirections may be applied to the
entire command list. For example, the output of all the commands in
the list may be redirected to a single stream.
( LIST )
Placing a list of commands between parentheses causes a subshell
- to be created, and each of the commands to be executed in that
- subshell. Since the LIST is executed in a subshell, variable
- assignments do not remain in effect after the subshell completes.
+ environment to be created (*note Command Execution Environment::),
+ and each of the commands in LIST to be executed in that subshell.
+ Since the LIST is executed in a subshell, variable assignments do
+ not remain in effect after the subshell completes.
`{}'
{ LIST; }
Placing a list of commands between curly braces causes the list to
be executed in the current shell context. No subshell is created.
- The semicolon following LIST is required.
+ The semicolon (or newline) following LIST is required.
In addition to the creation of a subshell, there is a subtle
difference between these two constructs due to historical reasons. The
braces are `reserved words', so they must be separated from the LIST by
-`blank's. The parentheses are `operators', and are recognized as
-separate tokens by the shell even if they are not separated from the
-LIST by whitespace.
+`blank's or other shell metacharacters. The parentheses are
+`operators', and are recognized as separate tokens by the shell even if
+they are not separated from the LIST by whitespace.
The exit status of both of these constructs is the exit status of
LIST.
\1f
-File: bashref.info, Node: Shell Functions, Next: Shell Parameters, Prev: Command Grouping, Up: Basic Shell Features
+File: bashref.info, Node: Coprocesses, Prev: Compound Commands, Up: Shell Commands
+
+3.2.5 Coprocesses
+-----------------
+
+A `coprocess' is a shell command preceded by the `coproc' reserved word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the `&' control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+
+ The format for a coprocess is:
+ `coproc' [NAME] COMMAND [REDIRECTIONS]
+
+This creates a coprocess named NAME. If NAME is not supplied, the
+default name is COPROC.
+
+ When the coproc is executed, the shell creates an array variable
+(*note Arrays::) named NAME in the context of the executing shell. The
+standard output of COMMAND is connected via a pipe to a file descriptor
+in the executing shell, and that file descriptor is assigned to NAME[0].
+The standard input of COMMAND is connected via a pipe to a file
+descriptor in the executing shell, and that file descriptor is assigned
+to NAME[1]. This pipe is established before any redirections specified
+by the command (*note Redirections::). The file descriptors can be
+utilized as arguments to shell commands and redirections using standard
+word expansions.
+
+ The process id of the shell spawned to execute the coprocess is
+available as the value of the variable NAME_PID. The `wait' builtin
+command may be used to wait for the coprocess to terminate.
+
+ The return status of a coprocess is the exit status of COMMAND.
+
+\1f
+File: bashref.info, Node: Shell Functions, Next: Shell Parameters, Prev: Shell Commands, Up: Basic Shell Features
-Shell Functions
-===============
+3.3 Shell Functions
+===================
- Shell functions are a way to group commands for later execution
-using a single name for the group. They are executed just like a
-"regular" command. Shell functions are executed in the current shell
-context; no new process is created to interpret them.
+Shell functions are a way to group commands for later execution using a
+single name for the group. They are executed just like a "regular"
+command. When the name of a shell function is used as a simple command
+name, the list of commands associated with that function name is
+executed. Shell functions are executed in the current shell context;
+no new process is created to interpret them.
- Functions are declared using this syntax:
- [ `function' ] NAME () { COMMAND-LIST; }
+ Functions are declared using this syntax:
+ [ `function' ] NAME () COMPOUND-COMMAND [ REDIRECTIONS ]
This defines a shell function named NAME. The reserved word
-`function' is optional. The BODY of the function is the COMMAND-LIST
-between { and }. This list is executed whenever NAME is specified as
-the name of a command. The exit status of a function is the exit
-status of the last command executed in the body.
+`function' is optional. If the `function' reserved word is supplied,
+the parentheses are optional. The BODY of the function is the compound
+command COMPOUND-COMMAND (*note Compound Commands::). That command is
+usually a LIST enclosed between { and }, but may be any compound
+command listed above. COMPOUND-COMMAND is executed whenever NAME is
+specified as the name of a command. Any redirections (*note
+Redirections::) associated with the shell function are performed when
+the function is executed.
+
+ A function definition may be deleted using the `-f' option to the
+`unset' builtin (*note Bourne Shell Builtins::).
+
+ The exit status of a function definition is zero unless a syntax
+error occurs or a readonly function with the same name already exists.
+When executed, the exit status of a function is the exit status of the
+last command executed in the body.
+
+ Note that for historical reasons, in the most common usage the curly
+braces that surround the body of the function must be separated from
+the body by `blank's or newlines. This is because the braces are
+reserved words and are only recognized as such when they are separated
+from the command list by whitespace or another shell metacharacter.
+Also, when using the braces, the LIST must be terminated by a semicolon,
+a `&', or a newline.
When a function is executed, the arguments to the function become
the positional parameters during its execution (*note Positional
-Parameters::.). The special parameter `#' that expands to the number of
-positional parameters is updated to reflect the change. Positional
-parameter `0' is unchanged.
+Parameters::). The special parameter `#' that expands to the number of
+positional parameters is updated to reflect the change. Special
+parameter `0' is unchanged. The first element of the `FUNCNAME'
+variable is set to the name of the function while the function is
+executing. All other aspects of the shell execution environment are
+identical between a function and its caller with the exception that the
+`DEBUG' and `RETURN' traps are not inherited unless the function has
+been given the `trace' attribute using the `declare' builtin or the `-o
+functrace' option has been enabled with the `set' builtin, (in which
+case all functions inherit the `DEBUG' and `RETURN' traps). *Note
+Bourne Shell Builtins::, for the description of the `trap' builtin.
If the builtin command `return' is executed in a function, the
function completes and execution resumes with the next command after
-the function call. When a function completes, the values of the
-positional parameters and the special parameter `#' are restored to the
-values they had prior to function execution. If a numeric argument is
-given to `return', that is the function return status.
+the function call. Any command associated with the `RETURN' trap is
+executed before execution resumes. When a function completes, the
+values of the positional parameters and the special parameter `#' are
+restored to the values they had prior to the function's execution. If
+a numeric argument is given to `return', that is the function's return
+status; otherwise the function's return status is the exit status of
+the last command executed before the `return'.
Variables local to the function may be declared with the `local'
builtin. These variables are visible only to the function and the
commands it invokes.
+ Function names and definitions may be listed with the `-f' option to
+the `declare' or `typeset' builtin commands (*note Bash Builtins::).
+The `-F' option to `declare' or `typeset' will list the function names
+only (and optionally the source file and line number, if the `extdebug'
+shell option is enabled). Functions may be exported so that subshells
+automatically have them defined with the `-f' option to the `export'
+builtin (*note Bourne Shell Builtins::). Note that shell functions and
+variables with the same name may result in multiple identically-named
+entries in the environment passed to the shell's children. Care should
+be taken in cases where this may cause a problem.
+
Functions may be recursive. No limit is placed on the number of
recursive calls.
\1f
File: bashref.info, Node: Shell Parameters, Next: Shell Expansions, Prev: Shell Functions, Up: Basic Shell Features
-Shell Parameters
-================
+3.4 Shell Parameters
+====================
* Menu:
* Positional Parameters:: The shell's command-line arguments.
-* Special Parameters:: Parameters with special meanings.
+* Special Parameters:: Parameters denoted by special characters.
A PARAMETER is an entity that stores values. It can be a `name', a
-number, or one of the special characters listed below. For the shell's
-purposes, a VARIABLE is a parameter denoted by a `name'.
+number, or one of the special characters listed below. A VARIABLE is a
+parameter denoted by a `name'. A variable has a VALUE and zero or more
+ATTRIBUTES. Attributes are assigned using the `declare' builtin command
+(see the description of the `declare' builtin in *note Bash Builtins::).
A parameter is set if it has been assigned a value. The null string
is a valid value. Once a variable is set, it may be unset only by using
A variable may be assigned to by a statement of the form
NAME=[VALUE]
-
-If VALUE is not given, the variable is assigned the null string. All
+ If VALUE is not given, the variable is assigned the null string. All
VALUEs undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote removal (detailed
-below). If the variable has its `-i' attribute set (see the
-description of the `declare' builtin in *Note Bash Builtins::), then
-VALUE is subject to arithmetic expansion even if the `$((...))' syntax
-does not appear (*note Arithmetic Expansion::.). Word splitting is not
+below). If the variable has its `integer' attribute set, then VALUE is
+evaluated as an arithmetic expression even if the `$((...))' expansion
+is not used (*note Arithmetic Expansion::). Word splitting is not
performed, with the exception of `"$@"' as explained below. Filename
-expansion is not performed.
+expansion is not performed. Assignment statements may also appear as
+arguments to the `alias', `declare', `typeset', `export', `readonly',
+and `local' builtin commands.
+
+ In the context where an assignment statement is assigning a value to
+a shell variable or array index (*note Arrays::), the `+=' operator can
+be used to append to or add to the variable's previous value. When
+`+=' is applied to a variable for which the integer attribute has been
+set, VALUE is evaluated as an arithmetic expression and added to the
+variable's current value, which is also evaluated. When `+=' is
+applied to an array variable using compound assignment (*note
+Arrays::), the variable's value is not unset (as it is when using `='),
+and new values are appended to the array beginning at one greater than
+the array's maximum index (for indexed arrays), or added as additional
+key-value pairs in an associative array. When applied to a
+string-valued variable, VALUE is expanded and appended to the
+variable's value.
\1f
File: bashref.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
-Positional Parameters
----------------------
+3.4.1 Positional Parameters
+---------------------------
- A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
+A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
other than the single digit `0'. Positional parameters are assigned
from the shell's arguments when it is invoked, and may be reassigned
-using the `set' builtin command. Positional parameters may not be
-assigned to with assignment statements. The positional parameters are
-temporarily replaced when a shell function is executed (*note Shell
-Functions::.).
+using the `set' builtin command. Positional parameter `N' may be
+referenced as `${N}', or as `$N' when `N' consists of a single digit.
+Positional parameters may not be assigned to with assignment statements.
+The `set' and `shift' builtins are used to set and unset them (*note
+Shell Builtin Commands::). The positional parameters are temporarily
+replaced when a shell function is executed (*note Shell Functions::).
When a positional parameter consisting of more than a single digit
is expanded, it must be enclosed in braces.
\1f
File: bashref.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
-Special Parameters
-------------------
+3.4.2 Special Parameters
+------------------------
- The shell treats several parameters specially. These parameters may
+The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed.
`*'
`@'
Expands to the positional parameters, starting from one. When the
- expansion occurs within double quotes, each parameter expands as a
+ expansion occurs within double quotes, each parameter expands to a
separate word. That is, `"$@"' is equivalent to `"$1" "$2" ...'.
- When there are no positional parameters, `"$@"' and `$@' expand to
- nothing (i.e., they are removed).
+ If the double-quoted expansion occurs within a word, the expansion
+ of the first parameter is joined with the beginning part of the
+ original word, and the expansion of the last parameter is joined
+ with the last part of the original word. When there are no
+ positional parameters, `"$@"' and `$@' expand to nothing (i.e.,
+ they are removed).
`#'
Expands to the number of positional parameters in decimal.
pipeline.
`-'
- Expands to the current option flags as specified upon invocation,
- by the `set' builtin command, or those set by the shell itself
- (such as the `-i' option).
+ (A hyphen.) Expands to the current option flags as specified upon
+ invocation, by the `set' builtin command, or those set by the
+ shell itself (such as the `-i' option).
`$'
Expands to the process ID of the shell. In a `()' subshell, it
- expands to the process ID of the current shell, not the subshell.
+ expands to the process ID of the invoking shell, not the subshell.
`!'
Expands to the process ID of the most recently executed background
`0'
Expands to the name of the shell or shell script. This is set at
- shell initialization. If Bash is invoked with a file of commands,
- `$0' is set to the name of that file. If Bash is started with the
- `-c' option, then `$0' is set to the first argument after the
- string to be executed, if one is present. Otherwise, it is set to
- the filename used to invoke Bash, as given by argument zero.
+ shell initialization. If Bash is invoked with a file of commands
+ (*note Shell Scripts::), `$0' is set to the name of that file. If
+ Bash is started with the `-c' option (*note Invoking Bash::), then
+ `$0' is set to the first argument after the string to be executed,
+ if one is present. Otherwise, it is set to the filename used to
+ invoke Bash, as given by argument zero.
`_'
- At shell startup, set to the absolute filename of the shell or
- shell script being executed as passed in the argument list.
- Subsequently, expands to the last argument to the previous command,
- after expansion. Also set to the full filename of each command
- executed and placed in the environment exported to that command.
- When checking mail, this parameter holds the name of the mail file.
+ (An underscore.) At shell startup, set to the absolute pathname
+ used to invoke the shell or shell script being executed as passed
+ in the environment or argument list. Subsequently, expands to the
+ last argument to the previous command, after expansion. Also set
+ to the full pathname used to invoke each command executed and
+ placed in the environment exported to that command. When checking
+ mail, this parameter holds the name of the mail file.
\1f
File: bashref.info, Node: Shell Expansions, Next: Redirections, Prev: Shell Parameters, Up: Basic Shell Features
-Shell Expansions
-================
+3.5 Shell Expansions
+====================
- Expansion is performed on the command line after it has been split
-into `token's. There are seven kinds of expansion performed:
+Expansion is performed on the command line after it has been split into
+`token's. There are seven kinds of expansion performed:
* brace expansion
* tilde expansion
* Menu:
+* Brace Expansion:: Expansion of expressions within braces.
+* Tilde Expansion:: Expansion of the ~ character.
* Shell Parameter Expansion:: How Bash expands variables to their values.
* Command Substitution:: Using the output of a command as an argument.
+* Arithmetic Expansion:: How to use arithmetic in shell expansions.
* Process Substitution:: A way to write and read to and from a
command.
* Word Splitting:: How the results of expansion are split into separate
* Quote Removal:: How and when quote characters are removed from
words.
- Brace expansion, tilde expansion, and arithmetic expansion are
-described in other sections. For brace expansion, see *Note Brace
-Expansion::; for tilde expansion, see *Note Tilde Expansion::; and for
-arithmetic expansion, see *Note Arithmetic Expansion::.
-
The order of expansions is: brace expansion, tilde expansion,
parameter, variable, and arithmetic expansion and command substitution
(done in a left-to-right fashion), word splitting, and filename
On systems that can support it, there is an additional expansion
available: PROCESS SUBSTITUTION. This is performed at the same time as
-parameter, variable, and arithemtic expansion and command substitution.
+parameter, variable, and arithmetic expansion and command substitution.
Only brace expansion, word splitting, and filename expansion can
change the number of words of the expansion; other expansions expand a
single word to a single word. The only exceptions to this are the
-expansions of `"$@"' (*note Special Parameters::.) and `"${NAME[@]}"'
-(*note Arrays::.).
+expansions of `"$@"' (*note Special Parameters::) and `"${NAME[@]}"'
+(*note Arrays::).
- After all expansions, `quote removal' (*note Quote Removal::.) is
+ After all expansions, `quote removal' (*note Quote Removal::) is
performed.
\1f
-File: bashref.info, Node: Shell Parameter Expansion, Next: Command Substitution, Up: Shell Expansions
+File: bashref.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Shell Expansions
-Shell Parameter Expansion
--------------------------
+3.5.1 Brace Expansion
+---------------------
+
+Brace expansion is a mechanism by which arbitrary strings may be
+generated. This mechanism is similar to FILENAME EXPANSION (*note
+Filename Expansion::), but the file names generated need not exist.
+Patterns to be brace expanded take the form of an optional PREAMBLE,
+followed by either a series of comma-separated strings or a seqeunce
+expression between a pair of braces, followed by an optional POSTSCRIPT.
+The preamble is prefixed to each string contained within the braces, and
+the postscript is then appended to each resulting string, expanding left
+to right.
+
+ Brace expansions may be nested. The results of each expanded string
+are not sorted; left to right order is preserved. For example,
+ bash$ echo a{d,c,b}e
+ ade ace abe
+
+ A sequence expression takes the form `{X..Y[INCR]}', where X and Y
+are either integers or single characters, and INCR, an optional
+increment, is an integer. When integers are supplied, the expression
+expands to each number between X and Y, inclusive. Supplied integers
+may be prefixed with `0' to force each term to have the same width.
+When either X or Y begins with a zero, the shell attempts to force all
+generated terms to contain the same number of digits, zero-padding
+where necessary. When characters are supplied, the expression expands
+to each character lexicographically between X and Y, inclusive. Note
+that both X and Y must be of the same type. When the increment is
+supplied, it is used as the difference between each term. The default
+increment is 1 or -1 as appropriate.
+
+ Brace expansion is performed before any other expansions, and any
+characters special to other expansions are preserved in the result. It
+is strictly textual. Bash does not apply any syntactic interpretation
+to the context of the expansion or the text between the braces. To
+avoid conflicts with parameter expansion, the string `${' is not
+considered eligible for brace expansion.
+
+ A correctly-formed brace expansion must contain unquoted opening and
+closing braces, and at least one unquoted comma or a valid sequence
+expression. Any incorrectly formed brace expansion is left unchanged.
+
+ A { or `,' may be quoted with a backslash to prevent its being
+considered part of a brace expression. To avoid conflicts with
+parameter expansion, the string `${' is not considered eligible for
+brace expansion.
+
+ This construct is typically used as shorthand when the common prefix
+of the strings to be generated is longer than in the above example:
+ mkdir /usr/local/src/bash/{old,new,dist,bugs}
+ or
+ chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+
+\1f
+File: bashref.info, Node: Tilde Expansion, Next: Shell Parameter Expansion, Prev: Brace Expansion, Up: Shell Expansions
+
+3.5.2 Tilde Expansion
+---------------------
+
+If a word begins with an unquoted tilde character (`~'), all of the
+characters up to the first unquoted slash (or all characters, if there
+is no unquoted slash) are considered a TILDE-PREFIX. If none of the
+characters in the tilde-prefix are quoted, the characters in the
+tilde-prefix following the tilde are treated as a possible LOGIN NAME.
+If this login name is the null string, the tilde is replaced with the
+value of the `HOME' shell variable. If `HOME' is unset, the home
+directory of the user executing the shell is substituted instead.
+Otherwise, the tilde-prefix is replaced with the home directory
+associated with the specified login name.
+
+ If the tilde-prefix is `~+', the value of the shell variable `PWD'
+replaces the tilde-prefix. If the tilde-prefix is `~-', the value of
+the shell variable `OLDPWD', if it is set, is substituted.
+
+ If the characters following the tilde in the tilde-prefix consist of
+a number N, optionally prefixed by a `+' or a `-', the tilde-prefix is
+replaced with the corresponding element from the directory stack, as it
+would be displayed by the `dirs' builtin invoked with the characters
+following tilde in the tilde-prefix as an argument (*note The Directory
+Stack::). If the tilde-prefix, sans the tilde, consists of a number
+without a leading `+' or `-', `+' is assumed.
+
+ If the login name is invalid, or the tilde expansion fails, the word
+is left unchanged.
+
+ Each variable assignment is checked for unquoted tilde-prefixes
+immediately following a `:' or the first `='. In these cases, tilde
+expansion is also performed. Consequently, one may use file names with
+tildes in assignments to `PATH', `MAILPATH', and `CDPATH', and the
+shell assigns the expanded value.
+
+ The following table shows how Bash treats unquoted tilde-prefixes:
+
+`~'
+ The value of `$HOME'
+
+`~/foo'
+ `$HOME/foo'
+
+`~fred/foo'
+ The subdirectory `foo' of the home directory of the user `fred'
+
+`~+/foo'
+ `$PWD/foo'
+
+`~-/foo'
+ `${OLDPWD-'~-'}/foo'
+
+`~N'
+ The string that would be displayed by `dirs +N'
+
+`~+N'
+ The string that would be displayed by `dirs +N'
- The `$' character introduces parameter expansion, command
-substitution, or arithmetic expansion. The parameter name or symbol to
-be expanded may be enclosed in braces, which are optional but serve to
-protect the variable to be expanded from characters immediately
-following it which could be interpreted as part of the name.
+`~-N'
+ The string that would be displayed by `dirs -N'
+
+
+\1f
+File: bashref.info, Node: Shell Parameter Expansion, Next: Command Substitution, Prev: Tilde Expansion, Up: Shell Expansions
+
+3.5.3 Shell Parameter Expansion
+-------------------------------
+
+The `$' character introduces parameter expansion, command substitution,
+or arithmetic expansion. The parameter name or symbol to be expanded
+may be enclosed in braces, which are optional but serve to protect the
+variable to be expanded from characters immediately following it which
+could be interpreted as part of the name.
+
+ When braces are used, the matching ending brace is the first `}' not
+escaped by a backslash or within a quoted string, and not within an
+embedded arithmetic expansion, command substitution, or parameter
+expansion.
The basic form of parameter expansion is ${PARAMETER}. The value of
PARAMETER is substituted. The braces are required when PARAMETER is a
variable formed from the rest of PARAMETER as the name of the variable;
this variable is then expanded and that value is used in the rest of
the substitution, rather than the value of PARAMETER itself. This is
-known as `indirect expansion'.
+known as `indirect expansion'. The exceptions to this are the
+expansions of ${!PREFIX*} and ${!NAME[@]} described below. The
+exclamation point must immediately follow the left brace in order to
+introduce indirection.
In each of the cases below, WORD is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
-When not performing substring expansion, Bash tests for a parameter
+
+ When not performing substring expansion, Bash tests for a parameter
that is unset or null; omitting the colon results in a test only for a
-parameter that is unset.
+parameter that is unset. Put another way, if the colon is included,
+the operator tests for both existence and that the value is not null;
+if the colon is omitted, the operator tests only for existence.
`${PARAMETER:-WORD}'
If PARAMETER is unset or null, the expansion of WORD is
`${PARAMETER:=WORD}'
If PARAMETER is unset or null, the expansion of WORD is assigned
to PARAMETER. The value of PARAMETER is then substituted.
- Positional parameters and special parameters may not be assigned
- to in this way.
+ Positional parameters and special parameters may not be assigned to
+ in this way.
`${PARAMETER:?WORD}'
If PARAMETER is null or unset, the expansion of WORD (or a message
`${PARAMETER:OFFSET}'
`${PARAMETER:OFFSET:LENGTH}'
- Expands to up to LENGTH characters of PARAMETER, starting at
- OFFSET. If LENGTH is omitted, expands to the substring of
- PARAMETER, starting at the character specified by OFFSET. LENGTH
- and OFFSET are arithmetic expressions (*note Arithmetic
- Evaluation::.). This is referred to as Substring Expansion.
+ Expands to up to LENGTH characters of PARAMETER starting at the
+ character specified by OFFSET. If LENGTH is omitted, expands to
+ the substring of PARAMETER starting at the character specified by
+ OFFSET. LENGTH and OFFSET are arithmetic expressions (*note Shell
+ Arithmetic::). This is referred to as Substring Expansion.
LENGTH must evaluate to a number greater than or equal to zero.
If OFFSET evaluates to a number less than zero, the value is used
as an offset from the end of the value of PARAMETER. If PARAMETER
is `@', the result is LENGTH positional parameters beginning at
- OFFSET. If PARAMETER is an array name indexed by `@' or `*', the
- result is the LENGTH members of the array beginning with
- ${PARAMETER[OFFSET]}. Substring indexing is zero-based unless the
- positional parameters are used, in which case the indexing starts
- at 1.
+ OFFSET. If PARAMETER is an indexed array name subscripted by `@'
+ or `*', the result is the LENGTH members of the array beginning
+ with `${PARAMETER[OFFSET]}'. A negative OFFSET is taken relative
+ to one greater than the maximum index of the specified array.
+ Substring expansion applied to an associative array produces
+ undefined results.
+
+ Note that a negative offset must be separated from the colon by at
+ least one space to avoid being confused with the `:-' expansion.
+ Substring indexing is zero-based unless the positional parameters
+ are used, in which case the indexing starts at 1 by default. If
+ OFFSET is 0, and the positional parameters are used, `$@' is
+ prefixed to the list.
+
+`${!PREFIX*}'
+`${!PREFIX@}'
+ Expands to the names of variables whose names begin with PREFIX,
+ separated by the first character of the `IFS' special variable.
+ When `@' is used and the expansion appears within double quotes,
+ each variable name expands to a separate word.
+
+`${!NAME[@]}'
+`${!NAME[*]}'
+ If NAME is an array variable, expands to the list of array indices
+ (keys) assigned in NAME. If NAME is not an array, expands to 0 if
+ NAME is set and null otherwise. When `@' is used and the
+ expansion appears within double quotes, each key expands to a
+ separate word.
`${#PARAMETER}'
- The length in characters of the value of PARAMETER is substituted.
- If PARAMETER is `*' or `@', the length substituted is the number
- of positional parameters. If PARAMETER is an array name
- subscripted by `*' or `@', the length substituted is the number of
- elements in the array.
+ The length in characters of the expanded value of PARAMETER is
+ substituted. If PARAMETER is `*' or `@', the value substituted is
+ the number of positional parameters. If PARAMETER is an array
+ name subscripted by `*' or `@', the value substituted is the
+ number of elements in the array.
`${PARAMETER#WORD}'
`${PARAMETER##WORD}'
The WORD is expanded to produce a pattern just as in filename
- expansion (*note Filename Expansion::.). If the pattern matches
- the beginning of the value of PARAMETER, then the expansion is the
- value of PARAMETER with the shortest matching pattern (the `#'
- case) or the longest matching pattern (the `##' case) deleted. If
- PARAMETER is `@' or `*', the pattern removal operation is applied
- to each positional parameter in turn, and the expansion is the
- resultant list. If PARAMETER is an array variable subscripted with
- `@' or `*', the pattern removal operation is applied to each
- member of the array in turn, and the expansion is the resultant
- list.
+ expansion (*note Filename Expansion::). If the pattern matches
+ the beginning of the expanded value of PARAMETER, then the result
+ of the expansion is the expanded value of PARAMETER with the
+ shortest matching pattern (the `#' case) or the longest matching
+ pattern (the `##' case) deleted. If PARAMETER is `@' or `*', the
+ pattern removal operation is applied to each positional parameter
+ in turn, and the expansion is the resultant list. If PARAMETER is
+ an array variable subscripted with `@' or `*', the pattern removal
+ operation is applied to each member of the array in turn, and the
+ expansion is the resultant list.
`${PARAMETER%WORD}'
`${PARAMETER%%WORD}'
The WORD is expanded to produce a pattern just as in filename
- expansion. If the pattern matches a trailing portion of the value
- of PARAMETER, then the expansion is the value of PARAMETER with
- the shortest matching pattern (the `%' case) or the longest
- matching pattern (the `%%' case) deleted. If PARAMETER is `@' or
- `*', the pattern removal operation is applied to each positional
- parameter in turn, and the expansion is the resultant list. If
- PARAMETER is an array variable subscripted with `@' or `*', the
- pattern removal operation is applied to each member of the array
- in turn, and the expansion is the resultant list.
+ expansion. If the pattern matches a trailing portion of the
+ expanded value of PARAMETER, then the result of the expansion is
+ the value of PARAMETER with the shortest matching pattern (the `%'
+ case) or the longest matching pattern (the `%%' case) deleted. If
+ PARAMETER is `@' or `*', the pattern removal operation is applied
+ to each positional parameter in turn, and the expansion is the
+ resultant list. If PARAMETER is an array variable subscripted
+ with `@' or `*', the pattern removal operation is applied to each
+ member of the array in turn, and the expansion is the resultant
+ list.
`${PARAMETER/PATTERN/STRING}'
-`${PARAMETER//PATTERN/STRING}'
The PATTERN is expanded to produce a pattern just as in filename
expansion. PARAMETER is expanded and the longest match of PATTERN
- against its value is replaced with STRING. In the first form,
- only the first match is replaced. The second form causes all
- matches of PATTERN to be replaced with STRING. If PATTERN begins
- with `#', it must match at the beginning of STRING. If PATTERN
- begins with `%', it must match at the end of STRING. If STRING is
- null, matches of PATTERN are deleted and the `/' following PATTERN
- may be omitted. If PARAMETER is `@' or `*', the substitution
+ against its value is replaced with STRING. If PATTERN begins with
+ `/', all matches of PATTERN are replaced with STRING. Normally
+ only the first match is replaced. If PATTERN begins with `#', it
+ must match at the beginning of the expanded value of PARAMETER.
+ If PATTERN begins with `%', it must match at the end of the
+ expanded value of PARAMETER. If STRING is null, matches of
+ PATTERN are deleted and the `/' following PATTERN may be omitted.
+ If PARAMETER is `@' or `*', the substitution operation is applied
+ to each positional parameter in turn, and the expansion is the
+ resultant list. If PARAMETER is an array variable subscripted
+ with `@' or `*', the substitution operation is applied to each
+ member of the array in turn, and the expansion is the resultant
+ list.
+
+`${PARAMETER^PATTERN}'
+`${PARAMETER^^PATTERN}'
+`${PARAMETER,PATTERN}'
+`${PARAMETER,,PATTERN}'
+ This expansion modifies the case of alphabetic characters in
+ PARAMETER. The PATTERN is expanded to produce a pattern just as in
+ pathname expansion. The `^' operator converts lowercase letters
+ matching PATTERN to uppercase; the `,' operator converts matching
+ uppercase letters to lowercase. The `^^' and `,,' expansions
+ convert each matched character in the expanded value; the `^' and
+ `,' expansions match and convert only the first character. If
+ PATTERN is omitted, it is treated like a `?', which matches every
+ character. If PARAMETER is `@' or `*', the case modification
operation is applied to each positional parameter in turn, and the
expansion is the resultant list. If PARAMETER is an array
- variable subscripted with `@' or `*', the substitution operation
- is applied to each member of the array in turn, and the expansion
- is the resultant list.
+ variable subscripted with `@' or `*', the case modification
+ operation is applied to each member of the array in turn, and the
+ expansion is the resultant list.
+
\1f
-File: bashref.info, Node: Command Substitution, Next: Process Substitution, Prev: Shell Parameter Expansion, Up: Shell Expansions
+File: bashref.info, Node: Command Substitution, Next: Arithmetic Expansion, Prev: Shell Parameter Expansion, Up: Shell Expansions
-Command Substitution
---------------------
+3.5.4 Command Substitution
+--------------------------
- Command substitution allows the output of a command to replace the
-command name. There are two forms:
+Command substitution allows the output of a command to replace the
+command itself. Command substitution occurs when a command is enclosed
+as follows:
$(COMMAND)
-
-or
+ or
`COMMAND`
Bash performs the expansion by executing COMMAND and replacing the
command substitution with the standard output of the command, with any
-trailing newlines deleted.
+trailing newlines deleted. Embedded newlines are not deleted, but they
+may be removed during word splitting. The command substitution `$(cat
+FILE)' can be replaced by the equivalent but faster `$(< FILE)'.
When the old-style backquote form of substitution is used, backslash
retains its literal meaning except when followed by `$', ``', or `\'.
-When using the `$(COMMAND)' form, all characters between the
-parentheses make up the command; none are treated specially.
+The first backquote not preceded by a backslash terminates the command
+substitution. When using the `$(COMMAND)' form, all characters between
+the parentheses make up the command; none are treated specially.
- Command substitutions may be nested. To nest when using the old
-form, escape the inner backquotes with backslashes.
+ Command substitutions may be nested. To nest when using the
+backquoted form, escape the inner backquotes with backslashes.
If the substitution appears within double quotes, word splitting and
filename expansion are not performed on the results.
\1f
-File: bashref.info, Node: Process Substitution, Next: Word Splitting, Prev: Command Substitution, Up: Shell Expansions
+File: bashref.info, Node: Arithmetic Expansion, Next: Process Substitution, Prev: Command Substitution, Up: Shell Expansions
-Process Substitution
---------------------
+3.5.5 Arithmetic Expansion
+--------------------------
- Process substitution is supported on systems that support named
-pipes (FIFOs) or the `/dev/fd' method of naming open files. It takes
-the form of
- <(LIST)
+Arithmetic expansion allows the evaluation of an arithmetic expression
+and the substitution of the result. The format for arithmetic
+expansion is:
-or
- >(LIST)
+ $(( EXPRESSION ))
+
+ The expression is treated as if it were within double quotes, but a
+double quote inside the parentheses is not treated specially. All
+tokens in the expression undergo parameter expansion, command
+substitution, and quote removal. Arithmetic expansions may be nested.
-The process LIST is run with its input or output connected to a FIFO or
-some file in `/dev/fd'. The name of this file is passed as an argument
-to the current command as the result of the expansion. If the
+ The evaluation is performed according to the rules listed below
+(*note Shell Arithmetic::). If the expression is invalid, Bash prints
+a message indicating failure to the standard error and no substitution
+occurs.
+
+\1f
+File: bashref.info, Node: Process Substitution, Next: Word Splitting, Prev: Arithmetic Expansion, Up: Shell Expansions
+
+3.5.6 Process Substitution
+--------------------------
+
+Process substitution is supported on systems that support named pipes
+(FIFOs) or the `/dev/fd' method of naming open files. It takes the
+form of
+ <(LIST)
+ or
+ >(LIST)
+ The process LIST is run with its input or output connected to a FIFO
+or some file in `/dev/fd'. The name of this file is passed as an
+argument to the current command as the result of the expansion. If the
`>(LIST)' form is used, writing to the file will provide input for
LIST. If the `<(LIST)' form is used, the file passed as an argument
-should be read to obtain the output of LIST.
+should be read to obtain the output of LIST. Note that no space may
+appear between the `<' or `>' and the left parenthesis, otherwise the
+construct would be interpreted as a redirection.
- On systems that support it, process substitution is performed
-simultaneously with parameter and variable expansion, command
-substitution, and arithmetic expansion.
+ When available, process substitution is performed simultaneously with
+parameter and variable expansion, command substitution, and arithmetic
+expansion.
\1f
File: bashref.info, Node: Word Splitting, Next: Filename Expansion, Prev: Process Substitution, Up: Shell Expansions
-Word Splitting
---------------
+3.5.7 Word Splitting
+--------------------
- The shell scans the results of parameter expansion, command
+The shell scans the results of parameter expansion, command
substitution, and arithmetic expansion that did not occur within double
quotes for word splitting.
The shell treats each character of `$IFS' as a delimiter, and splits
the results of the other expansions into words on these characters. If
`IFS' is unset, or its value is exactly `<space><tab><newline>', the
-default, then any sequence of `IFS' characters serves to delimit words.
-If `IFS' has a value other than the default, then sequences of the
-whitespace characters `space' and `tab' are ignored at the beginning
-and end of the word, as long as the whitespace character is in the
-value of `IFS' (an `IFS' whitespace character). Any character in `IFS'
-that is not `IFS' whitespace, along with any adjacent `IFS' whitespace
-characters, delimits a field. A sequence of `IFS' whitespace
-characters is also treated as a delimiter. If the value of `IFS' is
-null, no word splitting occurs.
+default, then sequences of ` <space>', `<tab>', and `<newline>' at the
+beginning and end of the results of the previous expansions are
+ignored, and any sequence of `IFS' characters not at the beginning or
+end serves to delimit words. If `IFS' has a value other than the
+default, then sequences of the whitespace characters `space' and `tab'
+are ignored at the beginning and end of the word, as long as the
+whitespace character is in the value of `IFS' (an `IFS' whitespace
+character). Any character in `IFS' that is not `IFS' whitespace, along
+with any adjacent `IFS' whitespace characters, delimits a field. A
+sequence of `IFS' whitespace characters is also treated as a delimiter.
+If the value of `IFS' is null, no word splitting occurs.
Explicit null arguments (`""' or `''') are retained. Unquoted
-implicit null arguments, resulting from the expansion of PARAMETERs
+implicit null arguments, resulting from the expansion of parameters
that have no values, are removed. If a parameter with no value is
expanded within double quotes, a null argument results and is retained.
\1f
File: bashref.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
-Filename Expansion
-------------------
+3.5.8 Filename Expansion
+------------------------
+
+* Menu:
+
+* Pattern Matching:: How the shell matches patterns.
After word splitting, unless the `-f' option has been set (*note The
-Set Builtin::.), Bash scans each word for the characters `*', `?', and
+Set Builtin::), Bash scans each word for the characters `*', `?', and
`['. If one of these characters appears, then the word is regarded as
a PATTERN, and replaced with an alphabetically sorted list of file
names matching the pattern. If no matching file names are found, and
-the shell option `nullglob' is disabled, the word is left unchanged. If
-the option is set, and no matches are found, the word is removed. When
-a pattern is used for filename generation, the character `.' at the
-start of a filename or immediately following a slash must be matched
-explicitly, unless the shell option `dotglob' is set. The slash
-character must always be matched explicitly. In other cases, the `.'
-character is not treated specially. See the description of `shopt' in
-*Note Bash Builtins::, for a description of the `nullglob' and
-`dotglob' options.
+the shell option `nullglob' is disabled, the word is left unchanged.
+If the `nullglob' option is set, and no matches are found, the word is
+removed. If the `failglob' shell option is set, and no matches are
+found, an error message is printed and the command is not executed. If
+the shell option `nocaseglob' is enabled, the match is performed
+without regard to the case of alphabetic characters.
+
+ When a pattern is used for filename generation, the character `.' at
+the start of a filename or immediately following a slash must be
+matched explicitly, unless the shell option `dotglob' is set. When
+matching a file name, the slash character must always be matched
+explicitly. In other cases, the `.' character is not treated specially.
+
+ See the description of `shopt' in *note The Shopt Builtin::, for a
+description of the `nocaseglob', `nullglob', `failglob', and `dotglob'
+options.
The `GLOBIGNORE' shell variable may be used to restrict the set of
-filenames matching a PATTERN. If `GLOBIGNORE' is set, each matching
+filenames matching a pattern. If `GLOBIGNORE' is set, each matching
filename that also matches one of the patterns in `GLOBIGNORE' is
removed from the list of matches. The filenames `.' and `..' are
-always ignored, even when `GLOBIGNORE'. is set. However, setting
-`GLOBIGNORE' has the effect of enabling the `dotglob' shell option, so
-all other filenames beginning with a `.' will match. To get the old
-behavior of ignoring filenames beginning with a `.', make `.*' one of
-the patterns in `GLOBIGNORE'. The `dotglob' option is disabled when
-`GLOBIGNORE' is unset.
+always ignored when `GLOBIGNORE' is set and not null. However, setting
+`GLOBIGNORE' to a non-null value has the effect of enabling the
+`dotglob' shell option, so all other filenames beginning with a `.'
+will match. To get the old behavior of ignoring filenames beginning
+with a `.', make `.*' one of the patterns in `GLOBIGNORE'. The
+`dotglob' option is disabled when `GLOBIGNORE' is unset.
+
+\1f
+File: bashref.info, Node: Pattern Matching, Up: Filename Expansion
+
+3.5.8.1 Pattern Matching
+........................
+
+Any character that appears in a pattern, other than the special pattern
+characters described below, matches itself. The NUL character may not
+occur in a pattern. A backslash escapes the following character; the
+escaping backslash is discarded when matching. The special pattern
+characters must be quoted if they are to be matched literally.
The special pattern characters have the following meanings:
`*'
- Matches any string, including the null string.
+ Matches any string, including the null string. When the
+ `globstar' shell option is enabled, and `*' is used in a filename
+ expansion context, two adjacent `*'s used as a single pattern will
+ match all files and zero or more directories and subdirectories.
+ If followed by a `/', two adjacent `*'s will match only
+ directories and subdirectories.
`?'
Matches any single character.
`[...]'
Matches any one of the enclosed characters. A pair of characters
- separated by a minus sign denotes a RANGE; any character lexically
- between those two characters, inclusive, is matched. If the first
- character following the `[' is a `!' or a `^' then any character
- not enclosed is matched. A `-' may be matched by including it as
- the first or last character in the set. A `]' may be matched by
- including it as the first character in the set.
+ separated by a hyphen denotes a RANGE EXPRESSION; any character
+ that sorts between those two characters, inclusive, using the
+ current locale's collating sequence and character set, is matched.
+ If the first character following the `[' is a `!' or a `^' then
+ any character not enclosed is matched. A `-' may be matched by
+ including it as the first or last character in the set. A `]' may
+ be matched by including it as the first character in the set. The
+ sorting order of characters in range expressions is determined by
+ the current locale and the value of the `LC_COLLATE' shell
+ variable, if set.
+
+ For example, in the default C locale, `[a-dx-z]' is equivalent to
+ `[abcdxyz]'. Many locales sort characters in dictionary order,
+ and in these locales `[a-dx-z]' is typically not equivalent to
+ `[abcdxyz]'; it might be equivalent to `[aBbCcDdxXyYz]', for
+ example. To obtain the traditional interpretation of ranges in
+ bracket expressions, you can force the use of the C locale by
+ setting the `LC_COLLATE' or `LC_ALL' environment variable to the
+ value `C'.
+
+ Within `[' and `]', CHARACTER CLASSES can be specified using the
+ syntax `[:'CLASS`:]', where CLASS is one of the following classes
+ defined in the POSIX standard:
+ alnum alpha ascii blank cntrl digit graph lower
+ print punct space upper word xdigit
+ A character class matches any character belonging to that class.
+ The `word' character class matches letters, digits, and the
+ character `_'.
+
+ Within `[' and `]', an EQUIVALENCE CLASS can be specified using
+ the syntax `[='C`=]', which matches all characters with the same
+ collation weight (as defined by the current locale) as the
+ character C.
+
+ Within `[' and `]', the syntax `[.'SYMBOL`.]' matches the
+ collating symbol SYMBOL.
+
+ If the `extglob' shell option is enabled using the `shopt' builtin,
+several extended pattern matching operators are recognized. In the
+following description, a PATTERN-LIST is a list of one or more patterns
+separated by a `|'. Composite patterns may be formed using one or more
+of the following sub-patterns:
+
+`?(PATTERN-LIST)'
+ Matches zero or one occurrence of the given patterns.
+
+`*(PATTERN-LIST)'
+ Matches zero or more occurrences of the given patterns.
+
+`+(PATTERN-LIST)'
+ Matches one or more occurrences of the given patterns.
+
+`@(PATTERN-LIST)'
+ Matches one of the given patterns.
+
+`!(PATTERN-LIST)'
+ Matches anything except one of the given patterns.
\1f
File: bashref.info, Node: Quote Removal, Prev: Filename Expansion, Up: Shell Expansions
-Quote Removal
--------------
+3.5.9 Quote Removal
+-------------------
- After the preceding expansions, all unquoted occurrences of the
+After the preceding expansions, all unquoted occurrences of the
characters `\', `'', and `"' that did not result from one of the above
expansions are removed.
\1f
File: bashref.info, Node: Redirections, Next: Executing Commands, Prev: Shell Expansions, Up: Basic Shell Features
-Redirections
-============
+3.6 Redirections
+================
- Before a command is executed, its input and output may be REDIRECTED
+Before a command is executed, its input and output may be REDIRECTED
using a special notation interpreted by the shell. Redirection may
also be used to open and close files for the current shell execution
environment. The following redirection operators may precede or appear
the first character of the redirection operator is `>', the redirection
refers to the standard output (file descriptor 1).
- The word that follows the redirection operator in the following
-descriptions is subjected to brace expansion, tilde expansion,
-parameter expansion, command substitution, arithmetic expansion, quote
-removal, and filename expansion. If it expands to more than one word,
-Bash reports an error.
+ The word following the redirection operator in the following
+descriptions, unless otherwise noted, is subjected to brace expansion,
+tilde expansion, parameter expansion, command substitution, arithmetic
+expansion, quote removal, filename expansion, and word splitting. If
+it expands to more than one word, Bash reports an error.
Note that the order of redirections is significant. For example,
the command
ls > DIRLIST 2>&1
-
-directs both standard output and standard error to the file DIRLIST,
-while the command
+ directs both standard output (file descriptor 1) and standard error
+(file descriptor 2) to the file DIRLIST, while the command
ls 2>&1 > DIRLIST
+ directs only the standard output to file DIRLIST, because the
+standard error was duplicated as standard output before the standard
+output was redirected to DIRLIST.
-directs only the standard output to file DIRLIST, because the standard
-error was duplicated as standard output before the standard output was
-redirected to DIRLIST.
+ Bash handles several filenames specially when they are used in
+redirections, as described in the following table:
+
+`/dev/fd/FD'
+ If FD is a valid integer, file descriptor FD is duplicated.
+
+`/dev/stdin'
+ File descriptor 0 is duplicated.
+
+`/dev/stdout'
+ File descriptor 1 is duplicated.
+
+`/dev/stderr'
+ File descriptor 2 is duplicated.
+
+`/dev/tcp/HOST/PORT'
+ If HOST is a valid hostname or Internet address, and PORT is an
+ integer port number or service name, Bash attempts to open a TCP
+ connection to the corresponding socket.
+
+`/dev/udp/HOST/PORT'
+ If HOST is a valid hostname or Internet address, and PORT is an
+ integer port number or service name, Bash attempts to open a UDP
+ connection to the corresponding socket.
-Redirecting Input
------------------
- Redirection of input causes the file whose name results from the
+ A failure to open or create a file causes the redirection to fail.
+
+ Redirections using file descriptors greater than 9 should be used
+with care, as they may conflict with file descriptors the shell uses
+internally.
+
+3.6.1 Redirecting Input
+-----------------------
+
+Redirection of input causes the file whose name results from the
expansion of WORD to be opened for reading on file descriptor `n', or
the standard input (file descriptor 0) if `n' is not specified.
The general format for redirecting input is:
- [n]<WORD
+ [N]<WORD
-Redirecting Output
-------------------
+3.6.2 Redirecting Output
+------------------------
- Redirection of output causes the file whose name results from the
-expansion of WORD to be opened for writing on file descriptor `n', or
-the standard output (file descriptor 1) if `n' is not specified. If
-the file does not exist it is created; if it does exist it is truncated
-to zero size.
+Redirection of output causes the file whose name results from the
+expansion of WORD to be opened for writing on file descriptor N, or the
+standard output (file descriptor 1) if N is not specified. If the file
+does not exist it is created; if it does exist it is truncated to zero
+size.
The general format for redirecting output is:
- [n]>[|]WORD
+ [N]>[|]WORD
- If the redirection operator is `>', and the `-C' option to the `set'
-builtin has been enabled, the redirection will fail if the filename
-whose name results from the expansion of WORD exists. If the
-redirection operator is `>|', then the value of the `-C' option to the
-`set' builtin command is not tested, and the redirection is attempted
-even if the file named by WORD exists.
+ If the redirection operator is `>', and the `noclobber' option to
+the `set' builtin has been enabled, the redirection will fail if the
+file whose name results from the expansion of WORD exists and is a
+regular file. If the redirection operator is `>|', or the redirection
+operator is `>' and the `noclobber' option is not enabled, the
+redirection is attempted even if the file named by WORD exists.
-Appending Redirected Output
----------------------------
+3.6.3 Appending Redirected Output
+---------------------------------
- Redirection of output in this fashion causes the file whose name
+Redirection of output in this fashion causes the file whose name
results from the expansion of WORD to be opened for appending on file
-descriptor `n', or the standard output (file descriptor 1) if `n' is
-not specified. If the file does not exist it is created.
+descriptor N, or the standard output (file descriptor 1) if N is not
+specified. If the file does not exist it is created.
The general format for appending output is:
- [n]>>WORD
+ [N]>>WORD
-Redirecting Standard Output and Standard Error
-----------------------------------------------
+3.6.4 Redirecting Standard Output and Standard Error
+----------------------------------------------------
- Bash allows both the standard output (file descriptor 1) and the
-standard error output (file descriptor 2) to be redirected to the file
-whose name is the expansion of WORD with this construct.
+This construct allows both the standard output (file descriptor 1) and
+the standard error output (file descriptor 2) to be redirected to the
+file whose name is the expansion of WORD.
There are two formats for redirecting standard output and standard
error:
&>WORD
-
-and
+ and
>&WORD
-
-Of the two forms, the first is preferred. This is semantically
+ Of the two forms, the first is preferred. This is semantically
equivalent to
>WORD 2>&1
-Here Documents
---------------
+3.6.5 Appending Standard Output and Standard Error
+--------------------------------------------------
+
+This construct allows both the standard output (file descriptor 1) and
+the standard error output (file descriptor 2) to be appended to the
+file whose name is the expansion of WORD.
+
+ The format for appending standard output and standard error is:
+ &>>WORD
+ This is semantically equivalent to
+ >>WORD 2>&1
+
+3.6.6 Here Documents
+--------------------
- This type of redirection instructs the shell to read input from the
+This type of redirection instructs the shell to read input from the
current source until a line containing only WORD (with no trailing
blanks) is seen. All of the lines read up to that point are then used
as the standard input for a command.
- The format of here-documents is as follows:
+ The format of here-documents is:
<<[-]WORD
HERE-DOCUMENT
DELIMITER
- No parameter expansion, command substitution, filename expansion, or
-arithmetic expansion is performed on WORD. If any characters in WORD
+ No parameter expansion, command substitution, arithmetic expansion,
+or filename expansion is performed on WORD. If any characters in WORD
are quoted, the DELIMITER is the result of quote removal on WORD, and
-the lines in the here-document are not expanded. Otherwise, all lines
-of the here-document are subjected to parameter expansion, command
-substitution, and arithmetic expansion. In the latter case, the pair
-`\newline' is ignored, and `\' must be used to quote the characters
-`\', `$', and ``'.
+the lines in the here-document are not expanded. If WORD is unquoted,
+all lines of the here-document are subjected to parameter expansion,
+command substitution, and arithmetic expansion. In the latter case,
+the character sequence `\newline' is ignored, and `\' must be used to
+quote the characters `\', `$', and ``'.
If the redirection operator is `<<-', then all leading tab
characters are stripped from input lines and the line containing
DELIMITER. This allows here-documents within shell scripts to be
indented in a natural fashion.
-Duplicating File Descriptors
-----------------------------
+3.6.7 Here Strings
+------------------
+
+A variant of here documents, the format is:
+ <<< WORD
+
+ The WORD is expanded and supplied to the command on its standard
+input.
- The redirection operator
- [n]<&WORD
+3.6.8 Duplicating File Descriptors
+----------------------------------
-is used to duplicate input file descriptors. If WORD expands to one or
-more digits, the file descriptor denoted by `n' is made to be a copy of
-that file descriptor. If WORD evaluates to `-', file descriptor `n' is
-closed. If `n' is not specified, the standard input (file descriptor
-0) is used.
+The redirection operator
+ [N]<&WORD
+ is used to duplicate input file descriptors. If WORD expands to one
+or more digits, the file descriptor denoted by N is made to be a copy
+of that file descriptor. If the digits in WORD do not specify a file
+descriptor open for input, a redirection error occurs. If WORD
+evaluates to `-', file descriptor N is closed. If N is not specified,
+the standard input (file descriptor 0) is used.
The operator
- [n]>&WORD
+ [N]>&WORD
+ is used similarly to duplicate output file descriptors. If N is not
+specified, the standard output (file descriptor 1) is used. If the
+digits in WORD do not specify a file descriptor open for output, a
+redirection error occurs. As a special case, if N is omitted, and WORD
+does not expand to one or more digits, the standard output and standard
+error are redirected as described previously.
+
+3.6.9 Moving File Descriptors
+-----------------------------
-is used similarly to duplicate output file descriptors. If `n' is not
-specified, the standard output (file descriptor 1) is used. As a
-special case, if `n' is omitted, and WORD does not expand to one or
-more digits, the standard output and standard error are redirected as
-described previously.
+The redirection operator
+ [N]<&DIGIT-
+ moves the file descriptor DIGIT to file descriptor N, or the
+standard input (file descriptor 0) if N is not specified. DIGIT is
+closed after being duplicated to N.
-Opening File Descriptors for Reading and Writing
-------------------------------------------------
+ Similarly, the redirection operator
+ [N]>&DIGIT-
+ moves the file descriptor DIGIT to file descriptor N, or the
+standard output (file descriptor 1) if N is not specified.
- The redirection operator
- [n]<>WORD
+3.6.10 Opening File Descriptors for Reading and Writing
+-------------------------------------------------------
-causes the file whose name is the expansion of WORD to be opened for
-both reading and writing on file descriptor `n', or on file descriptor
-0 if `n' is not specified. If the file does not exist, it is created.
+The redirection operator
+ [N]<>WORD
+ causes the file whose name is the expansion of WORD to be opened for
+both reading and writing on file descriptor N, or on file descriptor 0
+if N is not specified. If the file does not exist, it is created.
\1f
File: bashref.info, Node: Executing Commands, Next: Shell Scripts, Prev: Redirections, Up: Basic Shell Features
-Executing Commands
-==================
+3.7 Executing Commands
+======================
* Menu:
+* Simple Command Expansion:: How Bash expands simple commands before
+ executing them.
* Command Search and Execution:: How Bash finds commands and runs them.
-
+* Command Execution Environment:: The environment in which Bash
+ executes commands that are not
+ shell builtins.
* Environment:: The environment given to a command.
-
* Exit Status:: The status returned by commands and how Bash
interprets it.
-
* Signals:: What happens when Bash or a command it runs
receives a signal.
\1f
-File: bashref.info, Node: Command Search and Execution, Next: Environment, Up: Executing Commands
+File: bashref.info, Node: Simple Command Expansion, Next: Command Search and Execution, Up: Executing Commands
-Command Search and Execution
-----------------------------
+3.7.1 Simple Command Expansion
+------------------------------
- After a command has been split into words, if it results in a simple
-command and an optional list of arguments, the following actions are
-taken.
+When a simple command is executed, the shell performs the following
+expansions, assignments, and redirections, from left to right.
+
+ 1. The words that the parser has marked as variable assignments (those
+ preceding the command name) and redirections are saved for later
+ processing.
+
+ 2. The words that are not variable assignments or redirections are
+ expanded (*note Shell Expansions::). If any words remain after
+ expansion, the first word is taken to be the name of the command
+ and the remaining words are the arguments.
+
+ 3. Redirections are performed as described above (*note
+ Redirections::).
+
+ 4. The text after the `=' in each variable assignment undergoes tilde
+ expansion, parameter expansion, command substitution, arithmetic
+ expansion, and quote removal before being assigned to the variable.
+
+ If no command name results, the variable assignments affect the
+current shell environment. Otherwise, the variables are added to the
+environment of the executed command and do not affect the current shell
+environment. If any of the assignments attempts to assign a value to a
+readonly variable, an error occurs, and the command exits with a
+non-zero status.
+
+ If no command name results, redirections are performed, but do not
+affect the current shell environment. A redirection error causes the
+command to exit with a non-zero status.
+
+ If there is a command name left after expansion, execution proceeds
+as described below. Otherwise, the command exits. If one of the
+expansions contained a command substitution, the exit status of the
+command is the exit status of the last command substitution performed.
+If there were no command substitutions, the command exits with a status
+of zero.
+
+\1f
+File: bashref.info, Node: Command Search and Execution, Next: Command Execution Environment, Prev: Simple Command Expansion, Up: Executing Commands
+
+3.7.2 Command Search and Execution
+----------------------------------
+
+After a command has been split into words, if it results in a simple
+command and an optional list of arguments, the following actions are
+taken.
1. If the command name contains no slashes, the shell attempts to
locate it. If there exists a shell function by that name, that
- function is invoked as described above in *Note Shell Functions::.
+ function is invoked as described in *note Shell Functions::.
2. If the name does not match a function, the shell searches for it
in the list of shell builtins. If a match is found, that builtin
3. If the name is neither a shell function nor a builtin, and
contains no slashes, Bash searches each element of `$PATH' for a
directory containing an executable file by that name. Bash uses a
- hash table to remember the full filenames of executable files (see
- the description of `hash' in *Note Bourne Shell Builtins::) to
- avoid multiple `PATH' searches. A full search of the directories
+ hash table to remember the full pathnames of executable files to
+ avoid multiple `PATH' searches (see the description of `hash' in
+ *note Bourne Shell Builtins::). A full search of the directories
in `$PATH' is performed only if the command is not found in the
- hash table. If the search is unsuccessful, the shell prints an
- error message and returns a nonzero exit status.
+ hash table. If the search is unsuccessful, the shell searches for
+ a defined shell function named `command_not_found_handle'. If
+ that function exists, it is invoked with the original command and
+ the original command's arguments as its arguments, and the
+ function's exit status becomes the exit status of the shell. If
+ that function is not defined, the shell prints an error message
+ and returns an exit status of 127.
4. If the search is successful, or if the command name contains one
- or more slashes, the shell executes the named program. Argument 0
- is set to the name given, and the remaining arguments to the
- command are set to the arguments supplied, if any.
+ or more slashes, the shell executes the named program in a
+ separate execution environment. Argument 0 is set to the name
+ given, and the remaining arguments to the command are set to the
+ arguments supplied, if any.
5. If this execution fails because the file is not in executable
- format, and the file is not a directory, it is assumed to be SHELL
- SCRIPT (*note Shell Scripts::.).
+ format, and the file is not a directory, it is assumed to be a
+ SHELL SCRIPT and the shell executes it as described in *note Shell
+ Scripts::.
+
+ 6. If the command was not begun asynchronously, the shell waits for
+ the command to complete and collects its exit status.
+
+
+\1f
+File: bashref.info, Node: Command Execution Environment, Next: Environment, Prev: Command Search and Execution, Up: Executing Commands
+
+3.7.3 Command Execution Environment
+-----------------------------------
+
+The shell has an EXECUTION ENVIRONMENT, which consists of the following:
+
+ * open files inherited by the shell at invocation, as modified by
+ redirections supplied to the `exec' builtin
+
+ * the current working directory as set by `cd', `pushd', or `popd',
+ or inherited by the shell at invocation
+
+ * the file creation mode mask as set by `umask' or inherited from
+ the shell's parent
+
+ * current traps set by `trap'
+
+ * shell parameters that are set by variable assignment or with `set'
+ or inherited from the shell's parent in the environment
+
+ * shell functions defined during execution or inherited from the
+ shell's parent in the environment
+
+ * options enabled at invocation (either by default or with
+ command-line arguments) or by `set'
+
+ * options enabled by `shopt' (*note The Shopt Builtin::)
+
+ * shell aliases defined with `alias' (*note Aliases::)
+
+ * various process IDs, including those of background jobs (*note
+ Lists::), the value of `$$', and the value of `$PPID'
+
+
+ When a simple command other than a builtin or shell function is to
+be executed, it is invoked in a separate execution environment that
+consists of the following. Unless otherwise noted, the values are
+inherited from the shell.
+
+ * the shell's open files, plus any modifications and additions
+ specified by redirections to the command
+
+ * the current working directory
+
+ * the file creation mode mask
+
+ * shell variables and functions marked for export, along with
+ variables exported for the command, passed in the environment
+ (*note Environment::)
+
+ * traps caught by the shell are reset to the values inherited from
+ the shell's parent, and traps ignored by the shell are ignored
+
+
+ A command invoked in this separate environment cannot affect the
+shell's execution environment.
+
+ Command substitution, commands grouped with parentheses, and
+asynchronous commands are invoked in a subshell environment that is a
+duplicate of the shell environment, except that traps caught by the
+shell are reset to the values that the shell inherited from its parent
+at invocation. Builtin commands that are invoked as part of a pipeline
+are also executed in a subshell environment. Changes made to the
+subshell environment cannot affect the shell's execution environment.
+
+ If a command is followed by a `&' and job control is not active, the
+default standard input for the command is the empty file `/dev/null'.
+Otherwise, the invoked command inherits the file descriptors of the
+calling shell as modified by redirections.
\1f
-File: bashref.info, Node: Environment, Next: Exit Status, Prev: Command Search and Execution, Up: Executing Commands
+File: bashref.info, Node: Environment, Next: Exit Status, Prev: Command Execution Environment, Up: Executing Commands
-Environment
------------
+3.7.4 Environment
+-----------------
- When a program is invoked it is given an array of strings called the
+When a program is invoked it is given an array of strings called the
ENVIRONMENT. This is a list of name-value pairs, of the form
`name=value'.
