-This is bashref.info, produced by makeinfo version 4.0 from
+This is bashref.info, produced by makeinfo version 4.13 from
/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 text is a brief description of the features that are present in
-the Bash shell.
+the Bash shell (version 4.3, 2 February 2014).
-This is Edition 2.5, last updated 28 Mar 2001,
-of `The GNU Bash Reference Manual',
-for `Bash', Version 2.05.
+ This is Edition 4.3, last updated 2 February 2014, of `The GNU Bash
+Reference Manual', for `Bash', Version 4.3.
-Copyright (C) 1991-1999 Free Software Foundation, Inc.
+ Copyright (C) 1988-2014 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 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".
-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 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.
+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 2.5, last updated 28 Mar 2001, of `The GNU Bash
-Reference Manual', for `Bash', Version 2.05.
+This text is a brief description of the features that are present in
+the Bash shell (version 4.3, 2 February 2014). The Bash home page is
+`http://www.gnu.org/software/bash/'.
- Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
+ This is Edition 4.3, last updated 2 February 2014, of `The GNU Bash
+Reference Manual', for `Bash', Version 4.3.
Bash contains features that appear in other popular shells, and some
features that only appear in Bash. Some of the shells that Bash has
borrowed concepts from are the Bourne Shell (`sh'), the Korn Shell
-(`ksh'), and the C-shell (`csh' and its successor, `tcsh'). The
-following menu breaks the features up into categories based upon which
-one of these other shells inspired the feature.
+(`ksh'), and the C-shell (`csh' and its successor, `tcsh'). The
+following menu breaks the features up into categories, noting which
+features were inspired by other shells and which are specific to Bash.
This manual is meant as a brief introduction to features found in
Bash. The Bash manual page should be used as the definitive reference
* Menu:
* Introduction:: An introduction to the shell.
-
* Definitions:: Some definitions used in the rest of this
manual.
-
* Basic Shell Features:: The shell "building blocks".
-
* 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.
-
* Major Differences From The Bourne Shell:: A terse list of the differences
between Bash and historical
versions of /bin/sh.
-
-* 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.
+* GNU Free Documentation License:: Copying and sharing this documentation.
+* Indexes:: Various indexes for this manual.
\1f
File: bashref.info, Node: Introduction, Next: Definitions, Prev: Top, Up: Top
-Introduction
-************
+1 Introduction
+**************
* Menu:
* What is Bash?:: A short description of Bash.
-
* What is a shell?:: A brief introduction to shells.
\1f
File: bashref.info, Node: What is Bash?, Next: What is a shell?, Up: Introduction
-What is Bash?
-=============
+1.1 What is Bash?
+=================
- Bash is the shell, or command language interpreter, for the GNU
+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 `/bin/sh', which appeared in the Seventh Edition
-Bell Labs Research version of Unix.
+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 specification (IEEE Working Group 1003.2). It offers functional
-improvements over `sh' for both interactive and programming use.
+Tools portion of the IEEE POSIX specification (IEEE Standard 1003.1).
+It offers functional improvements over `sh' for both interactive and
+programming use.
While the GNU operating system 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, Windows 95/98, and Windows NT.
+exist for MS-DOS, OS/2, and Windows platforms.
\1f
File: bashref.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
-What is a shell?
-================
+1.2 What is a shell?
+====================
- At its base, a shell is simply a macro processor that executes
-commands. A Unix shell is both a command interpreter, which provides
-the user interface to the rich set of GNU utilities, and a programming
-language, allowing these utilitites to be combined. Files containing
+At its base, a shell is simply a macro processor that executes
+commands. The term macro processor means functionality where text and
+symbols are expanded to create larger expressions.
+
+ A Unix shell is both a command interpreter and a programming
+language. As a command interpreter, the shell provides the user
+interface to the rich set of GNU utilities. The programming language
+features allow these utilities to be combined. Files containing
commands can be created, and become commands themselves. These new
commands have the same status as system commands in directories such as
-`/bin', allowing users or groups to establish custom environments.
+`/bin', allowing users or groups to establish custom environments to
+automate their common tasks.
+
+ Shells may be used interactively or non-interactively. In
+interactive mode, they accept input typed from the keyboard. When
+executing non-interactively, shells execute commands read from a file.
A shell allows execution of GNU commands, both synchronously and
asynchronously. The shell waits for synchronous commands to complete
in parallel with the shell while it reads and executes additional
commands. The "redirection" constructs permit fine-grained control of
the input and output of those commands. Moreover, the shell allows
-control over the contents of commands' environments. Shells may be
-used interactively or non-interactively: they accept input typed from
-the keyboard or from a file.
+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.
+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.
Shells offer 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.
+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'
`special builtin'
A shell builtin command that has been classified as special by the
- POSIX 1003.2 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: 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
\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
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::).
\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
Each of the shell metacharacters (*note Definitions::) has special
meaning to the shell and must be quoted if it is to represent itself.
-When the command history expansion facilities are being used, 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.
+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
+Enclosing characters in single quotes (`'') preserves the literal value
+of each character within the quotes. A single quote may not occur
between single quotes, even when preceded by a backslash.
\1f
File: bashref.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
-Double Quotes
-.............
+3.1.2.3 Double Quotes
+.....................
- Enclosing characters in double quotes (`"') preserves the literal
-value of all characters within the quotes, with the exception of `$',
-``', and `\'. The characters `$' and ``' retain their special meaning
-within double quotes (*note Shell Expansions::). The backslash retains
-its special meaning only when followed by one of the following
-characters: `$', ``', `"', `\', or `newline'. Within double quotes,
-backslashes that are followed by one of these characters are removed.
-Backslashes preceding characters without a special meaning are left
-unmodified. A double quote may be quoted within double quotes by
-preceding it with a backslash.
+Enclosing characters in double quotes (`"') preserves the literal value
+of all characters within the quotes, with the exception of `$', ``',
+`\', 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::).
\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 `$'STRING'' are treated specially. The word
-expands to STRING, with backslash-escaped characters replaced as
-specified by the ANSI C standard. Backslash escape sequences, if
-present, are decoded as follows:
+Words of the form `$'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'
`\''
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)
+
+`\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.
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 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
+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
* 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
+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.
\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 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.
-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.
+ If `|&' is used, COMMAND1's standard error, in addition to its
+standard output, is connected to COMMAND2's standard input through the
+pipe; it is shorthand for `2>&1 |'. This implicit redirection of the
+standard error to the standard output 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.
+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.
+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
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
+ AND and OR lists are sequences of one or more pipelines separated by
+the control operators `&&' and `||', respectively. AND and OR lists
+are executed with left associativity.
+
+ An AND list has the form
COMMAND1 && COMMAND2
COMMAND2 is executed if, and only if, COMMAND1 returns an exit status
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.
+
+ In most cases a list of commands in a compound command's description
+may be separated from the rest of the command by one or more newlines,
+and may be followed by a newline in place of a semicolon.
+
+ Bash provides looping constructs, conditional commands, and
+mechanisms to group commands and execute them as a unit.
+
+\1f
+File: bashref.info, Node: Looping Constructs, Next: Conditional Constructs, Up: Compound Commands
+
+3.2.4.1 Looping Constructs
+..........................
- Bash supports the following looping constructs.
+Bash supports the following looping constructs.
Note that wherever a `;' appears in the description of a command's
syntax, it may be replaced with one or more newlines.
`until'
The syntax of the `until' command is:
+
until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
status which is not zero. The return status is the exit status of
the last command executed in CONSEQUENT-COMMANDS, or zero if none
`while'
The syntax of the `while' command is:
+
while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
`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, the `for' command executes the COMMANDS
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
COMMANDS are executed and the arithmetic expression EXPR3 is
evaluated. If any expression is omitted, it behaves as if it
evaluates to 1. The return value is the exit status of the last
- command in LIST that is executed, or false if any of the
+ 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'
The syntax of the `case' command is:
- `case WORD in [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]... esac'
+ 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. It's a common idiom
+ to use `*' as the final pattern to define the default case, since
+ that pattern will always match.
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 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::, as if the
+ `extglob' shell option were enabled. The `=' operator is
+ identical to `=='. 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 the quoted portion 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 the quoted portion to be matched as a string. Bracket
+ expressions in regular expressions must be treated carefully,
+ since normal quoting characters lose their meanings between
+ brackets. If the pattern is stored in a shell variable, quoting
+ the variable expansion forces the entire pattern 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.
+
+ For example, the following will match a line (stored in the shell
+ variable LINE) if there is a sequence of characters in the value
+ consisting of any number, including zero, of space characters,
+ zero or one instances of `a', then a `b':
+ [[ $line =~ [[:space:]]*(a)?b ]]
+
+ That means values like `aab' and ` aaaaaab' will match, as will a
+ line containing a `b' anywhere in its value.
+
+ Storing the regular expression in a shell variable is often a
+ useful way to avoid problems with quoting characters that are
+ special to the shell. It is sometimes difficult to specify a
+ regular expression literally without using quotes, or to keep
+ track of the quoting used by regular expressions while paying
+ attention to the shell's quote removal. Using a shell variable to
+ store the pattern decreases these problems. For example, the
+ following is equivalent to the above:
+ pattern='[[:space:]]*(a)?b'
+ [[ $line =~ $pattern ]]
+
+ If you want to match a character that's special to the regular
+ expression grammar, it has to be quoted to remove its special
+ meaning. This means that in the pattern `xxx.txt', the `.'
+ matches any character in the string (its usual regular expression
+ meaning), but in the pattern `"xxx.txt"' it can only match a
+ literal `.'. Shell programmers should take special care with
+ backslashes, since backslashes are used both by the shell and
+ regular expressions to remove the special meaning from the
+ following character. The following two sets of commands are _not_
+ equivalent:
+ pattern='\.'
+
+ [[ . =~ $pattern ]]
+ [[ . =~ \. ]]
+
+ [[ . =~ "$pattern" ]]
+ [[ . =~ '\.' ]]
+
+ The first two matches will succeed, but the second two will not,
+ because in the second two the backslash will be part of the
+ pattern to be matched. In the first two examples, the backslash
+ removes the special meaning from `.', so the literal `.' matches.
+ If the string in the first examples were anything other than `.',
+ say `a', the pattern would not match, because the quoted `.' in the
+ pattern loses its special meaning of matching any single character.
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 `||' commands do not execute EXPRESSION2 if the value
- of EXPRESSION1 is sufficient to determine the return value of the
- entire conditional expression.
+ The `&&' and `||' operators do not evaluate 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 coprocess 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 file descriptors are
+not available in subshells.
+
+ 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.
+
+ Since the coprocess is created as an asynchronous command, the
+`coproc' command always returns success. 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
+------------------
+
+There are ways to run commands in parallel that are not built into Bash.
+GNU Parallel is a tool to do just that.
+
+ 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. GNU Parallel provides shorthand references to many of
+the most common operations (input lines, various portions of the input
+line, different ways to specify the input source, and so on). Parallel
+can replace `xargs' or feed commands from its input sources to several
+different instances of Bash.
+
+ 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 replace `xargs' to gzip all html files in
+the current directory and its subdirectories:
+ find . -type f -name '*.html' -print | parallel gzip
+ If you need to protect special characters such as newlines in file
+names, use find's `-print0' option and parallel's `-0' option.
+
+ 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. While using `ls' will work in most instances, it is not
+sufficient to deal with all filenames. If you need to accommodate
+special characters in filenames, you can use
+
+ find . -depth 1 \! -name '.*' -print0 | parallel -0 mv {} destdir
+
+as alluded to above.
+
+ 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:
+ find . -depth 1 \! -name '.*' -print0 | parallel -0 -X mv {} destdir
+
+ GNU Parallel can replace certain common idioms that operate on lines
+read from a file (in this case, filenames listed one per line):
+ while IFS= read -r x; do
+ do-something1 "$x" "config-$x"
+ do-something2 < "$x"
+ done < file | 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.
+(We use `ls' for brevity here; using `find' as above is more robust in
+the face of filenames containing unexpected characters.) Parallel can
+take arguments from the command line; the above can also be written as
+
+ parallel "zcat {} | bzip2 >{.}.bz2 && rm {}" ::: *.gz
+
+ 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.
+Adding the `-k' option
+ { 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.
+
+ Finally, Parallel can be used to run a sequence of shell commands in
+parallel, similar to `cat file | bash'. It is not uncommon to take a
+list of filenames, create a series of shell commands to operate on
+them, and feed that list of commnds to a shell. Parallel can speed
+this up. Assuming that `file' contains a list of shell commands, one
+per line,
+
+ parallel -j 10 < file
+
+will evaluate the commands using the shell (since no explicit command is
+supplied as an argument), in blocks of ten shell jobs at a time.
+
+\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.
+
+ Functions are declared using this syntax:
+ NAME () COMPOUND-COMMAND [ REDIRECTIONS ]
- 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.
+ 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.
-
- Note that for historical reasons, 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 by whitespace. Also, the
-COMMAND-LIST must be terminated with a semicolon or a newline.
+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. When the shell is in POSIX mode
+(*note Bash POSIX Mode::), NAME may not be the same as one of the
+special builtins (*note Special Builtins::). 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. The `FUNCNAME' variable is set to the name
-of the function while the function is executing.
+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' (`typeset') builtin command (*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. When in POSIX mode (*note Bash POSIX
+Mode::), these builtins may appear in a command after one or more
+instances of the `command' builtin and retain these assignment
+statement properties.
+
+ 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.
+
+ A variable can be assigned the NAMEREF attribute using the `-n'
+option to the \fBdeclare\fP or \fBlocal\fP builtin commands (*note Bash
+Builtins::) to create a NAMEREF, or a reference to another variable.
+This allows variables to be manipulated indirectly. Whenever the
+nameref variable is referenced or assigned to, the operation is
+actually performed on the variable specified by the nameref variable's
+value. A nameref is commonly used within shell functions to refer to a
+variable whose name is passed as an argument to the function. For
+instance, if a variable name is passed to a shell function as its first
+argument, running
+ declare -n ref=$1
+ inside the function creates a nameref variable REF whose value is
+the variable name passed as the first argument. References and
+assignments to REF are treated as references and assignments to the
+variable whose name was passed as `$1'.
+
+ If the control variable in a `for' loop has the nameref attribute,
+the list of words can be a list of shell variables, and a name reference
+will be established for each word in the list, in turn, when the loop is
+executed. Array variables cannot be given the `-n' attribute.
+However, nameref variables can reference array variables and subscripted
+array variables. Namerefs can be unset using the `-n' option to the
+`unset' builtin (*note Bourne Shell Builtins::). Otherwise, if `unset'
+is executed with the name of a nameref variable as an argument, the
+variable referenced by the nameref variable will be unset.
\1f
File: bashref.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
-Positional Parameters
----------------------
+3.4.1 Positional Parameters
+---------------------------
- A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
+A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
other than the single digit `0'. Positional parameters are assigned
from the shell's arguments when it is invoked, and may be reassigned
using the `set' builtin command. Positional parameter `N' may be
\1f
File: bashref.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
-Special Parameters
-------------------
+3.4.2 Special Parameters
+------------------------
- The shell treats several parameters specially. These parameters may
+The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed.
`*'
- Expands to the positional parameters, starting from one. When the
- expansion occurs within double quotes, it expands to a single word
- with the value of each parameter separated by the first character
- of the `IFS' special variable. That is, `"$*"' is equivalent to
- `"$1C$2C..."', where C is the first character of the value of the
- `IFS' variable. If `IFS' is unset, the parameters are separated
- by spaces. If `IFS' is null, the parameters are joined without
- intervening separators.
+ ($*) Expands to the positional parameters, starting from one.
+ When the expansion is not within double quotes, each positional
+ parameter expands to a separate word. In contexts where it is
+ performed, those words are subject to further word splitting and
+ pathname expansion. When the expansion occurs within double
+ quotes, it expands to a single word with the value of each
+ parameter separated by the first character of the `IFS' special
+ variable. That is, `"$*"' is equivalent to `"$1C$2C..."', where C
+ is the first character of the value of the `IFS' variable. If
+ `IFS' is unset, the parameters are separated by spaces. If `IFS'
+ is null, the parameters are joined without intervening separators.
`@'
- Expands to the positional parameters, starting from one. When the
- expansion occurs within double quotes, each parameter expands to a
- separate word. That is, `"$@"' is equivalent to `"$1" "$2" ...'.
- When there are no positional parameters, `"$@"' and `$@' expand to
+ ($@) 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" "$2" ...'. If the double-quoted expansion occurs within a
+ word, the expansion of the first parameter is joined with the
+ beginning part of the original word, and the expansion of the last
+ parameter is joined with the last part of the original word. When
+ there are no positional parameters, `"$@"' and `$@' expand to
nothing (i.e., they are removed).
`#'
- Expands to the number of positional parameters in decimal.
+ ($#) Expands to the number of positional parameters in decimal.
`?'
- Expands to the exit status of the most recently executed foreground
- pipeline.
+ ($?) Expands to the exit status of the most recently executed
+ foreground pipeline.
`-'
- (A hyphen.) Expands to the current option flags as specified upon
- invocation, by the `set' builtin command, or those set by the
+ ($-, a hyphen.) Expands to the current option flags as specified
+ upon invocation, by the `set' builtin command, or those set by the
shell itself (such as the `-i' option).
`$'
- Expands to the process ID of the shell. In a `()' subshell, it
- expands to the process ID of the invoking shell, not the subshell.
+ ($$) Expands to the process ID of the shell. In a `()' subshell,
+ it expands to the process ID of the invoking shell, not the
+ subshell.
`!'
- Expands to the process ID of the most recently executed background
- (asynchronous) command.
+ ($!) Expands to the process ID of the job most recently placed
+ into the background, whether executed as an asynchronous command
+ or using the `bg' builtin (*note Job Control Builtins::).
`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.
+ ($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.
`_'
- (An underscore.) 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
* Quote Removal:: How and when quote characters are removed from
words.
- The order of expansions is: brace expansion, tilde expansion,
-parameter, variable, and arithmetic expansion and command substitution
-(done in a left-to-right fashion), word splitting, and filename
-expansion.
+ The order of expansions is: brace expansion; tilde expansion,
+parameter and variable expansion, arithmetic expansion, and command
+substitution (done in a left-to-right fashion); word splitting; and
+filename expansion.
On systems that can support it, there is an additional expansion
available: PROCESS SUBSTITUTION. This is performed at the same time as
-parameter, variable, and arithmetic expansion and command substitution.
+tilde, parameter, variable, and arithmetic expansion and command
+substitution.
Only brace expansion, word splitting, and filename expansion can
change the number of words of the expansion; other expansions expand a
\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 filenames 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 prefixed
-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 sequence
+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, using
+the default C locale. 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
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
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 filenames 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:
\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
expansion.
