-This is Info file bashref.info, produced by Makeinfo version 1.67 from
-the input file /usr/homes/chet/src/bash/src/doc/bashref.texi.
-
-INFO-DIR-SECTION Utilities
-START-INFO-DIR-ENTRY
-* Bash: (bash). The GNU Bourne-Again SHell.
-END-INFO-DIR-ENTRY
+This is bashref.info, produced by makeinfo version 4.13 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 4.2, 28 December 2010).
-This is Edition 2.2, last updated 1 April 1998,
-of `The GNU Bash Reference Manual',
-for `Bash', Version 2.02.
+ This is Edition 4.2, last updated 28 December 2010, of `The GNU Bash
+Reference Manual', for `Bash', Version 4.2.
-Copyright (C) 1991, 1993, 1996, 1997 Free Software Foundation, Inc.
+ Copyright (C) 1988-2010 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 1.3 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 Free Software 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 2.2, last updated 1 April 1998, of `The GNU Bash
-Reference Manual', for `Bash', Version 2.02.
+This text is a brief description of the features that are present in
+the Bash shell (version 4.2, 28 December 2010).
- Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
+ This is Edition 4.2, last updated 28 December 2010, of `The GNU Bash
+Reference Manual', for `Bash', Version 4.2.
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.
-
+* 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?
-=============
-
- 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 an `sh'-compatible shell that 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.
+1.1 What is Bash?
+=================
- 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
-MS-DOS, OS/2, Windows 95, and Windows NT.
+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 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 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 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. The term macro processor means functionality where text and
+symbols are expanded to create larger expressions.
- 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. Files containing
+ 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 like
-`/bin', allowing users or groups to establish custom environments.
+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.
- A shell allows execution of Unix commands, both synchronously and
+ 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, 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.
+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':
commands, control structures, shell functions, shell parameters, shell
* Shell Syntax:: What your input means to the shell.
* 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.
\1f
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::. These 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 (*note Shell
- Commands::.).
+ 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 (*note 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
+ Each of the shell metacharacters (*note Definitions::) has special
meaning to the shell and must be quoted if it is to represent itself.
-There are three quoting mechanisms: the ESCAPE CHARACTER, single
+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
+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
-.............
-
- 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 (*note Shell Expansions::.). The backslash retains its
-special meaning only when followed by one of the following characters:
-`$', ``', `"', `\', or `newline'. Within double quotes, backslashes
-that are followed by one of these characters are removed. Backslashes
-preceding characters without a special meaning are left unmodified. A
-double quote may be quoted within double quotes by preceding it with a
-backslash.
+3.1.2.3 Double Quotes
+.....................
+
+Enclosing characters in double quotes (`"') preserves the literal value
+of all characters within the quotes, with the exception of `$', ``',
+`\', and, 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'. 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)
backspace
`\e'
+`\E'
an escape character (not ANSI C)
`\f'
`\\'
backslash
+`\''
+ single quote
+
+`\"'
+ double quote
+
`\NNN'
- the character whose `ASCII' code is the octal value NNN (one to
+ the eight-bit character whose value is the octal value NNN (one to
three digits)
-`\xNNN'
- the character whose `ASCII' code is the hexadecimal 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.
+`\uHHHH'
+ the Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHH (one to four hex digits)
+
+`\UHHHHHHHH'
+ the Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHHHHHH (one to eight hex digits)
+
+`\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. *Note Is This Shell Interactive?::, for a
-description of what makes a shell interactive.
+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
-Shell Commands
-==============
+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:
* 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.
+* Compound Commands:: Shell commands for control flow.
+* Coprocesses:: Two-way communication between commands.
+* GNU Parallel:: Running commands in parallel.
\1f
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 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.
+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: 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 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
+specified by POSIX. When the shell is in POSIX mode (*note Bash POSIX
+Mode::), it does not recognize `time' as a reserved word if the next
+token begins with a `-'. 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.
+
+ When the shell is in POSIX mode (*note Bash POSIX Mode::), `time'
+may be followed by a newline. In this case, the shell displays the
+total user and system time consumed by the shell and its children. The
+`TIMEFORMAT' variable may be used to specify the format of the time
+information.
+
+ 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 (*note
-Command Execution Environment::.). 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 negation
-of the exit status of the last command.
+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: Shell Commands
+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 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). The standard
-input for asynchronous commands, in the absence of any explicit
-redirections, is redirected from `/dev/null'.
+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'.
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.
- The control operators `&&' and `||' denote AND lists and OR lists,
-respectively. An AND list has the form
- COMMAND && COMMAND2
+ 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, COMMAND returns an exit status of
-zero.
+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: Shell Commands
+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.
- Bash supports the following looping constructs.
+\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
+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'
`for'
The syntax of the `for' command is:
- for NAME [in WORDS ...]; do COMMANDS; done
+ for NAME [ [in [WORDS ...] ] ; ] do COMMANDS; done
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, `in "$@"' is assumed. The return status is
- the exit status of the last command that executes. If there are
- no items in the expansion of WORDS, no commands are executed, and
- the return status is zero.
-
- The `break' and `continue' builtins (*note Bourne Shell Builtins::.)
+ WORDS' is not present, the `for' command executes the COMMANDS
+ once for each positional parameter that is set, as if `in "$@"'
+ 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 COMMANDS 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: Shell Commands
+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:
`case WORD in [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]... esac'
`case' will selectively execute the COMMAND-LIST corresponding to
- the first PATTERN that matches WORD. The `|' is used to separate
+ 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 `;;'. The WORD
- undergoes tilde expansion, parameter expansion, command
+ 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 `;;'. The first pattern that matches determines the
- command-list that is executed.
+ 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.
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 specifed. The `PS3' prompt is then displayed and a line
+ 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
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.
+ 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
(( EXPRESSION ))
The arithmetic EXPRESSION is evaluated according to the rules
- described below (*note Shell Arithmetic::.). If the value of the
+ 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.
`[[...]]'
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
+ 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.
+ performed. Conditional operators such as `-f' must be unquoted to
+ be recognized as primaries.
+
+ When used with `[[', the `<' and `>' operators sort
+ lexicographically using the current locale.
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::. The return
- value is 0 if the string matches or does not match the pattern,
- respectively, and 1 otherwise. Any part of the pattern may be
- quoted to force it to be matched as a string.
+ 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:
`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 && and || commands do not execute EXPRESSION2 if the value of
- EXPRESSION1 is sufficient to determine the return value of the
- entire conditional expression.
\1f
-File: bashref.info, Node: Command Grouping, Prev: Conditional Constructs, Up: Shell Commands
+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 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.
+ 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; }
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: Coprocesses, Next: GNU Parallel, 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. NAME must not be supplied if COMMAND is a
+simple command (*note Simple Commands::); otherwise, it is interpreted
+as the first word of the simple command.
+
+ 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: GNU Parallel, Prev: Coprocesses, Up: Shell Commands
+
+3.2.6 GNU Parallel
+------------------
+
+GNU Parallel, as its name suggests, can be used to build and run
+commands in parallel. You may run the same command with different
+arguments, whether they are filenames, usernames, hostnames, or lines
+read from files.
+
+ For a complete description, refer to the GNU Parallel documentation.
+A few examples should provide a brief introduction to its use.
+
+ For example, it is easy to prefix each line in a text file with a
+specified string:
+ cat file | parallel -k echo prefix_string
+ The `-k' option is required to preserve the lines' order.
+
+ Similarly, you can append a specified string to each line in a text
+file:
+ cat file | parallel -k echo {} append_string
+
+ You can use Parallel to move files from the current directory when
+the number of files is too large to process with one `mv' invocation:
+ ls | parallel mv {} destdir
+
+ As you can see, the {} is replaced with each line read from standard
+input. This will run as many `mv' commands as there are files in the
+current directory. You can emulate a parallel `xargs' by adding the
+`-X' option:
+ ls | parallel -X mv {} destdir
+
+ GNU Parallel can replace certain common idioms that operate on lines
+read from a file (in this case, filenames):
+ for x in $(cat list); do
+ do-something1 $x config-$x
+ do-something2 < $x
+ done | process-output
+
+with a more compact syntax reminiscent of lambdas:
+ cat list | parallel "do-something1 {} config-{} ; do-something2 < {}" | process-output
+
+ Parallel provides a built-in mechanism to remove filename
+extensions, which lends itself to batch file transformations or
+renaming:
+ ls *.gz | parallel -j+0 "zcat {} | bzip2 >{.}.bz2 && rm {}"
+ This will recompress all files in the current directory with names
+ending in .gz using bzip2, running one job per CPU (-j+0) in parallel.
+
+ If a command generates output, you may want to preserve the input
+order in the output. For instance, the following command
+ { echo foss.org.my ; echo debian.org; echo freenetproject.org; } | parallel traceroute
+ will display as output the traceroute invocation that finishes
+first. Using the `-k' option, as we saw above
+ { echo foss.org.my ; echo debian.org; echo freenetproject.org; } | parallel -k traceroute
+ will ensure that the output of `traceroute foss.org.my' is displayed
+first.
+
+\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. 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.
- 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.
+ Functions are declared using this syntax:
+ NAME () COMPOUND-COMMAND [ REDIRECTIONS ]
+ or
- Functions are declared using this syntax:
- [ `function' ] NAME () { COMMAND-LIST; }
+ `function' NAME [()] COMPOUND-COMMAND [ REDIRECTIONS ]
This defines a shell function named NAME. The reserved word
`function' is optional. If the `function' reserved word is supplied,
-the parentheses are 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.
+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 these exceptions: 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), and the `ERR' trap
+is not inherited unless the `-o errtrace' shell option has been enabled.
+*Note Bourne Shell Builtins::, for the description of the `trap'
+builtin.
+
+ The `FUNCNEST' variable, if set to a numeric value greater than 0,
+defines a maximum function nesting level. Function invocations that
+exceed the limit cause the entire command to abort.
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 the function's execution. If a numeric
-argument is given to `return', that is the function's return status;
-otherwise the functions's return status is the exit status of the last
-command executed before the `return'.
+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.
- Functions may be recursive. No limit is placed on the number of
+ 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. The `FUNCNEST' variable may be used to
+limit the depth of the function call stack and restrict the number of
+function invocations. By default, 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 `integer' attribute set (see the
-description of the `declare' builtin in *Note Bash Builtins::), then
-VALUE is subject to arithmetic expansion even if the `$((...))'
-expansion is not used (*note Arithmetic Expansion::.). Word splitting
-is not performed, with the exception of `"$@"' as explained below.
-Filename expansion is not performed.
+below). If the variable has its `integer' attribute set, then VALUE is
+evaluated as an arithmetic expression even if the `$((...))' expansion
+is not used (*note Arithmetic Expansion::). Word splitting is not
+performed, with the exception of `"$@"' as explained below. Filename
+expansion is not performed. Assignment statements may also appear as
+arguments to the `alias', `declare', `typeset', `export', `readonly',
+and `local' builtin commands.
+
+ In the context where an assignment statement is assigning a value to
+a shell variable or array index (*note Arrays::), the `+=' operator can
+be used to append to or add to the variable's previous value. When
+`+=' is applied to a variable for which the INTEGER attribute has been
+set, VALUE is evaluated as an arithmetic expression and added to the
+variable's current value, which is also evaluated. When `+=' is
+applied to an array variable using compound assignment (*note
+Arrays::), the variable's value is not unset (as it is when using `='),
+and new values are appended to the array beginning at one greater than
+the array's maximum index (for indexed arrays), or added as additional
+key-value pairs in an associative array. When applied to a
+string-valued variable, VALUE is expanded and appended to the
+variable's value.
\1f
File: bashref.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
-Positional Parameters
----------------------
+3.4.1 Positional Parameters
+---------------------------
- A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
+A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
other than the single digit `0'. Positional parameters are assigned
from the shell's arguments when it is invoked, and may be reassigned
using the `set' builtin command. Positional parameter `N' may be
-referenced as `${N}'. 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::.).
+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 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
`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
- (*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.
+ (*note Shell Scripts::), `$0' is set to the name of that file. If
+ Bash is started with the `-c' option (*note Invoking Bash::), then
+ `$0' is set to the first argument after the string to be executed,
+ if one is present. Otherwise, it is set to the filename used to
+ invoke Bash, as given by argument zero.
`_'
- At shell startup, set to the absolute filename of the shell or
- shell script being executed as passed in the argument list.
- Subsequently, expands to the last argument to the previous command,
- after expansion. Also set to the full pathname of each command
- executed and placed in the environment exported to that command.
- When checking mail, this parameter holds the name of the mail file.
+ (An underscore.) At shell startup, set to the absolute pathname
+ used to invoke the shell or shell script being executed as passed
+ in the environment or argument list. Subsequently, expands to the
+ last argument to the previous command, after expansion. Also set
+ to the full pathname used to invoke each command executed and
+ placed in the environment exported to that command. When checking
+ mail, this parameter holds the name of the mail file.
\1f
File: bashref.info, Node: Shell Expansions, Next: Redirections, Prev: Shell Parameters, Up: Basic Shell Features
-Shell Expansions
-================
+3.5 Shell Expansions
+====================
- Expansion is performed on the command line after it has been split
-into `token's. There are seven kinds of expansion performed:
+Expansion is performed on the command line after it has been split into
+`token's. There are seven kinds of expansion performed:
* brace expansion
* tilde expansion
Only brace expansion, word splitting, and filename expansion can
change the number of words of the expansion; other expansions expand a
single word to a single word. The only exceptions to this are the
-expansions of `"$@"' (*note Special Parameters::.) and `"${NAME[@]}"'
-(*note Arrays::.).
+expansions of `"$@"' (*note Special Parameters::) and `"${NAME[@]}"'
+(*note Arrays::).
- After all expansions, `quote removal' (*note Quote Removal::.) is
+ After all expansions, `quote removal' (*note Quote Removal::) is
performed.
\1f
File: bashref.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Shell Expansions
-Brace Expansion
----------------
+3.5.1 Brace Expansion
+---------------------
- Brace expansion is a mechanism by which arbitrary strings may be
+Brace expansion is a mechanism by which arbitrary strings may be
generated. This mechanism is similar to FILENAME EXPANSION (*note
-Filename Expansion::.), but the file names generated need not exist.
+Filename Expansion::), but the file names generated need not exist.
Patterns to be brace expanded take the form of an optional PREAMBLE,
-followed by a series of comma-separated strings between a pair of
-braces, followed by an optional POSTSCRIPT. The preamble is prepended
-to each string contained within the braces, and the postscript is then
-appended to each resulting string, expanding left to right.
+followed by either a series of comma-separated strings or a seqeunce
+expression between a pair of braces, followed by an optional POSTSCRIPT.
+The preamble is prefixed to each string contained within the braces, and
+the postscript is then appended to each resulting string, expanding left
+to right.
Brace expansions may be nested. The results of each expanded string
are not sorted; left to right order is preserved. For example,
bash$ 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 the context of the expansion or the text between the braces. To
+avoid conflicts with parameter expansion, the string `${' is not
+considered eligible for brace expansion.
A correctly-formed brace expansion must contain unquoted opening and
-closing braces, and at least one unquoted comma. Any incorrectly
-formed brace expansion is left unchanged.
+closing braces, and at least one unquoted comma or a valid sequence
+expression. Any incorrectly formed brace expansion is left unchanged.
+
+ A { or `,' may be quoted with a backslash to prevent its being
+considered part of a brace expression. To avoid conflicts with
+parameter expansion, the string `${' 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:
\1f
File: bashref.info, Node: Tilde Expansion, Next: Shell Parameter Expansion, Prev: Brace Expansion, Up: Shell Expansions
-Tilde Expansion
----------------
+3.5.2 Tilde Expansion
+---------------------
- If a word begins with an unquoted tilde character (`~'), all of the
+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
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
+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 `='. 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.
+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:
`~-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
-Shell Parameter Expansion
--------------------------
+3.5.3 Shell Parameter Expansion
+-------------------------------
- The `$' character introduces parameter expansion, command
-substitution, or arithmetic expansion. The parameter name or symbol to
-be expanded may be enclosed in braces, which are optional but serve to
-protect the variable to be expanded from characters immediately
-following it which could be interpreted as part of the name.
+The `$' 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
followed by a character that is not to be interpreted as part of its
name.
- If the first character of PARAMETER is an exclamation point, a level
-of variable indirection is introduced. Bash uses the value of the
-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'.
+ If the first character of PARAMETER is an exclamation point (!), a
+level of variable indirection is introduced. Bash uses the value of
+the 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'. The exceptions to this are the
+expansions of ${!PREFIX
+} and ${!NAME[@]} described below. The exclamation point must
+immediately follow the left brace in order to introduce indirection.
In each of the cases below, WORD is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
-When not performing substring expansion, Bash tests for a parameter
-that is unset or null; omitting the colon results in a test only for a
-parameter that is unset.
+
+ When not performing substring expansion, using the form described
+below, Bash tests for a parameter that is unset or null. Omitting the
+colon results in a test only for a parameter that is unset. Put
+another way, if the colon is included, the operator tests for both
+PARAMETER's existence and that its value is not null; if the colon is
+omitted, the operator tests only for existence.
`${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 the
+ 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
+ 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.
+ 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
- `${PARAMETER[OFFSET]}'. Substring indexing is zero-based unless
- the positional parameters are used, in which case the indexing
- starts at 1.
+ as an offset from the end of the value of PARAMETER. If LENGTH
+ evaluates to a number less than zero, and PARAMETER is not `@' and
+ not an indexed or associative array, it is interpreted as an
+ offset from the end of the value of PARAMETER rather than a number
+ of characters, and the expansion is the characters between the two
+ offsets. If PARAMETER is `@', the result is LENGTH positional
+ parameters beginning at OFFSET. If PARAMETER is an indexed array
+ name subscripted by `@' or `*', the result is the LENGTH members
+ of the array beginning with `${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 expanded value of PARAMETER is
`${PARAMETER#WORD}'
`${PARAMETER##WORD}'
The WORD is expanded to produce a pattern just as in filename
- expansion (*note Filename Expansion::.). If the pattern matches
+ 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
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
- 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.
+ 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
+ filename 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 in the
+ expanded value. 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
+ 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: 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
\1f
File: bashref.info, Node: Arithmetic Expansion, Next: Process Substitution, Prev: Command Substitution, Up: Shell Expansions
-Arithmetic Expansion
---------------------
+3.5.5 Arithmetic Expansion
+--------------------------
- Arithmetic expansion allows the evaluation of an arithmetic
-expression and the substitution of the result. The format for
-arithmetic expansion is:
+Arithmetic expansion allows the evaluation of an arithmetic expression
+and the substitution of the result. The format for arithmetic
+expansion is:
$(( 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 substitutions may be
-nested.
+substitution, and quote removal. Arithmetic expansions may be nested.
The evaluation is performed according to the rules listed below
-(*note Shell Arithmetic::.). If the expression is invalid, Bash prints
+(*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
-Process Substitution
---------------------
+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
+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
+ 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
+ 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.
When available, process substitution is performed simultaneously with
parameter and variable expansion, command substitution, and arithmetic
\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 `['. If one of these characters appears, then the word is regarded
-as a PATTERN, and replaced with an alphabetically sorted list of file
+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 `nullglob' option is set, and no matches are found, the word is
-removed. If the shell option `nocaseglob' is enabled, the match is
-performed without regard to the case of alphabetic characters.
+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
+ When a pattern is used for filename expansion, 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 Bash Builtins::, for a
-description of the `nocaseglob', `nullglob', and `dotglob' options.
+ 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
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
-Pattern Matching
-................
+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. The special pattern characters must be
-quoted if they are to be matched literally.
+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.2 standard:
+ defined in the POSIX standard:
alnum alpha ascii blank cntrl digit graph lower
- print punct space upper xdigit
-
+ 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
Matches one or more occurrences of the given patterns.
`@(PATTERN-LIST)'
- Matches exactly one of the given patterns.
+ 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
anywhere within a simple command or may follow a command. Redirections
are processed in the order they appear, from left to right.
+ Each redirection that may be preceded by a file descriptor number
+may instead be preceded by a word of the form {VARNAME}. In this case,
+for each redirection operator except >&- and <&-, the shell will
+allocate a file descriptor greater than 10 and assign it to {VARNAME}.
+If >&- or <&- is preceded by {VARNAME}, the value of VARNAME defines
+the file descriptor to close.
+
In the following descriptions, if the file descriptor number is
omitted, and the first character of the redirection operator is `<',
the redirection refers to the standard input (file descriptor 0). If
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, and filename expansion. If it expands to
-more than one word, Bash reports an error.
+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 made a copy of the 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.
-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.
A failure to open or create a file causes the redirection to fail.
-Redirecting Input
------------------
+ 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
+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 `noclobber' option to
the `set' builtin has been enabled, the redirection will fail if the
-filename whose name results from the expansion of WORD exists and is a
+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. 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 pair `\newline' is ignored, and `\' must be used to quote the
-characters `\', `$', and ``'.
+the character sequence `\newline' is ignored, and `\' must be used to
+quote the characters `\', `$', 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 redirection operator
- [n]<&WORD
+ The WORD is expanded and supplied to the command on its standard
+input.
-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
+3.6.8 Duplicating File Descriptors
+----------------------------------
+
+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.
+evaluates to `-', file descriptor N is closed. If N is not specified,
+the standard input (file descriptor 0) is used.
The operator
- [n]>&WORD
-
-is used similarly to duplicate output file descriptors. If `n' is not
+ [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.
+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.
-Opening File Descriptors for Reading and Writing
-------------------------------------------------
+3.6.9 Moving File Descriptors
+-----------------------------
+
+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.
- The redirection operator
- [n]<>WORD
+ 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.
-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.
+3.6.10 Opening File Descriptors for Reading and Writing
+-------------------------------------------------------
+
+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: Simple Command Expansion, Next: Command Search and Execution, Up: Executing Commands
-Simple Command Expansion
-------------------------
+3.7.1 Simple Command Expansion
+------------------------------
- When a simple command is executed, the shell performs the following
+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
processing.
2. The words that are not variable assignments or redirections are
- expanded (*note Shell Expansions::.). If any words remain after
+ 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::.).
+ Redirections::).
4. The text after the `=' in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic
\1f
File: bashref.info, Node: Command Search and Execution, Next: Command Execution Environment, Prev: Simple Command Expansion, Up: Executing Commands
-Command Search and Execution
-----------------------------
+3.7.2 Command Search and Execution
+----------------------------------
- After a command has been split into words, if it results in a simple
+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
directory containing an executable file by that name. Bash uses a
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
+ *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 an exit status of 127.