- Bash allows you to manipulate the environment in several ways. On
+ Bash provides several ways to manipulate the environment. On
invocation, the shell scans its own environment and creates a parameter
for each name found, automatically marking it for EXPORT to child
processes. Executed commands inherit the environment. The `export'
environment is modified, the new value becomes part of the environment,
replacing the old. The environment inherited by any executed command
consists of the shell's initial environment, whose values may be
-modified in the shell, less any pairs removed by the `unset' command,
-plus any additions via the `export' and `declare -x' commands.
+modified in the shell, less any pairs removed by the `unset' and
+`export -n' commands, plus any additions via the `export' and `declare
+-x' commands.
The environment for any simple command or function may be augmented
temporarily by prefixing it with parameter assignments, as described in
-*Note Shell Parameters::. These assignment statements affect only the
+*note Shell Parameters::. These assignment statements affect only the
environment seen by that command.
- If the `-k' flag is set (*note The Set Builtin::., then all
+ If the `-k' option is set (*note The Set Builtin::), then all
parameter assignments are placed in the environment for a command, not
just those that precede the command name.
\1f
File: bashref.info, Node: Exit Status, Next: Signals, Prev: Environment, Up: Executing Commands
-Exit Status
------------
+3.7.5 Exit Status
+-----------------
+
+The exit status of an executed command is the value returned by the
+WAITPID system call or equivalent function. Exit statuses fall between
+0 and 255, though, as explained below, the shell may use values above
+125 specially. Exit statuses from shell builtins and compound commands
+are also limited to this range. Under certain circumstances, the shell
+will use special values to indicate specific failure modes.
- For the purposes of the shell, a command which exits with a zero
-exit status has succeeded. A non-zero exit status indicates failure.
-This seemingly counter-intuitive scheme is used so there is one
-well-defined way to indicate success and a variety of ways to indicate
-various failure modes. When a command terminates on a fatal signal
-whose number is N, Bash uses the value 128+N as the exit status.
+ For the shell's purposes, a command which exits with a zero exit
+status has succeeded. A non-zero exit status indicates failure. This
+seemingly counter-intuitive scheme is used so there is one well-defined
+way to indicate success and a variety of ways to indicate various
+failure modes. When a command terminates on a fatal signal whose
+number is N, Bash uses the value 128+N as the exit status.
If a command is not found, the child process created to execute it
returns a status of 127. If a command is found but is not executable,
the return status is 126.
+ If a command fails because of an error during expansion or
+redirection, the exit status is greater than zero.
+
The exit status is used by the Bash conditional commands (*note
-Conditional Constructs::.) and some of the list constructs (*note
-Lists::.).
+Conditional Constructs::) and some of the list constructs (*note
+Lists::).
All of the Bash builtins return an exit status of zero if they
succeed and a non-zero status on failure, so they may be used by the
-conditional and list constructs.
+conditional and list constructs. All builtins return an exit status of
+2 to indicate incorrect usage.
\1f
File: bashref.info, Node: Signals, Prev: Exit Status, Up: Executing Commands
-Signals
--------
-
- When Bash is interactive, it ignores `SIGTERM' (so that `kill 0'
-does not kill an interactive shell), and `SIGINT' is caught and handled
-(so that the `wait' builtin is interruptible). When Bash receives a
-`SIGINT', it breaks out of any executing loops. In all cases, Bash
-ignores `SIGQUIT'. If job control is in effect (*note Job Control::.),
-Bash ignores `SIGTTIN', `SIGTTOU', and `SIGTSTP'.
+3.7.6 Signals
+-------------
- Synchronous jobs started by Bash have signals set to the values
-inherited by the shell from its parent. When job control is not in
-effect, background jobs (commands terminated with `&') ignore `SIGINT'
-and `SIGQUIT'. Commands run as a result of command substitution ignore
-the keyboard-generated job control signals `SIGTTIN', `SIGTTOU', and
-`SIGTSTP'.
+When Bash is interactive, in the absence of any traps, it ignores
+`SIGTERM' (so that `kill 0' does not kill an interactive shell), and
+`SIGINT' is caught and handled (so that the `wait' builtin is
+interruptible). When Bash receives a `SIGINT', it breaks out of any
+executing loops. In all cases, Bash ignores `SIGQUIT'. If job control
+is in effect (*note Job Control::), Bash ignores `SIGTTIN', `SIGTTOU',
+and `SIGTSTP'.
+
+ Non-builtin commands started by Bash have signal handlers set to the
+values inherited by the shell from its parent. When job control is not
+in effect, asynchronous commands ignore `SIGINT' and `SIGQUIT' in
+addition to these inherited handlers. Commands run as a result of
+command substitution ignore the keyboard-generated job control signals
+`SIGTTIN', `SIGTTOU', and `SIGTSTP'.
The shell exits by default upon receipt of a `SIGHUP'. Before
-exiting, it resends the `SIGHUP' to all jobs, running or stopped. To
-prevent the shell from sending the `SIGHUP' signal to a particular job,
-remove it from the jobs table with the `disown' builtin (*note Job
-Control Builtins::.) or use `disown -h' to mark it to not receive
-`SIGHUP'.
+exiting, an interactive shell resends the `SIGHUP' to all jobs, running
+or stopped. Stopped jobs are sent `SIGCONT' to ensure that they receive
+the `SIGHUP'. To prevent the shell from sending the `SIGHUP' signal to
+a particular job, it should be removed from the jobs table with the
+`disown' builtin (*note Job Control Builtins::) or marked to not
+receive `SIGHUP' using `disown -h'.
+
+ If the `huponexit' shell option has been set with `shopt' (*note
+The Shopt Builtin::), Bash sends a `SIGHUP' to all jobs when an
+interactive login shell exits.
+
+ If Bash is waiting for a command to complete and receives a signal
+for which a trap has been set, the trap will not be executed until the
+command completes. When Bash is waiting for an asynchronous command
+via the `wait' builtin, the reception of a signal for which a trap has
+been set will cause the `wait' builtin to return immediately with an
+exit status greater than 128, immediately after which the trap is
+executed.
\1f
File: bashref.info, Node: Shell Scripts, Prev: Executing Commands, Up: Basic Shell Features
-Shell Scripts
-=============
+3.8 Shell Scripts
+=================
- A shell script is a text file containing shell commands. When such
-a file is used as the first non-option argument when invoking Bash, and
-neither the `-c' nor `-s' option is supplied (*note Invoking Bash::.),
+A shell script is a text file containing shell commands. When such a
+file is used as the first non-option argument when invoking Bash, and
+neither the `-c' nor `-s' option is supplied (*note Invoking Bash::),
Bash reads and executes commands from the file, then exits. This mode
-of operation creates a non-interactive shell. When Bash runs a shell
-script, it sets the special parameter `0' to the name of the file,
-rather than the name of the shell, and the positional parameters are
-set to the remaining arguments, if any are given. If no additional
-arguments are supplied, the positional parameters are unset.
+of operation creates a non-interactive shell. The shell first searches
+for the file in the current directory, and looks in the directories in
+`$PATH' if not found there.
+
+ When Bash runs a shell script, it sets the special parameter `0' to
+the name of the file, rather than the name of the shell, and the
+positional parameters are set to the remaining arguments, if any are
+given. If no additional arguments are supplied, the positional
+parameters are unset.
A shell script may be made executable by using the `chmod' command
to turn on the execute bit. When Bash finds such a file while
searching the `$PATH' for a command, it spawns a subshell to execute
it. In other words, executing
filename ARGUMENTS
-
-is equivalent to executing
+ is equivalent to executing
bash filename ARGUMENTS
if `filename' is an executable shell script. This subshell
reinitializes itself, so that the effect is as if a new shell had been
-invoked to interpret the script.
-
- Most versions of Unix make this a part of the kernel's command
-execution mechanism. If the first line of a script begins with the two
-characters `#!', the remainder of the line specifies an interpreter for
-the program. The arguments to the interpreter consist of a single
-optional argument following the interpreter name on the first line of
-the script file, followed by the name of the script file, followed by
-the rest of the arguments. Bash will perform this action on operating
-systems that do not handle it themselves. Note that some older
-versions of Unix limit the interpreter name and argument to a maximum
-of 32 characters.
+invoked to interpret the script, with the exception that the locations
+of commands remembered by the parent (see the description of `hash' in
+*note Bourne Shell Builtins::) are retained by the child.
+
+ Most versions of Unix make this a part of the operating system's
+command execution mechanism. If the first line of a script begins with
+the two characters `#!', the remainder of the line specifies an
+interpreter for the program. Thus, you can specify Bash, `awk', Perl,
+or some other interpreter and write the rest of the script file in that
+language.
+
+ The arguments to the interpreter consist of a single optional
+argument following the interpreter name on the first line of the script
+file, followed by the name of the script file, followed by the rest of
+the arguments. Bash will perform this action on operating systems that
+do not handle it themselves. Note that some older versions of Unix
+limit the interpreter name and argument to a maximum of 32 characters.
+
+ Bash scripts often begin with `#! /bin/bash' (assuming that Bash has
+been installed in `/bin'), since this ensures that Bash will be used to
+interpret the script, even if it is executed under another shell.
\1f
-File: bashref.info, Node: Bourne Shell Features, Next: Csh Features, Prev: Basic Shell Features, Up: Top
+File: bashref.info, Node: Shell Builtin Commands, Next: Shell Variables, Prev: Basic Shell Features, Up: Top
-Bourne Shell Style Features
-***************************
+4 Shell Builtin Commands
+************************
* Menu:
* Bourne Shell Builtins:: Builtin commands inherited from the Bourne
Shell.
-* Bourne Shell Variables:: Variables which Bash uses in the same way
- as the Bourne Shell.
-* Other Bourne Shell Features:: Addtional aspects of Bash which behave in
- the same way as the Bourne Shell.
-
- This section briefly summarizes things which Bash inherits from the
-Bourne Shell: builtins, variables, and other features. It also lists
-the significant differences between Bash and the Bourne Shell.
+* Bash Builtins:: Table of builtins specific to Bash.
+* Modifying Shell Behavior:: Builtins to modify shell attributes and
+ optional behavior.
+* Special Builtins:: Builtin commands classified specially by
+ POSIX.
+
+ Builtin commands are contained within the shell itself. When the
+name of a builtin command is used as the first word of a simple command
+(*note Simple Commands::), the shell executes the command directly,
+without invoking another program. Builtin commands are necessary to
+implement functionality impossible or inconvenient to obtain with
+separate utilities.
+
+ This section briefly describes the builtins which Bash inherits from
+the Bourne Shell, as well as the builtin commands which are unique to
+or have been extended in Bash.
+
+ Several builtin commands are described in other chapters: builtin
+commands which provide the Bash interface to the job control facilities
+(*note Job Control Builtins::), the directory stack (*note Directory
+Stack Builtins::), the command history (*note Bash History Builtins::),
+and the programmable completion facilities (*note Programmable
+Completion Builtins::).
+
+ Many of the builtins have been extended by POSIX or Bash.
+
+ Unless otherwise noted, each builtin command documented as accepting
+options preceded by `-' accepts `--' to signify the end of the options.
+For example, the `:', `true', `false', and `test' builtins do not
+accept options.
\1f
-File: bashref.info, Node: Bourne Shell Builtins, Next: Bourne Shell Variables, Up: Bourne Shell Features
+File: bashref.info, Node: Bourne Shell Builtins, Next: Bash Builtins, Up: Shell Builtin Commands
-Bourne Shell Builtins
-=====================
+4.1 Bourne Shell Builtins
+=========================
- The following shell builtin commands are inherited from the Bourne
-Shell. These commands are implemented as specified by the POSIX 1003.2
+The following shell builtin commands are inherited from the Bourne
+Shell. These commands are implemented as specified by the POSIX
standard.
-`:'
+`: (a colon)'
: [ARGUMENTS]
Do nothing beyond expanding ARGUMENTS and performing redirections.
+ The return status is zero.
-`.'
- . FILENAME
+`. (a period)'
+ . FILENAME [ARGUMENTS]
Read and execute commands from the FILENAME argument in the
- current shell context.
+ current shell context. If FILENAME does not contain a slash, the
+ `PATH' variable is used to find FILENAME. When Bash is not in
+ POSIX mode, the current directory is searched if FILENAME is not
+ found in `$PATH'. If any ARGUMENTS are supplied, they become the
+ positional parameters when FILENAME is executed. Otherwise the
+ positional parameters are unchanged. The return status is the
+ exit status of the last command executed, or zero if no commands
+ are executed. If FILENAME is not found, or cannot be read, the
+ return status is non-zero. This builtin is equivalent to `source'.
`break'
break [N]
Exit from a `for', `while', `until', or `select' loop. If N is
- supplied, the Nth enclosing loop is exited.
+ supplied, the Nth enclosing loop is exited. N must be greater
+ than or equal to 1. The return status is zero unless N is not
+ greater than or equal to 1.
`cd'
- cd [-LP] [DIRECTORY]
+ cd [-L|-P] [DIRECTORY]
Change the current working directory to DIRECTORY. If DIRECTORY
is not given, the value of the `HOME' shell variable is used. If
the shell variable `CDPATH' exists, it is used as a search path.
- If DIRECTORY begins with a slash, `CDPATH' is not used. The `-P'
- option means to not follow symbolic links; symlinks are followed
- by default or with the `-L' option.
+ If DIRECTORY begins with a slash, `CDPATH' is not used.
+
+ The `-P' option means to not follow symbolic links; symbolic links
+ are followed by default or with the `-L' option. If DIRECTORY is
+ `-', it is equivalent to `$OLDPWD'.
+
+ If a non-empty directory name from `CDPATH' is used, or if `-' is
+ the first argument, and the directory change is successful, the
+ absolute pathname of the new working directory is written to the
+ standard output.
+
+ The return status is zero if the directory is successfully changed,
+ non-zero otherwise.
`continue'
continue [N]
Resume the next iteration of an enclosing `for', `while', `until',
or `select' loop. If N is supplied, the execution of the Nth
- enclosing loop is resumed.
+ enclosing loop is resumed. N must be greater than or equal to 1.
+ The return status is zero unless N is not greater than or equal to
+ 1.
`eval'
eval [ARGUMENTS]
The arguments are concatenated together into a single command,
- which is then read and executed.
+ which is then read and executed, and its exit status returned as
+ the exit status of `eval'. If there are no arguments or only
+ empty arguments, the return status is zero.
`exec'
- exec [-cl] [-a NAME] [COMMAND] [ARGUMENTS]
- If COMMAND is supplied, it replaces the shell. If the `-l' option
- is supplied, the shell places a dash in the zeroth arg passed to
- COMMAND. This is what the `login' program does. The `-c' option
- causes COMMAND to be executed with an empty environment. If `-a'
- is supplied, the shell passes NAME as the zeroth argument to
- COMMAND. If no COMMAND is specified, redirections may be used to
- affect the current shell environment.
+ exec [-cl] [-a NAME] [COMMAND [ARGUMENTS]]
+ If COMMAND is supplied, it replaces the shell without creating a
+ new process. If the `-l' option is supplied, the shell places a
+ dash at the beginning of the zeroth argument passed to COMMAND.
+ This is what the `login' program does. The `-c' option causes
+ COMMAND to be executed with an empty environment. If `-a' is
+ supplied, the shell passes NAME as the zeroth argument to COMMAND.
+ If no COMMAND is specified, redirections may be used to affect the
+ current shell environment. If there are no redirection errors, the
+ return status is zero; otherwise the return status is non-zero.
`exit'
exit [N]
- Exit the shell, returning a status of N to the shell's parent.
+ Exit the shell, returning a status of N to the shell's parent. If
+ N is omitted, the exit status is that of the last command executed.
+ Any trap on `EXIT' is executed before the shell terminates.
`export'
export [-fn] [-p] [NAME[=VALUE]]
Mark each NAME to be passed to child processes in the environment.
If the `-f' option is supplied, the NAMEs refer to shell
- functions. The `-n' option means to no longer mark each NAME for
- export. If no NAMES are supplied, or if the `-p' option is given,
- a list of exported names is displayed.
+ functions; otherwise the names refer to shell variables. The `-n'
+ option means to no longer mark each NAME for export. If no NAMES
+ are supplied, or if the `-p' option is given, a list of exported
+ names is displayed. The `-p' option displays output in a form
+ that may be reused as input. If a variable name is followed by
+ =VALUE, the value of the variable is set to VALUE.
+
+ The return status is zero unless an invalid option is supplied,
+ one of the names is not a valid shell variable name, or `-f' is
+ supplied with a name that is not a shell function.
`getopts'
getopts OPTSTRING NAME [ARGS]
`getopts' is used by shell scripts to parse positional parameters.
- OPTSTRING contains the option letters to be recognized; if a letter
- is followed by a colon, the option is expected to have an
- argument, which should be separated from it by white space. Each
- time it is invoked, `getopts' places the next option in the shell
- variable NAME, initializing NAME if it does not exist, and the
- index of the next argument to be processed into the variable
- `OPTIND'. `OPTIND' is initialized to 1 each time the shell or a
- shell script is invoked. When an option requires an argument,
- `getopts' places that argument into the variable `OPTARG'. The
- shell does not reset `OPTIND' automatically; it must be manually
- reset between multiple calls to `getopts' within the same shell
- invocation if a new set of parameters is to be used.
+ OPTSTRING contains the option characters to be recognized; if a
+ character is followed by a colon, the option is expected to have an
+ argument, which should be separated from it by white space. The
+ colon (`:') and question mark (`?') may not be used as option
+ characters. Each time it is invoked, `getopts' places the next
+ option in the shell variable NAME, initializing NAME if it does
+ not exist, and the index of the next argument to be processed into
+ the variable `OPTIND'. `OPTIND' is initialized to 1 each time the
+ shell or a shell script is invoked. When an option requires an
+ argument, `getopts' places that argument into the variable
+ `OPTARG'. The shell does not reset `OPTIND' automatically; it
+ must be manually reset between multiple calls to `getopts' within
+ the same shell invocation if a new set of parameters is to be used.
+
+ When the end of options is encountered, `getopts' exits with a
+ return value greater than zero. `OPTIND' is set to the index of
+ the first non-option argument, and `name' is set to `?'.
+
+ `getopts' normally parses the positional parameters, but if more
+ arguments are given in ARGS, `getopts' parses those instead.
`getopts' can report errors in two ways. If the first character of
OPTSTRING is a colon, SILENT error reporting is used. In normal
- operation diagnostic messages are printed when illegal options or
+ operation diagnostic messages are printed when invalid options or
missing option arguments are encountered. If the variable `OPTERR'
- is set to 0, no error message will be displayed, even if the first
+ is set to 0, no error messages will be displayed, even if the first
character of `optstring' is not a colon.
- If an illegal option is seen, `getopts' places `?' into NAME and,
+ If an invalid option is seen, `getopts' places `?' into NAME and,
if not silent, prints an error message and unsets `OPTARG'. If
`getopts' is silent, the option character found is placed in
`OPTARG' and no diagnostic message is printed.
colon (`:') is placed in NAME and `OPTARG' is set to the option
character found.
- `getopts' normally parses the positional parameters, but if more
- arguments are given in ARGS, `getopts' parses those instead.
-
`hash'
- hash [-r] [-p FILENAME] [NAME]
- Remember the full filenames of commands specified as arguments, so
- they need not be searched for on subsequent invocations. The
- commands are found by searching through the directories listed in
- `$PATH'. The `-p' option inhibits the path search, and FILENAME
- is used as the location of NAME. The `-r' option causes the shell
- to forget all remembered locations. If no arguments are given,
- information about remembered commands is printed.
+ hash [-r] [-p FILENAME] [-dt] [NAME]
+ Remember the full pathnames of commands specified as NAME
+ arguments, so they need not be searched for on subsequent
+ invocations. The commands are found by searching through the
+ directories listed in `$PATH'. The `-p' option inhibits the path
+ search, and FILENAME is used as the location of NAME. The `-r'
+ option causes the shell to forget all remembered locations. The
+ `-d' option causes the shell to forget the remembered location of
+ each NAME. If the `-t' option is supplied, the full pathname to
+ which each NAME corresponds is printed. If multiple NAME
+ arguments are supplied with `-t' the NAME is printed before the
+ hashed full pathname. The `-l' option causes output to be
+ displayed in a format that may be reused as input. If no
+ arguments are given, or if only `-l' is supplied, information
+ about remembered commands is printed. The return status is zero
+ unless a NAME is not found or an invalid option is supplied.
`pwd'
pwd [-LP]
- Print the current working directory. If the `-P' option is
- supplied, the path printed will not contain symbolic links. If
- the `-L' option is supplied, the path printed may contain symbolic
- links.
+ Print the absolute pathname of the current working directory. If
+ the `-P' option is supplied, the pathname printed will not contain
+ symbolic links. If the `-L' option is supplied, the pathname
+ printed may contain symbolic links. The return status is zero
+ unless an error is encountered while determining the name of the
+ current directory or an invalid option is supplied.
`readonly'
- readonly [-apf] [NAME] ...
- Mark each NAME as unchangable. The values of these names may not
- be changed by subsequent assignment. If the `-f' option is
- supplied, each NAME refers to a shell function. The `-a' option
- means each NAME refers to an array variable. If no NAME arguments
- are given, or if the `-p' option is supplied, a list of all
- readonly names is printed.
+ readonly [-aApf] [NAME[=VALUE]] ...
+ Mark each NAME as readonly. The values of these names may not be
+ changed by subsequent assignment. If the `-f' option is supplied,
+ each NAME refers to a shell function. The `-a' option means each
+ NAME refers to an indexed array variable; the `-A' option means
+ each NAME refers to an associative array variable. If no NAME
+ arguments are given, or if the `-p' option is supplied, a list of
+ all readonly names is printed. The `-p' option causes output to
+ be displayed in a format that may be reused as input. If a
+ variable name is followed by =VALUE, the value of the variable is
+ set to VALUE. The return status is zero unless an invalid option
+ is supplied, one of the NAME arguments is not a valid shell
+ variable or function name, or the `-f' option is supplied with a
+ name that is not a shell function.
`return'
return [N]
- Cause a shell function to exit with value N. This may also be used
- to terminate execution of a script being executed with the `.'
- builtin.
+ Cause a shell function to exit with the return value N. If N is
+ not supplied, the return value is the exit status of the last
+ command executed in the function. This may also be used to
+ terminate execution of a script being executed with the `.' (or
+ `source') builtin, returning either N or the exit status of the
+ last command executed within the script as the exit status of the
+ script. Any command associated with the `RETURN' trap is executed
+ before execution resumes after the function or script. The return
+ status is non-zero if `return' is used outside a function and not
+ during the execution of a script by `.' or `source'.
`shift'
shift [N]
- Shift positional parameters to the left by N. The positional
- parameters from N+1 ... are renamed to `$1' ... . Parameters
- represented by the numbers `$#' to N+1 are unset. N must be a
- non-negative number less than or equal to `$#'.
+ Shift the positional parameters to the left by N. The positional
+ parameters from N+1 ... `$#' are renamed to `$1' ... `$#'-N.
+ Parameters represented by the numbers `$#' to `$#'-N+1 are unset.
+ N must be a non-negative number less than or equal to `$#'. If N
+ is zero or greater than `$#', the positional parameters are not
+ changed. If N is not supplied, it is assumed to be 1. The return
+ status is zero unless N is greater than `$#' or less than zero,
+ non-zero otherwise.
`test'
`['
- Evaluate a conditional expression (*note Bash Conditional
- Expressions::.).
+ Evaluate a conditional expression EXPR. Each operator and operand
+ must be a separate argument. Expressions are composed of the
+ primaries described below in *note Bash Conditional Expressions::.
+ `test' does not accept any options, nor does it accept and ignore
+ an argument of `--' as signifying the end of options.
+
+ When the `[' form is used, the last argument to the command must
+ be a `]'.
+
+ Expressions may be combined using the following operators, listed
+ in decreasing order of precedence. The evaluation depends on the
+ number of arguments; see below.
+
+ `! EXPR'
+ True if EXPR is false.
+
+ `( EXPR )'
+ Returns the value of EXPR. This may be used to override the
+ normal precedence of operators.
+
+ `EXPR1 -a EXPR2'
+ True if both EXPR1 and EXPR2 are true.
+
+ `EXPR1 -o EXPR2'
+ True if either EXPR1 or EXPR2 is true.
+
+ The `test' and `[' builtins evaluate conditional expressions using
+ a set of rules based on the number of arguments.
+
+ 0 arguments
+ The expression is false.
+
+ 1 argument
+ The expression is true if and only if the argument is not
+ null.
+
+ 2 arguments
+ If the first argument is `!', the expression is true if and
+ only if the second argument is null. If the first argument
+ is one of the unary conditional operators (*note Bash
+ Conditional Expressions::), the expression is true if the
+ unary test is true. If the first argument is not a valid
+ unary operator, the expression is false.
+
+ 3 arguments
+ If the second argument is one of the binary conditional
+ operators (*note Bash Conditional Expressions::), the result
+ of the expression is the result of the binary test using the
+ first and third arguments as operands. The `-a' and `-o'
+ operators are considered binary operators when there are
+ three arguments. If the first argument is `!', the value is
+ the negation of the two-argument test using the second and
+ third arguments. If the first argument is exactly `(' and
+ the third argument is exactly `)', the result is the
+ one-argument test of the second argument. Otherwise, the
+ expression is false.
+
+ 4 arguments
+ If the first argument is `!', the result is the negation of
+ the three-argument expression composed of the remaining
+ arguments. Otherwise, the expression is parsed and evaluated
+ according to precedence using the rules listed above.
+
+ 5 or more arguments
+ The expression is parsed and evaluated according to precedence
+ using the rules listed above.
`times'
times
Print out the user and system times used by the shell and its
- children.
+ children. The return status is zero.
`trap'
trap [-lp] [ARG] [SIGSPEC ...]
The commands in ARG are to be read and executed when the shell
- receives signal SIGSPEC. If ARG is absent or equal to `-', all
- specified signals are reset to the values they had when the shell
- was started. If ARG is the null string, then the signal specified
- by each SIGSPEC is ignored by the shell and commands it invokes.
- If ARG is `-p', the shell displays the trap commands associated
- with each SIGSPEC. If no arguments are supplied, or only `-p' is
- given, `trap' prints the list of commands associated with each
- signal number. Each SIGSPEC is either a signal name such as
- `SIGINT' (with or without the `SIG' prefix) or a signal number.
- If a SIGSPEC is `0' or `EXIT', ARG is executed when the shell
- exits. If a SIGSPEC is `DEBUG', the command ARG is executed after
- every simple command. The `-l' option causes the shell to print a
- list of signal names and their corresponding numbers.
+ receives signal SIGSPEC. If ARG is absent (and there is a single
+ SIGSPEC) or equal to `-', each specified signal's disposition is
+ reset to the value it had when the shell was started. If ARG is
+ the null string, then the signal specified by each SIGSPEC is
+ ignored by the shell and commands it invokes. If ARG is not
+ present and `-p' has been supplied, the shell displays the trap
+ commands associated with each SIGSPEC. If no arguments are
+ supplied, or only `-p' is given, `trap' prints the list of commands
+ associated with each signal number in a form that may be reused as
+ shell input. The `-l' option causes the shell to print a list of
+ signal names and their corresponding numbers. Each SIGSPEC is
+ either a signal name or a signal number. Signal names are case
+ insensitive and the `SIG' prefix is optional. If a SIGSPEC is `0'
+ or `EXIT', ARG is executed when the shell exits. If a SIGSPEC is
+ `DEBUG', the command ARG is executed before every simple command,
+ `for' command, `case' command, `select' command, every arithmetic
+ `for' command, and before the first command executes in a shell
+ function. Refer to the description of the `extglob' option to the
+ `shopt' builtin (*note The Shopt Builtin::) for details of its
+ effect on the `DEBUG' trap. If a SIGSPEC is `ERR', the command ARG
+ is executed whenever a simple command has a non-zero exit status,
+ subject to the following conditions. The `ERR' trap is not
+ executed if the failed command is part of the command list
+ immediately following an `until' or `while' keyword, part of the
+ test in an `if' statement, part of a command executed in a `&&' or
+ `||' list, or if the command's return status is being inverted
+ using `!'. These are the same conditions obeyed by the `errexit'
+ option. If a SIGSPEC is `RETURN', the command ARG is executed
+ each time a shell function or a script executed with the `.' or
+ `source' builtins finishes executing.
Signals ignored upon entry to the shell cannot be trapped or reset.
- Trapped signals are reset to their original values in a child
- process when it is created.
+ Trapped signals that are not being ignored are reset to their
+ original values in a child process when it is created.
+
+ The return status is zero unless a SIGSPEC does not specify a
+ valid signal.
`umask'
- umask [-S] [MODE]
+ umask [-p] [-S] [MODE]
Set the shell process's file creation mask to MODE. If MODE
begins with a digit, it is interpreted as an octal number; if not,
it is interpreted as a symbolic mode mask similar to that accepted
by the `chmod' command. If MODE is omitted, the current value of
the mask is printed. If the `-S' option is supplied without a
- MODE argument, the mask is printed in a symbolic format.
+ MODE argument, the mask is printed in a symbolic format. If the
+ `-p' option is supplied, and MODE is omitted, the output is in a
+ form that may be reused as input. The return status is zero if
+ the mode is successfully changed or if no MODE argument is
+ supplied, and non-zero otherwise.
+
+ Note that when the mode is interpreted as an octal number, each
+ number of the umask is subtracted from `7'. Thus, a umask of `022'
+ results in permissions of `755'.
`unset'
unset [-fv] [NAME]
Each variable or function NAME is removed. If no options are
supplied, or the `-v' option is given, each NAME refers to a shell
variable. If the `-f' option is given, the NAMEs refer to shell
- functions, and the function definition is removed. Read-only
- variables and functions may not be unset.
+ functions, and the function definition is removed. Readonly
+ variables and functions may not be unset. The return status is
+ zero unless a NAME is readonly.
\1f
-File: bashref.info, Node: Bourne Shell Variables, Next: Other Bourne Shell Features, Prev: Bourne Shell Builtins, Up: Bourne Shell Features
+File: bashref.info, Node: Bash Builtins, Next: Modifying Shell Behavior, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
-Bourne Shell Variables
-======================
-
- Bash uses certain shell variables in the same way as the Bourne
-shell. In some cases, Bash assigns a default value to the variable.
+4.2 Bash Builtin Commands
+=========================
-`IFS'
- A list of characters that separate fields; used when the shell
- splits words as part of expansion.
+This section describes builtin commands which are unique to or have
+been extended in Bash. Some of these commands are specified in the
+POSIX standard.
-`PATH'
- A colon-separated list of directories in which the shell looks for
- commands.
+`alias'
+ alias [`-p'] [NAME[=VALUE] ...]
-`HOME'
- The current user's home directory; the default for the `cd' builtin
- command.
+ Without arguments or with the `-p' option, `alias' prints the list
+ of aliases on the standard output in a form that allows them to be
+ reused as input. If arguments are supplied, an alias is defined
+ for each NAME whose VALUE is given. If no VALUE is given, the name
+ and value of the alias is printed. Aliases are described in *note
+ Aliases::.
-`CDPATH'
- A colon-separated list of directories used as a search path for
- the `cd' command.
+`bind'
+ bind [-m KEYMAP] [-lpsvPSV]
+ bind [-m KEYMAP] [-q FUNCTION] [-u FUNCTION] [-r KEYSEQ]
+ bind [-m KEYMAP] -f FILENAME
+ bind [-m KEYMAP] -x KEYSEQ:SHELL-COMMAND
+ bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
+ bind READLINE-COMMAND
-`MAILPATH'
- A colon-separated list of files which the shell periodically checks
- for new mail. You can also specify what message is printed by
- separating the file name from the message with a `?'. When used
- in the text of the message, `$_' stands for the name of the
- current mailfile.
+ Display current Readline (*note Command Line Editing::) key and
+ function bindings, bind a key sequence to a Readline function or
+ macro, or set a Readline variable. Each non-option argument is a
+ command as it would appear in a Readline initialization file
+ (*note Readline Init File::), but each binding or command must be
+ passed as a separate argument; e.g.,
+ `"\C-x\C-r":re-read-init-file'.
-`MAIL'
- If this parameter is set to a filename and the `MAILPATH' variable
- is not set, Bash informs the user of the arrival of mail in the
- specified file.
+ Options, if supplied, have the following meanings:
-`PS1'
- The primary prompt string. The default value is `\s-\v\$ '.
+ `-m KEYMAP'
+ Use KEYMAP as the keymap to be affected by the subsequent
+ bindings. Acceptable KEYMAP names are `emacs',
+ `emacs-standard', `emacs-meta', `emacs-ctlx', `vi', `vi-move',
+ `vi-command', and `vi-insert'. `vi' is equivalent to
+ `vi-command'; `emacs' is equivalent to `emacs-standard'.
-`PS2'
- The secondary prompt string. The default value is `> '.
+ `-l'
+ List the names of all Readline functions.
-`OPTIND'
- The index of the last option processed by the `getopts' builtin.
+ `-p'
+ Display Readline function names and bindings in such a way
+ that they can be used as input or in a Readline
+ initialization file.
-`OPTARG'
- The value of the last option argument processed by the `getopts'
- builtin.
+ `-P'
+ List current Readline function names and bindings.
-\1f
-File: bashref.info, Node: Other Bourne Shell Features, Prev: Bourne Shell Variables, Up: Bourne Shell Features
+ `-v'
+ Display Readline variable names and values in such a way that
+ they can be used as input or in a Readline initialization
+ file.
-Other Bourne Shell Features
-===========================
+ `-V'
+ List current Readline variable names and values.
-* Menu:
+ `-s'
+ Display Readline key sequences bound to macros and the
+ strings they output in such a way that they can be used as
+ input or in a Readline initialization file.
-* Major Differences From The Bourne Shell:: Major differences between
- Bash and the Bourne shell.
+ `-S'
+ Display Readline key sequences bound to macros and the
+ strings they output.
- Bash implements essentially the same grammar, parameter and variable
-expansion, redirection, and quoting as the Bourne Shell. Bash uses the
-POSIX 1003.2 standard as the specification of how these features are to
-be implemented. There are some differences between the traditional
-Bourne shell and the POSIX standard; this section quickly details the
-differences of significance. A number of these differences are
-explained in greater depth in subsequent sections.
+ `-f FILENAME'
+ Read key bindings from FILENAME.
-\1f
-File: bashref.info, Node: Major Differences From The Bourne Shell, Up: Other Bourne Shell Features
+ `-q FUNCTION'
+ Query about which keys invoke the named FUNCTION.
-Major Differences From The SVR4.2 Bourne Shell
-----------------------------------------------
+ `-u FUNCTION'
+ Unbind all keys bound to the named FUNCTION.
- Bash is POSIX-conformant, even where the POSIX specification differs
-from traditional `sh' behavior.
+ `-r KEYSEQ'
+ Remove any current binding for KEYSEQ.
- Bash has multi-character invocation options (*note Invoking Bash::.).
+ `-x KEYSEQ:SHELL-COMMAND'
+ Cause SHELL-COMMAND to be executed whenever KEYSEQ is entered.
+ When SHELL-COMMAND is executed, the shell sets the
+ `READLINE_LINE' variable to the contents of the Readline line
+ buffer and the `READLINE_POINT' variable to the current
+ location of the insertion point. If the executed command
+ changes the value of `READLINE_LINE' or `READLINE_POINT',
+ those new values will be reflected in the editing state.
- Bash has command-line editing (*note Command Line Editing::.) and
-the `bind' builtin.
+ The return status is zero unless an invalid option is supplied or
+ an error occurs.
- Bash has command history (*note Bash History Facilities::.) and the
-`history' and `fc' builtins to manipulate it.
+`builtin'
+ builtin [SHELL-BUILTIN [ARGS]]
+ Run a shell builtin, passing it ARGS, and return its exit status.
+ This is useful when defining a shell function with the same name
+ as a shell builtin, retaining the functionality of the builtin
+ within the function. The return status is non-zero if
+ SHELL-BUILTIN is not a shell builtin command.
+
+`caller'
+ caller [EXPR]
+ Returns the context of any active subroutine call (a shell
+ function or a script executed with the `.' or `source' builtins).
+
+ Without EXPR, `caller' displays the line number and source
+ filename of the current subroutine call. If a non-negative
+ integer is supplied as EXPR, `caller' displays the line number,
+ subroutine name, and source file corresponding to that position in
+ the current execution call stack. This extra information may be
+ used, for example, to print a stack trace. The current frame is
+ frame 0.
+
+ The return value is 0 unless the shell is not executing a
+ subroutine call or EXPR does not correspond to a valid position in
+ the call stack.
- Bash implements `csh'-like history expansion (*note History
-Interaction::.).
+`command'
+ command [-pVv] COMMAND [ARGUMENTS ...]
+ Runs COMMAND with ARGUMENTS ignoring any shell function named
+ COMMAND. Only shell builtin commands or commands found by
+ searching the `PATH' are executed. If there is a shell function
+ named `ls', running `command ls' within the function will execute
+ the external command `ls' instead of calling the function
+ recursively. The `-p' option means to use a default value for
+ `PATH' that is guaranteed to find all of the standard utilities.
+ The return status in this case is 127 if COMMAND cannot be found
+ or an error occurred, and the exit status of COMMAND otherwise.
- Bash has one-dimensional array variables (*note Arrays::.), and the
-appropriate variable expansions and assignment syntax to use them.
-Some of the Bash builtins take options to act on arrays. Bash provides
-some built-in array variables.
+ If either the `-V' or `-v' option is supplied, a description of
+ COMMAND is printed. The `-v' option causes a single word
+ indicating the command or file name used to invoke COMMAND to be
+ displayed; the `-V' option produces a more verbose description.
+ In this case, the return status is zero if COMMAND is found, and
+ non-zero if not.
- Bash implements the `!' keyword to negate the return value of a
-pipeline (*note Pipelines::.). Very useful when an `if' statement
-needs to act only if a test fails.
+`declare'
+ declare [-aAfFilrtux] [-p] [NAME[=VALUE] ...]
- Bash includes the `select' compound command, which allows the
-generation of simple menus (*note Korn Shell Constructs::.).
+ Declare variables and give them attributes. If no NAMEs are
+ given, then display the values of variables instead.
- Bash includes brace expansion (*note Brace Expansion::.) and tilde
-expansion (*note Tilde Expansion::.).
+ The `-p' option will display the attributes and values of each
+ NAME. When `-p' is used with NAME arguments, additional options
+ are ignored.
+
+ When `-p' is supplied without NAME arguments, `declare' will
+ display the attributes and values of all variables having the
+ attributes specified by the additional options. If no other
+ options are supplied with `-p', `declare' will display the
+ attributes and values of all shell variables. The `-f' option
+ will restrict the display to shell functions.
+
+ The `-F' option inhibits the display of function definitions; only
+ the function name and attributes are printed. If the `extdebug'
+ shell option is enabled using `shopt' (*note The Shopt Builtin::),
+ the source file name and line number where the function is defined
+ are displayed as well. `-F' implies `-f'. The following options
+ can be used to restrict output to variables with the specified
+ attributes or to give variables attributes:
- Bash implements command aliases and the `alias' and `unalias'
-builtins (*note Aliases::.).
+ `-a'
+ Each NAME is an indexed array variable (*note Arrays::).
- Bash provides shell arithmetic and arithmetic expansion (*note Shell
-Arithmetic::.).
+ `-A'
+ Each NAME is an associative array variable (*note Arrays::).
- The POSIX and `ksh'-style `$()' form of command substitution is
-implemented (*note Command Substitution::.), and preferred to the
-Bourne shell's ```' (which is also implemented for backwards
-compatibility).
+ `-f'
+ Use function names only.
- Variables present in the shell's initial environment are
-automatically exported to child processes. The Bourne shell does not
-normally do this unless the variables are explicitly marked using the
-`export' command.
+ `-i'
+ The variable is to be treated as an integer; arithmetic
+ evaluation (*note Shell Arithmetic::) is performed when the
+ variable is assigned a value.
- Bash includes the POSIX and `ksh'-style pattern removal `%', `#',
-`%%' and `##' constructs to remove leading or trailing substrings from
-variable values (*note Shell Parameter Expansion::.).
+ `-l'
+ When the variable is assigned a value, all upper-case
+ characters are converted to lower-case. The upper-case
+ attribute is disabled.
- The expansion `${#xx}', which returns the length of `$xx', is
-supported (*note Shell Parameter Expansion::.).
+ `-r'
+ Make NAMEs readonly. These names cannot then be assigned
+ values by subsequent assignment statements or unset.
- The `$'...'' quoting syntax, which expands ANSI-C backslash-escaped
-characters in the text between the single quotes, is supported (*note
-ANSI-C Quoting::.).
+ `-t'
+ Give each NAME the `trace' attribute. Traced functions
+ inherit the `DEBUG' and `RETURN' traps from the calling shell.
+ The trace attribute has no special meaning for variables.
- Bash supports the `$"..."' quoting syntax to do locale-specific
-translation of the characters between the double quotes. The `-D' and
-`--dump-strings' invocation options list the translatable strings found
-in a script (*note Locale Translation::.).
+ `-u'
+ When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
+ attribute is disabled.
- The expansion `${var:'OFFSET`[:'LENGTH`]}', which expands to the
-substring of `var''s value of length LENGTH, optionally beginning at
-OFFSET, is present (*note Shell Parameter Expansion::.).
+ `-x'
+ Mark each NAME for export to subsequent commands via the
+ environment.
- The expansion `${var/[/]'PATTERN`[/'REPLACEMENT`]}', which matches
-PATTERN and replaces it with REPLACEMENT in the value of `var', is
-available (*note Shell Parameter Expansion::.).
+ Using `+' instead of `-' turns off the attribute instead, with the
+ exceptions that `+a' may not be used to destroy an array variable
+ and `+r' will not remove the readonly attribute. When used in a
+ function, `declare' makes each NAME local, as with the `local'
+ command. If a variable name is followed by =VALUE, the value of
+ the variable is set to VALUE.
+
+ The return status is zero unless an invalid option is encountered,
+ an attempt is made to define a function using `-f foo=bar', an
+ attempt is made to assign a value to a readonly variable, an
+ attempt is made to assign a value to an array variable without
+ using the compound assignment syntax (*note Arrays::), one of the
+ NAMES is not a valid shell variable name, an attempt is made to
+ turn off readonly status for a readonly variable, an attempt is
+ made to turn off array status for an array variable, or an attempt
+ is made to display a non-existent function with `-f'.
- Bash has INDIRECT variable expansion using `${!word}' (*note Shell
-Parameter Expansion::.).
+`echo'
+ echo [-neE] [ARG ...]
+ Output the ARGs, separated by spaces, terminated with a newline.
+ The return status is always 0. If `-n' is specified, the trailing
+ newline is suppressed. If the `-e' option is given,
+ interpretation of the following backslash-escaped characters is
+ enabled. The `-E' option disables the interpretation of these
+ escape characters, even on systems where they are interpreted by
+ default. The `xpg_echo' shell option may be used to dynamically
+ determine whether or not `echo' expands these escape characters by
+ default. `echo' does not interpret `--' to mean the end of
+ options.
- Bash can expand positional parameters beyond `$9' using `${NUM}'.
+ `echo' interprets the following escape sequences:
+ `\a'
+ alert (bell)
- Bash has process substitution (*note Process Substitution::.).
+ `\b'
+ backspace
- Bash automatically assigns variables that provide information about
-the current user (`UID', `EUID', and `GROUPS'), the current host
-(`HOSTTYPE', `OSTYPE', `MACHTYPE', and `HOSTNAME'), and the instance of
-Bash that is running (`BASH', `BASH_VERSION', and `BASH_VERSINFO'.
-*Note Bash Variables::, for details.
+ `\c'
+ suppress further output
- The `IFS' variable is used to split only the results of expansion,
-not all words (*note Word Splitting::.). This closes a longstanding
-shell security hole.
+ `\e'
+ escape
- It is possible to have a variable and a function with the same name;
-`sh' does not separate the two name spaces.
+ `\f'
+ form feed
- Bash functions are permitted to have local variables using the
-`local' builtin, and thus useful recursive functions may be written.
+ `\n'
+ new line
- Variable assignments preceding commands affect only that command,
-even builtins and functions (*note Environment::.). In `sh', all
-variable assignments preceding commands are global unless the command
-is executed from the file system.
+ `\r'
+ carriage return
- Bash performs filename expansion on filenames specified as operands
-to output redirection operators.
+ `\t'
+ horizontal tab
- Bash contains the `<>' redirection operator, allowing a file to be
-opened for both reading and writing, and the `&>' redirection operator,
-for directing standard output and standard error to the same file
-(*note Redirections::.).
+ `\v'
+ vertical tab
- The `noclobber' option is available to avoid overwriting existing
-files with output redirection (*note The Set Builtin::.). The `>|'
-redirection operator may be used to override `noclobber'.
+ `\\'
+ backslash
- Bash interprets special backslash-escaped characters in the prompt
-strings when interactive (*note Printing a Prompt::.).
+ `\0NNN'
+ the eight-bit character whose value is the octal value NNN
+ (zero to three octal digits)
- Bash allows you to write a function to override a builtin, and
-provides access to that builtin's functionality within the function via
-the `builtin' and `command' builtins (*note Bash Builtins::.).
+ `\xHH'
+ the eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits)
- The `command' builtin allows selective disabling of functions when
-command lookup is performed (*note Bash Builtins::.).
+`enable'
+ enable [-a] [-dnps] [-f FILENAME] [NAME ...]
+ Enable and disable builtin shell commands. Disabling a builtin
+ allows a disk command which has the same name as a shell builtin
+ to be executed without specifying a full pathname, even though the
+ shell normally searches for builtins before disk commands. If
+ `-n' is used, the NAMEs become disabled. Otherwise NAMEs are
+ enabled. For example, to use the `test' binary found via `$PATH'
+ instead of the shell builtin version, type `enable -n test'.
- Individual builtins may be enabled or disabled using the `enable'
-builtin (*note Bash Builtins::.).
+ If the `-p' option is supplied, or no NAME arguments appear, a
+ list of shell builtins is printed. With no other arguments, the
+ list consists of all enabled shell builtins. The `-a' option
+ means to list each builtin with an indication of whether or not it
+ is enabled.
- The Bash `hash' builtin allows a name to be associated with an
-arbitrary filename, even when that filename cannot be found by
-searching the `$PATH', using `hash -p'.
+ The `-f' option means to load the new builtin command NAME from
+ shared object FILENAME, on systems that support dynamic loading.
+ The `-d' option will delete a builtin loaded with `-f'.
- Shell functions may be exported to children via the environment
-(*note Shell Functions::.).
+ If there are no options, a list of the shell builtins is displayed.
+ The `-s' option restricts `enable' to the POSIX special builtins.
+ If `-s' is used with `-f', the new builtin becomes a special
+ builtin (*note Special Builtins::).
- Bash includes a `help' builtin for quick reference to shell
-facilities (*note Bash Builtins::.).
+ The return status is zero unless a NAME is not a shell builtin or
+ there is an error loading a new builtin from a shared object.
- The Bash `read' builtin (*note Bash Builtins::.) will read a line
-ending in `\' with the `-r' option, and will use the `REPLY' variable
-as a default if no arguments are supplied. The Bash `read' builtin
-also accepts a prompt string with the `-p' option and will use Readline
-to obtain the line when given the `-e' option.
+`help'
+ help [-dms] [PATTERN]
+ Display helpful information about builtin commands. If PATTERN is
+ specified, `help' gives detailed help on all commands matching
+ PATTERN, otherwise a list of the builtins is printed.
- Bash includes the `shopt' builtin, for finer control of shell
-optional capabilities (*note Bash Builtins::.).
+ Options, if supplied, have the following meanings:
- Bash has much more optional behavior controllable with the `set'
-builtin (*note The Set Builtin::.).
+ `-d'
+ Display a short description of each PATTERN
- The `disown' builtin can remove a job from the internal shell job
-table (*note Job Control Builtins::.).
+ `-m'
+ Display the description of each PATTERN in a manpage-like
+ format
- The `return' builtin may be used to abort execution of scripts
-executed with the `.' or `source' builtins (*note Bourne Shell
-Builtins::.).
+ `-s'
+ Display only a short usage synopsis for each PATTERN
- The `test' builtin (*note Bourne Shell Builtins::.) is slightly
-different, as it implements the POSIX 1003.2 algorithm, which specifies
-the behavior based on the number of arguments.
+ The return status is zero unless no command matches PATTERN.
- The `trap' builtin (*note Bourne Shell Builtins::.) allows a `DEBUG'
-pseudo-signal specification, similar to `EXIT'. Commands specified
-with a `DEBUG' trap are executed after every simple command. The
-`DEBUG' trap is not inherited by shell functions.
+`let'
+ let EXPRESSION [EXPRESSION]
+ The `let' builtin allows arithmetic to be performed on shell
+ variables. Each EXPRESSION is evaluated according to the rules
+ given below in *note Shell Arithmetic::. If the last EXPRESSION
+ evaluates to 0, `let' returns 1; otherwise 0 is returned.
- The Bash `export', `readonly', and `declare' builtins can take a
-`-f' option to act on shell functions, a `-p' option to display
-variables with various attributes set in a format that can be used as
-shell input, a `-n' option to remove various variable attributes, and
-`name=value' arguments to set variable attributes and values
-simultaneously.
+`local'
+ local [OPTION] NAME[=VALUE] ...
+ For each argument, a local variable named NAME is created, and
+ assigned VALUE. The OPTION can be any of the options accepted by
+ `declare'. `local' can only be used within a function; it makes
+ the variable NAME have a visible scope restricted to that function
+ and its children. The return status is zero unless `local' is
+ used outside a function, an invalid NAME is supplied, or NAME is a
+ readonly variable.
- The Bash `cd' and `pwd' builtins (*note Bourne Shell Builtins::.)
-each take `-L' and `-P' builtins to switch between logical and physical
-modes.
+`logout'
+ logout [N]
+ Exit a login shell, returning a status of N to the shell's parent.
- The Bash `type' builtin is more extensive and gives more information
-about the names it finds (*note Bash Builtins::.).
+`mapfile'
+ mapfile [-n COUNT] [-O ORIGIN] [-s COUNT] [-t] [-u FD] [
+ -C CALLBACK] [-c QUANTUM] [ARRAY]
+ Read lines from the standard input into array variable ARRAY, or
+ from file descriptor FD if the `-u' option is supplied. The
+ variable `MAPFILE' is the default ARRAY. Options, if supplied,
+ have the following meanings:
+ `-n'
+ Copy at most COUNT lines. If COUNT is 0, all lines are
+ copied.
- Bash implements a `csh'-like directory stack, and provides the
-`pushd', `popd', and `dirs' builtins to manipulate it (*note C Shell
-Builtins::.). Bash also makes the directory stack visible as the value
-of the `DIRSTACK' shell variable.
+ `-O'
+ Begin assigning to ARRAY at index ORIGIN. The default index
+ is 0.
- The Bash restricted mode is more useful (*note The Restricted
-Shell::.); the SVR4.2 shell restricted mode is too limited.
+ `-s'
+ Discard the first COUNT lines read.
- Bash has the `time' reserved word and command timing (*note
-Pipelines::.). The display of the timing statistics may be controlled
-with the `TIMEFORMAT' variable.
+ `-t'
+ Remove a trailing line from each line read.
- The SVR4.2 shell has two privilege-related builtins (`mldmode' and
-`priv') not present in Bash.
+ `-u'
+ Read lines from file descriptor FD instead of the standard
+ input.
- Bash does not have the `stop' or `newgrp' builtins.
+ `-C'
+ Evaluate CALLBACK each time QUANTUMP lines are read. The
+ `-c' option specifies QUANTUM.
- Bash does not use the `SHACCT' variable or perform shell accounting.
+ `-c'
+ Specify the number of lines read between each call to
+ CALLBACK.
+
+ If `-C' is specified without `-c', the default quantum is 5000.
+
+ If not supplied with an explicit origin, `mapfile' will clear ARRAY
+ before assigning to it.
+
+ `mapfile' returns successfully unless an invalid option or option
+ argument is supplied, or ARRAY is invalid or unassignable.
+
+`printf'
+ printf [-v VAR] FORMAT [ARGUMENTS]
+ Write the formatted ARGUMENTS to the standard output under the
+ control of the FORMAT. The FORMAT is a character string which
+ contains three types of objects: plain characters, which are
+ simply copied to standard output, character escape sequences,
+ which are converted and copied to the standard output, and format
+ specifications, each of which causes printing of the next
+ successive ARGUMENT. In addition to the standard `printf(1)'
+ formats, `%b' causes `printf' to expand backslash escape sequences
+ in the corresponding ARGUMENT, (except that `\c' terminates
+ output, backslashes in `\'', `\"', and `\?' are not removed, and
+ octal escapes beginning with `\0' may contain up to four digits),
+ and `%q' causes `printf' to output the corresponding ARGUMENT in a
+ format that can be reused as shell input.
+
+ The `-v' option causes the output to be assigned to the variable
+ VAR rather than being printed to the standard output.
+
+ The FORMAT is reused as necessary to consume all of the ARGUMENTS.
+ If the FORMAT requires more ARGUMENTS than are supplied, the extra
+ format specifications behave as if a zero value or null string, as
+ appropriate, had been supplied. The return value is zero on
+ success, non-zero on failure.
- The SVR4.2 `sh' uses a `TIMEOUT' variable like Bash uses `TMOUT'.
+`read'
+ read [-ers] [-a ANAME] [-d DELIM] [-i TEXT] [-n NCHARS] [-p PROMPT] [-t TIMEOUT] [-u FD] [NAME ...]
+ One line is read from the standard input, or from the file
+ descriptor FD supplied as an argument to the `-u' option, and the
+ first word is assigned to the first NAME, the second word to the
+ second NAME, and so on, with leftover words and their intervening
+ separators assigned to the last NAME. If there are fewer words
+ read from the input stream than names, the remaining names are
+ assigned empty values. The characters in the value of the `IFS'
+ variable are used to split the line into words. The backslash
+ character `\' may be used to remove any special meaning for the
+ next character read and for line continuation. If no names are
+ supplied, the line read is assigned to the variable `REPLY'. The
+ return code is zero, unless end-of-file is encountered, `read'
+ times out (in which case the return code is greater than 128), or
+ an invalid file descriptor is supplied as the argument to `-u'.
+
+ Options, if supplied, have the following meanings:
- More features unique to Bash may be found in *Note Bash Features::.
+ `-a ANAME'
+ The words are assigned to sequential indices of the array
+ variable ANAME, starting at 0. All elements are removed from
+ ANAME before the assignment. Other NAME arguments are
+ ignored.
-Implementation Differences From The SVR4.2 Shell
-------------------------------------------------
+ `-d DELIM'
+ The first character of DELIM is used to terminate the input
+ line, rather than newline.
- Since Bash is a completely new implementation, it does not suffer
-from many of the limitations of the SVR4.2 shell. For instance:
+ `-e'
+ Readline (*note Command Line Editing::) is used to obtain the
+ line. Readline uses the current (or default, if line editing
+ was not previously active) editing settings.
- * Bash does not fork a subshell when redirecting into or out of a
- shell control structure such as an `if' or `while' statement.
+ `-i TEXT'
+ If Readline is being used to read the line, TEXT is placed
+ into the editing buffer before editing begins.
- * Bash does not allow unbalanced quotes. The SVR4.2 shell will
- silently insert a needed closing quote at `EOF' under certain
- circumstances. This can be the cause of some hard-to-find errors.
+ `-n NCHARS'
+ `read' returns after reading NCHARS characters rather than
+ waiting for a complete line of input.
- * The SVR4.2 shell uses a baroque memory management scheme based on
- trapping `SIGSEGV'. If the shell is started from a process with
- `SIGSEGV' blocked (e.g., by using the `system()' C library
- function call), the shell misbehaves badly.
+ `-p PROMPT'
+ Display PROMPT, without a trailing newline, before attempting
+ to read any input. The prompt is displayed only if input is
+ coming from a terminal.
- * In a questionable attempt at security, the SVR4.2 shell, when
- invoked without the `-p' option, will alter its real and effective
- UID and GID if they are less than some magic threshold value,
- commonly 100. This can lead to unexpected results.
+ `-r'
+ If this option is given, backslash does not act as an escape
+ character. The backslash is considered to be part of the
+ line. In particular, a backslash-newline pair may not be
+ used as a line continuation.
- * The SVR4.2 shell does not allow users to trap `SIGALRM' or
- `SIGCHLD'.
+ `-s'
+ Silent mode. If input is coming from a terminal, characters
+ are not echoed.
- * For some reason, the SVR4.2 shell does not allow the `MAILCHECK'
- variable to be unset.
+ `-t TIMEOUT'
+ Cause `read' to time out and return failure if a complete
+ line of input is not read within TIMEOUT seconds. TIMEOUT
+ may be a decimal number with a fractional portion following
+ the decimal point. This option is only effective if `read'
+ is reading input from a terminal, pipe, or other special
+ file; it has no effect when reading from regular files. If
+ TIMEOUT is 0, `read' returns success if input is available on
+ the specified file descriptor, failure otherwise. The exit
+ status is greater than 128 if the timeout is exceeded.
- * The SVR4.2 shell treats `^' as the undocumented equivalent of `|'.
+ `-u FD'
+ Read input from file descriptor FD.
- * Bash allows multiple option arguments when it is invoked (`-x -v');
- the SVR4.2 shell allows only one option argument (`-xv'). In
- fact, some versions of the shell dump core if the second argument
- begins with a `-'.
- * The SVR4.2 shell exits a script if any builtin fails; Bash exits a
- script only if one of the POSIX.2 special builtins fails, and only
- for certain failures, as enumerated in the POSIX.2 standard.
+`source'
+ source FILENAME
+ A synonym for `.' (*note Bourne Shell Builtins::).
- * The SVR4.2 shell behaves differently when invoked as `jsh' (it
- turns on job control).
+`type'
+ type [-afptP] [NAME ...]
+ For each NAME, indicate how it would be interpreted if used as a
+ command name.
-\1f
-File: bashref.info, Node: Csh Features, Next: Korn Shell Features, Prev: Bourne Shell Features, Up: Top
+ If the `-t' option is used, `type' prints a single word which is
+ one of `alias', `function', `builtin', `file' or `keyword', if
+ NAME is an alias, shell function, shell builtin, disk file, or
+ shell reserved word, respectively. If the NAME is not found, then
+ nothing is printed, and `type' returns a failure status.
-C-Shell Style Features
-**********************
+ If the `-p' option is used, `type' either returns the name of the
+ disk file that would be executed, or nothing if `-t' would not
+ return `file'.
- The C-Shell ("`csh'") was created by Bill Joy at The University of
-California at Berkeley. It is generally considered to have better
-features for interactive use than the original Bourne shell. Some of
-the `csh' features present in Bash include job control, history
-expansion, `protected' redirection, and several variables to control
-the interactive behaviour of the shell (e.g., `IGNOREEOF').
+ The `-P' option forces a path search for each NAME, even if `-t'
+ would not return `file'.
- *Note Using History Interactively::, for details on history
-expansion.
+ If a command is hashed, `-p' and `-P' print the hashed value, not
+ necessarily the file that appears first in `$PATH'.
-* Menu:
+ If the `-a' option is used, `type' returns all of the places that
+ contain an executable named FILE. This includes aliases and
+ functions, if and only if the `-p' option is not also used.
-* Brace Expansion:: Expansion of expressions within braces.
-* Tilde Expansion:: Expansion of the ~ character.
-* C Shell Builtins:: Builtin commands adopted from the C Shell.
-* C Shell Variables:: Variables which Bash uses in essentially
- the same way as the C Shell.
+ If the `-f' option is used, `type' does not attempt to find shell
+ functions, as with the `command' builtin.
-\1f
-File: bashref.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Csh Features
+ The return status is zero if all of the NAMES are found, non-zero
+ if any are not found.
-Brace Expansion
-===============
+`typeset'
+ typeset [-afFrxi] [-p] [NAME[=VALUE] ...]
+ The `typeset' command is supplied for compatibility with the Korn
+ shell; however, it has been deprecated in favor of the `declare'
+ builtin command.
- Brace expansion is a mechanism by which arbitrary strings may be
-generated. This mechanism is similar to FILENAME EXPANSION (*note
-Filename Expansion::.), but the file names generated need not exist.