The basic form of parameter expansion is ${PARAMETER}. The value of
-PARAMETER is substituted. The braces are required when PARAMETER is a
-positional parameter with more than one digit, or when PARAMETER is
-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
+PARAMETER is substituted. The PARAMETER is a shell parameter as
+described above (*note Shell Parameters::) or an array reference (*note
+Arrays::). The braces are required when PARAMETER is a positional
+parameter with more than one digit, or when PARAMETER is 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 (!), it
+introduces a level of variable indirection. 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 exception to this is the expansion
-of ${!PREFIX*} described below.
+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. Put another way, if the colon is included,
-the operator tests for both existence and that the value is not null;
-if the colon is omitted, the operator tests only for existence.
+ When not performing substring expansion, using the form described
+below (e.g., `:-'), 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
- character specified by OFFSET. If LENGTH is omitted, expands to
- the substring of PARAMETER starting at the character specified by
- OFFSET. LENGTH and OFFSET are arithmetic expressions (*note Shell
- Arithmetic::). This is referred to as Substring Expansion.
+ This is referred to as Substring Expansion. It expands to up to
+ LENGTH characters of the value of PARAMETER starting at the
+ character specified by OFFSET. If PARAMETER is `@', an indexed
+ array subscripted by `@' or `*', or an associative array name, the
+ results differ as described below. If LENGTH is omitted, it
+ expands to the substring of the value of PARAMETER starting at the
+ character specified by OFFSET and extending to the end of the
+ value. LENGTH and OFFSET are arithmetic expressions (*note Shell
+ Arithmetic::).
- 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 in characters from the end of the value of PARAMETER.
+ If LENGTH evaluates to a number less than zero, it is interpreted
+ as an offset in characters from the end of the value of PARAMETER
+ rather than a number of characters, and the expansion is the
+ characters between OFFSET and that result. Note that a negative
+ offset must be separated from the colon by at least one space to
+ avoid being confused with the `:-' expansion.
+
+ Here are some examples illustrating substring expansion on
+ parameters and subscripted arrays:
+
+ $ string=01234567890abcdefgh
+ $ echo ${string:7}
+ 7890abcdefgh
+ $ echo ${string:7:0}
+
+ $ echo ${string:7:2}
+ 78
+ $ echo ${string:7:-2}
+ 7890abcdef
+ $ echo ${string: -7}
+ bcdefgh
+ $ echo ${string: -7:0}
+
+ $ echo ${string: -7:2}
+ bc
+ $ echo ${string: -7:-2}
+ bcdef
+ $ set -- 01234567890abcdefgh
+ $ echo ${1:7}
+ 7890abcdefgh
+ $ echo ${1:7:0}
+
+ $ echo ${1:7:2}
+ 78
+ $ echo ${1:7:-2}
+ 7890abcdef
+ $ echo ${1: -7}
+ bcdefgh
+ $ echo ${1: -7:0}
+
+ $ echo ${1: -7:2}
+ bc
+ $ echo ${1: -7:-2}
+ bcdef
+ $ array[0]=01234567890abcdefgh
+ $ echo ${array[0]:7}
+ 7890abcdefgh
+ $ echo ${array[0]:7:0}
+
+ $ echo ${array[0]:7:2}
+ 78
+ $ echo ${array[0]:7:-2}
+ 7890abcdef
+ $ echo ${array[0]: -7}
+ bcdefgh
+ $ echo ${array[0]: -7:0}
+
+ $ echo ${array[0]: -7:2}
+ bc
+ $ echo ${array[0]: -7:-2}
+ bcdef
+
+ If PARAMETER is `@', the result is LENGTH positional parameters
+ beginning at OFFSET. A negative OFFSET is taken relative to one
+ greater than the greatest positional parameter, so an offset of -1
+ evaluates to the last positional parameter. It is an expansion
+ error if LENGTH evaluates to a number less than zero.
+
+ The following examples illustrate substring expansion using
+ positional parameters:
+
+ $ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${@:7}
+ 7 8 9 0 a b c d e f g h
+ $ echo ${@:7:0}
+
+ $ echo ${@:7:2}
+ 7 8
+ $ echo ${@:7:-2}
+ bash: -2: substring expression < 0
+ $ echo ${@: -7:2}
+ b c
+ $ echo ${@:0}
+ ./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${@:0:2}
+ ./bash 1
+ $ echo ${@: -7:0}
+
+ 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. It is
+ an expansion error if LENGTH evaluates to a number less than zero.
+
+ These examples show how you can use substring expansion with
+ indexed arrays:
+
+ $ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
+ $ echo ${array[@]:7}
+ 7 8 9 0 a b c d e f g h
+ $ echo ${array[@]:7:2}
+ 7 8
+ $ echo ${array[@]: -7:2}
+ b c
+ $ echo ${array[@]: -7:-2}
+ bash: -2: substring expression < 0
+ $ echo ${array[@]:0}
+ 0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${array[@]:0:2}
+ 0 1
+ $ echo ${array[@]: -7:0}
+
+ Substring expansion applied to an associative array produces
+ undefined results.
+
+ 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
substituted. If PARAMETER is `*' or `@', the value substituted is
the number of positional parameters. If PARAMETER is an array
name subscripted by `*' or `@', the value substituted is the
- number of elements in the array.
+ number of elements in the array. If PARAMETER is an indexed array
+ name subscripted by a negative number, that number is interpreted
+ as relative to one greater than the maximum index of PARAMETER, so
+ negative indices count back from the end of the array, and an
+ index of -1 references the last element.
`${PARAMETER#WORD}'
`${PARAMETER##WORD}'
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 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
+ 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
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. Each character in the expanded value of
+ PARAMETER is tested against PATTERN, and, if it matches the
+ pattern, its case is converted. The pattern should not attempt to
+ match more than one character. 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 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
+tokens in the expression undergo parameter and variable expansion,
+command substitution, and quote removal. The result is treated as the
+arithmetic expression to be evaluated. Arithmetic expansions may be
nested.
The evaluation is performed according to the rules listed below
\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. Note that no space may
\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.
+the results of the other expansions into words using these characters
+as field terminators. If `IFS' is unset, or its value is exactly
+`<space><tab><newline>', the 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
\1f
File: bashref.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
-Filename Expansion
-------------------
+3.5.8 Filename Expansion
+------------------------
* Menu:
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
-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.
-
- When a pattern is used for filename generation, the character `.' at
+a PATTERN, and replaced with an alphabetically sorted list of filenames
+matching the pattern (*note Pattern Matching::). If no matching
+filenames 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 `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 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
+matching a filename, 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 hyphen denotes a RANGE EXPRESSION; any character
- that sorts between those two characters, inclusive, using the
+ that falls 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.
+ the current locale and the values of the `LC_COLLATE' and `LC_ALL'
+ shell variables, if set.
For example, in the default C locale, `[a-dx-z]' is equivalent to
`[abcdxyz]'. Many locales sort characters in dictionary order,
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'.
+ value `C', or enable the `globasciiranges' shell option.
Within `[' and `]', CHARACTER CLASSES can be specified using the
syntax `[:'CLASS`:]', where CLASS is one of the following classes
- defined in the POSIX 1003.2 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
-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.
+Before a command is executed, its input and output may be REDIRECTED
+using a special notation interpreted by the shell. Redirection allows
+commands' file handles to be duplicated, opened, closed, made to refer
+to different files, and can change the files the command reads from and
+writes to. Redirection may also be used to modify file handles in 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 `<',
Note that the order of redirections is significant. For example,
the command
ls > DIRLIST 2>&1
-
-directs both standard output (file descriptor 1) and standard error
+ directs both standard output (file descriptor 1) and standard error
(file descriptor 2) to the file DIRLIST, while the command
ls 2>&1 > DIRLIST
-
-directs only the standard output to file DIRLIST, because the standard
-error was duplicated as standard output before the standard output was
-redirected to DIRLIST.
+ directs only the standard output to file DIRLIST, because the
+standard error was 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/tcp/HOST/PORT'
If HOST is a valid hostname or Internet address, and PORT is an
- integer port number, Bash attempts to open a TCP connection to the
- corresponding socket.
+ integer port number or service name, Bash attempts to open the
+ corresponding TCP socket.
`/dev/udp/HOST/PORT'
If HOST is a valid hostname or Internet address, and PORT is an
- integer port number, Bash attempts to open a UDP connection to the
- corresponding socket.
+ integer port number or service name, Bash attempts to open the
+ corresponding UDP socket.
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.
- Redirection of input causes the file whose name results from the
+3.6.1 Redirecting Input
+-----------------------
+
+Redirection of input causes the file whose name results from the
expansion of WORD to be opened for reading on file descriptor `n', or
the standard input (file descriptor 0) if `n' is not specified.
The general format for redirecting input is:
- [n]<WORD
+ [N]<WORD
-Redirecting Output
-------------------
+3.6.2 Redirecting Output
+------------------------
- Redirection of output causes the file whose name results from the
-expansion of WORD to be opened for writing on file descriptor `n', or
-the standard output (file descriptor 1) if `n' is not specified. If
-the file does not exist it is created; if it does exist it is truncated
-to zero size.
+Redirection of output causes the file whose name results from the
+expansion of WORD to be opened for writing on file descriptor N, or the
+standard output (file descriptor 1) if N is not specified. If the file
+does not exist it is created; if it does exist it is truncated to zero
+size.
The general format for redirecting output is:
- [n]>[|]WORD
+ [N]>[|]WORD
If the redirection operator is `>', and the `noclobber' option to
the `set' builtin has been enabled, the redirection will fail if the
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
+ When using the second form, WORD may not expand to a number or `-'.
+If it does, other redirection operators apply (see Duplicating File
+Descriptors below) for compatibility reasons.
-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
+ (see Duplicating File Descriptors below).
+
+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, 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,
+ No parameter and variable 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,
the character sequence `\newline' is ignored, and `\' must be used to
quote the characters `\', `$', and ``'.
DELIMITER. This allows here-documents within shell scripts to be
indented in a natural fashion.
-Duplicating File Descriptors
-----------------------------
+3.6.7 Here Strings
+------------------
- The redirection operator
- [n]<&WORD
+A variant of here documents, the format is:
+ <<< 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
+ The WORD undergoes brace expansion, tilde expansion, parameter and
+variable expansion, command substitution, arithmetic expansion, and
+quote removal. Pathname expansion and word splitting are not performed.
+The result is supplied as a single string to the command on its
+standard input.
+
+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. If WORD evaluates to `-', file descriptor N
+is closed. As a special case, if N is omitted, and WORD does not
+expand to one or more digits or `-', 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
\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 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::)
* 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'.
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
just those that precede the command name.
When Bash invokes an external command, the variable `$_' is set to
-the full path name of the command and passed to that command in its
+the full pathname of the command and passed to that command in its
environment.
\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
\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
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
+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 interactive
-login shell exits.
+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
+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.
+*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
\1f
File: bashref.info, Node: Shell Builtin Commands, Next: Shell Variables, Prev: Basic Shell Features, Up: Top
-Shell Builtin Commands
-**********************
+4 Shell Builtin Commands
+************************
* Menu:
* Bourne Shell Builtins:: Builtin commands inherited from the Bourne
Shell.
* Bash Builtins:: Table of builtins specific to Bash.
-* The Set Builtin:: This builtin is so overloaded it
- deserves its own section.
+* Modifying Shell Behavior:: Builtins to modify shell attributes and
+ optional behavior.
* Special Builtins:: Builtin commands classified specially by
- POSIX.2.
+ 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
implement functionality impossible or inconvenient to obtain with
separate utilities.
- This section briefly 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.
+ 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
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: 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.
`. (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. When Bash is not in
`break'
break [N]
+
Exit from a `for', `while', `until', or `select' loop. If N is
supplied, the Nth enclosing loop is exited. N must be greater
than or equal to 1. The return status is zero unless N is not
greater than or equal to 1.
`cd'
- cd [-LP] [DIRECTORY]
+ cd [-L|[-P [-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.
+ is not supplied, the value of the `HOME' shell variable is used.
+ Any additional arguments following DIRECTORY are ignored. If the
+ shell variable `CDPATH' exists, it is used as a search path: each
+ directory name in `CDPATH' is searched for DIRECTORY, with
+ alternative directory names in `CDPATH' separated by a colon (`:').
+ If DIRECTORY begins with a slash, `CDPATH' is not used.
+
+ The `-P' option means to not follow symbolic links: symbolic links
+ are resolved while `cd' is traversing DIRECTORY and before
+ processing an instance of `..' in DIRECTORY.
+
+ By default, or when the `-L' option is supplied, symbolic links in
+ DIRECTORY are resolved after `cd' processes an instance of `..' in
+ DIRECTORY.
+
+ If `..' appears in DIRECTORY, it is processed by removing the
+ immediately preceding pathname component, back to a slash or the
+ beginning of DIRECTORY.
+
+ 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.
+
+ On systems that support it, the `-@' option presents the extended
+ attributes associated with a file as a directory.
+
+ If DIRECTORY is `-', it is converted to `$OLDPWD' before the
+ directory change is attempted.
+
+ If a non-empty directory name from `CDPATH' is used, or if `-' is
+ the first argument, and the directory change is successful, the
+ absolute pathname of the new working directory is written to the
+ standard output.
+
+ The return status is zero if the directory is successfully changed,
+ non-zero otherwise.
`continue'
continue [N]
+
Resume the next iteration of an enclosing `for', `while', `until',
or `select' loop. If N is supplied, the execution of the Nth
enclosing loop is resumed. N must be greater than or equal to 1.
`eval'
eval [ARGUMENTS]
+
The arguments are concatenated together into a single command,
which is then read and executed, and its exit status returned as
the exit status of `eval'. If there are no arguments or only
`exec'
exec [-cl] [-a NAME] [COMMAND [ARGUMENTS]]
+
If COMMAND is supplied, it replaces the shell without creating a
new process. If the `-l' option is supplied, the shell places a
- dash at the beginning of the zeroth arg passed to COMMAND. This
- is what the `login' program does. The `-c' option causes COMMAND
- to be executed with an empty environment. If `-a' is supplied,
- the shell passes NAME as the zeroth argument to COMMAND. If no
- COMMAND is specified, redirections may be used to affect the
- current shell environment. If there are no redirection errors, the
- return status is zero; otherwise the return status is non-zero.
+ 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 COMMAND cannot be executed for some reason, a non-interactive
+ shell exits, unless the `execfail' shell option is enabled. In
+ that case, it returns failure. An interactive shell returns
+ failure if the file cannot be executed. 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. If
N is omitted, the exit status is that of the last command executed.
Any trap on `EXIT' is executed before the shell terminates.
`export'
export [-fn] [-p] [NAME[=VALUE]]
+
Mark each NAME to be passed to child processes in the environment.
If the `-f' option is supplied, the NAMEs refer to shell
functions; otherwise the names refer to shell variables. The `-n'
option means to no longer mark each NAME for export. If no NAMES
- are supplied, or if the `-p' option is given, a list of exported
- names is displayed. The `-p' option displays output in a form
- that may be reused as input. 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.
+ are supplied, or if the `-p' option is given, a list of names of
+ all exported variables is displayed. The `-p' option displays
+ output in a form that may be reused as input. If a variable name
+ is followed by =VALUE, the value of the variable is set to VALUE.
+
+ The return status is zero unless an invalid option is supplied,
+ one of the names is not a valid shell variable name, or `-f' is
+ supplied with a name that is not a shell function.
`getopts'
getopts OPTSTRING NAME [ARGS]
+
`getopts' is used by shell scripts to parse positional parameters.
OPTSTRING contains the option 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
+ argument, which should be separated from it by whitespace. 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
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.
`getopts' can report errors in two ways. If the first character of
OPTSTRING is a colon, SILENT error reporting is used. In normal
- operation diagnostic messages are printed when invalid options or
+ operation, diagnostic messages are printed when invalid options or
missing option arguments are encountered. If the variable `OPTERR'
is set to 0, no error messages will be displayed, even if the first
character of `optstring' is not a colon.
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 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
current directory or an invalid option is supplied.
`readonly'
- readonly [-apf] [NAME] ...
+ readonly [-aAf] [-p] [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
+ NAME refers to an indexed array variable; the `-A' option means
+ each NAME refers to an associative array variable. If both
+ options are supplied, `-A' takes precedence. If no NAME arguments
+ are given, or if the `-p' option is supplied, a list of all
+ readonly names is printed. The other options may be used to
+ restrict the output to a subset of the set of readonly names. 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. 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 `.' or
- `source'.
+
+ Cause a shell function to stop executing and return the value N to
+ its caller. If N is not supplied, the return value is the exit
+ status of the last command executed in the function. `return' may
+ also be used to terminate execution of a script being executed
+ with the `.' (`source') builtin, returning either N or the exit
+ status of the last command executed within the script as the exit
+ status of the script. If N is supplied, the return value is its
+ least significant 8 bits. 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
+ supplied a non-numeric argument or 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
+ 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::.
+ test EXPR
+
+ Evaluate a conditional express ion EXPR and return a status of 0
+ (true) or 1 (false). Each operator and operand must be a separate
+ argument. Expressions are composed of the primaries described
+ below in *note Bash Conditional Expressions::. `test' does not
+ accept any options, nor does it accept and ignore an argument of
+ `--' as signifying the end of options.
When the `[' form is used, the last argument to the command must
be a `]'.
Expressions may be combined using the following operators, listed
- in decreasing order of precedence.
+ 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.
unary operator, the expression is false.
3 arguments
- If the second argument is one of the binary conditional
+ 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
children. The return status is zero.
`trap'
trap [-lp] [ARG] [SIGSPEC ...]
+
The commands in ARG are to be read and executed when the shell
- receives signal SIGSPEC. If ARG is absent or equal to `-', all
- specified signals are reset to the values they had when the shell
- was started. If ARG is the null string, then the signal specified
- by each SIGSPEC is ignored by the shell and commands it invokes.
- If ARG is 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. 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
+ pipeline (which may consist of a single simple command), a list,
+ or a compound command returns 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 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 using `!'. These are the same conditions
+ obeyed by the `errexit' (`-e') 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.
`umask'
umask [-p] [-S] [MODE]
+
Set the shell process's file creation mask to MODE. If MODE
begins with a digit, it is interpreted as an octal number; if not,
it is interpreted as a symbolic mode mask similar to that accepted
results in permissions of `755'.
`unset'
- unset [-fv] [NAME]
- Each variable or function NAME is removed. If no options are
- supplied, or the `-v' option is given, each NAME refers to a shell
- variable. If the `-f' option is given, the NAMEs refer to shell
- functions, and the function definition is removed. Readonly
- variables and functions may not be unset. The return status is
- zero unless a NAME does not exist or is readonly.