+ 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 in a
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 a
- SHELL SCRIPT and the shell executes it as described in *Note Shell
+ 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
\1f
File: bashref.info, Node: Command Execution Environment, Next: Environment, Prev: Command Search and Execution, Up: Executing Commands
-Command Execution Environment
------------------------------
+3.7.3 Command Execution Environment
+-----------------------------------
- The shell has an EXECUTION ENVIRONMENT, which consists of the
-following:
+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
* options enabled at invocation (either by default or with
command-line arguments) or by `set'
- * options enabled by `shopt'
+ * options enabled by `shopt' (*note The Shopt Builtin::)
- * shell aliases defined with `alias' (*note Aliases::.)
+ * shell aliases defined with `alias' (*note Aliases::)
* various process IDs, including those of background jobs (*note
- Lists::.), the value of `$$', and the value of `$PPID'
+ Lists::), the value of `$$', 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
* the file creation mode mask
- * shell variables marked for export, along with variables exported
- for the command, passed in the environment (*note Environment::.)
+ * 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 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.
+ 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.
+
+ 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.
+
+ 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 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'
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' option 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 shell's purposes, a command which exits with a zero exit
status has succeeded. A non-zero exit status indicates failure. This
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
\1f
File: bashref.info, Node: Signals, Prev: Exit Status, Up: Executing Commands
-Signals
--------
+3.7.6 Signals
+-------------
- When Bash is interactive, in the absence of any traps, it ignores
+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',
+is in effect (*note Job Control::), Bash ignores `SIGTTIN', `SIGTTOU',
and `SIGTSTP'.
- 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' as well.
-Commands run as a result of command substitution ignore the
-keyboard-generated job control signals `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.
-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
+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
-Bash Builtins::.), Bash sends a `SIGHUP' to all jobs when an
+The Shopt Builtin::), Bash sends a `SIGHUP' to all jobs when an
interactive login shell exits.
- When Bash receives a signal for which a trap has been set while
-waiting for a command to complete, 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.
+ 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, 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 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.
+*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: Bash 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. Many of
-the builtins have been extended by POSIX or Bash.
+* 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.
+The `:', `true', `false', and `test' builtins do not accept options and
+do not treat `--' specially. The `exit', `logout', `break',
+`continue', `let', and `shift' builtins accept and process arguments
+beginning with `-' without requiring `--'. Other builtins that accept
+arguments but are not specified as accepting options interpret
+arguments beginning with `-' as invalid options and require `--' to
+prevent this interpretation.
\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. If FILENAME does not contain a slash, the
- `$PATH' variable is used to find FILENAME. The current directory
- is searched if FILENAME is not found in `$PATH'. The return
- status is the exit status of the last command executed, or zero if
- no commands are executed. If FILENAME is not found, or cannot be
- read, the return status is non-zero.
+ `PATH' variable is used to find FILENAME. When Bash is not in
+ POSIX mode, the current directory is searched if FILENAME is not
+ found in `$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]
greater than or equal to 1.
`cd'
- cd [-LP] [DIRECTORY]
+ cd [-L|[-P [-e]]] [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; symbolic links are
- followed by default or with the `-L' option. If DIRECTORY is `-',
- it is equivalent to `$OLDPWD'. The return status is zero if the
- directory is successfully changed, non-zero otherwise.
+ If DIRECTORY begins with a slash, `CDPATH' is not used.
+
+ The `-P' option means to not follow symbolic links; symbolic links
+ are followed by default or with the `-L' option. If the `-e'
+ option is supplied with `-P' and the current working directory
+ cannot be successfully determined after a successful directory
+ change, `cd' will return an unsuccessful status. If DIRECTORY is
+ `-', it is equivalent to `$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]
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 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
+ 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'
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. 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.
+ 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 `?'.
+ 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.
character found.
`hash'
- hash [-r] [-p FILENAME] [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 `$PATH'. The `-p' option inhibits the path
- search, and FILENAME is used as the location of NAME. The `-r'
- option causes the shell to forget all remembered locations. If no
- arguments are given, information about remembered commands is
- printed. The return status is zero unless a NAME is not found or
- an invalid option is supplied.
+ hash [-r] [-p FILENAME] [-dt] [NAME]
+ Each time `hash' is invoked, it remembers the full pathnames of the
+ commands specified as NAME arguments, so they need not be searched
+ for on subsequent invocations. The commands are found by
+ searching through the directories listed in `$PATH'. Any
+ previously-remembered pathname is discarded. 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. The return status is zero unless an error is encountered
- while determining the name of the current directory or an invalid
- option is supplied.
+ 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] ...
+ 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 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. 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.
+ 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 the return value N. This may
- also be used to terminate execution of a script being executed
- with the `.' builtin, returning either N or the exit status of the
+ 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. The return status is false if `return' is used outside a
- function and not during the execution of a script by `.'.
+ 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 the positional parameters to the left by N. The positional
- parameters from N+1 ... `$#' are renamed to `$1' ... `$#'-N+1.
- 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 `$#', the positional parameters are not
- changed. The return status is zero unless N is greater than `$#'
- or less than zero, non-zero otherwise.
+ 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 EXPR. Each operator and operand
must be a separate argument. Expressions are composed of the
- primaries described below in *Note Bash Conditional Expressions::.
+ 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.
+ in decreasing order of precedence. The evaluation depends on the
+ number of arguments; see below. Operator precedence is used when
+ there are five or more arguments.
`! EXPR'
True if EXPR is false.
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
+ 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
+ The following conditions are applied in the order listed. 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. 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. The `-a' and `-o'
- operators are considered binary operators in this case.
+ 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 expression is parsed and evaluated according to precedence
using the rules listed above.
+ When used with `test' or `[', the `<' and `>' operators sort
+ lexicographically using ASCII ordering.
+
`times'
times
Print out the user and system times used by the shell and its
`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 in a form that may be reused as shell input. 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 `extdebug' option to the `shopt' builtin (*note
+ The Shopt Builtin::) for details of its effect on the `DEBUG' trap.
+ 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.
+
+ 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 following the `if'
+ or `elif' reserved words, 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.
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 subshell or subshell environment when one is
+ created.
The return status is zero unless a SIGSPEC does not specify a
valid signal.
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
variable. If the `-f' option is given, the NAMEs refer to shell
functions, and the function definition is removed. Readonly
variables and functions may not be unset. The return status is
- zero unless a NAME does not exist or is readonly.
+ 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
-======================
+4.2 Bash Builtin Commands
+=========================
- Bash uses certain shell variables in the same way as the Bourne
-shell. In some cases, Bash assigns a default value to the variable.
+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.
-`CDPATH'
- A colon-separated list of directories used as a search path for
- the `cd' builtin command.
+`alias'
+ alias [`-p'] [NAME[=VALUE] ...]
-`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::.).
+ 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::.
-`IFS'
- A list of characters that separate fields; used when the shell
- splits words as part of expansion.
+`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
-`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.
+ 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'.
-`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.
+ Options, if supplied, have the following meanings:
-`OPTARG'
- The value of the last option argument processed by the `getopts'
- builtin.
+ `-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'.
-`OPTIND'
- The index of the last option argument processed by the `getopts'
- builtin.
+ `-l'
+ List the names of all Readline functions.
-`PATH'
- A colon-separated list of directories in which the shell looks for
- commands.
+ `-p'
+ Display Readline function names and bindings in such a way
+ that they can be used as input or in a Readline
+ initialization file.
-`PS1'
- The primary prompt string. The default value is `\s-\v\$ '.
+ `-P'
+ List current Readline function names and bindings.
-`PS2'
- The secondary prompt string. The default value is `> '.
+ `-v'
+ Display Readline variable names and values in such a way that
+ they can be used as input or in a Readline initialization
+ file.
-\1f
-File: bashref.info, Node: Other Bourne Shell Features, Prev: Bourne Shell Variables, Up: Bourne Shell Features
+ `-V'
+ List current Readline variable names and values.
-Other Bourne Shell Features
-===========================
+ `-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.
-* Menu:
+ `-S'
+ Display Readline key sequences bound to macros and the
+ strings they output.
-* Major Differences From The Bourne Shell:: Major differences between
- Bash and the Bourne shell.
+ `-f FILENAME'
+ Read key bindings from FILENAME.
- 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 Bash; this section quickly details the differences of
-significance. A number of these differences are explained in greater
-depth in subsequent sections.
+ `-q FUNCTION'
+ Query about which keys invoke the named FUNCTION.
-\1f
-File: bashref.info, Node: Major Differences From The Bourne Shell, Up: Other Bourne Shell Features
+ `-u FUNCTION'
+ Unbind all keys bound to the named FUNCTION.
-Major Differences From The SVR4.2 Bourne Shell
-----------------------------------------------
+ `-r KEYSEQ'
+ Remove any current binding for KEYSEQ.
- * Bash is POSIX-conformant, even where the POSIX specification
- differs from traditional `sh' behavior.
+ `-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 multi-character invocation options (*note Invoking
- Bash::.).
+ The return status is zero unless an invalid option is supplied or
+ an error occurs.
- * Bash has command-line editing (*note Command Line Editing::.) and
- the `bind' builtin.
+`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.
- * Bash has command history (*note Bash History Facilities::.) and the
- `history' and `fc' builtins to manipulate it.
+`caller'
+ caller [EXPR]
+ Returns the context of any active subroutine call (a shell
+ function or a script executed with the `.' or `source' builtins).
- * Bash implements `csh'-like history expansion (*note History
- Interaction::.).
+ 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.
- * 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 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.
- * The `$'...'' quoting syntax, which expands ANSI-C
- backslash-escaped characters in the text between the single quotes,
- is supported (*note ANSI-C Quoting::.).
+`command'
+ command [-pVv] COMMAND [ARGUMENTS ...]
+ Runs COMMAND with ARGUMENTS ignoring any shell function named
+ COMMAND. Only shell builtin commands or commands found by
+ searching the `PATH' are executed. If there is a shell function
+ named `ls', running `command ls' within the function will execute
+ the external command `ls' instead of calling the function
+ recursively. The `-p' option means to use a default value for
+ `PATH' that is guaranteed to find all of the standard utilities.
+ The return status in this case is 127 if COMMAND cannot be found
+ or an error occurred, and the exit status of COMMAND otherwise.
- * Bash supports the `$"..."' 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::.).
+ 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 has the `time' reserved word and command timing (*note
- Pipelines::.). The display of the timing statistics may be
- controlled with the `TIMEFORMAT' variable.
+ Declare variables and give them attributes. If no NAMEs are
+ given, then display the values of variables instead.
- * Bash includes the `select' compound command, which allows the
- generation of simple menus (*note Conditional Constructs::.).
+ The `-p' option will display the attributes and values of each
+ NAME. When `-p' is used with NAME arguments, additional options
+ are ignored.
- * Bash includes the `[[' compound command, which makes conditional
- testing part of the shell grammar (*note Conditional
- Constructs::.).
+ 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.
- * Bash includes brace expansion (*note Brace Expansion::.) and tilde
- expansion (*note Tilde Expansion::.).
+ 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'.
- * Bash implements command aliases and the `alias' and `unalias'
- builtins (*note Aliases::.).
+ The `-g' option forces variables to be created or modified at the
+ global scope, even when \fBdeclare\fP is executed in a shell
+ function. It is ignored in all other cases.
- * Bash provides shell arithmetic, the `((' compound command (*note
- Conditional Constructs::.), and arithmetic expansion (*note Shell
- Arithmetic::.).
+ The following options can be used to restrict output to variables
+ with the specified attributes or to give variables attributes:
- * 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.
+ `-a'
+ Each NAME is an indexed array variable (*note Arrays::).
- * Bash includes the POSIX pattern removal `%', `#', `%%' and `##'
- expansions to remove leading or trailing substrings from variable
- values (*note Shell Parameter Expansion::.).
+ `-A'
+ Each NAME is an associative array variable (*note Arrays::).
- * The expansion `${#xx}', which returns the length of `${xx}', is
- supported (*note Shell Parameter Expansion::.).
+ `-f'
+ Use function names only.
- * The expansion `${var:'OFFSET`[:'LENGTH`]}', which expands to the
- substring of `var''s value of length LENGTH, beginning at OFFSET,
- is present (*note Shell Parameter Expansion::.).
+ `-i'
+ The variable is to be treated as an integer; arithmetic
+ evaluation (*note Shell Arithmetic::) is performed when the
+ variable is assigned a value.
- * The expansion `${var/[/]'PATTERN`[/'REPLACEMENT`]}', which matches
- PATTERN and replaces it with REPLACEMENT in the value of `var', is
- available (*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.
- * Bash has INDIRECT variable expansion using `${!word}' (*note Shell
- Parameter Expansion::.).
+ `-r'
+ Make NAMEs readonly. These names cannot then be assigned
+ values by subsequent assignment statements or unset.
- * Bash can expand positional parameters beyond `$9' using `${NUM}'.
+ `-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.
- * 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).
+ `-u'
+ When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
+ attribute is disabled.
- * Bash has process substitution (*note Process Substitution::.).
+ `-x'
+ Mark each NAME for export to subsequent commands via the
+ environment.
- * 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.
+ 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, unless the `-g' option is used. If a variable name is
+ followed by =VALUE, the value of the variable is set to VALUE.
- * 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.
+ 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 implements the full set of POSIX.2 filename expansion
- operators, including CHARACTER CLASSES, EQUIVALENCE CLASSES, and
- COLLATING SYMBOLS (*note Filename 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 implements extended pattern matching features when the
- `extglob' shell option is enabled (*note Pattern Matching::.).
+ `echo' interprets the following escape sequences:
+ `\a'
+ alert (bell)
- * It is possible to have a variable and a function with the same
- name; `sh' does not separate the two name spaces.
+ `\b'
+ backspace
- * Bash functions are permitted to have local variables using the
- `local' builtin, and thus useful recursive functions may be
- written.
+ `\c'
+ suppress further output
- * 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.
+ `\e'
+ `\E'
+ escape
- * Bash performs filename expansion on filenames specified as operands
- to input and output redirection operators.
+ `\f'
+ form feed
- * 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::.).
+ `\n'
+ new line
- * 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'.
+ `\r'
+ carriage return
- * The Bash `cd' and `pwd' builtins (*note Bourne Shell Builtins::.)
- each take `-L' and `-P' builtins to switch between logical and
- physical modes.
+ `\t'
+ horizontal tab
- * 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::.).
+ `\v'
+ vertical tab
- * The `command' builtin allows selective disabling of functions when
- command lookup is performed (*note Bash Builtins::.).
+ `\\'
+ backslash
- * Individual builtins may be enabled or disabled using the `enable'
- builtin (*note Bash Builtins::.).
+ `\0NNN'
+ the eight-bit character whose value is the octal value NNN
+ (zero to three octal digits)
- * 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::.).
+ `\xHH'
+ the eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits)
- * Shell functions may be exported to children via the environment
- using `export -f' (*note Shell Functions::.).
+ `\uHHHH'
+ the Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHH (one to four hex digits)
- * 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.
+ `\UHHHHHHHH'
+ the Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHHHHHH (one to eight hex digits)
- * 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::.).
+`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'.
- * Bash includes a `help' builtin for quick reference to shell
- facilities (*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 `printf' builtin is available to display formatted output
- (*note Bash Builtins::.).
+ 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'.
- * 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.
+ 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::).
- * The `return' builtin may be used to abort execution of scripts
- executed with the `.' or `source' builtins (*note Bourne Shell
- 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.
- * Bash includes the `shopt' builtin, for finer control of shell
- optional capabilities (*note Bash Builtins::.).
+`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 has much more optional behavior controllable with the `set'
- builtin (*note The Set Builtin::.).
+ Options, if supplied, have the following meanings:
- * 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.
+ `-d'
+ Display a short description of each 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.
+ `-m'
+ Display the description of each PATTERN in a manpage-like
+ format
- * The Bash `type' builtin is more extensive and gives more
- information about the names it finds (*note Bash Builtins::.).
+ `-s'
+ Display only a short usage synopsis for each PATTERN
- * 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::.).
+ The return status is zero unless no command matches PATTERN.
- * 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.
+`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.
- * Bash interprets special backslash-escaped characters in the prompt
- strings when interactive (*note Printing a Prompt::.).
+`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 restricted mode is more useful (*note The Restricted
- Shell::.); the SVR4.2 shell restricted mode is too limited.
+`logout'
+ logout [N]
+ Exit a login shell, returning a status of N to the shell's parent.
- * 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'.
+`mapfile'
+ mapfile [-n COUNT] [-O ORIGIN] [-s COUNT] [-t] [-u FD] [
+ -C CALLBACK] [-c QUANTUM] [ARRAY]
+ Read lines from the standard input into the indexed 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.
- * The SVR4.2 shell has two privilege-related builtins (`mldmode' and
- `priv') not present in Bash.
+ `-O'
+ Begin assigning to ARRAY at index ORIGIN. The default index
+ is 0.
- * Bash does not have the `stop' or `newgrp' builtins.
+ `-s'
+ Discard the first COUNT lines read.
- * Bash does not use the `SHACCT' variable or perform shell
- accounting.
+ `-t'
+ Remove a trailing newline from each line read.
- * The SVR4.2 `sh' uses a `TIMEOUT' variable like Bash uses `TMOUT'.
-
-More features unique to Bash may be found in *Note Bash Features::.
-
-Implementation Differences From The SVR4.2 Shell
-------------------------------------------------
+ `-u'
+ Read lines from file descriptor FD instead of the standard
+ input.
- Since Bash is a completely new implementation, it does not suffer
-from many of the limitations of the SVR4.2 shell. For instance:
+ `-C'
+ Evaluate CALLBACK each time QUANTUMP lines are read. The
+ `-c' option specifies QUANTUM.
- * Bash does not fork a subshell when redirecting into or out of a
- shell control structure such as an `if' or `while' statement.
+ `-c'
+ Specify the number of lines read between each call to
+ CALLBACK.
- * 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.
+ If `-C' is specified without `-c', the default quantum is 5000.
+ When CALLBACK is evaluated, it is supplied the index of the next
+ array element to be assigned and the line to be assigned to that
+ element as additional arguments. CALLBACK is evaluated after the
+ line is read but before the array element is assigned.
- * 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.
+ If not supplied with an explicit origin, `mapfile' will clear ARRAY
+ before assigning to it.
- * 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.
+ `mapfile' returns successfully unless an invalid option or option
+ argument is supplied, ARRAY is invalid or unassignable, or ARRAY
+ is not an indexed array.
- * The SVR4.2 shell does not allow users to trap `SIGSEGV',
- `SIGALRM', or `SIGCHLD'.
+`printf'
+ printf [-v VAR] FORMAT [ARGUMENTS]
+ Write the formatted ARGUMENTS to the standard output under the
+ control of the FORMAT. The `-v' option causes the output to be
+ assigned to the variable VAR rather than being printed to the
+ standard output.
+
+ 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, `printf' interprets the
+ following extensions:
+
+ `%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).
+
+ `%q'
+ causes `printf' to output the corresponding ARGUMENT in a
+ format that can be reused as shell input.
+
+ `%(DATEFMT)T'
+ causes `printf' to output the date-time string resulting from
+ using DATEFMT as a format string for `strftime'(3). The
+ corresponding ARGUMENT is an integer representing the number
+ of seconds since the epoch. Two special argument values may
+ be used: -1 represents the current time, and -2 represents
+ the time the shell was invoked.
+
+ Arguments to non-string format specifiers are treated as C
+ language constants, except that a leading plus or minus sign is
+ allowed, and if the leading character is a single or double quote,
+ the value is the ASCII value of the following character.
- * The SVR4.2 shell does not allow the `IFS', `MAILCHECK', `PATH',
- `PS1', or `PS2' variables to be unset.
+ 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 shell treats `^' as the undocumented equivalent of `|'.
+`read'
+ read [-ers] [-a ANAME] [-d DELIM] [-i TEXT] [-n NCHARS] [-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:
- * 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 `-'.
+ `-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.
- * 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.
+ `-d DELIM'
+ The first character of DELIM is used to terminate the input
+ line, rather than newline.
- * The SVR4.2 shell behaves differently when invoked as `jsh' (it
- turns on job control).
+ `-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.
+
+ `-i TEXT'
+ If Readline is being used to read the line, TEXT is placed
+ into the editing buffer before editing begins.
+
+ `-n NCHARS'
+ `read' returns after reading NCHARS characters rather than
+ waiting for a complete line of input, but honor a delimiter
+ if fewer than NCHARS characters are read before the delimiter.
+
+ `-N NCHARS'
+ `read' returns after reading exactly NCHARS characters rather
+ than waiting for a complete line of input, unless EOF is
+ encountered or `read' times out. Delimiter characters
+ encountered in the input are not treated specially and do not
+ cause `read' to return until NCHARS characters are read.
-\1f
-File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Bourne Shell Features, Up: Top
+ `-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 Features
-*************
+ `-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.
- This section describes features unique to Bash.
+ `-s'
+ Silent mode. If input is coming from a terminal, characters
+ are not echoed.
-* Menu:
+ `-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.
-* 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.
-* 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.
+ `-u FD'
+ Read input from file descriptor FD.
-\1f
-File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
-Invoking Bash
-=============
+`readarray'
+ readarray [-n COUNT] [-O ORIGIN] [-s COUNT] [-t] [-u FD] [
+ -C CALLBACK] [-c QUANTUM] [ARRAY]
+ Read lines from the standard input into the indexed array variable
+ ARRAY, or from file descriptor FD if the `-u' option is supplied.
- 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 ...]
+ A synonym for `mapfile'.
- 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.
+`source'
+ source FILENAME
+ A synonym for `.' (*note Bourne Shell Builtins::).
-`--dump-po-strings'
- Equivalent to `-D', but the output is in the GNU `gettext' PO
- (portable object) file format.
+`type'
+ type [-afptP] [NAME ...]
+ For each NAME, indicate how it would be interpreted if used as a
+ command name.
-`--dump-strings'
- Equivalent to `-D'.
+ 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.
-`--help'
- Display a usage message on standard output and exit sucessfully.
+ 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'.
-`--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'. `exec bash --login' will replace the
- current shell with a Bash login shell.
+ The `-P' option forces a path search for each NAME, even if `-t'
+ would not return `file'.
-`--noediting'
- Do not use the GNU Readline library (*note Command Line Editing::.)
- to read interactive command lines.
+ If a command is hashed, `-p' and `-P' print the hashed value, not
+ necessarily the file that appears first in `$PATH'.
-`--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.
+ 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.
-`--norc'
- Don't read the `~/.bashrc' initialization file in an interactive
- shell. This is on by default if the shell is invoked as `sh'.
+ If the `-f' option is used, `type' does not attempt to find shell
+ functions, as with the `command' builtin.
-`--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.
+ The return status is zero if all of the NAMES are found, non-zero
+ if any are not found.
-`--rcfile FILENAME'
- Execute commands from FILENAME (instead of `~/.bashrc') in an
- interactive shell.
+`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.
-`--restricted'
- Make the shell a restricted shell (*note The Restricted Shell::.).
+`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.