-Patterns to be brace expanded take the form of an optional PREAMBLE,
-followed by a series of comma-separated strings between a pair of
-braces, followed by an optional POSTAMBLE. The preamble is prepended
-to each string contained within the braces, and the postamble is then
-appended to each resulting string, expanding left to right.
+`ulimit'
+ ulimit [-abcdefilmnpqrstuvxHST] [LIMIT]
+ `ulimit' provides control over the resources available to processes
+ started by the shell, on systems that allow such control. If an
+ option is given, it is interpreted as follows:
+ `-S'
+ Change and report the soft limit associated with a resource.
- Brace expansions may be nested. The results of each expanded string
-are not sorted; left to right order is preserved. For example,
- bash$ echo a{d,c,b}e
- ade ace abe
+ `-H'
+ Change and report the hard limit associated with a resource.
- Brace expansion is performed before any other expansions, and any
-characters special to other expansions are preserved in the result. It
-is strictly textual. Bash does not apply any syntactic interpretation
-to the context of the expansion or the text between the braces.
+ `-a'
+ All current limits are reported.
- A correctly-formed brace expansion must contain unquoted opening and
-closing braces, and at least one unquoted comma. Any incorrectly
-formed brace expansion is left unchanged.
+ `-b'
+ The maximum socket buffer size.
- This construct is typically used as shorthand when the common prefix
-of the strings to be generated is longer than in the above example:
- mkdir /usr/local/src/bash/{old,new,dist,bugs}
- or
- chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+ `-c'
+ The maximum size of core files created.
-\1f
-File: bashref.info, Node: Tilde Expansion, Next: C Shell Builtins, Prev: Brace Expansion, Up: Csh Features
+ `-d'
+ The maximum size of a process's data segment.
-Tilde Expansion
-===============
+ `-e'
+ The maximum scheduling priority ("nice").
- Bash has tilde (~) expansion, similar, but not identical, to that of
-`csh'. The following table shows what unquoted words beginning with a
-tilde expand to.
+ `-f'
+ The maximum size of files written by the shell and its
+ children.
-`~'
- The current value of `$HOME'.
+ `-i'
+ The maximum number of pending signals.
-`~/foo'
- `$HOME/foo'
+ `-l'
+ The maximum size that may be locked into memory.
-`~fred/foo'
- The subdirectory `foo' of the home directory of the user `fred'.
+ `-m'
+ The maximum resident set size.
-`~+/foo'
- `$PWD/foo'
+ `-n'
+ The maximum number of open file descriptors.
-`~-/foo'
- `$OLDPWD/foo'
+ `-p'
+ The pipe buffer size.
- Bash will also tilde expand words following redirection operators
-and words following `=' in assignment statements.
+ `-q'
+ The maximum number of bytes in POSIX message queues.
-\1f
-File: bashref.info, Node: C Shell Builtins, Next: C Shell Variables, Prev: Tilde Expansion, Up: Csh Features
+ `-r'
+ The maximum real-time scheduling priority.
-C Shell Builtins
-================
+ `-s'
+ The maximum stack size.
- Bash has several builtin commands whose definition is very similar
-to `csh'.
+ `-t'
+ The maximum amount of cpu time in seconds.
-`pushd'
- pushd [DIR | +N | -N] [-n]
+ `-u'
+ The maximum number of processes available to a single user.
- Save the current directory on a list and then `cd' to DIR. With no
- arguments, exchanges the top two directories.
+ `-v'
+ The maximum amount of virtual memory available to the process.
- `+N'
- Brings the Nth directory (counting from the left of the list
- printed by `dirs', starting with zero) to the top of the list
- by rotating the stack.
+ `-x'
+ The maximum number of file locks.
- `-N'
- Brings the Nth directory (counting from the right of the list
- printed by `dirs', starting with zero) to the top of the list
- by rotating the stack.
+ `-T'
+ The maximum number of threads.
- `-n'
- Suppresses the normal change of directory when adding
- directories to the stack, so that only the stack is
- manipulated.
- `DIR'
- Makes the current working directory be the top of the stack,
- and then `cd's to DIR. You can see the saved directory list
- with the `dirs' command.
+ If LIMIT is given, it is the new value of the specified resource;
+ the special LIMIT values `hard', `soft', and `unlimited' stand for
+ the current hard limit, the current soft limit, and no limit,
+ respectively. A hard limit cannot be increased by a non-root user
+ once it is set; a soft limit may be increased up to the value of
+ the hard limit. Otherwise, the current value of the soft limit
+ for the specified resource is printed, unless the `-H' option is
+ supplied. When setting new limits, if neither `-H' nor `-S' is
+ supplied, both the hard and soft limits are set. If no option is
+ given, then `-f' is assumed. Values are in 1024-byte increments,
+ except for `-t', which is in seconds, `-p', which is in units of
+ 512-byte blocks, and `-n' and `-u', which are unscaled values.
-`popd'
- popd [+N | -N] [-n]
+ The return status is zero unless an invalid option or argument is
+ supplied, or an error occurs while setting a new limit.
- Pop the directory stack, and `cd' to the new top directory. When
- no arguments are given, `popd' removes the top directory from the
- stack and performs a `cd' to the new top directory. The elements
- are numbered from 0 starting at the first directory listed with
- `dirs'; i.e., `popd' is equivalent to `popd +0'.
- `+N'
- Removes the Nth directory (counting from the left of the list
- printed by `dirs'), starting with zero.
+`unalias'
+ unalias [-a] [NAME ... ]
- `-N'
- Removes the Nth directory (counting from the right of the
- list printed by `dirs'), starting with zero.
+ Remove each NAME from the list of aliases. If `-a' is supplied,
+ all aliases are removed. Aliases are described in *note Aliases::.
- `-n'
- Suppresses the normal change of directory when removing
- directories from the stack, so that only the stack is
- manipulated.
-`dirs'
- dirs [+N | -N] [-clvp]
- Display the list of currently remembered directories. Directories
- find their way onto the list with the `pushd' command; you can get
- back up through the list with the `popd' command.
- `+N'
- Displays the Nth directory (counting from the left of the
- list printed by `dirs' when invoked without options), starting
- with zero.
+\1f
+File: bashref.info, Node: Modifying Shell Behavior, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
- `-N'
- Displays the Nth directory (counting from the right of the
- list printed by `dirs' when invoked without options), starting
- with zero.
+4.3 Modifying Shell Behavior
+============================
- `-c'
- Clears the directory stack by deleting all of the elements.
+* Menu:
- `-l'
- Produces a longer listing; the default listing format uses a
- tilde to denote the home directory.
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
- `-p'
- Causes `dirs' to print the directory stack with one entry per
- line.
+\1f
+File: bashref.info, Node: The Set Builtin, Next: The Shopt Builtin, Up: Modifying Shell Behavior
- `-v'
- Causes `dirs' to print the directory stack with one entry per
- line, prepending each entry with its index in the stack.
+4.3.1 The Set Builtin
+---------------------
-`history'
- history [-c] [N]
- history [-anrw] [FILENAME]
- history -ps ARG
+This builtin is so complicated that it deserves its own section. `set'
+allows you to change the values of shell options and set the positional
+parameters, or to display the names and values of shell variables.
- Display the history list with line numbers. Lines prefixed with
- with a `*' have been modified. An argument of N says to list only
- the last N lines. Options, if supplied, have the following
- meanings:
+`set'
+ set [--abefhkmnptuvxBCEHPT] [-o OPTION] [ARGUMENT ...]
+ set [+abefhkmnptuvxBCEHPT] [+o OPTION] [ARGUMENT ...]
- `-w'
- Write out the current history to the history file.
+ If no options or arguments are supplied, `set' displays the names
+ and values of all shell variables and functions, sorted according
+ to the current locale, in a format that may be reused as input for
+ setting or resetting the currently-set variables. Read-only
+ variables cannot be reset. In POSIX mode, only shell variables
+ are listed.
- `-r'
- Read the current history file and append its contents to the
- history list.
+ When options are supplied, they set or unset shell attributes.
+ Options, if specified, have the following meanings:
`-a'
- Append the new history lines (history lines entered since the
- beginning of the current Bash session) to the history file.
-
- `-n'
- Append the history lines not already read from the history
- file to the current history list. These are lines appended
- to the history file since the beginning of the current Bash
- session.
+ Mark variables and function which are modified or created for
+ export to the environment of subsequent commands.
- `-c'
- Clear the history list. This may be combined with the other
- options to replace the history list completely.
+ `-b'
+ Cause the status of terminated background jobs to be reported
+ immediately, rather than before printing the next primary
+ prompt.
- `-s'
- The ARGs are added to the end of the history list as a single
- entry.
+ `-e'
+ Exit immediately if a simple command (*note Simple
+ Commands::) exits with a non-zero status, unless the command
+ that fails is part of the command list immediately following
+ a `while' or `until' keyword, part of the test in an `if'
+ statement, part of a command executed in a `&&' or `||b' list,
+ any command in a pipeline but the last, or if the command's
+ return status is being inverted using `!'. Failing simple
+ commands that are part of shell functions or command lists
+ enclosed in braces or parentheses satisfying the above
+ conditions do not cause the shell to exit. A trap on `ERR',
+ if set, is executed before the shell exits.
- `-p'
- Perform history substitution on the ARGs and display the
- result on the standard output, without storing the results in
- the history list.
+ `-f'
+ Disable file name generation (globbing).
- When the `-w', `-r', `-a', or `-n' option is used, if FILENAME is
- given, then it is used as the history file. If not, then the
- value of the `HISTFILE' variable is used.
+ `-h'
+ Locate and remember (hash) commands as they are looked up for
+ execution. This option is enabled by default.
-`logout'
- Exit a login shell.
+ `-k'
+ All arguments in the form of assignment statements are placed
+ in the environment for a command, not just those that precede
+ the command name.
-`source'
- A synonym for `.' (*note Bourne Shell Builtins::.).
+ `-m'
+ Job control is enabled (*note Job Control::).
-\1f
-File: bashref.info, Node: C Shell Variables, Prev: C Shell Builtins, Up: Csh Features
+ `-n'
+ Read commands but do not execute them; this may be used to
+ check a script for syntax errors. This option is ignored by
+ interactive shells.
-C Shell Variables
-=================
+ `-o OPTION-NAME'
+ Set the option corresponding to OPTION-NAME:
-`IGNOREEOF'
- If this variable is set, its value is used the number of
- consecutive `EOF's Bash will read before exiting. By default,
- Bash will exit upon reading a single `EOF'. If `IGNOREEOF' is not
- set to a numeric value, Bash acts as if its value were 10.
+ `allexport'
+ Same as `-a'.
-\1f
-File: bashref.info, Node: Korn Shell Features, Next: Bash Features, Prev: Csh Features, Up: Top
+ `braceexpand'
+ Same as `-B'.
-Korn Shell Style Features
-*************************
+ `emacs'
+ Use an `emacs'-style line editing interface (*note
+ Command Line Editing::). This also affects the editing
+ interface used for `read -e'.
- This section describes features primarily inspired by the Korn Shell
-(`ksh'). In some cases, the POSIX 1003.2 standard has adopted these
-commands and variables from the Korn Shell; Bash implements those
-features using the POSIX standard as a guide.
+ `errexit'
+ Same as `-e'.
-* Menu:
+ `errtrace'
+ Same as `-E'.
-* Korn Shell Constructs:: Shell grammar constructs adopted from the
- Korn Shell
-* Korn Shell Builtins:: Builtin commands adopted from the Korn Shell.
-* Korn Shell Variables:: Variables which Bash uses in essentially
- the same way as the Korn Shell.
-* Aliases:: Substituting one command for another.
+ `functrace'
+ Same as `-T'.
-\1f
-File: bashref.info, Node: Korn Shell Constructs, Next: Korn Shell Builtins, Up: Korn Shell Features
+ `hashall'
+ Same as `-h'.
-Korn Shell Constructs
-=====================
+ `histexpand'
+ Same as `-H'.
- Bash includes the Korn Shell `select' construct. This construct
-allows the easy generation of menus. It has almost the same syntax as
-the `for' command.
-
- The syntax of the `select' command is:
- select NAME [in WORDS ...]; do COMMANDS; done
-
- The list of words following `in' is expanded, generating a list of
-items. The set of expanded words is printed on the standard error,
-each preceded by a number. If the `in WORDS' is omitted, the
-positional parameters are printed. The `PS3' prompt is then displayed
-and a line is read from the standard input. If the line consists of a
-number corresponding to one of the displayed words, then the value of
-NAME is set to that word. If the line is empty, the words and prompt
-are displayed again. If `EOF' is read, the `select' command completes.
-Any other value read causes NAME to be set to null. The line read is
-saved in the variable `REPLY'.
-
- The COMMANDS are executed after each selection until a `break' or
-`return' command is executed, at which point the `select' command
-completes.
-
- Bash also has adopted command timing from the Korn shell. If the
-`time' reserved word precedes a pipeline, which may consist of a single
-command, timing statistics for the pipeline are displayed when it
-completes. The statistics currently consist of elapsed (wall-clock)
-time and user and system time consumed by the command's execution.
-
- The use of `time' as a reserved word permits the timing of shell
-builtins, shell functions, and pipelines. An external `time' command
-cannot time these easily.
+ `history'
+ Enable command history, as described in *note Bash
+ History Facilities::. This option is on by default in
+ interactive shells.
-\1f
-File: bashref.info, Node: Korn Shell Builtins, Next: Korn Shell Variables, Prev: Korn Shell Constructs, Up: Korn Shell Features
+ `ignoreeof'
+ An interactive shell will not exit upon reading EOF.
-Korn Shell Builtins
-===================
+ `keyword'
+ Same as `-k'.
- This section describes Bash builtin commands taken from `ksh'.
+ `monitor'
+ Same as `-m'.
-`fc'
- `fc [-e ENAME] [-nlr] [FIRST] [LAST]'
- `fc -s [PAT=REP] [COMMAND]'
+ `noclobber'
+ Same as `-C'.
- Fix Command. In the first form, a range of commands from FIRST to
- LAST is selected from the history list. Both FIRST and LAST may
- be specified as a string (to locate the most recent command
- beginning with that string) or as a number (an index into the
- history list, where a negative number is used as an offset from the
- current command number). If LAST is not specified it is set to
- FIRST. If FIRST is not specified it is set to the previous
- command for editing and -16 for listing. If the `-l' flag is
- given, the commands are listed on standard output. The `-n' flag
- suppresses the command numbers when listing. The `-r' flag
- reverses the order of the listing. Otherwise, the editor given by
- ENAME is invoked on a file containing those commands. If ENAME is
- not given, the value of the following variable expansion is used:
- `${FCEDIT:-${EDITOR:-vi}}'. This says to use the value of the
- `FCEDIT' variable if set, or the value of the `EDITOR' variable if
- that is set, or `vi' if neither is set. When editing is complete,
- the edited commands are echoed and executed.
+ `noexec'
+ Same as `-n'.
- In the second form, COMMAND is re-executed after each instance of
- PAT in the selected command is replaced by REP.
+ `noglob'
+ Same as `-f'.
- A useful alias to use with the `fc' command is `r='fc -s'', so
- that typing `r cc' runs the last command beginning with `cc' and
- typing `r' re-executes the last command (*note Aliases::.).
+ `nolog'
+ Currently ignored.
-`let'
- The `let' builtin allows arithmetic to be performed on shell
- variables. For details, refer to *Note Arithmetic Builtins::.
+ `notify'
+ Same as `-b'.
-`typeset'
- The `typeset' command is supplied for compatibility with the Korn
- shell; however, it has been deprecated in favor of the `declare'
- command (*note Bash Builtins::.).
+ `nounset'
+ Same as `-u'.
-\1f
-File: bashref.info, Node: Korn Shell Variables, Next: Aliases, Prev: Korn Shell Builtins, Up: Korn Shell Features
+ `onecmd'
+ Same as `-t'.
-Korn Shell Variables
-====================
+ `physical'
+ Same as `-P'.
-`REPLY'
- The default variable for the `read' builtin.
+ `pipefail'
+ If set, the return value of a pipeline is the value of
+ the last (rightmost) command to exit with a non-zero
+ status, or zero if all commands in the pipeline exit
+ successfully. This option is disabled by default.
-`RANDOM'
- Each time this parameter is referenced, a random integer between 0
- and 32767 is generated. Assigning a value to this variable seeds
- the random number generator.
+ `posix'
+ Change the behavior of Bash where the default operation
+ differs from the POSIX standard to match the standard
+ (*note Bash POSIX Mode::). This is intended to make
+ Bash behave as a strict superset of that standard.
-`SECONDS'
- This variable expands to the number of seconds since the shell was
- started. Assignment to this variable resets the count to the
- value assigned, and the expanded value becomes the value assigned
- plus the number of seconds since the assignment.
+ `privileged'
+ Same as `-p'.
-`PS3'
- The value of this variable is used as the prompt for the `select'
- command. If this variable is not set, the `select' command
- prompts with `#? '
+ `verbose'
+ Same as `-v'.
-`PS4'
- This is the prompt printed before the command line is echoed when
- the `-x' option is set (*note The Set Builtin::.). The default is
- `+ '.
+ `vi'
+ Use a `vi'-style line editing interface. This also
+ affects the editing interface used for `read -e'.
-`PWD'
- The current working directory as set by the `cd' builtin.
+ `xtrace'
+ Same as `-x'.
-`OLDPWD'
- The previous working directory as set by the `cd' builtin.
+ `-p'
+ Turn on privileged mode. In this mode, the `$BASH_ENV' and
+ `$ENV' files are not processed, shell functions are not
+ inherited from the environment, and the `SHELLOPTS', `CDPATH'
+ and `GLOBIGNORE' variables, if they appear in the
+ environment, are ignored. If the shell is started with the
+ effective user (group) id not equal to the real user (group)
+ id, and the `-p' option is not supplied, these actions are
+ taken and the effective user id is set to the real user id.
+ If the `-p' option is supplied at startup, the effective user
+ id is not reset. Turning this option off causes the
+ effective user and group ids to be set to the real user and
+ group ids.
-`TMOUT'
- If set to a value greater than zero, the value is interpreted as
- the number of seconds to wait for input after issuing the primary
- prompt. Bash terminates after that number of seconds if input does
- not arrive.
+ `-t'
+ Exit after reading and executing one command.
-`LINENO'
- The line number in the script or shell function currently
- executing.
+ `-u'
+ Treat unset variables as an error when performing parameter
+ expansion. An error message will be written to the standard
+ error, and a non-interactive shell will exit.
-`FCEDIT'
- The editor used as a default by the `fc' builtin command.
+ `-v'
+ Print shell input lines as they are read.
-\1f
-File: bashref.info, Node: Aliases, Prev: Korn Shell Variables, Up: Korn Shell Features
+ `-x'
+ Print a trace of simple commands, `for' commands, `case'
+ commands, `select' commands, and arithmetic `for' commands
+ and their arguments or associated word lists after they are
+ expanded and before they are executed. The value of the `PS4'
+ variable is expanded and the resultant value is printed before
+ the command and its expanded arguments.
-Aliases
-=======
+ `-B'
+ The shell will perform brace expansion (*note Brace
+ Expansion::). This option is on by default.
-* Menu:
+ `-C'
+ Prevent output redirection using `>', `>&', and `<>' from
+ overwriting existing files.
-* Alias Builtins:: Builtins commands to maniuplate aliases.
+ `-E'
+ If set, any trap on `ERR' is inherited by shell functions,
+ command substitutions, and commands executed in a subshell
+ environment. The `ERR' trap is normally not inherited in
+ such cases.
- The shell maintains a list of ALIASES that may be set and unset with
-the `alias' and `unalias' builtin commands.
+ `-H'
+ Enable `!' style history substitution (*note History
+ Interaction::). This option is on by default for interactive
+ shells.
- The first word of each command, if unquoted, is checked to see if it
-has an alias. If so, that word is replaced by the text of the alias.
-The alias name and the replacement text may contain any valid shell
-input, including shell metacharacters, with the exception that the
-alias name may not contain =. The first word of the replacement text
-is tested for aliases, but a word that is identical to an alias being
-expanded is not expanded a second time. This means that one may alias
-`ls' to `"ls -F"', for instance, and Bash does not try to recursively
-expand the replacement text. If the last character of the alias value
-is a space or tab character, then the next command word following the
-alias is also checked for alias expansion.
-
- Aliases are created and listed with the `alias' command, and removed
-with the `unalias' command.
-
- There is no mechanism for using arguments in the replacement text,
-as in `csh'. If arguments are needed, a shell function should be used
-(*note Shell Functions::.).
-
- Aliases are not expanded when the shell is not interactive, unless
-the `expand_aliases' shell option is set using `shopt' (*note Bash
-Builtins::.).
+ `-P'
+ If set, do not follow symbolic links when performing commands
+ such as `cd' which change the current directory. The
+ physical directory is used instead. By default, Bash follows
+ the logical chain of directories when performing commands
+ which change the current directory.
- The rules concerning the definition and use of aliases are somewhat
-confusing. Bash always reads at least one complete line of input
-before executing any of the commands on that line. Aliases are
-expanded when a command is read, not when it is executed. Therefore, an
-alias definition appearing on the same line as another command does not
-take effect until the next line of input is read. The commands
-following the alias definition on that line are not affected by the new
-alias. This behavior is also an issue when functions are executed.
-Aliases are expanded when the function definition is read, not when the
-function is executed, because a function definition is itself a
-compound command. As a consequence, aliases defined in a function are
-not available until after that function is executed. To be safe,
-always put alias definitions on a separate line, and do not use `alias'
-in compound commands.
+ For example, if `/usr/sys' is a symbolic link to
+ `/usr/local/sys' then:
+ $ cd /usr/sys; echo $PWD
+ /usr/sys
+ $ cd ..; pwd
+ /usr
- Note that for almost every purpose, aliases are superseded by shell
-functions.
+ If `set -P' is on, then:
+ $ cd /usr/sys; echo $PWD
+ /usr/local/sys
+ $ cd ..; pwd
+ /usr/local
-\1f
-File: bashref.info, Node: Alias Builtins, Up: Aliases
+ `-T'
+ If set, any trap on `DEBUG' and `RETURN' are inherited by
+ shell functions, command substitutions, and commands executed
+ in a subshell environment. The `DEBUG' and `RETURN' traps
+ are normally not inherited in such cases.
-Alias Builtins
---------------
+ `--'
+ If no arguments follow this option, then the positional
+ parameters are unset. Otherwise, the positional parameters
+ are set to the ARGUMENTS, even if some of them begin with a
+ `-'.
-`alias'
- alias [`-p'] [NAME[=VALUE] ...]
+ `-'
+ Signal the end of options, cause all remaining ARGUMENTS to
+ be assigned to the positional parameters. The `-x' and `-v'
+ options are turned off. If there are no arguments, the
+ positional parameters remain unchanged.
- Without arguments or with the `-p' option, `alias' prints the list
- of aliases on the standard output in a form that allows them to be
- reused as input. If arguments are supplied, an alias is defined
- for each NAME whose VALUE is given. If no VALUE is given, the name
- and value of the alias is printed.
+ Using `+' rather than `-' causes these options to be turned off.
+ The options can also be used upon invocation of the shell. The
+ current set of options may be found in `$-'.
-`unalias'
- unalias [-a] [NAME ... ]
+ The remaining N ARGUMENTS are positional parameters and are
+ assigned, in order, to `$1', `$2', ... `$N'. The special
+ parameter `#' is set to N.
- Remove each NAME from the list of aliases. If `-a' is supplied,
- all aliases are removed.
+ The return status is always zero unless an invalid option is
+ supplied.
\1f
-File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Korn Shell Features, Up: Top
+File: bashref.info, Node: The Shopt Builtin, Prev: The Set Builtin, Up: Modifying Shell Behavior
-Bash Features
-*************
+4.3.2 The Shopt Builtin
+-----------------------
- This section describes features unique to Bash.
+This builtin allows you to change additional shell optional behavior.
-* Menu:
+`shopt'
+ shopt [-pqsu] [-o] [OPTNAME ...]
+ Toggle the values of variables controlling optional shell behavior.
+ With no options, or with the `-p' option, a list of all settable
+ options is displayed, with an indication of whether or not each is
+ set. The `-p' option causes output to be displayed in a form that
+ may be reused as input. Other options have the following meanings:
-* Invoking Bash:: Command line options that you can give
- to Bash.
-* Bash Startup Files:: When and how Bash executes scripts.
-* Is This Shell Interactive?:: Determining the state of a running Bash.
-* Bash Builtins:: Table of builtins specific to Bash.
-* The Set Builtin:: This builtin is so overloaded it
- deserves its own section.
-* Bash Conditional Expressions:: Primitives used in composing expressions for
- the `test' builtin.
-* Bash Variables:: List of variables that exist in Bash.
-* Shell Arithmetic:: Arithmetic on shell variables.
-* Arrays:: Array Variables
-* Printing a Prompt:: Controlling the PS1 string.
-* The Restricted Shell:: A more controlled mode of shell execution.
-* Bash POSIX Mode:: Making Bash behave more closely to what
- the POSIX standard specifies.
+ `-s'
+ Enable (set) each OPTNAME.
-\1f
-File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
+ `-u'
+ Disable (unset) each OPTNAME.
-Invoking Bash
-=============
+ `-q'
+ Suppresses normal output; the return status indicates whether
+ the OPTNAME is set or unset. If multiple OPTNAME arguments
+ are given with `-q', the return status is zero if all
+ OPTNAMES are enabled; non-zero otherwise.
- bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION] [ARGUMENT ...]
- bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION] -c STRING [ARGUMENT ...]
- bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION] [ARGUMENT ...]
+ `-o'
+ Restricts the values of OPTNAME to be those defined for the
+ `-o' option to the `set' builtin (*note The Set Builtin::).
- In addition to the single-character shell command-line options
-(*note The Set Builtin::.), there are several multi-character options
-that you can use. These options must appear on the command line before
-the single-character options in order for them to be recognized.
+ If either `-s' or `-u' is used with no OPTNAME arguments, the
+ display is limited to those options which are set or unset,
+ respectively.
-`--dump-strings'
- Equivalent to `-D'.
+ Unless otherwise noted, the `shopt' options are disabled (off) by
+ default.
-`--help'
- Display a usage message on standard output and exit sucessfully.
+ The return status when listing options is zero if all OPTNAMES are
+ enabled, non-zero otherwise. When setting or unsetting options,
+ the return status is zero unless an OPTNAME is not a valid shell
+ option.
-`--login'
- Make this shell act as if it were directly invoked by login. This
- is equivalent to `exec -l bash' but can be issued from another
- shell, such as `csh'. If you wanted to replace your current login
- shell with a Bash login shell, you would say `exec bash --login'.
+ The list of `shopt' options is:
+ `autocd'
+ If set, a command name that is the name of a directory is
+ executed as if it were the argument to the `cd' command.
+ This option is only used by interactive shells.
-`--noediting'
- Do not use the GNU Readline library (*note Command Line Editing::.)
- to read interactive command lines.
+ `cdable_vars'
+ If this is set, an argument to the `cd' builtin command that
+ is not a directory is assumed to be the name of a variable
+ whose value is the directory to change to.
-`--noprofile'
- Don't load the system-wide startup file `/etc/profile' or any of
- the personal initialization files `~/.bash_profile',
- `~/.bash_login', or `~/.profile' when Bash is invoked as a login
- shell.
+ `cdspell'
+ If set, minor errors in the spelling of a directory component
+ in a `cd' command will be corrected. The errors checked for
+ are transposed characters, a missing character, and a
+ character too many. If a correction is found, the corrected
+ path is printed, and the command proceeds. This option is
+ only used by interactive shells.
-`--norc'
- Don't read the `~/.bashrc' initialization file in an interactive
- shell. This is on by default if the shell is invoked as `sh'.
+ `checkhash'
+ If this is set, Bash checks that a command found in the hash
+ table exists before trying to execute it. If a hashed
+ command no longer exists, a normal path search is performed.
-`--posix'
- Change the behavior of Bash where the default operation differs
- from the POSIX 1003.2 standard to match the standard. This is
- intended to make Bash behave as a strict superset of that
- standard. *Note Bash POSIX Mode::, for a description of the Bash
- POSIX mode.
+ `checkjobs'
+ If set, Bash lists the status of any stopped and running jobs
+ before exiting an interactive shell. If any jobs are
+ running, this causes the exit to be deferred until a second
+ exit is attempted without an intervening command (*note Job
+ Control::). The shell always postpones exiting if any jobs
+ are stopped.
-`--rcfile FILENAME'
- Execute commands from FILENAME (instead of `~/.bashrc') in an
- interactive shell.
+ `checkwinsize'
+ If set, Bash checks the window size after each command and,
+ if necessary, updates the values of `LINES' and `COLUMNS'.
-`--restricted'
- Make the shell a restricted shell (*note The Restricted Shell::.).
+ `cmdhist'
+ If set, Bash attempts to save all lines of a multiple-line
+ command in the same history entry. This allows easy
+ re-editing of multi-line commands.
-`--verbose'
- Equivalent to `-v'.
+ `compat31'
+ If set, Bash changes its behavior to that of version 3.1 with
+ respect to quoted arguments to the conditional command's =~
+ operator.
-`--version'
- Show version information for this instance of Bash on the standard
- output and exit successfully.
+ `dirspell'
+ If set, Bash attempts spelling correction on directory names
+ during word completion if the directory name initially
+ supplied does not exist.
- There are several single-character options you can give which are
-not available with the `set' builtin.
+ `dotglob'
+ If set, Bash includes filenames beginning with a `.' in the
+ results of filename expansion.
-`-c STRING'
- Read and execute commands from STRING after processing the
- options, then exit. Any remaining arguments are assigned to the
- positional parameters, starting with `$0'.
+ `execfail'
+ If this is set, a non-interactive shell will not exit if it
+ cannot execute the file specified as an argument to the `exec'
+ builtin command. An interactive shell does not exit if `exec'
+ fails.
-`-i'
- Force the shell to run interactively.
+ `expand_aliases'
+ If set, aliases are expanded as described below under Aliases,
+ *note Aliases::. This option is enabled by default for
+ interactive shells.
-`-r'
- Make the shell restricted.
+ `extdebug'
+ If set, behavior intended for use by debuggers is enabled:
-`-s'
- If this flag is present, or if no arguments remain after option
- processing, then commands are read from the standard input. This
- option allows the positional parameters to be set when invoking an
- interactive shell.
+ 1. The `-F' option to the `declare' builtin (*note Bash
+ Builtins::) displays the source file name and line
+ number corresponding to each function name supplied as
+ an argument.
-`-D'
- A list of all double-quoted strings preceded by `$' is printed on
- the standard ouput. These are the strings that are subject to
- language translation when the current locale is not `C' or `POSIX'
- (*note Locale Translation::.). This implies the `-n' option; no
- commands will be executed.
+ 2. If the command run by the `DEBUG' trap returns a
+ non-zero value, the next command is skipped and not
+ executed.
- An *interactive* shell is one whose input and output are both
-connected to terminals (as determined by `isatty()'), or one started
-with the `-i' option.
+ 3. If the command run by the `DEBUG' trap returns a value
+ of 2, and the shell is executing in a subroutine (a
+ shell function or a shell script executed by the `.' or
+ `source' builtins), a call to `return' is simulated.
- If arguments remain after option processing, and neither the `-c'
-nor the `-s' option has been supplied, the first argument is assumed to
-be the name of a file containing shell commands (*note Shell
-Scripts::.). When Bash is invoked in this fashion, `$0' is set to the
-name of the file, and the positional parameters are set to the
-remaining arguments. Bash reads and executes commands from this file,
-then exits. Bash's exit status is the exit status of the last command
-executed in the script. If no commands are executed, the exit status
-is 0.
+ 4. `BASH_ARGC' and `BASH_ARGV' are updated as described in
+ their descriptions (*note Bash Variables::).
-\1f
-File: bashref.info, Node: Bash Startup Files, Next: Is This Shell Interactive?, Prev: Invoking Bash, Up: Bash Features
+ 5. Function tracing is enabled: command substitution,
+ shell functions, and subshells invoked with `( COMMAND
+ )' inherit the `DEBUG' and `RETURN' traps.
-Bash Startup Files
-==================
+ 6. Error tracing is enabled: command substitution, shell
+ functions, and subshells invoked with `( COMMAND )'
+ inherit the `ERROR' trap.
- This section describs how Bash executes its startup files. If any
-of the files exist but cannot be read, Bash reports an error. Tildes
-are expanded in file names as described above under Tilde Expansion
-(*note Tilde Expansion::.).
+ `extglob'
+ If set, the extended pattern matching features described above
+ (*note Pattern Matching::) are enabled.
- When Bash is invoked as an interactive login shell, it first reads
-and executes commands from the file `/etc/profile', if that file exists.
-After reading that file, it looks for `~/.bash_profile',
-`~/.bash_login', and `~/.profile', in that order, and reads and
-executes commands from the first one that exists and is readable. The
-`--noprofile' option may be used when the shell is started to inhibit
-this behavior.
+ `extquote'
+ If set, `$'STRING'' and `$"STRING"' quoting is performed
+ within `${PARAMETER}' expansions enclosed in double quotes.
+ This option is enabled by default.
- When a login shell exits, Bash reads and executes commands from the
-file `~/.bash_logout', if it exists.
+ `failglob'
+ If set, patterns which fail to match filenames during
+ pathname expansion result in an expansion error.
- When an interactive shell that is not a login shell is started, Bash
-reads and executes commands from `~/.bashrc', if that file exists.
-This may be inhibited by using the `--norc' option. The `--rcfile
-FILE' option will force Bash to read and execute commands from FILE
-instead of `~/.bashrc'.
+ `force_fignore'
+ If set, the suffixes specified by the `FIGNORE' shell variable
+ cause words to be ignored when performing word completion
+ even if the ignored words are the only possible completions.
+ *Note Bash Variables::, for a description of `FIGNORE'. This
+ option is enabled by default.
- So, typically, your `~/.bash_profile' contains the line
- `if [ -f `~/.bashrc' ]; then . `~/.bashrc'; fi'
+ `globstar'
+ If set, the pattern `**' used in a filename expansion context
+ will match a files and zero or more directories and
+ subdirectories. If the pattern is followed by a `/', only
+ directories and subdirectories match.
-after (or before) any login-specific initializations.
+ `gnu_errfmt'
+ If set, shell error messages are written in the standard GNU
+ error message format.
- When Bash is started non-interactively, to run a shell script, for
-example, it looks for the variable `BASH_ENV' in the environment,
-expands its value if it appears there, and uses the expanded value as
-the name of a file to read and execute. Bash behaves as if the
-following command were executed:
- `if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi'
+ `histappend'
+ If set, the history list is appended to the file named by the
+ value of the `HISTFILE' variable when the shell exits, rather
+ than overwriting the file.
-but the value of the `PATH' variable is not used to search for the file
-name.
+ `histreedit'
+ If set, and Readline is being used, a user is given the
+ opportunity to re-edit a failed history substitution.
- If Bash is invoked with the name `sh', it tries to mimic the startup
-behavior of historical versions of `sh' as closely as possible, while
-conforming to the POSIX standard as well.
+ `histverify'
+ If set, and Readline is being used, the results of history
+ substitution are not immediately passed to the shell parser.
+ Instead, the resulting line is loaded into the Readline
+ editing buffer, allowing further modification.
- When invoked as a login shell, it first attempts to read and execute
-commands from `/etc/profile' and `~/.profile', in that order. The
-`--noprofile' option may be used to inhibit this behavior. When
-invoked as an interactive shell with the name `sh', `bash' looks for
-the variable `ENV', expands its value if it is defined, and uses the
-expanded value as the name of a file to read and execute. Since a
-shell invoked as `sh' does not attempt to read and execute commands
-from any other startup files, the `--rcfile' option has no effect. A
-non-interactive shell invoked with the name `sh' does not attempt to
-read any startup files.
+ `hostcomplete'
+ If set, and Readline is being used, Bash will attempt to
+ perform hostname completion when a word containing a `@' is
+ being completed (*note Commands For Completion::). This
+ option is enabled by default.
- When invoked as `sh', Bash enters POSIX mode after the startup files
-are read.
+ `huponexit'
+ If set, Bash will send `SIGHUP' to all jobs when an
+ interactive login shell exits (*note Signals::).
- When Bash is started in POSIX mode, as with the `--posix' command
-line option, it follows the POSIX standard for startup files. In this
-mode, the `ENV' variable is expanded and commands are read and executed
-from the file whose name is the expanded value. No other startup files
-are read. This is done by interactive shells only.
+ `interactive_comments'
+ Allow a word beginning with `#' to cause that word and all
+ remaining characters on that line to be ignored in an
+ interactive shell. This option is enabled by default.
- Bash attempts to determine when it is being run by the remote shell
-daemon, usually `rshd'. If Bash determines it is being run by rshd, it
-reads and executes commands from `~/.bashrc', if that file exists and
-is readable. It will not do this if invoked as `sh'. The `--norc'
-option may be used to inhibit this behavior, and the `--rcfile' option
-may be used to force another file to be read, but rshd does not
-generally invoke the shell with those options or allow them to be
-specified.
+ `lithist'
+ If enabled, and the `cmdhist' option is enabled, multi-line
+ commands are saved to the history with embedded newlines
+ rather than using semicolon separators where possible.
-\1f
-File: bashref.info, Node: Is This Shell Interactive?, Next: Bash Builtins, Prev: Bash Startup Files, Up: Bash Features
+ `login_shell'
+ The shell sets this option if it is started as a login shell
+ (*note Invoking Bash::). The value may not be changed.
-Is This Shell Interactive?
-==========================
+ `mailwarn'
+ If set, and a file that Bash is checking for mail has been
+ accessed since the last time it was checked, the message
+ `"The mail in MAILFILE has been read"' is displayed.
- As defined in *Note Invoking Bash::, an interactive shell is one
-whose input and output are both connected to terminals (as determined
-by `isatty(3)'), or one started with the `-i' option.
+ `no_empty_cmd_completion'
+ If set, and Readline is being used, Bash will not attempt to
+ search the `PATH' for possible completions when completion is
+ attempted on an empty line.
- You may wish to determine within a startup script whether Bash is
-running interactively or not. To do this, examine the variable `$PS1';
-it is unset in non-interactive shells, and set in interactive shells.
-Thus:
+ `nocaseglob'
+ If set, Bash matches filenames in a case-insensitive fashion
+ when performing filename expansion.
- if [ -z "$PS1" ]; then
- echo This shell is not interactive
- else
- echo This shell is interactive
- fi
+ `nocasematch'
+ If set, Bash matches patterns in a case-insensitive fashion
+ when performing matching while executing `case' or `[['
+ conditional commands.
- Alternatively, you may test the value of the `-' special parameter.
-It contains `i' when the shell is interactive. For example:
+ `nullglob'
+ If set, Bash allows filename patterns which match no files to
+ expand to a null string, rather than themselves.
- case "$-" in
- *i*) echo This shell is interactive ;;
- *) echo This shell is not interactive ;;
- esac
+ `progcomp'
+ If set, the programmable completion facilities (*note
+ Programmable Completion::) are enabled. This option is
+ enabled by default.
-\1f
-File: bashref.info, Node: Bash Builtins, Next: The Set Builtin, Prev: Is This Shell Interactive?, Up: Bash Features
+ `promptvars'
+ If set, prompt strings undergo parameter expansion, command
+ substitution, arithmetic expansion, and quote removal after
+ being expanded as described below (*note Printing a Prompt::).
+ This option is enabled by default.
-Bash Builtin Commands
-=====================
+ `restricted_shell'
+ The shell sets this option if it is started in restricted mode
+ (*note The Restricted Shell::). The value may not be changed.
+ This is not reset when the startup files are executed,
+ allowing the startup files to discover whether or not a shell
+ is restricted.
- This section describes builtin commands which are unique to or have
-been extended in Bash.
+ `shift_verbose'
+ If this is set, the `shift' builtin prints an error message
+ when the shift count exceeds the number of positional
+ parameters.
-`bind'
- bind [-m KEYMAP] [-lpsvPSV] [-q NAME] [-r KEYSEQ]
- bind [-m KEYMAP] -f FILENAME
- bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
+ `sourcepath'
+ If set, the `source' builtin uses the value of `PATH' to find
+ the directory containing the file supplied as an argument.
+ This option is enabled by default.
- Display current Readline (*note Command Line Editing::.) key and
- function bindings, or bind a key sequence to a Readline function
- or macro. The binding syntax accepted is identical to that of
- `.inputrc' (*note Readline Init File::.), but each binding must be
- passed as a separate argument: e.g.,
- `"\C-x\C-r":re-read-init-file'. Options, if supplied, have the
- following meanings:
+ `xpg_echo'
+ If set, the `echo' builtin expands backslash-escape sequences
+ by default.
- `-m KEYMAP'
- Use KEYMAP as the keymap to be affected by the subsequent
- bindings. Acceptable KEYMAP names are `emacs',
- `emacs-standard', `emacs-meta', `emacs-ctlx', `vi',
- `vi-command', and `vi-insert'. `vi' is equivalent to
- `vi-command'; `emacs' is equivalent to `emacs-standard'.
- `-l'
- List the names of all Readline functions
+ The return status when listing options is zero if all OPTNAMES are
+ enabled, non-zero otherwise. When setting or unsetting options,
+ the return status is zero unless an OPTNAME is not a valid shell
+ option.
- `-p'
- Display Readline function names and bindings in such a way
- that they can be re-read
- `-P'
- List current Readline function names and bindings
+\1f
+File: bashref.info, Node: Special Builtins, Prev: Modifying Shell Behavior, Up: Shell Builtin Commands
- `-v'
- Display Readline variable names and values in such a way that
- they can be re-read
+4.4 Special Builtins
+====================
- `-V'
- List current Readline variable names and values
+For historical reasons, the POSIX standard has classified several
+builtin commands as _special_. When Bash is executing in POSIX mode,
+the special builtins differ from other builtin commands in three
+respects:
- `-s'
- Display Readline key sequences bound to macros and the
- strings they output in such a way that they can be re-read
+ 1. Special builtins are found before shell functions during command
+ lookup.
- `-S'
- Display Readline key sequences bound to macros and the
- strings they output
+ 2. If a special builtin returns an error status, a non-interactive
+ shell exits.
- `-f FILENAME'
- Read key bindings from FILENAME
+ 3. Assignment statements preceding the command stay in effect in the
+ shell environment after the command completes.
- `-q'
- Query about which keys invoke the named FUNCTION
+ When Bash is not executing in POSIX mode, these builtins behave no
+differently than the rest of the Bash builtin commands. The Bash POSIX
+mode is described in *note Bash POSIX Mode::.
- `-r KEYSEQ'
- Remove any current binding for KEYSEQ
+ These are the POSIX special builtins:
+ break : . continue eval exec exit export readonly return set
+ shift trap unset
-`builtin'
- builtin [SHELL-BUILTIN [ARGS]]
- Run a shell builtin. This is useful when you wish to define a
- shell function with the same name as a shell builtin, but need the
- functionality of the builtin within the function itself.
+\1f
+File: bashref.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
-`command'
- command [-pVv] COMMAND [ARGS ...]
- Runs COMMAND with ARG ignoring shell functions. If you have a
- shell function called `ls', and you wish to call the command `ls',
- you can say `command ls'. The `-p' option means to use a default
- value for `$PATH' that is guaranteed to find all of the standard
- utilities.
+5 Shell Variables
+*****************
- If either the `-V' or `-v' option is supplied, a description of
- COMMAND is printed. The `-v' option causes a single word
- indicating the command or file name used to invoke COMMAND to be
- printed; the `-V' option produces a more verbose description.
+* Menu:
-`declare'
- declare [-afFrxi] [-p] [NAME[=VALUE]]
+* Bourne Shell Variables:: Variables which Bash uses in the same way
+ as the Bourne Shell.
+* Bash Variables:: List of variables that exist in Bash.
- Declare variables and give them attributes. If no NAMEs are
- given, then display the values of variables instead.
+ This chapter describes the shell variables that Bash uses. Bash
+automatically assigns default values to a number of variables.
- The `-p' option will display the attributes and values of each
- NAME. When `-p' is used, additional options are ignored. The
- `-F' option inhibits the display of function definitions; only the
- function name and attributes are printed. `-F' implies `-f'. The
- following options can be used to restrict output to variables with
- the specified attributes or to give variables attributes:
+\1f
+File: bashref.info, Node: Bourne Shell Variables, Next: Bash Variables, Up: Shell Variables
- `-a'
- Each NAME is an array variable (*note Arrays::.).
+5.1 Bourne Shell Variables
+==========================
- `-f'
- Use function names only.
+Bash uses certain shell variables in the same way as the Bourne shell.
+In some cases, Bash assigns a default value to the variable.
- `-i'
- The variable is to be treated as an integer; arithmetic
- evaluation (*note Shell Arithmetic::.) is performed when the
- variable is assigned a value.
+`CDPATH'
+ A colon-separated list of directories used as a search path for
+ the `cd' builtin command.
- `-r'
- Make NAMEs readonly. These names cannot then be assigned
- values by subsequent assignment statements.
+`HOME'
+ The current user's home directory; the default for the `cd' builtin
+ command. The value of this variable is also used by tilde
+ expansion (*note Tilde Expansion::).
- `-x'
- Mark each NAME for export to subsequent commands via the
- environment.
+`IFS'
+ A list of characters that separate fields; used when the shell
+ splits words as part of expansion.
- Using `+' instead of `-' turns off the attribute instead. When
- used in a function, `declare' makes each NAME local, as with the
- `local' command.
+`MAIL'
+ If this parameter is set to a filename and the `MAILPATH' variable
+ is not set, Bash informs the user of the arrival of mail in the
+ specified file.
-`echo'
- echo [-neE] [arg ...]
- Output the `arg's, separated by spaces, terminated with a newline.
- The return status is always 0. If `-n' is specified, the
- trailing newline is suppressed. If the `-e' option is given,
- interpretation of the following backslash-escaped characters is
- enabled. The `-E' option disables the interpretation of these
- escape characters, even on systems where they are interpreted by
- default. `echo' interprets the following escape sequences:
- `\a'
- alert (bell)
+`MAILPATH'
+ A colon-separated list of filenames which the shell periodically
+ checks for new mail. Each list entry can specify the message that
+ is printed when new mail arrives in the mail file by separating
+ the file name from the message with a `?'. When used in the text
+ of the message, `$_' expands to the name of the current mail file.
- `\b'
- backspace
+`OPTARG'
+ The value of the last option argument processed by the `getopts'
+ builtin.
- `\c'
- suppress trailing newline
+`OPTIND'
+ The index of the last option argument processed by the `getopts'
+ builtin.
- `\e'
- escape
+`PATH'
+ A colon-separated list of directories in which the shell looks for
+ commands. A zero-length (null) directory name in the value of
+ `PATH' indicates the current directory. A null directory name may
+ appear as two adjacent colons, or as an initial or trailing colon.
- `\f'
- form feed
+`PS1'
+ The primary prompt string. The default value is `\s-\v\$ '.
+ *Note Printing a Prompt::, for the complete list of escape
+ sequences that are expanded before `PS1' is displayed.
- `\n'
- new line
+`PS2'
+ The secondary prompt string. The default value is `> '.
- `\r'
- carriage return
- `\t'
- horizontal tab
+\1f
+File: bashref.info, Node: Bash Variables, Prev: Bourne Shell Variables, Up: Shell Variables
- `\v'
- vertical tab
+5.2 Bash Variables
+==================
- `\\'
- backslash
+These variables are set or used by Bash, but other shells do not
+normally treat them specially.
- `\nnn'
- the character whose ASCII code is `nnn' (octal)
+ A few variables used by Bash are described in different chapters:
+variables for controlling the job control facilities (*note Job Control
+Variables::).
-`enable'
- enable [-n] [-p] [-f FILENAME] [-ads] [NAME ...]
- Enable and disable builtin shell commands. This allows you to use
- a disk command which has the same name as a shell builtin. If
- `-n' is used, the NAMEs become disabled. Otherwise NAMEs are
- enabled. For example, to use the `test' binary found via `$PATH'
- instead of the shell builtin version, type `enable -n test'.
+`BASH'
+ The full pathname used to execute the current instance of Bash.
+
+`BASHPID'
+ Expands to the process id of the current Bash process. This
+ differs from `$$' under certain circumstances, such as subshells
+ that do not require Bash to be re-initialized.
+
+`BASH_ALIASES'
+ An associative array variable whose members correspond to the
+ internal list of aliases as maintained by the `alias' builtin
+ (*note Bourne Shell Builtins::). Elements added to this array
+ appear in the alias list; unsetting array elements cause aliases
+ to be removed from the alias list.
+
+`BASH_ARGC'
+ An array variable whose values are the number of parameters in each
+ frame of the current bash execution call stack. The number of
+ parameters to the current subroutine (shell function or script
+ executed with `.' or `source') is at the top of the stack. When a
+ subroutine is executed, the number of parameters passed is pushed
+ onto `BASH_ARGC'. The shell sets `BASH_ARGC' only when in
+ extended debugging mode (see *note The Shopt Builtin:: for a
+ description of the `extdebug' option to the `shopt' builtin).
+
+`BASH_ARGV'
+ An array variable containing all of the parameters in the current
+ bash execution call stack. The final parameter of the last
+ subroutine call is at the top of the stack; the first parameter of
+ the initial call is at the bottom. When a subroutine is executed,
+ the parameters supplied are pushed onto `BASH_ARGV'. The shell
+ sets `BASH_ARGV' only when in extended debugging mode (see *note
+ The Shopt Builtin:: for a description of the `extdebug' option to
+ the `shopt' builtin).
+
+`BASH_CMDS'
+ An associative array variable whose members correspond to the
+ internal hash table of commands as maintained by the `hash' builtin
+ (*note Bourne Shell Builtins::). Elements added to this array
+ appear in the hash table; unsetting array elements cause commands
+ to be removed from the hash table.
+
+`BASH_COMMAND'
+ The command currently being executed or about to be executed,
+ unless the shell is executing a command as the result of a trap,
+ in which case it is the command executing at the time of the trap.
- If the `-p' option is supplied, or no NAME arguments appear, a
- list of shell builtins is printed. With no other arguments, the
- list consists of all enabled shell builtins. The `-a' option
- means to list each builtin with an indication of whether or not it
- is enabled.
+`BASH_ENV'
+ If this variable is set when Bash is invoked to execute a shell
+ script, its value is expanded and used as the name of a startup
+ file to read before executing the script. *Note Bash Startup
+ Files::.
- The `-f' option means to load the new builtin command NAME from
- shared object FILENAME, on systems that support dynamic loading.
- The `-d' option will delete a builtin loaded with `-f'. If there
- are no options, a list of the shell builtins is displayed. The
- `-s' option restricts `enable' to the POSIX.2 special builtins.
- If `-s' is used with `-f', the new builtin becomes a special
- builtin.
+`BASH_EXECUTION_STRING'
+ The command argument to the `-c' invocation option.
+
+`BASH_LINENO'
+ An array variable whose members are the line numbers in source
+ files corresponding to each member of FUNCNAME.
+ `${BASH_LINENO[$i]}' is the line number in the source file where
+ `${FUNCNAME[$i]}' was called (or `${BASH_LINENO[$i-1]}' if
+ referenced within another shell function). The corresponding
+ source file name is `${BASH_SOURCE[$i]}'. Use `LINENO' to obtain
+ the current line number.
+
+`BASH_REMATCH'
+ An array variable whose members are assigned by the `=~' binary
+ operator to the `[[' conditional command (*note Conditional
+ Constructs::). The element with index 0 is the portion of the
+ string matching the entire regular expression. The element with
+ index N is the portion of the string matching the Nth
+ parenthesized subexpression. This variable is read-only.
+
+`BASH_SOURCE'
+ An array variable whose members are the source filenames
+ corresponding to the elements in the `FUNCNAME' array variable.
+
+`BASH_SUBSHELL'
+ Incremented by one each time a subshell or subshell environment is
+ spawned. The initial value is 0.
-`help'
- help [PATTERN]
- Display helpful information about builtin commands. If PATTERN is
- specified, `help' gives detailed help on all commands matching
- PATTERN, otherwise a list of the builtins is printed.
+`BASH_VERSINFO'
+ A readonly array variable (*note Arrays::) whose members hold
+ version information for this instance of Bash. The values
+ assigned to the array members are as follows:
-`local'
- local NAME[=VALUE]
- For each argument, create a local variable called NAME, and give
- it VALUE. `local' can only be used within a function; it makes
- the variable NAME have a visible scope restricted to that function
- and its children.
+ `BASH_VERSINFO[0]'
+ The major version number (the RELEASE).
-`logout'
- logout [N]
- Exit a login shell, returning a status of N to the shell's parent.
+ `BASH_VERSINFO[1]'
+ The minor version number (the VERSION).
-`read'
- read [-a ANAME] [-p PROMPT] [-er] [NAME ...]
- One line is read from the standard input, and the first word is
- assigned to the first NAME, the second word to the second NAME,
- and so on, with leftover words assigned to the last NAME. Only
- the characters in the value of the `IFS' variable are recognized
- as word delimiters. If no names are supplied, the line read is
- assigned to the variable `REPLY'. The return code is zero, unless
- end-of-file is encountered. Options, if supplied, have the
- following meanings:
+ `BASH_VERSINFO[2]'
+ The patch level.
- `-r'
- If this option is given, a backslash-newline pair is not
- ignored, and the backslash is considered to be part of the
- line.
+ `BASH_VERSINFO[3]'
+ The build version.
- `-p PROMPT'
- Display `prompt', without a trailing newline, before
- attempting to read any input. The prompt is displayed only
- if input is coming from a terminal.
+ `BASH_VERSINFO[4]'
+ The release status (e.g., BETA1).
- `-a ANAME'
- The words are assigned to sequential indices of the array
- variable ANAME, starting at 0.
+ `BASH_VERSINFO[5]'
+ The value of `MACHTYPE'.
- `-e'
- Readline (*note Command Line Editing::.) is used to obtain
- the line.
-`shopt'
- shopt [-pqsu] [-o] [OPTNAME ...]
- Toggle the values of variables controlling optional shell behavior.
- With no options, or with the `-p' option, a list of all settable
- options is displayed, with an indication of whether or not each is
- set. Other options have the following meanings:
+`BASH_VERSION'
+ The version number of the current instance of Bash.
- `-s'
- Enable (set) each OPTNAME
+`COLUMNS'
+ Used by the `select' builtin command to determine the terminal
+ width when printing selection lists. Automatically set upon
+ receipt of a `SIGWINCH'.
+
+`COMP_CWORD'
+ An index into `${COMP_WORDS}' of the word containing the current
+ cursor position. This variable is available only in shell
+ functions invoked by the programmable completion facilities (*note
+ Programmable Completion::).
+
+`COMP_LINE'
+ The current command line. This variable is available only in
+ shell functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+`COMP_POINT'
+ The index of the current cursor position relative to the beginning
+ of the current command. If the current cursor position is at the
+ end of the current command, the value of this variable is equal to
+ `${#COMP_LINE}'. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+`COMP_TYPE'
+ Set to an integer value corresponding to the type of completion
+ attempted that caused a completion function to be called: TAB, for
+ normal completion, `?', for listing completions after successive
+ tabs, `!', for listing alternatives on partial word completion,
+ `@', to list completions if the word is not unmodified, or `%',
+ for menu completion. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+`COMP_KEY'
+ The key (or final key of a key sequence) used to invoke the current
+ completion function.
+
+`COMP_WORDBREAKS'
+ The set of characters that the Readline library treats as word
+ separators when performing word completion. If `COMP_WORDBREAKS'
+ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+`COMP_WORDS'
+ An array variable consisting of the individual words in the
+ current command line. The words are split on shell metacharacters
+ as the shell parser would separate them. This variable is
+ available only in shell functions invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+`COMPREPLY'
+ An array variable from which Bash reads the possible completions
+ generated by a shell function invoked by the programmable
+ completion facility (*note Programmable Completion::).
- `-u'
- Disable (unset) each OPTNAME.
+`DIRSTACK'
+ An array variable containing the current contents of the directory
+ stack. Directories appear in the stack in the order they are
+ displayed by the `dirs' builtin. Assigning to members of this
+ array variable may be used to modify directories already in the
+ stack, but the `pushd' and `popd' builtins must be used to add and
+ remove directories. Assignment to this variable will not change
+ the current directory. If `DIRSTACK' is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+`EMACS'
+ If Bash finds this variable in the environment when the shell
+ starts with value `t', it assumes that the shell is running in an
+ emacs shell buffer and disables line editing.
- `-q'
- Suppresses normal output; the return status indicates whether
- the OPTNAME is set or unset. If multiple OPTNAME arguments
- are given with `-q', the return status is zero if all
- OPTNAMES are enabled; non-zero otherwise.
+`EUID'
+ The numeric effective user id of the current user. This variable
+ is readonly.
- `-o'
- Restricts the values of OPTNAME to be those defined for the
- `-o' option to the `set' builtin (*note The Set Builtin::.).
+`FCEDIT'
+ The editor used as a default by the `-e' option to the `fc'
+ builtin command.
- If either of `-s' or `-u' is used with no OPTNAME arguments, the
- display is limited to those options which are set or unset,
- respectively.
+`FIGNORE'
+ A colon-separated list of suffixes to ignore when performing
+ filename completion. A file name whose suffix matches one of the
+ entries in `FIGNORE' is excluded from the list of matched file
+ names. A sample value is `.o:~'
- Unless otherwise noted, the `shopt' options are disabled (off) by
- default.
+`FUNCNAME'
+ An array variable containing the names of all shell functions
+ currently in the execution call stack. The element with index 0
+ is the name of any currently-executing shell function. The
+ bottom-most element is `"main"'. This variable exists only when a
+ shell function is executing. Assignments to `FUNCNAME' have no
+ effect and return an error status. If `FUNCNAME' is unset, it
+ loses its special properties, even if it is subsequently reset.
- The return status when listing options is zero if all OPTNAMES are
- enabled, non-zero otherwise. When setting or unsetting options,
- the return status is zero unless an OPTNAME is not a legal shell
- option.
+`GLOBIGNORE'
+ A colon-separated list of patterns defining the set of filenames to
+ be ignored by filename expansion. If a filename matched by a
+ filename expansion pattern also matches one of the patterns in
+ `GLOBIGNORE', it is removed from the list of matches.
- The list of `shopt' options is:
- `cdable_vars'
- If this is set, an argument to the `cd' builtin command that
- is not a directory is assumed to be the name of a variable
- whose value is the directory to change to.
+`GROUPS'
+ An array variable containing the list of groups of which the
+ current user is a member. Assignments to `GROUPS' have no effect
+ and return an error status. If `GROUPS' is unset, it loses its
+ special properties, even if it is subsequently reset.
- `cdspell'
- If set, minor errors in the spelling of a directory component
- in a `cd' command will be corrected. The errors checked for
- are transposed characters, a missing character, and a
- character too many. If a correction is found, the corrected
- path is printed, and the command proceeds. This option is
- only used by interactive shells.
+`histchars'
+ Up to three characters which control history expansion, quick
+ substitution, and tokenization (*note History Interaction::). The
+ first character is the HISTORY EXPANSION character, that is, the
+ character which signifies the start of a history expansion,
+ normally `!'. The second character is the character which
+ signifies `quick substitution' when seen as the first character on
+ a line, normally `^'. The optional third character is the
+ character which indicates that the remainder of the line is a
+ comment when found as the first character of a word, usually `#'.
+ The history comment character causes history substitution to be
+ skipped for the remaining words on the line. It does not
+ necessarily cause the shell parser to treat the rest of the line
+ as a comment.
- `checkhash'
- If this is set, Bash checks that a command found in the hash
- table exists before trying to execute it. If a hashed
- command no longer exists, a normal path search is performed.
+`HISTCMD'
+ The history number, or index in the history list, of the current
+ command. If `HISTCMD' is unset, it loses its special properties,
+ even if it is subsequently reset.
- `checkwinsize'
- If set, Bash checks the window size after each command and,
- if necessary, updates the values of `LINES' and `COLUMNS'.