+ unset [-fnv] [NAME]
+
+ Remove each variable or function NAME. If the `-v' option is
+ given, each NAME refers to a shell variable and that variable is
+ remvoved. If the `-f' option is given, the NAMEs refer to shell
+ functions, and the function definition is removed. If the `-n'
+ option is supplied, and NAME is a variable with the NAMEREF
+ attribute, NAME will be unset rather than the variable it
+ references. `-n' has no effect if the `-f' option is supplied.
+ If no options are supplied, each NAME refers to a variable; if
+ there is no variable by that name, any function with that name is
+ unset. Readonly variables and functions may not be unset. The
+ return status is zero unless a NAME is readonly.
\1f
-File: bashref.info, Node: Bash Builtins, Next: The Set Builtin, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
+File: bashref.info, Node: Bash Builtins, Next: Modifying Shell Behavior, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
-Bash Builtin Commands
-=====================
+4.2 Bash Builtin Commands
+=========================
- This section describes builtin commands which are unique to or have
+This section describes builtin commands which are unique to or have
been extended in Bash. Some of these commands are specified in the
-POSIX 1003.2 standard.
+POSIX standard.
`alias'
- alias [`-p'] [NAME[=VALUE] ...]
+ alias [-p] [NAME[=VALUE] ...]
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
+ and value of the alias is printed. Aliases are described in *note
Aliases::.
`bind'
- bind [-m KEYMAP] [-lpsvPSV]
+ bind [-m KEYMAP] [-lpsvPSVX]
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
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 a
- Readline initialization file (*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:
+ 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'.
+
+ Options, if supplied, have the following meanings:
`-m KEYMAP'
Use KEYMAP as the keymap to be affected by the subsequent
`-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.
+
+ `-X'
+ List all key sequences bound to shell commands and the
+ associated commands in a format that can be reused as input.
The return status is zero unless an invalid option is supplied or
an error occurs.
`builtin'
builtin [SHELL-BUILTIN [ARGS]]
+
Run a shell builtin, passing it ARGS, and return its exit status.
This is useful when defining a shell function with the same name
as a shell builtin, retaining the functionality of the builtin
within the function. The return status is non-zero if
SHELL-BUILTIN is not a shell builtin command.
+`caller'
+ caller [EXPR]
+
+ Returns the context of any active subroutine call (a shell
+ function or a script executed with the `.' or `source' builtins).
+
+ Without EXPR, `caller' displays the line number and source
+ filename of the current subroutine call. If a non-negative
+ integer is supplied as EXPR, `caller' displays the line number,
+ subroutine name, and source file corresponding to that position in
+ the current execution call stack. This extra information may be
+ used, for example, to print a stack trace. The current frame is
+ frame 0.
+
+ The return value is 0 unless the shell is not executing a
+ subroutine call or EXPR does not correspond to a valid position in
+ the call stack.
+
`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
non-zero if not.
`declare'
- declare [-afFrxi] [-p] [NAME[=VALUE]]
+ declare [-aAfFgilnrtux] [-p] [NAME[=VALUE] ...]
Declare variables and give them attributes. If no NAMEs are
given, then display the values of variables instead.
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:
+ NAME. When `-p' is used with NAME arguments, additional options,
+ other than `-f' and `-F', are ignored.
+
+ When `-p' is supplied without NAME arguments, `declare' will
+ display the attributes and values of all variables having the
+ attributes specified by the additional options. If no other
+ options are supplied with `-p', `declare' will display the
+ attributes and values of all shell variables. The `-f' option
+ will restrict the display to shell functions.
+
+ The `-F' option inhibits the display of function definitions; only
+ the function name and attributes are printed. If the `extdebug'
+ shell option is enabled using `shopt' (*note The Shopt Builtin::),
+ the source file name and line number where the function is defined
+ are displayed as well. `-F' implies `-f'.
+
+ The `-g' option forces variables to be created or modified at the
+ global scope, even when `declare' is executed in a shell function.
+ It is ignored in all other cases.
+
+ The following options can be used to restrict output to variables
+ with the specified attributes or to give variables attributes:
`-a'
- Each NAME is an array variable (*note Arrays::).
+ Each NAME is an indexed array variable (*note Arrays::).
+
+ `-A'
+ Each NAME is an associative array variable (*note Arrays::).
`-f'
Use function names only.
evaluation (*note Shell Arithmetic::) is performed when the
variable is assigned a value.
+ `-l'
+ When the variable is assigned a value, all upper-case
+ characters are converted to lower-case. The upper-case
+ attribute is disabled.
+
+ `-n'
+ Give each NAME the NAMEREF attribute, making it a name
+ reference to another variable. That other variable is
+ defined by the value of NAME. All references and assignments
+ to NAME, except for changing the `-n' attribute itself, are
+ performed on the variable referenced by NAME's value. The
+ `-n' attribute cannot be applied to array variables.
+
`-r'
Make NAMEs readonly. These names cannot then be assigned
values by subsequent assignment statements or unset.
+ `-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.
+
+ `-u'
+ When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
+ attribute is disabled.
+
`-x'
Mark each NAME for export to subsequent commands via the
environment.
- Using `+' instead of `-' turns off the attribute instead. When
- used in a function, `declare' makes each NAME local, as with the
- `local' command.
+ 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.
+
+ When using `-a' or `-A' and the compound assignment syntax to
+ create array variables, additional attributes do not take effect
+ until subsequent assignments.
The return status is zero unless an invalid option is encountered,
an attempt is made to define a function using `-f foo=bar', an
`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' interprets the following escape sequences:
+ The return status is 0 unless a write error occurs. 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.
+
+ `echo' interprets the following escape sequences:
`\a'
alert (bell)
backspace
`\c'
- suppress trailing newline
+ suppress further output
`\e'
+ `\E'
escape
`\f'
`\\'
backslash
- `\NNN'
- the character whose `ASCII' code is the octal value NNN (one
- to three digits)
+ `\0NNN'
+ the eight-bit character whose value is the octal value NNN
+ (zero to three octal 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)
+
+ `\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)
`enable'
- enable [-n] [-p] [-f FILENAME] [-ads] [NAME ...]
+ 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
there is an error loading a new builtin from a shared object.
`help'
- help [-s] [PATTERN]
+ 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. The `-s'
- option restricts the information displayed to a short usage
- synopsis. The return status is zero unless no command matches
- PATTERN.
+ PATTERN, otherwise a list of the builtins is printed.
-`let'
- let EXPRESSION [EXPRESSION]
- The `let' builtin allows arithmetic to be performed on shell
+ Options, if supplied, have the following meanings:
+
+ `-d'
+ Display a short description of each PATTERN
+
+ `-m'
+ Display the description of each PATTERN in a manpage-like
+ format
+
+ `-s'
+ Display only a short usage synopsis for each PATTERN
+
+ The return status is zero unless no command matches PATTERN.
+
+`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
+ given below in *note Shell Arithmetic::. If the last EXPRESSION
evaluates to 0, `let' returns 1; otherwise 0 is returned.
`local'
- local [OPTION] NAME[=VALUE]
+ 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
`logout'
logout [N]
+
Exit a login shell, returning a status of N to the shell's parent.
+`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.
+
+ `-O'
+ Begin assigning to ARRAY at index ORIGIN. The default index
+ is 0.
+
+ `-s'
+ Discard the first COUNT lines read.
+
+ `-t'
+ Remove a trailing newline from each line read.
+
+ `-u'
+ Read lines from file descriptor FD instead of the standard
+ input.
+
+ `-C'
+ Evaluate CALLBACK each time QUANTUMP lines are read. The
+ `-c' option specifies QUANTUM.
+
+ `-c'
+ Specify the number of lines read between each call to
+ CALLBACK.
+
+ 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.
+
+ If not supplied with an explicit origin, `mapfile' will clear ARRAY
+ before assigning to it.
+
+ `mapfile' returns successfully unless an invalid option or option
+ argument is supplied, ARRAY is invalid or unassignable, or ARRAY
+ is not an indexed array.
+
`printf'
- `printf' FORMAT [ARGUMENTS]
+ printf [-v VAR] FORMAT [ARGUMENTS]
+
Write the formatted ARGUMENTS to the standard output under the
- control of the FORMAT. The FORMAT is a character string which
- contains three types of objects: plain characters, which are
- simply copied to standard output, character escape sequences,
- which are converted and copied to the standard output, and format
- specifications, each of which causes printing of the next
- successive ARGUMENT. In addition to the standard `printf(1)'
- formats, `%b' causes `printf' to expand backslash escape sequences
- in the corresponding ARGUMENT, and `%q' causes `printf' to output
- the corresponding ARGUMENT in a format that can be reused as shell
- input.
+ 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. If no argument is specified,
+ conversion behaves as if -1 had been given. This is an
+ exception to the usual `printf' behavior.
+
+ 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 FORMAT is reused as necessary to consume all of the ARGUMENTS.
If the FORMAT requires more ARGUMENTS than are supplied, the extra
success, non-zero on failure.
`read'
- read [-ers] [-a ANAME] [-p PROMPT] [-t TIMEOUT] [-n NCHARS] [-d DELIM] [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. 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 or `read' times out.
+ 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 using the same
+ rules the shell uses for expansion (described above in *note Word
+ Splitting::). 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), a variable assignment error
+ (such as assigning to a readonly variable) occurs, or an invalid
+ file descriptor is supplied as the argument to `-u'.
+
Options, if supplied, have the following meanings:
`-a ANAME'
`-e'
Readline (*note Command Line Editing::) is used to obtain the
- line.
+ 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.
+ 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.
`-p PROMPT'
Display PROMPT, without a trailing newline, before attempting
`-t TIMEOUT'
Cause `read' to time out and return failure if a complete
- line of input is not read within TIMEOUT seconds. This
- option has no effect if `read' is not reading input from the
- terminal or a pipe.
-
-`shopt'
- shopt [-pqsu] [-o] [OPTNAME ...]
- Toggle the values of variables controlling optional shell behavior.
- With no options, or with the `-p' option, a list of all settable
- options is displayed, with an indication of whether or not each is
- set. The `-p' option causes output to be displayed in a form that
- may be reused as input. Other options have the following meanings:
-
- `-s'
- Enable (set) each OPTNAME.
-
- `-u'
- Disable (unset) each OPTNAME.
-
- `-q'
- Suppresses normal output; the return status indicates whether
- the OPTNAME is set or unset. If multiple OPTNAME arguments
- are given with `-q', the return status is zero if all
- OPTNAMES are enabled; non-zero otherwise.
-
- `-o'
- Restricts the values of OPTNAME to be those defined for the
- `-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,
- respectively.
-
- Unless otherwise noted, the `shopt' options are disabled (off) 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.
-
- The list of `shopt' options is:
- `cdable_vars'
- If this is set, an argument to the `cd' builtin command that
- is not a directory is assumed to be the name of a variable
- whose value is the directory to change to.
-
- `cdspell'
- If set, minor errors in the spelling of a directory component
- in a `cd' command will be corrected. The errors checked for
- are transposed characters, a missing character, and a
- character too many. If a correction is found, the corrected
- path is printed, and the command proceeds. This option is
- only used by interactive shells.
-
- `checkhash'
- If this is set, Bash checks that a command found in the hash
- table exists before trying to execute it. If a hashed
- command no longer exists, a normal path search is performed.
-
- `checkwinsize'
- If set, Bash checks the window size after each command and,
- if necessary, updates the values of `LINES' and `COLUMNS'.
-
- `cmdhist'
- If set, Bash attempts to save all lines of a multiple-line
- command in the same history entry. This allows easy
- re-editing of multi-line commands.
-
- `dotglob'
- If set, Bash includes filenames beginning with a `.' in the
- results of filename expansion.
-
- `execfail'
- If this is set, a non-interactive shell will not exit if it
- cannot execute the file specified as an argument to the `exec'
- builtin command. An interactive shell does not exit if `exec'
- fails.
-
- `expand_aliases'
- If set, aliases are expanded as described below under Aliases,
- *Note Aliases::. This option is enabled by default for
- interactive shells.
-
- `extglob'
- If set, the extended pattern matching features described above
- (*note Pattern Matching::) are enabled.
-
- `histappend'
- If set, the history list is appended to the file named by the
- value of the `HISTFILE' variable when the shell exits, rather
- than overwriting the file.
-
- `histreedit'
- If set, and Readline is being used, a user is given the
- opportunity to re-edit a failed history substitution.
-
- `histverify'
- If set, and Readline is being used, the results of history
- substitution are not immediately passed to the shell parser.
- Instead, the resulting line is loaded into the Readline
- editing buffer, allowing further modification.
-
- `hostcomplete'
- If set, and Readline is being used, Bash will attempt to
- perform hostname completion when a word containing a `@' is
- being completed (*note Commands For Completion::). This
- option is enabled by default.
-
- `huponexit'
- If set, Bash will send `SIGHUP' to all jobs when an
- 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.
-
- `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.
-
- `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.
-
- `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::).
- 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
- parameters.
-
- `sourcepath'
- If set, the `source' builtin uses the value of `PATH' to find
- the directory containing the file supplied as an argument.
- This option is enabled by default.
-
- `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.
+ line of input (or a specified number of characters) 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 `read' times out, `read'
+ saves any partial input read into the specified variable NAME.
+ If TIMEOUT is 0, `read' returns immediately, without trying to
+ read and data. The exit status is 0 if input is available on
+ the specified file descriptor, non-zero otherwise. The exit
+ status is greater than 128 if the timeout is exceeded.
+
+ `-u FD'
+ Read input from file descriptor FD.
+
+`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.
+
+ A synonym for `mapfile'.
`source'
source FILENAME
+
A synonym for `.' (*note Bourne Shell Builtins::).
`type'
- type [-atp] [NAME ...]
+ type [-afptP] [NAME ...]
+
For each NAME, indicate how it would be interpreted if used as a
command name.
disk file that would be executed, or nothing if `-t' would not
return `file'.
+ The `-P' option forces a path search for each NAME, even if `-t'
+ would not return `file'.
+
+ If a command is hashed, `-p' and `-P' print the hashed value,
+ which is not necessarily the file that appears first in `$PATH'.
+
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.
- The return status is zero if any of the NAMES are found, non-zero
- if none are found.
+ If the `-f' option is used, `type' does not attempt to find shell
+ functions, as with the `command' builtin.
+
+ The return status is zero if all of the NAMES are found, non-zero
+ if any are not found.
`typeset'
- typeset [-afFrxi] [-p] [NAME[=VALUE]]
+ typeset [-afFgrxilnrtux] [-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.
+ shell. It is a synonym for the `declare' builtin command.
`ulimit'
- ulimit [-acdflmnpstuvSH] [LIMIT]
+ 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.
`-a'
All current limits are reported.
+ `-b'
+ The maximum socket buffer size.
+
`-c'
The maximum size of core files created.
`-d'
The maximum size of a process's data segment.
+ `-e'
+ The maximum scheduling priority ("nice").
+
`-f'
- The maximum size of files created by the shell.
+ The maximum size of files written by the shell and its
+ children.
+
+ `-i'
+ The maximum number of pending signals.
`-l'
The maximum size that may be locked into memory.
`-m'
- The maximum resident set size.
+ The maximum resident set size (many systems do not honor this
+ limit).
`-n'
- The maximum number of open file descriptors.
+ The maximum number of open file descriptors (most systems do
+ not allow this value to be set).
`-p'
The pipe buffer size.
+ `-q'
+ The maximum number of bytes in POSIX message queues.
+
+ `-r'
+ The maximum real-time scheduling priority.
+
`-s'
The maximum stack size.
The maximum number of processes available to a single user.
`-v'
- The maximum amount of virtual memory available to the process.
+ The maximum amount of virtual memory available to the shell,
+ and, on some systems, to its children.
+
+ `-x'
+ The maximum number of file locks.
- If LIMIT is given, it is the new value of the specified resource.
+ `-T'
+ The maximum number of threads.
+
+ If LIMIT is given, and the `-a' option is not used, LIMIT 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.
+ which is in seconds; `-p', which is in units of 512-byte blocks;
+ and `-T', `-b', `-n' and `-u', which are unscaled values.
- 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.
+ The return status is zero unless an invalid option or argument is
+ supplied, or an error occurs while setting a new limit.
`unalias'
unalias [-a] [NAME ... ]
Remove each NAME from the list of aliases. If `-a' is supplied,
- all aliases are removed. Aliases are described in *Note Aliases::.
+ all aliases are removed. Aliases are described in *note Aliases::.
+
+\1f
+File: bashref.info, Node: Modifying Shell Behavior, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
+
+4.3 Modifying Shell Behavior
+============================
+
+* Menu:
+
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
\1f
-File: bashref.info, Node: The Set Builtin, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
+File: bashref.info, Node: The Set Builtin, Next: The Shopt Builtin, Up: Modifying Shell Behavior
-The Set Builtin
-===============
+4.3.1 The Set Builtin
+---------------------
- This builtin is so complicated that it deserves its own section.
+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.
`set'
- set [--abefhkmnptuvxBCHP] [-o OPTION] [ARGUMENT ...]
+ set [--abefhkmnptuvxBCEHPT] [-o OPTION-NAME] [ARGUMENT ...]
+ set [+abefhkmnptuvxBCEHPT] [+o OPTION-NAME] [ARGUMENT ...]
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.
+ 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.
When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:
prompt.
`-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 `!'.
+ Exit immediately if a pipeline (*note Pipelines::), which may
+ consist of a single simple command (*note Simple Commands::),
+ a list (*note Lists::), or a compound command (*note Compound
+ Commands::) 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 `!'. If a
+ compound command other than a subshell returns a non-zero
+ status because a command failed while `-e' was being ignored,
+ the shell does not exit. 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.
+
+ If a compound command or shell function executes in a context
+ where `-e' is being ignored, none of the commands executed
+ within the compound command or function body will be affected
+ by the `-e' setting, even if `-e' is set and a command
+ returns a failure status. If a compound command or shell
+ function sets `-e' while executing in a context where `-e' is
+ ignored, that setting will not have any effect until the
+ compound command or the command containing the function call
+ completes.
`-f'
- Disable file name generation (globbing).
+ Disable filename expansion (globbing).
`-h'
Locate and remember (hash) commands as they are looked up for
the command name.
`-m'
- Job control is enabled (*note Job Control::).
+ Job control is enabled (*note Job Control::). All processes
+ run in a separate process group. When a background job
+ completes, the shell prints a line containing its exit status.
`-n'
Read commands but do not execute them; this may be used to
`emacs'
Use an `emacs'-style line editing interface (*note
- Command Line Editing::).
+ Command Line Editing::). This also affects the editing
+ interface used for `read -e'.
`errexit'
Same as `-e'.
+ `errtrace'
+ Same as `-E'.
+
+ `functrace'
+ Same as `-T'.
+
`hashall'
Same as `-h'.
Same as `-H'.