-`--verbose'
- Equivalent to `-v'.
+ `-H'
+ Change and report the hard limit associated with a resource.
-`--version'
- Show version information for this instance of Bash on the standard
- output and exit successfully.
+ `-a'
+ All current limits are reported.
- There are several single-character options that may be supplied at
-invocation which are not available with the `set' builtin.
+ `-b'
+ The maximum socket buffer size.
-`-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 `$0'.
+ `-c'
+ The maximum size of core files created.
-`-i'
- Force the shell to run interactively.
+ `-d'
+ The maximum size of a process's data segment.
-`-r'
- Make the shell a restricted shell (*note The Restricted Shell::.).
+ `-e'
+ The maximum scheduling priority ("nice").
-`-s'
- If this option is present, or if no arguments remain after option
- processing, then commands are read from the standard input. This
- option allows the positional parameters to be set when invoking an
- interactive shell.
+ `-f'
+ The maximum size of files written by the shell and its
+ children.
-`-D'
- A list of all double-quoted strings preceded by `$' 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.
+ `-i'
+ The maximum number of pending signals.
-`--'
- A `--' signals the end of options and disables further option
- processing. Any arguments after the `--' are treated as filenames
- and arguments.
+ `-l'
+ The maximum size that may be locked into memory.
- 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.
+ `-m'
+ The maximum resident set size (many systems do not honor this
+ limit).
- 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.
+ `-n'
+ The maximum number of open file descriptors (most systems do
+ not allow this value to be set).
-\1f
-File: bashref.info, Node: Bash Startup Files, Next: Is This Shell Interactive?, Prev: Invoking Bash, Up: Bash Features
+ `-p'
+ The pipe buffer size.
-Bash Startup Files
-==================
+ `-q'
+ The maximum number of bytes in POSIX message queues.
- 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::.).
+ `-r'
+ The maximum real-time scheduling priority.
- 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.
+ `-s'
+ The maximum stack size.
- When a login shell exits, Bash reads and executes commands from the
-file `~/.bash_logout', if it exists.
+ `-t'
+ The maximum amount of cpu time in seconds.
- 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'.
+ `-u'
+ The maximum number of processes available to a single user.
- So, typically, your `~/.bash_profile' contains the line
- `if [ -f `~/.bashrc' ]; then . `~/.bashrc'; fi'
+ `-v'
+ The maximum amount of virtual memory available to the shell,
+ and, on some systems, to its children.
-after (or before) any login-specific initializations.
+ `-x'
+ The maximum number of file locks.
- 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'
+ `-T'
+ The maximum number of threads.
-but the value of the `PATH' variable is not used to search for the file
-name.
- 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.
+ 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.
- When invoked as an interactive 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.
+ The return status is zero unless an invalid option or argument is
+ supplied, or an error occurs while setting a new limit.
- When invoked as `sh', Bash enters POSIX mode after the startup files
-are read.
+`unalias'
+ unalias [-a] [NAME ... ]
- 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.
+ Remove each NAME from the list of aliases. If `-a' is supplied,
+ all aliases are removed. Aliases are described in *note Aliases::.
- 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.
\1f
-File: bashref.info, Node: Is This Shell Interactive?, Next: Bash Builtins, Prev: Bash Startup Files, Up: Bash Features
-
-Is This Shell Interactive?
-==========================
+File: bashref.info, Node: Modifying Shell Behavior, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
- 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.
-
- To determine within a startup script whether Bash is running
-interactively or not, examine the variable `$PS1'; it is unset in
-non-interactive shells, and set in interactive shells. Thus:
-
- if [ -z "$PS1" ]; then
- echo This shell is not interactive
- else
- echo This shell is interactive
- fi
+4.3 Modifying Shell Behavior
+============================
- Alternatively, startup scripts may test the value of the `-' special
-parameter. It contains `i' when the shell is interactive. For example:
+* Menu:
- case "$-" in
- *i*) echo This shell is interactive ;;
- *) echo This shell is not interactive ;;
- esac
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
\1f
-File: bashref.info, Node: Bash Builtins, Next: The Set Builtin, Prev: Is This Shell Interactive?, Up: Bash Features
+File: bashref.info, Node: The Set Builtin, Next: The Shopt Builtin, Up: Modifying Shell Behavior
-Bash Builtin Commands
-=====================
+4.3.1 The Set Builtin
+---------------------
- This section describes builtin commands which are unique to or have
-been extended in Bash.
+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.
-`bind'
- bind [-m KEYMAP] [-lpsvPSV]
- bind [-m KEYMAP] [-q FUNCTION] [-u FUNCTION] [-r KEYSEQ]
- bind [-m KEYMAP] -f FILENAME
- bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
+`set'
+ set [--abefhkmnptuvxBCEHPT] [-o OPTION-NAME] [ARGUMENT ...]
+ set [+abefhkmnptuvxBCEHPT] [+o OPTION-NAME] [ARGUMENT ...]
- 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:
+ 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.
- `-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'.
+ When options are supplied, they set or unset shell attributes.
+ Options, if specified, have the following meanings:
- `-l'
- List the names of all Readline functions.
+ `-a'
+ Mark variables and function which are modified or created for
+ export to the environment of subsequent commands.
- `-p'
- Display Readline function names and bindings in such a way
- that they can be re-read.
+ `-b'
+ Cause the status of terminated background jobs to be reported
+ immediately, rather than before printing the next primary
+ prompt.
- `-P'
- List current Readline function names and bindings.
+ `-e'
+ Exit immediately if a pipeline (*note Pipelines::), which may
+ consist of a single simple command (*note Simple Commands::),
+ a subshell command enclosed in parentheses (*note Command
+ Grouping::), or one of the commands executed as part of a
+ command list enclosed by braces (*note Command Grouping::)
+ returns a non-zero status. The shell does not exit if 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 any command executed in a `&&' or
+ `||' list except the command following the final `&&' or `||',
+ any command in a pipeline but the last, or if the command's
+ return status is being inverted with `!'. A trap on `ERR',
+ if set, is executed before the shell exits.
+
+ This option applies to the shell environment and each
+ subshell environment separately (*note Command Execution
+ Environment::), and may cause subshells to exit before
+ executing all the commands in the subshell.
- `-v'
- Display Readline variable names and values in such a way that
- they can be re-read.
+ `-f'
+ Disable filename expansion (globbing).
- `-V'
- List current Readline variable names and values.
+ `-h'
+ Locate and remember (hash) commands as they are looked up for
+ execution. This option is enabled by default.
- `-s'
- Display Readline key sequences bound to macros and the
- strings they output in such a way that they can be re-read.
+ `-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.
- `-S'
- Display Readline key sequences bound to macros and the
- strings they output.
+ `-m'
+ Job control is enabled (*note Job Control::).
- `-f FILENAME'
- Read key bindings from FILENAME.
+ `-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.
- `-q FUNCTION'
- Query about which keys invoke the named FUNCTION.
+ `-o OPTION-NAME'
+ Set the option corresponding to OPTION-NAME:
- `-u FUNCTION'
- Unbind all keys bound to the named FUNCTION.
+ `allexport'
+ Same as `-a'.
- `-r KEYSEQ'
- Remove any current binding for KEYSEQ.
+ `braceexpand'
+ Same as `-B'.
- The return status is zero unless an invalid option is supplied or
- an error occurs.
+ `emacs'
+ Use an `emacs'-style line editing interface (*note
+ Command Line Editing::). This also affects the editing
+ interface used for `read -e'.
-`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.
+ `errexit'
+ Same as `-e'.
-`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.
+ `errtrace'
+ Same as `-E'.
- 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.
+ `functrace'
+ Same as `-T'.
-`declare'
- declare [-afFrxi] [-p] [NAME[=VALUE]]
+ `hashall'
+ Same as `-h'.
- Declare variables and give them attributes. If no NAMEs are
- given, then display the values of variables instead.
+ `histexpand'
+ Same as `-H'.
- 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:
+ `history'
+ Enable command history, as described in *note Bash
+ History Facilities::. This option is on by default in
+ interactive shells.
- `-a'
- Each NAME is an array variable (*note Arrays::.).
+ `ignoreeof'
+ An interactive shell will not exit upon reading EOF.
- `-f'
- Use function names only.
+ `keyword'
+ Same as `-k'.
- `-i'
- The variable is to be treated as an integer; arithmetic
- evaluation (*note Shell Arithmetic::.) is performed when the
- variable is assigned a value.
+ `monitor'
+ Same as `-m'.
- `-r'
- Make NAMEs readonly. These names cannot then be assigned
- values by subsequent assignment statements or unset.
+ `noclobber'
+ Same as `-C'.
- `-x'
- Mark each NAME for export to subsequent commands via the
- environment.
+ `noexec'
+ Same as `-n'.
- Using `+' instead of `-' turns off the attribute instead. When
- used in a function, `declare' makes each NAME local, as with the
- `local' command.
+ `noglob'
+ Same as `-f'.
- 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'.
+ `nolog'
+ Currently ignored.
-`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. `echo' interprets the following escape sequences:
- `\a'
- alert (bell)
+ `notify'
+ Same as `-b'.
- `\b'
- backspace
+ `nounset'
+ Same as `-u'.
- `\c'
- suppress trailing newline
+ `onecmd'
+ Same as `-t'.
- `\e'
- escape
+ `physical'
+ Same as `-P'.
- `\f'
- form feed
+ `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.
- `\n'
- new line
+ `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.
- `\r'
- carriage return
+ `privileged'
+ Same as `-p'.
- `\t'
- horizontal tab
+ `verbose'
+ Same as `-v'.
- `\v'
- vertical tab
+ `vi'
+ Use a `vi'-style line editing interface. This also
+ affects the editing interface used for `read -e'.
- `\\'
- backslash
+ `xtrace'
+ Same as `-x'.
- `\NNN'
- the character whose `ASCII' code is the octal value NNN (one
- to three digits)
+ `-p'
+ Turn on privileged mode. In this mode, the `$BASH_ENV' and
+ `$ENV' files are not processed, shell functions are not
+ inherited from the environment, and the `SHELLOPTS',
+ `BASHOPTS', `CDPATH' and `GLOBIGNORE' variables, if they
+ appear in the environment, are ignored. If the shell is
+ started with the effective user (group) id not equal to the
+ real user (group) id, and the `-p' option is not supplied,
+ these actions are taken and the effective user id is set to
+ the real user id. If the `-p' option is supplied at startup,
+ the effective user id is not reset. Turning this option off
+ causes the effective user and group ids to be set to the real
+ user and group ids.
- `\xNNN'
- the character whose `ASCII' code is the hexadecimal value NNN
- (one to three digits)
+ `-t'
+ Exit after reading and executing one command.
-`enable'
- enable [-n] [-p] [-f FILENAME] [-ads] [NAME ...]
- Enable and disable builtin shell commands. Disabling a builtin
- allows a disk command which has the same name as a shell builtin
- to be executed with specifying a full pathname, even though the
- shell normally searches for builtins before disk commands. If
- `-n' is used, the NAMEs become disabled. Otherwise NAMEs are
- enabled. For example, to use the `test' binary found via `$PATH'
- instead of the shell builtin version, type `enable -n test'.
+ `-u'
+ Treat unset variables and parameters other than the special
+ parameters `@' or `*' as an error when performing parameter
+ expansion. An error message will be written to the standard
+ error, and a non-interactive shell will exit.
- 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.
+ `-v'
+ Print shell input lines as they are read.
- 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'.
+ `-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.
- 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.
+ `-B'
+ The shell will perform brace expansion (*note Brace
+ Expansion::). This option is on by default.
- 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.
+ `-C'
+ Prevent output redirection using `>', `>&', and `<>' from
+ overwriting existing files.
-`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. The return
- status is zero unless no command matches PATTERN.
+ `-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.
-`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.
+ `-H'
+ Enable `!' style history substitution (*note History
+ Interaction::). This option is on by default for interactive
+ shells.
-`local'
- local NAME[=VALUE]
- For each argument, a local variable named NAME is created, and
- assigned 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. The return status is zero unless
- `local' is used outside a function or an invalid NAME is supplied.
+ `-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.
-`logout'
- logout [N]
- Exit a login shell, returning a status of N to the shell's parent.
+ For example, if `/usr/sys' is a symbolic link to
+ `/usr/local/sys' then:
+ $ cd /usr/sys; echo $PWD
+ /usr/sys
+ $ cd ..; pwd
+ /usr
-`printf'
- `printf' 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, and `%q' causes `printf' to output
- the corresponding ARGUMENT in a format that can be reused as shell
- input.
+ If `set -P' is on, then:
+ $ cd /usr/sys; echo $PWD
+ /usr/local/sys
+ $ cd ..; pwd
+ /usr/local
- 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.
+ `-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.
-`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 and their intervening separators
- assigned to the last NAME. If there are fewer words read from the
- standard input 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. 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:
+ `--'
+ 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
+ `-'.
- `-r'
- If this option is given, a backslash-newline pair is not
- ignored, and the backslash is considered to be part of the
- line.
+ `-'
+ 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.
- `-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.
+ 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 `$-'.
- `-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.
+ The remaining N ARGUMENTS are positional parameters and are
+ assigned, in order, to `$1', `$2', ... `$N'. The special
+ parameter `#' is set to N.
- `-e'
- Readline (*note Command Line Editing::.) is used to obtain
- the line.
+ The return status is always zero unless an invalid option is
+ supplied.
+
+\1f
+File: bashref.info, Node: The Shopt Builtin, Prev: The Set Builtin, Up: Modifying Shell Behavior
+
+4.3.2 The Shopt Builtin
+-----------------------
+
+This builtin allows you to change additional shell optional behavior.
`shopt'
shopt [-pqsu] [-o] [OPTNAME ...]
`-o'
Restricts the values of OPTNAME to be those defined for the
- `-o' option to the `set' builtin (*note The Set Builtin::.).
+ `-o' option to the `set' builtin (*note The Set Builtin::).
If either `-s' or `-u' is used with no OPTNAME arguments, the
display is limited to those options which are set or unset,
option.
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.
+
`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
table exists before trying to execute it. If a hashed
command no longer exists, a normal path search is performed.
+ `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.
+
`checkwinsize'
If set, Bash checks the window size after each command and,
if necessary, updates the values of `LINES' and `COLUMNS'.
command in the same history entry. This allows easy
re-editing of multi-line commands.
+ `compat31'
+ If set, Bash changes its behavior to that of version 3.1 with
+ respect to quoted arguments to the conditional command's `=~'
+ operator.
+
+ `compat32'
+ If set, Bash changes its behavior to that of version 3.2 with
+ respect to locale-specific string comparison when using the
+ `[[' conditional command's `<' and `>' operators. Bash
+ versions prior to bash-4.0 use ASCII collation and strcmp(3);
+ bash-4.1 and later use the current locale's collation
+ sequence and strcoll(3).
+
+ `compat40'
+ If set, Bash changes its behavior to that of version 4.0 with
+ respect to locale-specific string comparison when using the
+ `[[' conditional command's `<' and `>' operators (see
+ previous item) and the effect of interrupting a command list.
+
+ `compat41'
+ If set, Bash, when in posix mode, treats a single quote in a
+ double-quoted parameter expansion as a special character.
+ The single quotes must match (an even number) and the
+ characters between the single quotes are considered quoted.
+ This is the behavior of POSIX mode through version 4.1. The
+ default Bash behavior remains as in previous versions.
+
+ `dirspell'
+ If set, Bash attempts spelling correction on directory names
+ during word completion if the directory name initially
+ supplied does not exist.
+
`dotglob'
If set, Bash includes filenames beginning with a `.' in the
results of filename expansion.
fails.
`expand_aliases'
- If set, aliases are expanded as described below< under Aliases
- (*note Aliases::.). This option is enabled by default for
+ If set, aliases are expanded as described below under Aliases,
+ *note Aliases::. This option is enabled by default for
interactive shells.
+ `extdebug'
+ If set, behavior intended for use by debuggers is enabled:
+
+ 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.
+
+ 2. If the command run by the `DEBUG' trap returns a
+ non-zero value, the next command is skipped and not
+ executed.
+
+ 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.
+
+ 4. `BASH_ARGC' and `BASH_ARGV' are updated as described in
+ their descriptions (*note Bash Variables::).
+
+ 5. Function tracing is enabled: command substitution,
+ shell functions, and subshells invoked with `( COMMAND
+ )' inherit the `DEBUG' and `RETURN' traps.
+
+ 6. Error tracing is enabled: command substitution, shell
+ functions, and subshells invoked with `( COMMAND )'
+ inherit the `ERR' trap.
+
`extglob'
If set, the extended pattern matching features described above
- (*note Pattern Matching::.) are enabled.
+ (*note Pattern Matching::) are enabled.
+
+ `extquote'
+ If set, `$'STRING'' and `$"STRING"' quoting is performed
+ within `${PARAMETER}' expansions enclosed in double quotes.
+ This option is enabled by default.
+
+ `failglob'
+ If set, patterns which fail to match filenames during
+ filename expansion result in an expansion error.
+
+ `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.
+
+ `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.
+
+ `gnu_errfmt'
+ If set, shell error messages are written in the standard GNU
+ error message format.
`histappend'
If set, the history list is appended to the file named by the
`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
+ being completed (*note Commands For Completion::). This
option is enabled by default.
`huponexit'
If set, Bash will send `SIGHUP' to all jobs when an
- interactive login shell exits (*note Signals::.).
+ interactive login shell exits (*note Signals::).
`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.
+ `lastpipe'
+ If set, and job control is not active, the shell runs the
+ last command of a pipeline not executed in the background in
+ the current shell environment.
+
`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.
+ `login_shell'
+ The shell sets this option if it is started as a login shell
+ (*note Invoking Bash::). The value may not be changed.
+
`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.
+ `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.
+
`nocaseglob'
If set, Bash matches filenames in a case-insensitive fashion
when performing filename expansion.
+ `nocasematch'
+ If set, Bash matches patterns in a case-insensitive fashion
+ when performing matching while executing `case' or `[['
+ conditional commands.
+
`nullglob'
If set, Bash allows filename patterns which match no files to
expand to a null string, rather than themselves.
+ `progcomp'
+ If set, the programmable completion facilities (*note
+ Programmable Completion::) are enabled. This option is
+ enabled by default.
+
`promptvars'
- If set, prompt strings undergo variable and parameter
- expansion after being expanded (*note Printing a Prompt::.).
+ 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.
+ `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.
+
`shift_verbose'
If this is set, the `shift' builtin prints an error message
when the shift count exceeds the number of positional
the directory containing the file supplied as an argument.
This option is enabled by default.
+ `xpg_echo'
+ If set, the `echo' builtin expands backslash-escape sequences
+ by default.
+
+
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.
-`source'
- source FILENAME
- A synonym for `.' (*note Bourne Shell Builtins::.).
-
-`type'
- type [-atp] [NAME ...]
- For each NAME, indicate how it would be interpreted if used as a
- command name.
-
- 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.
- 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'.
+\1f
+File: bashref.info, Node: Special Builtins, Prev: Modifying Shell Behavior, Up: Shell Builtin Commands
- 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.
+4.4 Special Builtins
+====================
- The return status is zero if any of the NAMES are found, non-zero
- if none are found.
+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:
-`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.
+ 1. Special builtins are found before shell functions during command
+ lookup.
-`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.
+ 2. If a special builtin returns an error status, a non-interactive
+ shell exits.
- `-H'
- Change and report the hard limit associated with a resource.
+ 3. Assignment statements preceding the command stay in effect in the
+ shell environment after the command completes.
- `-a'
- All current limits are reported.
+ 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::.
- `-c'
- The maximum size of core files created.
+ These are the POSIX special builtins:
+ break : . continue eval exec exit export readonly return set
+ shift trap unset
- `-d'
- The maximum size of a process's data segment.
+\1f
+File: bashref.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
- `-f'
- The maximum size of files created by the shell.
+5 Shell Variables
+*****************
- `-l'
- The maximum size that may be locked into memory.
+* Menu:
- `-m'
- The maximum resident set size.
+* Bourne Shell Variables:: Variables which Bash uses in the same way
+ as the Bourne Shell.
+* Bash Variables:: List of variables that exist in Bash.
- `-n'
- The maximum number of open file descriptors.
+ This chapter describes the shell variables that Bash uses. Bash
+automatically assigns default values to a number of variables.
- `-p'
- The pipe buffer size.
+\1f
+File: bashref.info, Node: Bourne Shell Variables, Next: Bash Variables, Up: Shell Variables
- `-s'
- The maximum stack size.
+5.1 Bourne Shell Variables
+==========================
- `-t'
- The maximum amount of cpu time in seconds.
+Bash uses certain shell variables in the same way as the Bourne shell.
+In some cases, Bash assigns a default value to the variable.
- `-u'
- The maximum number of processes available to a single user.
+`CDPATH'
+ A colon-separated list of directories used as a search path for
+ the `cd' builtin command.
- `-v'
- The maximum amount of virtual memory available to the process.
+`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::).
- 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.
+`IFS'
+ A list of characters that separate fields; used when the shell
+ splits words as part of expansion.
- The return status is zero unless an invalid option is supplied, a
- non-numeric argument other than `unlimited' is supplied as a
- LIMIT, or an error occurs while setting a new limit.
+`MAIL'
+ If this parameter is set to a filename or directory name and the
+ `MAILPATH' variable is not set, Bash informs the user of the
+ arrival of mail in the specified file or Maildir-format directory.
-\1f
-File: bashref.info, Node: The Set Builtin, Next: Bash Conditional Expressions, Prev: Bash Builtins, Up: Bash Features
+`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.
-The Set Builtin
-===============
+`OPTARG'
+ The value of the last option argument processed by the `getopts'
+ builtin.
- This builtin is so complicated that it deserves its own section.
+`OPTIND'
+ The index of the last option argument processed by the `getopts'
+ builtin.
-`set'
- set [--abefhkmnptuvxBCHP] [-o OPTION] [ARGUMENT ...]
+`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.
- 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.
+`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.
- When options are supplied, they set or unset shell attributes.
- Options, if specified, have the following meanings:
+`PS2'
+ The secondary prompt string. The default value is `> '.
- `-a'
- Mark variables which are modified or created for export.
- `-b'
- Cause the status of terminated background jobs to be reported
- immediately, rather than before printing the next primary
- prompt.
+\1f
+File: bashref.info, Node: Bash Variables, Prev: Bourne Shell Variables, Up: Shell Variables
- `-e'
- Exit immediately if a simple command (*note Simple
- Commands::.) exits with a non-zero status, unless the command
- that fails is part of an `until' or `while' loop, part of an
- `if' statement, part of a `&&' or `||' list, or if the
- command's return status is being inverted using `!'.
+5.2 Bash Variables
+==================
- `-f'
- Disable file name generation (globbing).
+These variables are set or used by Bash, but other shells do not
+normally treat them specially.