+`HISTCONTROL'
+ A colon-separated list of values controlling how commands are
+ saved on the history list. If the list of values includes
+ `ignorespace', lines which begin with a space character are not
+ saved in the history list. A value of `ignoredups' causes lines
+ which match the previous history entry to not be saved. A value
+ of `ignoreboth' is shorthand for `ignorespace' and `ignoredups'.
+ A value of `erasedups' causes all previous lines matching the
+ current line to be removed from the history list before that line
+ is saved. Any value not in the above list is ignored. If
+ `HISTCONTROL' is unset, or does not include a valid value, all
+ lines read by the shell parser are saved on the history list,
+ subject to the value of `HISTIGNORE'. The second and subsequent
+ lines of a multi-line compound command are not tested, and are
+ added to the history regardless of the value of `HISTCONTROL'.
- `cmdhist'
- If set, Bash attempts to save all lines of a multiple-line
- command in the same history entry. This allows easy
- re-editing of multi-line commands.
+`HISTFILE'
+ The name of the file to which the command history is saved. The
+ default value is `~/.bash_history'.
- `dotglob'
- If set, Bash includes filenames beginning with a `.' in the
- results of filename expansion.
+`HISTFILESIZE'
+ The maximum number of lines contained in the history file. When
+ this variable is assigned a value, the history file is truncated,
+ if necessary, by removing the oldest entries, to contain no more
+ than that number of lines. The history file is also truncated to
+ this size after writing it when an interactive shell exits. The
+ default value is 500.
- `execfail'
- If this is set, a non-interactive shell will not exit if it
- cannot execute the file specified as an argument to the `exec'
- builtin command. An interactive shell does not exit if `exec'
- fails.
+`HISTIGNORE'
+ A colon-separated list of patterns used to decide which command
+ lines should be saved on the history list. Each pattern is
+ anchored at the beginning of the line and must match the complete
+ line (no implicit `*' is appended). Each pattern is tested
+ against the line after the checks specified by `HISTCONTROL' are
+ applied. In addition to the normal shell pattern matching
+ characters, `&' matches the previous history line. `&' may be
+ escaped using a backslash; the backslash is removed before
+ attempting a match. The second and subsequent lines of a
+ multi-line compound command are not tested, and are added to the
+ history regardless of the value of `HISTIGNORE'.
- `histappend'
- If set, the history list is appended to the file named by the
- value of the `HISTFILE' variable when the shell exits, rather
- than overwriting the file.
+ `HISTIGNORE' subsumes the function of `HISTCONTROL'. A pattern of
+ `&' is identical to `ignoredups', and a pattern of `[ ]*' is
+ identical to `ignorespace'. Combining these two patterns,
+ separating them with a colon, provides the functionality of
+ `ignoreboth'.
+
+`HISTSIZE'
+ The maximum number of commands to remember on the history list.
+ The default value is 500.
+
+`HISTTIMEFORMAT'
+ If this variable is set and not null, its value is used as a
+ format string for STRFTIME to print the time stamp associated with
+ each history entry displayed by the `history' builtin. If this
+ variable is set, time stamps are written to the history file so
+ they may be preserved across shell sessions. This uses the
+ history comment character to distinguish timestamps from other
+ history lines.
+
+`HOSTFILE'
+ Contains the name of a file in the same format as `/etc/hosts' that
+ should be read when the shell needs to complete a hostname. The
+ list of possible hostname completions may be changed while the
+ shell is running; the next time hostname completion is attempted
+ after the value is changed, Bash adds the contents of the new file
+ to the existing list. If `HOSTFILE' is set, but has no value,
+ Bash attempts to read `/etc/hosts' to obtain the list of possible
+ hostname completions. When `HOSTFILE' is unset, the hostname list
+ is cleared.
+
+`HOSTNAME'
+ The name of the current host.
+
+`HOSTTYPE'
+ A string describing the machine Bash is running on.
+
+`IGNOREEOF'
+ Controls the action of the shell on receipt of an `EOF' character
+ as the sole input. If set, the value denotes the number of
+ consecutive `EOF' characters that can be read as the first
+ character on an input line before the shell will exit. If the
+ variable exists but does not have a numeric value (or has no
+ value) then the default is 10. If the variable does not exist,
+ then `EOF' signifies the end of input to the shell. This is only
+ in effect for interactive shells.
+
+`INPUTRC'
+ The name of the Readline initialization file, overriding the
+ default of `~/.inputrc'.
+
+`LANG'
+ Used to determine the locale category for any category not
+ specifically selected with a variable starting with `LC_'.
+
+`LC_ALL'
+ This variable overrides the value of `LANG' and any other `LC_'
+ variable specifying a locale category.
+
+`LC_COLLATE'
+ This variable determines the collation order used when sorting the
+ results of filename expansion, and determines the behavior of
+ range expressions, equivalence classes, and collating sequences
+ within filename expansion and pattern matching (*note Filename
+ Expansion::).
+
+`LC_CTYPE'
+ This variable determines the interpretation of characters and the
+ behavior of character classes within filename expansion and pattern
+ matching (*note Filename Expansion::).
+
+`LC_MESSAGES'
+ This variable determines the locale used to translate double-quoted
+ strings preceded by a `$' (*note Locale Translation::).
+
+`LC_NUMERIC'
+ This variable determines the locale category used for number
+ formatting.
+
+`LINENO'
+ The line number in the script or shell function currently
+ executing.
+
+`LINES'
+ Used by the `select' builtin command to determine the column length
+ for printing selection lists. Automatically set upon receipt of a
+ `SIGWINCH'.
+
+`MACHTYPE'
+ A string that fully describes the system type on which Bash is
+ executing, in the standard GNU CPU-COMPANY-SYSTEM format.
+
+`MAILCHECK'
+ How often (in seconds) that the shell should check for mail in the
+ files specified in the `MAILPATH' or `MAIL' variables. The
+ default is 60 seconds. When it is time to check for mail, the
+ shell does so before displaying the primary prompt. If this
+ variable is unset, or set to a value that is not a number greater
+ than or equal to zero, the shell disables mail checking.
+
+`OLDPWD'
+ The previous working directory as set by the `cd' builtin.
+
+`OPTERR'
+ If set to the value 1, Bash displays error messages generated by
+ the `getopts' builtin command.
+
+`OSTYPE'
+ A string describing the operating system Bash is running on.
+
+`PIPESTATUS'
+ An array variable (*note Arrays::) containing a list of exit
+ status values from the processes in the most-recently-executed
+ foreground pipeline (which may contain only a single command).
+
+`POSIXLY_CORRECT'
+ If this variable is in the environment when `bash' starts, the
+ shell enters POSIX mode (*note Bash POSIX Mode::) before reading
+ the startup files, as if the `--posix' invocation option had been
+ supplied. If it is set while the shell is running, `bash' enables
+ POSIX mode, as if the command
+ `set -o posix'
+ had been executed.
+
+`PPID'
+ The process ID of the shell's parent process. This variable is
+ readonly.
+
+`PROMPT_COMMAND'
+ If set, the value is interpreted as a command to execute before
+ the printing of each primary prompt (`$PS1').
+
+`PROMPT_DIRTRIM'
+ If set to a number greater than zero, the value is used as the
+ number of trailing directory components to retain when expanding
+ the `\w' and `\W' prompt string escapes (*note Printing a
+ Prompt::). Characters removed are replaced with an ellipsis.
+
+`PS3'
+ The value of this variable is used as the prompt for the `select'
+ command. If this variable is not set, the `select' command
+ prompts with `#? '
+
+`PS4'
+ The value is the prompt printed before the command line is echoed
+ when the `-x' option is set (*note The Set Builtin::). The first
+ character of `PS4' is replicated multiple times, as necessary, to
+ indicate multiple levels of indirection. The default is `+ '.
+
+`PWD'
+ The current working directory as set by the `cd' builtin.
+
+`RANDOM'
+ Each time this parameter is referenced, a random integer between 0
+ and 32767 is generated. Assigning a value to this variable seeds
+ the random number generator.
+
+`REPLY'
+ The default variable for the `read' builtin.
+
+`SECONDS'
+ This variable expands to the number of seconds since the shell was
+ started. Assignment to this variable resets the count to the
+ value assigned, and the expanded value becomes the value assigned
+ plus the number of seconds since the assignment.
+
+`SHELL'
+ The full pathname to the shell is kept in this environment
+ variable. If it is not set when the shell starts, Bash assigns to
+ it the full pathname of the current user's login shell.
+
+`SHELLOPTS'
+ A colon-separated list of enabled shell options. Each word in the
+ list is a valid argument for the `-o' option to the `set' builtin
+ command (*note The Set Builtin::). The options appearing in
+ `SHELLOPTS' are those reported as `on' by `set -o'. If this
+ variable is in the environment when Bash starts up, each shell
+ option in the list will be enabled before reading any startup
+ files. This variable is readonly.
+
+`SHLVL'
+ Incremented by one each time a new instance of Bash is started.
+ This is intended to be a count of how deeply your Bash shells are
+ nested.
+
+`TIMEFORMAT'
+ The value of this parameter is used as a format string specifying
+ how the timing information for pipelines prefixed with the `time'
+ reserved word should be displayed. The `%' character introduces an
+ escape sequence that is expanded to a time value or other
+ information. The escape sequences and their meanings are as
+ follows; the braces denote optional portions.
+
+ `%%'
+ A literal `%'.
+
+ `%[P][l]R'
+ The elapsed time in seconds.
+
+ `%[P][l]U'
+ The number of CPU seconds spent in user mode.
+
+ `%[P][l]S'
+ The number of CPU seconds spent in system mode.
+
+ `%P'
+ The CPU percentage, computed as (%U + %S) / %R.
+
+ The optional P is a digit specifying the precision, the number of
+ fractional digits after a decimal point. A value of 0 causes no
+ decimal point or fraction to be output. At most three places
+ after the decimal point may be specified; values of P greater than
+ 3 are changed to 3. If P is not specified, the value 3 is used.
+
+ The optional `l' specifies a longer format, including minutes, of
+ the form MMmSS.FFs. The value of P determines whether or not the
+ fraction is included.
+
+ If this variable is not set, Bash acts as if it had the value
+ `$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS''
+ If the value is null, no timing information is displayed. A
+ trailing newline is added when the format string is displayed.
+
+`TMOUT'
+ If set to a value greater than zero, `TMOUT' is treated as the
+ default timeout for the `read' builtin (*note Bash Builtins::).
+ The `select' command (*note Conditional Constructs::) terminates
+ if input does not arrive after `TMOUT' seconds when input is coming
+ from a terminal.
+
+ In an interactive shell, the value is interpreted as the number of
+ seconds to wait for input after issuing the primary prompt when
+ the shell is interactive. Bash terminates after that number of
+ seconds if input does not arrive.
+
+`TMPDIR'
+ If set, Bash uses its value as the name of a directory in which
+ Bash creates temporary files for the shell's use.
+
+`UID'
+ The numeric real user id of the current user. This variable is
+ readonly.
+
+
+\1f
+File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Shell Variables, Up: Top
+
+6 Bash Features
+***************
+
+This section describes features unique to Bash.
+
+* Menu:
+
+* Invoking Bash:: Command line options that you can give
+ to Bash.
+* Bash Startup Files:: When and how Bash executes scripts.
+* Interactive Shells:: What an interactive shell is.
+* Bash Conditional Expressions:: Primitives used in composing expressions for
+ the `test' builtin.
+* Shell Arithmetic:: Arithmetic on shell variables.
+* Aliases:: Substituting one command for another.
+* Arrays:: Array Variables.
+* The Directory Stack:: History of visited directories.
+* Printing a Prompt:: Controlling the PS1 string.
+* The Restricted Shell:: A more controlled mode of shell execution.
+* Bash POSIX Mode:: Making Bash behave more closely to what
+ the POSIX standard specifies.
+
+\1f
+File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
+
+6.1 Invoking Bash
+=================
+
+ bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] [ARGUMENT ...]
+ bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] -c STRING [ARGUMENT ...]
+ bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] [ARGUMENT ...]
+
+ In addition to the single-character shell command-line options
+(*note The Set Builtin::), there are several multi-character options
+that you can use. These options must appear on the command line before
+the single-character options to be recognized.
+
+`--debugger'
+ Arrange for the debugger profile to be executed before the shell
+ starts. Turns on extended debugging mode (see *note The Shopt
+ Builtin:: for a description of the `extdebug' option to the `shopt'
+ builtin) and shell function tracing (see *note The Set Builtin::
+ for a description of the `-o functrace' option).
+
+`--dump-po-strings'
+ A list of all double-quoted strings preceded by `$' is printed on
+ the standard output in the GNU `gettext' PO (portable object) file
+ format. Equivalent to `-D' except for the output format.
+
+`--dump-strings'
+ Equivalent to `-D'.
+
+`--help'
+ Display a usage message on standard output and exit successfully.
+
+`--init-file FILENAME'
+`--rcfile FILENAME'
+ Execute commands from FILENAME (instead of `~/.bashrc') in an
+ interactive shell.
+
+`--login'
+ Equivalent to `-l'.
+
+`--noediting'
+ Do not use the GNU Readline library (*note Command Line Editing::)
+ to read command lines when the shell is interactive.
+
+`--noprofile'
+ Don't load the system-wide startup file `/etc/profile' or any of
+ the personal initialization files `~/.bash_profile',
+ `~/.bash_login', or `~/.profile' when Bash is invoked as a login
+ shell.
+
+`--norc'
+ Don't read the `~/.bashrc' initialization file in an interactive
+ shell. This is on by default if the shell is invoked as `sh'.
+
+`--posix'
+ Change the behavior of Bash where the default operation differs
+ from the POSIX standard to match the standard. This is intended
+ to make Bash behave as a strict superset of that standard. *Note
+ Bash POSIX Mode::, for a description of the Bash POSIX mode.
+
+`--restricted'
+ Make the shell a restricted shell (*note The Restricted Shell::).
+
+`--verbose'
+ Equivalent to `-v'. Print shell input lines as they're read.
+
+`--version'
+ Show version information for this instance of Bash on the standard
+ output and exit successfully.
+
+
+ There are several single-character options that may be supplied at
+invocation which are not available with the `set' builtin.
+
+`-c STRING'
+ Read and execute commands from STRING after processing the
+ options, then exit. Any remaining arguments are assigned to the
+ positional parameters, starting with `$0'.
+
+`-i'
+ Force the shell to run interactively. Interactive shells are
+ described in *note Interactive Shells::.
+
+`-l'
+ Make this shell act as if it had been directly invoked by login.
+ When the shell is interactive, this is equivalent to starting a
+ login shell with `exec -l bash'. When the shell is not
+ interactive, the login shell startup files will be executed.
+ `exec bash -l' or `exec bash --login' will replace the current
+ shell with a Bash login shell. *Note Bash Startup Files::, for a
+ description of the special behavior of a login shell.
+
+`-r'
+ Make the shell a restricted shell (*note The Restricted Shell::).
+
+`-s'
+ If this option is present, or if no arguments remain after option
+ processing, then commands are read from the standard input. This
+ option allows the positional parameters to be set when invoking an
+ interactive shell.
+
+`-D'
+ A list of all double-quoted strings preceded by `$' is printed on
+ the standard output. These are the strings that are subject to
+ language translation when the current locale is not `C' or `POSIX'
+ (*note Locale Translation::). This implies the `-n' option; no
+ commands will be executed.
+
+`[-+]O [SHOPT_OPTION]'
+ SHOPT_OPTION is one of the shell options accepted by the `shopt'
+ builtin (*note The Shopt Builtin::). If SHOPT_OPTION is present,
+ `-O' sets the value of that option; `+O' unsets it. If
+ SHOPT_OPTION is not supplied, the names and values of the shell
+ options accepted by `shopt' are printed on the standard output.
+ If the invocation option is `+O', the output is displayed in a
+ format that may be reused as input.
+
+`--'
+ A `--' signals the end of options and disables further option
+ processing. Any arguments after the `--' are treated as filenames
+ and arguments.
+
+
+ A _login_ shell is one whose first character of argument zero is
+`-', or one invoked with the `--login' option.
+
+ An _interactive_ shell is one started without non-option arguments,
+unless `-s' is specified, without specifying the `-c' option, and whose
+input and output are both connected to terminals (as determined by
+`isatty(3)'), or one started with the `-i' option. *Note Interactive
+Shells::, for more information.
+
+ If arguments remain after option processing, and neither the `-c'
+nor the `-s' option has been supplied, the first argument is assumed to
+be the name of a file containing shell commands (*note Shell Scripts::).
+When Bash is invoked in this fashion, `$0' is set to the name of the
+file, and the positional parameters are set to the remaining arguments.
+Bash reads and executes commands from this file, then exits. Bash's
+exit status is the exit status of the last command executed in the
+script. If no commands are executed, the exit status is 0.
+
+\1f
+File: bashref.info, Node: Bash Startup Files, Next: Interactive Shells, Prev: Invoking Bash, Up: Bash Features
+
+6.2 Bash Startup Files
+======================
+
+This section describes how Bash executes its startup files. If any of
+the files exist but cannot be read, Bash reports an error. Tildes are
+expanded in file names as described above under Tilde Expansion (*note
+Tilde Expansion::).
+
+ Interactive shells are described in *note Interactive Shells::.
+
+Invoked as an interactive login shell, or with `--login'
+........................................................
+
+When Bash is invoked as an interactive login shell, or as a
+non-interactive shell with the `--login' option, it first reads and
+executes commands from the file `/etc/profile', if that file exists.
+After reading that file, it looks for `~/.bash_profile',
+`~/.bash_login', and `~/.profile', in that order, and reads and
+executes commands from the first one that exists and is readable. The
+`--noprofile' option may be used when the shell is started to inhibit
+this behavior.
+
+ When a login shell exits, Bash reads and executes commands from the
+file `~/.bash_logout', if it exists.
+
+Invoked as an interactive non-login shell
+.........................................
+
+When an interactive shell that is not a login shell is started, Bash
+reads and executes commands from `~/.bashrc', if that file exists.
+This may be inhibited by using the `--norc' option. The `--rcfile
+FILE' option will force Bash to read and execute commands from FILE
+instead of `~/.bashrc'.
+
+ So, typically, your `~/.bash_profile' contains the line
+ `if [ -f ~/.bashrc ]; then . ~/.bashrc; fi'
+ after (or before) any login-specific initializations.
+
+Invoked non-interactively
+.........................
+
+When Bash is started non-interactively, to run a shell script, for
+example, it looks for the variable `BASH_ENV' in the environment,
+expands its value if it appears there, and uses the expanded value as
+the name of a file to read and execute. Bash behaves as if the
+following command were executed:
+ `if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi'
+ but the value of the `PATH' variable is not used to search for the
+file name.
+
+ As noted above, if a non-interactive shell is invoked with the
+`--login' option, Bash attempts to read and execute commands from the
+login shell startup files.
+
+Invoked with name `sh'
+......................
+
+If Bash is invoked with the name `sh', it tries to mimic the startup
+behavior of historical versions of `sh' as closely as possible, while
+conforming to the POSIX standard as well.
+
+ When invoked as an interactive login shell, or as a non-interactive
+shell with the `--login' option, it first attempts to read and execute
+commands from `/etc/profile' and `~/.profile', in that order. The
+`--noprofile' option may be used to inhibit this behavior. When
+invoked as an interactive shell with the name `sh', Bash looks for the
+variable `ENV', expands its value if it is defined, and uses the
+expanded value as the name of a file to read and execute. Since a
+shell invoked as `sh' does not attempt to read and execute commands
+from any other startup files, the `--rcfile' option has no effect. A
+non-interactive shell invoked with the name `sh' does not attempt to
+read any other startup files.
+
+ When invoked as `sh', Bash enters POSIX mode after the startup files
+are read.
+
+Invoked in POSIX mode
+.....................
+
+When Bash is started in POSIX mode, as with the `--posix' command line
+option, it follows the POSIX standard for startup files. In this mode,
+interactive shells expand the `ENV' variable and commands are read and
+executed from the file whose name is the expanded value. No other
+startup files are read.
+
+Invoked by remote shell daemon
+..............................
+
+Bash attempts to determine when it is being run with its standard input
+connected to a a network connection, as if by the remote shell daemon,
+usually `rshd', or the secure shell daemon `sshd'. If Bash determines
+it is being run in this fashion, it reads and executes commands from
+`~/.bashrc', if that file exists and is readable. It will not do this
+if invoked as `sh'. The `--norc' option may be used to inhibit this
+behavior, and the `--rcfile' option may be used to force another file
+to be read, but `rshd' does not generally invoke the shell with those
+options or allow them to be specified.
+
+Invoked with unequal effective and real UID/GIDs
+................................................
+
+If Bash is started with the effective user (group) id not equal to the
+real user (group) id, and the `-p' option is not supplied, no startup
+files are read, shell functions are not inherited from the environment,
+the `SHELLOPTS' variable, if it appears in the environment, is ignored,
+and the effective user id is set to the real user id. If the `-p'
+option is supplied at invocation, the startup behavior is the same, but
+the effective user id is not reset.
+
+\1f
+File: bashref.info, Node: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
+
+6.3 Interactive Shells
+======================
+
+* Menu:
+
+* What is an Interactive Shell?:: What determines whether a shell is Interactive.
+* Is this Shell Interactive?:: How to tell if a shell is interactive.
+* Interactive Shell Behavior:: What changes in a interactive shell?
+
+\1f
+File: bashref.info, Node: What is an Interactive Shell?, Next: Is this Shell Interactive?, Up: Interactive Shells
+
+6.3.1 What is an Interactive Shell?
+-----------------------------------
+
+An interactive shell is one started without non-option arguments,
+unless `-s' is specified, without specifying the `-c' option, and whose
+input and error output are both connected to terminals (as determined
+by `isatty(3)'), or one started with the `-i' option.
- `histreedit'
- If set, and Readline is being used, a user is given the
- opportunity to re-edit a failed history substitution.
+ An interactive shell generally reads from and writes to a user's
+terminal.
- `histverify'
- If set, and Readline is being used, the results of history
- substitution are not immediately passed to the shell parser.
- Instead, the resulting line is loaded into the Readline
- editing buffer, allowing further modification.
+ The `-s' invocation option may be used to set the positional
+parameters when an interactive shell is started.
- `hostcomplete'
- If set, and Readline is being used, Bash will attempt to
- perform hostname completion when a word beginning with `@' is
- being completed (*note Commands For Completion::.). This
- option is enabled by default.
+\1f
+File: bashref.info, Node: Is this Shell Interactive?, Next: Interactive Shell Behavior, Prev: What is an Interactive Shell?, Up: Interactive Shells
- `interactive_comments'
- Allow a word beginning with `#' to cause that word and all
- remaining characters on that line to be ignored in an
- interactive shell. This option is enabled by default.
+6.3.2 Is this Shell Interactive?
+--------------------------------
+
+To determine within a startup script whether or not Bash is running
+interactively, test the value of the `-' special parameter. It
+contains `i' when the shell is interactive. For example:
+
+ case "$-" in
+ *i*) echo This shell is interactive ;;
+ *) echo This shell is not interactive ;;
+ esac
+
+ Alternatively, startup scripts may examine the variable `PS1'; it is
+unset in non-interactive shells, and set in interactive shells. Thus:
+
+ if [ -z "$PS1" ]; then
+ echo This shell is not interactive
+ else
+ echo This shell is interactive
+ fi
+
+\1f
+File: bashref.info, Node: Interactive Shell Behavior, Prev: Is this Shell Interactive?, Up: Interactive Shells
+
+6.3.3 Interactive Shell Behavior
+--------------------------------
+
+When the shell is running interactively, it changes its behavior in
+several ways.
+
+ 1. Startup files are read and executed as described in *note Bash
+ Startup Files::.
+
+ 2. Job Control (*note Job Control::) is enabled by default. When job
+ control is in effect, Bash ignores the keyboard-generated job
+ control signals `SIGTTIN', `SIGTTOU', and `SIGTSTP'.
+
+ 3. Bash expands and displays `PS1' before reading the first line of a
+ command, and expands and displays `PS2' before reading the second
+ and subsequent lines of a multi-line command.
+
+ 4. Bash executes the value of the `PROMPT_COMMAND' variable as a
+ command before printing the primary prompt, `$PS1' (*note Bash
+ Variables::).
+
+ 5. Readline (*note Command Line Editing::) is used to read commands
+ from the user's terminal.
+
+ 6. Bash inspects the value of the `ignoreeof' option to `set -o'
+ instead of exiting immediately when it receives an `EOF' on its
+ standard input when reading a command (*note The Set Builtin::).
+
+ 7. Command history (*note Bash History Facilities::) and history
+ expansion (*note History Interaction::) are enabled by default.
+ Bash will save the command history to the file named by `$HISTFILE'
+ when an interactive shell exits.
+
+ 8. Alias expansion (*note Aliases::) is performed by default.
+
+ 9. In the absence of any traps, Bash ignores `SIGTERM' (*note
+ Signals::).
+
+ 10. In the absence of any traps, `SIGINT' is caught and handled
+ ((*note Signals::). `SIGINT' will interrupt some shell builtins.
+
+ 11. An interactive login shell sends a `SIGHUP' to all jobs on exit if
+ the `huponexit' shell option has been enabled (*note Signals::).
+
+ 12. The `-n' invocation option is ignored, and `set -n' has no effect
+ (*note The Set Builtin::).
+
+ 13. Bash will check for mail periodically, depending on the values of
+ the `MAIL', `MAILPATH', and `MAILCHECK' shell variables (*note
+ Bash Variables::).
+
+ 14. Expansion errors due to references to unbound shell variables after
+ `set -u' has been enabled will not cause the shell to exit (*note
+ The Set Builtin::).
+
+ 15. The shell will not exit on expansion errors caused by VAR being
+ unset or null in `${VAR:?WORD}' expansions (*note Shell Parameter
+ Expansion::).
+
+ 16. Redirection errors encountered by shell builtins will not cause the
+ shell to exit.
+
+ 17. When running in POSIX mode, a special builtin returning an error
+ status will not cause the shell to exit (*note Bash POSIX Mode::).
+
+ 18. A failed `exec' will not cause the shell to exit (*note Bourne
+ Shell Builtins::).
+
+ 19. Parser syntax errors will not cause the shell to exit.
+
+ 20. Simple spelling correction for directory arguments to the `cd'
+ builtin is enabled by default (see the description of the `cdspell'
+ option to the `shopt' builtin in *note The Shopt Builtin::).
+
+ 21. The shell will check the value of the `TMOUT' variable and exit if
+ a command is not read within the specified number of seconds after
+ printing `$PS1' (*note Bash Variables::).
+
+
+\1f
+File: bashref.info, Node: Bash Conditional Expressions, Next: Shell Arithmetic, Prev: Interactive Shells, Up: Bash Features
+
+6.4 Bash Conditional Expressions
+================================
+
+Conditional expressions are used by the `[[' compound command and the
+`test' and `[' builtin commands.
+
+ Expressions may be unary or binary. Unary expressions are often
+used to examine the status of a file. There are string operators and
+numeric comparison operators as well. If the FILE argument to one of
+the primaries is of the form `/dev/fd/N', then file descriptor N is
+checked. If the FILE argument to one of the primaries is one of
+`/dev/stdin', `/dev/stdout', or `/dev/stderr', file descriptor 0, 1, or
+2, respectively, is checked.
+
+ Unless otherwise specified, primaries that operate on files follow
+symbolic links and operate on the target of the link, rather than the
+link itself.
+
+`-a FILE'
+ True if FILE exists.
+
+`-b FILE'
+ True if FILE exists and is a block special file.
+
+`-c FILE'
+ True if FILE exists and is a character special file.
+
+`-d FILE'
+ True if FILE exists and is a directory.
+
+`-e FILE'
+ True if FILE exists.
+
+`-f FILE'
+ True if FILE exists and is a regular file.
+
+`-g FILE'
+ True if FILE exists and its set-group-id bit is set.
+
+`-h FILE'
+ True if FILE exists and is a symbolic link.
+
+`-k FILE'
+ True if FILE exists and its "sticky" bit is set.
+
+`-p FILE'
+ True if FILE exists and is a named pipe (FIFO).
+
+`-r FILE'
+ True if FILE exists and is readable.
+
+`-s FILE'
+ True if FILE exists and has a size greater than zero.
+
+`-t FD'
+ True if file descriptor FD is open and refers to a terminal.
+
+`-u FILE'
+ True if FILE exists and its set-user-id bit is set.
+
+`-w FILE'
+ True if FILE exists and is writable.
+
+`-x FILE'
+ True if FILE exists and is executable.
+
+`-O FILE'
+ True if FILE exists and is owned by the effective user id.
+
+`-G FILE'
+ True if FILE exists and is owned by the effective group id.
+
+`-L FILE'
+ True if FILE exists and is a symbolic link.
+
+`-S FILE'
+ True if FILE exists and is a socket.
+
+`-N FILE'
+ True if FILE exists and has been modified since it was last read.
+
+`FILE1 -nt FILE2'
+ True if FILE1 is newer (according to modification date) than
+ FILE2, or if FILE1 exists and FILE2 does not.
+
+`FILE1 -ot FILE2'
+ True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
+ does not.
+
+`FILE1 -ef FILE2'
+ True if FILE1 and FILE2 refer to the same device and inode numbers.
+
+`-o OPTNAME'
+ True if shell option OPTNAME is enabled. The list of options
+ appears in the description of the `-o' option to the `set' builtin
+ (*note The Set Builtin::).
+
+`-z STRING'
+ True if the length of STRING is zero.
+
+`-n STRING'
+`STRING'
+ True if the length of STRING is non-zero.
+
+`STRING1 == STRING2'
+ True if the strings are equal. `=' may be used in place of `=='
+ for strict POSIX compliance.
+
+`STRING1 != STRING2'
+ True if the strings are not equal.
+
+`STRING1 < STRING2'
+ True if STRING1 sorts before STRING2 lexicographically in the
+ current locale.
+
+`STRING1 > STRING2'
+ True if STRING1 sorts after STRING2 lexicographically in the
+ current locale.
+
+`ARG1 OP ARG2'
+ `OP' is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These
+ arithmetic binary operators return true if ARG1 is equal to, not
+ equal to, less than, less than or equal to, greater than, or
+ greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
+ positive or negative integers.
+
+
+\1f
+File: bashref.info, Node: Shell Arithmetic, Next: Aliases, Prev: Bash Conditional Expressions, Up: Bash Features
+
+6.5 Shell Arithmetic
+====================
+
+The shell allows arithmetic expressions to be evaluated, as one of the
+shell expansions or by the `let' and the `-i' option to the `declare'
+builtins.
+
+ Evaluation is done in fixed-width integers with no check for
+overflow, though division by 0 is trapped and flagged as an error. The
+operators and their precedence, associativity, and values are the same
+as in the C language. The following list of operators is grouped into
+levels of equal-precedence operators. The levels are listed in order
+of decreasing precedence.
+
+`ID++ ID--'
+ variable post-increment and post-decrement
+
+`++ID --ID'
+ variable pre-increment and pre-decrement
+
+`- +'
+ unary minus and plus
+
+`! ~'
+ logical and bitwise negation
+
+`**'
+ exponentiation
+
+`* / %'
+ multiplication, division, remainder
+
+`+ -'
+ addition, subtraction
+
+`<< >>'
+ left and right bitwise shifts
+
+`<= >= < >'
+ comparison
+
+`== !='
+ equality and inequality
+
+`&'
+ bitwise AND
+
+`^'
+ bitwise exclusive OR
+
+`|'
+ bitwise OR
+
+`&&'
+ logical AND
+
+`||'
+ logical OR
+
+`expr ? expr : expr'
+ conditional operator
+
+`= *= /= %= += -= <<= >>= &= ^= |='
+ assignment
+
+`expr1 , expr2'
+ comma
+
+ Shell variables are allowed as operands; parameter expansion is
+performed before the expression is evaluated. Within an expression,
+shell variables may also be referenced by name without using the
+parameter expansion syntax. A shell variable that is null or unset
+evaluates to 0 when referenced by name without using the parameter
+expansion syntax. The value of a variable is evaluated as an
+arithmetic expression when it is referenced, or when a variable which
+has been given the INTEGER attribute using `declare -i' is assigned a
+value. A null value evaluates to 0. A shell variable need not have
+its integer attribute turned on to be used in an expression.
+
+ Constants with a leading 0 are interpreted as octal numbers. A
+leading `0x' or `0X' denotes hexadecimal. Otherwise, numbers take the
+form [BASE`#']N, where BASE is a decimal number between 2 and 64
+representing the arithmetic base, and N is a number in that base. If
+BASE`#' is omitted, then base 10 is used. The digits greater than 9
+are represented by the lowercase letters, the uppercase letters, `@',
+and `_', in that order. If BASE is less than or equal to 36, lowercase
+and uppercase letters may be used interchangeably to represent numbers
+between 10 and 35.
+
+ Operators are evaluated in order of precedence. Sub-expressions in
+parentheses are evaluated first and may override the precedence rules
+above.
+
+\1f
+File: bashref.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
+
+6.6 Aliases
+===========
+
+ALIASES allow a string to be substituted for a word when it is used as
+the first word of a simple command. The shell maintains a list of
+aliases that may be set and unset with the `alias' and `unalias'
+builtin commands.
+
+ The first word of each simple command, if unquoted, is checked to see
+if it has an alias. If so, that word is replaced by the text of the
+alias. The characters `/', `$', ``', `=' and any of the shell
+metacharacters or quoting characters listed above may not appear in an
+alias name. The replacement text may contain any valid shell input,
+including shell metacharacters. The first word of the replacement text
+is tested for aliases, but a word that is identical to an alias being
+expanded is not expanded a second time. This means that one may alias
+`ls' to `"ls -F"', for instance, and Bash does not try to recursively
+expand the replacement text. If the last character of the alias value
+is a space or tab character, then the next command word following the
+alias is also checked for alias expansion.
+
+ Aliases are created and listed with the `alias' command, and removed
+with the `unalias' command.
+
+ There is no mechanism for using arguments in the replacement text,
+as in `csh'. If arguments are needed, a shell function should be used
+(*note Shell Functions::).
+
+ Aliases are not expanded when the shell is not interactive, unless
+the `expand_aliases' shell option is set using `shopt' (*note The Shopt
+Builtin::).
+
+ The rules concerning the definition and use of aliases are somewhat
+confusing. Bash always reads at least one complete line of input
+before executing any of the commands on that line. Aliases are
+expanded when a command is read, not when it is executed. Therefore, an
+alias definition appearing on the same line as another command does not
+take effect until the next line of input is read. The commands
+following the alias definition on that line are not affected by the new
+alias. This behavior is also an issue when functions are executed.
+Aliases are expanded when a function definition is read, not when the
+function is executed, because a function definition is itself a
+compound command. As a consequence, aliases defined in a function are
+not available until after that function is executed. To be safe,
+always put alias definitions on a separate line, and do not use `alias'
+in compound commands.
+
+ For almost every purpose, shell functions are preferred over aliases.
+
+\1f
+File: bashref.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
+
+6.7 Arrays
+==========
+
+Bash provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array; the `declare' builtin
+will explicitly declare an array. There is no maximum limit on the
+size of an array, nor any requirement that members be indexed or
+assigned contiguously. Indexed arrays are referenced using integers
+(including arithmetic expressions (*note Shell Arithmetic::) and are
+zero-based; associative arrays use arbitrary strings.
+
+ An indexed array is created automatically if any variable is
+assigned to using the syntax
+ name[SUBSCRIPT]=VALUE
+
+The SUBSCRIPT is treated as an arithmetic expression that must evaluate
+to a number greater than or equal to zero. To explicitly declare an
+array, use
+ declare -a NAME
+ The syntax
+ declare -a NAME[SUBSCRIPT]
+ is also accepted; the SUBSCRIPT is ignored.
- `lithist'
- If enabled, and the `cmdhist' option is enabled, multi-line
- commands are saved to the history with embedded newlines
- rather than using semicolon separators where possible.
+ Associative arrays are created using
+ declare -A NAME.
- `mailwarn'
- If set, and a file that Bash is checking for mail has been
- accessed since the last time it was checked, the message
- `"The mail in MAILFILE has been read"' is displayed.
+ Attributes may be specified for an array variable using the
+`declare' and `readonly' builtins. Each attribute applies to all
+members of an array.
- `nullglob'
- If set, Bash allows filename patterns which match no files to
- expand to a null string, rather than themselves.
+ Arrays are assigned to using compound assignments of the form
+ name=(value1 ... valueN)
+ where each VALUE is of the form `[SUBSCRIPT]='STRING. Indexed array
+assignments do not require the bracket and subscript. When assigning
+to indexed arrays, if the optional subscript is supplied, that index is
+assigned to; otherwise the index of the element assigned is the last
+index assigned to by the statement plus one. Indexing starts at zero.
- `promptvars'
- If set, prompt strings undergo variable and parameter
- expansion after being expanded (*note Printing a Prompt::.).
- This option is enabled by default.
+ When assigning to an associative array, the subscript is required.
- `shift_verbose'
- If this is set, the `shift' builtin prints an error message
- when the shift count exceeds the number of positional
- parameters.
+ This syntax is also accepted by the `declare' builtin. Individual
+array elements may be assigned to using the `name['SUBSCRIPT`]='VALUE
+syntax introduced above.
- `sourcepath'
- If set, the `source' builtin uses the value of `PATH' to find
- the directory containing the file supplied as an argument.
- This is enabled by default.
+ Any element of an array may be referenced using
+`${name['SUBSCRIPT`]}'. The braces are required to avoid conflicts
+with the shell's filename expansion operators. If the SUBSCRIPT is `@'
+or `*', the word expands to all members of the array NAME. These
+subscripts differ only when the word appears within double quotes. If
+the word is double-quoted, `${name[*]}' expands to a single word with
+the value of each array member separated by the first character of the
+`IFS' variable, and `${name[@]}' expands each element of NAME to a
+separate word. When there are no array members, `${name[@]}' expands
+to nothing. If the double-quoted expansion occurs within a word, the
+expansion of the first parameter is joined with the beginning part of
+the original word, and the expansion of the last parameter is joined
+with the last part of the original word. This is analogous to the
+expansion of the special parameters `@' and `*'.
+`${#name['SUBSCRIPT`]}' expands to the length of `${name['SUBSCRIPT`]}'.
+If SUBSCRIPT is `@' or `*', the expansion is the number of elements in
+the array. Referencing an array variable without a subscript is
+equivalent to referencing with a subscript of 0.
-`type'
- type [-all] [-type | -path] [NAME ...]
- For each NAME, indicate how it would be interpreted if used as a
- command name.
+ The `unset' builtin is used to destroy arrays. `unset'
+NAME[SUBSCRIPT] destroys the array element at index SUBSCRIPT. Care
+must be taken to avoid unwanted side effects caused by filename
+generation. `unset' NAME, where NAME is an array, removes the entire
+array. A subscript of `*' or `@' also removes the entire array.
- If the `-type' flag is used, `type' returns a single word which is
- one of `alias', `function', `builtin', `file' or `keyword', if
- NAME is an alias, shell function, shell builtin, disk file, or
- shell reserved word, respectively. If the NAME is not found, then
- nothing is printed, and `type' returns a failure status.
+ The `declare', `local', and `readonly' builtins each accept a `-a'
+option to specify an indexed array and a `-A' option to specify an
+associative array. The `read' builtin accepts a `-a' option to assign
+a list of words read from the standard input to an array, and can read
+values from the standard input into individual array elements. The
+`set' and `declare' builtins display array values in a way that allows
+them to be reused as input.
- If the `-path' flag is used, `type' either returns the name of the
- disk file that would be executed, or nothing if `-type' would not
- return `file'.
+\1f
+File: bashref.info, Node: The Directory Stack, Next: Printing a Prompt, Prev: Arrays, Up: Bash Features
- If the `-all' flag is used, returns all of the places that contain
- an executable named FILE. This includes aliases and functions, if
- and only if the `-path' flag is not also used.
+6.8 The Directory Stack
+=======================
- `type' accepts `-a', `-t', and `-p' as equivalent to `-all',
- `-type', and `-path', respectively.
+* Menu:
-`ulimit'
- ulimit [-acdflmnpstuvSH] [LIMIT]
- `ulimit' provides control over the resources available to processes
- started by the shell, on systems that allow such control. If an
- option is given, it is interpreted as follows:
- `-S'
- change and report the soft limit associated with a resource.
+* Directory Stack Builtins:: Bash builtin commands to manipulate
+ the directory stack.
- `-H'
- change and report the hard limit associated with a resource.
+ The directory stack is a list of recently-visited directories. The
+`pushd' builtin adds directories to the stack as it changes the current
+directory, and the `popd' builtin removes specified directories from
+the stack and changes the current directory to the directory removed.
+The `dirs' builtin displays the contents of the directory stack.
- `-a'
- all current limits are reported.
+ The contents of the directory stack are also visible as the value of
+the `DIRSTACK' shell variable.
- `-c'
- the maximum size of core files created.
+\1f
+File: bashref.info, Node: Directory Stack Builtins, Up: The Directory Stack
- `-d'
- the maximum size of a process's data segment.
+6.8.1 Directory Stack Builtins
+------------------------------
- `-f'
- the maximum size of files created by the shell.
+`dirs'
+ dirs [+N | -N] [-clpv]
+ Display the list of currently remembered directories. Directories
+ are added to the list with the `pushd' command; the `popd' command
+ removes directories from the list.
+ `+N'
+ Displays the Nth directory (counting from the left of the
+ list printed by `dirs' when invoked without options), starting
+ with zero.
- `-l'
- The maximum size that may be locked into memory.
+ `-N'
+ Displays the Nth directory (counting from the right of the
+ list printed by `dirs' when invoked without options), starting
+ with zero.
- `-m'
- the maximum resident set size.
+ `-c'
+ Clears the directory stack by deleting all of the elements.
- `-n'
- the maximum number of open file descriptors.
+ `-l'
+ Produces a longer listing; the default listing format uses a
+ tilde to denote the home directory.
`-p'
- the pipe buffer size.
+ Causes `dirs' to print the directory stack with one entry per
+ line.
- `-s'
- the maximum stack size.
+ `-v'
+ Causes `dirs' to print the directory stack with one entry per
+ line, prefixing each entry with its index in the stack.
- `-t'
- the maximum amount of cpu time in seconds.
+`popd'
+ popd [+N | -N] [-n]
- `-u'
- the maximum number of processes available to a single user.
+ Remove the top entry from the directory stack, and `cd' to the new
+ top directory. When no arguments are given, `popd' removes the
+ top directory from the stack and performs a `cd' to the new top
+ directory. The elements are numbered from 0 starting at the first
+ directory listed with `dirs'; i.e., `popd' is equivalent to `popd
+ +0'.
+ `+N'
+ Removes the Nth directory (counting from the left of the list
+ printed by `dirs'), starting with zero.
- `-v'
- the maximum amount of virtual memory available to the process.
+ `-N'
+ Removes the Nth directory (counting from the right of the
+ list printed by `dirs'), starting with zero.
- If LIMIT is given, it is the new value of the specified resource.
- Otherwise, the current value of the soft limit for the specified
- resource is printed, unless the `-H' option is supplied. When
- setting new limits, if neither `-H' nor `-S' is supplied, both the
- hard and soft limits are set. If no option is given, then `-f' is
- assumed. Values are in 1024-byte increments, except for `-t',
- which is in seconds, `-p', which is in units of 512-byte blocks,
- and `-n' and `-u', which are unscaled values.
+ `-n'
+ Suppresses the normal change of directory when removing
+ directories from the stack, so that only the stack is
+ manipulated.
-\1f
-File: bashref.info, Node: The Set Builtin, Next: Bash Conditional Expressions, Prev: Bash Builtins, Up: Bash Features
+`pushd'
+ pushd [-n] [+N | -N | DIR ]
-The Set Builtin
-===============
+ Save the current directory on the top of the directory stack and
+ then `cd' to DIR. With no arguments, `pushd' exchanges the top
+ two directories.
- This builtin is so overloaded that it deserves its own section.
+ `-n'
+ Suppresses the normal change of directory when adding
+ directories to the stack, so that only the stack is
+ manipulated.
-`set'
- set [-abefhkmnptuvxdBCHP] [-o OPTION] [ARGUMENT ...]
+ `+N'
+ Brings the Nth directory (counting from the left of the list
+ printed by `dirs', starting with zero) to the top of the list
+ by rotating the stack.
- `-a'
- Mark variables which are modified or created for export.
+ `-N'
+ Brings the Nth directory (counting from the right of the list
+ printed by `dirs', starting with zero) to the top of the list
+ by rotating the stack.
- `-b'
- Cause the status of terminated background jobs to be reported
- immediately, rather than before printing the next primary
- prompt.
+ `DIR'
+ Makes the current working directory be the top of the stack,
+ and then executes the equivalent of ``cd' DIR'. `cd's to DIR.
- `-e'
- Exit immediately if a simple command exits with a non-zero
- status.
- `-f'
- Disable file name generation (globbing).
+\1f
+File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
- `-h'
- Locate and remember (hash) commands as they are looked up for
- execution.
+6.9 Controlling the Prompt
+==========================
- `-k'
- All arguments in the form of assignment statements are placed
- in the environment for a command, not just those that precede
- the command name.
+The value of the variable `PROMPT_COMMAND' is examined just before Bash
+prints each primary prompt. If `PROMPT_COMMAND' is set and has a
+non-null value, then the value is executed just as if it had been typed
+on the command line.
- `-m'
- Job control is enabled (*note Job Control::.).
+ In addition, the following table describes the special characters
+which can appear in the prompt variables:
- `-n'
- Read commands but do not execute them.
+`\a'
+ A bell character.
- `-o OPTION-NAME'
- Set the flag corresponding to OPTION-NAME:
+`\d'
+ The date, in "Weekday Month Date" format (e.g., "Tue May 26").
- `allexport'
- same as `-a'.
+`\D{FORMAT}'
+ The FORMAT is passed to `strftime'(3) and the result is inserted
+ into the prompt string; an empty FORMAT results in a
+ locale-specific time representation. The braces are required.
- `braceexpand'
- same as `-B'.
+`\e'
+ An escape character.
- `emacs'
- use an `emacs'-style line editing interface (*note
- Command Line Editing::.).
+`\h'
+ The hostname, up to the first `.'.
- `errexit'
- same as `-e'.
+`\H'
+ The hostname.
- `hashall'
- same as `-h'.
+`\j'
+ The number of jobs currently managed by the shell.
- `histexpand'
- same as `-H'.
+`\l'
+ The basename of the shell's terminal device name.
- `history'
- Enable command history, as described in *Note Bash
- History Facilities::. This option is on by default in
- interactive shells.
+`\n'
+ A newline.
- `ignoreeof'
- the shell will not exit upon reading EOF.
+`\r'
+ A carriage return.
- `keyword'
- same as `-k'.
+`\s'
+ The name of the shell, the basename of `$0' (the portion following
+ the final slash).
- `monitor'
- same as `-m'.
+`\t'
+ The time, in 24-hour HH:MM:SS format.
- `noclobber'
- same as `-C'.
+`\T'
+ The time, in 12-hour HH:MM:SS format.
- `noexec'
- same as `-n'.
+`\@'
+ The time, in 12-hour am/pm format.
- `noglob'
- same as `-f'.
+`\A'
+ The time, in 24-hour HH:MM format.
- `notify'
- same as `-b'.
+`\u'
+ The username of the current user.
- `nounset'
- same as `-u'.
+`\v'
+ The version of Bash (e.g., 2.00)
- `onecmd'
- same as `-t'.
+`\V'
+ The release of Bash, version + patchlevel (e.g., 2.00.0)
- `physical'
- same as `-P'.
+`\w'
+ The current working directory, with `$HOME' abbreviated with a
+ tilde (uses the `$PROMPT_DIRTRIM' variable).
- `posix'
- change the behavior of Bash where the default operation
- differs from the POSIX 1003.2 standard to match the
- standard. This is intended to make Bash behave as a
- strict superset of that standard.
+`\W'
+ The basename of `$PWD', with `$HOME' abbreviated with a tilde.
- `privileged'
- same as `-p'.
+`\!'
+ The history number of this command.
- `verbose'
- same as `-v'.
+`\#'
+ The command number of this command.
- `vi'
- use a `vi'-style line editing interface.
+`\$'
+ If the effective uid is 0, `#', otherwise `$'.
- `xtrace'
- same as `-x'.
+`\NNN'
+ The character whose ASCII code is the octal value NNN.
- `-p'
- Turn on privileged mode. In this mode, the `$BASH_ENV' file
- is not processed, and shell functions are not inherited from
- the environment. This is enabled automatically on startup if
- the effective user (group) id is not equal to the real user
- (group) id. Turning this option off causes the effective user
- and group ids to be set to the real user and group ids.
+`\\'
+ A backslash.
- `-t'
- Exit after reading and executing one command.
+`\['
+ Begin a sequence of non-printing characters. This could be used to
+ embed a terminal control sequence into the prompt.
- `-u'
- Treat unset variables as an error when substituting.
+`\]'
+ End a sequence of non-printing characters.
- `-v'
- Print shell input lines as they are read.
+ The command number and the history number are usually different: the
+history number of a command is its position in the history list, which
+may include commands restored from the history file (*note Bash History
+Facilities::), while the command number is the position in the sequence
+of commands executed during the current shell session.
- `-x'
- Print commands and their arguments as they are executed.
+ After the string is decoded, it is expanded via parameter expansion,
+command substitution, arithmetic expansion, and quote removal, subject
+to the value of the `promptvars' shell option (*note Bash Builtins::).
- `-B'
- The shell will perform brace expansion (*note Brace
- Expansion::.). This option is on by default.
+\1f
+File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
- `-C'
- Disallow output redirection to existing files.
+6.10 The Restricted Shell
+=========================
- `-H'
- Enable `!' style history substitution (*note History
- Interaction::.). This flag is on by default for interactive
- shells.
+If Bash is started with the name `rbash', or the `--restricted' or `-r'
+option is supplied at invocation, the shell becomes restricted. A
+restricted shell is used to set up an environment more controlled than
+the standard shell. A restricted shell behaves identically to `bash'
+with the exception that the following are disallowed or not performed:
- `-P'
- If set, do not follow symbolic links when performing commands
- such as `cd' which change the current directory. The
- physical directory is used instead. By default, Bash follows
- the logical chain of directories when performing commands
- which change the current directory.
+ * Changing directories with the `cd' builtin.
- For example, if `/usr/sys' is a link to `/usr/local/sys' then:
- $ cd /usr/sys; echo $PWD
- /usr/sys
- $ cd ..; pwd
- /usr
+ * Setting or unsetting the values of the `SHELL', `PATH', `ENV', or
+ `BASH_ENV' variables.
- If `set -P' is on, then:
- $ cd /usr/sys; echo $PWD
- /usr/local/sys
- $ cd ..; pwd
- /usr/local
+ * Specifying command names containing slashes.
- `--'
- If no arguments follow this flag, then the positional
- parameters are unset. Otherwise, the positional parameters
- are set to the ARGUMENTS, even if some of them begin with a
- `-'.
+ * Specifying a filename containing a slash as an argument to the `.'
+ builtin command.
- `-'
- Signal the end of options, cause all remaining ARGUMENTS to
- be assigned to the positional parameters. The `-x' and `-v'
- options are turned off. If there are no arguments, the
- positional parameters remain unchanged.
+ * Specifying a filename containing a slash as an argument to the `-p'
+ option to the `hash' builtin command.
- Using `+' rather than `-' causes these flags to be turned off.
- The flags can also be used upon invocation of the shell. The
- current set of flags may be found in `$-'.
+ * Importing function definitions from the shell environment at
+ startup.
- The remaining N ARGUMENTS are positional parameters and are
- assigned, in order, to `$1', `$2', ... `$N'. If no arguments are
- given, all shell variables are printed.
+ * Parsing the value of `SHELLOPTS' from the shell environment at
+ startup.
-\1f
-File: bashref.info, Node: Bash Conditional Expressions, Next: Bash Variables, Prev: The Set Builtin, Up: Bash Features
+ * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
+ redirection operators.
-Bash Conditional Expressions
-============================
+ * Using the `exec' builtin to replace the shell with another command.
- Conditional expressions are used by the `test' and `[' builtins.
+ * Adding or deleting builtin commands with the `-f' and `-d' options
+ to the `enable' builtin.
- Expressions may be unary or binary. Unary expressions are often
-used to examine the status of a file. There are string operators and
-numeric comparison operators as well. Each operator and operand must
-be a separate argument. If FILE is of the form `/dev/fd/N', then file
-descriptor N is checked. Expressions are composed of the following
-primaries:
+ * Using the `enable' builtin command to enable disabled shell
+ builtins.
-`-b FILE'
- True if FILE exists and is a block special file.
+ * Specifying the `-p' option to the `command' builtin.
-`-c FILE'
- True if FILE exists and is a character special file.
+ * Turning off restricted mode with `set +r' or `set +o restricted'.
-`-d FILE'
- True if FILE exists and is a directory.
+ These restrictions are enforced after any startup files are read.
-`-e FILE'
- True if FILE exists.
+ When a command that is found to be a shell script is executed (*note
+Shell Scripts::), `rbash' turns off any restrictions in the shell
+spawned to execute the script.
-`-f FILE'
- True if FILE exists and is a regular file.
+\1f
+File: bashref.info, Node: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
+
+6.11 Bash POSIX Mode
+====================
-`-g FILE'
- True if FILE exists and is set-group-id.
+Starting Bash with the `--posix' command-line option or executing `set
+-o posix' while Bash is running will cause Bash to conform more closely
+to the POSIX standard by changing the behavior to match that specified
+by POSIX in areas where the Bash default differs.
-`-k FILE'
- True if FILE has its "sticky" bit set.
+ When invoked as `sh', Bash enters POSIX mode after reading the
+startup files.
-`-L FILE'
- True if FILE exists and is a symbolic link.
+ The following list is what's changed when `POSIX mode' is in effect:
-`-p FILE'
- True if FILE exists and is a named pipe.
+ 1. When a command in the hash table no longer exists, Bash will
+ re-search `$PATH' to find the new location. This is also
+ available with `shopt -s checkhash'.
-`-r FILE'
- True if FILE exists and is readable.
+ 2. The message printed by the job control code and builtins when a job
+ exits with a non-zero status is `Done(status)'.
-`-s FILE'
- True if FILE exists and has a size greater than zero.
+ 3. The message printed by the job control code and builtins when a job
+ is stopped is `Stopped(SIGNAME)', where SIGNAME is, for example,
+ `SIGTSTP'.
-`-S FILE'
- True if FILE exists and is a socket.
+ 4. The `bg' builtin uses the required format to describe each job
+ placed in the background, which does not include an indication of
+ whether the job is the current or previous job.
-`-t FD'
- True if FD is opened on a terminal.
+ 5. Reserved words appearing in a context where reserved words are
+ recognized do not undergo alias expansion.
-`-u FILE'
- True if FILE exists and its set-user-id bit is set.
+ 6. The POSIX `PS1' and `PS2' expansions of `!' to the history number
+ and `!!' to `!' are enabled, and parameter expansion is performed
+ on the values of `PS1' and `PS2' regardless of the setting of the
+ `promptvars' option.
-`-w FILE'
- True if FILE exists and is writable.
+ 7. The POSIX startup files are executed (`$ENV') rather than the
+ normal Bash files.
-`-x FILE'
- True if FILE exists and is executable.
+ 8. Tilde expansion is only performed on assignments preceding a
+ command name, rather than on all assignment statements on the line.
-`-O FILE'
- True if FILE exists and is owned by the effective user id.
+ 9. The default history file is `~/.sh_history' (this is the default
+ value of `$HISTFILE').
-`-G FILE'
- True if FILE exists and is owned by the effective group id.
+ 10. The output of `kill -l' prints all the signal names on a single
+ line, separated by spaces, without the `SIG' prefix.
-`FILE1 -nt FILE2'
- True if FILE1 is newer (according to modification date) than FILE2.
+ 11. The `kill' builtin does not accept signal names with a `SIG'
+ prefix.
-`FILE1 -ot FILE2'
- True if FILE1 is older than FILE2.
+ 12. Non-interactive shells exit if FILENAME in `.' FILENAME is not
+ found.
-`FILE1 -ef FILE2'
- True if FILE1 and FILE2 have the same device and inode numbers.
+ 13. Non-interactive shells exit if a syntax error in an arithmetic
+ expansion results in an invalid expression.
-`-o OPTNAME'
- True if shell option OPTNAME is enabled. The list of options
- appears in the description of the `-o' option to the `set' builtin
- (*note The Set Builtin::.).
+ 14. Redirection operators do not perform filename expansion on the word
+ in the redirection unless the shell is interactive.
-`-z STRING'
- True if the length of STRING is zero.
+ 15. Redirection operators do not perform word splitting on the word in
+ the redirection.
-`-n STRING'
-`STRING'
- True if the length of STRING is non-zero.
+ 16. Function names must be valid shell `name's. That is, they may not
+ contain characters other than letters, digits, and underscores, and
+ may not start with a digit. Declaring a function with an invalid
+ name causes a fatal syntax error in non-interactive shells.
-`STRING1 = STRING2'
- True if the strings are equal. `==' may be used in place of `='.
+ 17. POSIX special builtins are found before shell functions during
+ command lookup.
-`STRING1 != STRING2'
- True if the strings are not equal.
+ 18. If a POSIX special builtin returns an error status, a
+ non-interactive shell exits. The fatal errors are those listed in
+ the POSIX standard, and include things like passing incorrect
+ options, redirection errors, variable assignment errors for
+ assignments preceding the command name, and so on.
-`STRING1 < STRING2'
- True if STRING1 sorts before STRING2 lexicographically.
+ 19. If `CDPATH' is set, the `cd' builtin will not implicitly append
+ the current directory to it. This means that `cd' will fail if no
+ valid directory name can be constructed from any of the entries in
+ `$CDPATH', even if the a directory with the same name as the name
+ given as an argument to `cd' exists in the current directory.
-`STRING1 > STRING2'
- True if STRING1 sorts after STRING2 lexicographically.
+ 20. A non-interactive shell exits with an error status if a variable
+ assignment error occurs when no command name follows the assignment
+ statements. A variable assignment error occurs, for example, when
+ trying to assign a value to a readonly variable.
-`! EXPR'
- True if EXPR is false.
+ 21. A non-interactive shell exits with an error status if the iteration
+ variable in a `for' statement or the selection variable in a
+ `select' statement is a readonly variable.
-`EXPR1 -a EXPR2'
- True if both EXPR1 and EXPR2 are true.
+ 22. Process substitution is not available.
-`EXPR1 -o EXPR2'
- True if either EXPR1 and EXPR2 is true.
+ 23. Assignment statements preceding POSIX special builtins persist in
+ the shell environment after the builtin completes.
-`ARG1 OP ARG2'
- `OP' is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These
- arithmetic binary operators return true if ARG1 is equal to, not
- equal to, less than, less than or equal to, greater than, or
- greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
- positive or negative integers.
+ 24. Assignment statements preceding shell function calls persist in the
+ shell environment after the function returns, as if a POSIX
+ special builtin command had been executed.
- The Bash `test' and `[' builtins evaluate conditional expressions
-using a set of rules based on the number of arguments. These are the
-rules:
+ 25. The `export' and `readonly' builtin commands display their output
+ in the format required by POSIX.
-0 arguments
- The expression is false.
+ 26. The `trap' builtin displays signal names without the leading `SIG'.
-1 argument
- The expression is true if and only if the argument is not null.
+ 27. The `trap' builtin doesn't check the first argument for a possible
+ signal specification and revert the signal handling to the original
+ disposition if it is, unless that argument consists solely of
+ digits and is a valid signal number. If users want to reset the
+ handler for a given signal to the original disposition, they
+ should use `-' as the first argument.
-2 arguments
- If the first argument is `!', the expression is true if and only
- if the second argument is null. If the first argument is one of
- the listed unary operators, the expression is true if the unary
- test is true. If the first argument is not a legal unary
- operator, the expression is false.
+ 28. The `.' and `source' builtins do not search the current directory
+ for the filename argument if it is not found by searching `PATH'.