`history'
- Enable command history, as described in *Note Bash
+ Enable command history, as described in *note Bash
History Facilities::. This option is on by default in
interactive shells.
`noglob'
Same as `-f'.
+ `nolog'
+ Currently ignored.
+
`notify'
Same as `-b'.
`physical'
Same as `-P'.
+ `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.
+
`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.
+ 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.
`privileged'
Same as `-p'.
Same as `-v'.
`vi'
- Use a `vi'-style line editing interface.
+ Use a `vi'-style line editing interface. This also
+ affects the editing interface used for `read -e'.
`xtrace'
Same as `-x'.
`-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. If the shell
- is started with the effective user (group) id not equal to the
+ 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,
Exit after reading and executing one command.
`-u'
- Treat unset variables as an error when performing parameter
+ 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.
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.
+ 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.
`-B'
The shell will perform brace expansion (*note Brace
Prevent output redirection using `>', `>&', and `<>' from
overwriting existing files.
+ `-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.
+
`-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.
+ If set, do not resolve 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 ..; pwd
/usr
- If `set -P' is on, then:
- $ cd /usr/sys; echo $PWD
- /usr/local/sys
- $ cd ..; pwd
- /usr/local
+ If `set -P' is on, then:
+ $ cd /usr/sys; echo $PWD
+ /usr/local/sys
+ $ cd ..; pwd
+ /usr/local
+
+ `-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.
+
+ `--'
+ 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: 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 ...]
+
+ Toggle the values of settings controlling optional shell behavior.
+ The settings can be either those listed below, or, if the `-o'
+ option is used, those available with the `-o' option to the `set'
+ builtin command (*note The Set Builtin::). With no options, or
+ with the `-p' option, a list of all settable options is displayed,
+ with an indication of whether or not each is set. The `-p' option
+ causes output to be displayed in a form that may be reused as
+ input. Other options have the following meanings:
+
+ `-s'
+ Enable (set) each OPTNAME.
+
+ `-u'
+ Disable (unset) each OPTNAME.
+
+ `-q'
+ Suppresses normal output; the return status indicates whether
+ the OPTNAME is set or unset. If multiple OPTNAME arguments
+ are given with `-q', the return status is zero if all
+ OPTNAMES are enabled; non-zero otherwise.
+
+ `-o'
+ Restricts the values of OPTNAME to be those defined for the
+ `-o' option to the `set' builtin (*note The Set Builtin::).
+
+ If either `-s' or `-u' is used with no OPTNAME arguments, `shopt'
+ shows only those options which are set or unset, respectively.
+
+ Unless otherwise noted, the `shopt' options are disabled (off) 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.
+
+ 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
+ whose value is the directory to change to.
+
+ `cdspell'
+ If set, minor errors in the spelling of a directory component
+ in a `cd' command will be corrected. The errors checked for
+ are transposed characters, a missing character, and a
+ character too many. If a correction is found, the corrected
+ path is printed, and the command proceeds. This option is
+ only used by interactive shells.
+
+ `checkhash'
+ If this is set, Bash checks that a command found in the hash
+ table exists before trying to execute it. If a hashed
+ command no longer exists, a normal path search is performed.
+
+ `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'.
+
+ `cmdhist'
+ If set, Bash attempts to save all lines of a multiple-line
+ command in the same history entry. This allows easy
+ re-editing of multi-line commands.
+
+ `compat31'
+ If set, Bash changes its behavior to that of version 3.1 with
+ respect to quoted arguments to the conditional command's `=~'
+ operator and with respect to locale-specific string
+ comparison when using the `[[' conditional command's `<' and
+ `>' operators. Bash versions prior to bash-4.1 use ASCII
+ collation and strcmp(3); bash-4.1 and later use the current
+ locale's collation sequence and strcoll(3).
+
+ `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 (see
+ previous item).
+
+ `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
+ description of `compat31') and the effect of interrupting a
+ command list. Bash versions 4.0 and later interrupt the list
+ as if the shell received the interrupt; previous versions
+ continue with the next command in the 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.
+
+ `compat42'
+ If set, Bash does not process the replacement string in the
+ pattern substitution word expansion using quote removal.
+
+ `complete_fullquote'
+ If set, Bash quotes all shell metacharacters in filenames and
+ directory names when performing completion. If not set, Bash
+ removes metacharacters such as the dollar sign from the set of
+ characters that will be quoted in completed filenames when
+ these metacharacters appear in shell variable references in
+ words to be completed. This means that dollar signs in
+ variable names that expand to directories will not be quoted;
+ however, any dollar signs appearing in filenames will not be
+ quoted, either. This is active only when bash is using
+ backslashes to quote completed filenames. This variable is
+ set by default, which is the default Bash behavior in
+ versions through 4.2.
+
+ `direxpand'
+ If set, Bash replaces directory names with the results of
+ word expansion when performing filename completion. This
+ changes the contents of the readline editing buffer. If not
+ set, Bash attempts to preserve what the user typed.
+
+ `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.
+
+ `execfail'
+ If this is set, a non-interactive shell will not exit if it
+ cannot execute the file specified as an argument to the `exec'
+ builtin command. An interactive shell does not exit if `exec'
+ fails.
+
+ `expand_aliases'
+ 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.
+
+ `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.
+
+ `globasciiranges'
+ If set, range expressions used in pattern matching bracket
+ expressions (*note Pattern Matching::) behave as if in the
+ traditional C locale when performing comparisons. That is,
+ the current locale's collating sequence is not taken into
+ account, so `b' will not collate between `A' and `B', and
+ upper-case and lower-case ASCII characters will collate
+ together.
+
+ `globstar'
+ If set, the pattern `**' used in a filename expansion context
+ will match all 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
+ value of the `HISTFILE' variable when the shell exits, rather
+ than overwriting the file.
+
+ `histreedit'
+ If set, and Readline is being used, a user is given the
+ opportunity to re-edit a failed history substitution.
+
+ `histverify'
+ If set, and Readline is being used, the results of history
+ substitution are not immediately passed to the shell parser.
+ Instead, the resulting line is loaded into the Readline
+ editing buffer, allowing further modification.
+
+ `hostcomplete'
+ If set, and Readline is being used, Bash will attempt to
+ perform hostname completion when a word containing a `@' is
+ being completed (*note Commands For Completion::). This
+ option is enabled by default.
+
+ `huponexit'
+ If set, Bash will send `SIGHUP' to all jobs when an
+ 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 parameter expansion, command
+ substitution, arithmetic expansion, and quote removal after
+ being expanded as described below (*note Controlling the
+ Prompt::). This option is enabled by default.
- `--'
- 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
- `-'.
+ `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.
- `-'
- 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.
+ `shift_verbose'
+ If this is set, the `shift' builtin prints an error message
+ when the shift count exceeds the number of positional
+ parameters.
- 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 `$-'.
+ `sourcepath'
+ If set, the `source' builtin uses the value of `PATH' to find
+ the directory containing the file supplied as an argument.
+ This option is enabled by default.
- The remaining N ARGUMENTS are positional parameters and are
- assigned, in order, to `$1', `$2', ... `$N'. The special
- parameter `#' is set to N.
+ `xpg_echo'
+ If set, the `echo' builtin expands backslash-escape sequences
+ by default.
- The return status is always zero unless an invalid option is
- supplied.
+
+ 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.
\1f
-File: bashref.info, Node: Special Builtins, Prev: The Set Builtin, Up: Shell Builtin Commands
+File: bashref.info, Node: Special Builtins, Prev: Modifying Shell Behavior, Up: Shell Builtin Commands
-Special Builtins
-================
+4.4 Special Builtins
+====================
- For historical reasons, the POSIX 1003.2 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
+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:
1. Special builtins are found before shell functions during command
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::.
+mode is described in *note Bash POSIX Mode::.
These are the POSIX special builtins:
break : . continue eval exec exit export readonly return set
\1f
File: bashref.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
-Shell Variables
-***************
+5 Shell Variables
+*****************
* Menu:
\1f
File: bashref.info, Node: Bourne Shell Variables, Next: Bash Variables, Up: Shell Variables
-Bourne Shell Variables
-======================
+5.1 Bourne Shell Variables
+==========================
- Bash uses certain shell variables in the same way as the Bourne
-shell. In some cases, Bash assigns a default value to the variable.
+Bash uses certain shell variables in the same way as the Bourne shell.
+In some cases, Bash assigns a default value to the variable.
`CDPATH'
A colon-separated list of directories used as a search path for
splits words as part of expansion.
`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.
+ 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.
`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
+ the filename from the message with a `?'. When used in the text
of the message, `$_' expands to the name of the current mail file.
`OPTARG'
`PATH'
A colon-separated list of directories in which the shell looks for
- commands.
+ 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.
`PS1'
The primary prompt string. The default value is `\s-\v\$ '.
- *Note Printing a Prompt::, for the complete list of escape
+ *Note Controlling the Prompt::, for the complete list of escape
sequences that are expanded before `PS1' is displayed.
`PS2'
The secondary prompt string. The default value is `> '.
+
\1f
File: bashref.info, Node: Bash Variables, Prev: Bourne Shell Variables, Up: Shell Variables
-Bash Variables
-==============
+5.2 Bash Variables
+==================
- These variables are set or used by Bash, but other shells do not
+These variables are set or used by Bash, but other shells do not
normally treat them specially.
A few variables used by Bash are described in different chapters:
`BASH'
The full pathname used to execute the current instance of Bash.
+`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.
+
+`BASH_COMPAT'
+ The value is used to set the shell's compatibility level. *Note
+ The Shopt Builtin::, for a description of the various compatibility
+ levels and their effects. The value may be a decimal number
+ (e.g., 4.2) or an integer (e.g., 42) corresponding to the desired
+ compatibility level. If `BASH_COMPAT' is unset or set to the
+ empty string, the compatibility level is set to the default for
+ the current version. If `BASH_COMPAT' is set to a value that is
+ not one of the valid compatibility levels, the shell prints an
+ error message and sets the compatibility level to the default for
+ the current version. The valid compatibility levels correspond to
+ the compatibility options accepted by the `shopt' builtin
+ described above (for example, COMPAT42 means that 4.2 and 42 are
+ valid values). The current version is also a valid value.
+
`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_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 within each subshell or subshell environment
+ when the shell begins executing in that environment. The initial
+ value is 0.
`BASH_VERSINFO'
A readonly array variable (*note Arrays::) whose members hold
`BASH_VERSINFO[5]'
The value of `MACHTYPE'.
-`COMP_WORDS'
- An array variable consisting of the individual words in the
- current command line. This variable is available only in shell
- functions invoked by the programmable completion facilities (*note
- Programmable Completion::).
+`BASH_VERSION'
+ The version number of the current instance of Bash.
+
+`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.
+
+`CHILD_MAX'
+ Set the number of exited child status values for the shell to
+ remember. Bash will not allow this value to be decreased below a
+ POSIX-mandated minimum, and there is a maximum value (currently
+ 8192) that this may not exceed. The minimum value is
+ system-dependent.
+
+`COLUMNS'
+ Used by the `select' command to determine the terminal width when
+ printing selection lists. Automatically set if the `checkwinsize'
+ option is enabled (*note The Shopt Builtin::), or in an
+ interactive shell upon receipt of a `SIGWINCH'.
`COMP_CWORD'
An index into `${COMP_WORDS}' of the word containing the current
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::).
+ completion facility (*note Programmable Completion::). Each array
+ element contains one possible completion.
+
+`COPROC'
+ An array variable created to hold the file descriptors for output
+ from and input to an unnamed coprocess (*note Coprocesses::).
`DIRSTACK'
An array variable containing the current contents of the directory
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::).
+
`EUID'
The numeric effective user id of the current user. This variable
is readonly.
`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:~'
+ filename completion. A filename whose suffix matches one of the
+ entries in `FIGNORE' is excluded from the list of matched
+ filenames. A sample value is `.o:~'
+
+`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.
+
+ 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.
+
+`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.
`GLOBIGNORE'
A colon-separated list of patterns defining the set of filenames to
command. If `HISTCMD' is unset, it loses its special properties,
even if it is subsequently reset.
-`FUNCNAME'
- The name of any currently-executing shell function. 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.
-
`HISTCONTROL'
- A value of `ignorespace' means to not enter lines which begin with
- a space or tab into the history list. A value of `ignoredups'
- means to not 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'.
+ 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'.
+
+`HISTFILE'
+ The name of the file to which the command history is saved. The
+ default value is `~/.bash_history'.
+
+`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 by
+ removing the oldest entries. The history file is also truncated
+ to this size after writing it when a shell exits. If the value is
+ 0, the history file is truncated to zero size. Non-numeric values
+ and numeric values less than zero inhibit truncation. The shell
+ sets the default value to the value of `HISTSIZE' after reading
+ any startup files.
`HISTIGNORE'
A colon-separated list of patterns used to decide which command
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 value 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
- history file is also truncated to this size after writing it when
- an interactive shell exits. The default value is 500.
+ If the value is 0, commands are not saved in the history list.
+ Numeric values less than zero result in every command being saved
+ on the history list (there is no limit). The shell sets the
+ default value to 500 after reading any startup files.
+
+`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
list of possible hostname completions may be changed while the
shell is running; the next time hostname completion is attempted
after the value is changed, Bash adds the contents of the new file
- to the existing list. If `HOSTFILE' is set, but has no value,
- Bash attempts to read `/etc/hosts' to obtain the list of possible
- hostname completions. When `HOSTFILE' is unset, the hostname list
- is cleared.
+ 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.
This variable determines the locale category used for number
formatting.
-`LINES'
- Used by the `select' builtin command to determine the column length
- for printing selection lists. Automatically set upon receipt of a
- `SIGWINCH'.
-
-`COLUMNS'
- Used by the `select' builtin command to determine the terminal
- width when printing selection lists. Automatically set upon
- receipt of a `SIGWINCH'.
-
`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 if the `checkwinsize'
+ option is enabled (*note The Shopt Builtin::), or in an
+ interactive shell 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.
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.
status values from the processes in the most-recently-executed
foreground pipeline (which may contain only a single command).
+`POSIXLY_CORRECT'
+ If this variable is in the environment when Bash starts, the shell
+ enters POSIX mode (*note Bash POSIX Mode::) before reading the
+ startup files, as if the `--posix' invocation option had been
+ supplied. If it is set while the shell is running, Bash enables
+ POSIX mode, as if the command
+ `set -o posix'
+ had been executed.
+
`PPID'
The process ID of the shell's parent process. This variable is
readonly.
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 Controlling the
+ Prompt::). Characters removed are replaced with an ellipsis.
+
`PS3'
The value of this variable is used as the prompt for the `select'
command. If this variable is not set, the `select' command
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
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 when the shell is interactive. 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 a line of input after issuing the primary
+ prompt. Bash terminates after waiting for that number of seconds
+ if a complete line of input does not arrive.
+
+`TMPDIR'
+ If set, Bash uses its value as the name of a directory in which
+ Bash creates temporary files for the shell's use.
`UID'
The numeric real user id of the current user. This variable is
readonly.
+
\1f
File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Shell Variables, Up: Top
-Bash Features
-*************
+6 Bash Features
+***************
- This section describes features unique to Bash.
+This chapter describes features unique to Bash.
* Menu:
* Aliases:: Substituting one command for another.
* Arrays:: Array Variables.
* The Directory Stack:: History of visited directories.
-* Printing a Prompt:: Controlling the PS1 string.
+* Controlling the Prompt:: Customizing the various prompt strings.
* The Restricted Shell:: A more controlled mode of shell execution.
* Bash POSIX Mode:: Making Bash behave more closely to what
the POSIX standard specifies.
\1f
File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
-Invoking Bash
-=============
+6.1 Invoking Bash
+=================
+
+ bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] [ARGUMENT ...]
+ bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] -c STRING [ARGUMENT ...]
+ bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] [ARGUMENT ...]
- 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 ...]
+ 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.
- 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.
+`--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).
`--dump-po-strings'
A list of all double-quoted strings preceded by `$' is printed on
- the standard ouput in the GNU `gettext' PO (portable object) file
+ the standard output in the GNU `gettext' PO (portable object) file
format. Equivalent to `-D' except for the output format.
`--dump-strings'
Equivalent to `-D'.
`--help'
- Display a usage message on standard output and exit sucessfully.
+ Display a usage message on standard output and exit successfully.
`--init-file FILENAME'
`--rcfile FILENAME'
interactive shell.
`--login'
- 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 --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.
+ Equivalent to `-l'.
`--noediting'
Do not use the GNU Readline library (*note Command Line Editing::)
`--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.
+ from the POSIX standard to match the standard. This is intended
+ to make Bash behave as a strict superset of that standard. *Note
+ Bash POSIX Mode::, for a description of the Bash POSIX mode.
`--restricted'
Make the shell a restricted shell (*note The Restricted Shell::).
There are several single-character options that may be supplied at
invocation which are not available with the `set' builtin.
-`-c STRING'
- Read and execute commands from STRING after processing the
- options, then exit. Any remaining arguments are assigned to the
- positional parameters, starting with `$0'.
+`-c'
+ Read and execute commands from the first non-option ARGUMENT after
+ processing the options, then exit. Any remaining arguments are
+ assigned to the positional parameters, starting with `$0'.
`-i'
Force the shell to run interactively. Interactive shells are
- described in *Note Interactive Shells::.
+ described in *note Interactive Shells::.
+
+`-l'
+ Make this shell act as if it had been directly invoked by login.
+ When the shell is interactive, this is equivalent to starting a
+ login shell with `exec -l bash'. When the shell is not
+ interactive, the login shell startup files will be executed.
+ `exec bash -l' or `exec bash --login' will replace the current
+ shell with a Bash login shell. *Note Bash Startup Files::, for a
+ description of the special behavior of a login shell.
`-r'
Make the shell a restricted shell (*note The Restricted Shell::).
`-D'
A list of all double-quoted strings preceded by `$' is printed on
- the standard ouput. These are the strings that are subject to
+ the standard output. These are the strings that are subject to
language translation when the current locale is not `C' or `POSIX'
(*note Locale Translation::). This implies the `-n' option; no
commands will be executed.
+`[-+]O [SHOPT_OPTION]'
+ SHOPT_OPTION is one of the shell options accepted by the `shopt'
+ builtin (*note The Shopt Builtin::). If SHOPT_OPTION is present,
+ `-O' sets the value of that option; `+O' unsets it. If
+ SHOPT_OPTION is not supplied, the names and values of the shell
+ options accepted by `shopt' are printed on the standard output.
+ If the invocation option is `+O', the output is displayed in a
+ format that may be reused as input.
+
`--'
A `--' signals the end of options and disables further option
processing. Any arguments after the `--' are treated as filenames
and arguments.
+ A _login_ shell is one whose first character of argument zero is
+`-', or one invoked with the `--login' option.