- `-h'
- Locate and remember (hash) commands as they are looked up for
- execution. This option is enabled by default.
+ A few variables used by Bash are described in different chapters:
+variables for controlling the job control facilities (*note Job Control
+Variables::).
- `-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.
+`BASH'
+ The full pathname used to execute the current instance of Bash.
- `-m'
- Job control is enabled (*note Job Control::.).
+`BASHOPTS'
+ A colon-separated list of enabled shell options. Each word in the
+ list is a valid argument for the `-s' option to the `shopt'
+ builtin command (*note The Shopt Builtin::). The options
+ appearing in `BASHOPTS' are those reported as `on' by `shopt'. 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.
+
+`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.
- `-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.
+`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::.
- `-o OPTION-NAME'
- Set the option corresponding to OPTION-NAME:
+`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 where each corresponding member of FUNCNAME was invoked.
+ `${BASH_LINENO[$i]}' is the line number in the source file
+ (`${BASH_SOURCE[$i+1]}') where `${FUNCNAME[$i]}' was called (or
+ `${BASH_LINENO[$i-1]}' if referenced within another shell
+ function). 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 where the
+ corresponding shell function names in the `FUNCNAME' array
+ variable are defined. The shell function `${FUNCNAME[$i]}' is
+ defined in the file `${BASH_SOURCE[$i]}' and called from
+ `${BASH_SOURCE[$i+1]}'
+
+`BASH_SUBSHELL'
+ Incremented by one each time a subshell or subshell environment is
+ spawned. The initial value is 0.
- `allexport'
- Same as `-a'.
+`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:
- `braceexpand'
- Same as `-B'.
+ `BASH_VERSINFO[0]'
+ The major version number (the RELEASE).
- `emacs'
- Use an `emacs'-style line editing interface (*note
- Command Line Editing::.).
+ `BASH_VERSINFO[1]'
+ The minor version number (the VERSION).
- `errexit'
- Same as `-e'.
+ `BASH_VERSINFO[2]'
+ The patch level.
- `hashall'
- Same as `-h'.
+ `BASH_VERSINFO[3]'
+ The build version.
- `histexpand'
- Same as `-H'.
+ `BASH_VERSINFO[4]'
+ The release status (e.g., BETA1).
- `history'
- Enable command history, as described in *Note Bash
- History Facilities::. This option is on by default in
- interactive shells.
+ `BASH_VERSINFO[5]'
+ The value of `MACHTYPE'.
- `ignoreeof'
- An interactive shell will not exit upon reading EOF.
- `keyword'
- Same as `-k'.
+`BASH_VERSION'
+ The version number of the current instance of Bash.
- `monitor'
- Same as `-m'.
+`BASH_XTRACEFD'
+ If set to an integer corresponding to a valid file descriptor, Bash
+ will write the trace output generated when `set -x' is enabled to
+ that file descriptor. This allows tracing output to be separated
+ from diagnostic and error messages. The file descriptor is closed
+ when `BASH_XTRACEFD' is unset or assigned a new value. Unsetting
+ `BASH_XTRACEFD' or assigning it the empty string causes the trace
+ output to be sent to the standard error. Note that setting
+ `BASH_XTRACEFD' to 2 (the standard error file descriptor) and then
+ unsetting it will result in the standard error being closed.
+
+`COLUMNS'
+ Used by the `select' 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 line is split into words as Readline
+ would split it, using `COMP_WORDBREAKS' as described above. 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::).
+
+`COPROC'
+ An array variable created to hold the file descriptors for output
+ from and input to an unnamed coprocess (*note Coprocesses::).
- `noclobber'
- Same as `-C'.
+`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.
+
+`ENV'
+ Similar to `BASH_ENV'; used when the shell is invoked in POSIX
+ Mode (*note Bash POSIX Mode::).
- `noexec'
- Same as `-n'.
+`EUID'
+ The numeric effective user id of the current user. This variable
+ is readonly.
- `noglob'
- Same as `-f'.
+`FCEDIT'
+ The editor used as a default by the `-e' option to the `fc'
+ builtin command.
- `notify'
- Same as `-b'.
+`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:~'
- `nounset'
- Same as `-u'.
+`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 (the one with the highest index) 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.
- `onecmd'
- Same as `-t'.
+ This variable can be used with `BASH_LINENO' and `BASH_SOURCE'.
+ Each element of `FUNCNAME' has corresponding elements in
+ `BASH_LINENO' and `BASH_SOURCE' to describe the call stack. For
+ instance, `${FUNCNAME[$i]}' was called from the file
+ `${BASH_SOURCE[$i+1]}' at line number `${BASH_LINENO[$i]}'. The
+ `caller' builtin displays the current call stack using this
+ information.
- `physical'
- Same as `-P'.
+`FUNCNEST'
+ If set to a numeric value greater than 0, defines a maximum
+ function nesting level. Function invocations that exceed this
+ nesting level will cause the current command to abort.
- `posix'
- Change the behavior of Bash where the default operation
- differs from the POSIX 1003.2 standard to match the
- standard (*note Bash POSIX Mode::.). This is intended
- to make Bash behave as a strict superset of that
- standard.
+`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.
- `privileged'
- Same as `-p'.
+`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.
- `verbose'
- Same as `-v'.
+`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.
- `vi'
- Use a `vi'-style line editing interface.
+`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.
- `xtrace'
- Same as `-x'.
+`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'.
- `-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' variable,
- if it appears in the environment, is ignored. 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.
+`HISTFILE'
+ The name of the file to which the command history is saved. The
+ default value is `~/.bash_history'.
- `-t'
- Exit after reading and executing one command.
-
- `-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.
-
- `-v'
- Print shell input lines as they are read.
-
- `-x'
- Print a trace of simple commands and their arguments after
- they are expanded and before they are executed.
-
- `-B'
- The shell will perform brace expansion (*note Brace
- Expansion::.). This option is on by default.
-
- `-C'
- Prevent output redirection using `>', `>&', and `<>' from
- overwriting existing files.
-
- `-H'
- Enable `!' style history substitution (*note History
- Interaction::.). This option is on by default for
- interactive shells.
-
- `-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.
-
- For example, if `/usr/sys' is a symbolic link to
- `/usr/local/sys' then:
- $ cd /usr/sys; echo $PWD
- /usr/sys
- $ cd ..; pwd
- /usr
-
- If `set -P' is on, then:
- $ cd /usr/sys; echo $PWD
- /usr/local/sys
- $ cd ..; pwd
- /usr/local
-
- `--'
- 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
- `-'.
-
- `-'
- 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.
-
- 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 `$-'.
-
- The remaining N ARGUMENTS are positional parameters and are
- assigned, in order, to `$1', `$2', ... `$N'. The special
- parameter `#' is set to N.
-
- The return status is always zero unless an invalid option is
- supplied.
-
-\1f
-File: bashref.info, Node: Bash Conditional Expressions, Next: Bash Variables, Prev: The Set Builtin, Up: Bash Features
-
-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 any FILE argument to one of
-the primaries is of the form `/dev/fd/N', then file descriptor N is
-checked.
-
-`-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.
-
-`-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.
-
-`FILE1 -ot FILE2'
- True if FILE1 is older than FILE2.
-
-`FILE1 -ef FILE2'
- True if FILE1 and FILE2 have 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 `=='.
-
-`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: Bash Variables, Next: Shell Arithmetic, Prev: Bash Conditional Expressions, Up: Bash Features
-
-Bash Variables
-==============
-
- These variables are set or used by Bash, but other shells do not
-normally treat them specially.
-
-`BASH'
- The full pathname used to execute the current instance of Bash.
-
-`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::.
-
-`BASH_VERSION'
- The version number of the current instance of Bash.
-
-`BASH_VERSINFO'
- A readonly array variable whose members hold version information
- for this instance of Bash. The values assigned to the array
- members are as follows:
-
- `BASH_VERSINFO[0]'
- The major version number (the RELEASE).
-
- `BASH_VERSINFO[1]'
- The minor version number (the VERSION).
-
- `BASH_VERSINFO[2]'
- The patch level.
-
- `BASH_VERSINFO[3]'
- The build version.
-
- `BASH_VERSINFO[4]'
- The release status (e.g., BETA1).
-
- `BASH_VERSINFO[5]'
- The value of `MACHTYPE'.
-
-`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.
-
-`EUID'
- The numeric effective user id of the current user. This variable
- is readonly.
-
-`FCEDIT'
- The editor used as a default by the `-e' option to the `fc'
- builtin command.
-
-`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:~'
-
-`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.
-
-`GROUPS'
- An array variable containing the list of groups of which the
- current user is a member. This variable is readonly.
-
-`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 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.
-
-`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.
-
-`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. 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'.
+`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.
`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
+ 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
+ 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'.
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'.
-
`HISTSIZE'
The maximum number of commands to remember on the history list.
The default value is 500.
-`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.
+`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. 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.
+ 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, or
+ does not name a readable file, 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.
in effect for interactive shells.
`INPUTRC'
- The name of the Readline startup file, overriding the default of
- `~/.inputrc'.
+ The name of the Readline initialization file, overriding the
+ default of `~/.inputrc'.
`LANG'
Used to determine the locale category for any category not
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::.).
+ 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::.).
+ matching (*note Filename Expansion::).
`LC_MESSAGES'
This variable determines the locale used to translate double-quoted
- strings preceded by a `$' (*note Locale Translation::.).
+ strings preceded by a `$' (*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' 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.
+ 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.
+
+`MAPFILE'
+ An array variable created to hold the text read by the `mapfile'
+ builtin when no variable name is supplied.
`OLDPWD'
The previous working directory as set by the `cd' builtin.
A string describing the operating system Bash is running on.
`PIPESTATUS'
- An array variable (*note Arrays::.) containing a list of exit
+ 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
+ The process ID of the shell's parent process. This variable is
readonly.
`PROMPT_COMMAND'
- If present, this contains a string which is a command to execute
- before the printing of each primary prompt (`$PS1').
+ If set, the value is interpreted as a command to execute before
+ the printing of each primary prompt (`$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'
prompts with `#? '
`PS4'
- This is the prompt printed before the command line is echoed when
- the `-x' option is set (*note The Set Builtin::.). The first
+ 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 `+ '.
and 32767 is generated. Assigning a value to this variable seeds
the random number generator.
+`READLINE_LINE'
+ The contents of the Readline line buffer, for use with `bind -x'
+ (*note Bash Builtins::).
+
+`READLINE_POINT'
+ The position of the insertion point in the Readline line buffer,
+ for use with `bind -x' (*note Bash Builtins::).
+
`REPLY'
The default variable for the `read' builtin.
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
+ 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
trailing newline is added when the format string is displayed.
`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.
+ 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: Shell Arithmetic, Next: Aliases, Prev: Bash Variables, Up: Bash Features
+File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Shell Variables, Up: Top
-Shell Arithmetic
-================
+6 Bash Features
+***************
- The shell allows arithmetic expressions to be evaluated, as one of
-the shell expansions or by the `let' builtin.
+This section describes features unique to Bash.
- 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.
+* Menu:
-`- +'
- unary minus and plus
+* 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.
-`! ~'
- logical and bitwise negation
+\1f
+File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
-`**'
- exponentiation
+6.1 Invoking Bash
+=================
-`* / %'
- multiplication, division, remainder
+ 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 ...]
-`+ -'
- addition, subtraction
+ All of the single-character options used with the `set' builtin
+(*note The Set Builtin::) can be used as options when the shell is
+invoked. In addition, 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.
-`<< >>'
- left and right bitwise shifts
+`--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).
-`<= >= < >'
- comparison
+`--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.
-`== !='
- equality and inequality
+`--dump-strings'
+ Equivalent to `-D'.
-`&'
- bitwise AND
+`--help'
+ Display a usage message on standard output and exit successfully.
-`^'
- bitwise exclusive OR
+`--init-file FILENAME'
+`--rcfile FILENAME'
+ Execute commands from FILENAME (instead of `~/.bashrc') in an
+ interactive shell.
-`|'
- bitwise OR
+`--login'
+ Equivalent to `-l'.
-`&&'
- logical AND
+`--noediting'
+ Do not use the GNU Readline library (*note Command Line Editing::)
+ to read command lines when the shell is interactive.
-`||'
- logical OR
+`--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.
-`expr ? expr : expr'
- conditional evaluation
+`--norc'
+ Don't read the `~/.bashrc' initialization file in an interactive
+ shell. This is on by default if the shell is invoked as `sh'.
-`= *= /= %= += -= <<= >>= &= ^= |='
- assignment
+`--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.
- 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.
+`--restricted'
+ Make the shell a restricted shell (*note The Restricted Shell::).
- 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.
+`--verbose'
+ Equivalent to `-v'. Print shell input lines as they're read.
- Operators are evaluated in order of precedence. Sub-expressions in
-parentheses are evaluated first and may override the precedence rules
-above.
+`--version'
+ Show version information for this instance of Bash on the standard
+ output and exit successfully.
-\1f
-File: bashref.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
-Aliases
-=======
+ There are several single-character options that may be supplied at
+invocation which are not available with the `set' builtin.
-* Menu:
+`-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'.
-* Alias Builtins:: Builtins commands to maniuplate aliases.
+`-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.
- 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.
+`-r'
+ Make the shell a restricted shell (*note The Restricted Shell::).
- 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 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.
+`-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.
- Aliases are created and listed with the `alias' command, and removed
-with the `unalias' command.
+`-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.
- 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::.).
+`[-+]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.
- Aliases are not expanded when the shell is not interactive, unless
-the `expand_aliases' shell option is set using `shopt' (*note Bash
-Builtins::.).
+`--'
+ A `--' signals the end of options and disables further option
+ processing. Any arguments after the `--' are treated as filenames
+ and arguments.
- 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, aliases are superseded by shell functions.
+ 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: Alias Builtins, Up: Aliases
+File: bashref.info, Node: Bash Startup Files, Next: Interactive Shells, Prev: Invoking Bash, Up: Bash Features
-Alias Builtins
---------------
+6.2 Bash Startup Files
+======================
-`alias'
- alias [`-p'] [NAME[=VALUE] ...]
+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::).
- 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.
+ Interactive shells are described in *note Interactive Shells::.
-`unalias'
- unalias [-a] [NAME ... ]
+Invoked as an interactive login shell, or with `--login'
+........................................................
- Remove each NAME from the list of aliases. If `-a' is supplied,
- all aliases are removed.
+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.
-\1f
-File: bashref.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
+ When a login shell exits, Bash reads and executes commands from the
+file `~/.bash_logout', if it exists.
-Arrays
-======
+Invoked as an interactive non-login shell
+.........................................
- 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.
+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'.
- An array is created automatically if any variable is assigned to
-using the syntax
- name[SUBSCRIPT]=VALUE
+ So, typically, your `~/.bash_profile' contains the line
+ `if [ -f ~/.bashrc ]; then . ~/.bashrc; fi'
+ after (or before) any login-specific initializations.
-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
+Invoked non-interactively
+.........................
-The syntax
- declare -a NAME[SUBSCRIPT]
+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 . "$BASH_ENV"; fi'
+ but the value of the `PATH' variable is not used to search for the
+file name.
-is also accepted; the SUBSCRIPT is ignored. Attributes may be
-specified for an array variable using the `declare' and `readonly'
-builtins. Each attribute applies to all members of an array.
+ As noted above, if a non-interactive shell is invoked with the
+`--login' option, Bash attempts to read and execute commands from the
+login shell startup files.
- Arrays are assigned to using compound assignments of the form
- name=(value1 ... valueN)
+Invoked with name `sh'
+......................
-where each VALUE is of the form `[[SUBSCRIPT]=]'STRING. If the
-optional subscript is supplied, that index is assigned to; otherwise
-the index of the element assigned is the last index assigned to by the
-statement plus one. Indexing starts at zero. This syntax is also
-accepted by the `declare' builtin. Individual array elements may be
-assigned to using the `name['SUBSCRIPT`]='VALUE syntax introduced above.
+If Bash is invoked with the name `sh', it tries to mimic the startup
+behavior of historical versions of `sh' as closely as possible, while
+conforming to the POSIX standard as well.
- Any element of an array may be referenced using
-`${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.
+ 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.
- 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.
+ When invoked as `sh', Bash enters POSIX mode after the startup files
+are read.
- 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.
+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 network connection, as when executed 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', `BASHOPTS', `CDPATH', and `GLOBIGNORE' variables, if
+they appear in the environment, are 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: The Directory Stack, Next: Printing a Prompt, Prev: Arrays, Up: Bash Features
+File: bashref.info, Node: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
-The Directory Stack
-===================
+6.3 Interactive Shells
+======================
- 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.
+* Menu:
- The contents of the directory stack are also visible as the value of
-the `DIRSTACK' shell variable.
+* 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?
-`dirs'
- dirs [+N | -N] [-clvp]
- 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.
+\1f
+File: bashref.info, Node: What is an Interactive Shell?, Next: Is this Shell Interactive?, Up: Interactive Shells
- `-N'
- Displays the Nth directory (counting from the right of the
- list printed by `dirs' when invoked without options), starting
- with zero.
+6.3.1 What is an Interactive Shell?
+-----------------------------------
- `-c'
- Clears the directory stack by deleting all of the elements.
+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.
- `-l'
- Produces a longer listing; the default listing format uses a
- tilde to denote the home directory.
+ An interactive shell generally reads from and writes to a user's
+terminal.
- `-p'
- Causes `dirs' to print the directory stack with one entry per
- line.
+ The `-s' invocation option may be used to set the positional
+parameters when an interactive shell is started.
- `-v'
- Causes `dirs' to print the directory stack with one entry per
- line, prefixing each entry with its index in the stack.
+\1f
+File: bashref.info, Node: Is this Shell Interactive?, Next: Interactive Shell Behavior, Prev: What is an Interactive Shell?, Up: Interactive Shells
-`popd'
- popd [+N | -N] [-n]
+6.3.2 Is this Shell Interactive?
+--------------------------------
- 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.
+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:
- `-N'
- Removes the Nth directory (counting from the right of the
- list printed by `dirs'), starting with zero.
+ case "$-" in
+ *i*) echo This shell is interactive ;;
+ *) echo This shell is not interactive ;;
+ esac
- `-n'
- Suppresses the normal change of directory when removing
- directories from the stack, so that only the stack is
- manipulated.
+ Alternatively, startup scripts may examine the variable `PS1'; it is
+unset in non-interactive shells, and set in interactive shells. Thus:
-`pushd'
- pushd [DIR | +N | -N] [-n]
+ if [ -z "$PS1" ]; then
+ echo This shell is not interactive
+ else
+ echo This shell is interactive
+ fi
- Save the current directory on the top of the directory stack and
- then `cd' to DIR. With no arguments, `pushd' exchanges the top
- two directories.
+\1f
+File: bashref.info, Node: Interactive Shell Behavior, Prev: Is this Shell Interactive?, Up: Interactive Shells
- `+N'
- Brings the Nth directory (counting from the left of the list
- printed by `dirs', starting with zero) to the top of the list
- by rotating the stack.
+6.3.3 Interactive Shell Behavior
+--------------------------------
- `-N'
- Brings the Nth directory (counting from the right of the list
- printed by `dirs', starting with zero) to the top of the list
- by rotating the stack.
+When the shell is running interactively, it changes its behavior in
+several ways.
- `-n'
- Suppresses the normal change of directory when adding
- directories to the stack, so that only the stack is
- manipulated.
+ 1. Startup files are read and executed as described in *note Bash
+ Startup Files::.
- `DIR'
- Makes the current working directory be the top of the stack,
- and then executes the equivalent of ``cd' DIR'. `cd's to DIR.
+ 2. Job Control (*note Job Control::) is enabled by default. When job
+ control is in effect, Bash ignores the keyboard-generated job
+ control signals `SIGTTIN', `SIGTTOU', and `SIGTSTP'.
-\1f
-File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
+ 3. Bash expands and displays `PS1' before reading the first line of a
+ command, and expands and displays `PS2' before reading the second
+ and subsequent lines of a multi-line command.
-Controlling the Prompt
-======================
+ 4. Bash executes the value of the `PROMPT_COMMAND' variable as a
+ command before printing the primary prompt, `$PS1' (*note Bash
+ Variables::).
- 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 it had been typed on the command line.
+ 5. Readline (*note Command Line Editing::) is used to read commands
+ from the user's terminal.
- In addition, the following table describes the special characters
-which can appear in the prompt variables:
+ 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::).
-`\a'
- A bell character.
+ 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.
-`\d'
- The date, in "Weekday Month Date" format (e.g., "Tue May 26").
+ 8. Alias expansion (*note Aliases::) is performed by default.
-`\e'
- An escape character.
+ 9. In the absence of any traps, Bash ignores `SIGTERM' (*note
+ Signals::).
-`\h'
- The hostname, up to the first `.'.
+ 10. In the absence of any traps, `SIGINT' is caught and handled
+ ((*note Signals::). `SIGINT' will interrupt some shell builtins.
-`\H'
- The hostname.
+ 11. An interactive login shell sends a `SIGHUP' to all jobs on exit if
+ the `huponexit' shell option has been enabled (*note Signals::).
-`\n'
- A newline.
+ 12. The `-n' invocation option is ignored, and `set -n' has no effect
+ (*note The Set Builtin::).
-`\r'
- A carriage return.
+ 13. Bash will check for mail periodically, depending on the values of
+ the `MAIL', `MAILPATH', and `MAILCHECK' shell variables (*note
+ Bash Variables::).
-`\s'
- The name of the shell, the basename of `$0' (the portion following
- the final slash).
+ 14. Expansion errors due to references to unbound shell variables after
+ `set -u' has been enabled will not cause the shell to exit (*note
+ The Set Builtin::).
-`\t'
- The time, in 24-hour HH:MM:SS format.
+ 15. The shell will not exit on expansion errors caused by VAR being
+ unset or null in `${VAR:?WORD}' expansions (*note Shell Parameter
+ Expansion::).
-`\T'
- The time, in 12-hour HH:MM:SS format.
+ 16. Redirection errors encountered by shell builtins will not cause the
+ shell to exit.
-`\@'
- The time, in 12-hour am/pm format.
+ 17. When running in POSIX mode, a special builtin returning an error
+ status will not cause the shell to exit (*note Bash POSIX Mode::).
-`\u'
- The username of the current user.
+ 18. A failed `exec' will not cause the shell to exit (*note Bourne
+ Shell Builtins::).
-`\v'
- The version of Bash (e.g., 2.00)
+ 19. Parser syntax errors will not cause the shell to exit.
-`\V'
- The release of Bash, version + patchlevel (e.g., 2.00.0)
+ 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::).
-`\w'
- The current working directory.
+ 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 `$PS1' (*note Bash Variables::).
-`\W'
- The basename of `$PWD'.
-`\!'
- The history number of this command.