-3 arguments
- If the first argument is `!', the value is the negation of the
- two-argument test using the second and third arguments. If the
- second argument is one of the binary operators, the result of the
- expression is the result of the binary test using the first and
- third arguments as operands. If the first argument is exactly `('
- and the third argument is exactly `)', the result is the
- one-argument test of the second argument. Otherwise, the
- expression is false. The `-a' and `-o' operators are considered
- binary operators in this case.
+ 29. Subshells spawned to execute command substitutions inherit the
+ value of the `-e' option from the parent shell. When not in POSIX
+ mode, Bash clears the `-e' option in such subshells.
-4 arguments
- If the first argument is `!', the result is the negation of the
- three-argument expression composed of the remaining arguments.
- Otherwise, the expression is parsed and evaluated according to
- precedence. `-a' has a higher precedence than `-o'.
+ 30. Alias expansion is always enabled, even in non-interactive shells.
-5 or more arguments
- The expression is parsed and evaluated according to precedence,
- with `-a' having a higher precedence than `-o'.
+ 31. When the `alias' builtin displays alias definitions, it does not
+ display them with a leading `alias ' unless the `-p' option is
+ supplied.
-\1f
-File: bashref.info, Node: Bash Variables, Next: Shell Arithmetic, Prev: Bash Conditional Expressions, Up: Bash Features
+ 32. When the `set' builtin is invoked without options, it does not
+ display shell function names and definitions.
-Bash Variables
-==============
+ 33. When the `set' builtin is invoked without options, it displays
+ variable values without quotes, unless they contain shell
+ metacharacters, even if the result contains nonprinting characters.
- These variables are set or used by Bash, but other shells do not
-normally treat them specially.
+ 34. When the `cd' builtin is invoked in LOGICAL mode, and the pathname
+ constructed from `$PWD' and the directory name supplied as an
+ argument does not refer to an existing directory, `cd' will fail
+ instead of falling back to PHYSICAL mode.
-`BASH_ENV'
- If this variable is set when Bash is invoked to execute a shell
- script, its value is expanded and used as the name of a startup
- file to read before executing the script. *Note Bash Startup
- Files::.
+ 35. When the `pwd' builtin is supplied the `-P' option, it resets
+ `$PWD' to a pathname containing no symlinks.
-`TIMEFORMAT'
- The value of this parameter is used as a format string specifying
- how the timing information for pipelines prefixed with the `time'
- reserved word should be displayed. The `%' character introduces an
- escape sequence that is expanded to a time value or other
- information. The escape sequences and their meanings are as
- follows; the braces denote optional portions.
+ 36. The `pwd' builtin verifies that the value it prints is the same as
+ the current directory, even if it is not asked to check the file
+ system with the `-P' option.
- `%%'
- A literal `%'.
+ 37. When listing the history, the `fc' builtin does not include an
+ indication of whether or not a history entry has been modified.
- `%[P][l]R'
- The elapsed time in seconds.
+ 38. The default editor used by `fc' is `ed'.
- `%[P][l]U'
- The number of CPU seconds spent in user mode.
+ 39. The `type' and `command' builtins will not report a non-executable
+ file as having been found, though the shell will attempt to
+ execute such a file if it is the only so-named file found in
+ `$PATH'.
- `%[P][l]S'
- The number of CPU seconds spent in system mode.
+ 40. The `vi' editing mode will invoke the `vi' editor directly when
+ the `v' command is run, instead of checking `$VISUAL' and
+ `$EDITOR'.
- `%P'
- The CPU percentage, computed as (%U + %S) / %R.
+ 41. When the `xpg_echo' option is enabled, Bash does not attempt to
+ interpret any arguments to `echo' as options. Each argument is
+ displayed, after escape characters are converted.
- The optional P is a digit specifying the precision, the number of
- fractional digits after a decimal point. A value of 0 causes no
- decimal point or fraction to be output. At most three places
- after the decimal point may be specified; values of P greater than
- 3 are changed to 3. If P is not specified, the value 3 is used.
+ 42. The `ulimit' builtin uses a block size of 512 bytes for the `-c'
+ and `-f' options.
- The optional `l' specifies a longer format, including minutes, of
- the form MMmSS.FFs. The value of P determines whether or not the
- fraction is included.
- If this variable is not set, bash acts as if it had the value
- `$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS''.
- If the value is null, no timing information is displayed. A
- trailing newline is added when the format string is displayed.
+ There is other POSIX behavior that Bash does not implement by
+default even when in POSIX mode. Specifically:
-`HISTCONTROL'
- Set to a value of `ignorespace', it means don't enter lines which
- begin with a space or tab into the history list. Set to a value
- of `ignoredups', it means don't enter lines which match the last
- entered line. A value of `ignoreboth' combines the two options.
- Unset, or set to any other value than those above, means to save
- all lines on the history list.
+ 1. The `fc' builtin checks `$EDITOR' as a program to edit history
+ entries if `FCEDIT' is unset, rather than defaulting directly to
+ `ed'. `fc' uses `ed' if `EDITOR' is unset.
-`HISTIGNORE'
- A colon-separated list of patterns used to decide which command
- lines should be saved on the history list. Each pattern is
- anchored at the beginning of the line and must fully specify the
- line (no implicit `*' is appended). Each pattern is tested
- against the line after the checks specified by `HISTCONTROL' are
- applied. In addition to the normal shell pattern matching
- characters, `&' matches the previous history line. `&' may be
- escaped using a backslash. The backslash is removed before
- attempting a match.
+ 2. As noted above, Bash requires the `xpg_echo' option to be enabled
+ for the `echo' builtin to be fully conformant.
- `HISTIGNORE' subsumes the function of `HISTCONTROL'. A pattern of
- `&' is identical to `ignoredups', and a pattern of `[ ]*' is
- identical to `ignorespace'. Combining these two patterns,
- separating them with a colon, provides the functionality of
- `ignoreboth'.
-`HISTFILE'
- The name of the file to which the command history is saved. The
- default is `~/.bash_history'.
+ Bash can be configured to be POSIX-conformant by default, by
+specifying the `--enable-strict-posix-default' to `configure' when
+building (*note Optional Features::).
-`HISTSIZE'
- If set, this is the maximum number of commands to remember in the
- history.
+\1f
+File: bashref.info, Node: Job Control, Next: Command Line Editing, Prev: Bash Features, Up: Top
-`HISTFILESIZE'
- The maximum number of lines contained in the history file. When
- this variable is assigned a value, the history file is truncated,
- if necessary, to contain no more than that number of lines. The
- default value is 500. The history file is also truncated to this
- size after writing it when an interactive shell exits.
+7 Job Control
+*************
-`histchars'
- Up to three characters which control history expansion, quick
- substitution, and tokenization (*note History Interaction::.).
- The first character is the "history-expansion-char", that is, the
- character which signifies the start of a history expansion,
- normally `!'. The second character is the character which
- signifies `quick substitution' when seen as the first character on
- a line, normally `^'. The optional third character is the
- character which signifies the remainder of the line is a comment,
- when found as the first character of a word, usually `#'. The
- history comment character causes history substitution to be
- skipped for the remaining words on the line. It does not
- necessarily cause the shell parser to treat the rest of the line
- as a comment.
+This chapter discusses what job control is, how it works, and how Bash
+allows you to access its facilities.
-`HISTCMD'
- The history number, or index in the history list, of the current
- command. If `HISTCMD' is unset, it loses its special properties,
- even if it is subsequently reset.
+* Menu:
-`HOSTFILE'
- Contains the name of a file in the same format as `/etc/hosts' that
- should be read when the shell needs to complete a hostname. You
- can change the file interactively; the next time you attempt to
- complete a hostname, Bash will add the contents of the new file to
- the already existing database.
+* Job Control Basics:: How job control works.
+* Job Control Builtins:: Bash builtin commands used to interact
+ with job control.
+* Job Control Variables:: Variables Bash uses to customize job
+ control.
-`MAILCHECK'
- How often (in seconds) that the shell should check for mail in the
- files specified in `MAILPATH'.
+\1f
+File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
-`PROMPT_COMMAND'
- If present, this contains a string which is a command to execute
- before the printing of each primary prompt (`$PS1').
+7.1 Job Control Basics
+======================
-`UID'
- The numeric real user id of the current user.
+Job control refers to the ability to selectively stop (suspend) the
+execution of processes and continue (resume) their execution at a later
+point. A user typically employs this facility via an interactive
+interface supplied jointly by the system's terminal driver and Bash.
-`EUID'
- The numeric effective user id of the current user.
+ The shell associates a JOB with each pipeline. It keeps a table of
+currently executing jobs, which may be listed with the `jobs' command.
+When Bash starts a job asynchronously, it prints a line that looks like:
+ [1] 25647
+ indicating that this job is job number 1 and that the process ID of
+the last process in the pipeline associated with this job is 25647.
+All of the processes in a single pipeline are members of the same job.
+Bash uses the JOB abstraction as the basis for job control.
-`GROUPS'
- An array variable containing the list of groups of which the
- current user is a member.
+ To facilitate the implementation of the user interface to job
+control, the operating system maintains the notion of a current terminal
+process group ID. Members of this process group (processes whose
+process group ID is equal to the current terminal process group ID)
+receive keyboard-generated signals such as `SIGINT'. These processes
+are said to be in the foreground. Background processes are those whose
+process group ID differs from the terminal's; such processes are immune
+to keyboard-generated signals. Only foreground processes are allowed
+to read from or write to the terminal. Background processes which
+attempt to read from (write to) the terminal are sent a `SIGTTIN'
+(`SIGTTOU') signal by the terminal driver, which, unless caught,
+suspends the process.
-`PPID'
- The process id of the shell's parent process.
+ If the operating system on which Bash is running supports job
+control, Bash contains facilities to use it. Typing the SUSPEND
+character (typically `^Z', Control-Z) while a process is running causes
+that process to be stopped and returns control to Bash. Typing the
+DELAYED SUSPEND character (typically `^Y', Control-Y) causes the
+process to be stopped when it attempts to read input from the terminal,
+and control to be returned to Bash. The user then manipulates the
+state of this job, using the `bg' command to continue it in the
+background, the `fg' command to continue it in the foreground, or the
+`kill' command to kill it. A `^Z' takes effect immediately, and has
+the additional side effect of causing pending output and typeahead to
+be discarded.
-`HOSTNAME'
- The name of the current host.
+ There are a number of ways to refer to a job in the shell. The
+character `%' introduces a job specification (JOBSPEC).
+
+ Job number `n' may be referred to as `%n'. The symbols `%%' and
+`%+' refer to the shell's notion of the current job, which is the last
+job stopped while it was in the foreground or started in the background.
+A single `%' (with no accompanying job specification) also refers to
+the current job. The previous job may be referenced using `%-'. If
+there is only a single job, `%+' and `%-' can both be used to refer to
+that job. In output pertaining to jobs (e.g., the output of the `jobs'
+command), the current job is always flagged with a `+', and the
+previous job with a `-'.
+
+ A job may also be referred to using a prefix of the name used to
+start it, or using a substring that appears in its command line. For
+example, `%ce' refers to a stopped `ce' job. Using `%?ce', on the other
+hand, refers to any job containing the string `ce' in its command line.
+If the prefix or substring matches more than one job, Bash reports an
+error.
-`HOSTTYPE'
- A string describing the machine Bash is running on.
+ Simply naming a job can be used to bring it into the foreground:
+`%1' is a synonym for `fg %1', bringing job 1 from the background into
+the foreground. Similarly, `%1 &' resumes job 1 in the background,
+equivalent to `bg %1'
-`OSTYPE'
- A string describing the operating system Bash is running on.
+ The shell learns immediately whenever a job changes state.
+Normally, Bash waits until it is about to print a prompt before
+reporting changes in a job's status so as to not interrupt any other
+output. If the `-b' option to the `set' builtin is enabled, Bash
+reports such changes immediately (*note The Set Builtin::). Any trap
+on `SIGCHLD' is executed for each child process that exits.
+
+ If an attempt to exit Bash is made while jobs are stopped, (or
+running, if the `checkjobs' option is enabled - see *note The Shopt
+Builtin::), the shell prints a warning message, and if the `checkjobs'
+option is enabled, lists the jobs and their statuses. The `jobs'
+command may then be used to inspect their status. If a second attempt
+to exit is made without an intervening command, Bash does not print
+another warning, and any stopped jobs are terminated.
-`MACHTYPE'
- A string that fully describes the system type on which Bash is
- executing, in the standard GNU CPU-COMPANY-SYSTEM format.
+\1f
+File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
-`SHELLOPTS'
- A colon-separated list of enabled shell options. Each word in the
- list is a valid argument for the `-o' option to the `set' builtin
- command (*note The Set Builtin::.). The options appearing in
- `SHELLOPTS' are those reported as `on' by `set -o'. If this
- variable is in the environment when Bash starts up, each shell
- option in the list will be enabled before reading any startup
- files. This variable is readonly.
+7.2 Job Control Builtins
+========================
-`FIGNORE'
- A colon-separated list of suffixes to ignore when performing
- filename completion. A file name whose suffix matches one of the
- entries in `FIGNORE' is excluded from the list of matched file
- names. A sample value is `.o:~'
+`bg'
+ bg [JOBSPEC ...]
+ Resume each suspended job JOBSPEC in the background, as if it had
+ been started with `&'. If JOBSPEC is not supplied, the current
+ job is used. The return status is zero unless it is run when job
+ control is not enabled, or, when run with job control enabled, any
+ JOBSPEC was not found or specifies a job that was started without
+ job control.
-`GLOBIGNORE'
- A colon-separated list of patterns defining the set of filenames to
- be ignored by filename expansion. If a filename matched by a
- filename expansion pattern also matches one of the patterns in
- `GLOBIGNORE', it is removed from the list of matches.
+`fg'
+ fg [JOBSPEC]
+ Resume the job JOBSPEC in the foreground and make it the current
+ job. If JOBSPEC is not supplied, the current job is used. The
+ return status is that of the command placed into the foreground,
+ or non-zero if run when job control is disabled or, when run with
+ job control enabled, JOBSPEC does not specify a valid job or
+ JOBSPEC specifies a job that was started without job control.
-`DIRSTACK'
- An array variable (*note Arrays::.) containing the current
- contents of the directory stack. Directories appear in the stack
- in the order they are displayed by the `dirs' builtin. Assigning
- to members of this array variable may be used to modify
- directories already in the stack, but the `pushd' and `popd'
- builtins must be used to add and remove directories. Assignment
- to this variable will not change the current directory. If
- `DIRSTACK' is unset, it loses its special properties, even if it
- is subsequently reset.
+`jobs'
+ jobs [-lnprs] [JOBSPEC]
+ jobs -x COMMAND [ARGUMENTS]
-`PIPESTATUS'
- An array variable (*note Arrays::.) containing a list of exit
- status values from the processes in the most-recently-executed
- foreground pipeline (which may contain only a single command).
+ The first form lists the active jobs. The options have the
+ following meanings:
-`INPUTRC'
- The name of the Readline startup file, overriding the default of
- `~/.inputrc'.
+ `-l'
+ List process IDs in addition to the normal information.
-`BASH'
- The full filename used to execute the current instance of Bash.
+ `-n'
+ Display information only about jobs that have changed status
+ since the user was last notified of their status.
-`BASH_VERSION'
- The version number of the current instance of Bash.
+ `-p'
+ List only the process ID of the job's process group leader.
-`BASH_VERSINFO'
- An array variable whose members hold version information for this
- instance of Bash. The values assigned to the array members are as
- follows:
+ `-r'
+ Restrict output to running jobs.
- `BASH_VERSINFO[0]'
- The major version number (the RELEASE).
+ `-s'
+ Restrict output to stopped jobs.
- `BASH_VERSINFO[1]'
- The minor version number (the VERSION).
+ If JOBSPEC is given, output is restricted to information about
+ that job. If JOBSPEC is not supplied, the status of all jobs is
+ listed.
- `BASH_VERSINFO[2]'
- The patch level.
+ If the `-x' option is supplied, `jobs' replaces any JOBSPEC found
+ in COMMAND or ARGUMENTS with the corresponding process group ID,
+ and executes COMMAND, passing it ARGUMENTs, returning its exit
+ status.
- `BASH_VERSINFO[3]'
- The build version.
+`kill'
+ kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] JOBSPEC or PID
+ kill -l [EXIT_STATUS]
+ Send a signal specified by SIGSPEC or SIGNUM to the process named
+ by job specification JOBSPEC or process ID PID. SIGSPEC is either
+ a case-insensitive signal name such as `SIGINT' (with or without
+ the `SIG' prefix) or a signal number; SIGNUM is a signal number.
+ If SIGSPEC and SIGNUM are not present, `SIGTERM' is used. The
+ `-l' option lists the signal names. If any arguments are supplied
+ when `-l' is given, the names of the signals corresponding to the
+ arguments are listed, and the return status is zero. EXIT_STATUS
+ is a number specifying a signal number or the exit status of a
+ process terminated by a signal. The return status is zero if at
+ least one signal was successfully sent, or non-zero if an error
+ occurs or an invalid option is encountered.
- `BASH_VERSINFO[4]'
- The release status (e.g., BETA1).
+`wait'
+ wait [JOBSPEC or PID ...]
+ Wait until the child process specified by each process ID PID or
+ job specification JOBSPEC exits and return the exit status of the
+ last command waited for. If a job spec is given, all processes in
+ the job are waited for. If no arguments are given, all currently
+ active child processes are waited for, and the return status is
+ zero. If neither JOBSPEC nor PID specifies an active child process
+ of the shell, the return status is 127.
- `BASH_VERSINFO[5]'
- The value of `MACHTYPE'.
+`disown'
+ disown [-ar] [-h] [JOBSPEC ...]
+ Without options, each JOBSPEC is removed from the table of active
+ jobs. If the `-h' option is given, the job is not removed from
+ the table, but is marked so that `SIGHUP' is not sent to the job
+ if the shell receives a `SIGHUP'. If JOBSPEC is not present, and
+ neither the `-a' nor `-r' option is supplied, the current job is
+ used. If no JOBSPEC is supplied, the `-a' option means to remove
+ or mark all jobs; the `-r' option without a JOBSPEC argument
+ restricts operation to running jobs.
-`SHLVL'
- Incremented by one each time a new instance of Bash is started.
- This is intended to be a count of how deeply your Bash shells are
- nested.
+`suspend'
+ suspend [-f]
+ Suspend the execution of this shell until it receives a `SIGCONT'
+ signal. A login shell cannot be suspended; the `-f' option can be
+ used to override this and force the suspension.
-`OPTERR'
- If set to the value 1, Bash displays error messages generated by
- the `getopts' builtin command.
-`LANG'
- Used to determine the locale category for any category not
- specifically selected with a variable starting with `LC_'.
+ When job control is not active, the `kill' and `wait' builtins do
+not accept JOBSPEC arguments. They must be supplied process IDs.
-`LC_ALL'
- This variable overrides the value of `LANG' and any other `LC_'
- variable specifying a locale category.
+\1f
+File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
-`LC_COLLATE'
- This variable determines the collation order used when sorting the
- results of filename expansion (*note Filename Expansion::.).
+7.3 Job Control Variables
+=========================
-`LC_MESSAGES'
- This variable determines the locale used to translate double-quoted
- strings preceded by a `$' (*note Locale Translation::.).
+`auto_resume'
+ This variable controls how the shell interacts with the user and
+ job control. If this variable exists then single word simple
+ commands without redirections are treated as candidates for
+ resumption of an existing job. There is no ambiguity allowed; if
+ there is more than one job beginning with the string typed, then
+ the most recently accessed job will be selected. The name of a
+ stopped job, in this context, is the command line used to start
+ it. If this variable is set to the value `exact', the string
+ supplied must match the name of a stopped job exactly; if set to
+ `substring', the string supplied needs to match a substring of the
+ name of a stopped job. The `substring' value provides
+ functionality analogous to the `%?' job ID (*note Job Control
+ Basics::). If set to any other value, the supplied string must be
+ a prefix of a stopped job's name; this provides functionality
+ analogous to the `%' job ID.
-`IGNOREEOF'
- Controls the action of the shell on receipt of an `EOF' character
- as the sole input. If set, then the value of it is the number of
- consecutive `EOF' characters that can be read as the first
- character on an input line before the shell will exit. If the
- variable exists but does not have a numeric value (or has no
- value) then the default is 10. If the variable does not exist,
- then `EOF' signifies the end of input to the shell. This is only
- in effect for interactive shells.
\1f
-File: bashref.info, Node: Shell Arithmetic, Next: Arrays, Prev: Bash Variables, Up: Bash Features
+File: bashref.info, Node: Command Line Editing, Next: Using History Interactively, Prev: Job Control, Up: Top
-Shell Arithmetic
-================
+8 Command Line Editing
+**********************
+
+This chapter describes the basic features of the GNU command line
+editing interface. Command line editing is provided by the Readline
+library, which is used by several different programs, including Bash.
+Command line editing is enabled by default when using an interactive
+shell, unless the `--noediting' option is supplied at shell invocation.
+Line editing is also used when using the `-e' option to the `read'
+builtin command (*note Bash Builtins::). By default, the line editing
+commands are similar to those of emacs. A vi-style line editing
+interface is also available. Line editing can be enabled at any time
+using the `-o emacs' or `-o vi' options to the `set' builtin command
+(*note The Set Builtin::), or disabled using the `+o emacs' or `+o vi'
+options to `set'.
* Menu:
-* Arithmetic Evaluation:: How shell arithmetic works.
-* Arithmetic Expansion:: How to use arithmetic in shell expansions.
-* Arithmetic Builtins:: Builtin commands that use shell arithmetic.
+* Introduction and Notation:: Notation used in this text.
+* Readline Interaction:: The minimum set of commands for editing a line.
+* Readline Init File:: Customizing Readline from a user's view.
+* Bindable Readline Commands:: A description of most of the Readline commands
+ available for binding
+* Readline vi Mode:: A short description of how to make Readline
+ behave like the vi editor.
- Bash includes several mechanisms to evaluate arithmetic expressions
-and display the result or use it as part of a command.
+* Programmable Completion:: How to specify the possible completions for
+ a specific command.
+* Programmable Completion Builtins:: Builtin commands to specify how to
+ complete arguments for a particular command.
\1f
-File: bashref.info, Node: Arithmetic Evaluation, Next: Arithmetic Expansion, Up: Shell Arithmetic
+File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
-Arithmetic Evaluation
----------------------
+8.1 Introduction to Line Editing
+================================
- The shell allows arithmetic expressions to be evaluated, as one of
-the shell expansions or by the `let' builtin.
+The following paragraphs describe the notation used to represent
+keystrokes.
- Evaluation is done in long integers with no check for overflow,
-though division by 0 is trapped and flagged as an error. The following
-list of operators is grouped into levels of equal-precedence operators.
-The levels are listed in order of decreasing precedence.
+ The text `C-k' is read as `Control-K' and describes the character
+produced when the <k> key is pressed while the Control key is depressed.
+
+ The text `M-k' is read as `Meta-K' and describes the character
+produced when the Meta key (if you have one) is depressed, and the <k>
+key is pressed. The Meta key is labeled <ALT> on many keyboards. On
+keyboards with two keys labeled <ALT> (usually to either side of the
+space bar), the <ALT> on the left side is generally set to work as a
+Meta key. The <ALT> key on the right may also be configured to work as
+a Meta key or may be configured as some other modifier, such as a
+Compose key for typing accented characters.
+
+ If you do not have a Meta or <ALT> key, or another key working as a
+Meta key, the identical keystroke can be generated by typing <ESC>
+_first_, and then typing <k>. Either process is known as "metafying"
+the <k> key.
+
+ The text `M-C-k' is read as `Meta-Control-k' and describes the
+character produced by "metafying" `C-k'.
+
+ In addition, several keys have their own names. Specifically,
+<DEL>, <ESC>, <LFD>, <SPC>, <RET>, and <TAB> all stand for themselves
+when seen in this text, or in an init file (*note Readline Init File::).
+If your keyboard lacks a <LFD> key, typing <C-j> will produce the
+desired character. The <RET> key may be labeled <Return> or <Enter> on
+some keyboards.
-`- +'
- unary minus and plus
+\1f
+File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
-`! ~'
- logical and bitwise negation
+8.2 Readline Interaction
+========================
-`* / %'
- multiplication, division, remainder
+Often during an interactive session you type in a long line of text,
+only to notice that the first word on the line is misspelled. The
+Readline library gives you a set of commands for manipulating the text
+as you type it in, allowing you to just fix your typo, and not forcing
+you to retype the majority of the line. Using these editing commands,
+you move the cursor to the place that needs correction, and delete or
+insert the text of the corrections. Then, when you are satisfied with
+the line, you simply press <RET>. You do not have to be at the end of
+the line to press <RET>; the entire line is accepted regardless of the
+location of the cursor within the line.
-`+ -'
- addition, subtraction
+* Menu:
-`<< >>'
- left and right bitwise shifts
+* Readline Bare Essentials:: The least you need to know about Readline.
+* Readline Movement Commands:: Moving about the input line.
+* Readline Killing Commands:: How to delete text, and how to get it back!
+* Readline Arguments:: Giving numeric arguments to commands.
+* Searching:: Searching through previous lines.
-`<= >= < >'
- comparison
+\1f
+File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
-`== !='
- equality and inequality
+8.2.1 Readline Bare Essentials
+------------------------------
-`&'
- bitwise AND
+In order to enter characters into the line, simply type them. The typed
+character appears where the cursor was, and then the cursor moves one
+space to the right. If you mistype a character, you can use your erase
+character to back up and delete the mistyped character.
-`^'
- bitwise exclusive OR
+ Sometimes you may mistype a character, and not notice the error
+until you have typed several other characters. In that case, you can
+type `C-b' to move the cursor to the left, and then correct your
+mistake. Afterwards, you can move the cursor to the right with `C-f'.
-`|'
- bitwise OR
+ When you add text in the middle of a line, you will notice that
+characters to the right of the cursor are `pushed over' to make room
+for the text that you have inserted. Likewise, when you delete text
+behind the cursor, characters to the right of the cursor are `pulled
+back' to fill in the blank space created by the removal of the text. A
+list of the bare essentials for editing the text of an input line
+follows.
-`&&'
- logical AND
+`C-b'
+ Move back one character.
-`||'
- logical OR
+`C-f'
+ Move forward one character.
-`expr ? expr : expr'
- conditional evaluation
+<DEL> or <Backspace>
+ Delete the character to the left of the cursor.
-`= *= /= %= += -= <<= >>= &= ^= |='
- assignment
+`C-d'
+ Delete the character underneath the cursor.
- Shell variables are allowed as operands; parameter expansion is
-performed before the expression is evaluated. The value of a parameter
-is coerced to a long integer within an expression. A shell variable
-need not have its integer attribute turned on to be used in an
-expression.
+Printing characters
+ Insert the character into the line at the cursor.
- Constants with a leading 0 are interpreted as octal numbers. A
-leading `0x' or `0X' denotes hexadecimal. Otherwise, numbers take the
-form [BASE`#']N, where BASE is a decimal number between 2 and 64
-representing the arithmetic base, and N is a number in that base. If
-BASE is omitted, then base 10 is used. The digits greater than 9 are
-represented by the lowercase letters, the uppercase letters, `_', and
-`@', in that order. If BASE is less than or equal to 36, lowercase and
-uppercase letters may be used interchangably to represent numbers
-between 10 and 35.
+`C-_' or `C-x C-u'
+ Undo the last editing command. You can undo all the way back to an
+ empty line.
- Operators are evaluated in order of precedence. Sub-expressions in
-parentheses are evaluated first and may override the precedence rules
-above.
+(Depending on your configuration, the <Backspace> key be set to delete
+the character to the left of the cursor and the <DEL> key set to delete
+the character underneath the cursor, like `C-d', rather than the
+character to the left of the cursor.)
\1f
-File: bashref.info, Node: Arithmetic Expansion, Next: Arithmetic Builtins, Prev: Arithmetic Evaluation, Up: Shell Arithmetic
+File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
-Arithmetic Expansion
---------------------
+8.2.2 Readline Movement Commands
+--------------------------------
- Arithmetic expansion allows the evaluation of an arithmetic
-expression and the substitution of the result. The format for
-arithmetic expansion is:
+The above table describes the most basic keystrokes that you need in
+order to do editing of the input line. For your convenience, many
+other commands have been added in addition to `C-b', `C-f', `C-d', and
+<DEL>. Here are some commands for moving more rapidly about the line.
- $(( EXPRESSION ))
+`C-a'
+ Move to the start of the line.
- The expression is treated as if it were within double quotes, but a
-double quote inside the braces or parentheses is not treated specially.
-All tokens in the expression undergo parameter expansion, command
-substitution, and quote removal. Arithmetic substitutions may be
-nested.
+`C-e'
+ Move to the end of the line.
- The evaluation is performed according to the rules listed above. If
-the expression is invalid, Bash prints a message indicating failure and
-no substitution occurs.
+`M-f'
+ Move forward a word, where a word is composed of letters and
+ digits.
-\1f
-File: bashref.info, Node: Arithmetic Builtins, Prev: Arithmetic Expansion, Up: Shell Arithmetic
+`M-b'
+ Move backward a word.
-Arithmetic Builtins
--------------------
+`C-l'
+ Clear the screen, reprinting the current line at the top.
-`let'
- let EXPRESSION [EXPRESSION]
- The `let' builtin allows arithmetic to be performed on shell
- variables. Each EXPRESSION is evaluated according to the rules
- given previously (*note Arithmetic Evaluation::.). If the last
- EXPRESSION evaluates to 0, `let' returns 1; otherwise 0 is
- returned.
+ Notice how `C-f' moves forward a character, while `M-f' moves
+forward a word. It is a loose convention that control keystrokes
+operate on characters while meta keystrokes operate on words.
\1f
-File: bashref.info, Node: Arrays, Next: Printing a Prompt, Prev: Shell Arithmetic, Up: Bash Features
-
-Arrays
-======
+File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
- Bash provides one-dimensional array variables. Any variable may be
-used as an array; the `declare' builtin will explicitly declare an
-array. There is no maximum limit on the size of an array, nor any
-requirement that members be indexed or assigned contiguously. Arrays
-are zero-based.
+8.2.3 Readline Killing Commands
+-------------------------------
- An array is created automatically if any variable is assigned to
-using the syntax
- name[SUBSCRIPT]=VALUE
+"Killing" text means to delete the text from the line, but to save it
+away for later use, usually by "yanking" (re-inserting) it back into
+the line. (`Cut' and `paste' are more recent jargon for `kill' and
+`yank'.)
-The SUBSCRIPT is treated as an arithmetic expression that must evaluate
-to a number greater than or equal to zero. To explicitly declare an
-array, use
- declare -a NAME
+ If the description for a command says that it `kills' text, then you
+can be sure that you can get the text back in a different (or the same)
+place later.
-The syntax
- declare -a NAME[SUBSCRIPT]
+ When you use a kill command, the text is saved in a "kill-ring".
+Any number of consecutive kills save all of the killed text together, so
+that when you yank it back, you get it all. The kill ring is not line
+specific; the text that you killed on a previously typed line is
+available to be yanked back later, when you are typing another line.
-is also accepted; the SUBSCRIPT is ignored. Attributes may be
-specified for an array variable using the `declare' and `readonly'
-builtins. Each attribute applies to all members of an array.
+ Here is the list of commands for killing text.
- Arrays are assigned to using compound assignments of the form
- name=(value1 ... valueN)
+`C-k'
+ Kill the text from the current cursor position to the end of the
+ line.
-where each VALUE is of the form `[[SUBSCRIPT]=]'STRING. If the
-optional subscript is supplied, that index is assigned to; otherwise
-the index of the element assigned is the last index assigned to by the
-statement plus one. Indexing starts at zero. This syntax is also
-accepted by the `declare' builtin. Individual array elements may be
-assigned to using the `name['SUBSCRIPT`]='VALUE syntax introduced above.
+`M-d'
+ Kill from the cursor to the end of the current word, or, if between
+ words, to the end of the next word. Word boundaries are the same
+ as those used by `M-f'.
- Any element of an array may be referenced using
-`${name['SUBSCRIPT`]}'. The braces are required to avoid conflicts
-with the shell's filename expansion operators. If the SUBSCRIPT is `@'
-or `*', the word expands to all members of the array NAME. These
-subscripts differ only when the word appears within double quotes. If
-the word is double-quoted, `${name[*]}' expands to a single word with
-the value of each array member separated by the first character of the
-`IFS' variable, and `${name[@]}' expands each element of NAME to a
-separate word. When there are no array members, `${name[@]}' expands
-to nothing. This is analogous to the expansion of the special
-parameters `@' and `*'. `${#name['SUBSCRIPT`]}' expands to the length
-of `${name['SUBSCRIPT`]}'. If SUBSCRIPT is `@' or `*', the expansion
-is the number of elements in the array. Referencing an array variable
-without a subscript is equivalent to referencing element zero.
+`M-<DEL>'
+ Kill from the cursor the start of the current word, or, if between
+ words, to the start of the previous word. Word boundaries are the
+ same as those used by `M-b'.
- The `unset' builtin is used to destroy arrays. `unset'
-NAME[SUBSCRIPT] destroys the array element at index SUBSCRIPT. `unset'
-NAME, where NAME is an array, removes the entire array. A subscript of
-`*' or `@' also removes the entire array.
+`C-w'
+ Kill from the cursor to the previous whitespace. This is
+ different than `M-<DEL>' because the word boundaries differ.
- The `declare', `local', and `readonly' builtins each accept a `-a'
-option to specify an array. The `read' builtin accepts a `-a' option
-to assign a list of words read from the standard input to an array, and
-can read values from the standard input into individual array elements.
-The `set' and `declare' builtins display array values in a way that
-allows them to be reused as input.
-\1f
-File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: Arrays, Up: Bash Features
+ Here is how to "yank" the text back into the line. Yanking means to
+copy the most-recently-killed text from the kill buffer.
-Controlling the Prompt
-======================
+`C-y'
+ Yank the most recently killed text back into the buffer at the
+ cursor.
- The value of the variable `PROMPT_COMMAND' is examined just before
-Bash prints each primary prompt. If it is set and non-null, then the
-value is executed just as if you had typed it on the command line.
+`M-y'
+ Rotate the kill-ring, and yank the new top. You can only do this
+ if the prior command is `C-y' or `M-y'.
- In addition, the following table describes the special characters
-which can appear in the prompt variables:
+\1f
+File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
-`\a'
- a bell character.
+8.2.4 Readline Arguments
+------------------------
-`\d'
- the date, in "Weekday Month Date" format (e.g., "Tue May 26").
+You can pass numeric arguments to Readline commands. Sometimes the
+argument acts as a repeat count, other times it is the sign of the
+argument that is significant. If you pass a negative argument to a
+command which normally acts in a forward direction, that command will
+act in a backward direction. For example, to kill text back to the
+start of the line, you might type `M-- C-k'.
-`\e'
- an escape character.
+ The general way to pass numeric arguments to a command is to type
+meta digits before the command. If the first `digit' typed is a minus
+sign (`-'), then the sign of the argument will be negative. Once you
+have typed one meta digit to get the argument started, you can type the
+remainder of the digits, and then the command. For example, to give
+the `C-d' command an argument of 10, you could type `M-1 0 C-d', which
+will delete the next ten characters on the input line.
-`\h'
- the hostname, up to the first `.'.
+\1f
+File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
-`\H'
- the hostname.
+8.2.5 Searching for Commands in the History
+-------------------------------------------
-`\n'
- newline.
+Readline provides commands for searching through the command history
+(*note Bash History Facilities::) for lines containing a specified
+string. There are two search modes: "incremental" and
+"non-incremental".
-`\s'
- the name of the shell, the basename of `$0' (the portion following
- the final slash).
+ Incremental searches begin before the user has finished typing the
+search string. As each character of the search string is typed,
+Readline displays the next entry from the history matching the string
+typed so far. An incremental search requires only as many characters
+as needed to find the desired history entry. To search backward in the
+history for a particular string, type `C-r'. Typing `C-s' searches
+forward through the history. The characters present in the value of
+the `isearch-terminators' variable are used to terminate an incremental
+search. If that variable has not been assigned a value, the <ESC> and
+`C-J' characters will terminate an incremental search. `C-g' will
+abort an incremental search and restore the original line. When the
+search is terminated, the history entry containing the search string
+becomes the current line.
+
+ To find other matching entries in the history list, type `C-r' or
+`C-s' as appropriate. This will search backward or forward in the
+history for the next entry matching the search string typed so far.
+Any other key sequence bound to a Readline command will terminate the
+search and execute that command. For instance, a <RET> will terminate
+the search and accept the line, thereby executing the command from the
+history list. A movement command will terminate the search, make the
+last line found the current line, and begin editing.
+
+ Readline remembers the last incremental search string. If two
+`C-r's are typed without any intervening characters defining a new
+search string, any remembered search string is used.
-`\t'
- the time, in 24-hour HH:MM:SS format.
+ Non-incremental searches read the entire search string before
+starting to search for matching history lines. The search string may be
+typed by the user or be part of the contents of the current line.
-`\T'
- the time, in 12-hour HH:MM:SS format.
+\1f
+File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
-`\@'
- the time, in 12-hour am/pm format.
+8.3 Readline Init File
+======================
-`\v'
- the version of Bash (e.g., 2.00)
+Although the Readline library comes with a set of Emacs-like
+keybindings installed by default, it is possible to use a different set
+of keybindings. Any user can customize programs that use Readline by
+putting commands in an "inputrc" file, conventionally in his home
+directory. The name of this file is taken from the value of the shell
+variable `INPUTRC'. If that variable is unset, the default is
+`~/.inputrc'. If that file does not exist or cannot be read, the
+ultimate default is `/etc/inputrc'.
-`\V'
- the release of Bash, version + patchlevel (e.g., 2.00.0)
+ When a program which uses the Readline library starts up, the init
+file is read, and the key bindings are set.
-`\w'
- the current working directory.
+ In addition, the `C-x C-r' command re-reads this init file, thus
+incorporating any changes that you might have made to it.
-`\W'
- the basename of `$PWD'.
+* Menu:
-`\u'
- your username.
+* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
-`\!'
- the history number of this command.
+* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
-`\#'
- the command number of this command.
+* Sample Init File:: An example inputrc file.
-`\$'
- if the effective uid is 0, `#', otherwise `$'.
+\1f
+File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
-`\nnn'
- the character corresponding to the octal number `nnn'.
+8.3.1 Readline Init File Syntax
+-------------------------------
-`\\'
- a backslash.
+There are only a few basic constructs allowed in the Readline init
+file. Blank lines are ignored. Lines beginning with a `#' are
+comments. Lines beginning with a `$' indicate conditional constructs
+(*note Conditional Init Constructs::). Other lines denote variable
+settings and key bindings.
-`\['
- begin a sequence of non-printing characters. This could be used to
- embed a terminal control sequence into the prompt.
+Variable Settings
+ You can modify the run-time behavior of Readline by altering the
+ values of variables in Readline using the `set' command within the
+ init file. The syntax is simple:
-`\]'
- end a sequence of non-printing characters.
+ set VARIABLE VALUE
-\1f
-File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
+ Here, for example, is how to change from the default Emacs-like
+ key binding to use `vi' line editing commands:
-The Restricted Shell
-====================
+ set editing-mode vi
- If Bash is started with the name `rbash', or the `--restricted'
-option is supplied at invocation, the shell becomes restricted. A
-restricted shell is used to set up an environment more controlled than
-the standard shell. A restricted shell behaves identically to `bash'
-with the exception that the following are disallowed:
- * Changing directories with the `cd' builtin.
+ Variable names and values, where appropriate, are recognized
+ without regard to case. Unrecognized variable names are ignored.
- * Setting or unsetting the values of the `SHELL' or `PATH' variables.
+ Boolean variables (those that can be set to on or off) are set to
+ on if the value is null or empty, ON (case-insensitive), or 1.
+ Any other value results in the variable being set to off.
- * Specifying command names containing slashes.
+ The `bind -V' command lists the current Readline variable names
+ and values. *Note Bash Builtins::.
- * Specifying a filename containing a slash as an argument to the `.'
- builtin command.
+ A great deal of run-time behavior is changeable with the following
+ variables.
- * Importing function definitions from the shell environment at
- startup.
+ `bell-style'
+ Controls what happens when Readline wants to ring the
+ terminal bell. If set to `none', Readline never rings the
+ bell. If set to `visible', Readline uses a visible bell if
+ one is available. If set to `audible' (the default),
+ Readline attempts to ring the terminal's bell.
- * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
- redirection operators.
+ `bind-tty-special-chars'
+ If set to `on', Readline attempts to bind the control
+ characters treated specially by the kernel's terminal driver
+ to their Readline equivalents.
- * Using the `exec' builtin to replace the shell with another command.
+ `comment-begin'
+ The string to insert at the beginning of the line when the
+ `insert-comment' command is executed. The default value is
+ `"#"'.
- * Adding or deleting builtin commands with the `-f' and `-d' options
- to the `enable' builtin.
+ `completion-ignore-case'
+ If set to `on', Readline performs filename matching and
+ completion in a case-insensitive fashion. The default value
+ is `off'.
- * Specifying the `-p' option to the `command' builtin.
+ `completion-prefix-display-length'
+ The length in characters of the common prefix of a list of
+ possible completions that is displayed without modification.
+ When set to a value greater than zero, common prefixes longer
+ than this value are replaced with an ellipsis when displaying
+ possible completions.
- * Turning off restricted mode with `set +r'.
+ `completion-query-items'
+ The number of possible completions that determines when the
+ user is asked whether the list of possibilities should be
+ displayed. If the number of possible completions is greater
+ than this value, Readline will ask the user whether or not he
+ wishes to view them; otherwise, they are simply listed. This
+ variable must be set to an integer value greater than or
+ equal to 0. A negative value means Readline should never ask.
+ The default limit is `100'.
-\1f
-File: bashref.info, Node: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
+ `convert-meta'
+ If set to `on', Readline will convert characters with the
+ eighth bit set to an ASCII key sequence by stripping the
+ eighth bit and prefixing an <ESC> character, converting them
+ to a meta-prefixed key sequence. The default value is `on'.
-Bash POSIX Mode
-===============
+ `disable-completion'
+ If set to `On', Readline will inhibit word completion.
+ Completion characters will be inserted into the line as if
+ they had been mapped to `self-insert'. The default is `off'.
- Starting Bash with the `--posix' command-line option or executing
-`set -o posix' while Bash is running will cause Bash to conform more
-closely to the POSIX.2 standard by changing the behavior to match that
-specified by POSIX.2 in areas where the Bash default differs.
+ `editing-mode'
+ The `editing-mode' variable controls which default set of key
+ bindings is used. By default, Readline starts up in Emacs
+ editing mode, where the keystrokes are most similar to Emacs.
+ This variable can be set to either `emacs' or `vi'.
- The following list is what's changed when `POSIX mode' is in effect:
+ `enable-keypad'
+ When set to `on', Readline will try to enable the application
+ keypad when it is called. Some systems need this to enable
+ the arrow keys. The default is `off'.
- 1. When a command in the hash table no longer exists, Bash will
- re-search `$PATH' to find the new location. This is also
- available with `shopt -s checkhash'.
+ `expand-tilde'
+ If set to `on', tilde expansion is performed when Readline
+ attempts word completion. The default is `off'.
- 2. The `>&' redirection does not redirect stdout and stderr.
+ `history-preserve-point'
+ If set to `on', the history code attempts to place the point
+ (the current cursor position) at the same location on each
+ history line retrieved with `previous-history' or
+ `next-history'. The default is `off'.
- 3. The message printed by the job control code and builtins when a job
- exits with a non-zero status is `Done(status)'.
+ `history-size'
+ Set the maximum number of history entries saved in the
+ history list. If set to zero, the number of entries in the
+ history list is not limited.
- 4. Reserved words may not be aliased.
+ `horizontal-scroll-mode'
+ This variable can be set to either `on' or `off'. Setting it
+ to `on' means that the text of the lines being edited will
+ scroll horizontally on a single screen line when they are
+ longer than the width of the screen, instead of wrapping onto
+ a new screen line. By default, this variable is set to `off'.
- 5. The POSIX.2 `PS1' and `PS2' expansions of `!' to the history
- number and `!!' to `!' are enabled, and parameter expansion is
- performed on the value regardless of the setting of the
- `promptvars' option.
+ `input-meta'
+ If set to `on', Readline will enable eight-bit input (it will
+ not clear the eighth bit in the characters it reads),
+ regardless of what the terminal claims it can support. The
+ default value is `off'. The name `meta-flag' is a synonym
+ for this variable.
- 6. Interactive comments are enabled by default. (Note that Bash has
- them on by default anyway.)
+ `isearch-terminators'
+ The string of characters that should terminate an incremental
+ search without subsequently executing the character as a
+ command (*note Searching::). If this variable has not been
+ given a value, the characters <ESC> and `C-J' will terminate
+ an incremental search.
- 7. The POSIX.2 startup files are executed (`$ENV') rather than the
- normal Bash files.
+ `keymap'
+ Sets Readline's idea of the current keymap for key binding
+ commands. Acceptable `keymap' names are `emacs',
+ `emacs-standard', `emacs-meta', `emacs-ctlx', `vi', `vi-move',
+ `vi-command', and `vi-insert'. `vi' is equivalent to
+ `vi-command'; `emacs' is equivalent to `emacs-standard'. The
+ default value is `emacs'. The value of the `editing-mode'
+ variable also affects the default keymap.
- 8. Tilde expansion is only performed on assignments preceding a
- command name, rather than on all assignment statements on the line.
+ `mark-directories'
+ If set to `on', completed directory names have a slash
+ appended. The default is `on'.
- 9. The default history file is `~/.sh_history' (this is the default
- value of `$HISTFILE').
+ `mark-modified-lines'
+ This variable, when set to `on', causes Readline to display an
+ asterisk (`*') at the start of history lines which have been
+ modified. This variable is `off' by default.
+
+ `mark-symlinked-directories'
+ If set to `on', completed names which are symbolic links to
+ directories have a slash appended (subject to the value of
+ `mark-directories'). The default is `off'.
+
+ `match-hidden-files'
+ This variable, when set to `on', causes Readline to match
+ files whose names begin with a `.' (hidden files) when
+ performing filename completion, unless the leading `.' is
+ supplied by the user in the filename to be completed. This
+ variable is `on' by default.
- 10. The output of `kill -l' prints all the signal names on a single
- line, separated by spaces.
+ `output-meta'
+ If set to `on', Readline will display characters with the
+ eighth bit set directly rather than as a meta-prefixed escape
+ sequence. The default is `off'.
- 11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
- found.
+ `page-completions'
+ If set to `on', Readline uses an internal `more'-like pager
+ to display a screenful of possible completions at a time.
+ This variable is `on' by default.
- 12. Redirection operators do not perform filename expansion on the word
- in the redirection unless the shell is interactive.
+ `print-completions-horizontally'
+ If set to `on', Readline will display completions with matches
+ sorted horizontally in alphabetical order, rather than down
+ the screen. The default is `off'.
- 13. Function names must be valid shell `name's. That is, they may not
- contain characters other than letters, digits, and underscores, and
- may not start with a digit. Declaring a function with an illegal
- name causes a fatal syntax error in non-interactive shells.
+ `revert-all-at-newline'
+ If set to `on', Readline will undo all changes to history
+ lines before returning when `accept-line' is executed. By
+ default, history lines may be modified and retain individual
+ undo lists across calls to `readline'. The default is `off'.
- 14. POSIX.2 `special' builtins are found before shell functions during
- command lookup.
+ `show-all-if-ambiguous'
+ This alters the default behavior of the completion functions.
+ If set to `on', words which have more than one possible
+ completion cause the matches to be listed immediately instead
+ of ringing the bell. The default value is `off'.
- 15. If a POSIX.2 special builtin returns an error status, a
- non-interactive shell exits. The fatal errors are those listed in
- the POSIX.2 standard, and include things like passing incorrect
- options, redirection errors, variable assignment errors for
- assignments preceding the command name, and so on.
+ `show-all-if-unmodified'
+ This alters the default behavior of the completion functions
+ in a fashion similar to SHOW-ALL-IF-AMBIGUOUS. If set to
+ `on', words which have more than one possible completion
+ without any possible partial completion (the possible
+ completions don't share a common prefix) cause the matches to
+ be listed immediately instead of ringing the bell. The
+ default value is `off'.
- 16. If the `cd' builtin finds a directory to change to using
- `$CDPATH', the value it assigns to the `PWD' variable does not
- contain any symbolic links, as if `cd -P' had been executed.
+ `visible-stats'
+ If set to `on', a character denoting a file's type is
+ appended to the filename when listing possible completions.
+ The default is `off'.
- 17. A non-interactive shell exits with an error status if a variable
- assignment error occurs when no command name follows the assignment
- statements. A variable assignment error occurs, for example, when
- trying to assign a value to a read-only variable.
- 18. A non-interactive shell exits with an error status if the iteration
- variable in a `for' statement or the selection variable in a
- `select' statement is a read-only variable.
+Key Bindings
+ The syntax for controlling key bindings in the init file is
+ simple. First you need to find the name of the command that you
+ want to change. The following sections contain tables of the
+ command name, the default keybinding, if any, and a short
+ description of what the command does.
- 19. Process substitution is not available.
+ Once you know the name of the command, simply place on a line in
+ the init file the name of the key you wish to bind the command to,
+ a colon, and then the name of the command. There can be no space
+ between the key name and the colon - that will be interpreted as
+ part of the key name. The name of the key can be expressed in
+ different ways, depending on what you find most comfortable.
- 20. Assignment statements preceding POSIX.2 `special' builtins persist
- in the shell environment after the builtin completes.
+ In addition to command names, readline allows keys to be bound to
+ a string that is inserted when the key is pressed (a MACRO).
- 21. The `export' and `readonly' builtin commands display their output
- in the format required by POSIX.2.
+ The `bind -p' command displays Readline function names and
+ bindings in a format that can put directly into an initialization
+ file. *Note Bash Builtins::.
+ KEYNAME: FUNCTION-NAME or MACRO
+ KEYNAME is the name of a key spelled out in English. For
+ example:
+ Control-u: universal-argument
+ Meta-Rubout: backward-kill-word
+ Control-o: "> output"
- There is other POSIX.2 behavior that Bash does not implement.
-Specifically:
+ In the above example, `C-u' is bound to the function
+ `universal-argument', `M-DEL' is bound to the function
+ `backward-kill-word', and `C-o' is bound to run the macro
+ expressed on the right hand side (that is, to insert the text
+ `> output' into the line).
- 1. Assignment statements affect the execution environment of all
- builtins, not just special ones.
+ A number of symbolic character names are recognized while
+ processing this key binding syntax: DEL, ESC, ESCAPE, LFD,
+ NEWLINE, RET, RETURN, RUBOUT, SPACE, SPC, and TAB.
-\1f
-File: bashref.info, Node: Job Control, Next: Using History Interactively, Prev: Bash Features, Up: Top
+ "KEYSEQ": FUNCTION-NAME or MACRO
+ KEYSEQ differs from KEYNAME above in that strings denoting an
+ entire key sequence can be specified, by placing the key
+ sequence in double quotes. Some GNU Emacs style key escapes
+ can be used, as in the following example, but the special
+ character names are not recognized.
-Job Control
-***********
+ "\C-u": universal-argument
+ "\C-x\C-r": re-read-init-file
+ "\e[11~": "Function Key 1"
- This chapter disusses what job control is, how it works, and how
-Bash allows you to access its facilities.
+ In the above example, `C-u' is again bound to the function
+ `universal-argument' (just as it was in the first example),
+ `C-x C-r' is bound to the function `re-read-init-file', and
+ `<ESC> <[> <1> <1> <~>' is bound to insert the text `Function
+ Key 1'.
-* Menu:
-* Job Control Basics:: How job control works.
-* Job Control Builtins:: Bash builtin commands used to interact
- with job control.
-* Job Control Variables:: Variables Bash uses to customize job
- control.
+ The following GNU Emacs style escape sequences are available when
+ specifying key sequences:
-\1f
-File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
+ `\C-'
+ control prefix
-Job Control Basics
-==================
+ `\M-'
+ meta prefix
- Job control refers to the ability to selectively stop (suspend) the
-execution of processes and continue (resume) their execution at a later
-point. A user typically employs this facility via an interactive
-interface supplied jointly by the system's terminal driver and Bash.
+ `\e'
+ an escape character
- The shell associates a JOB with each pipeline. It keeps a table of
-currently executing jobs, which may be listed with the `jobs' command.
-When Bash starts a job asynchronously (in the background), it prints a
-line that looks like:
- [1] 25647
+ `\\'
+ backslash
-indicating that this job is job number 1 and that the process ID of the
-last process in the pipeline associated with this job is 25647. All of
-the processes in a single pipeline are members of the same job. Bash
-uses the JOB abstraction as the basis for job control.
+ `\"'
+ <">, a double quotation mark
- To facilitate the implementation of the user interface to job
-control, the system maintains the notion of a current terminal process
-group ID. Members of this process group (processes whose process group
-ID is equal to the current terminal process group ID) receive
-keyboard-generated signals such as `SIGINT'. These processes are said
-to be in the foreground. Background processes are those whose process
-group ID differs from the terminal's; such processes are immune to
-keyboard-generated signals. Only foreground processes are allowed to
-read from or write to the terminal. Background processes which attempt
-to read from (write to) the terminal are sent a `SIGTTIN' (`SIGTTOU')
-signal by the terminal driver, which, unless caught, suspends the
-process.
+ `\''
+ <'>, a single quote or apostrophe
- If the operating system on which Bash is running supports job
-control, Bash allows you to use it. Typing the SUSPEND character
-(typically `^Z', Control-Z) while a process is running causes that
-process to be stopped and returns you to Bash. Typing the DELAYED
-SUSPEND character (typically `^Y', Control-Y) causes the process to be
-stopped when it attempts to read input from the terminal, and control to
-be returned to Bash. You may then manipulate the state of this job,
-using the `bg' command to continue it in the background, the `fg'
-command to continue it in the foreground, or the `kill' command to kill
-it. A `^Z' takes effect immediately, and has the additional side
-effect of causing pending output and typeahead to be discarded.
+ In addition to the GNU Emacs style escape sequences, a second set
+ of backslash escapes is available:
- There are a number of ways to refer to a job in the shell. The
-character `%' introduces a job name. Job number `n' may be referred to
-as `%n'. A job may also be referred to using a prefix of the name used
-to start it, or using a substring that appears in its command line.
-For example, `%ce' refers to a stopped `ce' job. Using `%?ce', on the
-other hand, refers to any job containing the string `ce' in its command
-line. If the prefix or substring matches more than one job, Bash
-reports an error. The symbols `%%' and `%+' refer to the shell's
-notion of the current job, which is the last job stopped while it was
-in the foreground. The previous job may be referenced using `%-'. In
-output pertaining to jobs (e.g., the output of the `jobs' command), the
-current job is always flagged with a `+', and the previous job with a
-`-'.
+ `\a'
+ alert (bell)
- Simply naming a job can be used to bring it into the foreground:
-`%1' is a synonym for `fg %1', bringing job 1 from the background into
-the foreground. Similarly, `%1 &' resumes job 1 in the background,
-equivalent to `bg %1'
+ `\b'
+ backspace
- The shell learns immediately whenever a job changes state.
-Normally, Bash waits until it is about to print a prompt before
-reporting changes in a job's status so as to not interrupt any other
-output. If the the `-b' option to the `set' builtin is set, Bash
-reports such changes immediately (*note The Set Builtin::.).
+ `\d'
+ delete
- If you attempt to exit Bash while jobs are stopped, the shell prints
-a message warning you that you have stopped jobs. You may then use the
-`jobs' command to inspect their status. If you do this, or try to exit
-again immediately, you are not warned again, and the stopped jobs are
-terminated.
+ `\f'
+ form feed
-\1f
-File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
+ `\n'
+ newline
-Job Control Builtins
-====================
+ `\r'
+ carriage return
-`bg'
- bg [JOBSPEC]
- Place JOBSPEC into the background, as if it had been started with
- `&'. If JOBSPEC is not supplied, the current job is used.
+ `\t'
+ horizontal tab
-`fg'
- fg [JOBSPEC]
- Bring JOBSPEC into the foreground and make it the current job. If
- JOBSPEC is not supplied, the current job is used.
+ `\v'
+ vertical tab
-`jobs'
- jobs [-lpnrs] [JOBSPEC]
- jobs -x COMMAND [JOBSPEC]
+ `\NNN'
+ the eight-bit character whose value is the octal value NNN
+ (one to three digits)
- The first form lists the active jobs. The options have the
- following meanings:
+ `\xHH'
+ the eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits)
- `-l'
- List process IDs in addition to the normal information
+ When entering the text of a macro, single or double quotes must be
+ used to indicate a macro definition. Unquoted text is assumed to
+ be a function name. In the macro body, the backslash escapes
+ described above are expanded. Backslash will quote any other
+ character in the macro text, including `"' and `''. For example,
+ the following binding will make `C-x \' insert a single `\' into
+ the line:
+ "\C-x\\": "\\"
- `-n'
- Display information only about jobs that have changed status
- since you were last notified of their status.
- `-p'
- List only the process ID of the job's process group leader.
+\1f
+File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
- `-r'
- Restrict output to running jobs.
+8.3.2 Conditional Init Constructs
+---------------------------------
- `-s'
- Restrict output to stopped jobs.
+Readline implements a facility similar in spirit to the conditional
+compilation features of the C preprocessor which allows key bindings
+and variable settings to be performed as the result of tests. There
+are four parser directives used.
- If JOBSPEC is given, output is restricted to information about
- that job. If JOBSPEC is not supplied, the status of all jobs is
- listed.
+`$if'
+ The `$if' construct allows bindings to be made based on the
+ editing mode, the terminal being used, or the application using
+ Readline. The text of the test extends to the end of the line; no
+ characters are required to isolate it.
- If the `-x' option is supplied, `jobs' replaces any JOBSPEC found
- in COMMAND or ARGUMENTS with the corresponding process group ID,
- and executes COMMAND, passing it ARGUMENTs, returning its exit
- status.
+ `mode'
+ The `mode=' form of the `$if' directive is used to test
+ whether Readline is in `emacs' or `vi' mode. This may be
+ used in conjunction with the `set keymap' command, for
+ instance, to set bindings in the `emacs-standard' and
+ `emacs-ctlx' keymaps only if Readline is starting out in
+ `emacs' mode.
-`kill'
- kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] JOBSPEC
- kill -l [SIGSPEC]
- Send a signal specified by SIGSPEC or SIGNUM to the process named
- by JOBSPEC. SIGSPEC is either a signal name such as `SIGINT'
- (with or without the `SIG' prefix) or a signal number; SIGNUM is a
- signal number. If SIGSPEC and SIGNUM are not present, `SIGTERM'
- is used. The `-l' option lists the signal names, or the signal
- name corresponding to SIGSPEC.
+ `term'
+ The `term=' form may be used to include terminal-specific key
+ bindings, perhaps to bind the key sequences output by the
+ terminal's function keys. The word on the right side of the
+ `=' is tested against both the full name of the terminal and
+ the portion of the terminal name before the first `-'. This
+ allows `sun' to match both `sun' and `sun-cmd', for instance.
-`wait'
- wait [JOBSPEC|PID]
- Wait until the child process specified by process ID PID or job
- specification JOBSPEC exits and report its exit status. If a job
- spec is given, all processes in the job are waited for. If no
- arguments are given, all currently active child processes are
- waited for.
+ `application'
+ The APPLICATION construct is used to include
+ application-specific settings. Each program using the
+ Readline library sets the APPLICATION NAME, and you can test
+ for a particular value. This could be used to bind key
+ sequences to functions useful for a specific program. For
+ instance, the following command adds a key sequence that
+ quotes the current or previous word in Bash:
+ $if Bash
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ $endif
-`disown'
- disown [-h] [JOBSPEC ...]
- Without options, each JOBSPEC is removed from the table of active
- jobs. If the `-h' option is given, the job is not removed from
- the table, but is marked so that `SIGHUP' is not sent to the job
- if the shell receives a `SIGHUP'. If JOBSPEC is not present, the
- current job is used.