+
An _interactive_ shell is one started without non-option arguments,
unless `-s' is specified, without specifying the `-c' option, and whose
input and output are both connected to terminals (as determined by
\1f
File: bashref.info, Node: Bash Startup Files, Next: Interactive Shells, Prev: Invoking Bash, Up: Bash Features
-Bash Startup Files
-==================
+6.2 Bash Startup Files
+======================
- 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::).
+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 filenames as described above under Tilde Expansion (*note
+Tilde Expansion::).
- Interactive shells are described in *Note Interactive Shells::.
+ Interactive shells are described in *note Interactive Shells::.
Invoked as an interactive login shell, or with `--login'
........................................................
- When Bash is invoked as an interactive login shell, or as a
+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',
Invoked as an interactive non-login shell
.........................................
- When an interactive shell that is not a login shell is started, Bash
+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
So, typically, your `~/.bash_profile' contains the line
`if [ -f ~/.bashrc ]; then . ~/.bashrc; fi'
-
-after (or before) any login-specific initializations.
+ after (or before) any login-specific initializations.
Invoked non-interactively
.........................
- When Bash is started non-interactively, to run a shell script, for
+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.
+ but the value of the `PATH' variable is not used to search for the
+filename.
As noted above, if a non-interactive shell is invoked with the
`--login' option, Bash attempts to read and execute commands from the
Invoked with name `sh'
......................
- If Bash is invoked with the name `sh', it tries to mimic the startup
+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.
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.
+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 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.
+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 neither `rshd' nor `sshd' generally
+invoke the shell with those options or allow them to be specified.
Invoked with unequal effective and real UID/GIDs
................................................
- If Bash is started with the effective user (group) id not equal to
-the real user (group) id, and the `-p' option is not supplied, no
-startup files are read, shell functions are not inherited from the
-environment, the `SHELLOPTS' variable, if it appears in the
-environment, is ignored, and the effective user id is set to the real
-user id. If the `-p' option is supplied at invocation, the startup
-behavior is the same, but the effective user id is not reset.
+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: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
-Interactive Shells
-==================
+6.3 Interactive Shells
+======================
* Menu:
\1f
File: bashref.info, Node: What is an Interactive Shell?, Next: Is this Shell Interactive?, Up: Interactive Shells
-What is an Interactive Shell?
------------------------------
+6.3.1 What is an Interactive Shell?
+-----------------------------------
- An interactive shell is one started without non-option arguments,
-unless `-s' is specified, without specifiying the `-c' option, and
-whose input and output are both connected to terminals (as determined
+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.
An interactive shell generally reads from and writes to a user's
\1f
File: bashref.info, Node: Is this Shell Interactive?, Next: Interactive Shell Behavior, Prev: What is an Interactive Shell?, Up: Interactive Shells
-Is this Shell Interactive?
---------------------------
+6.3.2 Is this Shell Interactive?
+--------------------------------
- To determine within a startup script whether or not Bash is running
+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:
\1f
File: bashref.info, Node: Interactive Shell Behavior, Prev: Is this Shell Interactive?, Up: Interactive Shells
-Interactive Shell Behavior
---------------------------
+6.3.3 Interactive Shell Behavior
+--------------------------------
- When the shell is running interactively, it changes its behavior in
+When the shell is running interactively, it changes its behavior in
several ways.
- 1. Startup files are read and executed as described in *Note Bash
+ 1. Startup files are read and executed as described in *note Bash
Startup Files::.
2. Job Control (*note Job Control::) is enabled by default. When job
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.
+ when a shell with history enabled exits.
8. Alias expansion (*note Aliases::) is performed by default.
((*note Signals::). `SIGINT' will interrupt some shell builtins.
11. An interactive login shell sends a `SIGHUP' to all jobs on exit if
- the `hupoxexit' shell option has been enabled (*note Signals::).
+ the `huponexit' shell option has been enabled (*note Signals::).
12. The `-n' invocation option is ignored, and `set -n' has no effect
(*note The Set Builtin::).
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 Bash Builtins::).
+ option to the `shopt' builtin in *note The Shopt Builtin::).
21. The shell will check the value of the `TMOUT' variable and exit if
a command is not read within the specified number of seconds after
\1f
File: bashref.info, Node: Bash Conditional Expressions, Next: Shell Arithmetic, Prev: Interactive Shells, Up: Bash Features
-Bash Conditional Expressions
-============================
+6.4 Bash Conditional Expressions
+================================
- Conditional expressions are used by the `[[' compound command and
-the `test' and `[' builtin commands.
+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
`/dev/stdin', `/dev/stdout', or `/dev/stderr', file descriptor 0, 1, or
2, respectively, is checked.
+ When used with `[[', the `<' and `>' operators sort
+lexicographically using the current locale. The `test' command uses
+ASCII ordering.
+
+ Unless otherwise specified, primaries that operate on files follow
+symbolic links and operate on the target of the link, rather than the
+link itself.
+
`-a FILE'
True if FILE exists.
`-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.
+`-N FILE'
+ True if FILE exists and has been modified since it was last read.
+
+`-O FILE'
+ True if FILE exists and is owned by the effective user id.
+
`-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 -ef FILE2'
+ True if FILE1 and FILE2 refer to the same device and inode numbers.
`FILE1 -nt FILE2'
- True if FILE1 is newer (according to modification date) than FILE2.
+ True if FILE1 is newer (according to modification date) than
+ FILE2, or if FILE1 exists and FILE2 does not.
`FILE1 -ot FILE2'
- True if FILE1 is older than FILE2.
-
-`FILE1 -ef FILE2'
- True if FILE1 and FILE2 have the same device and inode numbers.
+ True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
+ does not.
`-o OPTNAME'
- True if shell option OPTNAME is enabled. The list of options
+ 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::).
+`-v VARNAME'
+ True if the shell variable VARNAME is set (has been assigned a
+ value).
+
+`-R VARNAME'
+ True if the shell variable VARNAME is set and is a name reference.
+
`-z STRING'
True if the length of STRING is zero.
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 equal. When used with the `[[' command,
+ this performs pattern matching as described above (*note
+ Conditional Constructs::).
+
+ `=' should be used with the `test' command for POSIX conformance.
`STRING1 != STRING2'
True if the strings are not equal.
`STRING1 < STRING2'
- True if STRING1 sorts before STRING2 lexicographically in the
- current locale.
+ True if STRING1 sorts before STRING2 lexicographically.
`STRING1 > STRING2'
- True if STRING1 sorts after STRING2 lexicographically in the
- current locale.
+ True if STRING1 sorts after STRING2 lexicographically.
`ARG1 OP ARG2'
`OP' is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These
\1f
File: bashref.info, Node: Shell Arithmetic, Next: Aliases, Prev: Bash Conditional Expressions, Up: Bash Features
-Shell Arithmetic
-================
+6.5 Shell Arithmetic
+====================
- The shell allows arithmetic expressions to be evaluated, as one of
-the shell expansions or by the `let' builtin.
+The shell allows arithmetic expressions to be evaluated, as one of the
+shell expansions or by the `let' and the `-i' option to the `declare'
+builtins.
- Evaluation is done in long integers with no check for overflow,
-though division by 0 is trapped and flagged as an error. The operators
-and their precedence and associativity 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.
+ Evaluation is done in fixed-width integers with no check for
+overflow, though division by 0 is trapped and flagged as an error. The
+operators and their precedence, associativity, and values are the same
+as in the C language. The following list of operators is grouped into
+levels of equal-precedence operators. The levels are listed in order
+of decreasing precedence.
`ID++ ID--'
variable post-increment and post-decrement
logical OR
`expr ? expr : expr'
- conditional evaluation
+ conditional operator
`= *= /= %= += -= <<= >>= &= ^= |='
assignment
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. The value of a variable is evaluated as an
-arithmetic expression when it is referenced. A shell variable need not
-have its integer attribute turned on to be used in an expression.
+parameter expansion syntax. A shell variable that is null or unset
+evaluates to 0 when referenced by name without using the parameter
+expansion syntax. The value of a variable is evaluated as an
+arithmetic expression when it is referenced, or when a variable which
+has been given the INTEGER attribute using `declare -i' is assigned a
+value. A null value evaluates to 0. A shell variable need not have
+its INTEGER attribute turned on to be used in an expression.
Constants with a leading 0 are interpreted as octal numbers. A
leading `0x' or `0X' denotes hexadecimal. Otherwise, numbers take the
-form [BASE`#']N, where BASE is a decimal number between 2 and 64
-representing the arithmetic base, and N is a number in that base. If
-BASE`#' is omitted, then base 10 is used. The digits greater than 9
-are represented by the lowercase letters, the uppercase letters, `_',
-and `@', in that order. If BASE is less than or equal to 36, lowercase
-and uppercase letters may be used interchangably to represent numbers
-between 10 and 35.
+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. When specifying N, he
+digits greater than 9 are represented by the lowercase letters, the
+uppercase letters, `@', and `_', in that order. If BASE is less than
+or equal to 36, lowercase and uppercase letters may be used
+interchangeably to represent numbers between 10 and 35.
Operators are evaluated in order of precedence. Sub-expressions in
parentheses are evaluated first and may override the precedence rules
\1f
File: bashref.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
-Aliases
-=======
+6.6 Aliases
+===========
- ALIASES allow a string to be substituted for a word when it is used
-as the first word of a simple command. The shell maintains a list of
+ALIASES allow a string to be substituted for a word when it is used as
+the first word of a simple command. The shell maintains a list of
aliases that may be set and unset with the `alias' and `unalias'
builtin commands.
The first word of each simple command, if unquoted, is checked to see
if it has an alias. If so, that word is replaced by the text of the
-alias. The 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.
+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 BLANK, then the next command word following the alias is also
+checked for alias expansion.
Aliases are created and listed with the `alias' command, and removed
with the `unalias' command.
(*note Shell Functions::).
Aliases are not expanded when the shell is not interactive, unless
-the `expand_aliases' shell option is set using `shopt' (*note Bash
-Builtins::).
+the `expand_aliases' shell option is set using `shopt' (*note The Shopt
+Builtin::).
The rules concerning the definition and use of aliases are somewhat
confusing. Bash always reads at least one complete line of input
\1f
File: bashref.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
-Arrays
-======
+6.7 Arrays
+==========
- 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.
+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. Unless otherwise
+noted, indexed array indices must be non-negative integers.
- An array is created automatically if any variable is assigned to
-using the syntax
- name[SUBSCRIPT]=VALUE
+ An indexed array is created automatically if any variable is
+assigned to using the syntax
+ NAME[SUBSCRIPT]=VALUE
The SUBSCRIPT is treated as an arithmetic expression that must evaluate
-to a number greater than or equal to zero. To explicitly declare an
-array, use
+to a number. To explicitly declare an array, use
declare -a NAME
-
-The syntax
+ The syntax
declare -a NAME[SUBSCRIPT]
+ is also accepted; the SUBSCRIPT is ignored.
+
+Associative arrays are created using
+ declare -A 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.
+ Attributes may be specified for an array variable using the
+`declare' and `readonly' builtins. Each attribute applies to all
+members of an array.
Arrays are assigned to using compound assignments of the form
- name=(value1 ... valueN)
-
-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.
-
- 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.
-
- 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.
+ NAME=(VALUE1 VALUE2 ... )
+ where each VALUE is of the form `[SUBSCRIPT]='STRING. Indexed array
+assignments do not require anything but STRING. 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 assigning to an associative array, the subscript is required.
+
+ This syntax is also accepted by the `declare' builtin. Individual
+array elements may be assigned to using the `NAME[SUBSCRIPT]=VALUE'
+syntax introduced above.
+
+ When assigning to an indexed array, if NAME is subscripted by a
+negative number, that number is interpreted as relative to one greater
+than the maximum index of NAME, so negative indices count back from the
+end of the array, and an index of -1 references the last element.
+
+ 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. If the
+SUBSCRIPT used to reference an element of an indexed array evaluates to
+a number less than zero, it is interpreted as relative to one greater
+than the maximum index of the array, so negative indices count back
+from the end of the array, and an index of -1 refers to the last
+element.
+
+ An array variable is considered set if a subscript has been assigned
+a value. The null string is a valid value.
+
+ It is possible to obtain the keys (indices) of an array as well as
+the values. ${!NAME[@]} and ${!NAME[*]} expand to the indices assigned
+in array variable NAME. The treatment when in double quotes is similar
+to the expansion of the special parameters `@' and `*' within double
+quotes.
+
+ The `unset' builtin is used to destroy arrays. `unset
+NAME[SUBSCRIPT]' destroys the array element at index SUBSCRIPT.
+Negative subscripts to indexed arrays are interpreted as described
+above. 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.
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.
+option to specify an indexed array and a `-A' option to specify an
+associative array. If both options are supplied, `-A' takes precedence.
+The `read' builtin accepts a `-a' option to assign a list of words read
+from the standard input to an array, and can read values from the
+standard input into individual array elements. The `set' and `declare'
+builtins display array values in a way that allows them to be reused as
+input.
\1f
-File: bashref.info, Node: The Directory Stack, Next: Printing a Prompt, Prev: Arrays, Up: Bash Features
+File: bashref.info, Node: The Directory Stack, Next: Controlling the Prompt, Prev: Arrays, Up: Bash Features
-The Directory Stack
-===================
+6.8 The Directory Stack
+=======================
* Menu:
\1f
File: bashref.info, Node: Directory Stack Builtins, Up: The Directory Stack
-Directory Stack Builtins
-------------------------
+6.8.1 Directory Stack Builtins
+------------------------------
`dirs'
- dirs [+N | -N] [-clpv]
+ dirs [-clpv] [+N | -N]
+
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.
-
- `-N'
- Displays the Nth directory (counting from the right of the
- list printed by `dirs' when invoked without options), starting
- with zero.
`-c'
Clears the directory stack by deleting all of the elements.
`-l'
- Produces a longer listing; the default listing format uses a
- tilde to denote the home directory.
+ Produces a listing using full pathnames; the default listing
+ format uses a tilde to denote the home directory.
`-p'
Causes `dirs' to print the directory stack with one entry per
Causes `dirs' to print the directory stack with one entry per
line, prefixing each entry with its index in the stack.
+ `+N'
+ Displays the Nth directory (counting from the left of the
+ list printed by `dirs' when invoked without options), starting
+ with zero.
+
+ `-N'
+ Displays the Nth directory (counting from the right of the
+ list printed by `dirs' when invoked without options), starting
+ with zero.
+
`popd'
- popd [+N | -N] [-n]
+ popd [-n] [+N | -N]
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'.
+ directory listed with `dirs'; that is, `popd' is equivalent to
+ `popd +0'.
+
+ `-n'
+ Suppresses the normal change of directory when removing
+ directories from the stack, so that only the stack is
+ manipulated.
+
`+N'
Removes the Nth directory (counting from the left of the list
printed by `dirs'), starting with zero.
Removes the Nth directory (counting from the right of the
list printed by `dirs'), starting with zero.
- `-n'
- Suppresses the normal change of directory when removing
- directories from the stack, so that only the stack is
- manipulated.
-
`pushd'
- pushd [DIR | +N | -N] [-n]
+ pushd [-n] [+N | -N | DIR]
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'
+ Suppresses the normal change of directory when adding
+ directories to the stack, so that only the stack is
+ manipulated.
+
`+N'
Brings the Nth directory (counting from the left of the list
printed by `dirs', starting with zero) to the top of the list
printed by `dirs', starting with zero) to the top of the list
by rotating the stack.
- `-n'
- Suppresses the normal change of directory when adding
- directories to the stack, so that only the stack is
- manipulated.
-
`DIR'
Makes the current working directory be the top of the stack,
- and then executes the equivalent of ``cd' DIR'. `cd's to DIR.
+ making it the new current directory as if it had been
+ supplied as an argument to the `cd' builtin.
\1f
-File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
+File: bashref.info, Node: Controlling the Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
-Controlling the Prompt
-======================
+6.9 Controlling the Prompt
+==========================
- The value of the variable `PROMPT_COMMAND' is examined just before
-Bash prints each primary prompt. If `PROMPT_COMMAND' is set and has a
+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.
In addition, the following table describes the special characters
-which can appear in the prompt variables:
+which can appear in the prompt variables `PS1' to `PS4':
`\a'
A bell character.
`\d'
The date, in "Weekday Month Date" format (e.g., "Tue May 26").
+`\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.
+
`\e'
An escape character.
`\@'
The time, in 12-hour am/pm format.
+`\A'
+ The time, in 24-hour HH:MM format.
+
`\u'
The username of the current user.
The release of Bash, version + patchlevel (e.g., 2.00.0)
`\w'
- The current working directory.
+ The current working directory, with `$HOME' abbreviated with a
+ tilde (uses the `$PROMPT_DIRTRIM' variable).
`\W'
- The basename of `$PWD'.
+ The basename of `$PWD', with `$HOME' abbreviated with a tilde.
`\!'
The history number of this command.
to the value of the `promptvars' shell option (*note Bash Builtins::).
\1f
-File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
+File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Controlling the Prompt, Up: Bash Features
-The Restricted Shell
-====================
+6.10 The Restricted Shell
+=========================
- If Bash is started with the name `rbash', or the `--restricted'
+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:
+with the exception that the following are disallowed or not performed:
+
* Changing directories with the `cd' builtin.
* Setting or unsetting the values of the `SHELL', `PATH', `ENV', or
* Adding or deleting builtin commands with the `-f' and `-d' options
to the `enable' builtin.
+ * Using the `enable' builtin command to enable disabled shell
+ builtins.
+
* Specifying the `-p' option to the `command' builtin.
* Turning off restricted mode with `set +r' or `set +o restricted'.
+ These restrictions are enforced after any startup files are read.
+
+ 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: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
-Bash POSIX Mode
-===============
+6.11 Bash POSIX Mode
+====================
+
+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.
- 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 1003.2 standard by changing the behavior to match
-that specified by POSIX in areas where the Bash default differs.
+ When invoked as `sh', Bash enters POSIX mode after reading the
+startup files.
The following list is what's changed when `POSIX mode' is in effect:
is stopped is `Stopped(SIGNAME)', where SIGNAME is, for example,
`SIGTSTP'.
- 4. Reserved words may not be aliased.
+ 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.
- 5. The POSIX 1003.2 `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.
+ 5. Reserved words appearing in a context where reserved words are
+ recognized do not undergo alias expansion.
- 6. Interactive comments are enabled by default. (Bash has them on by
- default anyway.)
+ 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.
- 7. The POSIX 1003.2 startup files are executed (`$ENV') rather than
- the normal Bash files.
+ 7. The POSIX startup files are executed (`$ENV') rather than the
+ normal Bash files.
8. Tilde expansion is only performed on assignments preceding a
command name, rather than on all assignment statements on the line.