+\1f
+File: bashref.info, Node: Bash Conditional Expressions, Next: Shell Arithmetic, Prev: Interactive Shells, Up: Bash Features
-`\#'
- The command number of this command.
+6.4 Bash Conditional Expressions
+================================
-`\$'
- If the effective uid is 0, `#', otherwise `$'.
+Conditional expressions are used by the `[[' compound command and the
+`test' and `[' builtin commands.
-`\NNN'
- The character whose ASCII code is the octal value NNN.
+ 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.
-`\\'
- A backslash.
+ When used with `[[', the `<' and `>' operators sort
+lexicographically using the current locale. The `test' command uses
+ASCII ordering.
-`\['
- Begin a sequence of non-printing characters. This could be used to
- embed a terminal control sequence into the prompt.
+ Unless otherwise specified, primaries that operate on files follow
+symbolic links and operate on the target of the link, rather than the
+link itself.
-`\]'
- End a sequence of non-printing characters.
+`-a FILE'
+ True if FILE exists.
-\1f
-File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
+`-b FILE'
+ True if FILE exists and is a block special file.
-The Restricted Shell
-====================
+`-c FILE'
+ True if FILE exists and is a character special file.
- 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.
+`-d FILE'
+ True if FILE exists and is a directory.
- * Setting or unsetting the values of the `SHELL' or `PATH' variables.
+`-e FILE'
+ True if FILE exists.
- * Specifying command names containing slashes.
+`-f FILE'
+ True if FILE exists and is a regular file.
- * Specifying a filename containing a slash as an argument to the `.'
- builtin command.
+`-g FILE'
+ True if FILE exists and its set-group-id bit is set.
- * Importing function definitions from the shell environment at
- startup.
+`-h FILE'
+ True if FILE exists and is a symbolic link.
- * Parsing the value of `SHELLOPTS' from the shell environment at
- startup.
+`-k FILE'
+ True if FILE exists and its "sticky" bit is set.
- * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
- redirection operators.
+`-p FILE'
+ True if FILE exists and is a named pipe (FIFO).
- * Using the `exec' builtin to replace the shell with another command.
+`-r FILE'
+ True if FILE exists and is readable.
- * Adding or deleting builtin commands with the `-f' and `-d' options
- to the `enable' builtin.
+`-s FILE'
+ True if FILE exists and has a size greater than zero.
- * Specifying the `-p' option to the `command' builtin.
+`-t FD'
+ True if file descriptor FD is open and refers to a terminal.
- * Turning off restricted mode with `set +r' or `set +o restricted'.
+`-u FILE'
+ True if FILE exists and its set-user-id bit is set.
-\1f
-File: bashref.info, Node: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
+`-w FILE'
+ True if FILE exists and is writable.
-Bash POSIX Mode
-===============
+`-x FILE'
+ True if FILE exists and is executable.
- 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.
+`-G FILE'
+ True if FILE exists and is owned by the effective group id.
- The following list is what's changed when `POSIX mode' is in effect:
+`-L FILE'
+ True if FILE exists and is a symbolic link.
- 1. When a command in the hash table no longer exists, Bash will
- re-search `$PATH' to find the new location. This is also
- available with `shopt -s checkhash'.
+`-N FILE'
+ True if FILE exists and has been modified since it was last read.
- 2. The `>&' redirection does not redirect stdout and stderr.
+`-O FILE'
+ True if FILE exists and is owned by the effective user id.
- 3. The message printed by the job control code and builtins when a job
- exits with a non-zero status is `Done(status)'.
+`-S FILE'
+ True if FILE exists and is a socket.
- 4. Reserved words may not be aliased.
+`FILE1 -ef FILE2'
+ True if FILE1 and FILE2 refer to the same device and inode numbers.
- 5. The POSIX.2 `PS1' and `PS2' expansions of `!' to the history
- number and `!!' to `!' are enabled, and parameter expansion is
- performed on the values of `PS1' and `PS2' regardless of the
- setting of the `promptvars' option.
+`FILE1 -nt FILE2'
+ True if FILE1 is newer (according to modification date) than
+ FILE2, or if FILE1 exists and FILE2 does not.
- 6. Interactive comments are enabled by default. (Bash has them on by
- default anyway.)
+`FILE1 -ot FILE2'
+ True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
+ does not.
- 7. The POSIX.2 startup files are executed (`$ENV') rather than the
- normal Bash files.
+`-o OPTNAME'
+ True if the 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::).
- 8. Tilde expansion is only performed on assignments preceding a
- command name, rather than on all assignment statements on the line.
+`-v VARNAME'
+ True if the shell variable VARNAME is set (has been assigned a
+ value).
- 9. The default history file is `~/.sh_history' (this is the default
- value of `$HISTFILE').
+`-z STRING'
+ True if the length of STRING is zero.
- 10. The output of `kill -l' prints all the signal names on a single
- line, separated by spaces.
+`-n STRING'
+`STRING'
+ True if the length of STRING is non-zero.
- 11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
- found.
+`STRING1 == STRING2'
+`STRING1 = STRING2'
+ True if the strings are equal. `=' should be used with the `test'
+ command for POSIX conformance.
- 12. Non-interactive shells exit if a syntax error in an arithmetic
- expansion results in an invalid expression.
+`STRING1 != STRING2'
+ True if the strings are not equal.
- 13. Redirection operators do not perform filename expansion on the word
- in the redirection unless the shell is interactive.
+`STRING1 < STRING2'
+ True if STRING1 sorts before STRING2 lexicographically.
- 14. Function names must be valid shell `name's. That is, they may not
- contain characters other than letters, digits, and underscores, and
- may not start with a digit. Declaring a function with an invalid
- name causes a fatal syntax error in non-interactive shells.
+`STRING1 > STRING2'
+ True if STRING1 sorts after STRING2 lexicographically.
- 15. POSIX.2 `special' builtins are found before shell functions during
- command lookup.
+`ARG1 OP ARG2'
+ `OP' is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These
+ arithmetic binary operators return true if ARG1 is equal to, not
+ equal to, less than, less than or equal to, greater than, or
+ greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
+ positive or negative integers.
- 16. If a POSIX.2 special builtin returns an error status, a
- non-interactive shell exits. The fatal errors are those listed in
- the POSIX.2 standard, and include things like passing incorrect
- options, redirection errors, variable assignment errors for
- assignments preceding the command name, and so on.
- 17. If the `cd' builtin finds a directory to change to using
- `$CDPATH', the value it assigns to the `PWD' variable does not
- contain any symbolic links, as if `cd -P' had been executed.
+\1f
+File: bashref.info, Node: Shell Arithmetic, Next: Aliases, Prev: Bash Conditional Expressions, Up: Bash Features
- 18. 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.
+6.5 Shell Arithmetic
+====================
- 19. 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.
+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.
- 20. 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.
+ 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.
- 21. Process substitution is not available.
+`ID++ ID--'
+ variable post-increment and post-decrement
- 22. Assignment statements preceding POSIX.2 special builtins persist
- in the shell environment after the builtin completes.
+`++ID --ID'
+ variable pre-increment and pre-decrement
- 23. The `export' and `readonly' builtin commands display their output
- in the format required by POSIX.2.
+`- +'
+ unary minus and plus
+`! ~'
+ logical and bitwise negation
- There is other POSIX.2 behavior that Bash does not implement.
-Specifically:
+`**'
+ exponentiation
- 1. Assignment statements affect the execution environment of all
- builtins, not just special ones.
+`* / %'
+ multiplication, division, remainder
-\1f
-File: bashref.info, Node: Job Control, Next: Using History Interactively, Prev: Bash Features, Up: Top
+`+ -'
+ addition, subtraction
-Job Control
-***********
+`<< >>'
+ left and right bitwise shifts
- This chapter discusses what job control is, how it works, and how
-Bash allows you to access its facilities.
+`<= >= < >'
+ comparison
-* Menu:
+`== !='
+ equality and inequality
-* 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.
+`&'
+ bitwise AND
-\1f
-File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
+`^'
+ bitwise exclusive OR
-Job Control Basics
-==================
+`|'
+ bitwise OR
- 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.
+`&&'
+ logical AND
- 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
+`||'
+ logical OR
-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.
+`expr ? expr : expr'
+ conditional operator
- 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.
+`= *= /= %= += -= <<= >>= &= ^= |='
+ assignment
- 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.
+`expr1 , expr2'
+ comma
- 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 or started in the background. 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 `-'.
+ 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.
- 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'
+ 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 the optional 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.
- 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 enabled, Bash
-reports such changes immediately (*note The Set Builtin::.).
-
- If an attempt to exit Bash is while jobs are stopped, the shell
-prints a message warning that there are stopped jobs. 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 the stopped jobs are terminated.
+ 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: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
+File: bashref.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
-Job Control Builtins
-====================
+6.6 Aliases
+===========
-`bg'
- bg [JOBSPEC]
- Resume the 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, if
- JOBSPEC was not found or JOBSPEC specifies a job that was started
- without job control.
+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.
-`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.
+ 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.
-`jobs'
- jobs [-lpnrs] [JOBSPEC]
- jobs -x COMMAND [ARGUMENTS]
+ Aliases are created and listed with the `alias' command, and removed
+with the `unalias' command.
- The first form lists the active jobs. The options have the
- following meanings:
+ 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::).
- `-l'
- List process IDs in addition to the normal information.
+ Aliases are not expanded when the shell is not interactive, unless
+the `expand_aliases' shell option is set using `shopt' (*note The Shopt
+Builtin::).
- `-n'
- Display information only about jobs that have changed status
- since the user was last notified of their status.
+ 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.
- `-p'
- List only the process ID of the job's process group leader.
+ For almost every purpose, shell functions are preferred over aliases.
- `-r'
- Restrict output to running jobs.
+\1f
+File: bashref.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
- `-s'
- Restrict output to stopped jobs.
+6.7 Arrays
+==========
- 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 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.
- 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.
+ An indexed array is created automatically if any variable is
+assigned to using the syntax
+ name[SUBSCRIPT]=VALUE
-`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 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.
+The SUBSCRIPT is treated as an arithmetic expression that must evaluate
+to a number. If SUBSCRIPT evaluates to a number less than zero, it is
+used as an offset from one greater than the array's maximum index (so a
+subcript of -1 refers to the last element of the array). To explicitly
+declare an array, use
+ declare -a NAME
+ The syntax
+ declare -a NAME[SUBSCRIPT]
+ is also accepted; the SUBSCRIPT is ignored.
-`wait'
- wait [JOBSPEC|PID]
- Wait until the child process specified by 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.
+ Associative arrays are created using
+ declare -A NAME.
-`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.
+ Attributes may be specified for an array variable using the
+`declare' and `readonly' builtins. Each attribute applies to all
+members of an array.
-`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.
+ 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.
- When job control is not active, the `kill' and `wait' builtins do
-not accept JOBSPEC arguments. They must be supplied process IDs.
+ When assigning to an associative array, the subscript is required.
-\1f
-File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
+ This syntax is also accepted by the `declare' builtin. Individual
+array elements may be assigned to using the `name['SUBSCRIPT`]='VALUE
+syntax introduced above.
-Job Control Variables
-=====================
+ 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.
+
+ An array variable is considered set if a subscript has been assigned
+a value. The null string is a valid value.
-`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.
+ 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
+expansion. `unset' NAME, where NAME is an array, removes the entire
+array. A subscript of `*' or `@' also removes the entire array.
-\1f
-File: bashref.info, Node: Using History Interactively, Next: Command Line Editing, Prev: Job Control, Up: Top
+ 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.
-Using History Interactively
-***************************
+\1f
+File: bashref.info, Node: The Directory Stack, Next: Printing a Prompt, Prev: Arrays, Up: Bash Features
- 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.
+6.8 The Directory Stack
+=======================
* 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
+* Directory Stack Builtins:: Bash builtin commands to manipulate
+ the directory stack.
-Bash History Facilities
-=======================
+ 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.
- 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 contents of the directory stack are also visible as the value of
+the `DIRSTACK' shell variable.
- The builtin command `fc' may be used to list or edit and re-execute
-a portion of the history list. The `history' builtin 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.
+\1f
+File: bashref.info, Node: Directory Stack Builtins, Up: The Directory Stack
- 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'.
+6.8.1 Directory Stack Builtins
+------------------------------
-\1f
-File: bashref.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
+`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.
-Bash History Builtins
-=====================
+ `-N'
+ Displays the Nth directory (counting from the right of the
+ list printed by `dirs' when invoked without options), starting
+ with zero.
- Bash provides two builtin commands that allow you to manipulate the
-history list and history file.
+ `-c'
+ Clears the directory stack by deleting all of the elements.
-`fc'
- `fc [-e ENAME] [-nlr] [FIRST] [LAST]'
- `fc -s [PAT=REP] [COMMAND]'
+ `-l'
+ Produces a longer listing; the default listing format uses a
+ tilde to denote the home directory.
- 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.
+ `-p'
+ Causes `dirs' to print the directory stack with one entry per
+ line.
- In the second form, COMMAND is re-executed after each instance of
- PAT in the selected command is replaced by REP.
+ `-v'
+ Causes `dirs' to print the directory stack with one entry per
+ line, prefixing each entry with its index in the stack.
- 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::.).
+`popd'
+ popd [+N | -N] [-n]
-`history'
- history [-c] [N]
- history [-anrw] [FILENAME]
- history -ps ARG
+ 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.
- 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:
+ `-N'
+ Removes the Nth directory (counting from the right of the
+ list printed by `dirs'), starting with zero.
- `-w'
- Write out the current history to the history file.
+ `-n'
+ Suppresses the normal change of directory when removing
+ directories from the stack, so that only the stack is
+ manipulated.
- `-r'
- Read the current history file and append its contents to the
- history list.
+`pushd'
+ pushd [-n] [+N | -N | DIR ]
- `-a'
- Append the new history lines (history lines entered since the
- beginning of the current Bash session) to the history file.
+ 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.
`-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.
+ Suppresses the normal change of directory when adding
+ directories to the stack, so that only the stack is
+ manipulated.
- `-c'
- Clear the history list. This may be combined with the other
- options to replace the history list completely.
+ `+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.
- `-s'
- The ARGs are added to the end of the history list as a single
- entry.
+ `-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.
- `-p'
- Perform history substitution on the ARGs and display the
- result on the standard output, without storing the results in
- the history list.
+ `DIR'
+ Makes the current working directory be the top of the stack,
+ and then executes the equivalent of ``cd' DIR'. `cd's to DIR.
- 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.
\1f
-File: bashref.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
+File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
-History Expansion
-=================
+6.9 Controlling the Prompt
+==========================
- 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.
+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.
- 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.
+ In addition, the following table describes the special characters
+which can appear in the prompt variables:
- 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.
+`\a'
+ A bell character.
- 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.
+`\d'
+ The date, in "Weekday Month Date" format (e.g., "Tue May 26").
- The shell allows control of the various characters used by the
-history expansion mechanism with the `histchars' variable.
+`\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.
-* Menu:
+`\e'
+ An escape character.
-* Event Designators:: How to specify which history line to use.
-* Word Designators:: Specifying which words are of interest.
-* Modifiers:: Modifying the results of substitution.
+`\h'
+ The hostname, up to the first `.'.
-\1f
-File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
+`\H'
+ The hostname.
-Event Designators
------------------
+`\j'
+ The number of jobs currently managed by the shell.
- An event designator is a reference to a command line entry in the
-history list.
+`\l'
+ The basename of the shell's terminal device name.
-`!'
- Start a history substitution, except when followed by a space, tab,
- the end of the line, `=' or `('.
+`\n'
+ A newline.
-`!N'
- Refer to command line N.
+`\r'
+ A carriage return.
-`!-N'
- Refer to the command N lines back.
+`\s'
+ The name of the shell, the basename of `$0' (the portion following
+ the final slash).
-`!!'
- Refer to the previous command. This is a synonym for `!-1'.
+`\t'
+ The time, in 24-hour HH:MM:SS format.
-`!STRING'
- Refer to the most recent command starting with STRING.
+`\T'
+ The time, in 12-hour HH:MM:SS format.
-`!?STRING[?]'
- Refer to the most recent command containing STRING. The trailing
- `?' may be omitted if the STRING is followed immediately by a
- newline.
+`\@'
+ The time, in 12-hour am/pm format.
-`^STRING1^STRING2^'
- Quick Substitution. Repeat the last command, replacing STRING1
- with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
+`\A'
+ The time, in 24-hour HH:MM format.
-`!#'
- The entire command line typed so far.
+`\u'
+ The username of the current user.
-\1f
-File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
+`\v'
+ The version of Bash (e.g., 2.00)
-Word Designators
-----------------
+`\V'
+ The release of Bash, version + patchlevel (e.g., 2.00.0)
- Word designators are used to select desired words from the event. A
-`:' separates the event specification from the word designator. It may
-be omitted if the word designator begins with a `^', `$', `*', `-', 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.
+`\w'
+ The current working directory, with `$HOME' abbreviated with a
+ tilde (uses the `$PROMPT_DIRTRIM' variable).
-`0 (zero)'
- The `0'th word. For many applications, this is the command word.
+`\W'
+ The basename of `$PWD', with `$HOME' abbreviated with a tilde.
-`N'
- The Nth word.
+`\!'
+ The history number of this command.
-`^'
- The first argument; that is, word 1.
+`\#'
+ The command number of this command.
-`$'
- The last argument.
+`\$'
+ If the effective uid is 0, `#', otherwise `$'.
-`%'
- The word matched by the most recent `?STRING?' search.
+`\NNN'
+ The character whose ASCII code is the octal value NNN.
-`X-Y'
- A range of words; `-Y' abbreviates `0-Y'.
+`\\'
+ A backslash.
-`*'
- 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.
+`\['
+ Begin a sequence of non-printing characters. This could be used to
+ embed a terminal control sequence into the prompt.
-`X*'
- Abbreviates `X-$'
+`\]'
+ End a sequence of non-printing characters.
-`X-'
- Abbreviates `X-$' like `X*', but omits the last word.
+ 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.
- If a word designator is supplied without an event specification, the
-previous command is used as the event.
+ 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::).
\1f
-File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
+File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
-Modifiers
----------
+6.10 The Restricted Shell
+=========================
- After the optional word designator, you can add a sequence of one or
-more of the following modifiers, each preceded by a `:'.
+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:
-`h'
- Remove a trailing pathname component, leaving only the head.
+ * Changing directories with the `cd' builtin.
-`t'
- Remove all leading pathname components, leaving the tail.
+ * Setting or unsetting the values of the `SHELL', `PATH', `ENV', or
+ `BASH_ENV' variables.
-`r'
- Remove a trailing suffix of the form `.SUFFIX', leaving the
- basename.
+ * Specifying command names containing slashes.
-`e'
- Remove all but the trailing suffix.
+ * Specifying a filename containing a slash as an argument to the `.'
+ builtin command.
-`p'
- Print the new command but do not execute it.
+ * Specifying a filename containing a slash as an argument to the `-p'
+ option to the `hash' builtin command.
-`q'
- Quote the substituted words, escaping further substitutions.
+ * Importing function definitions from the shell environment at
+ startup.
-`x'
- Quote the substituted words as with `q', but break into words at
- spaces, tabs, and newlines.
+ * Parsing the value of `SHELLOPTS' from the shell environment at
+ startup.
-`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.
+ * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
+ redirection operators.
-`&'
- Repeat the previous substitution.
+ * Using the `exec' builtin to replace the shell with another command.
-`g'
- Cause changes to be applied over the entire event line. Used in
- conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
+ * Adding or deleting builtin commands with the `-f' and `-d' options
+ to the `enable' builtin.
-\1f
-File: bashref.info, Node: Command Line Editing, Next: Installing Bash, Prev: Using History Interactively, Up: Top
+ * Using the `enable' builtin command to enable disabled shell
+ builtins.
-Command Line Editing
-********************
+ * Specifying the `-p' option to the `command' builtin.
- This chapter describes the basic features of the GNU command line
-editing interface.
+ * Turning off restricted mode with `set +r' or `set +o restricted'.
-* Menu:
+ These restrictions are enforced after any startup files are read.
-* 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.
+ 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.
\1f
-File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
+File: bashref.info, Node: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
-Introduction to Line Editing
-============================
+6.11 Bash POSIX Mode
+====================
- The following paragraphs describe the notation used to represent
-keystrokes.
+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.
- 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.
+ When invoked as `sh', Bash enters POSIX mode after reading the
+startup files.
- 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.
+ The following list is what's changed when `POSIX mode' is in effect:
- The text <M-C-k> is read as `Meta-Control-k' and describes the
-character produced by "metafying" <C-k>.
+ 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'.
- 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::.).
+ 2. The message printed by the job control code and builtins when a job
+ exits with a non-zero status is `Done(status)'.
-\1f
-File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
+ 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'.
-Readline Interaction
-====================
+ 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.
- 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.
+ 5. Reserved words appearing in a context where reserved words are
+ recognized do not undergo alias expansion.
-* Menu:
+ 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.
-* 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.
+ 7. The POSIX startup files are executed (`$ENV') rather than the
+ normal Bash files.
-\1f
-File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
+ 8. Tilde expansion is only performed on assignments preceding a
+ command name, rather than on all assignment statements on the line.
-Readline Bare Essentials
-------------------------
+ 9. The default history file is `~/.sh_history' (this is the default
+ value of `$HISTFILE').
- 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.
+ 10. The output of `kill -l' prints all the signal names on a single
+ line, separated by spaces, without the `SIG' prefix.
- 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>.
+ 11. The `kill' builtin does not accept signal names with a `SIG'
+ prefix.
- 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.
+ 12. Non-interactive shells exit if FILENAME in `.' FILENAME is not
+ found.
-<C-b>
- Move back one character.
+ 13. Non-interactive shells exit if a syntax error in an arithmetic
+ expansion results in an invalid expression.
-<C-f>
- Move forward one character.
+ 14. Non-interactive shells exit if there is a syntax error in a script
+ read with the `.' or `source' builtins, or in a string processed by
+ the `eval' builtin.
-<DEL>
- Delete the character to the left of the cursor.
+ 15. Redirection operators do not perform filename expansion on the word
+ in the redirection unless the shell is interactive.
-<C-d>
- Delete the character underneath the cursor.
+ 16. Redirection operators do not perform word splitting on the word in
+ the redirection.
-Printing characters
- Insert the character into the line at the cursor.
+ 17. 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.
-<C-_>
- Undo the last editing command. You can undo all the way back to an
- empty line.
+ 18. POSIX special builtins are found before shell functions during
+ command lookup.
-\1f
-File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
+ 19. The `time' reserved word may be used by itself as a command. When
+ used in this way, it displays timing statistics for the shell and
+ its completed children. The `TIMEFORMAT' variable controls the
+ format of the timing information.