+`$endif'
+ This command, as seen in the previous example, terminates an `$if'
+ command.
-`suspend'
- suspend [-f]
- Suspend the execution of this shell until it receives a `SIGCONT'
- signal. The `-f' option means to suspend even if the shell is a
- login shell.
+`$else'
+ Commands in this branch of the `$if' directive are executed if the
+ test fails.
- When job control is not active, the `kill' and `wait' builtins do
-not accept JOBSPEC arguments. They must be supplied process IDs.
+`$include'
+ This directive takes a single filename as an argument and reads
+ commands and bindings from that file. For example, the following
+ directive reads from `/etc/inputrc':
+ $include /etc/inputrc
\1f
-File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
-
-Job Control Variables
-=====================
+File: bashref.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
-`auto_resume'
- This variable controls how the shell interacts with the user and
- job control. If this variable exists then single word simple
- commands without redirects are treated as candidates for resumption
- of an existing job. There is no ambiguity allowed; if there is
- more than one job beginning with the string typed, then the most
- recently accessed job will be selected. The name of a stopped
- job, in this context, is the command line used to start it. If
- this variable is set to the value `exact', the string supplied
- must match the name of a stopped job exactly; if set to
- `substring', the string supplied needs to match a substring of the
- name of a stopped job. The `substring' value provides
- functionality analogous to the `%?' job ID (*note Job Control
- Basics::.). If set to any other value, the supplied string must
- be a prefix of a stopped job's name; this provides functionality
- analogous to the `%' job ID.
+8.3.3 Sample Init File
+----------------------
-\1f
-File: bashref.info, Node: Using History Interactively, Next: Command Line Editing, Prev: Job Control, Up: Top
+Here is an example of an INPUTRC file. This illustrates key binding,
+variable assignment, and conditional syntax.
-Using History Interactively
-***************************
- This chapter describes how to use the GNU History Library
-interactively, from a user's standpoint. It should be considered a
-user's guide. For information on using the GNU History Library in your
-own programs, see the GNU Readline Library Manual.
+ # This file controls the behaviour of line input editing for
+ # programs that use the GNU Readline library. Existing
+ # programs include FTP, Bash, and GDB.
+ #
+ # You can re-read the inputrc file with C-x C-r.
+ # Lines beginning with '#' are comments.
+ #
+ # First, include any systemwide bindings and variable
+ # assignments from /etc/Inputrc
+ $include /etc/Inputrc
-* Menu:
+ #
+ # Set various bindings for emacs mode.
-* Bash History Facilities:: How Bash lets you manipulate your command
- history.
-* History Interaction:: What it feels like using History as a user.
+ set editing-mode emacs
-\1f
-File: bashref.info, Node: Bash History Facilities, Next: History Interaction, Up: Using History Interactively
+ $if mode=emacs
-Bash History Facilities
-=======================
+ Meta-Control-h: backward-kill-word Text after the function name is ignored
- When the `-o history' option to the `set' builtin is enabled (*note
-The Set Builtin::.), the shell provides access to the COMMAND HISTORY,
-the list of commands previously typed. The text of the last `HISTSIZE'
-commands (default 500) is saved in a history list. The shell stores
-each command in the history list prior to parameter and variable
-expansion but after history expansion is performed, subject to the
-values of the shell variables `HISTIGNORE' and `HISTCONTROL'. When the
-shell starts up, the history is initialized from the file named by the
-`HISTFILE' variable (default `~/.bash_history'). `HISTFILE' is
-truncated, if necessary, to contain no more than the number of lines
-specified by the value of the `HISTFILESIZE' variable. When an
-interactive shell exits, the last `HISTSIZE' lines are copied from the
-history list to `HISTFILE'. If the `histappend' shell option is set
-(*note Bash Builtins::.), the lines are appended to the history file,
-otherwise the history file is overwritten. If `HISTFILE' is unset, or
-if the history file is unwritable, the history is not saved. After
-saving the history, the history file is truncated to contain no more
-than `$HISTFILESIZE' lines. If `HISTFILESIZE' is not set, no
-truncation is performed.
-
- The builtin command `fc' (*note Korn Shell Builtins::.) may be used
-to list or edit and re-execute a portion of the history list. The
-`history' builtin (*note C Shell Builtins::.) can be used to display or
-modify the history list and manipulate the history file. When using
-the command-line editing, search commands are available in each editing
-mode that provide access to the history list.
+ #
+ # Arrow keys in keypad mode
+ #
+ #"\M-OD": backward-char
+ #"\M-OC": forward-char
+ #"\M-OA": previous-history
+ #"\M-OB": next-history
+ #
+ # Arrow keys in ANSI mode
+ #
+ "\M-[D": backward-char
+ "\M-[C": forward-char
+ "\M-[A": previous-history
+ "\M-[B": next-history
+ #
+ # Arrow keys in 8 bit keypad mode
+ #
+ #"\M-\C-OD": backward-char
+ #"\M-\C-OC": forward-char
+ #"\M-\C-OA": previous-history
+ #"\M-\C-OB": next-history
+ #
+ # Arrow keys in 8 bit ANSI mode
+ #
+ #"\M-\C-[D": backward-char
+ #"\M-\C-[C": forward-char
+ #"\M-\C-[A": previous-history
+ #"\M-\C-[B": next-history
- The shell allows control over which commands are saved on the history
-list. The `HISTCONTROL' and `HISTIGNORE' variables may be set to cause
-the shell to save only a subset of the commands entered. The `cmdhist'
-shell option, if enabled, causes the shell to attempt to save each line
-of a multi-line command in the same history entry, adding semicolons
-where necessary to preserve syntactic correctness. The `lithist' shell
-option causes the shell to save the command with embedded newlines
-instead of semicolons. *Note Bash Builtins:: for a description of
-`shopt'.
+ C-q: quoted-insert
-\1f
-File: bashref.info, Node: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
+ $endif
-Interactive History Expansion
-=============================
+ # An old-style binding. This happens to be the default.
+ TAB: complete
- The History library provides a history expansion feature that is
-similar to the history expansion provided by `csh'. This section
-describes the syntax used to manipulate the history information.
+ # Macros that are convenient for shell interaction
+ $if Bash
+ # edit the path
+ "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
+ # prepare to type a quoted word --
+ # insert open and close double quotes
+ # and move to just after the open quote
+ "\C-x\"": "\"\"\C-b"
+ # insert a backslash (testing backslash escapes
+ # in sequences and macros)
+ "\C-x\\": "\\"
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ # Add a binding to refresh the line, which is unbound
+ "\C-xr": redraw-current-line
+ # Edit variable on current line.
+ "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
+ $endif
- History expansions introduce words from the history list into the
-input stream, making it easy to repeat commands, insert the arguments
-to a previous command into the current input line, or fix errors in
-previous commands quickly.
+ # use a visible bell if one is available
+ set bell-style visible
- History expansion takes place in two parts. The first is to
-determine which line from the previous history should be used during
-substitution. The second is to select portions of that line for
-inclusion into the current one. The line selected from the previous
-history is called the "event", and the portions of that line that are
-acted upon are called "words". Various "modifiers" are available to
-manipulate the selected words. The line is broken into words in the
-same fashion that Bash does, so that several English (or Unix) words
-surrounded by quotes are considered as one word. History expansions
-are introduced by the appearance of the history expansion character,
-which is `!' by default. Only `\' and `'' may be used to escape the
-history expansion character.
+ # don't strip characters to 7 bits when reading
+ set input-meta on
- Several shell options settable with the `shopt' builtin (*note Bash
-Builtins::.) may be used to tailor the behavior of history expansion.
-If the `histverify' shell option is enabled, and Readline is being
-used, history substitutions are not immediately passed to the shell
-parser. Instead, the expanded line is reloaded into the Readline
-editing buffer for further modification. If Readline is being used,
-and the `histreedit' shell option is enabled, a failed history
-expansion will be reloaded into the Readline editing buffer for
-correction. The `-p' option to the `history' builtin command may be
-used to see what a history expansion will do before using it. The `-s'
-option to the `history' builtin may be used to add commands to the end
-of the history list without actually executing them, so that they are
-available for subsequent recall.
+ # allow iso-latin1 characters to be inserted rather
+ # than converted to prefix-meta sequences
+ set convert-meta off
- The shell allows control of the various characters used by the
-history expansion mechanism with the `histchars' variable.
+ # display characters with the eighth bit set directly
+ # rather than as meta-prefixed characters
+ set output-meta on
-* Menu:
+ # if there are more than 150 possible completions for
+ # a word, ask the user if he wants to see all of them
+ set completion-query-items 150
-* Event Designators:: How to specify which history line to use.
-* Word Designators:: Specifying which words are of interest.
-* Modifiers:: Modifying the results of substitution.
+ # For FTP
+ $if Ftp
+ "\C-xg": "get \M-?"
+ "\C-xt": "put \M-?"
+ "\M-.": yank-last-arg
+ $endif
\1f
-File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
-
-Event Designators
------------------
+File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
- An event designator is a reference to a command line entry in the
-history list.
+8.4 Bindable Readline Commands
+==============================
-`!'
- Start a history substitution, except when followed by a space, tab,
- the end of the line, = or (.
+* Menu:
-`!N'
- Refer to command line N.
+* Commands For Moving:: Moving about the line.
+* Commands For History:: Getting at previous lines.
+* Commands For Text:: Commands for changing text.
+* Commands For Killing:: Commands for killing and yanking.
+* Numeric Arguments:: Specifying numeric arguments, repeat counts.
+* Commands For Completion:: Getting Readline to do the typing for you.
+* Keyboard Macros:: Saving and re-executing typed characters
+* Miscellaneous Commands:: Other miscellaneous commands.
-`!-N'
- Refer to the command N lines back.
+ This section describes Readline commands that may be bound to key
+sequences. You can list your key bindings by executing `bind -P' or,
+for a more terse format, suitable for an INPUTRC file, `bind -p'.
+(*Note Bash Builtins::.) Command names without an accompanying key
+sequence are unbound by default.
-`!!'
- Refer to the previous command. This is a synonym for `!-1'.
+ In the following descriptions, "point" refers to the current cursor
+position, and "mark" refers to a cursor position saved by the
+`set-mark' command. The text between the point and mark is referred to
+as the "region".
-`!STRING'
- Refer to the most recent command starting with STRING.
+\1f
+File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
-`!?STRING[?]'
- Refer to the most recent command containing STRING. The trailing
- `?' may be omitted if the STRING is followed immediately by a
- newline.
+8.4.1 Commands For Moving
+-------------------------
-`^STRING1^STRING2^'
- Quick Substitution. Repeat the last command, replacing STRING1
- with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
+`beginning-of-line (C-a)'
+ Move to the start of the current line.
-`!#'
- The entire command line typed so far.
+`end-of-line (C-e)'
+ Move to the end of the line.
-\1f
-File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
+`forward-char (C-f)'
+ Move forward a character.
-Word Designators
-----------------
+`backward-char (C-b)'
+ Move back a character.
- Word designators are used to select desired words from the event. A
-`:' separates the event specification from the word designator. It can
-be omitted if the word designator begins with a `^', `$', `*', `-', or
-`%'. Words are numbered from the beginning of the line, with the first
-word being denoted by 0 (zero). Words are inserted into the current
-line separated by single spaces.
+`forward-word (M-f)'
+ Move forward to the end of the next word. Words are composed of
+ letters and digits.
-`0 (zero)'
- The `0'th word. For many applications, this is the command word.
+`backward-word (M-b)'
+ Move back to the start of the current or previous word. Words are
+ composed of letters and digits.
-`N'
- The Nth word.
+`shell-forward-word ()'
+ Move forward to the end of the next word. Words are delimited by
+ non-quoted shell metacharacters.
-`^'
- The first argument; that is, word 1.
+`shell-backward-word ()'
+ Move back to the start of the current or previous word. Words are
+ delimited by non-quoted shell metacharacters.
-`$'
- The last argument.
+`clear-screen (C-l)'
+ Clear the screen and redraw the current line, leaving the current
+ line at the top of the screen.
-`%'
- The word matched by the most recent `?STRING?' search.
+`redraw-current-line ()'
+ Refresh the current line. By default, this is unbound.
-`X-Y'
- A range of words; `-Y' abbreviates `0-Y'.
-`*'
- All of the words, except the `0'th. This is a synonym for `1-$'.
- It is not an error to use `*' if there is just one word in the
- event; the empty string is returned in that case.
+\1f
+File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
-`X*'
- Abbreviates `X-$'
+8.4.2 Commands For Manipulating The History
+-------------------------------------------
-`X-'
- Abbreviates `X-$' like `X*', but omits the last word.
+`accept-line (Newline or Return)'
+ Accept the line regardless of where the cursor is. If this line is
+ non-empty, add it to the history list according to the setting of
+ the `HISTCONTROL' and `HISTIGNORE' variables. If this line is a
+ modified history line, then restore the history line to its
+ original state.
- If a word designator is supplied without an event specification, the
-previous command is used as the event.
+`previous-history (C-p)'
+ Move `back' through the history list, fetching the previous
+ command.
-\1f
-File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
+`next-history (C-n)'
+ Move `forward' through the history list, fetching the next command.
-Modifiers
----------
+`beginning-of-history (M-<)'
+ Move to the first line in the history.
- After the optional word designator, you can add a sequence of one or
-more of the following modifiers, each preceded by a `:'.
+`end-of-history (M->)'
+ Move to the end of the input history, i.e., the line currently
+ being entered.
-`h'
- Remove a trailing pathname component, leaving only the head.
+`reverse-search-history (C-r)'
+ Search backward starting at the current line and moving `up'
+ through the history as necessary. This is an incremental search.
-`t'
- Remove all leading pathname components, leaving the tail.
+`forward-search-history (C-s)'
+ Search forward starting at the current line and moving `down'
+ through the the history as necessary. This is an incremental
+ search.
-`r'
- Remove a trailing suffix of the form `.SUFFIX', leaving the
- basename.
+`non-incremental-reverse-search-history (M-p)'
+ Search backward starting at the current line and moving `up'
+ through the history as necessary using a non-incremental search
+ for a string supplied by the user.
-`e'
- Remove all but the trailing suffix.
+`non-incremental-forward-search-history (M-n)'
+ Search forward starting at the current line and moving `down'
+ through the the history as necessary using a non-incremental search
+ for a string supplied by the user.
-`p'
- Print the new command but do not execute it.
+`history-search-forward ()'
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. This is a
+ non-incremental search. By default, this command is unbound.
-`q'
- Quote the substituted words, escaping further substitutions.
+`history-search-backward ()'
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. This is a
+ non-incremental search. By default, this command is unbound.
-`x'
- Quote the substituted words as with `q', but break into words at
- spaces, tabs, and newlines.
+`yank-nth-arg (M-C-y)'
+ Insert the first argument to the previous command (usually the
+ second word on the previous line) at point. With an argument N,
+ insert the Nth word from the previous command (the words in the
+ previous command begin with word 0). A negative argument inserts
+ the Nth word from the end of the previous command. Once the
+ argument N is computed, the argument is extracted as if the `!N'
+ history expansion had been specified.
+
+`yank-last-arg (M-. or M-_)'
+ Insert last argument to the previous command (the last word of the
+ previous history entry). With an argument, behave exactly like
+ `yank-nth-arg'. Successive calls to `yank-last-arg' move back
+ through the history list, inserting the last argument of each line
+ in turn. The history expansion facilities are used to extract the
+ last argument, as if the `!$' history expansion had been specified.
-`s/OLD/NEW/'
- Substitute NEW for the first occurrence of OLD in the event line.
- Any delimiter may be used in place of `/'. The delimiter may be
- quoted in OLD and NEW with a single backslash. If `&' appears in
- NEW, it is replaced by OLD. A single backslash will quote the
- `&'. The final delimiter is optional if it is the last character
- on the input line.
-`&'
- Repeat the previous substitution.
+\1f
+File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
-`g'
- Cause changes to be applied over the entire event line. Used in
- conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
+8.4.3 Commands For Changing Text
+--------------------------------
-\1f
-File: bashref.info, Node: Command Line Editing, Next: Installing Bash, Prev: Using History Interactively, Up: Top
+`delete-char (C-d)'
+ Delete the character at point. If point is at the beginning of
+ the line, there are no characters in the line, and the last
+ character typed was not bound to `delete-char', then return EOF.
-Command Line Editing
-********************
+`backward-delete-char (Rubout)'
+ Delete the character behind the cursor. A numeric argument means
+ to kill the characters instead of deleting them.
- This chapter describes the basic features of the GNU command line
-editing interface.
+`forward-backward-delete-char ()'
+ Delete the character under the cursor, unless the cursor is at the
+ end of the line, in which case the character behind the cursor is
+ deleted. By default, this is not bound to a key.
-* Menu:
+`quoted-insert (C-q or C-v)'
+ Add the next character typed to the line verbatim. This is how to
+ insert key sequences like `C-q', for example.
-* Introduction and Notation:: Notation used in this text.
-* Readline Interaction:: The minimum set of commands for editing a line.
-* Readline Init File:: Customizing Readline from a user's view.
-* Bindable Readline Commands:: A description of most of the Readline commands
- available for binding
-* Readline vi Mode:: A short description of how to make Readline
- behave like the vi editor.
+`self-insert (a, b, A, 1, !, ...)'
+ Insert yourself.
-\1f
-File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
+`transpose-chars (C-t)'
+ Drag the character before the cursor forward over the character at
+ the cursor, moving the cursor forward as well. If the insertion
+ point is at the end of the line, then this transposes the last two
+ characters of the line. Negative arguments have no effect.
-Introduction to Line Editing
-============================
+`transpose-words (M-t)'
+ Drag the word before point past the word after point, moving point
+ past that word as well. If the insertion point is at the end of
+ the line, this transposes the last two words on the line.
- The following paragraphs describe the notation used to represent
-keystrokes.
+`upcase-word (M-u)'
+ Uppercase the current (or following) word. With a negative
+ argument, uppercase the previous word, but do not move the cursor.
- The text C-k is read as `Control-K' and describes the character
-produced when the k key is pressed while the Control key is depressed.
+`downcase-word (M-l)'
+ Lowercase the current (or following) word. With a negative
+ argument, lowercase the previous word, but do not move the cursor.
- The text M-k is read as `Meta-K' and describes the character
-produced when the meta key (if you have one) is depressed, and the k
-key is pressed. If you do not have a meta key, the identical keystroke
-can be generated by typing ESC first, and then typing k. Either
-process is known as "metafying" the k key.
+`capitalize-word (M-c)'
+ Capitalize the current (or following) word. With a negative
+ argument, capitalize the previous word, but do not move the cursor.
- The text M-C-k is read as `Meta-Control-k' and describes the
-character produced by "metafying" C-k.
+`overwrite-mode ()'
+ Toggle overwrite mode. With an explicit positive numeric argument,
+ switches to overwrite mode. With an explicit non-positive numeric
+ argument, switches to insert mode. This command affects only
+ `emacs' mode; `vi' mode does overwrite differently. Each call to
+ `readline()' starts in insert mode.
- In addition, several keys have their own names. Specifically, DEL,
-ESC, LFD, SPC, RET, and TAB all stand for themselves when seen in this
-text, or in an init file (*note Readline Init File::.).
+ In overwrite mode, characters bound to `self-insert' replace the
+ text at point rather than pushing the text to the right.
+ Characters bound to `backward-delete-char' replace the character
+ before point with a space.
-\1f
-File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
+ By default, this command is unbound.
-Readline Interaction
-====================
- Often during an interactive session you type in a long line of text,
-only to notice that the first word on the line is misspelled. The
-Readline library gives you a set of commands for manipulating the text
-as you type it in, allowing you to just fix your typo, and not forcing
-you to retype the majority of the line. Using these editing commands,
-you move the cursor to the place that needs correction, and delete or
-insert the text of the corrections. Then, when you are satisfied with
-the line, you simply press RETURN. You do not have to be at the end of
-the line to press RETURN; the entire line is accepted regardless of the
-location of the cursor within the line.
+\1f
+File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
-* Menu:
+8.4.4 Killing And Yanking
+-------------------------
-* Readline Bare Essentials:: The least you need to know about Readline.
-* Readline Movement Commands:: Moving about the input line.
-* Readline Killing Commands:: How to delete text, and how to get it back!
-* Readline Arguments:: Giving numeric arguments to commands.
-* Searching:: Searching through previous lines.
+`kill-line (C-k)'
+ Kill the text from point to the end of the line.
-\1f
-File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
+`backward-kill-line (C-x Rubout)'
+ Kill backward to the beginning of the line.
-Readline Bare Essentials
-------------------------
+`unix-line-discard (C-u)'
+ Kill backward from the cursor to the beginning of the current line.
- In order to enter characters into the line, simply type them. The
-typed character appears where the cursor was, and then the cursor moves
-one space to the right. If you mistype a character, you can use your
-erase character to back up and delete the mistyped character.
+`kill-whole-line ()'
+ Kill all characters on the current line, no matter where point is.
+ By default, this is unbound.
- Sometimes you may miss typing a character that you wanted to type,
-and not notice your error until you have typed several other
-characters. In that case, you can type C-b to move the cursor to the
-left, and then correct your mistake. Afterwards, you can move the
-cursor to the right with C-f.
+`kill-word (M-d)'
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the same
+ as `forward-word'.
- When you add text in the middle of a line, you will notice that
-characters to the right of the cursor are `pushed over' to make room
-for the text that you have inserted. Likewise, when you delete text
-behind the cursor, characters to the right of the cursor are `pulled
-back' to fill in the blank space created by the removal of the text. A
-list of the basic bare essentials for editing the text of an input line
-follows.
+`backward-kill-word (M-<DEL>)'
+ Kill the word behind point. Word boundaries are the same as
+ `backward-word'.
-C-b
- Move back one character.
+`shell-kill-word ()'
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the same
+ as `shell-forward-word'.
-C-f
- Move forward one character.
+`backward-kill-word ()'
+ Kill the word behind point. Word boundaries are the same as
+ `shell-backward-word'.
-DEL
- Delete the character to the left of the cursor.
+`unix-word-rubout (C-w)'
+ Kill the word behind point, using white space as a word boundary.
+ The killed text is saved on the kill-ring.
-C-d
- Delete the character underneath the cursor.
+`unix-filename-rubout ()'
+ Kill the word behind point, using white space and the slash
+ character as the word boundaries. The killed text is saved on the
+ kill-ring.
-Printing characters
- Insert the character into the line at the cursor.
+`delete-horizontal-space ()'
+ Delete all spaces and tabs around point. By default, this is
+ unbound.
-C-_
- Undo the last thing that you did. You can undo all the way back
- to an empty line.
+`kill-region ()'
+ Kill the text in the current region. By default, this command is
+ unbound.
-\1f
-File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
+`copy-region-as-kill ()'
+ Copy the text in the region to the kill buffer, so it can be yanked
+ right away. By default, this command is unbound.
-Readline Movement Commands
---------------------------
+`copy-backward-word ()'
+ Copy the word before point to the kill buffer. The word
+ boundaries are the same as `backward-word'. By default, this
+ command is unbound.
- The above table describes the most basic possible keystrokes that
-you need in order to do editing of the input line. For your
-convenience, many other commands have been added in addition to C-b,
-C-f, C-d, and DEL. Here are some commands for moving more rapidly
-about the line.
+`copy-forward-word ()'
+ Copy the word following point to the kill buffer. The word
+ boundaries are the same as `forward-word'. By default, this
+ command is unbound.
-C-a
- Move to the start of the line.
+`yank (C-y)'
+ Yank the top of the kill ring into the buffer at point.
-C-e
- Move to the end of the line.
+`yank-pop (M-y)'
+ Rotate the kill-ring, and yank the new top. You can only do this
+ if the prior command is `yank' or `yank-pop'.
-M-f
- Move forward a word.
+\1f
+File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
-M-b
- Move backward a word.
+8.4.5 Specifying Numeric Arguments
+----------------------------------
-C-l
- Clear the screen, reprinting the current line at the top.
+`digit-argument (M-0, M-1, ... M--)'
+ Add this digit to the argument already accumulating, or start a new
+ argument. `M--' starts a negative argument.
- Notice how C-f moves forward a character, while M-f moves forward a
-word. It is a loose convention that control keystrokes operate on
-characters while meta keystrokes operate on words.
+`universal-argument ()'
+ This is another way to specify an argument. If this command is
+ followed by one or more digits, optionally with a leading minus
+ sign, those digits define the argument. If the command is
+ followed by digits, executing `universal-argument' again ends the
+ numeric argument, but is otherwise ignored. As a special case, if
+ this command is immediately followed by a character that is
+ neither a digit or minus sign, the argument count for the next
+ command is multiplied by four. The argument count is initially
+ one, so executing this function the first time makes the argument
+ count four, a second time makes the argument count sixteen, and so
+ on. By default, this is not bound to a key.
\1f
-File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
+File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
-Readline Killing Commands
--------------------------
+8.4.6 Letting Readline Type For You
+-----------------------------------
- "Killing" text means to delete the text from the line, but to save
-it away for later use, usually by "yanking" (re-inserting) it back into
-the line. If the description for a command says that it `kills' text,
-then you can be sure that you can get the text back in a different (or
-the same) place later.
+`complete (<TAB>)'
+ Attempt to perform completion on the text before point. The
+ actual completion performed is application-specific. Bash
+ attempts completion treating the text as a variable (if the text
+ begins with `$'), username (if the text begins with `~'), hostname
+ (if the text begins with `@'), or command (including aliases and
+ functions) in turn. If none of these produces a match, filename
+ completion is attempted.
- When you use a kill command, the text is saved in a "kill-ring".
-Any number of consecutive kills save all of the killed text together, so
-that when you yank it back, you get it all. The kill ring is not line
-specific; the text that you killed on a previously typed line is
-available to be yanked back later, when you are typing another line.
+`possible-completions (M-?)'
+ List the possible completions of the text before point.
- Here is the list of commands for killing text.
+`insert-completions (M-*)'
+ Insert all completions of the text before point that would have
+ been generated by `possible-completions'.
-C-k
- Kill the text from the current cursor position to the end of the
- line.
+`menu-complete ()'
+ Similar to `complete', but replaces the word to be completed with
+ a single match from the list of possible completions. Repeated
+ execution of `menu-complete' steps through the list of possible
+ completions, inserting each match in turn. At the end of the list
+ of completions, the bell is rung (subject to the setting of
+ `bell-style') and the original text is restored. An argument of N
+ moves N positions forward in the list of matches; a negative
+ argument may be used to move backward through the list. This
+ command is intended to be bound to <TAB>, but is unbound by
+ default.
-M-d
- Kill from the cursor to the end of the current word, or if between
- words, to the end of the next word.
+`delete-char-or-list ()'
+ Deletes the character under the cursor if not at the beginning or
+ end of the line (like `delete-char'). If at the end of the line,
+ behaves identically to `possible-completions'. This command is
+ unbound by default.
-M-DEL
- Kill from the cursor the start of the previous word, or if between
- words, to the start of the previous word.
+`complete-filename (M-/)'
+ Attempt filename completion on the text before point.
-C-w
- Kill from the cursor to the previous whitespace. This is
- different than M-DEL because the word boundaries differ.
+`possible-filename-completions (C-x /)'
+ List the possible completions of the text before point, treating
+ it as a filename.
- And, here is how to "yank" the text back into the line. Yanking
-means to copy the most-recently-killed text from the kill buffer.
+`complete-username (M-~)'
+ Attempt completion on the text before point, treating it as a
+ username.
-C-y
- Yank the most recently killed text back into the buffer at the
- cursor.
+`possible-username-completions (C-x ~)'
+ List the possible completions of the text before point, treating
+ it as a username.
-M-y
- Rotate the kill-ring, and yank the new top. You can only do this
- if the prior command is C-y or M-y.
+`complete-variable (M-$)'
+ Attempt completion on the text before point, treating it as a
+ shell variable.
-\1f
-File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
+`possible-variable-completions (C-x $)'
+ List the possible completions of the text before point, treating
+ it as a shell variable.
-Readline Arguments
-------------------
+`complete-hostname (M-@)'
+ Attempt completion on the text before point, treating it as a
+ hostname.
- You can pass numeric arguments to Readline commands. Sometimes the
-argument acts as a repeat count, other times it is the sign of the
-argument that is significant. If you pass a negative argument to a
-command which normally acts in a forward direction, that command will
-act in a backward direction. For example, to kill text back to the
-start of the line, you might type `M-- C-k'.
+`possible-hostname-completions (C-x @)'
+ List the possible completions of the text before point, treating
+ it as a hostname.
- The general way to pass numeric arguments to a command is to type
-meta digits before the command. If the first `digit' you type is a
-minus sign (-), then the sign of the argument will be negative. Once
-you have typed one meta digit to get the argument started, you can type
-the remainder of the digits, and then the command. For example, to give
-the C-d command an argument of 10, you could type `M-1 0 C-d'.
+`complete-command (M-!)'
+ Attempt completion on the text before point, treating it as a
+ command name. Command completion attempts to match the text
+ against aliases, reserved words, shell functions, shell builtins,
+ and finally executable filenames, in that order.
-\1f
-File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
+`possible-command-completions (C-x !)'
+ List the possible completions of the text before point, treating
+ it as a command name.
-Searching for Commands in the History
--------------------------------------
+`dynamic-complete-history (M-<TAB>)'
+ Attempt completion on the text before point, comparing the text
+ against lines from the history list for possible completion
+ matches.
- Readline provides commands for searching through the command history
-(*note Bash History Facilities::.) for lines containing a specified
-string. There are two search modes: INCREMENTAL and NON-INCREMENTAL.
+`dabbrev-expand ()'
+ Attempt menu completion on the text before point, comparing the
+ text against lines from the history list for possible completion
+ matches.
- Incremental searches begin before the user has finished typing the
-search string. As each character of the search string is typed,
-readline displays the next entry from the history matching the string
-typed so far. An incremental search requires only as many characters
-as needed to find the desired history entry. The Escape character is
-used to terminate an incremental search. Control-J will also terminate
-the search. Control-G will abort an incremental search and restore the
-original line. When the search is terminated, the history entry
-containing the search string becomes the current line. To find other
-matching entries in the history list, type Control-S or Control-R as
-appropriate. This will search backward or forward in the history for
-the next entry matching the search string typed so far. Any other key
-sequence bound to a readline command will terminate the search and
-execute that command. For instance, a `newline' will terminate the
-search and accept the line, thereby executing the command from the
-history list.
+`complete-into-braces (M-{)'
+ Perform filename completion and insert the list of possible
+ completions enclosed within braces so the list is available to the
+ shell (*note Brace Expansion::).
- Non-incremental searches read the entire search string before
-starting to search for matching history lines. The search string may be
-typed by the user or part of the contents of the current line.
\1f
-File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
+File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
-Readline Init File
-==================
+8.4.7 Keyboard Macros
+---------------------
- Although the Readline library comes with a set of `emacs'-like
-keybindings installed by default, it is possible that you would like to
-use a different set of keybindings. You can customize programs that
-use Readline by putting commands in an "inputrc" file in your home
-directory. The name of this file is taken from the value of the shell
-variable `INPUTRC'. If that variable is unset, the default is
-`~/.inputrc'.
+`start-kbd-macro (C-x ()'
+ Begin saving the characters typed into the current keyboard macro.
- When a program which uses the Readline library starts up, the init
-file is read, and the key bindings are set.
+`end-kbd-macro (C-x ))'
+ Stop saving the characters typed into the current keyboard macro
+ and save the definition.
- In addition, the `C-x C-r' command re-reads this init file, thus
-incorporating any changes that you might have made to it.
+`call-last-kbd-macro (C-x e)'
+ Re-execute the last keyboard macro defined, by making the
+ characters in the macro appear as if typed at the keyboard.
-* Menu:
-* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
+\1f
+File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
-* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
+8.4.8 Some Miscellaneous Commands
+---------------------------------
-* Sample Init File:: An example inputrc file.
+`re-read-init-file (C-x C-r)'
+ Read in the contents of the INPUTRC file, and incorporate any
+ bindings or variable assignments found there.
-\1f
-File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
+`abort (C-g)'
+ Abort the current editing command and ring the terminal's bell
+ (subject to the setting of `bell-style').
-Readline Init File Syntax
--------------------------
+`do-uppercase-version (M-a, M-b, M-X, ...)'
+ If the metafied character X is lowercase, run the command that is
+ bound to the corresponding uppercase character.
- There are only a few basic constructs allowed in the Readline init
-file. Blank lines are ignored. Lines beginning with a `#' are
-comments. Lines beginning with a `$' indicate conditional constructs
-(*note Conditional Init Constructs::.). Other lines denote variable
-settings and key bindings.
+`prefix-meta (<ESC>)'
+ Metafy the next character typed. This is for keyboards without a
+ meta key. Typing `<ESC> f' is equivalent to typing `M-f'.
-Variable Settings
- You can change the state of a few variables in Readline by using
- the `set' command within the init file. Here is how you would
- specify that you wish to use `vi' line editing commands:
+`undo (C-_ or C-x C-u)'
+ Incremental undo, separately remembered for each line.
- set editing-mode vi
+`revert-line (M-r)'
+ Undo all changes made to this line. This is like executing the
+ `undo' command enough times to get back to the beginning.
- Right now, there are only a few variables which can be set; so
- few, in fact, that we just list them here:
+`tilde-expand (M-&)'
+ Perform tilde expansion on the current word.
- `bell-style'
- Controls what happens when Readline wants to ring the
- terminal bell. If set to `none', Readline never rings the
- bell. If set to `visible', Readline uses a visible bell if
- one is available. If set to `audible' (the default),
- Readline attempts to ring the terminal's bell.
+`set-mark (C-@)'
+ Set the mark to the point. If a numeric argument is supplied, the
+ mark is set to that position.
- `comment-begin'
- The string to insert at the beginning of the line when the
- `insert-comment' command is executed. The default value is
- `"#"'.
+`exchange-point-and-mark (C-x C-x)'
+ Swap the point with the mark. The current cursor position is set
+ to the saved position, and the old cursor position is saved as the
+ mark.
- `completion-query-items'
- The number of possible completions that determines when the
- user is asked whether he wants to see the list of
- possibilities. If the number of possible completions is
- greater than this value, Readline will ask the user whether
- or not he wishes to view them; otherwise, they are simply
- listed. The default limit is `100'.
+`character-search (C-])'
+ A character is read and point is moved to the next occurrence of
+ that character. A negative count searches for previous
+ occurrences.
- `convert-meta'
- If set to `on', Readline will convert characters with the
- eigth bit set to an ASCII key sequence by stripping the eigth
- bit and prepending an ESC character, converting them to a
- meta-prefixed key sequence. The default value is `on'.
+`character-search-backward (M-C-])'
+ A character is read and point is moved to the previous occurrence
+ of that character. A negative count searches for subsequent
+ occurrences.
- `disable-completion'
- If set to `On', readline will inhibit word completion.
- Completion characters will be inserted into the line as if
- they had been mapped to `self-insert'. The default is `off'.
+`insert-comment (M-#)'
+ Without a numeric argument, the value of the `comment-begin'
+ variable is inserted at the beginning of the current line. If a
+ numeric argument is supplied, this command acts as a toggle: if
+ the characters at the beginning of the line do not match the value
+ of `comment-begin', the value is inserted, otherwise the
+ characters in `comment-begin' are deleted from the beginning of
+ the line. In either case, the line is accepted as if a newline
+ had been typed. The default value of `comment-begin' causes this
+ command to make the current line a shell comment. If a numeric
+ argument causes the comment character to be removed, the line will
+ be executed by the shell.
- `editing-mode'
- The `editing-mode' variable controls which editing mode you
- are using. By default, Readline starts up in Emacs editing
- mode, where the keystrokes are most similar to Emacs. This
- variable can be set to either `emacs' or `vi'.
+`dump-functions ()'
+ Print all of the functions and their key bindings to the Readline
+ output stream. If a numeric argument is supplied, the output is
+ formatted in such a way that it can be made part of an INPUTRC
+ file. This command is unbound by default.
- `enable-keypad'
- When set to `on', readline will try to enable the application
- keypad when it is called. Some systems need this to enable
- the arrow keys. The default is `off'.
+`dump-variables ()'
+ Print all of the settable variables and their values to the
+ Readline output stream. If a numeric argument is supplied, the
+ output is formatted in such a way that it can be made part of an
+ INPUTRC file. This command is unbound by default.
- `expand-tilde'
- If set to `on', tilde expansion is performed when Readline
- attempts word completion. The default is `off'.
+`dump-macros ()'
+ Print all of the Readline key sequences bound to macros and the
+ strings they output. If a numeric argument is supplied, the
+ output is formatted in such a way that it can be made part of an
+ INPUTRC file. This command is unbound by default.
- `horizontal-scroll-mode'
- This variable can be set to either `on' or `off'. Setting it
- to `on' means that the text of the lines that you edit will
- scroll horizontally on a single screen line when they are
- longer than the width of the screen, instead of wrapping onto
- a new screen line. By default, this variable is set to `off'.
+`glob-complete-word (M-g)'
+ The word before point is treated as a pattern for pathname
+ expansion, with an asterisk implicitly appended. This pattern is
+ used to generate a list of matching file names for possible
+ completions.
- `keymap'
- Sets Readline's idea of the current keymap for key binding
- commands. Acceptable `keymap' names are `emacs',
- `emacs-standard', `emacs-meta', `emacs-ctlx', `vi',
- `vi-command', and `vi-insert'. `vi' is equivalent to
- `vi-command'; `emacs' is equivalent to `emacs-standard'. The
- default value is `emacs'. The value of the `editing-mode'
- variable also affects the default keymap.
+`glob-expand-word (C-x *)'
+ The word before point is treated as a pattern for pathname
+ expansion, and the list of matching file names is inserted,
+ replacing the word. If a numeric argument is supplied, a `*' is
+ appended before pathname expansion.
+
+`glob-list-expansions (C-x g)'
+ The list of expansions that would have been generated by
+ `glob-expand-word' is displayed, and the line is redrawn. If a
+ numeric argument is supplied, a `*' is appended before pathname
+ expansion.
+
+`display-shell-version (C-x C-v)'
+ Display version information about the current instance of Bash.
+
+`shell-expand-line (M-C-e)'
+ Expand the line as the shell does. This performs alias and
+ history expansion as well as all of the shell word expansions
+ (*note Shell Expansions::).
- `mark-directories'
- If set to `on', completed directory names have a slash
- appended. The default is `on'.
+`history-expand-line (M-^)'
+ Perform history expansion on the current line.
- `mark-modified-lines'
- This variable, when set to `on', says to display an asterisk
- (`*') at the start of history lines which have been modified.
- This variable is `off' by default.
+`magic-space ()'
+ Perform history expansion on the current line and insert a space
+ (*note History Interaction::).
- `input-meta'
- If set to `on', Readline will enable eight-bit input (it will
- not strip the eighth bit from the characters it reads),
- regardless of what the terminal claims it can support. The
- default value is `off'. The name `meta-flag' is a synonym
- for this variable.
+`alias-expand-line ()'
+ Perform alias expansion on the current line (*note Aliases::).
- `output-meta'
- If set to `on', Readline will display characters with the
- eighth bit set directly rather than as a meta-prefixed escape
- sequence. The default is `off'.
+`history-and-alias-expand-line ()'
+ Perform history and alias expansion on the current line.
- `show-all-if-ambiguous'
- This alters the default behavior of the completion functions.
- If set to `on', words which have more than one possible
- completion cause the matches to be listed immediately instead
- of ringing the bell. The default value is `off'.
+`insert-last-argument (M-. or M-_)'
+ A synonym for `yank-last-arg'.
- `visible-stats'
- If set to `on', a character denoting a file's type is
- appended to the filename when listing possible completions.
- The default is `off'.
+`operate-and-get-next (C-o)'
+ Accept the current line for execution and fetch the next line
+ relative to the current line from the history for editing. Any
+ argument is ignored.
-Key Bindings
- The syntax for controlling key bindings in the init file is
- simple. First you have to know the name of the command that you
- want to change. The following pages contain tables of the command
- name, the default keybinding, and a short description of what the
- command does.
+`edit-and-execute-command (C-xC-e)'
+ Invoke an editor on the current command line, and execute the
+ result as shell commands. Bash attempts to invoke `$VISUAL',
+ `$EDITOR', and `emacs' as the editor, in that order.
- Once you know the name of the command, simply place the name of
- the key you wish to bind the command to, a colon, and then the
- name of the command on a line in the init file. The name of the
- key can be expressed in different ways, depending on which is most
- comfortable for you.
- KEYNAME: FUNCTION-NAME or MACRO
- KEYNAME is the name of a key spelled out in English. For
- example:
- Control-u: universal-argument
- Meta-Rubout: backward-kill-word
- Control-o: "> output"
+\1f
+File: bashref.info, Node: Readline vi Mode, Next: Programmable Completion, Prev: Bindable Readline Commands, Up: Command Line Editing
- In the above example, `C-u' is bound to the function
- `universal-argument', and `C-o' is bound to run the macro
- expressed on the right hand side (that is, to insert the text
- `> output' into the line).
+8.5 Readline vi Mode
+====================
- "KEYSEQ": FUNCTION-NAME or MACRO
- KEYSEQ differs from KEYNAME above in that strings denoting an
- entire key sequence can be specified, by placing the key
- sequence in double quotes. Some GNU Emacs style key escapes
- can be used, as in the following example, but the special
- character names are not recognized.
+While the Readline library does not have a full set of `vi' editing
+functions, it does contain enough to allow simple editing of the line.
+The Readline `vi' mode behaves as specified in the POSIX 1003.2
+standard.
- "\C-u": universal-argument
- "\C-x\C-r": re-read-init-file
- "\e[11~": "Function Key 1"
+ In order to switch interactively between `emacs' and `vi' editing
+modes, use the `set -o emacs' and `set -o vi' commands (*note The Set
+Builtin::). The Readline default is `emacs' mode.
- In the above example, `C-u' is bound to the function
- `universal-argument' (just as it was in the first example),
- `C-x C-r' is bound to the function `re-read-init-file', and
- `ESC [ 1 1 ~' is bound to insert the text `Function Key 1'.
- The following escape sequences are available when specifying
- key sequences:
+ When you enter a line in `vi' mode, you are already placed in
+`insertion' mode, as if you had typed an `i'. Pressing <ESC> switches
+you into `command' mode, where you can edit the text of the line with
+the standard `vi' movement keys, move to previous history lines with
+`k' and subsequent lines with `j', and so forth.
- ``\C-''
- control prefix
+\1f
+File: bashref.info, Node: Programmable Completion, Next: Programmable Completion Builtins, Prev: Readline vi Mode, Up: Command Line Editing
- ``\M-''
- meta prefix
+8.6 Programmable Completion
+===========================
- ``\e''
- an escape character
+When word completion is attempted for an argument to a command for
+which a completion specification (a COMPSPEC) has been defined using
+the `complete' builtin (*note Programmable Completion Builtins::), the
+programmable completion facilities are invoked.
+
+ First, the command name is identified. If a compspec has been
+defined for that command, the compspec is used to generate the list of
+possible completions for the word. If the command word is a full
+pathname, a compspec for the full pathname is searched for first. If
+no compspec is found for the full pathname, an attempt is made to find
+a compspec for the portion following the final slash.
+
+ Once a compspec has been found, it is used to generate the list of
+matching words. If a compspec is not found, the default Bash completion
+described above (*note Commands For Completion::) is performed.
+
+ First, the actions specified by the compspec are used. Only matches
+which are prefixed by the word being completed are returned. When the
+`-f' or `-d' option is used for filename or directory name completion,
+the shell variable `FIGNORE' is used to filter the matches. *Note Bash
+Variables::, for a description of `FIGNORE'.
+
+ Any completions specified by a filename expansion pattern to the
+`-G' option are generated next. The words generated by the pattern
+need not match the word being completed. The `GLOBIGNORE' shell
+variable is not used to filter the matches, but the `FIGNORE' shell
+variable is used.
+
+ Next, the string specified as the argument to the `-W' option is
+considered. The string is first split using the characters in the `IFS'
+special variable as delimiters. Shell quoting is honored. Each word
+is then expanded using brace expansion, tilde expansion, parameter and
+variable expansion, command substitution, and arithmetic expansion, as
+described above (*note Shell Expansions::). The results are split
+using the rules described above (*note Word Splitting::). The results
+of the expansion are prefix-matched against the word being completed,
+and the matching words become the possible completions.
+
+ After these matches have been generated, any shell function or
+command specified with the `-F' and `-C' options is invoked. When the
+command or function is invoked, the `COMP_LINE', `COMP_POINT',
+`COMP_KEY', and `COMP_TYPE' variables are assigned values as described
+above (*note Bash Variables::). If a shell function is being invoked,
+the `COMP_WORDS' and `COMP_CWORD' variables are also set. When the
+function or command is invoked, the first argument is the name of the
+command whose arguments are being completed, the second argument is the
+word being completed, and the third argument is the word preceding the
+word being completed on the current command line. No filtering of the
+generated completions against the word being completed is performed;
+the function or command has complete freedom in generating the matches.
+
+ Any function specified with `-F' is invoked first. The function may
+use any of the shell facilities, including the `compgen' and `compopt'
+builtins described below (*note Programmable Completion Builtins::), to
+generate the matches. It must put the possible completions in the
+`COMPREPLY' array variable.
+
+ Next, any command specified with the `-C' option is invoked in an
+environment equivalent to command substitution. It should print a list
+of completions, one per line, to the standard output. Backslash may be
+used to escape a newline, if necessary.
+
+ After all of the possible completions are generated, any filter
+specified with the `-X' option is applied to the list. The filter is a
+pattern as used for pathname expansion; a `&' in the pattern is
+replaced with the text of the word being completed. A literal `&' may
+be escaped with a backslash; the backslash is removed before attempting
+a match. Any completion that matches the pattern will be removed from
+the list. A leading `!' negates the pattern; in this case any
+completion not matching the pattern will be removed.
+
+ Finally, any prefix and suffix specified with the `-P' and `-S'
+options are added to each member of the completion list, and the result
+is returned to the Readline completion code as the list of possible
+completions.
+
+ If the previously-applied actions do not generate any matches, and
+the `-o dirnames' option was supplied to `complete' when the compspec
+was defined, directory name completion is attempted.
+
+ If the `-o plusdirs' option was supplied to `complete' when the
+compspec was defined, directory name completion is attempted and any
+matches are added to the results of the other actions.
+
+ By default, if a compspec is found, whatever it generates is
+returned to the completion code as the full set of possible completions.
+The default Bash completions are not attempted, and the Readline default
+of filename completion is disabled. If the `-o bashdefault' option was
+supplied to `complete' when the compspec was defined, the default Bash
+completions are attempted if the compspec generates no matches. If the
+`-o default' option was supplied to `complete' when the compspec was
+defined, Readline's default completion will be performed if the
+compspec (and, if attempted, the default Bash completions) generate no
+matches.
+
+ When a compspec indicates that directory name completion is desired,
+the programmable completion functions force Readline to append a slash
+to completed names which are symbolic links to directories, subject to
+the value of the MARK-DIRECTORIES Readline variable, regardless of the
+setting of the MARK-SYMLINKED-DIRECTORIES Readline variable.
- ``\\''
- backslash
+\1f
+File: bashref.info, Node: Programmable Completion Builtins, Prev: Programmable Completion, Up: Command Line Editing
- ``\"''
- "
+8.7 Programmable Completion Builtins
+====================================
- ``\'''
- '
+Two builtin commands are available to manipulate the programmable
+completion facilities.
+
+`compgen'
+ `compgen [OPTION] [WORD]'
+
+ Generate possible completion matches for WORD according to the
+ OPTIONs, which may be any option accepted by the `complete'
+ builtin with the exception of `-p' and `-r', and write the matches
+ to the standard output. When using the `-F' or `-C' options, the
+ various shell variables set by the programmable completion
+ facilities, while available, will not have useful values.
+
+ The matches will be generated in the same way as if the
+ programmable completion code had generated them directly from a
+ completion specification with the same flags. If WORD is
+ specified, only those completions matching WORD will be displayed.
- When entering the text of a macro, single or double quotes
- should be used to indicate a macro definition. Unquoted text
- is assumed to be a function name. Backslash will quote any
- character in the macro text, including `"' and `''. For
- example, the following binding will make `C-x \' insert a
- single `\' into the line:
- "\C-x\\": "\\"
+ The return value is true unless an invalid option is supplied, or
+ no matches were generated.
-\1f
-File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
+`complete'
+ `complete [-abcdefgjksuv] [-o COMP-OPTION] [-E] [-A ACTION] [-G GLOBPAT] [-W WORDLIST]
+ [-F FUNCTION] [-C COMMAND] [-X FILTERPAT]
+ [-P PREFIX] [-S SUFFIX] NAME [NAME ...]'
+ `complete -pr [-E] [NAME ...]'
-Conditional Init Constructs
----------------------------
+ Specify how arguments to each NAME should be completed. If the
+ `-p' option is supplied, or if no options are supplied, existing
+ completion specifications are printed in a way that allows them to
+ be reused as input. The `-r' option removes a completion
+ specification for each NAME, or, if no NAMEs are supplied, all
+ completion specifications. The `-E' option indicates that the
+ remaining options and actions should apply to "empty" command
+ completion; that is, completion attempted on a blank line.
- Readline implements a facility similar in spirit to the conditional
-compilation features of the C preprocessor which allows key bindings
-and variable settings to be performed as the result of tests. There
-are three parser directives used.
+ The process of applying these completion specifications when word
+ completion is attempted is described above (*note Programmable
+ Completion::).
-`$if'
- The `$if' construct allows bindings to be made based on the
- editing mode, the terminal being used, or the application using
- Readline. The text of the test extends to the end of the line; no
- characters are required to isolate it.
+ Other options, if specified, have the following meanings. The
+ arguments to the `-G', `-W', and `-X' options (and, if necessary,
+ the `-P' and `-S' options) should be quoted to protect them from
+ expansion before the `complete' builtin is invoked.
- `mode'
- The `mode=' form of the `$if' directive is used to test
- whether Readline is in `emacs' or `vi' mode. This may be
- used in conjunction with the `set keymap' command, for
- instance, to set bindings in the `emacs-standard' and
- `emacs-ctlx' keymaps only if Readline is starting out in
- `emacs' mode.
+ `-o COMP-OPTION'
+ The COMP-OPTION controls several aspects of the compspec's
+ behavior beyond the simple generation of completions.
+ COMP-OPTION may be one of:
- `term'
- The `term=' form may be used to include terminal-specific key
- bindings, perhaps to bind the key sequences output by the
- terminal's function keys. The word on the right side of the
- `=' is tested against the full name of the terminal and the
- portion of the terminal name before the first `-'. This
- allows `sun' to match both `sun' and `sun-cmd', for instance.
+ `bashdefault'
+ Perform the rest of the default Bash completions if the
+ compspec generates no matches.
- `application'
- The APPLICATION construct is used to include
- application-specific settings. Each program using the
- Readline library sets the APPLICATION NAME, and you can test
- for it. This could be used to bind key sequences to
- functions useful for a specific program. For instance, the
- following command adds a key sequence that quotes the current
- or previous word in Bash:
- $if Bash
- # Quote the current or previous word
- "\C-xq": "\eb\"\ef\""
- $endif
+ `default'
+ Use Readline's default filename completion if the
+ compspec generates no matches.
-`$endif'
- This command, as you saw in the previous example, terminates an
- `$if' command.
+ `dirnames'
+ Perform directory name completion if the compspec
+ generates no matches.
-`$else'
- Commands in this branch of the `$if' directive are executed if the
- test fails.
+ `filenames'
+ Tell Readline that the compspec generates filenames, so
+ it can perform any filename-specific processing (like
+ adding a slash to directory names quoting special
+ characters, or suppressing trailing spaces). This
+ option is intended to be used with shell functions
+ specified with `-F'.
-\1f
-File: bashref.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
+ `nospace'
+ Tell Readline not to append a space (the default) to
+ words completed at the end of the line.
-Sample Init File
-----------------
+ `plusdirs'
+ After any matches defined by the compspec are generated,
+ directory name completion is attempted and any matches
+ are added to the results of the other actions.
- Here is an example of an inputrc file. This illustrates key
-binding, variable assignment, and conditional syntax.
+ `-A ACTION'
+ The ACTION may be one of the following to generate a list of
+ possible completions:
- # This file controls the behaviour of line input editing for
- # programs that use the Gnu Readline library. Existing programs
- # include FTP, Bash, and Gdb.
- #
- # You can re-read the inputrc file with C-x C-r.
- # Lines beginning with '#' are comments.
- #
- # Set various bindings for emacs mode.
-
- set editing-mode emacs
-
- $if mode=emacs
-
- Meta-Control-h: backward-kill-word Text after the function name is ignored
-
- #
- # Arrow keys in keypad mode
- #
- #"\M-OD": backward-char
- #"\M-OC": forward-char
- #"\M-OA": previous-history
- #"\M-OB": next-history
- #
- # Arrow keys in ANSI mode
- #
- "\M-[D": backward-char
- "\M-[C": forward-char
- "\M-[A": previous-history
- "\M-[B": next-history
- #
- # Arrow keys in 8 bit keypad mode
- #
- #"\M-\C-OD": backward-char
- #"\M-\C-OC": forward-char
- #"\M-\C-OA": previous-history
- #"\M-\C-OB": next-history
- #
- # Arrow keys in 8 bit ANSI mode
- #
- #"\M-\C-[D": backward-char
- #"\M-\C-[C": forward-char
- #"\M-\C-[A": previous-history
- #"\M-\C-[B": next-history
-
- C-q: quoted-insert
-
- $endif
-
- # An old-style binding. This happens to be the default.
- TAB: complete
-
- # Macros that are convenient for shell interaction
- $if Bash
- # edit the path
- "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
- # prepare to type a quoted word -- insert open and close double quotes
- # and move to just after the open quote
- "\C-x\"": "\"\"\C-b"
- # insert a backslash (testing backslash escapes in sequences and macros)
- "\C-x\\": "\\"
- # Quote the current or previous word
- "\C-xq": "\eb\"\ef\""
- # Add a binding to refresh the line, which is unbound
- "\C-xr": redraw-current-line
- # Edit variable on current line.
- "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
- $endif
-
- # use a visible bell if one is available
- set bell-style visible
-
- # don't strip characters to 7 bits when reading
- set input-meta on
-
- # allow iso-latin1 characters to be inserted rather than converted to
- # prefix-meta sequences
- set convert-meta off
-
- # display characters with the eighth bit set directly rather than
- # as meta-prefixed characters
- set output-meta on
-
- # if there are more than 150 possible completions for a word, ask the
- # user if he wants to see all of them
- set completion-query-items 150
-
- # For FTP
- $if Ftp
- "\C-xg": "get \M-?"
- "\C-xt": "put \M-?"
- "\M-.": yank-last-arg
- $endif
+ `alias'
+ Alias names. May also be specified as `-a'.
-\1f
-File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
+ `arrayvar'
+ Array variable names.
-Bindable Readline Commands
-==========================
+ `binding'
+ Readline key binding names (*note Bindable Readline
+ Commands::).
-* Menu:
+ `builtin'
+ Names of shell builtin commands. May also be specified
+ as `-b'.
-* Commands For Moving:: Moving about the line.
-* Commands For History:: Getting at previous lines.
-* Commands For Text:: Commands for changing text.
-* Commands For Killing:: Commands for killing and yanking.
-* Numeric Arguments:: Specifying numeric arguments, repeat counts.
-* Commands For Completion:: Getting Readline to do the typing for you.
-* Keyboard Macros:: Saving and re-executing typed characters
-* Miscellaneous Commands:: Other miscellaneous commands.
+ `command'
+ Command names. May also be specified as `-c'.
- This section describes Readline commands that may be bound to key
-sequences.
+ `directory'
+ Directory names. May also be specified as `-d'.
+
+ `disabled'
+ Names of disabled shell builtins.
+
+ `enabled'
+ Names of enabled shell builtins.
-\1f
-File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
+ `export'
+ Names of exported shell variables. May also be
+ specified as `-e'.
-Commands For Moving
--------------------
+ `file'
+ File names. May also be specified as `-f'.
-`beginning-of-line (C-a)'
- Move to the start of the current line.
+ `function'
+ Names of shell functions.
-`end-of-line (C-e)'
- Move to the end of the line.
+ `group'
+ Group names. May also be specified as `-g'.
-`forward-char (C-f)'
- Move forward a character.
+ `helptopic'
+ Help topics as accepted by the `help' builtin (*note
+ Bash Builtins::).
-`backward-char (C-b)'
- Move back a character.
+ `hostname'
+ Hostnames, as taken from the file specified by the
+ `HOSTFILE' shell variable (*note Bash Variables::).
-`forward-word (M-f)'
- Move forward to the end of the next word. Words are composed of
- letters and digits.
+ `job'
+ Job names, if job control is active. May also be
+ specified as `-j'.
-`backward-word (M-b)'
- Move back to the start of this, or the previous, word. Words are
- composed of letters and digits.
+ `keyword'
+ Shell reserved words. May also be specified as `-k'.
-`clear-screen (C-l)'
- Clear the screen and redraw the current line, leaving the current
- line at the top of the screen.
+ `running'
+ Names of running jobs, if job control is active.
-`redraw-current-line ()'
- Refresh the current line. By default, this is unbound.
+ `service'
+ Service names. May also be specified as `-s'.
-\1f
-File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
+ `setopt'
+ Valid arguments for the `-o' option to the `set' builtin
+ (*note The Set Builtin::).
-Commands For Manipulating The History
--------------------------------------
+ `shopt'
+ Shell option names as accepted by the `shopt' builtin
+ (*note Bash Builtins::).
-`accept-line (Newline, Return)'
- Accept the line regardless of where the cursor is. If this line is
- non-empty, add it to the history list according to the setting of
- the `HISTCONTROL' variable. If this line was a history line, then
- restore the history line to its original state.
+ `signal'
+ Signal names.
-`previous-history (C-p)'
- Move `up' through the history list.
+ `stopped'
+ Names of stopped jobs, if job control is active.
-`next-history (C-n)'
- Move `down' through the history list.
+ `user'
+ User names. May also be specified as `-u'.
-`beginning-of-history (M-<)'
- Move to the first line in the history.
+ `variable'
+ Names of all shell variables. May also be specified as
+ `-v'.
-`end-of-history (M->)'
- Move to the end of the input history, i.e., the line you are
- entering.
+ `-G GLOBPAT'
+ The filename expansion pattern GLOBPAT is expanded to generate
+ the possible completions.
-`reverse-search-history (C-r)'
- Search backward starting at the current line and moving `up'
- through the history as necessary. This is an incremental search.
+ `-W WORDLIST'
+ The WORDLIST is split using the characters in the `IFS'
+ special variable as delimiters, and each resultant word is
+ expanded. The possible completions are the members of the
+ resultant list which match the word being completed.
-`forward-search-history (C-s)'
- Search forward starting at the current line and moving `down'
- through the the history as necessary. This is an incremental
- search.
+ `-C COMMAND'
+ COMMAND is executed in a subshell environment, and its output
+ is used as the possible completions.
-`non-incremental-reverse-search-history (M-p)'
- Search backward starting at the current line and moving `up'
- through the history as necessary using a non-incremental search
- for a string supplied by the user.
+ `-F FUNCTION'
+ The shell function FUNCTION is executed in the current shell
+ environment. When it finishes, the possible completions are
+ retrieved from the value of the `COMPREPLY' array variable.
-`non-incremental-forward-search-history (M-n)'
- Search forward starting at the current line and moving `down'
- through the the history as necessary using a non-incremental search
- for a string supplied by the user.
+ `-X FILTERPAT'
+ FILTERPAT is a pattern as used for filename expansion. It is
+ applied to the list of possible completions generated by the
+ preceding options and arguments, and each completion matching
+ FILTERPAT is removed from the list. A leading `!' in
+ FILTERPAT negates the pattern; in this case, any completion
+ not matching FILTERPAT is removed.
-`history-search-forward ()'
- Search forward through the history for the string of characters
- between the start of the current line and the current cursor
- position (the `point'). This is a non-incremental search. By
- default, this command is unbound.