- 9. The default history file is `~/.sh_history' (this is the default
+ 9. The `command' builtin does not prevent builtins that take
+ assignment statements as arguments from expanding them as
+ assignment statements; when not in POSIX mode, assignment builtins
+ lose their assignment statement expansion properties when preceded
+ by `command'.
+
+ 10. The default history file is `~/.sh_history' (this is the default
value of `$HISTFILE').
- 10. The output of `kill -l' prints all the signal names on a single
- line, separated by spaces.
+ 11. The output of `kill -l' prints all the signal names on a single
+ line, separated by spaces, without the `SIG' prefix.
- 11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
+ 12. The `kill' builtin does not accept signal names with a `SIG'
+ prefix.
+
+ 13. Non-interactive shells exit if FILENAME in `.' FILENAME is not
found.
- 12. Non-interactive shells exit if a syntax error in an arithmetic
+ 14. Non-interactive shells exit if a syntax error in an arithmetic
expansion results in an invalid expression.
- 13. Redirection operators do not perform filename expansion on the word
+ 15. 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.
+
+ 16. Redirection operators do not perform filename expansion on the word
in the redirection unless the shell is interactive.
- 14. Redirection operators do not perform word splitting on the word in
+ 17. Redirection operators do not perform word splitting on the word in
the redirection.
- 15. Function names must be valid shell `name's. That is, they may not
+ 18. 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.
- 16. POSIX 1003.2 `special' builtins are found before shell functions
- during command lookup.
+ 19. Function names may not be the same as one of the POSIX special
+ builtins.
+
+ 20. POSIX special builtins are found before shell functions during
+ command lookup.
+
+ 21. 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.
- 17. If a POSIX 1003.2 special builtin returns an error status, a
+ 22. When parsing and expanding a ${...} expansion that appears within
+ double quotes, single quotes are no longer special and cannot be
+ used to quote a closing brace or other special character, unless
+ the operator is one of those defined to perform pattern removal.
+ In this case, they do not have to appear as matched pairs.
+
+ 23. The parser does not recognize `time' as a reserved word if the next
+ token begins with a `-'.
+
+ 24. If a POSIX special builtin returns an error status, a
non-interactive shell exits. The fatal errors are those listed in
- the POSIX.2 standard, and include things like passing incorrect
+ the POSIX standard, and include things like passing incorrect
options, redirection errors, variable assignment errors for
assignments preceding the command name, and so on.
- 18. If the `cd' builtin finds a directory to change to using
- `$CDPATH', the value it assigns to the `PWD' variable does not
- contain any symbolic links, as if `cd -P' had been executed.
-
- 19. If `CDPATH' is set, the `cd' builtin will not implicitly append
- the current directory to it. This means that `cd' will fail if no
- valid directory name can be constructed from any of the entries in
- `$CDPATH', even if the a directory with the same name as the name
- given as an argument to `cd' exists in the current directory.
-
- 20. A non-interactive shell exits with an error status if a variable
+ 25. 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.
- 21. A non-interactive shell exits with an error status if the iteration
+ 26. A non-interactive shell exits 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.
+
+ 27. 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.
- 22. Process substitution is not available.
+ 28. Process substitution is not available.
+
+ 29. While variable indirection is available, it may not be applied to
+ the `#' and `?' special parameters.
- 23. Assignment statements preceding POSIX 1003.2 special builtins
- persist in the shell environment after the builtin completes.
+ 30. Assignment statements preceding POSIX special builtins persist in
+ the shell environment after the builtin completes.
- 24. Assignment statements preceding shell function calls persist in the
+ 31. 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.
- 25. The `export' and `readonly' builtin commands display their output
- in the format required by POSIX 1003.2.
+ 32. The `export' and `readonly' builtin commands display their output
+ in the format required by POSIX.
- 26. The `trap' builtin displays signal names without the leading `SIG'.
+ 33. The `trap' builtin displays signal names without the leading `SIG'.
- 27. The `.' and `source' builtins do not search the current directory
+ 34. 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.
+
+ 35. The `.' and `source' builtins do not search the current directory
for the filename argument if it is not found by searching `PATH'.
- 28. Subshells spawned to execute command substitutions inherit the
+ 36. 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.
- 29. Alias expansion is always enabled, even in non-interactive shells.
+ 37. Alias expansion is always enabled, even in non-interactive shells.
+
+ 38. When the `alias' builtin displays alias definitions, it does not
+ display them with a leading `alias ' unless the `-p' option is
+ supplied.
- 30. When the `set' builtin is invoked without options, it does not
+ 39. When the `set' builtin is invoked without options, it does not
display shell function names and definitions.
+ 40. 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.
+
+ 41. 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.
+
+ 42. 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.
+
+ 43. When listing the history, the `fc' builtin does not include an
+ indication of whether or not a history entry has been modified.
+
+ 44. The default editor used by `fc' is `ed'.
+
+ 45. 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
+ `$PATH'.
+
+ 46. The `vi' editing mode will invoke the `vi' editor directly when
+ the `v' command is run, instead of checking `$VISUAL' and
+ `$EDITOR'.
+
+ 47. 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.
- There is other POSIX 1003.2 behavior that Bash does not implement.
-Specifically:
+ 48. The `ulimit' builtin uses a block size of 512 bytes for the `-c'
+ and `-f' options.
- 1. Assignment statements affect the execution environment of all
- builtins, not just special ones.
+ 49. 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.
- 2. When a subshell is created to execute a shell script with execute
- permission, but without a leading `#!', Bash sets `$0' to the full
- pathname of the script as found by searching `$PATH', rather than
- the command as typed by the user.
+ 50. The `read' builtin may be interrupted by a signal for which a trap
+ has been set. If Bash receives a trapped signal while executing
+ `read', the trap handler executes and `read' returns an exit
+ status greater than 128.
- 3. When using `.' to source a shell script found in `$PATH', bash
- checks execute permission bits rather than read permission bits,
- just as if it were searching for a command.
+ There is other POSIX behavior that Bash does not implement by
+default even when in POSIX mode. Specifically:
+
+ 1. The `fc' builtin checks `$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.
+
+ 2. As noted above, Bash requires the `xpg_echo' option to be enabled
+ for the `echo' builtin to be fully conformant.
+
+
+ Bash can be configured to be POSIX-conformant by default, by
+specifying the `--enable-strict-posix-default' to `configure' when
+building (*note Optional Features::).
\1f
-File: bashref.info, Node: Job Control, Next: Using History Interactively, Prev: Bash Features, Up: Top
+File: bashref.info, Node: Job Control, Next: Command Line Editing, Prev: Bash Features, Up: Top
-Job Control
-***********
+7 Job Control
+*************
- This chapter discusses what job control is, how it works, and how
-Bash allows you to access its facilities.
+This chapter discusses what job control is, how it works, and how Bash
+allows you to access its facilities.
* Menu:
\1f
File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
-Job Control Basics
-==================
+7.1 Job Control Basics
+======================
- Job control refers to the ability to selectively stop (suspend) the
+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.
+interface supplied jointly by the operating system kernel's terminal
+driver and Bash.
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.
+ 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.
To facilitate the implementation of the user interface to job
control, the operating system maintains the notion of a current terminal
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.
+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.
If the operating system on which Bash is running supports job
control, Bash contains facilities to use it. Typing the SUSPEND
be discarded.
There are a number of ways to refer to a job in the shell. The
-character `%' introduces a job name.
+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. 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
-`-'.
+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.
+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.
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 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'
+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 the stopped jobs are terminated.
+another warning, and any stopped jobs are terminated.
\1f
File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
-Job Control Builtins
-====================
+7.2 Job Control Builtins
+========================
`bg'
- bg [JOBSPEC]
- Resume the suspended job JOBSPEC in the background, as if it had
+ 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, if
- JOBSPEC was not found or JOBSPEC specifies a job that was started
- without job control.
+ 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.
`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,
List only the process ID of the job's process group leader.
`-r'
- Restrict output to running jobs.
+ Display only running jobs.
`-s'
- Restrict output to stopped jobs.
+ Display only stopped jobs.
If JOBSPEC is given, output is restricted to information about
that job. If JOBSPEC is not supplied, the status of all jobs is
`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.
+ 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.
`wait'
- wait [JOBSPEC or 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
+ wait [-n] [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.
+ zero. If the `-n' option is supplied, `wait' waits for any job to
+ terminate and returns its exit status. If neither JOBSPEC nor PID
+ specifies an active child process of the shell, the return status
+ is 127.
`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.
+
+ Without options, remove each JOBSPEC 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 the `-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.
`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.
+ signal. A login shell cannot be suspended; the `-f' option can be
+ used to override this and force the suspension.
When job control is not active, the `kill' and `wait' builtins do
not accept JOBSPEC arguments. They must be supplied process IDs.
\1f
File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
-Job Control Variables
-=====================
+7.3 Job Control Variables
+=========================
`auto_resume'
This variable controls how the shell interacts with the user and
a prefix of a stopped job's name; this provides functionality
analogous to the `%' job ID.
+
\1f
-File: bashref.info, Node: Command Line Editing, Next: Installing Bash, Prev: Using History Interactively, Up: Top
+File: bashref.info, Node: Command Line Editing, Next: Using History Interactively, Prev: Job Control, Up: Top
-Command Line Editing
-********************
+8 Command Line Editing
+**********************
- This chapter describes the basic features of the GNU command line
+This chapter describes the basic features of the GNU command line
editing interface. Command line editing is provided by the Readline
library, which is used by several different programs, including Bash.
+Command line editing is enabled by default when using an interactive
+shell, unless the `--noediting' option is supplied at shell invocation.
+Line editing is also used when using the `-e' option to the `read'
+builtin command (*note Bash Builtins::). By default, the line editing
+commands are similar to those of Emacs. A vi-style line editing
+interface is also available. Line editing can be enabled at any time
+using the `-o emacs' or `-o vi' options to the `set' builtin command
+(*note The Set Builtin::), or disabled using the `+o emacs' or `+o vi'
+options to `set'.
* Menu:
a specific command.
* Programmable Completion Builtins:: Builtin commands to specify how to
complete arguments for a particular command.
+* A Programmable Completion Example:: An example shell function for
+ generating possible completions.
\1f
File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
-Introduction to Line Editing
-============================
+8.1 Introduction to Line Editing
+================================
- The following paragraphs describe the notation used to represent
+The following paragraphs describe the notation used to represent
keystrokes.
The text `C-k' is read as `Control-K' and describes the character
\1f
File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
-Readline Interaction
-====================
+8.2 Readline Interaction
+========================
- Often during an interactive session you type in a long line of text,
+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
\1f
File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
-Readline Bare Essentials
-------------------------
+8.2.1 Readline Bare Essentials
+------------------------------
- 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.
+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.
Sometimes you may mistype a character, and not notice the error
until you have typed several other characters. In that case, you can
\1f
File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
-Readline Movement Commands
---------------------------
+8.2.2 Readline Movement Commands
+--------------------------------
- The above table describes the most basic keystrokes that you need in
+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.
\1f
File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
-Readline Killing Commands
--------------------------
+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
+"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'.)
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.
+available to be yanked back later, when you are typing another line.
Here is the list of commands for killing text.
as those used by `M-f'.
`M-<DEL>'
- Kill from the cursor the start of the previous word, or, if between
+ 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'.
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.
\1f
File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
-Readline Arguments
-------------------
+8.2.4 Readline Arguments
+------------------------
- You can pass numeric arguments to Readline commands. Sometimes the
+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
\1f
File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
-Searching for Commands in the History
--------------------------------------
+8.2.5 Searching for Commands in the History
+-------------------------------------------
- Readline provides commands for searching through the command 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".
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
-Readline Init File
-==================
+8.3 Readline Init File
+======================
- Although the Readline library comes with a set of Emacs-like
+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'.
+`~/.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.
\1f
File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
-Readline Init File Syntax
--------------------------
+8.3.1 Readline Init File Syntax
+-------------------------------
- There are only a few basic constructs allowed in the Readline init
+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
set editing-mode vi
Variable names and values, where appropriate, are recognized
- without regard to case.
+ 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::.
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.
+
+ `colored-stats'
+ If set to `on', Readline displays possible completions using
+ different colors to indicate their file type. The color
+ definitions are taken from the value of the `LS_COLORS'
+ environment variable. The default is `off'.
+
`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 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. This variable must be set to an integer value
- greater than or equal to 0. The default limit is `100'.
+ 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
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, any existing history entries
+ are deleted and no new entries are saved. If set to a value
+ less than zero, the number of history entries is not limited.
+ By default, the number of history entries 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
default value is `emacs'. The value of the `editing-mode'
variable also affects the default keymap.
+ `keyseq-timeout'
+ Specifies the duration Readline will wait for a character
+ when reading an ambiguous key sequence (one that can form a
+ complete key sequence using the input read so far, or can
+ take additional input to complete a longer key sequence). If
+ no input is received within the timeout, Readline will use
+ the shorter but complete key sequence. Readline uses this
+ value to determine whether or not input is available on the
+ current input source (`rl_instream' by default). The value
+ is specified in milliseconds, so a value of 1000 means that
+ Readline will wait one second for additional input. If this
+ variable is set to a value less than or equal to zero, or to a
+ non-numeric value, Readline will wait until another key is
+ pressed to decide which key sequence to complete. The
+ default value is `500'.
+
`mark-directories'
If set to `on', completed directory names have a slash
appended. The default is `on'.
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'.
+
+ `show-mode-in-prompt'
+ If set to `on', add a character to the beginning of the prompt
+ indicating the editing mode: emacs (`@'), vi command (`:'),
+ or vi insertion (`+'). 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
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. The name of the key
- can be expressed in different ways, depending on what you find most
- comfortable.
+ 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).
`<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:
vertical tab
`\NNN'
- the character whose ASCII code is the octal value NNN (one to
- three digits)
-
- `\xNNN'
- the character whose ASCII code is the hexadecimal value 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
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
-Conditional Init Constructs
----------------------------
+8.3.2 Conditional Init Constructs
+---------------------------------
- Readline implements a facility similar in spirit to the conditional
+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.
\1f
File: bashref.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
-Sample 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.
+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.
+ # 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
+ # First, include any system-wide 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-\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
+ # 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)
+ # insert a backslash (testing backslash escapes
+ # in sequences and macros)
"\C-x\\": "\\"
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
# 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
+
+ # 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
+
+ # 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
+
+ # 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-?"
\1f
File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
-Bindable Readline Commands
-==========================
+8.4 Bindable Readline Commands
+==============================
* Menu:
\1f
File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
-Commands For Moving
--------------------
+8.4.1 Commands For Moving
+-------------------------
`beginning-of-line (C-a)'
Move to the start of the current line.
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
-Commands For Manipulating The History
--------------------------------------
+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
`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
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. 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
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. By default, this command is unbound.
+
+`history-substr-search-forward ()'
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a
+ non-incremental search. By default, this command is unbound.
+
+`history-substr-search-backward ()'
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a
non-incremental search. By default, this command is unbound.
`yank-nth-arg (M-C-y)'
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.
+ the Nth word from the end of the previous command. Once the
+ argument N is computed, the argument is extracted as if the `!N'
+ history expansion had been specified.
`yank-last-arg (M-. or M-_)'
Insert last argument to the previous command (the last word of the
- previous history entry). With an argument, behave exactly like
- `yank-nth-arg'. Successive calls to `yank-last-arg' move back
- through the history list, inserting the last argument of each line
- in turn.
+ 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
-Commands For Changing Text
---------------------------
+8.4.3 Commands For Changing Text
+--------------------------------
+
+`end-of-file (usually C-d)'
+ The character indicating end-of-file as set, for example, by
+ `stty'. If this character is read when there are no characters on
+ the line, and point is at the beginning of the line, Readline
+ interprets it as the end of input and returns EOF.
`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.
+ Delete the character at point. If this function is bound to the
+ same character as the tty EOF character, as `C-d' commonly is, see
+ above for the effects.
`backward-delete-char (Rubout)'
Delete the character behind the cursor. A numeric argument means
`transpose-words (M-t)'
Drag the word before point past the word after point, moving point
- past that word as well.
+ 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
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
-Killing And Yanking
--------------------
+8.4.4 Killing And Yanking
+-------------------------
`kill-line (C-k)'
Kill the text from point to the end of the line.
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.
\1f
File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
-Specifying Numeric Arguments
-----------------------------
+8.4.5 Specifying Numeric Arguments
+----------------------------------
`digit-argument (M-0, M-1, ... M--)'
Add this digit to the argument already accumulating, or start a new
\1f
File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
-Letting Readline Type For You
------------------------------
+8.4.6 Letting Readline Type For You
+-----------------------------------
`complete (<TAB>)'
Attempt to perform completion on the text before point. The
completion is attempted.
`possible-completions (M-?)'
- List the possible completions of the text before point.
+ 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
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,
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
-Keyboard Macros
----------------
+8.4.7 Keyboard Macros
+---------------------
`start-kbd-macro (C-x ()'
Begin saving the characters typed into the current keyboard macro.
Re-execute the last keyboard macro defined, by making the
characters in the macro appear as if typed at the keyboard.
+`print-last-kbd-macro ()'
+ Print the last keboard macro defined in a format suitable for the
+ INPUTRC file.
+
+
\1f
File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
-Some Miscellaneous 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
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-#)'
- 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. The default value of `comment-begin'
- causes this command to make the current line a shell comment.
+ 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 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.
+ 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.
+ `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.
relative to the current line from the history for editing. Any
argument is ignored.
-`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.
+`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.
+
\1f
File: bashref.info, Node: Readline vi Mode, Next: Programmable Completion, Prev: Bindable Readline Commands, Up: Command Line Editing
-Readline vi Mode
-================
+8.5 Readline vi Mode
+====================
- While the Readline library does not have a full set of `vi' editing
+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.
+The Readline `vi' mode behaves as specified in the POSIX standard.
In order to switch interactively between `emacs' and `vi' editing
modes, use the `set -o emacs' and `set -o vi' commands (*note The Set
\1f
File: bashref.info, Node: Programmable Completion, Next: Programmable Completion Builtins, Prev: Readline vi Mode, Up: Command Line Editing
-Programmable Completion
-=======================
+8.6 Programmable Completion
+===========================
- When word completion is attempted for an argument to a command for
+When word completion is attempted for an argument to a command for
which a completion specification (a COMPSPEC) has been defined using
the `complete' builtin (*note Programmable Completion Builtins::), the
programmable completion facilities are invoked.
First, the command name is identified. If a compspec has been
defined for that command, the compspec is used to generate the list of
-possible completions for the word. If the command word is a full
-pathname, a compspec for the full pathname is searched for first. If
-no compspec is found for the full pathname, an attempt is made to find
-a compspec for the portion following the final slash.