-Readline Movement Commands
---------------------------
+ 20. When parsing and expanding a ${...} expansion that appears within
+ double quotes, single quotes are no longer special and cannot be
+ used to quote a closing brace or other special character, unless
+ the operator is one of those defined to perform pattern removal.
+ In this case, they do not have to appear as matched pairs.
- 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.
+ 21. The parser does not recognize `time' as a reserved word if the next
+ token begins with a `-'.
-<C-a>
- Move to the start of the line.
+ 22. 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.
-<C-e>
- Move to the end of the line.
+ 23. 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.
-<M-f>
- Move forward a word, where a word is composed of letters and
- digits.
+ 24. A non-interactive shell exists with an error status if a variable
+ assignment error occurs in an assignment statement preceding a
+ special builtin, but not with any other simple command.
-<M-b>
- Move backward a word.
+ 25. 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.
-<C-l>
- Clear the screen, reprinting the current line at the top.
+ 26. Process substitution is not available.
- 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.
+ 27. Assignment statements preceding POSIX special builtins persist in
+ the shell environment after the builtin completes.
-\1f
-File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
+ 28. 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.
-Readline Killing Commands
--------------------------
+ 29. The `export' and `readonly' builtin commands display their output
+ in the format required by POSIX.
- "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.
+ 30. The `trap' builtin displays signal names without the leading `SIG'.
- 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.
+ 31. 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.
- Here is the list of commands for killing text.
+ 32. The `.' and `source' builtins do not search the current directory
+ for the filename argument if it is not found by searching `PATH'.
-<C-k>
- Kill the text from the current cursor position to the end of the
- line.
+ 33. 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.
-<M-d>
- Kill from the cursor to the end of the current word, or if between
- words, to the end of the next word.
+ 34. Alias expansion is always enabled, even in non-interactive shells.
-<M-DEL>
- Kill from the cursor the start of the previous word, or if between
- words, to the start of the previous word.
+ 35. When the `alias' builtin displays alias definitions, it does not
+ display them with a leading `alias ' unless the `-p' option is
+ supplied.
-<C-w>
- Kill from the cursor to the previous whitespace. This is
- different than <M-DEL> because the word boundaries differ.
+ 36. When the `set' builtin is invoked without options, it does not
+ display shell function names and definitions.
- Here is how to "yank" the text back into the line. Yanking means to
-copy the most-recently-killed text from the kill buffer.
+ 37. 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.
-<C-y>
- Yank the most recently killed text back into the buffer at the
- cursor.
+ 38. 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.
-<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>.
+ 39. 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.
-\1f
-File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
+ 40. When listing the history, the `fc' builtin does not include an
+ indication of whether or not a history entry has been modified.
-Readline Arguments
-------------------
+ 41. The default editor used by `fc' is `ed'.
- 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'.
+ 42. 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
+ `$PATH'.
- The general way to pass numeric arguments to a command is to type
-meta digits before the command. If the first `digit' typed is a minus
-sign (<->), then the sign of the argument will be negative. Once you
-have typed one meta digit to get the argument started, you can type the
-remainder of the digits, and then the command. For example, to give
-the <C-d> command an argument of 10, you could type `M-1 0 C-d'.
+ 43. The `vi' editing mode will invoke the `vi' editor directly when
+ the `v' command is run, instead of checking `$VISUAL' and
+ `$EDITOR'.
-\1f
-File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
+ 44. 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.
-Searching for Commands in the History
--------------------------------------
+ 45. The `ulimit' builtin uses a block size of 512 bytes for the `-c'
+ and `-f' options.
- 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.
+ 46. The arrival of `SIGCHLD' when a trap is set on `SIGCHLD' does not
+ interrupt the `wait' builtin and cause it to return immediately.
+ The trap command is run once for each child that exits.
- 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 <ESC> character is
-used to terminate an incremental search. <C-j> will also terminate the
-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-s> or <C-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 <RET> will terminate the search
-and accept the line, thereby executing the command from the history
-list.
- 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.
+ There is other POSIX behavior that Bash does not implement by
+default even when in POSIX mode. Specifically:
-\1f
-File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
+ 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.
-Readline Init File
-==================
+ 2. As noted above, Bash requires the `xpg_echo' option to be enabled
+ for the `echo' builtin to be fully conformant.
- 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 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'.
- When a program which uses the Readline library starts up, the init
-file is read, and the key bindings are set.
+ Bash can be configured to be POSIX-conformant by default, by
+specifying the `--enable-strict-posix-default' to `configure' when
+building (*note Optional Features::).
- In addition, the `C-x C-r' command re-reads this init file, thus
-incorporating any changes that you might have made to it.
+\1f
+File: bashref.info, Node: Job Control, Next: Command Line Editing, Prev: Bash Features, Up: Top
-* Menu:
+7 Job Control
+*************
-* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
+This chapter discusses what job control is, how it works, and how Bash
+allows you to access its facilities.
-* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
+* Menu:
-* Sample Init File:: An example inputrc file.
+* 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.
\1f
-File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
-
-Readline Init File Syntax
--------------------------
-
- 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.
+File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
-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. Here is how to change from the default Emacs-like key
- binding to use `vi' line editing commands:
+7.1 Job Control Basics
+======================
- set editing-mode vi
+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 operating system kernel's terminal
+driver and Bash.
- A great deal of run-time behavior is changeable with the following
- variables.
+ 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.
- `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.
+ 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, if the user so specifies with `stty tostop', write to
+the terminal. Background processes which attempt to read from (write
+to when `stty tostop' is in effect) the terminal are sent a `SIGTTIN'
+(`SIGTTOU') signal by the kernel's terminal driver, which, unless
+caught, suspends the process.
- `comment-begin'
- The string to insert at the beginning of the line when the
- `insert-comment' command is executed. The default value is
- `"#"'.
+ 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.
- `completion-ignore-case'
- If set to `on', Readline performs filename matching and
- completion in a case-insensitive fashion. The default value
- is `off'.
+ 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.
- `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'.
+ 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'
- `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 prepending an <ESC> character, converting them
- to a meta-prefixed key sequence. The default value is `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.
- `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'.
+\1f
+File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
- `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'.
+7.2 Job Control Builtins
+========================
- `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'.
+`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.
- `expand-tilde'
- If set to `on', tilde expansion is performed when Readline
- attempts word completion. The default is `off'.
+`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.
- `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'.
+`jobs'
+ jobs [-lnprs] [JOBSPEC]
+ jobs -x COMMAND [ARGUMENTS]
- `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.
+ The first form lists the active jobs. The options have the
+ following meanings:
- `mark-directories'
- If set to `on', completed directory names have a slash
- appended. The default is `on'.
+ `-l'
+ List process IDs in addition to the normal information.
- `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.
+ `-n'
+ Display information only about jobs that have changed status
+ since the user was last notified of their status.
- `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.
+ `-p'
+ List only the process ID of the job's process group leader.
- `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'.
+ `-r'
+ Restrict output to running jobs.
- `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'.
+ `-s'
+ Restrict output to stopped jobs.
- `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'.
+ If JOBSPEC is given, output is restricted to information about
+ that job. If JOBSPEC is not supplied, the status of all jobs is
+ listed.
- `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'.
+ 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.
-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 sections contain tables of the
- command name, the default keybinding, if any, and a short
- description of what the command does.
+`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.
- 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.
+`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.
- 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"
+`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.
- 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).
+`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.
- "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.
- "\C-u": universal-argument
- "\C-x\C-r": re-read-init-file
- "\e[11~": "Function Key 1"
+ When job control is not active, the `kill' and `wait' builtins do
+not accept JOBSPEC arguments. They must be supplied process IDs.
- 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'.
+\1f
+File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
- The following GNU Emacs style escape sequences are available when
- specifying key sequences:
+7.3 Job Control Variables
+=========================
- `\C-'
- control prefix
+`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.
- `\M-'
- meta prefix
- `\e'
- an escape character
+\1f
+File: bashref.info, Node: Command Line Editing, Next: Using History Interactively, Prev: Job Control, Up: Top
+
+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'.
- `\\'
- backslash
+* Menu:
- `\"'
- <">
+* 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.
- `\''
- <'>
+* 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.
- In addition to the GNU Emacs style escape sequences, a second set
- of backslash escapes is available:
+\1f
+File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
- `\a'
- alert (bell)
+8.1 Introduction to Line Editing
+================================
- `\b'
- backspace
+The following paragraphs describe the notation used to represent
+keystrokes.
- `\d'
- delete
+ 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.
- `\f'
- form feed
+ 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.
- `\n'
- newline
+ 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.
- `\r'
- carriage return
+ The text `M-C-k' is read as `Meta-Control-k' and describes the
+character produced by "metafying" `C-k'.
- `\t'
- horizontal tab
+ 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.
- `\v'
- vertical tab
+\1f
+File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
- `\NNN'
- the character whose ASCII code is the octal value NNN (one to
- three digits)
+8.2 Readline Interaction
+========================
- `\xNNN'
- the character whose ASCII code is the hexadecimal value NNN
- (one to three digits)
+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.
- 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\\": "\\"
+* Menu:
+
+* 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.
\1f
-File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
+File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
-Conditional Init Constructs
----------------------------
+8.2.1 Readline Bare Essentials
+------------------------------
- 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.
+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.
-`$if'
- The `$if' construct allows bindings to be made based on the
- editing mode, the terminal being used, or the application using
- Readline. The text of the test extends to the end of the line; no
- characters are required to isolate it.
+ Sometimes you may mistype a character, and not notice the error
+until you have typed several other characters. In that case, you can
+type `C-b' to move the cursor to the left, and then correct your
+mistake. Afterwards, you can move the cursor to the right with `C-f'.
- `mode'
- The `mode=' form of the `$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.
+ 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.
- `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.
+`C-b'
+ Move back one character.
- `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\""
- $endif
+`C-f'
+ Move forward one character.
-`$endif'
- This command, as seen in the previous example, terminates an `$if'
- command.
+<DEL> or <Backspace>
+ Delete the character to the left of the cursor.
-`$else'
- Commands in this branch of the `$if' directive are executed if the
- test fails.
+`C-d'
+ Delete the character underneath the cursor.
-`$include'
- This directive takes a single filename as an argument and reads
- commands and bindings from that file.
- $include /etc/inputrc
+Printing characters
+ Insert the character into the line at the cursor.
+
+`C-_' or `C-x C-u'
+ Undo the last editing command. You can undo all the way back to an
+ empty line.
+
+(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: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
+File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
-Sample Init File
-----------------
+8.2.2 Readline Movement Commands
+--------------------------------
- Here is an example of an inputrc file. This illustrates key
-binding, variable assignment, and conditional syntax.
+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.
+`C-a'
+ Move to the start of the line.
- # 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
-
- #
- # 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
+`C-e'
+ Move to the end of the line.
-\1f
-File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
+`M-f'
+ Move forward a word, where a word is composed of letters and
+ digits.
-Bindable Readline Commands
-==========================
+`M-b'
+ Move backward a word.
-* Menu:
+`C-l'
+ Clear the screen, reprinting the current line at the top.
-* Commands For Moving:: Moving about the line.
+ 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: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
+
+8.2.3 Readline Killing Commands
+-------------------------------
+
+"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'.)
+
+ 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.
+
+ 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.
+
+ Here is the list of commands for killing text.
+
+`C-k'
+ Kill the text from the current cursor position to the end of the
+ line.
+
+`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'.
+
+`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'.
+
+`C-w'
+ Kill from the cursor to the previous whitespace. This is
+ different than `M-<DEL>' because the word boundaries differ.
+
+
+ Here is how to "yank" the text back into the line. Yanking means to
+copy the most-recently-killed text from the kill buffer.
+
+`C-y'
+ Yank the most recently killed text back into the buffer at the
+ cursor.
+
+`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'.
+
+\1f
+File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
+
+8.2.4 Readline Arguments
+------------------------
+
+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'.
+
+ 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.
+
+\1f
+File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
+
+8.2.5 Searching for Commands in the History
+-------------------------------------------
+
+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".
+
+ 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.
+
+ 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.
+
+\1f
+File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
+
+8.3 Readline Init File
+======================
+
+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'.
+
+ When a program which uses the Readline library starts up, the init
+file is read, and the key bindings are set.
+
+ In addition, the `C-x C-r' command re-reads this init file, thus
+incorporating any changes that you might have made to it.
+
+* Menu:
+
+* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
+
+* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
+
+* Sample Init File:: An example inputrc file.
+
+\1f
+File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
+
+8.3.1 Readline Init File Syntax
+-------------------------------
+
+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.
+
+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:
+
+ set VARIABLE VALUE
+
+ Here, for example, is how to change from the default Emacs-like
+ key binding to use `vi' line editing commands:
+
+ set editing-mode vi
+
+ Variable names and values, where appropriate, are recognized
+ without regard to case. Unrecognized variable names are ignored.
+
+ 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.
+
+ The `bind -V' command lists the current Readline variable names
+ and values. *Note Bash Builtins::.
+
+ A great deal of run-time behavior is changeable with the following
+ variables.
+
+ `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.
+
+ `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.
+
+ `comment-begin'
+ The string to insert at the beginning of the line when the
+ `insert-comment' command is executed. The default value is
+ `"#"'.
+
+ `completion-display-width'
+ The number of screen columns used to display possible matches
+ when performing completion. The value is ignored if it is
+ less than 0 or greater than the terminal screen width. A
+ value of 0 will cause matches to be displayed one per line.
+ The default value is -1.
+
+ `completion-ignore-case'
+ If set to `on', Readline performs filename matching and
+ completion in a case-insensitive fashion. The default value
+ is `off'.
+
+ `completion-map-case'
+ If set to `on', and COMPLETION-IGNORE-CASE is enabled,
+ Readline treats hyphens (`-') and underscores (`_') as
+ equivalent when performing case-insensitive filename matching
+ and completion.
+
+ `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.
+
+ `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'.
+
+ `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'.
+
+ `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'.
+
+ `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'.
+
+ `echo-control-characters'
+ When set to `on', on operating systems that indicate they
+ support it, readline echoes a character corresponding to a
+ signal generated from the keyboard. The default is `on'.
+
+ `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'.
+
+ `enable-meta-key'
+ When set to `on', Readline will try to enable any meta
+ modifier key the terminal claims to support when it is
+ called. On many terminals, the meta key is used to send
+ eight-bit characters. The default is `on'.
+
+ `expand-tilde'
+ If set to `on', tilde expansion is performed when Readline
+ attempts word completion. The default is `off'.
+
+ `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'.
+
+ `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.
+
+ `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'.
+
+ `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.
+
+ `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.
+
+ `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.
+
+ `mark-directories'
+ If set to `on', completed directory names have a slash
+ appended. The default is `on'.
+
+ `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. If set to `off', the leading
+ `.' must be supplied by the user in the filename to be
+ completed. This variable is `on' by default.
+
+ `menu-complete-display-prefix'
+ If set to `on', menu completion displays the common prefix of
+ the list of possible completions (which may be empty) before
+ cycling through the list. The default is `off'.
+
+ `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'.
+
+ `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.
+
+ `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'.
+
+ `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'.
+
+ `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'.
+
+ `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'.
+
+ `skip-completed-text'
+ If set to `on', this alters the default completion behavior
+ when inserting a single match into the line. It's only
+ active when performing completion in the middle of a word.
+ If enabled, readline does not insert characters from the
+ completion that match characters after point in the word
+ being completed, so portions of the word following the cursor
+ are not duplicated. For instance, if this is enabled,
+ attempting completion when the cursor is after the `e' in
+ `Makefile' will result in `Makefile' rather than
+ `Makefilefile', assuming there is a single possible
+ completion. The default value is `off'.
+
+ `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'.
+
+
+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.
+
+ 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.
+
+ In addition to command names, readline allows keys to be bound to
+ a string that is inserted when the key is pressed (a MACRO).
+
+ 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"
+
+ 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).
+
+ 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.
+
+ "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.
+
+ "\C-u": universal-argument
+ "\C-x\C-r": re-read-init-file
+ "\e[11~": "Function Key 1"
+
+ 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'.
+
+
+ The following GNU Emacs style escape sequences are available when
+ specifying key sequences:
+
+ `\C-'
+ control prefix
+
+ `\M-'
+ meta prefix
+
+ `\e'
+ an escape character
+
+ `\\'
+ backslash
+
+ `\"'
+ <">, a double quotation mark
+
+ `\''
+ <'>, a single quote or apostrophe
+
+ In addition to the GNU Emacs style escape sequences, a second set
+ of backslash escapes is available:
+
+ `\a'
+ alert (bell)
+
+ `\b'
+ backspace
+
+ `\d'
+ delete
+
+ `\f'
+ form feed
+
+ `\n'
+ newline
+
+ `\r'
+ carriage return
+
+ `\t'
+ horizontal tab
+
+ `\v'
+ vertical tab
+
+ `\NNN'
+ 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)
+
+ 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\\": "\\"
+
+
+\1f
+File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
+
+8.3.2 Conditional Init Constructs
+---------------------------------
+
+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.
+
+`$if'
+ The `$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.
+
+ `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.
+
+ `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.
+
+ `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\""
+ $endif
+
+`$endif'
+ This command, as seen in the previous example, terminates an `$if'
+ command.
+
+`$else'
+ Commands in this branch of the `$if' directive are executed if the
+ test fails.
+
+`$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: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
+
+8.3.3 Sample Init File
+----------------------
+
+Here is an example of an INPUTRC file. This illustrates key binding,
+variable assignment, and conditional syntax.
+
+
+ # 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
+
+ #
+ # 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
+
+\1f
+File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
+
+8.4 Bindable Readline Commands
+==============================
+
+* Menu:
+
+* 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.
* Keyboard Macros:: Saving and re-executing typed characters
* Miscellaneous Commands:: Other miscellaneous commands.
- This section describes Readline commands that may be bound to key
-sequences.
+ 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.
+
+ 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".
+
+\1f
+File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
+
+8.4.1 Commands For Moving
+-------------------------
+
+`beginning-of-line (C-a)'
+ Move to the start of the current line.
+
+`end-of-line (C-e)'
+ Move to the end of the line.
+
+`forward-char (C-f)'
+ Move forward a character.
+
+`backward-char (C-b)'
+ Move back a character.
+
+`forward-word (M-f)'
+ Move forward to the end of the next word. Words are composed of
+ letters and digits.
+
+`backward-word (M-b)'
+ Move back to the start of the current or previous word. Words are
+ composed of letters and digits.
+
+`shell-forward-word ()'
+ Move forward to the end of the next word. Words are delimited by
+ non-quoted shell metacharacters.
+
+`shell-backward-word ()'
+ Move back to the start of the current or previous word. Words are
+ delimited by non-quoted shell metacharacters.
+
+`clear-screen (C-l)'
+ Clear the screen and redraw the current line, leaving the current
+ line at the top of the screen.
+
+`redraw-current-line ()'
+ Refresh the current line. By default, this is unbound.
+
+
+\1f
+File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
+
+8.4.2 Commands For Manipulating The History
+-------------------------------------------
+
+`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.
+
+`previous-history (C-p)'
+ Move `back' through the history list, fetching the previous
+ command.
+
+`next-history (C-n)'
+ Move `forward' through the history list, fetching the next command.
+
+`beginning-of-history (M-<)'
+ Move to the first line in the history.
+
+`end-of-history (M->)'
+ Move to the end of the input history, i.e., the line currently
+ being entered.
+
+`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.
+
+`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.
+
+`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.
+
+`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.
+
+`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.
+
+`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.
+
+`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 a numeric argument, behave exactly
+ like `yank-nth-arg'. Successive calls to `yank-last-arg' move
+ back through the history list, inserting the last word (or the
+ word specified by the argument to the first call) of each line in
+ turn. Any numeric argument supplied to these successive calls
+ determines the direction to move through the history. A negative
+ argument switches the direction through the history (back or
+ forward). The history expansion facilities are used to extract
+ the last argument, as if the `!$' history expansion had been
+ specified.
+
+
+\1f
+File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
+
+8.4.3 Commands For Changing Text
+--------------------------------
+
+`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.
+
+`backward-delete-char (Rubout)'
+ Delete the character behind the cursor. A numeric argument means
+ to kill the characters instead of deleting them.
+
+`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.
+
+`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.
+
+`self-insert (a, b, A, 1, !, ...)'
+ Insert yourself.
+
+`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.
+
+`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.
+
+`upcase-word (M-u)'
+ Uppercase the current (or following) word. With a negative
+ argument, uppercase the previous word, but do not move the cursor.
+
+`downcase-word (M-l)'
+ Lowercase the current (or following) word. With a negative
+ argument, lowercase the previous word, but do not move the cursor.
+
+`capitalize-word (M-c)'
+ Capitalize the current (or following) word. With a negative
+ argument, capitalize the previous word, but do not move the cursor.
+
+`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 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.
+
+ By default, this command is unbound.
+
+
+\1f
+File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
+
+8.4.4 Killing And Yanking
+-------------------------
+
+`kill-line (C-k)'
+ Kill the text from point to the end of the line.
+
+`backward-kill-line (C-x Rubout)'
+ Kill backward to the beginning of the line.
+
+`unix-line-discard (C-u)'
+ Kill backward from the cursor to the beginning of the current line.
+
+`kill-whole-line ()'
+ Kill all characters on the current line, no matter where point is.
+ By default, this is unbound.
+
+`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'.
+
+`backward-kill-word (M-<DEL>)'
+ Kill the word behind point. Word boundaries are the same as
+ `backward-word'.
+
+`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'.
+
+`shell-backward-kill-word ()'
+ Kill the word behind point. Word boundaries are the same as
+ `shell-backward-word'.
+
+`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.
+
+`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.
+
+`delete-horizontal-space ()'
+ Delete all spaces and tabs around point. By default, this is
+ unbound.
+
+`kill-region ()'
+ Kill the text in the current region. By default, this command is
+ unbound.
+
+`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.
+
+`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.
+
+`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.
+
+`yank (C-y)'
+ Yank the top of the kill ring into the buffer at point.
+
+`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: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
+File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
-Commands For Moving
--------------------
+8.4.5 Specifying Numeric Arguments
+----------------------------------
-`beginning-of-line (C-a)'
- Move to the start of the current line.
+`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.
-`end-of-line (C-e)'
- Move to the end of the line.
+`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.
-`forward-char (C-f)'
- Move forward a character.
+\1f
+File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
-`backward-char (C-b)'
- Move back a character.
+8.4.6 Letting Readline Type For You
+-----------------------------------
-`forward-word (M-f)'
- Move forward to the end of the next word. Words are composed of
- letters and digits.
+`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.
-`backward-word (M-b)'
- Move back to the start of this, or the previous, word. Words are
- composed of letters and digits.
+`possible-completions (M-?)'
+ List the possible completions of the text before point. When
+ displaying completions, Readline sets the number of columns used
+ for display to the value of `completion-display-width', the value
+ of the environment variable `COLUMNS', or the screen width, in
+ that order.