+ `-P PREFIX'
+ PREFIX is added at the beginning of each possible completion
+ after all other options have been applied.
-`history-search-backward ()'
- Search backward through the history for the string of characters
- between the start of the current line and the point. This is a
- non-incremental search. By default, this command is unbound.
+ `-S SUFFIX'
+ SUFFIX is appended to each possible completion after all
+ other options have been applied.
-`yank-nth-arg (M-C-y)'
- Insert the first argument to the previous command (usually the
- second word on the previous line). With an argument N, insert the
- Nth word from the previous command (the words in the previous
- command begin with word 0). A negative argument inserts the Nth
- word from the end of the previous command.
+ The return value is true unless an invalid option is supplied, an
+ option other than `-p' or `-r' is supplied without a NAME
+ argument, an attempt is made to remove a completion specification
+ for a NAME for which no specification exists, or an error occurs
+ adding a completion specification.
+
+`compopt'
+ `compopt' [-o OPTION] [+o OPTION] [NAME]
+ Modify completion options for each NAME according to the OPTIONs,
+ or for the currently-execution completion if no NAMEs are supplied.
+ If no OPTIONs are given, display the completion options for each
+ NAME or the current completion. The possible values of OPTION are
+ those valid for the `complete' builtin described above.
+
+ The return value is true unless an invalid option is supplied, an
+ attempt is made to modify the options for a NAME for which no
+ completion specification exists, or an output error occurs.
-`yank-last-arg (M-., M-_)'
- Insert last argument to the previous command (the last word of the
- previous history entry). With an argument, behave exactly like
- `yank-nth-arg'.
\1f
-File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
+File: bashref.info, Node: Using History Interactively, Next: Installing Bash, Prev: Command Line Editing, Up: Top
-Commands For Changing Text
---------------------------
+9 Using History Interactively
+*****************************
+
+This chapter describes how to use the GNU History Library
+interactively, from a user's standpoint. It should be considered a
+user's guide. For information on using the GNU History Library in
+other programs, see the GNU Readline Library Manual.
+
+* Menu:
+
+* Bash History Facilities:: How Bash lets you manipulate your command
+ history.
+* Bash History Builtins:: The Bash builtin commands that manipulate
+ the command history.
+* History Interaction:: What it feels like using History as a user.
+
+\1f
+File: bashref.info, Node: Bash History Facilities, Next: Bash History Builtins, Up: Using History Interactively
-`delete-char (C-d)'
- Delete the character under the cursor. If the cursor is at the
- beginning of the line, there are no characters in the line, and
- the last character typed was not `C-d', then return `EOF'.
+9.1 Bash History Facilities
+===========================
-`backward-delete-char (Rubout)'
- Delete the character behind the cursor. A numeric arg says to kill
- the characters instead of deleting them.
+When the `-o history' option to the `set' builtin is enabled (*note The
+Set Builtin::), the shell provides access to the "command history", the
+list of commands previously typed. The value of the `HISTSIZE' shell
+variable is used as the number of commands to save in a history list.
+The text of the last `$HISTSIZE' commands (default 500) is saved. The
+shell stores each command in the history list prior to parameter and
+variable expansion but after history expansion is performed, subject to
+the values of the shell variables `HISTIGNORE' and `HISTCONTROL'.
+
+ When the shell starts up, the history is initialized from the file
+named by the `HISTFILE' variable (default `~/.bash_history'). The file
+named by the value of `HISTFILE' is truncated, if necessary, to contain
+no more than the number of lines specified by the value of the
+`HISTFILESIZE' variable. When an interactive shell exits, the last
+`$HISTSIZE' lines are copied from the history list to the file named by
+`$HISTFILE'. If the `histappend' shell option is set (*note Bash
+Builtins::), the lines are appended to the history file, otherwise the
+history file is overwritten. If `HISTFILE' is unset, or if the history
+file is unwritable, the history is not saved. After saving the
+history, the history file is truncated to contain no more than
+`$HISTFILESIZE' lines. If `HISTFILESIZE' is not set, no truncation is
+performed.
-`quoted-insert (C-q, C-v)'
- Add the next character that you type to the line verbatim. This is
- how to insert key sequences like C-q, for example.
+ If the `HISTTIMEFORMAT' is set, the time stamp information
+associated with each history entry is written to the history file,
+marked with the history comment character. When the history file is
+read, lines beginning with the history comment character followed
+immediately by a digit are interpreted as timestamps for the previous
+history line.
-`tab-insert (M-TAB)'
- Insert a tab character.
+ The builtin command `fc' may be used to list or edit and re-execute
+a portion of the history list. The `history' builtin may be used to
+display or modify the history list and manipulate the history file.
+When using command-line editing, search commands are available in each
+editing mode that provide access to the history list (*note Commands
+For History::).
-`self-insert (a, b, A, 1, !, ...)'
- Insert yourself.
+ The shell allows control over which commands are saved on the history
+list. The `HISTCONTROL' and `HISTIGNORE' variables may be set to cause
+the shell to save only a subset of the commands entered. The `cmdhist'
+shell option, if enabled, causes the shell to attempt to save each line
+of a multi-line command in the same history entry, adding semicolons
+where necessary to preserve syntactic correctness. The `lithist' shell
+option causes the shell to save the command with embedded newlines
+instead of semicolons. The `shopt' builtin is used to set these
+options. *Note Bash Builtins::, for a description of `shopt'.
-`transpose-chars (C-t)'
- Drag the character before the cursor forward over the character at
- the cursor, moving the cursor forward as well. If the insertion
- point is at the end of the line, then this transposes the last two
- characters of the line. Negative argumentss don't work.
+\1f
+File: bashref.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
-`transpose-words (M-t)'
- Drag the word behind the cursor past the word in front of the
- cursor moving the cursor over that word as well.
+9.2 Bash History Builtins
+=========================
-`upcase-word (M-u)'
- Uppercase the current (or following) word. With a negative
- argument, do the previous word, but do not move the cursor.
+Bash provides two builtin commands which manipulate the history list
+and history file.
-`downcase-word (M-l)'
- Lowercase the current (or following) word. With a negative
- argument, do the previous word, but do not move the cursor.
+`fc'
+ `fc [-e ENAME] [-lnr] [FIRST] [LAST]'
+ `fc -s [PAT=REP] [COMMAND]'
-`capitalize-word (M-c)'
- Capitalize the current (or following) word. With a negative
- argument, do the previous word, but do not move the cursor.
+ Fix Command. In the first form, a range of commands from FIRST to
+ LAST is selected from the history list. Both FIRST and LAST may
+ be specified as a string (to locate the most recent command
+ beginning with that string) or as a number (an index into the
+ history list, where a negative number is used as an offset from the
+ current command number). If LAST is not specified it is set to
+ FIRST. If FIRST is not specified it is set to the previous
+ command for editing and -16 for listing. If the `-l' flag is
+ given, the commands are listed on standard output. The `-n' flag
+ suppresses the command numbers when listing. The `-r' flag
+ reverses the order of the listing. Otherwise, the editor given by
+ ENAME is invoked on a file containing those commands. If ENAME is
+ not given, the value of the following variable expansion is used:
+ `${FCEDIT:-${EDITOR:-vi}}'. This says to use the value of the
+ `FCEDIT' variable if set, or the value of the `EDITOR' variable if
+ that is set, or `vi' if neither is set. When editing is complete,
+ the edited commands are echoed and executed.
-\1f
-File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
+ In the second form, COMMAND is re-executed after each instance of
+ PAT in the selected command is replaced by REP.
-Killing And Yanking
--------------------
+ A useful alias to use with the `fc' command is `r='fc -s'', so
+ that typing `r cc' runs the last command beginning with `cc' and
+ typing `r' re-executes the last command (*note Aliases::).
-`kill-line (C-k)'
- Kill the text from the current cursor position to the end of the
- line.
+`history'
+ history [N]
+ history -c
+ history -d OFFSET
+ history [-anrw] [FILENAME]
+ history -ps ARG
-`backward-kill-line (C-x Rubout)'
- Kill backward to the beginning of the line.
+ With no options, display the history list with line numbers.
+ Lines prefixed with a `*' have been modified. An argument of N
+ lists only the last N lines. If the shell variable
+ `HISTTIMEFORMAT' is set and not null, it is used as a format
+ string for STRFTIME to display the time stamp associated with each
+ displayed history entry. No intervening blank is printed between
+ the formatted time stamp and the history line.
-`unix-line-discard (C-u)'
- Kill backward from the cursor to the beginning of the current line.
- Save the killed text on the kill-ring.
+ Options, if supplied, have the following meanings:
-`kill-whole-line ()'
- Kill all characters on the current line, no matter where the
- cursor is. By default, this is unbound.
+ `-c'
+ Clear the history list. This may be combined with the other
+ options to replace the history list completely.
-`kill-word (M-d)'
- Kill from the cursor to the end of the current word, or if between
- words, to the end of the next word. Word boundaries are the same
- as `forward-word'.
+ `-d OFFSET'
+ Delete the history entry at position OFFSET. OFFSET should
+ be specified as it appears when the history is displayed.
-`backward-kill-word (M-DEL)'
- Kill the word behind the cursor. Word boundaries are the same as
- `backward-word'.
+ `-a'
+ Append the new history lines (history lines entered since the
+ beginning of the current Bash session) to the history file.
-`unix-word-rubout (C-w)'
- Kill the word behind the cursor, using white space as a word
- boundary. The killed text is saved on the kill-ring.
+ `-n'
+ Append the history lines not already read from the history
+ file to the current history list. These are lines appended
+ to the history file since the beginning of the current Bash
+ session.
-`delete-horizontal-space ()'
- Delete all spaces and tabs around point. By default, this is
- unbound.
+ `-r'
+ Read the current history file and append its contents to the
+ history list.
-`kill-region ()'
- Kill the text between the point and the *mark* (saved cursor
- position. This text is referred to as the REGION. By default,
- this command is unbound.
+ `-w'
+ Write out the current history to the history file.
-`copy-region-as-kill ()'
- Copy the text in the region to the kill buffer, so you can yank it
- right away. By default, this command is unbound.
+ `-p'
+ Perform history substitution on the ARGs and display the
+ result on the standard output, without storing the results in
+ the history list.
-`copy-backward-word ()'
- Copy the word before point to the kill buffer. By default, this
- command is unbound.
+ `-s'
+ The ARGs are added to the end of the history list as a single
+ entry.
-`copy-forward-word ()'
- Copy the word following point to the kill buffer. By default,
- this command is unbound.
-`yank (C-y)'
- Yank the top of the kill ring into the buffer at the current
- cursor position.
+ When any of the `-w', `-r', `-a', or `-n' options is used, if
+ FILENAME is given, then it is used as the history file. If not,
+ then the value of the `HISTFILE' variable is used.
-`yank-pop (M-y)'
- Rotate the kill-ring, and yank the new top. You can only do this
- if the prior command is yank or yank-pop.
\1f
-File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
+File: bashref.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
-Specifying Numeric Arguments
-----------------------------
+9.3 History Expansion
+=====================
-`digit-argument (M-0, M-1, ... M--)'
- Add this digit to the argument already accumulating, or start a new
- argument. M- starts a negative argument.
+The History library provides a history expansion feature that is similar
+to the history expansion provided by `csh'. This section describes the
+syntax used to manipulate the history information.
-`universal-argument ()'
- This is another way to specify an argument. If this command is
- followed by one or more digits, optionally with a leading minus
- sign, those digits define the argument. If the command is
- followed by digits, executing `universal-argument' again ends the
- numeric argument, but is otherwise ignored. As a special case, if
- this command is immediately followed by a character that is
- neither a digit or minus sign, the argument count for the next
- command is multiplied by four. The argument count is initially
- one, so executing this function the first time makes the argument
- count four, a second time makes the argument count sixteen, and so
- on. By default, this is not bound to a key.
+ History expansions introduce words from the history list into the
+input stream, making it easy to repeat commands, insert the arguments
+to a previous command into the current input line, or fix errors in
+previous commands quickly.
-\1f
-File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
+ History expansion takes place in two parts. The first is to
+determine which line from the history list should be used during
+substitution. The second is to select portions of that line for
+inclusion into the current one. The line selected from the history is
+called the "event", and the portions of that line that are acted upon
+are called "words". Various "modifiers" are available to manipulate
+the selected words. The line is broken into words in the same fashion
+that Bash does, so that several words surrounded by quotes are
+considered one word. History expansions are introduced by the
+appearance of the history expansion character, which is `!' by default.
+Only `\' and `'' may be used to escape the history expansion character.
-Letting Readline Type For You
------------------------------
+ Several shell options settable with the `shopt' builtin (*note Bash
+Builtins::) may be used to tailor the behavior of history expansion.
+If the `histverify' shell option is enabled, and Readline is being
+used, history substitutions are not immediately passed to the shell
+parser. Instead, the expanded line is reloaded into the Readline
+editing buffer for further modification. If Readline is being used,
+and the `histreedit' shell option is enabled, a failed history
+expansion will be reloaded into the Readline editing buffer for
+correction. The `-p' option to the `history' builtin command may be
+used to see what a history expansion will do before using it. The `-s'
+option to the `history' builtin may be used to add commands to the end
+of the history list without actually executing them, so that they are
+available for subsequent recall. This is most useful in conjunction
+with Readline.
-`complete (TAB)'
- Attempt to do completion on the text before the cursor. This is
- application-specific. Generally, if you are typing a filename
- argument, you can do filename completion; if you are typing a
- command, you can do command completion, if you are typing in a
- symbol to GDB, you can do symbol name completion, if you are
- typing in a variable to Bash, you can do variable name completion,
- and so on. Bash attempts completion treating the text as a
- variable (if the text begins with `$'), username (if the text
- begins with `~'), hostname (if the text begins with `@'), or
- command (including aliases and functions) in turn. If none of
- these produces a match, filename completion is attempted.
+ The shell allows control of the various characters used by the
+history expansion mechanism with the `histchars' variable, as explained
+above (*note Bash Variables::). The shell uses the history comment
+character to mark history timestamps when writing the history file.
-`possible-completions (M-?)'
- List the possible completions of the text before the cursor.
+* Menu:
-`insert-completions (M-*)'
- Insert all completions of the text before point that would have
- been generated by `possible-completions'.
+* Event Designators:: How to specify which history line to use.
+* Word Designators:: Specifying which words are of interest.
+* Modifiers:: Modifying the results of substitution.
-`complete-filename (M-/)'
- Attempt filename completion on the text before point.
+\1f
+File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
-`possible-filename-completions (C-x /)'
- List the possible completions of the text before point, treating
- it as a filename.
+9.3.1 Event Designators
+-----------------------
-`complete-username (M-~)'
- Attempt completion on the text before point, treating it as a
- username.
+An event designator is a reference to a command line entry in the
+history list.
-`possible-username-completions (C-x ~)'
- List the possible completions of the text before point, treating
- it as a username.
+`!'
+ Start a history substitution, except when followed by a space, tab,
+ the end of the line, `=' or `(' (when the `extglob' shell option
+ is enabled using the `shopt' builtin).
-`complete-variable (M-$)'
- Attempt completion on the text before point, treating it as a
- shell variable.
+`!N'
+ Refer to command line N.
-`possible-variable-completions (C-x $)'
- List the possible completions of the text before point, treating
- it as a shell variable.
+`!-N'
+ Refer to the command N lines back.
-`complete-hostname (M-@)'
- Attempt completion on the text before point, treating it as a
- hostname.
+`!!'
+ Refer to the previous command. This is a synonym for `!-1'.
-`possible-hostname-completions (C-x @)'
- List the possible completions of the text before point, treating
- it as a hostname.
+`!STRING'
+ Refer to the most recent command starting with STRING.
-`complete-command (M-!)'
- Attempt completion on the text before point, treating it as a
- command name. Command completion attempts to match the text
- against aliases, reserved words, shell functions, builtins, and
- finally executable filenames, in that order.
+`!?STRING[?]'
+ Refer to the most recent command containing STRING. The trailing
+ `?' may be omitted if the STRING is followed immediately by a
+ newline.
-`possible-command-completions (C-x !)'
- List the possible completions of the text before point, treating
- it as a command name.
+`^STRING1^STRING2^'
+ Quick Substitution. Repeat the last command, replacing STRING1
+ with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
-`dynamic-complete-history (M-TAB)'
- Attempt completion on the text before point, comparing the text
- against lines from the history list for possible completion
- matches.
+`!#'
+ The entire command line typed so far.
-`complete-into-braces (M-{)'
- Perform filename completion and return the list of possible
- completions enclosed within braces so the list is available to the
- shell (*note Brace Expansion::.).
\1f
-File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
-
-Keyboard Macros
----------------
-
-`start-kbd-macro (C-x ()'
- Begin saving the characters typed into the current keyboard macro.
-
-`end-kbd-macro (C-x ))'
- Stop saving the characters typed into the current keyboard macro
- and save the definition.
+File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
-`call-last-kbd-macro (C-x e)'
- Re-execute the last keyboard macro defined, by making the
- characters in the macro appear as if typed at the keyboard.
+9.3.2 Word Designators
+----------------------
-\1f
-File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
+Word designators are used to select desired words from the event. A
+`:' separates the event specification from the word designator. It may
+be omitted if the word designator begins with a `^', `$', `*', `-', or
+`%'. Words are numbered from the beginning of the line, with the first
+word being denoted by 0 (zero). Words are inserted into the current
+line separated by single spaces.
-Some Miscellaneous Commands
----------------------------
+ For example,
-`re-read-init-file (C-x C-r)'
- Read in the contents of the inputrc file, and incorporate any
- bindings or variable assignments found there.
+`!!'
+ designates the preceding command. When you type this, the
+ preceding command is repeated in toto.
-`abort (C-g)'
- Abort the current editing command and ring the terminal's bell
- (subject to the setting of `bell-style').
+`!!:$'
+ designates the last argument of the preceding command. This may be
+ shortened to `!$'.
-`do-uppercase-version (M-a, M-b, M-X, ...)'
- If the metafied character X is lowercase, run the command that is
- bound to the corresponding uppercase character.
+`!fi:2'
+ designates the second argument of the most recent command starting
+ with the letters `fi'.
-`prefix-meta (ESC)'
- Make the next character that you type be metafied. This is for
- people without a meta key. Typing `ESC f' is equivalent to typing
- `M-f'.
+ Here are the word designators:
-`undo (C-_, C-x C-u)'
- Incremental undo, separately remembered for each line.
+`0 (zero)'
+ The `0'th word. For many applications, this is the command word.
-`revert-line (M-r)'
- Undo all changes made to this line. This is like typing the `undo'
- command enough times to get back to the beginning.
+`N'
+ The Nth word.
-`tilde-expand (M-~)'
- Perform tilde expansion on the current word.
+`^'
+ The first argument; that is, word 1.
-`set-mark (C-@)'
- Set the mark to the current point. If a numeric argument is
- supplied, the mark is set to that position.
+`$'
+ The last argument.
-`exchange-point-and-mark (C-x C-x)'
- Swap the point with the mark. The current cursor position is set
- to the saved position, and the old cursor position is saved as the
- mark.
+`%'
+ The word matched by the most recent `?STRING?' search.
-`character-search (C-])'
- A character is read and point is moved to the next occurrence of
- that character. A negative count searches for previous
- occurrences.
+`X-Y'
+ A range of words; `-Y' abbreviates `0-Y'.
-`character-search-backward (M-C-])'
- A character is read and point is moved to the previous occurrence
- of that character. A negative count searches for subsequent
- occurrences.
+`*'
+ All of the words, except the `0'th. This is a synonym for `1-$'.
+ It is not an error to use `*' if there is just one word in the
+ event; the empty string is returned in that case.
-`insert-comment (M-#)'
- The value of the `comment-begin' variable is inserted at the
- beginning of the current line, and the line is accepted as if a
- newline had been typed. This makes the current line a shell
- comment.
+`X*'
+ Abbreviates `X-$'
-`dump-functions ()'
- Print all of the functions and their key bindings to the readline
- output stream. If a numeric argument is supplied, the output is
- formatted in such a way that it can be made part of an INPUTRC
- file. This command is unbound by default.
+`X-'
+ Abbreviates `X-$' like `X*', but omits the last word.
-`dump-variables ()'
- Print all of the settable variables and their values to the
- readline output stream. If a numeric argument is supplied, the
- output is formatted in such a way that it can be made part of an
- INPUTRC file. This command is unbound by default.
-`dump-macros ()'
- Print all of the readline key sequences bound to macros and the
- strings they ouput. If a numeric argument is supplied, the output
- is formatted in such a way that it can be made part of an INPUTRC
- file. This command is unbound by default.
+ If a word designator is supplied without an event specification, the
+previous command is used as the event.
-`glob-expand-word (C-x *)'
- The word before point is treated as a pattern for pathname
- expansion, and the list of matching file names is inserted,
- replacing the word.
+\1f
+File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
-`glob-list-expansions (C-x g)'
- The list of expansions that would have been generated by
- `glob-expand-word' is inserted into the line, replacing the word
- before point.
+9.3.3 Modifiers
+---------------
-`display-shell-version (C-x C-v)'
- Display version information about the current instance of Bash.
+After the optional word designator, you can add a sequence of one or
+more of the following modifiers, each preceded by a `:'.
-`shell-expand-line (M-C-e)'
- Expand the line the way the shell does when it reads it. This
- performs alias and history expansion as well as all of the shell
- word expansions.
+`h'
+ Remove a trailing pathname component, leaving only the head.
-`history-expand-line (M-^)'
- Perform history expansion on the current line.
+`t'
+ Remove all leading pathname components, leaving the tail.
-`alias-expand-line'
- Perform alias expansion on the current line (*note Aliases::.).
+`r'
+ Remove a trailing suffix of the form `.SUFFIX', leaving the
+ basename.
-`history-and-alias-expand-line'
- Perform history and alias expansion on the current line.
+`e'
+ Remove all but the trailing suffix.
-`insert-last-argument (M-., M-_)'
- A synonym for `yank-last-arg'.
+`p'
+ Print the new command but do not execute it.
-`operate-and-get-next (C-o)'
- Accept the current line for execution and fetch the next line
- relative to the current line from the history for editing. Any
- argument is ignored.
+`q'
+ Quote the substituted words, escaping further substitutions.
-`emacs-editing-mode (C-e)'
- When in `vi' editing mode, this causes a switch back to `emacs'
- editing mode, as if the command `set -o emacs' had been executed.
+`x'
+ Quote the substituted words as with `q', but break into words at
+ spaces, tabs, and newlines.
-\1f
-File: bashref.info, Node: Readline vi Mode, Prev: Bindable Readline Commands, Up: Command Line Editing
+`s/OLD/NEW/'
+ Substitute NEW for the first occurrence of OLD in the event line.
+ Any delimiter may be used in place of `/'. The delimiter may be
+ quoted in OLD and NEW with a single backslash. If `&' appears in
+ NEW, it is replaced by OLD. A single backslash will quote the
+ `&'. The final delimiter is optional if it is the last character
+ on the input line.
-Readline vi Mode
-================
+`&'
+ Repeat the previous substitution.
- While the Readline library does not have a full set of `vi' editing
-functions, it does contain enough to allow simple editing of the line.
-The Readline `vi' mode behaves as specified in the POSIX 1003.2
-standard.
+`g'
+`a'
+ Cause changes to be applied over the entire event line. Used in
+ conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
- In order to switch interactively between `emacs' and `vi' editing
-modes, use the `set -o emacs' and `set -o vi' commands (*note The Set
-Builtin::.). The Readline default is `emacs' mode.
+`G'
+ Apply the following `s' modifier once to each word in the event.
- When you enter a line in `vi' mode, you are already placed in
-`insertion' mode, as if you had typed an `i'. Pressing ESC switches
-you into `command' mode, where you can edit the text of the line with
-the standard `vi' movement keys, move to previous history lines with
-`k' and subsequent lines with `j', and so forth.
\1f
-File: bashref.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Command Line Editing, Up: Top
+File: bashref.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Using History Interactively, Up: Top
-Installing Bash
-***************
+10 Installing Bash
+******************
- This chapter provides basic instructions for installing Bash on the
-various supported platforms. The distribution supports nearly every
-version of Unix (and, someday, GNU). Other independent ports exist for
-OS/2, Windows 95, and Windows NT.
+This chapter provides basic instructions for installing Bash on the
+various supported platforms. The distribution supports the GNU
+operating systems, nearly every version of Unix, and several non-Unix
+systems such as BeOS and Interix. Other independent ports exist for
+MS-DOS, OS/2, and Windows platforms.
* Menu:
* Basic Installation:: Installation instructions.
-
* Compilers and Options:: How to set special options for various
systems.
-
* Compiling For Multiple Architectures:: How to compile Bash for more
than one kind of system from
the same source tree.
-
* Installation Names:: How to set the various paths used by the installation.
-
* Specifying the System Type:: How to configure Bash for a particular system.
-
* Sharing Defaults:: How to share default configuration values among GNU
programs.
-
* Operation Controls:: Options recognized by the configuration program.
-
* Optional Features:: How to enable and disable optional features when
building Bash.
\1f
File: bashref.info, Node: Basic Installation, Next: Compilers and Options, Up: Installing Bash
-Basic Installation
-==================
-
- These are installation instructions for Bash.
-
- The `configure' shell script attempts to guess correct values for
-various system-dependent variables used during compilation. It uses
-those values to create a `Makefile' in each directory of the package
-(the top directory, the `builtins' and `doc' directories, and the each
-directory under `lib'). It also creates a `config.h' file containing
-system-dependent definitions. Finally, it creates a shell script named
-`config.status' that you can run in the future to recreate the current
-configuration, a file `config.cache' that saves the results of its
-tests to speed up reconfiguring, and a file `config.log' containing
-compiler output (useful mainly for debugging `configure'). If at some
-point `config.cache' contains results you don't want to keep, you may
-remove or edit it.
-
- If you need to do unusual things to compile the package, please try
-to figure out how `configure' could check whether or not to do them,
-and mail diffs or instructions to `bash-maintainers@prep.ai.mit.edu' so
-they can be considered for the next release.
-
- The file `configure.in' is used to create `configure' by a program
-called Autoconf. You only need `configure.in' if you want to change it
-or regenerate `configure' using a newer version of Autoconf. If you do
-this, make sure you are using Autoconf version 2.10 or newer.
+10.1 Basic Installation
+=======================
- If you need to change `configure.in' or regenerate `configure', you
-will need to create two files: `_distribution' and `_patchlevel'.
-`_distribution' should contain the major and minor version numbers of
-the Bash distribution, for example `2.01'. `_patchlevel' should
-contain the patch level of the Bash distribution, `0' for example. The
-script `support/mkconffiles' has been provided to automate the creation
-of these files.
+These are installation instructions for Bash.
The simplest way to compile Bash is:
./configure' instead to prevent `csh' from trying to execute
`configure' itself.
- Running `configure' takes awhile. While running, it prints some
+ Running `configure' takes some time. While running, it prints
messages telling which features it is checking for.
2. Type `make' to compile Bash and build the `bashbug' bug reporting
also install the manual pages and Info file.
+ The `configure' shell script attempts to guess correct values for
+various system-dependent variables used during compilation. It uses
+those values to create a `Makefile' in each directory of the package
+(the top directory, the `builtins', `doc', and `support' directories,
+each directory under `lib', and several others). It also creates a
+`config.h' file containing system-dependent definitions. Finally, it
+creates a shell script named `config.status' that you can run in the
+future to recreate the current configuration, a file `config.cache'
+that saves the results of its tests to speed up reconfiguring, and a
+file `config.log' containing compiler output (useful mainly for
+debugging `configure'). If at some point `config.cache' contains
+results you don't want to keep, you may remove or edit it.
+
+ To find out more about the options and arguments that the
+`configure' script understands, type
+
+ bash-2.04$ ./configure --help
+
+at the Bash prompt in your Bash source directory.
+
+ If you need to do unusual things to compile Bash, please try to
+figure out how `configure' could check whether or not to do them, and
+mail diffs or instructions to <bash-maintainers@gnu.org> so they can be
+considered for the next release.
+
+ The file `configure.in' is used to create `configure' by a program
+called Autoconf. You only need `configure.in' if you want to change it
+or regenerate `configure' using a newer version of Autoconf. If you do
+this, make sure you are using Autoconf version 2.50 or newer.
+
You can remove the program binaries and object files from the source
code directory by typing `make clean'. To also remove the files that
`configure' created (so you can compile Bash for a different kind of
\1f
File: bashref.info, Node: Compilers and Options, Next: Compiling For Multiple Architectures, Prev: Basic Installation, Up: Installing Bash
-Compilers and Options
-=====================
+10.2 Compilers and Options
+==========================
- Some systems require unusual options for compilation or linking that
+Some systems require unusual options for compilation or linking that
the `configure' script does not know about. You can give `configure'
initial values for variables by setting them in the environment. Using
a Bourne-compatible shell, you can do that on the command line like
\1f
File: bashref.info, Node: Compiling For Multiple Architectures, Next: Installation Names, Prev: Compilers and Options, Up: Installing Bash
-Compiling For Multiple Architectures
-====================================
+10.3 Compiling For Multiple Architectures
+=========================================
- You can compile Bash for more than one kind of computer at the same
+You can compile Bash for more than one kind of computer at the same
time, by placing the object files for each architecture in their own
directory. To do this, you must use a version of `make' that supports
the `VPATH' variable, such as GNU `make'. `cd' to the directory where
\1f
File: bashref.info, Node: Installation Names, Next: Specifying the System Type, Prev: Compiling For Multiple Architectures, Up: Installing Bash
-Installation Names
-==================
+10.4 Installation Names
+=======================
- By default, `make install' will install into `/usr/local/bin',
+By default, `make install' will install into `/usr/local/bin',
`/usr/local/man', etc. You can specify an installation prefix other
-than `/usr/local' by giving `configure' the option `--prefix=PATH'.
+than `/usr/local' by giving `configure' the option `--prefix=PATH', or
+by specifying a value for the `DESTDIR' `make' variable when running
+`make install'.
You can specify separate installation prefixes for
architecture-specific files and architecture-independent files. If you
-give `configure' the option `--exec-prefix=PATH', the package will use
-`PATH' as the prefix for installing programs and libraries.
+give `configure' the option `--exec-prefix=PATH', `make install' will
+use PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.
\1f
File: bashref.info, Node: Specifying the System Type, Next: Sharing Defaults, Prev: Installation Names, Up: Installing Bash
-Specifying the System Type
-==========================
+10.5 Specifying the System Type
+===============================
- There may be some features `configure' can not figure out
-automatically, but needs to determine by the type of host the package
-will run on. Usually `configure' can figure that out, but if it prints
-a message saying it can not guess the host type, give it the
+There may be some features `configure' can not figure out
+automatically, but need to determine by the type of host Bash will run
+on. Usually `configure' can figure that out, but if it prints a
+message saying it can not guess the host type, give it the
`--host=TYPE' option. `TYPE' can either be a short name for the system
type, such as `sun4', or a canonical name with three fields:
-`CPU-COMPANY-SYSTEM' (e.g., `sparc-sun-sunos4.1.2').
+`CPU-COMPANY-SYSTEM' (e.g., `i386-unknown-freebsd4.2').
-See the file `support/config.sub' for the possible values of each field.
+ See the file `support/config.sub' for the possible values of each
+field.
\1f
File: bashref.info, Node: Sharing Defaults, Next: Operation Controls, Prev: Specifying the System Type, Up: Installing Bash
-Sharing Defaults
-================
+10.6 Sharing Defaults
+=====================
- If you want to set default values for `configure' scripts to share,
-you can create a site shell script called `config.site' that gives
-default values for variables like `CC', `cache_file', and `prefix'.
-`configure' looks for `PREFIX/share/config.site' if it exists, then
+If you want to set default values for `configure' scripts to share, you
+can create a site shell script called `config.site' that gives default
+values for variables like `CC', `cache_file', and `prefix'. `configure'
+looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists. Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: the Bash `configure' looks for a site script, but not all
\1f
File: bashref.info, Node: Operation Controls, Next: Optional Features, Prev: Sharing Defaults, Up: Installing Bash
-Operation Controls
-==================
+10.7 Operation Controls
+=======================
- `configure' recognizes the following options to control how it
-operates.
+`configure' recognizes the following options to control how it operates.
`--cache-file=FILE'
Use and save the results of the tests in FILE instead of
script, and exit.
`configure' also accepts some other, not widely used, boilerplate
-options.
+options. `configure --help' prints the complete list.
\1f
File: bashref.info, Node: Optional Features, Prev: Operation Controls, Up: Installing Bash
-Optional Features
-=================
+10.8 Optional Features
+======================
- The Bash `configure' has a number of `--enable-FEATURE' options,
-where FEATURE indicates an optional part of the package. There are
-also several `--with-PACKAGE' options, where PACKAGE is something like
-`gnu-malloc' or `purify' (for the Purify memory allocation checker). To
-turn off the default use of a package, use `--without-PACKAGE'. To
-configure Bash without a feature that is enabled by default, use
-`--disable-FEATURE'.
+The Bash `configure' has a number of `--enable-FEATURE' options, where
+FEATURE indicates an optional part of Bash. There are also several
+`--with-PACKAGE' options, where PACKAGE is something like `bash-malloc'
+or `purify'. To turn off the default use of a package, use
+`--without-PACKAGE'. To configure Bash without a feature that is
+enabled by default, use `--disable-FEATURE'.
Here is a complete list of the `--enable-' and `--with-' options
that the Bash `configure' recognizes.
`--with-afs'
Define if you are using the Andrew File System from Transarc.
+`--with-bash-malloc'
+ Use the Bash version of `malloc' in the directory `lib/malloc'.
+ This is not the same `malloc' that appears in GNU libc, but an
+ older version originally derived from the 4.2 BSD `malloc'. This
+ `malloc' is very fast, but wastes some space on each allocation.
+ This option is enabled by default. The `NOTES' file contains a
+ list of systems for which this should be turned off, and
+ `configure' disables this option automatically for a number of
+ systems.
+
`--with-curses'
Use the curses library instead of the termcap library. This should
be supplied if your system has an inadequate or incomplete termcap
database.
-`--with-glibc-malloc'
- Use the GNU libc version of `malloc' in `lib/malloc/gmalloc.c'.
- This is somewhat slower than the default `malloc', but wastes
- considerably less space.
-
`--with-gnu-malloc'
- Use the GNU version of `malloc' in `lib/malloc/malloc.c'. This is
- not the same `malloc' that appears in GNU libc, but an older
- version derived from the 4.2 BSD `malloc'. This `malloc' is very
- fast, but wastes a lot of space. This option is enabled by
- default. The `NOTES' file contains a list of systems for which
- this should be turned off, and `configure' disables this option
- automatically for a number of systems.
+ A synonym for `--with-bash-malloc'.
+
+`--with-installed-readline[=PREFIX]'
+ Define this to make Bash link with a locally-installed version of
+ Readline rather than the version in `lib/readline'. This works
+ only with Readline 5.0 and later versions. If PREFIX is `yes' or
+ not supplied, `configure' uses the values of the make variables
+ `includedir' and `libdir', which are subdirectories of `prefix' by
+ default, to find the installed version of Readline if it is not in
+ the standard system include and library directories. If PREFIX is
+ `no', Bash links with the version in `lib/readline'. If PREFIX is
+ set to any other value, `configure' treats it as a directory
+ pathname and looks for the installed version of Readline in
+ subdirectories of that directory (include files in
+ PREFIX/`include' and the library in PREFIX/`lib').
`--with-purify'
- Define this to use the Purify memory allocation checker from Pure
- Software.
+ Define this to use the Purify memory allocation checker from
+ Rational Software.
`--enable-minimal-config'
This produces a shell with minimal features, close to the
historical Bourne shell.
-The `minimal-config' option can be used to disable all of the following
-options, but it is processed first, so individual options may be
-enabled using `enable-FEATURE'.
+ There are several `--enable-' options that alter how Bash is
+compiled and linked, rather than changing run-time features.
+
+`--enable-largefile'
+ Enable support for large files
+ (http://www.sas.com/standards/large_file/x_open.20Mar96.html) if
+ the operating system requires special compiler options to build
+ programs which can access large files. This is enabled by
+ default, if the operating system provides large file support.
+
+`--enable-profiling'
+ This builds a Bash binary that produces profiling information to be
+ processed by `gprof' each time it is executed.
+
+`--enable-static-link'
+ This causes Bash to be linked statically, if `gcc' is being used.
+ This could be used to build a version to use as root's shell.
+
+ The `minimal-config' option can be used to disable all of the
+following options, but it is processed first, so individual options may
+be enabled using `enable-FEATURE'.
All of the following options except for `disabled-builtins' and
-`usg-echo-default' are enabled by default, unless the operating system
+`xpg-echo-default' are enabled by default, unless the operating system
does not provide the necessary support.
`--enable-alias'
Allow alias expansion and include the `alias' and `unalias'
- builtins.
+ builtins (*note Aliases::).
+
+`--enable-arith-for-command'
+ Include support for the alternate form of the `for' command that
+ behaves like the C language `for' statement (*note Looping
+ Constructs::).
`--enable-array-variables'
- Include support for one-dimensional array shell variables.
+ Include support for one-dimensional array shell variables (*note
+ Arrays::).
`--enable-bang-history'
- Include support for `csh'-like history substitution.
+ Include support for `csh'-like history substitution (*note History
+ Interaction::).
`--enable-brace-expansion'
Include `csh'-like brace expansion ( `b{a,b}c' ==> `bac bbc' ).
+ See *note Brace Expansion::, for a complete description.
+
+`--enable-casemod-attributes'
+ Include support for case-modifying attributes in the `declare'
+ builtin and assignment statements. Variables with the UPPERCASE
+ attribute, for example, will have their values converted to
+ uppercase upon assignment.
+
+`--enable-casemod-expansion'
+ Include support for case-modifying word expansions.
`--enable-command-timing'
Include support for recognizing `time' as a reserved word and for
- displaying timing statistics for the pipeline following `time'.
- This allows pipelines as well as shell builtins and functions to
- be timed.
+ displaying timing statistics for the pipeline following `time'
+ (*note Pipelines::). This allows pipelines as well as shell
+ builtins and functions to be timed.
+
+`--enable-cond-command'
+ Include support for the `[[' conditional command. (*note
+ Conditional Constructs::).
+
+`--enable-cond-regexp'
+ Include support for matching POSIX regular expressions using the
+ `=~' binary operator in the `[[' conditional command. (*note
+ Conditional Constructs::).
+
+`--enable-coprocesses'
+ Include support for coprocesses and the `coproc' reserved word
+ (*note Pipelines::).
+
+`--enable-debugger'
+ Include support for the bash debugger (distributed separately).
`--enable-directory-stack'
Include support for a `csh'-like directory stack and the `pushd',
- `popd', and `dirs' builtins.
+ `popd', and `dirs' builtins (*note The Directory Stack::).
`--enable-disabled-builtins'
Allow builtin commands to be invoked via `builtin xxx' even after
- `xxx' has been disabled using `enable -n xxx'. See *Note Bash
+ `xxx' has been disabled using `enable -n xxx'. See *note Bash
Builtins::, for details of the `builtin' and `enable' builtin
commands.
`--enable-dparen-arithmetic'
- Include support for the `ksh' `((...))' command.
+ Include support for the `((...))' command (*note Conditional
+ Constructs::).
+
+`--enable-extended-glob'
+ Include support for the extended pattern matching features
+ described above under *note Pattern Matching::.
`--enable-help-builtin'
Include the `help' builtin, which displays help on shell builtins
- and variables.
+ and variables (*note Bash Builtins::).
`--enable-history'
Include command history and the `fc' and `history' builtin
- commands.
+ commands (*note Bash History Facilities::).
`--enable-job-control'
- This enables job control features, if the OS supports them.
+ This enables the job control features (*note Job Control::), if
+ the operating system supports them.
+
+`--enable-multibyte'
+ This enables support for multibyte characters if the operating
+ system provides the necessary support.
+
+`--enable-net-redirections'
+ This enables the special handling of filenames of the form
+ `/dev/tcp/HOST/PORT' and `/dev/udp/HOST/PORT' when used in
+ redirections (*note Redirections::).
`--enable-process-substitution'
- This enables process substitution (*note Process Substitution::.)
- if the OS provides the necessary support.
+ This enables process substitution (*note Process Substitution::) if
+ the operating system provides the necessary support.
+
+`--enable-progcomp'
+ Enable the programmable completion facilities (*note Programmable
+ Completion::). If Readline is not enabled, this option has no
+ effect.
`--enable-prompt-string-decoding'
Turn on the interpretation of a number of backslash-escaped
characters in the `$PS1', `$PS2', `$PS3', and `$PS4' prompt
- strings.
+ strings. See *note Printing a Prompt::, for a complete list of
+ prompt string escape sequences.
`--enable-readline'
Include support for command-line editing and history with the Bash
- version of the Readline library.
+ version of the Readline library (*note Command Line Editing::).
`--enable-restricted'
Include support for a "restricted shell". If this is enabled,
- Bash, when called as `rbash', enters a restricted mode. See *Note
+ Bash, when called as `rbash', enters a restricted mode. See *note
The Restricted Shell::, for a description of restricted mode.
`--enable-select'
- Include the `ksh' `select' builtin, which allows the generation of
- simple menus.
+ Include the `select' builtin, which allows the generation of simple
+ menus (*note Conditional Constructs::).
+
+`--enable-separate-helpfiles'
+ Use external files for the documentation displayed by the `help'
+ builtin instead of storing the text internally.
+
+`--enable-single-help-strings'
+ Store the text displayed by the `help' builtin as a single string
+ for each help topic. This aids in translating the text to
+ different languages. You may need to disable this if your
+ compiler cannot handle very long string literals.
+
+`--enable-strict-posix-default'
+ Make Bash POSIX-conformant by default (*note Bash POSIX Mode::).
`--enable-usg-echo-default'
+ A synonym for `--enable-xpg-echo-default'.
+
+`--enable-xpg-echo-default'
Make the `echo' builtin expand backslash-escaped characters by
- default, without requiring the `-e' option. This makes the Bash
- `echo' behave more like the System V version.
+ default, without requiring the `-e' option. This sets the default
+ value of the `xpg_echo' shell option to `on', which makes the Bash
+ `echo' behave more like the version specified in the Single Unix
+ Specification, version 3. *Note Bash Builtins::, for a
+ description of the escape sequences that `echo' recognizes.
- The file `config.h.top' contains C Preprocessor `#define' statements
+
+ The file `config-top.h' contains C Preprocessor `#define' statements
for options which are not settable from `configure'. Some of these are
not meant to be changed; beware of the consequences if you do. Read
the comments associated with each definition for more information about
its effect.
\1f
-File: bashref.info, Node: Reporting Bugs, Next: Builtin Index, Prev: Installing Bash, Up: Top
+File: bashref.info, Node: Reporting Bugs, Next: Major Differences From The Bourne Shell, Prev: Installing Bash, Up: Top
-Reporting Bugs
-**************
+Appendix A Reporting Bugs
+*************************
- Please report all bugs you find in Bash. But first, you should make
+Please report all bugs you find in Bash. But first, you should make
sure that it really is a bug, and that it appears in the latest version
-of Bash that you have.
+of Bash. The latest version of Bash is always available for FTP from
+`ftp://ftp.gnu.org/pub/bash/'.
Once you have determined that a bug actually exists, use the
`bashbug' command to submit a bug report. If you have a fix, you are
encouraged to mail that as well! Suggestions and `philosophical' bug
-reports may be mailed to `bug-bash@prep.ai.MIT.Edu' or posted to the
-Usenet newsgroup `gnu.bash.bug'.
+reports may be mailed to <bug-bash@gnu.org> or posted to the Usenet
+newsgroup `gnu.bash.bug'.
All bug reports should include:
* The version number of Bash.
`bashbug' inserts the first three items automatically into the template
it provides for filing a bug report.
- Please send all reports concerning this manual to
-`chet@ins.CWRU.Edu'.
+ Please send all reports concerning this manual to <chet@po.CWRU.Edu>.
+
+\1f
+File: bashref.info, Node: Major Differences From The Bourne Shell, Next: GNU Free Documentation License, Prev: Reporting Bugs, Up: Top
+
+Appendix B Major Differences From The Bourne Shell
+**************************************************
+
+Bash implements essentially the same grammar, parameter and variable
+expansion, redirection, and quoting as the Bourne Shell. Bash uses the
+POSIX standard as the specification of how these features are to be
+implemented. There are some differences between the traditional Bourne
+shell and Bash; this section quickly details the differences of
+significance. A number of these differences are explained in greater
+depth in previous sections. This section uses the version of `sh'
+included in SVR4.2 (the last version of the historical Bourne shell) as
+the baseline reference.
+
+ * Bash is POSIX-conformant, even where the POSIX specification
+ differs from traditional `sh' behavior (*note Bash POSIX Mode::).
+
+ * Bash has multi-character invocation options (*note Invoking
+ Bash::).
+
+ * Bash has command-line editing (*note Command Line Editing::) and
+ the `bind' builtin.
+
+ * Bash provides a programmable word completion mechanism (*note
+ Programmable Completion::), and builtin commands `complete',
+ `compgen', and `compopt', to manipulate it.
+
+ * Bash has command history (*note Bash History Facilities::) and the
+ `history' and `fc' builtins to manipulate it. The Bash history
+ list maintains timestamp information and uses the value of the
+ `HISTTIMEFORMAT' variable to display it.
+
+ * Bash implements `csh'-like history expansion (*note History
+ Interaction::).
+
+ * Bash has one-dimensional array variables (*note Arrays::), and the
+ appropriate variable expansions and assignment syntax to use them.
+ Several of the Bash builtins take options to act on arrays. Bash
+ provides a number of built-in array variables.
+
+ * The `$'...'' quoting syntax, which expands ANSI-C
+ backslash-escaped characters in the text between the single quotes,
+ is supported (*note ANSI-C Quoting::).
+
+ * Bash supports the `$"..."' quoting syntax to do locale-specific
+ translation of the characters between the double quotes. The
+ `-D', `--dump-strings', and `--dump-po-strings' invocation options
+ list the translatable strings found in a script (*note Locale
+ Translation::).
+
+ * Bash implements the `!' keyword to negate the return value of a
+ pipeline (*note Pipelines::). Very useful when an `if' statement
+ needs to act only if a test fails. The Bash `-o pipefail' option
+ to `set' will cause a pipeline to return a failure status if any
+ command fails.
+
+ * Bash has the `time' reserved word and command timing (*note
+ Pipelines::). The display of the timing statistics may be
+ controlled with the `TIMEFORMAT' variable.
+
+ * Bash implements the `for (( EXPR1 ; EXPR2 ; EXPR3 ))' arithmetic
+ for command, similar to the C language (*note Looping
+ Constructs::).
+
+ * Bash includes the `select' compound command, which allows the
+ generation of simple menus (*note Conditional Constructs::).
+
+ * Bash includes the `[[' compound command, which makes conditional
+ testing part of the shell grammar (*note Conditional
+ Constructs::), including optional regular expression matching.
+
+ * Bash provides optional case-insensitive matching for the `case' and
+ `[[' constructs.
+
+ * Bash includes brace expansion (*note Brace Expansion::) and tilde
+ expansion (*note Tilde Expansion::).
+
+ * Bash implements command aliases and the `alias' and `unalias'
+ builtins (*note Aliases::).
+
+ * Bash provides shell arithmetic, the `((' compound command (*note
+ Conditional Constructs::), and arithmetic expansion (*note Shell
+ Arithmetic::).
+
+ * Variables present in the shell's initial environment are
+ automatically exported to child processes. The Bourne shell does
+ not normally do this unless the variables are explicitly marked
+ using the `export' command.
+
+ * Bash supports the `+=' assignment operator, which appends to the
+ value of the variable named on the left hand side.
+
+ * Bash includes the POSIX pattern removal `%', `#', `%%' and `##'
+ expansions to remove leading or trailing substrings from variable
+ values (*note Shell Parameter Expansion::).
+
+ * The expansion `${#xx}', which returns the length of `${xx}', is
+ supported (*note Shell Parameter Expansion::).
+
+ * The expansion `${var:'OFFSET`[:'LENGTH`]}', which expands to the
+ substring of `var''s value of length LENGTH, beginning at OFFSET,
+ is present (*note Shell Parameter Expansion::).
+
+ * The expansion `${var/[/]'PATTERN`[/'REPLACEMENT`]}', which matches
+ PATTERN and replaces it with REPLACEMENT in the value of `var', is
+ available (*note Shell Parameter Expansion::).
+
+ * The expansion `${!PREFIX}*' expansion, which expands to the names
+ of all shell variables whose names begin with PREFIX, is available
+ (*note Shell Parameter Expansion::).
+
+ * Bash has INDIRECT variable expansion using `${!word}' (*note Shell
+ Parameter Expansion::).
+
+ * Bash can expand positional parameters beyond `$9' using `${NUM}'.
+
+ * The POSIX `$()' form of command substitution is implemented (*note
+ Command Substitution::), and preferred to the Bourne shell's ```'
+ (which is also implemented for backwards compatibility).
+
+ * Bash has process substitution (*note Process Substitution::).
+
+ * Bash automatically assigns variables that provide information
+ about the current user (`UID', `EUID', and `GROUPS'), the current
+ host (`HOSTTYPE', `OSTYPE', `MACHTYPE', and `HOSTNAME'), and the
+ instance of Bash that is running (`BASH', `BASH_VERSION', and
+ `BASH_VERSINFO'). *Note Bash Variables::, for details.
+
+ * The `IFS' variable is used to split only the results of expansion,
+ not all words (*note Word Splitting::). This closes a
+ longstanding shell security hole.
+
+ * Bash implements the full set of POSIX filename expansion operators,
+ including CHARACTER CLASSES, EQUIVALENCE CLASSES, and COLLATING
+ SYMBOLS (*note Filename Expansion::).
+
+ * Bash implements extended pattern matching features when the
+ `extglob' shell option is enabled (*note Pattern Matching::).
+
+ * It is possible to have a variable and a function with the same
+ name; `sh' does not separate the two name spaces.
+
+ * Bash functions are permitted to have local variables using the
+ `local' builtin, and thus useful recursive functions may be written
+ (*note Bash Builtins::).
+
+ * Variable assignments preceding commands affect only that command,
+ even builtins and functions (*note Environment::). In `sh', all
+ variable assignments preceding commands are global unless the
+ command is executed from the file system.
+
+ * Bash performs filename expansion on filenames specified as operands
+ to input and output redirection operators (*note Redirections::).
+
+ * Bash contains the `<>' redirection operator, allowing a file to be
+ opened for both reading and writing, and the `&>' redirection
+ operator, for directing standard output and standard error to the
+ same file (*note Redirections::).
+
+ * Bash includes the `<<<' redirection operator, allowing a string to
+ be used as the standard input to a command.
+
+ * Bash implements the `[n]<&WORD' and `[n]>&WORD' redirection
+ operators, which move one file descriptor to another.
+
+ * Bash treats a number of filenames specially when they are used in
+ redirection operators (*note Redirections::).
+
+ * Bash can open network connections to arbitrary machines and
+ services with the redirection operators (*note Redirections::).
+
+ * The `noclobber' option is available to avoid overwriting existing
+ files with output redirection (*note The Set Builtin::). The `>|'
+ redirection operator may be used to override `noclobber'.
+
+ * The Bash `cd' and `pwd' builtins (*note Bourne Shell Builtins::)
+ each take `-L' and `-P' options to switch between logical and
+ physical modes.
+
+ * Bash allows a function to override a builtin with the same name,
+ and provides access to that builtin's functionality within the
+ function via the `builtin' and `command' builtins (*note Bash
+ Builtins::).
+
+ * The `command' builtin allows selective disabling of functions when
+ command lookup is performed (*note Bash Builtins::).
+
+ * Individual builtins may be enabled or disabled using the `enable'
+ builtin (*note Bash Builtins::).
+
+ * The Bash `exec' builtin takes additional options that allow users
+ to control the contents of the environment passed to the executed
+ command, and what the zeroth argument to the command is to be
+ (*note Bourne Shell Builtins::).
+
+ * Shell functions may be exported to children via the environment
+ using `export -f' (*note Shell Functions::).
+
+ * The Bash `export', `readonly', and `declare' builtins can take a
+ `-f' option to act on shell functions, a `-p' option to display
+ variables with various attributes set in a format that can be used
+ as shell input, a `-n' option to remove various variable
+ attributes, and `name=value' arguments to set variable attributes
+ and values simultaneously.
+
+ * The Bash `hash' builtin allows a name to be associated with an
+ arbitrary filename, even when that filename cannot be found by
+ searching the `$PATH', using `hash -p' (*note Bourne Shell
+ Builtins::).
+
+ * Bash includes a `help' builtin for quick reference to shell
+ facilities (*note Bash Builtins::).
+
+ * The `printf' builtin is available to display formatted output
+ (*note Bash Builtins::).
+
+ * The Bash `read' builtin (*note Bash Builtins::) will read a line
+ ending in `\' with the `-r' option, and will use the `REPLY'
+ variable as a default if no non-option arguments are supplied.
+ The Bash `read' builtin also accepts a prompt string with the `-p'
+ option and will use Readline to obtain the line when given the
+ `-e' option. The `read' builtin also has additional options to
+ control input: the `-s' option will turn off echoing of input
+ characters as they are read, the `-t' option will allow `read' to
+ time out if input does not arrive within a specified number of
+ seconds, the `-n' option will allow reading only a specified
+ number of characters rather than a full line, and the `-d' option
+ will read until a particular character rather than newline.
+
+ * The `return' builtin may be used to abort execution of scripts
+ executed with the `.' or `source' builtins (*note Bourne Shell
+ Builtins::).
+
+ * Bash includes the `shopt' builtin, for finer control of shell
+ optional capabilities (*note The Shopt Builtin::), and allows
+ these options to be set and unset at shell invocation (*note
+ Invoking Bash::).
+
+ * Bash has much more optional behavior controllable with the `set'
+ builtin (*note The Set Builtin::).
+
+ * The `-x' (`xtrace') option displays commands other than simple
+ commands when performing an execution trace (*note The Set
+ Builtin::).
+
+ * The `test' builtin (*note Bourne Shell Builtins::) is slightly
+ different, as it implements the POSIX algorithm, which specifies
+ the behavior based on the number of arguments.
+
+ * Bash includes the `caller' builtin, which displays the context of
+ any active subroutine call (a shell function or a script executed
+ with the `.' or `source' builtins). This supports the bash
+ debugger.
+
+ * The `trap' builtin (*note Bourne Shell Builtins::) allows a
+ `DEBUG' pseudo-signal specification, similar to `EXIT'. Commands
+ specified with a `DEBUG' trap are executed before every simple
+ command, `for' command, `case' command, `select' command, every
+ arithmetic `for' command, and before the first command executes in
+ a shell function. The `DEBUG' trap is not inherited by shell
+ functions unless the function has been given the `trace' attribute
+ or the `functrace' option has been enabled using the `shopt'
+ builtin. The `extdebug' shell option has additional effects on the
+ `DEBUG' trap.
+
+ The `trap' builtin (*note Bourne Shell Builtins::) allows an `ERR'
+ pseudo-signal specification, similar to `EXIT' and `DEBUG'.
+ Commands specified with an `ERR' trap are executed after a simple
+ command fails, with a few exceptions. The `ERR' trap is not
+ inherited by shell functions unless the `-o errtrace' option to
+ the `set' builtin is enabled.
+
+ The `trap' builtin (*note Bourne Shell Builtins::) allows a
+ `RETURN' pseudo-signal specification, similar to `EXIT' and
+ `DEBUG'. Commands specified with an `RETURN' trap are executed
+ before execution resumes after a shell function or a shell script
+ executed with `.' or `source' returns. The `RETURN' trap is not
+ inherited by shell functions unless the function has been given
+ the `trace' attribute or the `functrace' option has been enabled
+ using the `shopt' builtin.
+
+ * The Bash `type' builtin is more extensive and gives more
+ information about the names it finds (*note Bash Builtins::).
+
+ * The Bash `umask' builtin permits a `-p' option to cause the output
+ to be displayed in the form of a `umask' command that may be
+ reused as input (*note Bourne Shell Builtins::).
+
+ * Bash implements a `csh'-like directory stack, and provides the
+ `pushd', `popd', and `dirs' builtins to manipulate it (*note The
+ Directory Stack::). Bash also makes the directory stack visible
+ as the value of the `DIRSTACK' shell variable.
+
+ * Bash interprets special backslash-escaped characters in the prompt
+ strings when interactive (*note Printing a Prompt::).
+
+ * The Bash restricted mode is more useful (*note The Restricted
+ Shell::); the SVR4.2 shell restricted mode is too limited.
+
+ * The `disown' builtin can remove a job from the internal shell job
+ table (*note Job Control Builtins::) or suppress the sending of
+ `SIGHUP' to a job when the shell exits as the result of a `SIGHUP'.
+
+ * Bash includes a number of features to support a separate debugger
+ for shell scripts.
+
+ * The SVR4.2 shell has two privilege-related builtins (`mldmode' and
+ `priv') not present in Bash.
+
+ * Bash does not have the `stop' or `newgrp' builtins.
+
+ * Bash does not use the `SHACCT' variable or perform shell
+ accounting.
+
+ * The SVR4.2 `sh' uses a `TIMEOUT' variable like Bash uses `TMOUT'.
+
+
+More features unique to Bash may be found in *note Bash Features::.
+
+B.1 Implementation Differences From The SVR4.2 Shell
+====================================================
+
+Since Bash is a completely new implementation, it does not suffer from
+many of the limitations of the SVR4.2 shell. For instance:
+
+ * Bash does not fork a subshell when redirecting into or out of a
+ shell control structure such as an `if' or `while' statement.
+
+ * Bash does not allow unbalanced quotes. The SVR4.2 shell will
+ silently insert a needed closing quote at `EOF' under certain
+ circumstances. This can be the cause of some hard-to-find errors.
+
+ * The SVR4.2 shell uses a baroque memory management scheme based on
+ trapping `SIGSEGV'. If the shell is started from a process with
+ `SIGSEGV' blocked (e.g., by using the `system()' C library
+ function call), it misbehaves badly.
+
+ * In a questionable attempt at security, the SVR4.2 shell, when
+ invoked without the `-p' option, will alter its real and effective
+ UID and GID if they are less than some magic threshold value,
+ commonly 100. This can lead to unexpected results.
+
+ * The SVR4.2 shell does not allow users to trap `SIGSEGV',
+ `SIGALRM', or `SIGCHLD'.
+
+ * The SVR4.2 shell does not allow the `IFS', `MAILCHECK', `PATH',
+ `PS1', or `PS2' variables to be unset.
+
+ * The SVR4.2 shell treats `^' as the undocumented equivalent of `|'.
+
+ * Bash allows multiple option arguments when it is invoked (`-x -v');
+ the SVR4.2 shell allows only one option argument (`-xv'). In
+ fact, some versions of the shell dump core if the second argument
+ begins with a `-'.
+
+ * The SVR4.2 shell exits a script if any builtin fails; Bash exits a
+ script only if one of the POSIX special builtins fails, and only
+ for certain failures, as enumerated in the POSIX standard.
+
+ * The SVR4.2 shell behaves differently when invoked as `jsh' (it
+ turns on job control).
+
+\1f
+File: bashref.info, Node: GNU Free Documentation License, Next: Indexes, Prev: Major Differences From The Bourne Shell, Up: Top
+
+Appendix C GNU Free Documentation License
+*****************************************
+
+ Version 1.2, November 2002
+
+ Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
+ 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+ 0. PREAMBLE
+
+ The purpose of this License is to make a manual, textbook, or other
+ functional and useful document "free" in the sense of freedom: to
+ assure everyone the effective freedom to copy and redistribute it,
+ with or without modifying it, either commercially or
+ noncommercially. Secondarily, this License preserves for the
+ author and publisher a way to get credit for their work, while not
+ being considered responsible for modifications made by others.
+
+ This License is a kind of "copyleft", which means that derivative
+ works of the document must themselves be free in the same sense.
+ It complements the GNU General Public License, which is a copyleft
+ license designed for free software.