+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
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, arithmetic expansion, and
-pathname 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.
+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' and `COMP_POINT'
-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.
+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 ($1) is the name of
+the command whose arguments are being completed, the second argument
+($2) is the word being completed, and the third argument ($3) 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' builtin
-described below (*note Programmable Completion Builtins::), to generate
-the matches. It must put the possible completions in the `COMPREPLY'
-array variable.
+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, one per array element.
Next, any command specified with the `-C' option is invoked in an
environment equivalent to command substitution. It should print a list
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 default' option was
-supplied to `complete' when the compspec was defined, Readline's
-default completion will be performed if the compspec generates no
+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 -o bashdefault -o default
+
\1f
-File: bashref.info, Node: Programmable Completion Builtins, Prev: Programmable Completion, Up: Command Line Editing
+File: bashref.info, Node: Programmable Completion Builtins, Next: A Programmable Completion Example, Prev: Programmable Completion, Up: Command Line Editing
-Programmable Completion Builtins
-================================
+8.7 Programmable Completion Builtins
+====================================
- Two builtin commands are available to manipulate the programmable
-completion facilities.
+Three builtin commands are available to manipulate the programmable
+completion facilities: one to specify how the arguments to a particular
+command are to be completed, and two to modify the completion as it is
+happening.
`compgen'
`compgen [OPTION] [WORD]'
no matches were generated.
`complete'
- `complete [-abcdefjkvu] [-o COMP-OPTION] [-A ACTION] [-G GLOBPAT] [-W WORDLIST]
- [-P PREFIX] [-S SUFFIX] [-X FILTERPAT] [-F FUNCTION]
- [-C COMMAND] NAME [NAME ...]'
- `complete -pr [NAME ...]'
+ `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.
+ 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::).
+ 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,
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 completion if the compspec
- generates no matches.
+ Use Readline's default filename completion if the
+ compspec generates no matches.
`dirnames'
Perform directory name completion if the compspec
`filenames'
Tell Readline that the compspec generates filenames, so
- it can perform any filename\-specific processing (like
- adding a slash to directory names or suppressing
- trailing spaces). This option is intended to be used
- with shell functions specified with `-F'.
+ 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'.
+
+ `noquote'
+ Tell Readline not to quote the completed words if they
+ are filenames (quoting filenames is the default).
+
+ `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
`function'
Names of shell functions.
+ `group'
+ Group names. May also be specified as `-g'.
+
`helptopic'
Help topics as accepted by the `help' builtin (*note
Bash Builtins::).
`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::).
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 is executed, $1 is the name of the
+ command whose arguments are being completed, $2 is the word
+ being completed, and $3 is the word preceding the word being
+ completed, as described above (*note Programmable
+ Completion::). 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.
- `-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.
-
`-X FILTERPAT'
FILTERPAT is a pattern as used for filename expansion. It is
applied to the list of possible completions generated by the
FILTERPAT negates the pattern; in this case, any completion
not matching FILTERPAT is removed.
- `-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.
-
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.
+
+
+\1f
+File: bashref.info, Node: A Programmable Completion Example, Prev: Programmable Completion Builtins, Up: Command Line Editing
+
+8.8 A Programmable Completion Example
+=====================================
+
+The most common way to obtain additional completion functionality beyond
+the default actions `complete' and `compgen' provide is to use a shell
+function and bind it to a particular command using `complete -F'.
+
+ The following function provides completions for the `cd' builtin.
+It is a reasonably good example of what shell functions must do when
+used for completion. This function uses the word passsed as `$2' to
+determine the directory name to complete. You can also use the
+`COMP_WORDS' array variable; the current word is indexed by the
+`COMP_CWORD' variable.
+
+ The function relies on the `complete' and `compgen' builtins to do
+much of the work, adding only the things that the Bash `cd' does beyond
+accepting basic directory names: tilde expansion (*note Tilde
+Expansion::), searching directories in $CDPATH, which is described above
+(*note Bourne Shell Builtins::), and basic support for the
+`cdable_vars' shell option (*note The Shopt Builtin::). `_comp_cd'
+modifies the value of IFS so that it contains only a newline to
+accommodate file names containing spaces and tabs - `compgen' prints
+the possible completions it generates one per line.
+
+ Possible completions go into the COMPREPLY array variable, one
+completion per array element. The programmable completion system
+retrieves the completions from there when the function returns.
+
+ # A completion function for the cd builtin
+ # based on the cd completion function from the bash_completion package
+ _comp_cd()
+ {
+ local IFS=$' \t\n' # normalize IFS
+ local cur _skipdot _cdpath
+ local i j k
+
+ # Tilde expansion, with side effect of expanding tilde to full pathname
+ case "$2" in
+ \~*) eval cur="$2" ;;
+ *) cur=$2 ;;
+ esac
+
+ # no cdpath or absolute pathname -- straight directory completion
+ if [[ -z "${CDPATH:-}" ]] || [[ "$cur" == @(./*|../*|/*) ]]; then
+ # compgen prints paths one per line; could also use while loop
+ IFS=$'\n'
+ COMPREPLY=( $(compgen -d -- "$cur") )
+ IFS=$' \t\n'
+ # CDPATH+directories in the current directory if not in CDPATH
+ else
+ IFS=$'\n'
+ _skipdot=false
+ # preprocess CDPATH to convert null directory names to .
+ _cdpath=${CDPATH/#:/.:}
+ _cdpath=${_cdpath//::/:.:}
+ _cdpath=${_cdpath/%:/:.}
+ for i in ${_cdpath//:/$'\n'}; do
+ if [[ $i -ef . ]]; then _skipdot=true; fi
+ k="${#COMPREPLY[@]}"
+ for j in $( compgen -d -- "$i/$cur" ); do
+ COMPREPLY[k++]=${j#$i/} # cut off directory
+ done
+ done
+ $_skipdot || COMPREPLY+=( $(compgen -d -- "$cur") )
+ IFS=$' \t\n'
+ fi
+
+ # variable names if appropriate shell option set and no completions
+ if shopt -q cdable_vars && [[ ${#COMPREPLY[@]} -eq 0 ]]; then
+ COMPREPLY=( $(compgen -v -- "$cur") )
+ fi
+
+ return 0
+ }
+
+ We install the completion function using the `-F' option to
+`complete':
+
+ # Tell readline to quote appropriate and append slashes to directories;
+ # use the bash default completion for other arguments
+ complete -o filenames -o nospace -o bashdefault -F _comp_cd cd
+
+Since we'd like Bash and Readline to take care of some of the other
+details for us, we use several other options to tell Bash and Readline
+what to do. The `-o filenames' option tells Readline that the possible
+completions should be treated as filenames, and quoted appropriately.
+That option will also cause Readline to append a slash to filenames it
+can determine are directories (which is why we might want to extend
+`_comp_cd' to append a slash if we're using directories found via
+CDPATH: Readline can't tell those completions are directories). The
+`-o nospace' option tells Readline to not append a space character to
+the directory name, in case we want to append to it. The `-o
+bashdefault' option brings in the rest of the "Bash default"
+completions - possible completion that Bash adds to the default Readline
+set. These include things like command name completion, variable
+completion for words beginning with `{', completions containing pathname
+expansion patterns (*note Filename Expansion::), and so on.
+
+ Once installed using `complete', `_comp_cd' will be called every
+time we attempt word completion for a `cd' command.
+
+ Many more examples - an extensive collection of completions for most
+of the common GNU, Unix, and Linux commands - are available as part of
+the bash_completion project. This is installed by default on many
+GNU/Linux distributions. Originally written by Ian Macdonald, the
+project now lives at `http://bash-completion.alioth.debian.org/'.
+There are ports for other systems such as Solaris and Mac OS X.
+
+ An older version of the bash_completion package is distributed with
+bash in the `examples/complete' subdirectory.
+
\1f
-File: bashref.info, Node: Using History Interactively, Next: Command Line Editing, Prev: Job Control, Up: Top
+File: bashref.info, Node: Using History Interactively, Next: Installing Bash, Prev: Command Line Editing, Up: Top
-Using History Interactively
-***************************
+9 Using History Interactively
+*****************************
- This chapter describes how to use the GNU History Library
+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.
\1f
File: bashref.info, Node: Bash History Facilities, Next: Bash History Builtins, Up: Using History Interactively
-Bash History Facilities
-=======================
+9.1 Bash History Facilities
+===========================
- 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 `$HISTSIZE' commands (default 500) is saved.
-The shell stores each command in the history list prior to parameter
-and variable expansion but after history expansion is performed,
-subject to the values of the shell variables `HISTIGNORE' and
-`HISTCONTROL'.
+When the `-o history' option to the `set' builtin is enabled (*note The
+Set Builtin::), the shell provides access to the "command history", the
+list of commands previously typed. The value of the `HISTSIZE' shell
+variable is used as the number of commands to save in a history list.
+The text of the last `$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
+`HISTFILESIZE' variable. When a shell with history enabled 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
-`$HISTFILESIZE' lines. If `HISTFILESIZE' is not set, no truncation is
-performed.
+`$HISTFILESIZE' lines. If `HISTFILESIZE' is unset, or set to null, a
+non-numeric value, or a numeric value less than zero, the history file
+is not truncated.
+
+ 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.
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
\1f
File: bashref.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
-Bash History Builtins
-=====================
+9.2 Bash History Builtins
+=========================
- Bash provides two builtin commands which manipulate the history list
+Bash provides two builtin commands which manipulate the history list
and history file.
`fc'
- `fc [-e ENAME] [-nlr] [FIRST] [LAST]'
+ `fc [-e ENAME] [-lnr] [FIRST] [LAST]'
`fc -s [PAT=REP] [COMMAND]'
- 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.
+ The first form selects a range of commands from FIRST to LAST from
+ the history list and displays or edits and re-executes them. 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.
In the second form, COMMAND is re-executed after each instance of
- PAT in the selected command is replaced by REP.
+ PAT in the selected command is replaced by REP. COMMAND is
+ intepreted the same as FIRST above.
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
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. Options, if supplied, have the
- following meanings:
+ 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.
+
+ Options, if supplied, have the following meanings:
`-c'
Clear the history list. This may be combined with the other
session.
`-r'
- Read the current history file and append its contents to the
- history list.
+ Read the history file and append its contents to the history
+ list.
`-w'
- Write out the current history to the history file.
+ Write out the current history list to the history file.
`-p'
Perform history substitution on the ARGs and display the
The ARGs are added to the end of the history list as a single
entry.
+
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.
+
\1f
File: bashref.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
-History Expansion
-=================
+9.3 History Expansion
+=====================
- 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 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.
History expansions introduce words from the history list into the
input stream, making it easy to repeat commands, insert the arguments
with Readline.
The shell allows control of the various characters used by the
-history expansion mechanism with the `histchars' variable.
+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.
* Menu:
\1f
File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
-Event Designators
------------------
+9.3.1 Event Designators
+-----------------------
- An event designator is a reference to a command line entry in the
-history list.
+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.
`!'
Start a history substitution, except when followed by a space, tab,
- the end of the line, `=' or `('.
+ the end of the line, `=' or `(' (when the `extglob' shell option
+ is enabled using the `shopt' builtin).
`!N'
Refer to command line N.
Refer to the previous command. This is a synonym for `!-1'.
`!STRING'
- Refer to the most recent command starting with STRING.
+ Refer to the most recent command preceding the current position in
+ the history list starting with STRING.
`!?STRING[?]'
- Refer to the most recent command containing STRING. The trailing
- `?' may be omitted if the STRING is followed immediately by a
- newline.
+ 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.
`^STRING1^STRING2^'
Quick Substitution. Repeat the last command, replacing STRING1
`!#'
The entire command line typed so far.
+
\1f
File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
-Word Designators
-----------------
+9.3.2 Word Designators
+----------------------
- Word designators are used to select desired words from the event. A
+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 `^', `$', `*', `-', or
`%'. Words are numbered from the beginning of the line, with the first
`X-'
Abbreviates `X-$' like `X*', but omits the last word.
+
If a word designator is supplied without an event specification, the
previous command is used as the event.
\1f
File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
-Modifiers
----------
+9.3.3 Modifiers
+---------------
- After the optional word designator, you can add a sequence of one or
+After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.
`h'
Remove a trailing pathname component, leaving only the head.
`t'
- Remove all leading pathname components, leaving the tail.
+ Remove all leading pathname components, leaving the tail.
`r'
Remove a trailing suffix of the form `.SUFFIX', leaving the
Repeat the previous substitution.
`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.
+
+
\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
+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, Windows 95/98, and Windows NT.
+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
-==================
+10.1 Basic Installation
+=======================
- These are installation instructions for Bash.
+These are installation instructions for Bash.
The simplest way to compile Bash is:
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
+ The file `configure.ac' is used to create `configure' by a program
+called Autoconf. You only need `configure.ac' 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.
-
- 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.
+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
\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
\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.
\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
\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
-`bash-malloc' or `purify'. To turn off the default use of a package,
-use `--without-PACKAGE'. To configure Bash without a feature that is
+The Bash `configure' has a number of `--enable-FEATURE' options, where
+FEATURE indicates an optional part of Bash. There are also several
+`--with-PACKAGE' options, where PACKAGE is something like `bash-malloc'
+or `purify'. To turn off the default use of a package, use
+`--without-PACKAGE'. To configure Bash without a feature that is
enabled by default, use `--disable-FEATURE'.
Here is a complete list of the `--enable-' and `--with-' options
Define if you are using the Andrew File System from Transarc.
`--with-bash-malloc'
- Use the Bash 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.
+ 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 certain circumstances.
-
`--with-gnu-malloc'
A synonym for `--with-bash-malloc'.
-`--with-installed-readline'
+`--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 4.1 and later versions.
+ 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
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.
following options, but it is processed first, so individual options may
be enabled using `enable-FEATURE'.
- All of the following options except for `disabled-builtins' and
-`xpg-echo-default' are enabled by default, unless the operating system
-does not provide the necessary support.
+ All of the following options except for `disabled-builtins',
+`directpand-default', and `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'
`--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
builtins and functions to be timed.
`--enable-cond-command'
- Include support for the `[[' conditional command (*note
+ 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-direxpand-default'
+ Cause the `direxpand' shell option (*note The Shopt Builtin::) to
+ be enabled by default when the shell starts. It is normally
+ disabled by default.
+
`--enable-directory-stack'
Include support for a `csh'-like directory stack and the `pushd',
`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-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-glob-asciirange-default'
+ Set the default value of the GLOBASCIIRANGES shell option described
+ above under *note The Shopt Builtin:: to be enabled. This
+ controls the behavior of character ranges when used in pattern
+ matching bracket expressions.
`--enable-help-builtin'
Include the `help' builtin, which displays help on shell builtins
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
This enables process substitution (*note Process Substitution::) if
the operating system provides the necessary support.
-`--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
- prompt string escape sequences.
-
`--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 Controlling the 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::).
`--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'.
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 2. *Note Bash Builtins::, for a
+ Specification, version 3. *Note Bash Builtins::, for a
description of the escape sequences that `echo' recognizes.
The file `config-top.h' contains C Preprocessor `#define' statements
\1f
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 <bug-bash@gnu.org>.
\1f
-File: bashref.info, Node: Major Differences From The Bourne Shell, Next: Builtin Index, Prev: Reporting Bugs, Up: Top
+File: bashref.info, Node: Major Differences From The Bourne Shell, Next: GNU Free Documentation License, Prev: Reporting Bugs, Up: Top
-Major Differences From The Bourne Shell
-***************************************
+Appendix B Major Differences From The Bourne Shell
+**************************************************
- Bash implements essentially the same grammar, parameter and variable
+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
+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 as the baseline reference.
+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::).
the `bind' builtin.
* Bash provides a programmable word completion mechanism (*note
- Programmable Completion::), and two builtin commands, `complete'
- and `compgen', to manipulate it.
+ 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.
+ `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 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.
+ 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
generation of simple menus (*note Conditional Constructs::).
* Bash includes the `[[' compound command, which makes conditional
- testing part of the shell grammar (*note Conditional Constructs::).
+ 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::).
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::).
PATTERN and replaces it with REPLACEMENT in the value of `var', is
available (*note Shell Parameter Expansion::).
- * The expansion `${!PREFIX}*' expansion, which expands to the names
+ * The expansion `${!PREFIX*}' expansion, which expands to the names
of all shell variables whose names begin with PREFIX, is available
(*note Shell Parameter Expansion::).
not all words (*note Word Splitting::). This closes a
longstanding shell security hole.
- * Bash implements the full set of POSIX 1003.2 filename expansion
- operators, including CHARACTER CLASSES, EQUIVALENCE CLASSES, and
- COLLATING SYMBOLS (*note Filename Expansion::).
+ * The filename expansion bracket expression code uses `!' and `^' to
+ negate the set of characters between the brackets. The Bourne
+ shell uses only `!'.
+
+ * 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::).
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::).
Builtins::).
* Bash includes the `shopt' builtin, for finer control of shell
- optional capabilities (*note Bash Builtins::).
+ 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 after every simple
- command. The `DEBUG' trap is not inherited by shell functions.
+ 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::).
as the value of the `DIRSTACK' shell variable.
* Bash interprets special backslash-escaped characters in the prompt
- strings when interactive (*note Printing a Prompt::).
+ strings when interactive (*note Controlling the Prompt::).
* The Bash restricted mode is more useful (*note The Restricted
Shell::); the SVR4.2 shell restricted mode is too limited.
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.
* The SVR4.2 `sh' uses a `TIMEOUT' variable like Bash uses `TMOUT'.
-More features unique to Bash may be found in *Note Bash Features::.
+More features unique to Bash may be found in *note Bash Features::.
-Implementation Differences From The SVR4.2 Shell
-================================================
+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:
+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.
begins with a `-'.
* The SVR4.2 shell exits a script if any builtin fails; Bash exits a
- script only if one of the POSIX 1003.2 special builtins fails, and
- only for certain failures, as enumerated in the POSIX 1003.2
- standard.
+ 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: Builtin Index, Next: Reserved Word Index, Prev: Major Differences From The Bourne Shell, Up: Top
+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
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+
+ A "Secondary Section" is a named appendix or a front-matter section
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+ The "Invariant Sections" are certain Secondary Sections whose
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+ The "Cover Texts" are certain short passages of text that are
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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
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+ works in formats which do not have any title page as such, "Title
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+ The "publisher" means any person or entity that distributes copies
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+ 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
+ "Acknowledgements", "Dedications", "Endorsements", or "History".)
+ To "Preserve the Title" of such a section when you modify the
+ Document means that it remains a section "Entitled XYZ" according
+ to this definition.
+
+ The Document may include Warranty Disclaimers next to the notice
+ which states that this License applies to the Document. These
+ Warranty Disclaimers are considered to be included by reference in
+ this License, but only as regards disclaiming warranties: any other
+ implication that these Warranty Disclaimers may have is void and
+ has no effect on the meaning of this License.