+
+`insert-completions (M-*)'
+ Insert all completions of the text before point that would have
+ been generated by `possible-completions'.
+
+`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.
+
+`menu-complete-backward ()'
+ Identical to `menu-complete', but moves backward through the list
+ of possible completions, as if `menu-complete' had been given a
+ negative argument.
+
+`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.
+
+`complete-filename (M-/)'
+ Attempt filename completion on the text before point.
+
+`possible-filename-completions (C-x /)'
+ List the possible completions of the text before point, treating
+ it as a filename.
+
+`complete-username (M-~)'
+ Attempt completion on the text before point, treating it as a
+ username.
+
+`possible-username-completions (C-x ~)'
+ List the possible completions of the text before point, treating
+ it as a username.
+
+`complete-variable (M-$)'
+ Attempt completion on the text before point, treating it as a
+ shell variable.
+
+`possible-variable-completions (C-x $)'
+ List the possible completions of the text before point, treating
+ it as a shell variable.
+
+`complete-hostname (M-@)'
+ Attempt completion on the text before point, treating it as a
+ hostname.
+
+`possible-hostname-completions (C-x @)'
+ List the possible completions of the text before point, treating
+ it as a hostname.
+
+`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.
+
+`possible-command-completions (C-x !)'
+ List the possible completions of the text before point, treating
+ it as a command name.
+
+`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.
+
+`dabbrev-expand ()'
+ Attempt menu completion on the text before point, comparing the
+ text against lines from the history list for possible completion
+ matches.
+
+`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::).
+
+
+\1f
+File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
+
+8.4.7 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.
+
+`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.
+
+
+\1f
+File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
+
+8.4.8 Some Miscellaneous Commands
+---------------------------------
+
+`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.
+
+`abort (C-g)'
+ Abort the current editing command and ring the terminal's bell
+ (subject to the setting of `bell-style').
+
+`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.
+
+`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'.
+
+`undo (C-_ or C-x C-u)'
+ Incremental undo, separately remembered for each line.
+
+`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.
+
+`tilde-expand (M-&)'
+ Perform tilde expansion on the current word.
+
+`set-mark (C-@)'
+ Set the mark to the point. If a numeric argument is supplied, the
+ mark is set to that position.
+
+`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.
+
+`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.
+
+`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.
+
+`skip-csi-sequence ()'
+ Read enough characters to consume a multi-key sequence such as
+ those defined for keys like Home and End. Such sequences begin
+ with a Control Sequence Indicator (CSI), usually ESC-[. If this
+ sequence is bound to "\e[", keys producing such sequences will
+ have no effect unless explicitly bound to a readline command,
+ instead of inserting stray characters into the editing buffer.
+ This is unbound by default, but usually bound to ESC-[.
+
+`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.
+
+`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.
+
+`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 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.
+
+`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.
+
+`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::).
+
+`history-expand-line (M-^)'
+ Perform history expansion on the current line.
+
+`magic-space ()'
+ Perform history expansion on the current line and insert a space
+ (*note History Interaction::).
+
+`alias-expand-line ()'
+ Perform alias expansion on the current line (*note Aliases::).
+
+`history-and-alias-expand-line ()'
+ Perform history and alias expansion on the current line.
+
+`insert-last-argument (M-. or M-_)'
+ A synonym for `yank-last-arg'.
+
+`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.
-`clear-screen (C-l)'
- Clear the screen and redraw the current line, leaving the current
- line at the top of the screen.
+`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.
-`redraw-current-line ()'
- Refresh the current line. By default, this is unbound.
\1f
-File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
+File: bashref.info, Node: Readline vi Mode, Next: Programmable Completion, Prev: Bindable Readline Commands, Up: Command Line Editing
-Commands For Manipulating The History
--------------------------------------
+8.5 Readline vi Mode
+====================
-`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' and `HISTIGNORE' variables. If this line was a
- history line, then restore the history line to its original state.
+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 standard.
-`previous-history (C-p)'
- Move `up' through the history list.
+ 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.
-`next-history (C-n)'
- Move `down' through the history list.
+ 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.
-`beginning-of-history (M-<)'
- Move to the first line in the history.
+\1f
+File: bashref.info, Node: Programmable Completion, Next: Programmable Completion Builtins, Prev: Readline vi Mode, Up: Command Line Editing
-`end-of-history (M->)'
- Move to the end of the input history, i.e., the line currently
- being entered.
+8.6 Programmable Completion
+===========================
-`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.
+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 the empty
+string (completion attempted at the beginning of an empty line), any
+compspec defined with the `-E' option to `complete' is used. 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. If those searches do not result in a compspec, any compspec
+defined with the `-D' option to `complete' is used as the default.
+
+ 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.
+
+ There is some support for dynamically modifying completions. This is
+most useful when used in combination with a default completion specified
+with `-D'. It's possible for shell functions executed as completion
+handlers to indicate that completion should be retried by returning an
+exit status of 124. If a shell function returns 124, and changes the
+compspec associated with the command on which completion is being
+attempted (supplied as the first argument when the function is
+executed), programmable completion restarts from the beginning, with an
+attempt to find a new compspec for that command. This allows a set of
+completions to be built dynamically as completion is attempted, rather
+than being loaded all at once.
+
+ For instance, assuming that there is a library of compspecs, each
+kept in a file corresponding to the name of the command, the following
+default completion function would load completions dynamically:
+
+ _completion_loader()
+ {
+ . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
+ }
+ complete -D -F _completion_loader
-`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.
+\1f
+File: bashref.info, Node: Programmable Completion Builtins, Prev: Programmable Completion, Up: Command Line Editing
-`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.
+8.7 Programmable Completion Builtins
+====================================
-`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.
+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.
+
+ The return value is true unless an invalid option is supplied, or
+ no matches were generated.
+
+`complete'
+ `complete [-abcdefgjksuv] [-o COMP-OPTION] [-DE] [-A ACTION] [-G GLOBPAT] [-W WORDLIST]
+ [-F FUNCTION] [-C COMMAND] [-X FILTERPAT]
+ [-P PREFIX] [-S SUFFIX] NAME [NAME ...]'
+ `complete -pr [-DE] [NAME ...]'
+
+ 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 `-D' option indicates that the
+ remaining options and actions should apply to the "default"
+ command completion; that is, completion attempted on a command for
+ which no completion has previously been defined. The `-E' option
+ indicates that the remaining options and actions should apply to
+ "empty" command completion; that is, completion attempted on a
+ blank line.
+
+ The process of applying these completion specifications when word
+ completion is attempted is described above (*note Programmable
+ Completion::). The `-D' option takes precedence over `-E'.
+
+ 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.
+
+ `-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:
+
+ `bashdefault'
+ Perform the rest of the default Bash completions if the
+ compspec generates no matches.
+
+ `default'
+ Use Readline's default filename completion if the
+ compspec generates no matches.
+
+ `dirnames'
+ Perform directory name completion if the compspec
+ generates no matches.
+
+ `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'.
+
+ `nospace'
+ Tell Readline not to append a space (the default) to
+ words completed at the end of the line.
+
+ `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.
+
+
+ `-A ACTION'
+ The ACTION may be one of the following to generate a list of
+ possible completions:
+
+ `alias'
+ Alias names. May also be specified as `-a'.
+
+ `arrayvar'
+ Array variable names.
+
+ `binding'
+ Readline key binding names (*note Bindable Readline
+ Commands::).
+
+ `builtin'
+ Names of shell builtin commands. May also be specified
+ as `-b'.
+
+ `command'
+ Command names. May also be specified as `-c'.
+
+ `directory'
+ Directory names. May also be specified as `-d'.
+
+ `disabled'
+ Names of disabled shell builtins.
+
+ `enabled'
+ Names of enabled shell builtins.
+
+ `export'
+ Names of exported shell variables. May also be
+ specified as `-e'.
-`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.
+ `file'
+ File names. May also be specified as `-f'.
-`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.
+ `function'
+ Names of shell functions.
+
+ `group'
+ Group names. May also be specified as `-g'.
-`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.
+ `helptopic'
+ Help topics as accepted by the `help' builtin (*note
+ Bash Builtins::).
-`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'. Successive calls to `yank-last-arg' move back
- through the history list, inserting the last argument of each line
- in turn.
+ `hostname'
+ Hostnames, as taken from the file specified by the
+ `HOSTFILE' shell variable (*note Bash Variables::).
-\1f
-File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
+ `job'
+ Job names, if job control is active. May also be
+ specified as `-j'.
-Commands For Changing Text
---------------------------
+ `keyword'
+ Shell reserved words. May also be specified as `-k'.
+
+ `running'
+ Names of running jobs, if job control is active.
+
+ `service'
+ Service names. May also be specified as `-s'.
+
+ `setopt'
+ Valid arguments for the `-o' option to the `set' builtin
+ (*note The Set Builtin::).
+
+ `shopt'
+ Shell option names as accepted by the `shopt' builtin
+ (*note Bash Builtins::).
+
+ `signal'
+ Signal names.
+
+ `stopped'
+ Names of stopped jobs, if job control is active.
+
+ `user'
+ User names. May also be specified as `-u'.
+
+ `variable'
+ Names of all shell variables. May also be specified as
+ `-v'.
+
+ `-C COMMAND'
+ COMMAND is executed in a subshell environment, and its output
+ is used as the possible completions.
+
+ `-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.
+
+ `-G GLOBPAT'
+ The filename expansion pattern GLOBPAT is expanded to generate
+ the possible completions.
+
+ `-P PREFIX'
+ PREFIX is added at the beginning of each possible completion
+ after all other options have been applied.
+
+ `-S SUFFIX'
+ SUFFIX is appended to each possible completion after all
+ other options have been applied.
+
+ `-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.
+
+ `-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.
+
+ 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] [-DE] [+o OPTION] [NAME]
+ Modify completion options for each NAME according to the OPTIONs,
+ or for the currently-executing 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 `-D'
+ option indicates that the remaining options should apply to the
+ "default" command completion; that is, completion attempted on a
+ command for which no completion has previously been defined. The
+ `-E' option indicates that the remaining options should apply to
+ "empty" command completion; that is, completion attempted on a
+ blank line.
+
+ The `-D' option takes precedence over `-E'.
+
+ 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.
-`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 bound to `delete-char', then
- return `EOF'.
-`backward-delete-char (Rubout)'
- Delete the character behind the cursor. A numeric argument means
- to kill the characters instead of deleting them.
+\1f
+File: bashref.info, Node: Using History Interactively, Next: Installing Bash, Prev: Command Line Editing, Up: Top
-`quoted-insert (C-q, C-v)'
- Add the next character typed to the line verbatim. This is how to
- insert key sequences like <C-q>, for example.
+9 Using History Interactively
+*****************************
-`self-insert (a, b, A, 1, !, ...)'
- Insert yourself.
+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.
-`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 don't work.
+* Menu:
-`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.
+* 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.
-`upcase-word (M-u)'
- Uppercase the current (or following) word. With a negative
- argument, uppercase the previous word, but do not move the cursor.
+\1f
+File: bashref.info, Node: Bash History Facilities, Next: Bash History Builtins, Up: Using History Interactively
-`downcase-word (M-l)'
- Lowercase the current (or following) word. With a negative
- argument, lowercase the previous word, but do not move the cursor.
+9.1 Bash History Facilities
+===========================
-`capitalize-word (M-c)'
- Capitalize the current (or following) word. With a negative
- argument, capitalize the previous word, but do not move the cursor.
+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.
-\1f
-File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
+ 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.
-Killing And Yanking
--------------------
+ 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::).
-`kill-line (C-k)'
- Kill the text from the current cursor position to the end of the
- line.
+ 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'.
-`backward-kill-line (C-x Rubout)'
- Kill backward to the beginning of the line.
+\1f
+File: bashref.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
-`unix-line-discard (C-u)'
- Kill backward from the cursor to the beginning of the current line.
- The killed text is saved on the kill-ring.
+9.2 Bash History Builtins
+=========================
-`kill-whole-line ()'
- Kill all characters on the current line, no matter where the
- cursor is. By default, this is unbound.
+Bash provides two builtin commands which manipulate the history list
+and history file.
-`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'.
+`fc'
+ `fc [-e ENAME] [-lnr] [FIRST] [LAST]'
+ `fc -s [PAT=REP] [COMMAND]'
-`backward-kill-word (M-DEL)'
- Kill the word behind the cursor. Word boundaries are the same as
- `backward-word'.
+ 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.
-`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.
+ In the second form, COMMAND is re-executed after each instance of
+ PAT in the selected command is replaced by REP.
-`delete-horizontal-space ()'
- Delete all spaces and tabs around point. By default, this is
- unbound.
+ 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-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.
+`history'
+ history [N]
+ history -c
+ history -d OFFSET
+ history [-anrw] [FILENAME]
+ history -ps ARG
-`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.
+ 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.
-`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.
+ Options, if supplied, have the following meanings:
-`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'
+ Clear the history list. This may be combined with the other
+ options to replace the history list completely.
-`yank (C-y)'
- Yank the top of the kill ring into the buffer at the current
- cursor position.
+ `-d OFFSET'
+ Delete the history entry at position OFFSET. OFFSET should
+ be specified as it appears when the history is displayed.
-`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.
+ `-a'
+ Append the new history lines (history lines entered since the
+ beginning of the current Bash session) to the history file.
-\1f
-File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
+ `-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.
-Specifying Numeric Arguments
-----------------------------
+ `-r'
+ Read the current history file and append its contents to the
+ history list.
-`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.
+ `-w'
+ Write out the current history to the history file.
-`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.
+ `-p'
+ Perform history substitution on the ARGs and display the
+ result on the standard output, without storing the results in
+ the history list.
-\1f
-File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
+ `-s'
+ The ARGs are added to the end of the history list as a single
+ entry.
-Letting Readline Type For You
------------------------------
-`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.
+ 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.
-`possible-completions (M-?)'
- List the possible completions of the text before the cursor.
-`insert-completions (M-*)'
- Insert all completions of the text before point that would have
- been generated by `possible-completions'.
+\1f
+File: bashref.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
-`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 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.
+9.3 History Expansion
+=====================
-`complete-filename (M-/)'
- Attempt filename completion on the text before point.
+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.
-`possible-filename-completions (C-x /)'
- List the possible completions of the text before point, treating
- it as a filename.
+ 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.
-`complete-username (M-~)'
- Attempt completion on the text before point, treating it as a
- username.
+ 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.
+
+ 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.
-`possible-username-completions (C-x ~)'
- List the possible completions of the text before point, treating
- it as a username.
+ 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.
-`complete-variable (M-$)'
- Attempt completion on the text before point, treating it as a
- shell variable.
+* Menu:
-`possible-variable-completions (C-x $)'
- List the possible completions of the text before point, treating
- it as a shell variable.
+* 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-hostname (M-@)'
- Attempt completion on the text before point, treating it as a
- hostname.
+\1f
+File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
-`possible-hostname-completions (C-x @)'
- List the possible completions of the text before point, treating
- it as a hostname.
+9.3.1 Event Designators
+-----------------------
-`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.
+An event designator is a reference to a command line entry in the
+history list. Unless the reference is absolute, events are relative to
+the current position in the history list.
-`possible-command-completions (C-x !)'
- List the possible completions of the text before point, treating
- it as a command name.
+`!'
+ 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).
-`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.
+`!N'
+ Refer to command line N.
-`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::.).
+`!-N'
+ Refer to the command N lines back.
-\1f
-File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
+`!!'
+ Refer to the previous command. This is a synonym for `!-1'.
-Keyboard Macros
----------------
+`!STRING'
+ Refer to the most recent command preceding the current position in
+ the history list starting with STRING.
-`start-kbd-macro (C-x ()'
- Begin saving the characters typed into the current keyboard macro.
+`!?STRING[?]'
+ Refer to the most recent command preceding the current position in
+ the history list containing STRING. The trailing `?' may be
+ omitted if the STRING is followed immediately by a newline.
-`end-kbd-macro (C-x ))'
- Stop saving the characters typed into the current keyboard macro
- and save the definition.
+`^STRING1^STRING2^'
+ Quick Substitution. Repeat the last command, replacing STRING1
+ with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
+
+`!#'
+ The entire command line typed so far.
-`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.
\1f
-File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
+File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
-Some Miscellaneous Commands
----------------------------
+9.3.2 Word Designators
+----------------------
-`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.
+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.
-`abort (C-g)'
- Abort the current editing command and ring the terminal's bell
- (subject to the setting of `bell-style').
+ For example,
-`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.
+`!!'
+ designates the preceding command. When you type this, the
+ preceding command is repeated in toto.
-`prefix-meta (ESC)'
- Make the next character typed be metafied. This is for keyboards
- without a meta key. Typing `ESC f' is equivalent to typing `M-f'.
+`!!:$'
+ designates the last argument of the preceding command. This may be
+ shortened to `!$'.
-`undo (C-_, C-x C-u)'
- Incremental undo, separately remembered for each line.
+`!fi:2'
+ designates the second argument of the most recent command starting
+ with the letters `fi'.
-`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.
+ Here are the word designators:
-`tilde-expand (M-~)'
- Perform tilde expansion on the current word.
+`0 (zero)'
+ The `0'th word. For many applications, this is the command word.
-`set-mark (C-@)'
- Set the mark to the current point. If a numeric argument is
- supplied, the mark is set to that position.
+`N'
+ The Nth word.
-`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 first argument; that is, word 1.
-`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.
+`$'
+ The last argument.
-`character-search-backward (M-C-])'
- A character is read and point is moved to the previous occurrence
- of that character. A negative count searches for subsequent
- occurrences.
+`%'
+ The word matched by the most recent `?STRING?' search.
-`insert-comment (M-#)'
- The value of the `comment-begin' variable is inserted at the
- beginning of the current line, and the line is accepted as if a
- newline had been typed. This makes the current line a shell
- comment.
+`X-Y'
+ A range of words; `-Y' abbreviates `0-Y'.
-`dump-functions ()'
- Print all of the functions and their key bindings to the Readline
- output stream. If a numeric argument is supplied, the output is
- formatted in such a way that it can be made part of an INPUTRC
- file. This command is unbound by default.
+`*'
+ All of the words, except the `0'th. This is a synonym for `1-$'.
+ It is not an error to use `*' if there is just one word in the
+ event; the empty string is returned in that case.
-`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.
+`X*'
+ Abbreviates `X-$'
-`dump-macros ()'
- Print all of the Readline key sequences bound to macros and the
- strings they ouput. If a numeric argument is supplied, the output
- is formatted in such a way that it can be made part of an INPUTRC
- file. This command is unbound by default.
+`X-'
+ Abbreviates `X-$' like `X*', but omits the last word.
-`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.
-`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 word designator is supplied without an event specification, the
+previous command is used as the event.
-`display-shell-version (C-x C-v)'
- Display version information about the current instance of Bash.
+\1f
+File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
-`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::.).
+9.3.3 Modifiers
+---------------
-`history-expand-line (M-^)'
- Perform history expansion on the current line.
+After the optional word designator, you can add a sequence of one or
+more of the following modifiers, each preceded by a `:'.
-`magic-space ()'
- Perform history expansion on the current line and insert a space
- (*note History Interaction::.).
+`h'
+ Remove a trailing pathname component, leaving only the head.
-`alias-expand-line ()'
- Perform alias expansion on the current line (*note Aliases::.).
+`t'
+ Remove all leading pathname components, leaving the tail.
-`history-and-alias-expand-line ()'
- Perform history and alias expansion on the current line.
+`r'
+ Remove a trailing suffix of the form `.SUFFIX', leaving the
+ basename.
-`insert-last-argument (M-., M-_)'
- A synonym for `yank-last-arg'.
+`e'
+ Remove all but the trailing suffix.
-`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.
+`p'
+ Print the new command but do not execute it.
-`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.
+`q'
+ Quote the substituted words, escaping further substitutions.
-\1f
-File: bashref.info, Node: Readline vi Mode, Prev: Bindable Readline Commands, Up: Command Line Editing
+`x'
+ Quote the substituted words as with `q', but break into words at
+ spaces, tabs, and newlines.
-Readline vi Mode
-================
+`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.
- 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.
+`&'
+ Repeat the previous substitution.
- 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'
+`a'
+ Cause changes to be applied over the entire event line. Used in
+ conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
+
+`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
-MS-DOS, 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 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 2.10 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', `make install' will
-use `PATH' as the prefix for installing programs and libraries.
+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 Bash will run
+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 Bash. There are also
-several `--with-PACKAGE' options, where PACKAGE is something like
-`gnu-malloc' or `purify'. To turn off the default use of a package, use
+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'.
`--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 not the version of `malloc' that appears in glibc version
- 2, but a modified version of the `malloc' from glibc version 1.
- This is somewhat slower than the default `malloc', but wastes less
- space on a per-allocation basis, and will return memory to the
- operating system under some circumstances.
-
`--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 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.
+ 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
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.
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 (*note Aliases::.).
+ 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 (*note
- Arrays::.).
+ Arrays::).
`--enable-bang-history'
Include support for `csh'-like history substitution (*note History
- Interaction::.).
+ Interaction::).
`--enable-brace-expansion'
Include `csh'-like brace expansion ( `b{a,b}c' ==> `bac bbc' ).
- See *Note Brace Expansion::, for a complete description.
+ 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::.).
+ 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 (*note The Directory Stack::.).
+ `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 `((...))' command (*note Conditional
- Constructs::.).
+ Constructs::).
`--enable-extended-glob'
Include support for the extended pattern matching features
- described above under *Note Pattern Matching::.
+ described above under *note Pattern Matching::.
+
+`--enable-extended-glob-default'
+ Set the default value of the EXTGLOB shell option described above
+ under *note The Shopt Builtin:: to be enabled.
`--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 the job control features (*note Job Control::.), if
+ 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 operating system 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. See *Note Printing a Prompt::, for a complete list of
+ 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 (*note Command Line Editing::.).
+ 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 `select' builtin, which allows the generation of simple
- menus (*note Conditional Constructs::.).
+ Include the `select' compound command, 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/gnu/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
`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@po.CWRU.Edu>.
+ Please send all reports concerning this manual to
+<chet.ramey@case.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 1.3, 3 November 2008
+
+ Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+ `http://fsf.org/'
+
+ 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
+ modifications and/or translated into another language.
+
+ 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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+ the notice that says that the Document is released under this
+ License. If a section does not fit the above definition of
+ Secondary then it is not allowed to be designated as Invariant.
+ The Document may contain zero Invariant Sections. If the Document
+ does not identify any Invariant Sections then there are none.
+
+ The "Cover Texts" are certain short passages of text that are
+ listed, as Front-Cover Texts or Back-Cover Texts, in the notice
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+
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+
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+
+ The "Title Page" means, for a printed book, the title page itself,
+ plus such following pages as are needed to hold, legibly, the
+ material this License requires to appear in the title page. For
+ works in formats which do not have any title page as such, "Title
+ Page" means the text near the most prominent appearance of the
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+
+ The "publisher" means any person or entity that distributes copies
+ of the Document to the public.