+
+ We have designed this License in order to use it for manuals for
+ free software, because free software needs free documentation: a
+ free program should come with manuals providing the same freedoms
+ that the software does. But this License is not limited to
+ software manuals; it can be used for any textual work, regardless
+ of subject matter or whether it is published as a printed book.
+ We recommend this License principally for works whose purpose is
+ instruction or reference.
+
+ 1. APPLICABILITY AND DEFINITIONS
+
+ This License applies to any manual or other work, in any medium,
+ that contains a notice placed by the copyright holder saying it
+ can be distributed under the terms of this License. Such a notice
+ grants a world-wide, royalty-free license, unlimited in duration,
+ to use that work under the conditions stated herein. The
+ "Document", below, refers to any such manual or work. Any member
+ of the public is a licensee, and is addressed as "you". You
+ accept the license if you copy, modify or distribute the work in a
+ way requiring permission under copyright law.
+
+ A "Modified Version" of the Document means any work containing the
+ Document or a portion of it, either copied verbatim, or with
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+
+ A "Secondary Section" is a named appendix or a front-matter section
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+
+ The "Invariant Sections" are certain Secondary Sections whose
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+ following text that translates XYZ in another language. (Here XYZ
+ stands for a specific section name mentioned below, such as
+ "Acknowledgements", "Dedications", "Endorsements", or "History".)
+ To "Preserve the Title" of such a section when you modify the
+ Document means that it remains a section "Entitled XYZ" according
+ to this definition.
+
+ The Document may include Warranty Disclaimers next to the notice
+ which states that this License applies to the Document. These
+ Warranty Disclaimers are considered to be included by reference in
+ this License, but only as regards disclaiming warranties: any other
+ implication that these Warranty Disclaimers may have is void and
+ has no effect on the meaning of this License.
+
+ 2. VERBATIM COPYING
+
+ You may copy and distribute the Document in any medium, either
+ commercially or noncommercially, provided that this License, the
+ copyright notices, and the license notice saying this License
+ applies to the Document are reproduced in all copies, and that you
+ add no other conditions whatsoever to those of this License. You
+ may not use technical measures to obstruct or control the reading
+ or further copying of the copies you make or distribute. However,
+ you may accept compensation in exchange for copies. If you
+ distribute a large enough number of copies you must also follow
+ the conditions in section 3.
+
+ You may also lend copies, under the same conditions stated above,
+ and you may publicly display copies.
+
+ 3. COPYING IN QUANTITY
+
+ If you publish printed copies (or copies in media that commonly
+ have printed covers) of the Document, numbering more than 100, and
+ the Document's license notice requires Cover Texts, you must
+ enclose the copies in covers that carry, clearly and legibly, all
+ these Cover Texts: Front-Cover Texts on the front cover, and
+ Back-Cover Texts on the back cover. Both covers must also clearly
+ and legibly identify you as the publisher of these copies. The
+ front cover must present the full title with all words of the
+ title equally prominent and visible. You may add other material
+ on the covers in addition. Copying with changes limited to the
+ covers, as long as they preserve the title of the Document and
+ satisfy these conditions, can be treated as verbatim copying in
+ other respects.
+
+ If the required texts for either cover are too voluminous to fit
+ legibly, you should put the first ones listed (as many as fit
+ reasonably) on the actual cover, and continue the rest onto
+ adjacent pages.
+
+ If you publish or distribute Opaque copies of the Document
+ numbering more than 100, you must either include a
+ machine-readable Transparent copy along with each Opaque copy, or
+ state in or with each Opaque copy a computer-network location from
+ which the general network-using public has access to download
+ using public-standard network protocols a complete Transparent
+ copy of the Document, free of added material. If you use the
+ latter option, you must take reasonably prudent steps, when you
+ begin distribution of Opaque copies in quantity, to ensure that
+ this Transparent copy will remain thus accessible at the stated
+ location until at least one year after the last time you
+ distribute an Opaque copy (directly or through your agents or
+ retailers) of that edition to the public.
+
+ It is requested, but not required, that you contact the authors of
+ the Document well before redistributing any large number of
+ copies, to give them a chance to provide you with an updated
+ version of the Document.
+
+ 4. MODIFICATIONS
+
+ You may copy and distribute a Modified Version of the Document
+ under the conditions of sections 2 and 3 above, provided that you
+ release the Modified Version under precisely this License, with
+ the Modified Version filling the role of the Document, thus
+ licensing distribution and modification of the Modified Version to
+ whoever possesses a copy of it. In addition, you must do these
+ things in the Modified Version:
+
+ A. Use in the Title Page (and on the covers, if any) a title
+ distinct from that of the Document, and from those of
+ previous versions (which should, if there were any, be listed
+ in the History section of the Document). You may use the
+ same title as a previous version if the original publisher of
+ that version gives permission.
+
+ B. List on the Title Page, as authors, one or more persons or
+ entities responsible for authorship of the modifications in
+ the Modified Version, together with at least five of the
+ principal authors of the Document (all of its principal
+ authors, if it has fewer than five), unless they release you
+ from this requirement.
+
+ C. State on the Title page the name of the publisher of the
+ Modified Version, as the publisher.
+
+ D. Preserve all the copyright notices of the Document.
+
+ E. Add an appropriate copyright notice for your modifications
+ adjacent to the other copyright notices.
+
+ F. Include, immediately after the copyright notices, a license
+ notice giving the public permission to use the Modified
+ Version under the terms of this License, in the form shown in
+ the Addendum below.
+
+ G. Preserve in that license notice the full lists of Invariant
+ Sections and required Cover Texts given in the Document's
+ license notice.
+
+ H. Include an unaltered copy of this License.
+
+ I. Preserve the section Entitled "History", Preserve its Title,
+ and add to it an item stating at least the title, year, new
+ authors, and publisher of the Modified Version as given on
+ the Title Page. If there is no section Entitled "History" in
+ the Document, create one stating the title, year, authors,
+ and publisher of the Document as given on its Title Page,
+ then add an item describing the Modified Version as stated in
+ the previous sentence.
+
+ J. Preserve the network location, if any, given in the Document
+ for public access to a Transparent copy of the Document, and
+ likewise the network locations given in the Document for
+ previous versions it was based on. These may be placed in
+ the "History" section. You may omit a network location for a
+ work that was published at least four years before the
+ Document itself, or if the original publisher of the version
+ it refers to gives permission.
+
+ K. For any section Entitled "Acknowledgements" or "Dedications",
+ Preserve the Title of the section, and preserve in the
+ section all the substance and tone of each of the contributor
+ acknowledgements and/or dedications given therein.
+
+ L. Preserve all the Invariant Sections of the Document,
+ unaltered in their text and in their titles. Section numbers
+ or the equivalent are not considered part of the section
+ titles.
+
+ M. Delete any section Entitled "Endorsements". Such a section
+ may not be included in the Modified Version.
+
+ N. Do not retitle any existing section to be Entitled
+ "Endorsements" or to conflict in title with any Invariant
+ Section.
+
+ O. Preserve any Warranty Disclaimers.
+
+ If the Modified Version includes new front-matter sections or
+ appendices that qualify as Secondary Sections and contain no
+ material copied from the Document, you may at your option
+ designate some or all of these sections as invariant. To do this,
+ add their titles to the list of Invariant Sections in the Modified
+ Version's license notice. These titles must be distinct from any
+ other section titles.
+
+ You may add a section Entitled "Endorsements", provided it contains
+ nothing but endorsements of your Modified Version by various
+ parties--for example, statements of peer review or that the text
+ has been approved by an organization as the authoritative
+ definition of a standard.
+
+ You may add a passage of up to five words as a Front-Cover Text,
+ and a passage of up to 25 words as a Back-Cover Text, to the end
+ of the list of Cover Texts in the Modified Version. Only one
+ passage of Front-Cover Text and one of Back-Cover Text may be
+ added by (or through arrangements made by) any one entity. If the
+ Document already includes a cover text for the same cover,
+ previously added by you or by arrangement made by the same entity
+ you are acting on behalf of, you may not add another; but you may
+ replace the old one, on explicit permission from the previous
+ publisher that added the old one.
+
+ The author(s) and publisher(s) of the Document do not by this
+ License give permission to use their names for publicity for or to
+ assert or imply endorsement of any Modified Version.
+
+ 5. COMBINING DOCUMENTS
+
+ You may combine the Document with other documents released under
+ this License, under the terms defined in section 4 above for
+ modified versions, provided that you include in the combination
+ all of the Invariant Sections of all of the original documents,
+ unmodified, and list them all as Invariant Sections of your
+ combined work in its license notice, and that you preserve all
+ their Warranty Disclaimers.
+
+ The combined work need only contain one copy of this License, and
+ multiple identical Invariant Sections may be replaced with a single
+ copy. If there are multiple Invariant Sections with the same name
+ but different contents, make the title of each such section unique
+ by adding at the end of it, in parentheses, the name of the
+ original author or publisher of that section if known, or else a
+ unique number. Make the same adjustment to the section titles in
+ the list of Invariant Sections in the license notice of the
+ combined work.
+
+ In the combination, you must combine any sections Entitled
+ "History" in the various original documents, forming one section
+ Entitled "History"; likewise combine any sections Entitled
+ "Acknowledgements", and any sections Entitled "Dedications". You
+ must delete all sections Entitled "Endorsements."
+
+ 6. COLLECTIONS OF DOCUMENTS
+
+ You may make a collection consisting of the Document and other
+ documents released under this License, and replace the individual
+ copies of this License in the various documents with a single copy
+ that is included in the collection, provided that you follow the
+ rules of this License for verbatim copying of each of the
+ documents in all other respects.
+
+ You may extract a single document from such a collection, and
+ distribute it individually under this License, provided you insert
+ a copy of this License into the extracted document, and follow
+ this License in all other respects regarding verbatim copying of
+ that document.
+
+ 7. AGGREGATION WITH INDEPENDENT WORKS
+
+ A compilation of the Document or its derivatives with other
+ separate and independent documents or works, in or on a volume of
+ a storage or distribution medium, is called an "aggregate" if the
+ copyright resulting from the compilation is not used to limit the
+ legal rights of the compilation's users beyond what the individual
+ works permit. When the Document is included in an aggregate, this
+ License does not apply to the other works in the aggregate which
+ are not themselves derivative works of the Document.
+
+ If the Cover Text requirement of section 3 is applicable to these
+ copies of the Document, then if the Document is less than one half
+ of the entire aggregate, the Document's Cover Texts may be placed
+ on covers that bracket the Document within the aggregate, or the
+ electronic equivalent of covers if the Document is in electronic
+ form. Otherwise they must appear on printed covers that bracket
+ the whole aggregate.
+
+ 8. TRANSLATION
+
+ Translation is considered a kind of modification, so you may
+ distribute translations of the Document under the terms of section
+ 4. Replacing Invariant Sections with translations requires special
+ permission from their copyright holders, but you may include
+ translations of some or all Invariant Sections in addition to the
+ original versions of these Invariant Sections. You may include a
+ translation of this License, and all the license notices in the
+ Document, and any Warranty Disclaimers, provided that you also
+ include the original English version of this License and the
+ original versions of those notices and disclaimers. In case of a
+ disagreement between the translation and the original version of
+ this License or a notice or disclaimer, the original version will
+ prevail.
+
+ If a section in the Document is Entitled "Acknowledgements",
+ "Dedications", or "History", the requirement (section 4) to
+ Preserve its Title (section 1) will typically require changing the
+ actual title.
+
+ 9. TERMINATION
+
+ You may not copy, modify, sublicense, or distribute the Document
+ except as expressly provided for under this License. Any other
+ attempt to copy, modify, sublicense or distribute the Document is
+ void, and will automatically terminate your rights under this
+ License. However, parties who have received copies, or rights,
+ from you under this License will not have their licenses
+ terminated so long as such parties remain in full compliance.
+
+ 10. FUTURE REVISIONS OF THIS LICENSE
+
+ The Free Software Foundation may publish new, revised versions of
+ the GNU Free Documentation License from time to time. Such new
+ versions will be similar in spirit to the present version, but may
+ differ in detail to address new problems or concerns. See
+ `http://www.gnu.org/copyleft/'.
+
+ Each version of the License is given a distinguishing version
+ number. If the Document specifies that a particular numbered
+ version of this License "or any later version" applies to it, you
+ have the option of following the terms and conditions either of
+ that specified version or of any later version that has been
+ published (not as a draft) by the Free Software Foundation. If
+ the Document does not specify a version number of this License,
+ you may choose any version ever published (not as a draft) by the
+ Free Software Foundation.
+
+ADDENDUM: How to use this License for your documents
+====================================================
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and license
+notices just after the title page:
+
+ Copyright (C) YEAR YOUR NAME.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.2
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+
+ If you have Invariant Sections, Front-Cover Texts and Back-Cover
+Texts, replace the "with...Texts." line with this:
+
+ with the Invariant Sections being LIST THEIR TITLES, with
+ the Front-Cover Texts being LIST, and with the Back-Cover Texts
+ being LIST.
+
+ If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+ If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License, to
+permit their use in free software.
+
+\1f
+File: bashref.info, Node: Indexes, Prev: GNU Free Documentation License, Up: Top
+
+Appendix D Indexes
+******************
+
+* Menu:
+
+* Builtin Index:: Index of Bash builtin commands.
+* Reserved Word Index:: Index of Bash reserved words.
+* Variable Index:: Quick reference helps you find the
+ variable you want.
+* Function Index:: Index of bindable Readline functions.
+* Concept Index:: General index for concepts described in
+ this manual.
\1f
-File: bashref.info, Node: Builtin Index, Next: Reserved Word Index, Prev: Reporting Bugs, Up: Top
+File: bashref.info, Node: Builtin Index, Next: Reserved Word Index, Up: Indexes
-Index of Shell Builtin Commands
-*******************************
+D.1 Index of Shell Builtin Commands
+===================================
+\0\b[index\0\b]
* Menu:
-* .: Bourne Shell Builtins.
-* :: Bourne Shell Builtins.
-* [: Bourne Shell Builtins.
-* alias: Alias Builtins.
-* bg: Job Control Builtins.
-* bind: Bash Builtins.
-* break: Bourne Shell Builtins.
-* builtin: Bash Builtins.
-* cd: Bourne Shell Builtins.
-* command: Bash Builtins.
-* continue: Bourne Shell Builtins.
-* declare: Bash Builtins.
-* dirs: C Shell Builtins.
-* disown: Job Control Builtins.
-* echo: Bash Builtins.
-* enable: Bash Builtins.
-* eval: Bourne Shell Builtins.
-* exec: Bourne Shell Builtins.
-* exit: Bourne Shell Builtins.
-* export: Bourne Shell Builtins.
-* fc: Korn Shell Builtins.
-* fg: Job Control Builtins.
-* getopts: Bourne Shell Builtins.
-* hash: Bourne Shell Builtins.
-* help: Bash Builtins.
-* history: C Shell Builtins.
-* jobs: Job Control Builtins.
-* kill: Job Control Builtins.
-* let <1>: Arithmetic Builtins.
-* let: Korn Shell Builtins.
-* local: Bash Builtins.
-* logout <1>: Bash Builtins.
-* logout: C Shell Builtins.
-* popd: C Shell Builtins.
-* pushd: C Shell Builtins.
-* pwd: Bourne Shell Builtins.
-* read: Bash Builtins.
-* readonly: Bourne Shell Builtins.
-* return: Bourne Shell Builtins.
-* set: The Set Builtin.
-* shift: Bourne Shell Builtins.
-* shopt: Bash Builtins.
-* source: C Shell Builtins.
-* suspend: Job Control Builtins.
-* test: Bourne Shell Builtins.
-* times: Bourne Shell Builtins.
-* trap: Bourne Shell Builtins.
-* type: Bash Builtins.
-* typeset: Korn Shell Builtins.
-* ulimit: Bash Builtins.
-* umask: Bourne Shell Builtins.
-* unalias: Alias Builtins.
-* unset: Bourne Shell Builtins.
-* wait: Job Control Builtins.
-
-\1f
-File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Top
-
-Shell Reserved Words
-********************
+* .: Bourne Shell Builtins.
+ (line 16)
+* :: Bourne Shell Builtins.
+ (line 11)
+* [: Bourne Shell Builtins.
+ (line 213)
+* alias: Bash Builtins. (line 11)
+* bg: Job Control Builtins.
+ (line 7)
+* bind: Bash Builtins. (line 21)
+* break: Bourne Shell Builtins.
+ (line 29)
+* builtin: Bash Builtins. (line 98)
+* caller: Bash Builtins. (line 106)
+* cd: Bourne Shell Builtins.
+ (line 36)
+* command: Bash Builtins. (line 123)
+* compgen: Programmable Completion Builtins.
+ (line 10)
+* complete: Programmable Completion Builtins.
+ (line 28)
+* compopt: Programmable Completion Builtins.
+ (line 213)
+* continue: Bourne Shell Builtins.
+ (line 55)
+* declare: Bash Builtins. (line 142)
+* dirs: Directory Stack Builtins.
+ (line 7)
+* disown: Job Control Builtins.
+ (line 83)
+* echo: Bash Builtins. (line 221)
+* enable: Bash Builtins. (line 273)
+* eval: Bourne Shell Builtins.
+ (line 63)
+* exec: Bourne Shell Builtins.
+ (line 70)
+* exit: Bourne Shell Builtins.
+ (line 82)
+* export: Bourne Shell Builtins.
+ (line 88)
+* fc: Bash History Builtins.
+ (line 10)
+* fg: Job Control Builtins.
+ (line 16)
+* getopts: Bourne Shell Builtins.
+ (line 103)
+* hash: Bourne Shell Builtins.
+ (line 145)
+* help: Bash Builtins. (line 301)
+* history: Bash History Builtins.
+ (line 39)
+* jobs: Job Control Builtins.
+ (line 25)
+* kill: Job Control Builtins.
+ (line 57)
+* let: Bash Builtins. (line 321)
+* local: Bash Builtins. (line 328)
+* logout: Bash Builtins. (line 338)
+* mapfile: Bash Builtins. (line 342)
+* popd: Directory Stack Builtins.
+ (line 37)
+* printf: Bash Builtins. (line 383)
+* pushd: Directory Stack Builtins.
+ (line 58)
+* pwd: Bourne Shell Builtins.
+ (line 163)
+* read: Bash Builtins. (line 408)
+* readonly: Bourne Shell Builtins.
+ (line 172)
+* return: Bourne Shell Builtins.
+ (line 188)
+* set: The Set Builtin. (line 11)
+* shift: Bourne Shell Builtins.
+ (line 201)
+* shopt: The Shopt Builtin. (line 9)
+* source: Bash Builtins. (line 480)
+* suspend: Job Control Builtins.
+ (line 94)
+* test: Bourne Shell Builtins.
+ (line 213)
+* times: Bourne Shell Builtins.
+ (line 281)
+* trap: Bourne Shell Builtins.
+ (line 286)
+* type: Bash Builtins. (line 484)
+* typeset: Bash Builtins. (line 515)
+* ulimit: Bash Builtins. (line 521)
+* umask: Bourne Shell Builtins.
+ (line 327)
+* unalias: Bash Builtins. (line 607)
+* unset: Bourne Shell Builtins.
+ (line 344)
+* wait: Job Control Builtins.
+ (line 73)
+\1f
+File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Indexes
+
+D.2 Index of Shell Reserved Words
+=================================
+
+\0\b[index\0\b]
* Menu:
-* !: Pipelines.
-* {: Command Grouping.
-* }: Command Grouping.
-* case: Conditional Constructs.
-* do: Looping Constructs.
-* done: Looping Constructs.
-* elif: Conditional Constructs.
-* else: Conditional Constructs.
-* esac: Conditional Constructs.
-* fi: Conditional Constructs.
-* for: Looping Constructs.
-* function: Shell Functions.
-* if: Conditional Constructs.
-* in: Conditional Constructs.
-* select: Korn Shell Constructs.
-* then: Conditional Constructs.
-* time: Pipelines.
-* until: Looping Constructs.
-* while: Looping Constructs.
-
-\1f
-File: bashref.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Top
-
-Parameter and Variable Index
-****************************
+* !: Pipelines. (line 9)
+* [[: Conditional Constructs.
+ (line 117)
+* ]]: Conditional Constructs.
+ (line 117)
+* case: Conditional Constructs.
+ (line 28)
+* do: Looping Constructs. (line 12)
+* done: Looping Constructs. (line 12)
+* elif: Conditional Constructs.
+ (line 7)
+* else: Conditional Constructs.
+ (line 7)
+* esac: Conditional Constructs.
+ (line 28)
+* fi: Conditional Constructs.
+ (line 7)
+* for: Looping Constructs. (line 29)
+* function: Shell Functions. (line 13)
+* if: Conditional Constructs.
+ (line 7)
+* in: Conditional Constructs.
+ (line 28)
+* select: Conditional Constructs.
+ (line 76)
+* then: Conditional Constructs.
+ (line 7)
+* time: Pipelines. (line 9)
+* until: Looping Constructs. (line 12)
+* while: Looping Constructs. (line 20)
+* {: Command Grouping. (line 21)
+* }: Command Grouping. (line 21)
+
+\1f
+File: bashref.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Indexes
+
+D.3 Parameter and Variable Index
+================================
+\0\b[index\0\b]
* Menu:
-* !: Special Parameters.
-* #: Special Parameters.
-* $: Special Parameters.
-* *: Special Parameters.
-* -: Special Parameters.
-* 0: Special Parameters.
-* ?: Special Parameters.
-* @: Special Parameters.
-* _: Special Parameters.
-* auto_resume: Job Control Variables.
-* BASH: Bash Variables.
-* BASH_ENV: Bash Variables.
-* BASH_VERSINFO: Bash Variables.
-* BASH_VERSION: Bash Variables.
-* bell-style: Readline Init File Syntax.
-* CDPATH: Bourne Shell Variables.
-* comment-begin: Readline Init File Syntax.
-* completion-query-items: Readline Init File Syntax.
-* convert-meta: Readline Init File Syntax.
-* DIRSTACK: Bash Variables.
-* disable-completion: Readline Init File Syntax.
-* editing-mode: Readline Init File Syntax.
-* enable-keypad: Readline Init File Syntax.
-* EUID: Bash Variables.
-* expand-tilde: Readline Init File Syntax.
-* FCEDIT: Korn Shell Variables.
-* FIGNORE: Bash Variables.
-* GLOBIGNORE: Bash Variables.
-* GROUPS: Bash Variables.
-* histchars: Bash Variables.
-* HISTCMD: Bash Variables.
-* HISTCONTROL: Bash Variables.
-* HISTFILE: Bash Variables.
-* HISTFILESIZE: Bash Variables.
-* HISTIGNORE: Bash Variables.
-* HISTSIZE: Bash Variables.
-* HOME: Bourne Shell Variables.
-* horizontal-scroll-mode: Readline Init File Syntax.
-* HOSTFILE: Bash Variables.
-* HOSTNAME: Bash Variables.
-* HOSTTYPE: Bash Variables.
-* IFS: Bourne Shell Variables.
-* IGNOREEOF <1>: Bash Variables.
-* IGNOREEOF: C Shell Variables.
-* input-meta: Readline Init File Syntax.
-* INPUTRC: Bash Variables.
-* keymap: Readline Init File Syntax.
-* LANG: Bash Variables.
-* LC_ALL: Bash Variables.
-* LC_COLLATE: Bash Variables.
-* LC_MESSAGES: Bash Variables.
-* LINENO: Korn Shell Variables.
-* MACHTYPE: Bash Variables.
-* MAIL: Bourne Shell Variables.
-* MAILCHECK: Bash Variables.
-* MAILPATH: Bourne Shell Variables.
-* mark-modified-lines: Readline Init File Syntax.
-* meta-flag: Readline Init File Syntax.
-* OLDPWD: Korn Shell Variables.
-* OPTARG: Bourne Shell Variables.
-* OPTERR: Bash Variables.
-* OPTIND: Bourne Shell Variables.
-* OSTYPE: Bash Variables.
-* output-meta: Readline Init File Syntax.
-* PATH: Bourne Shell Variables.
-* PIPESTATUS: Bash Variables.
-* PPID: Bash Variables.
-* PROMPT_COMMAND: Bash Variables.
-* PS1: Bourne Shell Variables.
-* PS2: Bourne Shell Variables.
-* PS3: Korn Shell Variables.
-* PS4: Korn Shell Variables.
-* PWD: Korn Shell Variables.
-* RANDOM: Korn Shell Variables.
-* REPLY: Korn Shell Variables.
-* SECONDS: Korn Shell Variables.
-* SHELLOPTS: Bash Variables.
-* SHLVL: Bash Variables.
-* show-all-if-ambiguous: Readline Init File Syntax.
-* TIMEFORMAT: Bash Variables.
-* TMOUT: Korn Shell Variables.
-* UID: Bash Variables.
-* visible-stats: Readline Init File Syntax.
-
-\1f
-File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Top
-
-Function Index
-**************
+* !: Special Parameters. (line 46)
+* #: Special Parameters. (line 30)
+* $: Special Parameters. (line 42)
+* *: Special Parameters. (line 9)
+* -: Special Parameters. (line 37)
+* 0: Special Parameters. (line 50)
+* ?: Special Parameters. (line 33)
+* @: Special Parameters. (line 19)
+* _: Special Parameters. (line 59)
+* auto_resume: Job Control Variables.
+ (line 6)
+* BASH: Bash Variables. (line 13)
+* BASH_ALIASES: Bash Variables. (line 21)
+* BASH_ARGC: Bash Variables. (line 28)
+* BASH_ARGV: Bash Variables. (line 38)
+* BASH_CMDS: Bash Variables. (line 48)
+* BASH_COMMAND: Bash Variables. (line 55)
+* BASH_ENV: Bash Variables. (line 60)
+* BASH_EXECUTION_STRING: Bash Variables. (line 66)
+* BASH_LINENO: Bash Variables. (line 69)
+* BASH_REMATCH: Bash Variables. (line 78)
+* BASH_SOURCE: Bash Variables. (line 86)
+* BASH_SUBSHELL: Bash Variables. (line 90)
+* BASH_VERSINFO: Bash Variables. (line 94)
+* BASH_VERSION: Bash Variables. (line 118)
+* BASHPID: Bash Variables. (line 16)
+* bell-style: Readline Init File Syntax.
+ (line 38)
+* bind-tty-special-chars: Readline Init File Syntax.
+ (line 45)
+* CDPATH: Bourne Shell Variables.
+ (line 9)
+* COLUMNS: Bash Variables. (line 121)
+* comment-begin: Readline Init File Syntax.
+ (line 50)
+* COMP_CWORD: Bash Variables. (line 126)
+* COMP_KEY: Bash Variables. (line 155)
+* COMP_LINE: Bash Variables. (line 132)
+* COMP_POINT: Bash Variables. (line 137)
+* COMP_TYPE: Bash Variables. (line 145)
+* COMP_WORDBREAKS: Bash Variables. (line 159)
+* COMP_WORDS: Bash Variables. (line 165)
+* completion-prefix-display-length: Readline Init File Syntax.
+ (line 60)
+* completion-query-items: Readline Init File Syntax.
+ (line 67)
+* COMPREPLY: Bash Variables. (line 172)
+* convert-meta: Readline Init File Syntax.
+ (line 77)
+* DIRSTACK: Bash Variables. (line 177)
+* disable-completion: Readline Init File Syntax.
+ (line 83)
+* editing-mode: Readline Init File Syntax.
+ (line 88)
+* EMACS: Bash Variables. (line 187)
+* enable-keypad: Readline Init File Syntax.
+ (line 94)
+* EUID: Bash Variables. (line 192)
+* expand-tilde: Readline Init File Syntax.
+ (line 99)
+* FCEDIT: Bash Variables. (line 196)
+* FIGNORE: Bash Variables. (line 200)
+* FUNCNAME: Bash Variables. (line 206)
+* GLOBIGNORE: Bash Variables. (line 215)
+* GROUPS: Bash Variables. (line 221)
+* histchars: Bash Variables. (line 227)
+* HISTCMD: Bash Variables. (line 242)
+* HISTCONTROL: Bash Variables. (line 247)
+* HISTFILE: Bash Variables. (line 263)
+* HISTFILESIZE: Bash Variables. (line 267)
+* HISTIGNORE: Bash Variables. (line 275)
+* history-preserve-point: Readline Init File Syntax.
+ (line 103)
+* history-size: Readline Init File Syntax.
+ (line 109)
+* HISTSIZE: Bash Variables. (line 294)
+* HISTTIMEFORMAT: Bash Variables. (line 298)
+* HOME: Bourne Shell Variables.
+ (line 13)
+* horizontal-scroll-mode: Readline Init File Syntax.
+ (line 114)
+* HOSTFILE: Bash Variables. (line 307)
+* HOSTNAME: Bash Variables. (line 318)
+* HOSTTYPE: Bash Variables. (line 321)
+* IFS: Bourne Shell Variables.
+ (line 18)
+* IGNOREEOF: Bash Variables. (line 324)
+* input-meta: Readline Init File Syntax.
+ (line 121)
+* INPUTRC: Bash Variables. (line 334)
+* isearch-terminators: Readline Init File Syntax.
+ (line 128)
+* keymap: Readline Init File Syntax.
+ (line 135)
+* LANG: Bash Variables. (line 338)
+* LC_ALL: Bash Variables. (line 342)
+* LC_COLLATE: Bash Variables. (line 346)
+* LC_CTYPE: Bash Variables. (line 353)
+* LC_MESSAGES <1>: Locale Translation. (line 11)
+* LC_MESSAGES: Bash Variables. (line 358)
+* LC_NUMERIC: Bash Variables. (line 362)
+* LINENO: Bash Variables. (line 366)
+* LINES: Bash Variables. (line 370)
+* MACHTYPE: Bash Variables. (line 375)
+* MAIL: Bourne Shell Variables.
+ (line 22)
+* MAILCHECK: Bash Variables. (line 379)
+* MAILPATH: Bourne Shell Variables.
+ (line 27)
+* mark-modified-lines: Readline Init File Syntax.
+ (line 148)
+* mark-symlinked-directories: Readline Init File Syntax.
+ (line 153)
+* match-hidden-files: Readline Init File Syntax.
+ (line 158)
+* meta-flag: Readline Init File Syntax.
+ (line 121)
+* OLDPWD: Bash Variables. (line 387)
+* OPTARG: Bourne Shell Variables.
+ (line 34)
+* OPTERR: Bash Variables. (line 390)
+* OPTIND: Bourne Shell Variables.
+ (line 38)
+* OSTYPE: Bash Variables. (line 394)
+* output-meta: Readline Init File Syntax.
+ (line 165)
+* page-completions: Readline Init File Syntax.
+ (line 170)
+* PATH: Bourne Shell Variables.
+ (line 42)
+* PIPESTATUS: Bash Variables. (line 397)
+* POSIXLY_CORRECT: Bash Variables. (line 402)
+* PPID: Bash Variables. (line 411)
+* PROMPT_COMMAND: Bash Variables. (line 415)
+* PROMPT_DIRTRIM: Bash Variables. (line 419)
+* PS1: Bourne Shell Variables.
+ (line 48)
+* PS2: Bourne Shell Variables.
+ (line 53)
+* PS3: Bash Variables. (line 425)
+* PS4: Bash Variables. (line 430)
+* PWD: Bash Variables. (line 436)
+* RANDOM: Bash Variables. (line 439)
+* REPLY: Bash Variables. (line 444)
+* revert-all-at-newline: Readline Init File Syntax.
+ (line 180)
+* SECONDS: Bash Variables. (line 447)
+* SHELL: Bash Variables. (line 453)
+* SHELLOPTS: Bash Variables. (line 458)
+* SHLVL: Bash Variables. (line 467)
+* show-all-if-ambiguous: Readline Init File Syntax.
+ (line 186)
+* show-all-if-unmodified: Readline Init File Syntax.
+ (line 192)
+* TEXTDOMAIN: Locale Translation. (line 11)
+* TEXTDOMAINDIR: Locale Translation. (line 11)
+* TIMEFORMAT: Bash Variables. (line 472)
+* TMOUT: Bash Variables. (line 510)
+* TMPDIR: Bash Variables. (line 522)
+* UID: Bash Variables. (line 526)
+* visible-stats: Readline Init File Syntax.
+ (line 201)
+
+\1f
+File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Indexes
+
+D.4 Function Index
+==================
+\0\b[index\0\b]
* Menu:
-* abort (C-g): Miscellaneous Commands.
-* accept-line (Newline, Return): Commands For History.
-* backward-char (C-b): Commands For Moving.
-* backward-delete-char (Rubout): Commands For Text.
-* backward-kill-line (C-x Rubout): Commands For Killing.
-* backward-kill-word (M-DEL): Commands For Killing.
-* backward-word (M-b): Commands For Moving.
-* beginning-of-history (M-<): Commands For History.
-* beginning-of-line (C-a): Commands For Moving.
-* call-last-kbd-macro (C-x e): Keyboard Macros.
-* capitalize-word (M-c): Commands For Text.
-* character-search (C-]): Miscellaneous Commands.
-* character-search-backward (M-C-]): Miscellaneous Commands.
-* clear-screen (C-l): Commands For Moving.
-* complete (TAB): Commands For Completion.
-* copy-backward-word (): Commands For Killing.
-* copy-forward-word (): Commands For Killing.
-* copy-region-as-kill (): Commands For Killing.
-* delete-char (C-d): Commands For Text.
-* delete-horizontal-space (): Commands For Killing.
-* digit-argument (M-0, M-1, ... M-): Numeric Arguments.
+* abort (C-g): Miscellaneous Commands.
+ (line 10)
+* accept-line (Newline or Return): Commands For History. (line 6)
+* backward-char (C-b): Commands For Moving. (line 15)
+* backward-delete-char (Rubout): Commands For Text. (line 11)
+* backward-kill-line (C-x Rubout): Commands For Killing. (line 9)
+* backward-kill-word (M-<DEL>): Commands For Killing. (line 24)
+* backward-word (M-b): Commands For Moving. (line 22)
+* beginning-of-history (M-<): Commands For History. (line 20)
+* beginning-of-line (C-a): Commands For Moving. (line 6)
+* call-last-kbd-macro (C-x e): Keyboard Macros. (line 13)
+* capitalize-word (M-c): Commands For Text. (line 46)
+* character-search (C-]): Miscellaneous Commands.
+ (line 41)
+* character-search-backward (M-C-]): Miscellaneous Commands.
+ (line 46)
+* clear-screen (C-l): Commands For Moving. (line 34)
+* complete (<TAB>): Commands For Completion.
+ (line 6)
+* copy-backward-word (): Commands For Killing. (line 58)
+* copy-forward-word (): Commands For Killing. (line 63)
+* copy-region-as-kill (): Commands For Killing. (line 54)
+* delete-char (C-d): Commands For Text. (line 6)
+* delete-char-or-list (): Commands For Completion.
+ (line 34)
+* delete-horizontal-space (): Commands For Killing. (line 46)
+* digit-argument (M-0, M-1, ... M--): Numeric Arguments. (line 6)
* do-uppercase-version (M-a, M-b, M-X, ...): Miscellaneous Commands.
-* downcase-word (M-l): Commands For Text.
-* dump-functions (): Miscellaneous Commands.
-* dump-macros (): Miscellaneous Commands.
-* dump-variables (): Miscellaneous Commands.
-* end-kbd-macro (C-x )): Keyboard Macros.
-* end-of-history (M->): Commands For History.
-* end-of-line (C-e): Commands For Moving.
-* exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
-* forward-char (C-f): Commands For Moving.
-* forward-search-history (C-s): Commands For History.
-* forward-word (M-f): Commands For Moving.
-* history-search-backward (): Commands For History.
-* history-search-forward (): Commands For History.
-* insert-comment (M-#): Miscellaneous Commands.
-* insert-completions (M-*): Commands For Completion.
-* kill-line (C-k): Commands For Killing.
-* kill-region (): Commands For Killing.
-* kill-whole-line (): Commands For Killing.
-* kill-word (M-d): Commands For Killing.
-* next-history (C-n): Commands For History.
+ (line 14)
+* downcase-word (M-l): Commands For Text. (line 42)
+* dump-functions (): Miscellaneous Commands.
+ (line 64)
+* dump-macros (): Miscellaneous Commands.
+ (line 76)
+* dump-variables (): Miscellaneous Commands.
+ (line 70)
+* end-kbd-macro (C-x )): Keyboard Macros. (line 9)
+* end-of-history (M->): Commands For History. (line 23)
+* end-of-line (C-e): Commands For Moving. (line 9)
+* exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
+ (line 36)
+* forward-backward-delete-char (): Commands For Text. (line 15)
+* forward-char (C-f): Commands For Moving. (line 12)
+* forward-search-history (C-s): Commands For History. (line 31)
+* forward-word (M-f): Commands For Moving. (line 18)
+* history-search-backward (): Commands For History. (line 51)
+* history-search-forward (): Commands For History. (line 46)
+* insert-comment (M-#): Miscellaneous Commands.
+ (line 51)
+* insert-completions (M-*): Commands For Completion.
+ (line 18)
+* kill-line (C-k): Commands For Killing. (line 6)
+* kill-region (): Commands For Killing. (line 50)
+* kill-whole-line (): Commands For Killing. (line 15)
+* kill-word (M-d): Commands For Killing. (line 19)
+* menu-complete (): Commands For Completion.
+ (line 22)
+* next-history (C-n): Commands For History. (line 17)
* non-incremental-forward-search-history (M-n): Commands For History.
+ (line 41)
* non-incremental-reverse-search-history (M-p): Commands For History.
-* possible-completions (M-?): Commands For Completion.
-* prefix-meta (ESC): Miscellaneous Commands.
-* previous-history (C-p): Commands For History.
-* quoted-insert (C-q, C-v): Commands For Text.
-* re-read-init-file (C-x C-r): Miscellaneous Commands.
-* redraw-current-line (): Commands For Moving.
-* reverse-search-history (C-r): Commands For History.
-* revert-line (M-r): Miscellaneous Commands.
-* self-insert (a, b, A, 1, !, ...): Commands For Text.
-* set-mark (C-@): Miscellaneous Commands.
-* start-kbd-macro (C-x (): Keyboard Macros.
-* tab-insert (M-TAB): Commands For Text.
-* tilde-expand (M-~): Miscellaneous Commands.
-* transpose-chars (C-t): Commands For Text.
-* transpose-words (M-t): Commands For Text.
-* undo (C-_, C-x C-u): Miscellaneous Commands.
-* universal-argument (): Numeric Arguments.
-* unix-line-discard (C-u): Commands For Killing.
-* unix-word-rubout (C-w): Commands For Killing.
-* upcase-word (M-u): Commands For Text.
-* yank (C-y): Commands For Killing.
-* yank-last-arg (M-., M-_): Commands For History.
-* yank-nth-arg (M-C-y): Commands For History.
-* yank-pop (M-y): Commands For Killing.
-
-\1f
-File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Top
-
-Concept Index
-*************
+ (line 36)
+* overwrite-mode (): Commands For Text. (line 50)
+* possible-completions (M-?): Commands For Completion.
+ (line 15)
+* prefix-meta (<ESC>): Miscellaneous Commands.
+ (line 18)
+* previous-history (C-p): Commands For History. (line 13)
+* quoted-insert (C-q or C-v): Commands For Text. (line 20)
+* re-read-init-file (C-x C-r): Miscellaneous Commands.
+ (line 6)
+* redraw-current-line (): Commands For Moving. (line 38)
+* reverse-search-history (C-r): Commands For History. (line 27)
+* revert-line (M-r): Miscellaneous Commands.
+ (line 25)
+* self-insert (a, b, A, 1, !, ...): Commands For Text. (line 24)
+* set-mark (C-@): Miscellaneous Commands.
+ (line 32)
+* start-kbd-macro (C-x (): Keyboard Macros. (line 6)
+* transpose-chars (C-t): Commands For Text. (line 27)
+* transpose-words (M-t): Commands For Text. (line 33)
+* undo (C-_ or C-x C-u): Miscellaneous Commands.
+ (line 22)
+* universal-argument (): Numeric Arguments. (line 10)
+* unix-filename-rubout (): Commands For Killing. (line 41)
+* unix-line-discard (C-u): Commands For Killing. (line 12)
+* unix-word-rubout (C-w): Commands For Killing. (line 37)
+* upcase-word (M-u): Commands For Text. (line 38)
+* yank (C-y): Commands For Killing. (line 68)
+* yank-last-arg (M-. or M-_): Commands For History. (line 65)
+* yank-nth-arg (M-C-y): Commands For History. (line 56)
+* yank-pop (M-y): Commands For Killing. (line 71)
+
+\1f
+File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Indexes
+
+D.5 Concept Index
+=================
+\0\b[index\0\b]
* Menu:
-* alias expansion: Aliases.
-* arithmetic evaluation: Arithmetic Evaluation.
-* arithmetic expansion: Arithmetic Expansion.
-* arithmetic, shell: Shell Arithmetic.
-* arrays: Arrays.
-* background: Job Control Basics.
-* Bash configuration: Basic Installation.
-* Bash installation: Basic Installation.
-* Bourne shell: Basic Shell Features.
-* brace expansion: Brace Expansion.
-* builtin: Definitions.
-* command editing: Readline Bare Essentials.
-* command execution: Command Search and Execution.
-* command history: Bash History Facilities.
-* command search: Command Search and Execution.
-* command substitution: Command Substitution.
-* command timing: Pipelines.
-* commands, conditional: Conditional Constructs.
-* commands, grouping: Command Grouping.
-* commands, lists: Lists.
-* commands, looping: Looping Constructs.
-* commands, pipelines: Pipelines.
-* commands, simple: Simple Commands.
-* comments, shell: Comments.
-* configuration: Basic Installation.
-* control operator: Definitions.
-* editing command lines: Readline Bare Essentials.
-* environment: Environment.
-* evaluation, arithmetic: Arithmetic Evaluation.
-* event designators: Event Designators.
-* exit status <1>: Definitions.
-* exit status: Exit Status.
-* expansion: Shell Expansions.
-* expansion, arithmetic: Arithmetic Expansion.
-* expansion, brace: Brace Expansion.
-* expansion, filename: Filename Expansion.
-* expansion, parameter: Shell Parameter Expansion.
-* expansion, pathname: Filename Expansion.
-* expansion, tilde: Tilde Expansion.
-* expressions, arithmetic: Arithmetic Evaluation.
-* expressions, conditional: Bash Conditional Expressions.
-* field: Definitions.
-* filename: Definitions.
-* filename expansion: Filename Expansion.
-* foreground: Job Control Basics.
-* functions, shell: Shell Functions.
-* history events: Event Designators.
-* history expansion: History Interaction.
-* history list: Bash History Facilities.
-* History, how to use: Job Control Variables.
-* identifier: Definitions.
-* initialization file, readline: Readline Init File.
-* installation: Basic Installation.
-* interaction, readline: Readline Interaction.
-* interactive shell <1>: Is This Shell Interactive?.
-* interactive shell: Invoking Bash.
-* job: Definitions.
-* job control <1>: Definitions.
-* job control: Job Control Basics.
-* kill ring: Readline Killing Commands.
-* killing text: Readline Killing Commands.
-* localization: Locale Translation.
-* metacharacter: Definitions.
-* name: Definitions.
-* notation, readline: Readline Bare Essentials.
-* operator, shell: Definitions.
-* parameter expansion: Shell Parameter Expansion.
-* parameters: Shell Parameters.
-* parameters, positional: Positional Parameters.
-* parameters, special: Special Parameters.
-* pathname expansion: Filename Expansion.
-* pipeline: Pipelines.
-* POSIX: Definitions.
-* POSIX Mode: Bash POSIX Mode.
-* process group: Definitions.
-* process group ID: Definitions.
-* process substitution: Process Substitution.
-* prompting: Printing a Prompt.
-* quoting: Quoting.
-* quoting, ANSI: ANSI-C Quoting.
-* Readline, how to use: Modifiers.
-* redirection: Redirections.
-* reserved word: Definitions.
-* restricted shell: The Restricted Shell.
-* return status: Definitions.
-* shell function: Shell Functions.
-* shell script: Shell Scripts.
-* shell variable: Shell Parameters.
-* signal: Definitions.
-* signal handling: Signals.
-* special builtin: Definitions.
-* startup files: Bash Startup Files.
-* suspending jobs: Job Control Basics.
-* tilde expansion: Tilde Expansion.
-* token: Definitions.
-* variable, shell: Shell Parameters.
-* word: Definitions.
-* word splitting: Word Splitting.
-* yanking text: Readline Killing Commands.
+* alias expansion: Aliases. (line 6)
+* arithmetic evaluation: Shell Arithmetic. (line 6)
+* arithmetic expansion: Arithmetic Expansion.
+ (line 6)
+* arithmetic, shell: Shell Arithmetic. (line 6)
+* arrays: Arrays. (line 6)
+* background: Job Control Basics. (line 6)
+* Bash configuration: Basic Installation. (line 6)
+* Bash installation: Basic Installation. (line 6)
+* Bourne shell: Basic Shell Features.
+ (line 6)
+* brace expansion: Brace Expansion. (line 6)
+* builtin: Definitions. (line 17)
+* command editing: Readline Bare Essentials.
+ (line 6)
+* command execution: Command Search and Execution.
+ (line 6)
+* command expansion: Simple Command Expansion.
+ (line 6)
+* command history: Bash History Facilities.
+ (line 6)
+* command search: Command Search and Execution.
+ (line 6)
+* command substitution: Command Substitution.
+ (line 6)
+* command timing: Pipelines. (line 9)
+* commands, compound: Compound Commands. (line 6)
+* commands, conditional: Conditional Constructs.
+ (line 6)
+* commands, grouping: Command Grouping. (line 6)
+* commands, lists: Lists. (line 6)
+* commands, looping: Looping Constructs. (line 6)
+* commands, pipelines: Pipelines. (line 6)
+* commands, shell: Shell Commands. (line 6)
+* commands, simple: Simple Commands. (line 6)
+* comments, shell: Comments. (line 6)
+* completion builtins: Programmable Completion Builtins.
+ (line 6)
+* configuration: Basic Installation. (line 6)
+* control operator: Definitions. (line 21)
+* coprocess: Coprocesses. (line 6)
+* directory stack: The Directory Stack. (line 6)
+* editing command lines: Readline Bare Essentials.
+ (line 6)
+* environment: Environment. (line 6)
+* evaluation, arithmetic: Shell Arithmetic. (line 6)
+* event designators: Event Designators. (line 6)
+* execution environment: Command Execution Environment.
+ (line 6)
+* exit status <1>: Exit Status. (line 6)
+* exit status: Definitions. (line 26)
+* expansion: Shell Expansions. (line 6)
+* expansion, arithmetic: Arithmetic Expansion.
+ (line 6)
+* expansion, brace: Brace Expansion. (line 6)
+* expansion, filename: Filename Expansion. (line 9)
+* expansion, parameter: Shell Parameter Expansion.
+ (line 6)
+* expansion, pathname: Filename Expansion. (line 9)
+* expansion, tilde: Tilde Expansion. (line 6)
+* expressions, arithmetic: Shell Arithmetic. (line 6)
+* expressions, conditional: Bash Conditional Expressions.
+ (line 6)
+* field: Definitions. (line 30)
+* filename: Definitions. (line 35)
+* filename expansion: Filename Expansion. (line 9)
+* foreground: Job Control Basics. (line 6)
+* functions, shell: Shell Functions. (line 6)
+* history builtins: Bash History Builtins.
+ (line 6)
+* history events: Event Designators. (line 7)
+* history expansion: History Interaction. (line 6)
+* history list: Bash History Facilities.
+ (line 6)
+* History, how to use: Programmable Completion Builtins.
+ (line 225)
+* identifier: Definitions. (line 51)
+* initialization file, readline: Readline Init File. (line 6)
+* installation: Basic Installation. (line 6)
+* interaction, readline: Readline Interaction.
+ (line 6)
+* interactive shell <1>: Interactive Shells. (line 6)
+* interactive shell: Invoking Bash. (line 127)
+* internationalization: Locale Translation. (line 6)
+* job: Definitions. (line 38)
+* job control <1>: Job Control Basics. (line 6)
+* job control: Definitions. (line 42)
+* kill ring: Readline Killing Commands.
+ (line 19)
+* killing text: Readline Killing Commands.
+ (line 6)
+* localization: Locale Translation. (line 6)
+* login shell: Invoking Bash. (line 124)
+* matching, pattern: Pattern Matching. (line 6)
+* metacharacter: Definitions. (line 46)
+* name: Definitions. (line 51)
+* native languages: Locale Translation. (line 6)
+* notation, readline: Readline Bare Essentials.
+ (line 6)
+* operator, shell: Definitions. (line 57)
+* parameter expansion: Shell Parameter Expansion.
+ (line 6)
+* parameters: Shell Parameters. (line 6)
+* parameters, positional: Positional Parameters.
+ (line 6)
+* parameters, special: Special Parameters. (line 6)
+* pathname expansion: Filename Expansion. (line 9)
+* pattern matching: Pattern Matching. (line 6)
+* pipeline: Pipelines. (line 6)
+* POSIX: Definitions. (line 9)
+* POSIX Mode: Bash POSIX Mode. (line 6)
+* process group: Definitions. (line 62)
+* process group ID: Definitions. (line 66)
+* process substitution: Process Substitution.
+ (line 6)
+* programmable completion: Programmable Completion.
+ (line 6)
+* prompting: Printing a Prompt. (line 6)
+* quoting: Quoting. (line 6)
+* quoting, ANSI: ANSI-C Quoting. (line 6)
+* Readline, how to use: Job Control Variables.
+ (line 24)
+* redirection: Redirections. (line 6)
+* reserved word: Definitions. (line 70)
+* restricted shell: The Restricted Shell.
+ (line 6)
+* return status: Definitions. (line 75)
+* shell arithmetic: Shell Arithmetic. (line 6)
+* shell function: Shell Functions. (line 6)
+* shell script: Shell Scripts. (line 6)
+* shell variable: Shell Parameters. (line 6)
+* shell, interactive: Interactive Shells. (line 6)
+* signal: Definitions. (line 78)
+* signal handling: Signals. (line 6)
+* special builtin <1>: Special Builtins. (line 6)
+* special builtin: Definitions. (line 82)
+* startup files: Bash Startup Files. (line 6)
+* suspending jobs: Job Control Basics. (line 6)
+* tilde expansion: Tilde Expansion. (line 6)
+* token: Definitions. (line 86)
+* translation, native languages: Locale Translation. (line 6)
+* variable, shell: Shell Parameters. (line 6)
+* variables, readline: Readline Init File Syntax.
+ (line 37)
+* word: Definitions. (line 90)
+* word splitting: Word Splitting. (line 6)
+* yanking text: Readline Killing Commands.
+ (line 6)
\1f
Tag Table:
-Node: Top\7f1005
-Node: Introduction\7f3109
-Node: What is Bash?\7f3334
-Node: What is a shell?\7f4418
-Node: Definitions\7f6299
-Node: Basic Shell Features\7f8960
-Node: Shell Syntax\7f10481
-Node: Shell Operation\7f10771
-Node: Quoting\7f12005
-Node: Escape Character\7f13040
-Node: Single Quotes\7f13471
-Node: Double Quotes\7f13800
-Node: ANSI-C Quoting\7f14496
-Node: Locale Translation\7f15228
-Node: Comments\7f15649
-Node: Simple Commands\7f16173
-Node: Pipelines\7f16762
-Node: Lists\7f17833
-Node: Looping Constructs\7f19108
-Node: Conditional Constructs\7f20285
-Node: Command Grouping\7f22352
-Node: Shell Functions\7f23738
-Node: Shell Parameters\7f25511
-Node: Positional Parameters\7f26834
-Node: Special Parameters\7f27528
-Node: Shell Expansions\7f30094
-Node: Shell Parameter Expansion\7f32098
-Node: Command Substitution\7f38106
-Node: Process Substitution\7f39106
-Node: Word Splitting\7f40012
-Node: Filename Expansion\7f41464
-Node: Quote Removal\7f43830
-Node: Redirections\7f44116
-Node: Executing Commands\7f49857
-Node: Command Search and Execution\7f50312
-Node: Environment\7f52046
-Node: Exit Status\7f53682
-Node: Signals\7f54699
-Node: Shell Scripts\7f55910
-Node: Bourne Shell Features\7f57779
-Node: Bourne Shell Builtins\7f58449
-Node: Bourne Shell Variables\7f66803
-Node: Other Bourne Shell Features\7f68340
-Node: Major Differences From The Bourne Shell\7f69097
-Node: Csh Features\7f79457
-Node: Brace Expansion\7f80375
-Node: Tilde Expansion\7f81930
-Node: C Shell Builtins\7f82562
-Node: C Shell Variables\7f87118
-Node: Korn Shell Features\7f87526
-Node: Korn Shell Constructs\7f88254
-Node: Korn Shell Builtins\7f89969
-Node: Korn Shell Variables\7f92127
-Node: Aliases\7f93686
-Node: Alias Builtins\7f96150
-Node: Bash Features\7f96766
-Node: Invoking Bash\7f97757
-Node: Bash Startup Files\7f101622
-Node: Is This Shell Interactive?\7f105197
-Node: Bash Builtins\7f106180
-Node: The Set Builtin\7f122035
-Node: Bash Conditional Expressions\7f127410
-Node: Bash Variables\7f132061
-Node: Shell Arithmetic\7f142095
-Node: Arithmetic Evaluation\7f142563
-Node: Arithmetic Expansion\7f144593
-Node: Arithmetic Builtins\7f145397
-Node: Arrays\7f145868
-Node: Printing a Prompt\7f148895
-Node: The Restricted Shell\7f150493
-Node: Bash POSIX Mode\7f151723
-Node: Job Control\7f155407
-Node: Job Control Basics\7f155872
-Node: Job Control Builtins\7f160015
-Node: Job Control Variables\7f162938
-Node: Using History Interactively\7f164085
-Node: Bash History Facilities\7f164674
-Node: History Interaction\7f167072
-Node: Event Designators\7f169634
-Node: Word Designators\7f170557
-Node: Modifiers\7f171806
-Node: Command Line Editing\7f173123
-Node: Introduction and Notation\7f173783
-Node: Readline Interaction\7f174791
-Node: Readline Bare Essentials\7f175979
-Node: Readline Movement Commands\7f177508
-Node: Readline Killing Commands\7f178398
-Node: Readline Arguments\7f180100
-Node: Searching\7f181073
-Node: Readline Init File\7f182709
-Node: Readline Init File Syntax\7f183765
-Node: Conditional Init Constructs\7f191554
-Node: Sample Init File\7f193835
-Node: Bindable Readline Commands\7f196868
-Node: Commands For Moving\7f197618
-Node: Commands For History\7f198465
-Node: Commands For Text\7f201138
-Node: Commands For Killing\7f202880
-Node: Numeric Arguments\7f204906
-Node: Commands For Completion\7f206030
-Node: Keyboard Macros\7f208992
-Node: Miscellaneous Commands\7f209550
-Node: Readline vi Mode\7f213766
-Node: Installing Bash\7f214642
-Node: Basic Installation\7f215711
-Node: Compilers and Options\7f218636
-Node: Compiling For Multiple Architectures\7f219370
-Node: Installation Names\7f221027
-Node: Specifying the System Type\7f221749
-Node: Sharing Defaults\7f222460
-Node: Operation Controls\7f223125
-Node: Optional Features\7f224030
-Node: Reporting Bugs\7f228913
-Node: Builtin Index\7f229993
-Node: Reserved Word Index\7f233406
-Node: Variable Index\7f234714
-Node: Function Index\7f239899
-Node: Concept Index\7f244257
+Node: Top\7f1344
+Node: Introduction\7f3181
+Node: What is Bash?\7f3409
+Node: What is a shell?\7f4522
+Node: Definitions\7f7062
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+Node: Coprocesses\7f37430
+Node: Shell Functions\7f38919
+Node: Shell Parameters\7f43380
+Node: Positional Parameters\7f45796
+Node: Special Parameters\7f46696
+Node: Shell Expansions\7f49660
+Node: Brace Expansion\7f51585
+Node: Tilde Expansion\7f54338
+Node: Shell Parameter Expansion\7f56689
+Node: Command Substitution\7f65520
+Node: Arithmetic Expansion\7f66853
+Node: Process Substitution\7f67703
+Node: Word Splitting\7f68753
+Node: Filename Expansion\7f70376
+Node: Pattern Matching\7f72516
+Node: Quote Removal\7f76155
+Node: Redirections\7f76450
+Node: Executing Commands\7f84593
+Node: Simple Command Expansion\7f85263
+Node: Command Search and Execution\7f87193
+Node: Command Execution Environment\7f89530
+Node: Environment\7f92329
+Node: Exit Status\7f93989
+Node: Signals\7f95610
+Node: Shell Scripts\7f97578
+Node: Shell Builtin Commands\7f100096
+Node: Bourne Shell Builtins\7f101773
+Node: Bash Builtins\7f119091
+Node: Modifying Shell Behavior\7f142764
+Node: The Set Builtin\7f143109
+Node: The Shopt Builtin\7f152149
+Node: Special Builtins\7f163011
+Node: Shell Variables\7f163990
+Node: Bourne Shell Variables\7f164430
+Node: Bash Variables\7f166411
+Node: Bash Features\7f188729
+Node: Invoking Bash\7f189612
+Node: Bash Startup Files\7f195421
+Node: Interactive Shells\7f200390
+Node: What is an Interactive Shell?\7f200800
+Node: Is this Shell Interactive?\7f201449
+Node: Interactive Shell Behavior\7f202264
+Node: Bash Conditional Expressions\7f205544
+Node: Shell Arithmetic\7f209123
+Node: Aliases\7f211869
+Node: Arrays\7f214441
+Node: The Directory Stack\7f218283
+Node: Directory Stack Builtins\7f218997
+Node: Printing a Prompt\7f221889
+Node: The Restricted Shell\7f224641
+Node: Bash POSIX Mode\7f226473
+Node: Job Control\7f234326
+Node: Job Control Basics\7f234786
+Node: Job Control Builtins\7f239399
+Node: Job Control Variables\7f243763
+Node: Command Line Editing\7f244921
+Node: Introduction and Notation\7f246488
+Node: Readline Interaction\7f248110
+Node: Readline Bare Essentials\7f249301
+Node: Readline Movement Commands\7f251090
+Node: Readline Killing Commands\7f252055
+Node: Readline Arguments\7f253975
+Node: Searching\7f255019
+Node: Readline Init File\7f257205
+Node: Readline Init File Syntax\7f258352
+Node: Conditional Init Constructs\7f271586
+Node: Sample Init File\7f274119
+Node: Bindable Readline Commands\7f277236
+Node: Commands For Moving\7f278443
+Node: Commands For History\7f279587
+Node: Commands For Text\7f282742
+Node: Commands For Killing\7f285415
+Node: Numeric Arguments\7f287866
+Node: Commands For Completion\7f289005
+Node: Keyboard Macros\7f292772
+Node: Miscellaneous Commands\7f293343
+Node: Readline vi Mode\7f298654
+Node: Programmable Completion\7f299568
+Node: Programmable Completion Builtins\7f305401
+Node: Using History Interactively\7f313827
+Node: Bash History Facilities\7f314511
+Node: Bash History Builtins\7f317425
+Node: History Interaction\7f321282
+Node: Event Designators\7f323987
+Node: Word Designators\7f325002
+Node: Modifiers\7f326641
+Node: Installing Bash\7f328045
+Node: Basic Installation\7f329182
+Node: Compilers and Options\7f331874
+Node: Compiling For Multiple Architectures\7f332615
+Node: Installation Names\7f334279
+Node: Specifying the System Type\7f335097
+Node: Sharing Defaults\7f335813
+Node: Operation Controls\7f336486
+Node: Optional Features\7f337444
+Node: Reporting Bugs\7f346846
+Node: Major Differences From The Bourne Shell\7f348040
+Node: GNU Free Documentation License\7f364727
+Node: Indexes\7f387188
+Node: Builtin Index\7f387642
+Node: Reserved Word Index\7f394396
+Node: Variable Index\7f396844
+Node: Function Index\7f408650
+Node: Concept Index\7f415382
\1f
End Tag Table
projects / platform / upstream / bash.git / blobdiff