+
+ A section "Entitled XYZ" means a named subunit of the Document
+ whose title either is precisely XYZ or contains XYZ in parentheses
+ following text that translates XYZ in another language. (Here XYZ
+ stands for a specific section name mentioned below, such as
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+ 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
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+ 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 under this License. Any attempt
+ otherwise to copy, modify, sublicense, or distribute it is void,
+ and will automatically terminate your rights under this License.
+
+ However, if you cease all violation of this License, then your
+ license from a particular copyright holder is reinstated (a)
+ provisionally, unless and until the copyright holder explicitly
+ and finally terminates your license, and (b) permanently, if the
+ copyright holder fails to notify you of the violation by some
+ reasonable means prior to 60 days after the cessation.
+
+ Moreover, your license from a particular copyright holder is
+ reinstated permanently if the copyright holder notifies you of the
+ violation by some reasonable means, this is the first time you have
+ received notice of violation of this License (for any work) from
+ that copyright holder, and you cure the violation prior to 30 days
+ after your receipt of the notice.
+
+ Termination of your rights under this section does not terminate
+ the licenses of parties who have received copies or rights from
+ you under this License. If your rights have been terminated and
+ not permanently reinstated, receipt of a copy of some or all of
+ the same material does not give you any rights to use it.
+
+ 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. If the Document specifies that a proxy
+ can decide which future versions of this License can be used, that
+ proxy's public statement of acceptance of a version permanently
+ authorizes you to choose that version for the Document.
+
+ 11. RELICENSING
+
+ "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
+ World Wide Web server that publishes copyrightable works and also
+ provides prominent facilities for anybody to edit those works. A
+ public wiki that anybody can edit is an example of such a server.
+ A "Massive Multiauthor Collaboration" (or "MMC") contained in the
+ site means any set of copyrightable works thus published on the MMC
+ site.
+
+ "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
+ license published by Creative Commons Corporation, a not-for-profit
+ corporation with a principal place of business in San Francisco,
+ California, as well as future copyleft versions of that license
+ published by that same organization.
+
+ "Incorporate" means to publish or republish a Document, in whole or
+ in part, as part of another Document.
+
+ An MMC is "eligible for relicensing" if it is licensed under this
+ License, and if all works that were first published under this
+ License somewhere other than this MMC, and subsequently
+ incorporated in whole or in part into the MMC, (1) had no cover
+ texts or invariant sections, and (2) were thus incorporated prior
+ to November 1, 2008.
+
+ The operator of an MMC Site may republish an MMC contained in the
+ site under CC-BY-SA on the same site at any time before August 1,
+ 2009, provided the MMC is eligible for relicensing.
+
+
+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 1.3
+ 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.
+ (line 16)
* :: Bourne Shell Builtins.
+ (line 11)
* [: Bourne Shell Builtins.
-* alias: Alias Builtins.
+ (line 217)
+* alias: Bash Builtins. (line 11)
* bg: Job Control Builtins.
-* bind: Bash Builtins.
+ (line 7)
+* bind: Bash Builtins. (line 21)
* break: Bourne Shell Builtins.
-* builtin: Bash Builtins.
+ (line 29)
+* builtin: Bash Builtins. (line 98)
+* caller: Bash Builtins. (line 106)
* cd: Bourne Shell Builtins.
-* command: Bash 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 217)
* continue: Bourne Shell Builtins.
-* declare: Bash Builtins.
-* dirs: The Directory Stack.
+ (line 58)
+* declare: Bash Builtins. (line 142)
+* dirs: Directory Stack Builtins.
+ (line 7)
* disown: Job Control Builtins.
-* echo: Bash Builtins.
-* enable: Bash Builtins.
+ (line 83)
+* echo: Bash Builtins. (line 226)
+* enable: Bash Builtins. (line 287)
* eval: Bourne Shell Builtins.
+ (line 66)
* exec: Bourne Shell Builtins.
+ (line 73)
* exit: Bourne Shell Builtins.
+ (line 85)
* export: Bourne Shell Builtins.
+ (line 91)
* fc: Bash History Builtins.
+ (line 10)
* fg: Job Control Builtins.
+ (line 16)
* getopts: Bourne Shell Builtins.
+ (line 106)
* hash: Bourne Shell Builtins.
-* help: Bash Builtins.
+ (line 148)
+* help: Bash Builtins. (line 315)
* history: Bash History Builtins.
+ (line 39)
* jobs: Job Control Builtins.
+ (line 25)
* kill: Job Control Builtins.
-* let: Bash Builtins.
-* local: Bash Builtins.
-* logout: Bash Builtins.
-* popd: The Directory Stack.
-* printf: Bash Builtins.
-* pushd: The Directory Stack.
+ (line 57)
+* let: Bash Builtins. (line 335)
+* local: Bash Builtins. (line 342)
+* logout: Bash Builtins. (line 352)
+* mapfile: Bash Builtins. (line 356)
+* popd: Directory Stack Builtins.
+ (line 37)
+* printf: Bash Builtins. (line 402)
+* pushd: Directory Stack Builtins.
+ (line 58)
* pwd: Bourne Shell Builtins.
-* read: Bash Builtins.
+ (line 167)
+* read: Bash Builtins. (line 447)
+* readarray: Bash Builtins. (line 527)
* readonly: Bourne Shell Builtins.
+ (line 176)
* return: Bourne Shell Builtins.
-* set: The Set Builtin.
+ (line 192)
+* set: The Set Builtin. (line 11)
* shift: Bourne Shell Builtins.
-* shopt: Bash Builtins.
-* source: Bash Builtins.
+ (line 205)
+* shopt: The Shopt Builtin. (line 9)
+* source: Bash Builtins. (line 535)
* suspend: Job Control Builtins.
+ (line 94)
* test: Bourne Shell Builtins.
+ (line 217)
* times: Bourne Shell Builtins.
+ (line 290)
* trap: Bourne Shell Builtins.
-* type: Bash Builtins.
-* typeset: Bash Builtins.
-* ulimit: Bash Builtins.
+ (line 295)
+* type: Bash Builtins. (line 539)
+* typeset: Bash Builtins. (line 570)
+* ulimit: Bash Builtins. (line 576)
* umask: Bourne Shell Builtins.
-* unalias: Alias Builtins.
+ (line 341)
+* unalias: Bash Builtins. (line 665)
* unset: Bourne Shell Builtins.
+ (line 358)
* wait: Job Control Builtins.
+ (line 73)
\1f
-File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Top
+File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Indexes
-Shell Reserved Words
-********************
+D.2 Index of Shell Reserved Words
+=================================
+\0\b[index\0\b]
* Menu:
-* !: Pipelines.
+* !: Pipelines. (line 9)
* [[: Conditional Constructs.
+ (line 117)
* ]]: Conditional Constructs.
+ (line 117)
* case: Conditional Constructs.
-* do: Looping Constructs.
-* done: Looping 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.
-* for: Looping Constructs.
-* function: Shell Functions.
+ (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.
-* time: Pipelines.
-* until: Looping Constructs.
-* while: Looping Constructs.
-* {: Command Grouping.
-* }: Command Grouping.
+ (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: Top
+File: bashref.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Indexes
-Parameter and Variable Index
-****************************
+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.
+* !: 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.
-* BASH: Bash Variables.
-* BASH_ENV: Bash Variables.
-* BASH_VERSINFO: Bash Variables.
-* BASH_VERSION: Bash Variables.
+ (line 6)
+* BASH: Bash Variables. (line 13)
+* BASH_ALIASES: Bash Variables. (line 30)
+* BASH_ARGC: Bash Variables. (line 37)
+* BASH_ARGV: Bash Variables. (line 47)
+* BASH_CMDS: Bash Variables. (line 57)
+* BASH_COMMAND: Bash Variables. (line 64)
+* BASH_ENV: Bash Variables. (line 69)
+* BASH_EXECUTION_STRING: Bash Variables. (line 75)
+* BASH_LINENO: Bash Variables. (line 78)
+* BASH_REMATCH: Bash Variables. (line 86)
+* BASH_SOURCE: Bash Variables. (line 94)
+* BASH_SUBSHELL: Bash Variables. (line 101)
+* BASH_VERSINFO: Bash Variables. (line 105)
+* BASH_VERSION: Bash Variables. (line 129)
+* BASH_XTRACEFD: Bash Variables. (line 132)
+* BASHOPTS: Bash Variables. (line 16)
+* BASHPID: Bash Variables. (line 25)
* 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 143)
* comment-begin: Readline Init File Syntax.
+ (line 50)
+* COMP_CWORD: Bash Variables. (line 148)
+* COMP_KEY: Bash Variables. (line 177)
+* COMP_LINE: Bash Variables. (line 154)
+* COMP_POINT: Bash Variables. (line 159)
+* COMP_TYPE: Bash Variables. (line 167)
+* COMP_WORDBREAKS: Bash Variables. (line 181)
+* COMP_WORDS: Bash Variables. (line 187)
+* completion-display-width: Readline Init File Syntax.
+ (line 55)
+* completion-ignore-case: Readline Init File Syntax.
+ (line 62)
+* completion-map-case: Readline Init File Syntax.
+ (line 67)
+* completion-prefix-display-length: Readline Init File Syntax.
+ (line 73)
* completion-query-items: Readline Init File Syntax.
+ (line 80)
+* COMPREPLY: Bash Variables. (line 195)
* convert-meta: Readline Init File Syntax.
-* DIRSTACK: Bash Variables.
+ (line 90)
+* COPROC: Bash Variables. (line 200)
+* DIRSTACK: Bash Variables. (line 204)
* disable-completion: Readline Init File Syntax.
+ (line 96)
* editing-mode: Readline Init File Syntax.
+ (line 101)
+* EMACS: Bash Variables. (line 214)
* enable-keypad: Readline Init File Syntax.
-* EUID: Bash Variables.
+ (line 112)
+* ENV: Bash Variables. (line 219)
+* EUID: Bash Variables. (line 223)
* expand-tilde: Readline Init File Syntax.
-* FCEDIT: Bash 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.
+ (line 123)
+* FCEDIT: Bash Variables. (line 227)
+* FIGNORE: Bash Variables. (line 231)
+* FUNCNAME: Bash Variables. (line 237)
+* FUNCNEST: Bash Variables. (line 255)
+* GLOBIGNORE: Bash Variables. (line 260)
+* GROUPS: Bash Variables. (line 266)
+* histchars: Bash Variables. (line 272)
+* HISTCMD: Bash Variables. (line 287)
+* HISTCONTROL: Bash Variables. (line 292)
+* HISTFILE: Bash Variables. (line 308)
+* HISTFILESIZE: Bash Variables. (line 312)
+* HISTIGNORE: Bash Variables. (line 320)
+* history-preserve-point: Readline Init File Syntax.
+ (line 127)
+* history-size: Readline Init File Syntax.
+ (line 133)
+* HISTSIZE: Bash Variables. (line 339)
+* HISTTIMEFORMAT: Bash Variables. (line 343)
* HOME: Bourne Shell Variables.
+ (line 13)
* horizontal-scroll-mode: Readline Init File Syntax.
-* HOSTFILE: Bash Variables.
-* HOSTNAME: Bash Variables.
-* HOSTTYPE: Bash Variables.
+ (line 138)
+* HOSTFILE: Bash Variables. (line 352)
+* HOSTNAME: Bash Variables. (line 363)
+* HOSTTYPE: Bash Variables. (line 366)
* IFS: Bourne Shell Variables.
-* IGNOREEOF: Bash Variables.
+ (line 18)
+* IGNOREEOF: Bash Variables. (line 369)
* input-meta: Readline Init File Syntax.
-* INPUTRC: Bash Variables.
+ (line 145)
+* INPUTRC: Bash Variables. (line 379)
+* isearch-terminators: Readline Init File Syntax.
+ (line 152)
* keymap: Readline Init File Syntax.
-* LANG: Bash Variables.
-* LC_ALL: Bash Variables.
-* LC_COLLATE: Bash Variables.
-* LC_CTYPE: Bash Variables.
-* LC_MESSAGES: Bash Variables.
-* LINENO: Bash Variables.
-* MACHTYPE: Bash Variables.
+ (line 159)
+* LANG: Bash Variables. (line 383)
+* LC_ALL: Bash Variables. (line 387)
+* LC_COLLATE: Bash Variables. (line 391)
+* LC_CTYPE: Bash Variables. (line 398)
+* LC_MESSAGES <1>: Locale Translation. (line 11)
+* LC_MESSAGES: Bash Variables. (line 403)
+* LC_NUMERIC: Bash Variables. (line 407)
+* LINENO: Bash Variables. (line 411)
+* LINES: Bash Variables. (line 415)
+* MACHTYPE: Bash Variables. (line 420)
* MAIL: Bourne Shell Variables.
-* MAILCHECK: Bash Variables.
+ (line 22)
+* MAILCHECK: Bash Variables. (line 424)
* MAILPATH: Bourne Shell Variables.
+ (line 27)
+* MAPFILE: Bash Variables. (line 432)
* mark-modified-lines: Readline Init File Syntax.
+ (line 172)
+* mark-symlinked-directories: Readline Init File Syntax.
+ (line 177)
+* match-hidden-files: Readline Init File Syntax.
+ (line 182)
+* menu-complete-display-prefix: Readline Init File Syntax.
+ (line 189)
* meta-flag: Readline Init File Syntax.
-* OLDPWD: Bash Variables.
+ (line 145)
+* OLDPWD: Bash Variables. (line 436)
* OPTARG: Bourne Shell Variables.
-* OPTERR: Bash Variables.
+ (line 34)
+* OPTERR: Bash Variables. (line 439)
* OPTIND: Bourne Shell Variables.
-* OSTYPE: Bash Variables.
+ (line 38)
+* OSTYPE: Bash Variables. (line 443)
* output-meta: Readline Init File Syntax.
+ (line 194)
+* page-completions: Readline Init File Syntax.
+ (line 199)
* PATH: Bourne Shell Variables.
-* PIPESTATUS: Bash Variables.
-* PPID: Bash Variables.
-* PROMPT_COMMAND: Bash Variables.
+ (line 42)
+* PIPESTATUS: Bash Variables. (line 446)
+* POSIXLY_CORRECT: Bash Variables. (line 451)
+* PPID: Bash Variables. (line 460)
+* PROMPT_COMMAND: Bash Variables. (line 464)
+* PROMPT_DIRTRIM: Bash Variables. (line 468)
* PS1: Bourne Shell Variables.
+ (line 48)
* PS2: Bourne Shell Variables.
-* PS3: Bash Variables.
-* PS4: Bash Variables.
-* PWD: Bash Variables.
-* RANDOM: Bash Variables.
-* REPLY: Bash Variables.
-* SECONDS: Bash Variables.
-* SHELLOPTS: Bash Variables.
-* SHLVL: Bash Variables.
+ (line 53)
+* PS3: Bash Variables. (line 474)
+* PS4: Bash Variables. (line 479)
+* PWD: Bash Variables. (line 485)
+* RANDOM: Bash Variables. (line 488)
+* READLINE_LINE: Bash Variables. (line 493)
+* READLINE_POINT: Bash Variables. (line 497)
+* REPLY: Bash Variables. (line 501)
+* revert-all-at-newline: Readline Init File Syntax.
+ (line 209)
+* SECONDS: Bash Variables. (line 504)
+* SHELL: Bash Variables. (line 510)
+* SHELLOPTS: Bash Variables. (line 515)
+* SHLVL: Bash Variables. (line 524)
* show-all-if-ambiguous: Readline Init File Syntax.
-* TIMEFORMAT: Bash Variables.
-* TMOUT: Bash Variables.
-* UID: Bash Variables.
+ (line 215)
+* show-all-if-unmodified: Readline Init File Syntax.
+ (line 221)
+* skip-completed-text: Readline Init File Syntax.
+ (line 230)
+* TEXTDOMAIN: Locale Translation. (line 11)
+* TEXTDOMAINDIR: Locale Translation. (line 11)
+* TIMEFORMAT: Bash Variables. (line 529)
+* TMOUT: Bash Variables. (line 567)
+* TMPDIR: Bash Variables. (line 579)
+* UID: Bash Variables. (line 583)
* visible-stats: Readline Init File Syntax.
+ (line 243)
\1f
-File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Top
+File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Indexes
-Function Index
-**************
+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.
+ (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.
-* 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.
+ (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 43)
+* 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.
+ (line 14)
+* downcase-word (M-l): Commands For Text. (line 42)
* dump-functions (): Miscellaneous Commands.
+ (line 73)
* dump-macros (): Miscellaneous Commands.
+ (line 85)
* 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.
+ (line 79)
+* 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.
-* 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.
+ (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 60)
* 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.
+ (line 22)
+* 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.
-* next-history (C-n): Commands For History.
+ (line 26)
+* menu-complete-backward (): Commands For Completion.
+ (line 38)
+* 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.
+ (line 36)
+* overwrite-mode (): Commands For Text. (line 50)
* 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.
+ (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.
-* redraw-current-line (): Commands For Moving.
-* reverse-search-history (C-r): Commands For History.
+ (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.
-* self-insert (a, b, A, 1, !, ...): Commands For Text.
+ (line 25)
+* self-insert (a, b, A, 1, !, ...): Commands For Text. (line 24)
* set-mark (C-@): Miscellaneous Commands.
-* start-kbd-macro (C-x (): Keyboard Macros.
-* 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 32)
+* skip-csi-sequence (): Miscellaneous Commands.
+ (line 51)
+* 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: Shell Arithmetic.
+* alias expansion: Aliases. (line 6)
+* arithmetic evaluation: Shell Arithmetic. (line 6)
* arithmetic expansion: Arithmetic Expansion.
-* arithmetic, shell: Shell Arithmetic.
-* arrays: Arrays.
-* background: Job Control Basics.
-* Bash configuration: Basic Installation.
-* Bash installation: Basic Installation.
+ (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.
-* brace expansion: Brace Expansion.
-* builtin: Definitions.
+ (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.
-* command timing: Pipelines.
+ (line 6)
+* command timing: Pipelines. (line 9)
+* commands, compound: Compound Commands. (line 6)
* commands, conditional: Conditional Constructs.
-* commands, grouping: Command Grouping.
-* commands, lists: Lists.
-* commands, looping: Looping Constructs.
-* commands, pipelines: Pipelines.
-* commands, shell: Shell Commands.
-* commands, simple: Simple Commands.
-* comments, shell: Comments.
-* configuration: Basic Installation.
-* control operator: Definitions.
-* directory stack: The Directory Stack.
+ (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.
-* environment: Environment.
-* evaluation, arithmetic: Shell Arithmetic.
-* event designators: Event Designators.
+ (line 6)
+* environment: Environment. (line 6)
+* evaluation, arithmetic: Shell Arithmetic. (line 6)
+* event designators: Event Designators. (line 6)
* execution environment: Command Execution Environment.
-* exit status <1>: Exit Status.
-* exit status: Definitions.
-* expansion: Shell Expansions.
+ (line 6)
+* exit status <1>: Exit Status. (line 6)
+* exit status: Definitions. (line 26)
+* expansion: Shell Expansions. (line 6)
* expansion, arithmetic: Arithmetic Expansion.
-* expansion, brace: Brace Expansion.
-* expansion, filename: Filename Expansion.
+ (line 6)
+* expansion, brace: Brace Expansion. (line 6)
+* expansion, filename: Filename Expansion. (line 9)
* expansion, parameter: Shell Parameter Expansion.
-* expansion, pathname: Filename Expansion.
-* expansion, tilde: Tilde Expansion.
-* expressions, arithmetic: Shell Arithmetic.
+ (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.
-* field: Definitions.
-* filename: Definitions.
-* filename expansion: Filename Expansion.
-* foreground: Job Control Basics.
-* functions, shell: Shell Functions.
+ (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.
-* history events: Event Designators.
-* history expansion: History Interaction.
+ (line 6)
+* history events: Event Designators. (line 8)
+* history expansion: History Interaction. (line 6)
* history list: Bash History Facilities.
-* History, how to use: Job Control Variables.
-* identifier: Definitions.
-* initialization file, readline: Readline Init File.
-* installation: Basic Installation.
+ (line 6)
+* History, how to use: Programmable Completion Builtins.
+ (line 237)
+* identifier: Definitions. (line 51)
+* initialization file, readline: Readline Init File. (line 6)
+* installation: Basic Installation. (line 6)
* 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.
+ (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.
-* localization: Locale Translation.
-* matching, pattern: Pattern Matching.
-* metacharacter: Definitions.
-* name: Definitions.
+ (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.
-* operator, shell: Definitions.
+ (line 6)
+* operator, shell: Definitions. (line 57)
* parameter expansion: Shell Parameter Expansion.
-* parameters: Shell Parameters.
+ (line 6)
+* parameters: Shell Parameters. (line 6)
* parameters, positional: Positional Parameters.
-* parameters, special: Special Parameters.
-* pathname expansion: Filename Expansion.
-* pattern matching: Pattern Matching.
-* pipeline: Pipelines.
-* POSIX: Definitions.
-* POSIX Mode: Bash POSIX Mode.
-* process group: Definitions.
-* process group ID: Definitions.
+ (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.
-* prompting: Printing a Prompt.
-* quoting: Quoting.
-* quoting, ANSI: ANSI-C Quoting.
-* Readline, how to use: Modifiers.
-* redirection: Redirections.
-* reserved word: Definitions.
+ (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.
-* return status: Definitions.
-* shell arithmetic: Shell Arithmetic.
-* 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.
+ (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\7f1197
-Node: Introduction\7f3153
-Node: What is Bash?\7f3378
-Node: What is a shell?\7f4472
-Node: Definitions\7f6494
-Node: Basic Shell Features\7f9155
-Node: Shell Syntax\7f10378
-Node: Shell Operation\7f10667
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-Node: Escape Character\7f12986
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-Node: Concept Index\7f275885
+Node: Top\7f1346
+Node: Introduction\7f3185
+Node: What is Bash?\7f3413
+Node: What is a shell?\7f4526
+Node: Definitions\7f7066
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+Node: Escape Character\7f14830
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+Node: Command Line Editing\7f259179
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+Node: Readline Killing Commands\7f266313
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+Node: Readline Init File\7f271463
+Node: Readline Init File Syntax\7f272610
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+Node: GNU Free Documentation License\7f384759
+Node: Indexes\7f409955
+Node: Builtin Index\7f410409
+Node: Reserved Word Index\7f417236
+Node: Variable Index\7f419684
+Node: Function Index\7f432779
+Node: Concept Index\7f439788
\1f
End Tag Table
projects / platform / upstream / bash.git / blobdiff