+
+ 2. VERBATIM COPYING
+
+ You may copy and distribute the Document in any medium, either
+ commercially or noncommercially, provided that this License, the
+ copyright notices, and the license notice saying this License
+ applies to the Document are reproduced in all copies, and that you
+ add no other conditions whatsoever to those of this License. You
+ may not use technical measures to obstruct or control the reading
+ or further copying of the copies you make or distribute. However,
+ you may accept compensation in exchange for copies. If you
+ distribute a large enough number of copies you must also follow
+ the conditions in section 3.
+
+ You may also lend copies, under the same conditions stated above,
+ and you may publicly display copies.
+
+ 3. COPYING IN QUANTITY
+
+ If you publish printed copies (or copies in media that commonly
+ have printed covers) of the Document, numbering more than 100, and
+ the Document's license notice requires Cover Texts, you must
+ enclose the copies in covers that carry, clearly and legibly, all
+ these Cover Texts: Front-Cover Texts on the front cover, and
+ Back-Cover Texts on the back cover. Both covers must also clearly
+ and legibly identify you as the publisher of these copies. The
+ front cover must present the full title with all words of the
+ title equally prominent and visible. You may add other material
+ on the covers in addition. Copying with changes limited to the
+ covers, as long as they preserve the title of the Document and
+ satisfy these conditions, can be treated as verbatim copying in
+ other respects.
+
+ If the required texts for either cover are too voluminous to fit
+ legibly, you should put the first ones listed (as many as fit
+ reasonably) on the actual cover, and continue the rest onto
+ adjacent pages.
+
+ If you publish or distribute Opaque copies of the Document
+ numbering more than 100, you must either include a
+ machine-readable Transparent copy along with each Opaque copy, or
+ state in or with each Opaque copy a computer-network location from
+ which the general network-using public has access to download
+ using public-standard network protocols a complete Transparent
+ copy of the Document, free of added material. If you use the
+ latter option, you must take reasonably prudent steps, when you
+ begin distribution of Opaque copies in quantity, to ensure that
+ this Transparent copy will remain thus accessible at the stated
+ location until at least one year after the last time you
+ distribute an Opaque copy (directly or through your agents or
+ retailers) of that edition to the public.
+
+ It is requested, but not required, that you contact the authors of
+ the Document well before redistributing any large number of
+ copies, to give them a chance to provide you with an updated
+ version of the Document.
+
+ 4. MODIFICATIONS
+
+ You may copy and distribute a Modified Version of the Document
+ under the conditions of sections 2 and 3 above, provided that you
+ release the Modified Version under precisely this License, with
+ the Modified Version filling the role of the Document, thus
+ licensing distribution and modification of the Modified Version to
+ whoever possesses a copy of it. In addition, you must do these
+ things in the Modified Version:
+
+ A. Use in the Title Page (and on the covers, if any) a title
+ distinct from that of the Document, and from those of
+ previous versions (which should, if there were any, be listed
+ in the History section of the Document). You may use the
+ same title as a previous version if the original publisher of
+ that version gives permission.
+
+ B. List on the Title Page, as authors, one or more persons or
+ entities responsible for authorship of the modifications in
+ the Modified Version, together with at least five of the
+ principal authors of the Document (all of its principal
+ authors, if it has fewer than five), unless they release you
+ from this requirement.
+
+ C. State on the Title page the name of the publisher of the
+ Modified Version, as the publisher.
+
+ D. Preserve all the copyright notices of the Document.
+
+ E. Add an appropriate copyright notice for your modifications
+ adjacent to the other copyright notices.
+
+ F. Include, immediately after the copyright notices, a license
+ notice giving the public permission to use the Modified
+ Version under the terms of this License, in the form shown in
+ the Addendum below.
+
+ G. Preserve in that license notice the full lists of Invariant
+ Sections and required Cover Texts given in the Document's
+ license notice.
+
+ H. Include an unaltered copy of this License.
+
+ I. Preserve the section Entitled "History", Preserve its Title,
+ and add to it an item stating at least the title, year, new
+ authors, and publisher of the Modified Version as given on
+ the Title Page. If there is no section Entitled "History" in
+ the Document, create one stating the title, year, authors,
+ and publisher of the Document as given on its Title Page,
+ then add an item describing the Modified Version as stated in
+ the previous sentence.
+
+ J. Preserve the network location, if any, given in the Document
+ for public access to a Transparent copy of the Document, and
+ likewise the network locations given in the Document for
+ previous versions it was based on. These may be placed in
+ the "History" section. You may omit a network location for a
+ work that was published at least four years before the
+ Document itself, or if the original publisher of the version
+ it refers to gives permission.
+
+ K. For any section Entitled "Acknowledgements" or "Dedications",
+ Preserve the Title of the section, and preserve in the
+ section all the substance and tone of each of the contributor
+ acknowledgements and/or dedications given therein.
+
+ L. Preserve all the Invariant Sections of the Document,
+ unaltered in their text and in their titles. Section numbers
+ or the equivalent are not considered part of the section
+ titles.
+
+ M. Delete any section Entitled "Endorsements". Such a section
+ may not be included in the Modified Version.
+
+ N. Do not retitle any existing section to be Entitled
+ "Endorsements" or to conflict in title with any Invariant
+ Section.
+
+ O. Preserve any Warranty Disclaimers.
+
+ If the Modified Version includes new front-matter sections or
+ appendices that qualify as Secondary Sections and contain no
+ material copied from the Document, you may at your option
+ designate some or all of these sections as invariant. To do this,
+ add their titles to the list of Invariant Sections in the Modified
+ Version's license notice. These titles must be distinct from any
+ other section titles.
+
+ You may add a section Entitled "Endorsements", provided it contains
+ nothing but endorsements of your Modified Version by various
+ parties--for example, statements of peer review or that the text
+ has been approved by an organization as the authoritative
+ definition of a standard.
+
+ You may add a passage of up to five words as a Front-Cover Text,
+ and a passage of up to 25 words as a Back-Cover Text, to the end
+ of the list of Cover Texts in the Modified Version. Only one
+ passage of Front-Cover Text and one of Back-Cover Text may be
+ added by (or through arrangements made by) any one entity. If the
+ Document already includes a cover text for the same cover,
+ previously added by you or by arrangement made by the same entity
+ you are acting on behalf of, you may not add another; but you may
+ replace the old one, on explicit permission from the previous
+ publisher that added the old one.
+
+ The author(s) and publisher(s) of the Document do not by this
+ License give permission to use their names for publicity for or to
+ assert or imply endorsement of any Modified Version.
+
+ 5. COMBINING DOCUMENTS
+
+ You may combine the Document with other documents released under
+ this License, under the terms defined in section 4 above for
+ modified versions, provided that you include in the combination
+ all of the Invariant Sections of all of the original documents,
+ unmodified, and list them all as Invariant Sections of your
+ combined work in its license notice, and that you preserve all
+ their Warranty Disclaimers.
+
+ The combined work need only contain one copy of this License, and
+ multiple identical Invariant Sections may be replaced with a single
+ copy. If there are multiple Invariant Sections with the same name
+ but different contents, make the title of each such section unique
+ by adding at the end of it, in parentheses, the name of the
+ original author or publisher of that section if known, or else a
+ unique number. Make the same adjustment to the section titles in
+ the list of Invariant Sections in the license notice of the
+ combined work.
+
+ In the combination, you must combine any sections Entitled
+ "History" in the various original documents, forming one section
+ Entitled "History"; likewise combine any sections Entitled
+ "Acknowledgements", and any sections Entitled "Dedications". You
+ must delete all sections Entitled "Endorsements."
+
+ 6. COLLECTIONS OF DOCUMENTS
+
+ You may make a collection consisting of the Document and other
+ documents released under this License, and replace the individual
+ copies of this License in the various documents with a single copy
+ that is included in the collection, provided that you follow the
+ rules of this License for verbatim copying of each of the
+ documents in all other respects.
+
+ You may extract a single document from such a collection, and
+ distribute it individually under this License, provided you insert
+ a copy of this License into the extracted document, and follow
+ this License in all other respects regarding verbatim copying of
+ that document.
+
+ 7. AGGREGATION WITH INDEPENDENT WORKS
+
+ A compilation of the Document or its derivatives with other
+ separate and independent documents or works, in or on a volume of
+ a storage or distribution medium, is called an "aggregate" if the
+ copyright resulting from the compilation is not used to limit the
+ legal rights of the compilation's users beyond what the individual
+ works permit. When the Document is included in an aggregate, this
+ License does not apply to the other works in the aggregate which
+ are not themselves derivative works of the Document.
+
+ If the Cover Text requirement of section 3 is applicable to these
+ copies of the Document, then if the Document is less than one half
+ of the entire aggregate, the Document's Cover Texts may be placed
+ on covers that bracket the Document within the aggregate, or the
+ electronic equivalent of covers if the Document is in electronic
+ form. Otherwise they must appear on printed covers that bracket
+ the whole aggregate.
+
+ 8. TRANSLATION
+
+ Translation is considered a kind of modification, so you may
+ distribute translations of the Document under the terms of section
+ 4. Replacing Invariant Sections with translations requires special
+ permission from their copyright holders, but you may include
+ translations of some or all Invariant Sections in addition to the
+ original versions of these Invariant Sections. You may include a
+ translation of this License, and all the license notices in the
+ Document, and any Warranty Disclaimers, provided that you also
+ include the original English version of this License and the
+ original versions of those notices and disclaimers. In case of a
+ disagreement between the translation and the original version of
+ this License or a notice or disclaimer, the original version will
+ prevail.
+
+ If a section in the Document is Entitled "Acknowledgements",
+ "Dedications", or "History", the requirement (section 4) to
+ Preserve its Title (section 1) will typically require changing the
+ actual title.
+
+ 9. TERMINATION
+
+ You may not copy, modify, sublicense, or distribute the Document
+ except as expressly provided 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, Up: Indexes
-Index of Shell Builtin Commands
-*******************************
+D.1 Index of Shell Builtin Commands
+===================================
+\0\b[index\0\b]
* Menu:
* .: Bourne Shell Builtins.
+ (line 17)
* :: Bourne Shell Builtins.
+ (line 11)
* [: Bourne Shell Builtins.
-* alias: Bash Builtins.
+ (line 258)
+* 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 31)
+* builtin: Bash Builtins. (line 102)
+* caller: Bash Builtins. (line 111)
* cd: Bourne Shell Builtins.
-* command: Bash Builtins.
+ (line 39)
+* command: Bash Builtins. (line 129)
* compgen: Programmable Completion Builtins.
+ (line 12)
* complete: Programmable Completion Builtins.
+ (line 30)
+* compopt: Programmable Completion Builtins.
+ (line 228)
* continue: Bourne Shell Builtins.
-* declare: Bash Builtins.
+ (line 80)
+* declare: Bash Builtins. (line 149)
* dirs: Directory Stack Builtins.
+ (line 7)
* disown: Job Control Builtins.
-* echo: Bash Builtins.
-* enable: Bash Builtins.
+ (line 89)
+* echo: Bash Builtins. (line 245)
+* enable: Bash Builtins. (line 307)
* eval: Bourne Shell Builtins.
+ (line 89)
* exec: Bourne Shell Builtins.
+ (line 97)
* exit: Bourne Shell Builtins.
+ (line 114)
* export: Bourne Shell Builtins.
+ (line 121)
* fc: Bash History Builtins.
+ (line 10)
* fg: Job Control Builtins.
+ (line 17)
* getopts: Bourne Shell Builtins.
+ (line 137)
* hash: Bourne Shell Builtins.
-* help: Bash Builtins.
+ (line 180)
+* help: Bash Builtins. (line 336)
* history: Bash History Builtins.
+ (line 40)
* jobs: Job Control Builtins.
+ (line 27)
* kill: Job Control Builtins.
-* let: Bash Builtins.
-* local: Bash Builtins.
-* logout: Bash Builtins.
+ (line 59)
+* let: Bash Builtins. (line 357)
+* local: Bash Builtins. (line 365)
+* logout: Bash Builtins. (line 376)
+* mapfile: Bash Builtins. (line 381)
* popd: Directory Stack Builtins.
-* printf: Bash Builtins.
+ (line 39)
+* printf: Bash Builtins. (line 429)
* pushd: Directory Stack Builtins.
+ (line 61)
* pwd: Bourne Shell Builtins.
-* read: Bash Builtins.
+ (line 200)
+* read: Bash Builtins. (line 477)
+* readarray: Bash Builtins. (line 564)
* readonly: Bourne Shell Builtins.
+ (line 210)
* return: Bourne Shell Builtins.
-* set: The Set Builtin.
+ (line 229)
+* set: The Set Builtin. (line 11)
* shift: Bourne Shell Builtins.
-* shopt: Bash Builtins.
-* source: Bash Builtins.
+ (line 245)
+* shopt: The Shopt Builtin. (line 9)
+* source: Bash Builtins. (line 573)
* suspend: Job Control Builtins.
+ (line 101)
* test: Bourne Shell Builtins.
+ (line 258)
* times: Bourne Shell Builtins.
+ (line 334)
* trap: Bourne Shell Builtins.
-* type: Bash Builtins.
-* typeset: Bash Builtins.
-* ulimit: Bash Builtins.
+ (line 340)
+* type: Bash Builtins. (line 578)
+* typeset: Bash Builtins. (line 610)
+* ulimit: Bash Builtins. (line 616)
* umask: Bourne Shell Builtins.
-* unalias: Bash Builtins.
+ (line 389)
+* unalias: Bash Builtins. (line 707)
* unset: Bourne Shell Builtins.
+ (line 407)
* wait: Job Control Builtins.
+ (line 76)
\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
-Index of Shell Reserved Words
-*****************************
+D.2 Index of Shell Reserved Words
+=================================
+\0\b[index\0\b]
* Menu:
-* !: Pipelines.
+* !: Pipelines. (line 9)
* [[: Conditional Constructs.
+ (line 119)
* ]]: Conditional Constructs.
+ (line 119)
* 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 32)
+* function: Shell Functions. (line 13)
* if: Conditional Constructs.
+ (line 7)
* in: Conditional Constructs.
+ (line 28)
* select: Conditional Constructs.
+ (line 78)
* 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 22)
+* {: 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 50)
+* #: Special Parameters. (line 33)
+* $: Special Parameters. (line 45)
+* $!: Special Parameters. (line 51)
+* $#: Special Parameters. (line 34)
+* $$: Special Parameters. (line 46)
+* $*: Special Parameters. (line 10)
+* $-: Special Parameters. (line 41)
+* $0: Special Parameters. (line 56)
+* $?: Special Parameters. (line 37)
+* $@: Special Parameters. (line 23)
+* $_: Special Parameters. (line 65)
+* *: Special Parameters. (line 9)
+* -: Special Parameters. (line 40)
+* 0: Special Parameters. (line 55)
+* ?: Special Parameters. (line 36)
+* @: Special Parameters. (line 22)
+* _: Special Parameters. (line 64)
* 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_COMPAT: Bash Variables. (line 69)
+* BASH_ENV: Bash Variables. (line 84)
+* BASH_EXECUTION_STRING: Bash Variables. (line 90)
+* BASH_LINENO: Bash Variables. (line 93)
+* BASH_REMATCH: Bash Variables. (line 101)
+* BASH_SOURCE: Bash Variables. (line 109)
+* BASH_SUBSHELL: Bash Variables. (line 116)
+* BASH_VERSINFO: Bash Variables. (line 121)
+* BASH_VERSION: Bash Variables. (line 144)
+* BASH_XTRACEFD: Bash Variables. (line 147)
+* 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.
-* COLUMNS: Bash Variables.
+ (line 9)
+* CHILD_MAX: Bash Variables. (line 158)
+* colored-stats: Readline Init File Syntax.
+ (line 50)
+* COLUMNS: Bash Variables. (line 165)
* comment-begin: Readline Init File Syntax.
-* COMP_CWORD: Bash Variables.
-* COMP_LINE: Bash Variables.
-* COMP_POINT: Bash Variables.
-* COMP_WORDS: Bash Variables.
+ (line 56)
+* COMP_CWORD: Bash Variables. (line 171)
+* COMP_KEY: Bash Variables. (line 200)
+* COMP_LINE: Bash Variables. (line 177)
+* COMP_POINT: Bash Variables. (line 182)
+* COMP_TYPE: Bash Variables. (line 190)
+* COMP_WORDBREAKS: Bash Variables. (line 204)
+* COMP_WORDS: Bash Variables. (line 210)
+* completion-display-width: Readline Init File Syntax.
+ (line 61)
+* completion-ignore-case: Readline Init File Syntax.
+ (line 68)
+* completion-map-case: Readline Init File Syntax.
+ (line 73)
+* completion-prefix-display-length: Readline Init File Syntax.
+ (line 79)
* completion-query-items: Readline Init File Syntax.
-* COMPREPLY: Bash Variables.
+ (line 86)
+* COMPREPLY: Bash Variables. (line 218)
* convert-meta: Readline Init File Syntax.
-* DIRSTACK: Bash Variables.
+ (line 96)
+* COPROC: Bash Variables. (line 224)
+* DIRSTACK: Bash Variables. (line 228)
* disable-completion: Readline Init File Syntax.
+ (line 102)
* editing-mode: Readline Init File Syntax.
+ (line 107)
+* EMACS: Bash Variables. (line 238)
* enable-keypad: Readline Init File Syntax.
-* EUID: Bash Variables.
+ (line 118)
+* ENV: Bash Variables. (line 243)
+* EUID: Bash Variables. (line 247)
* expand-tilde: Readline Init File Syntax.
-* FCEDIT: Bash Variables.
-* FIGNORE: Bash Variables.
-* FUNCNAME: 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 129)
+* FCEDIT: Bash Variables. (line 251)
+* FIGNORE: Bash Variables. (line 255)
+* FUNCNAME: Bash Variables. (line 261)
+* FUNCNEST: Bash Variables. (line 279)
+* GLOBIGNORE: Bash Variables. (line 284)
+* GROUPS: Bash Variables. (line 290)
+* histchars: Bash Variables. (line 296)
+* HISTCMD: Bash Variables. (line 311)
+* HISTCONTROL: Bash Variables. (line 316)
+* HISTFILE: Bash Variables. (line 332)
+* HISTFILESIZE: Bash Variables. (line 336)
+* HISTIGNORE: Bash Variables. (line 347)
+* history-preserve-point: Readline Init File Syntax.
+ (line 133)
+* history-size: Readline Init File Syntax.
+ (line 139)
+* HISTSIZE: Bash Variables. (line 366)
+* HISTTIMEFORMAT: Bash Variables. (line 373)
* HOME: Bourne Shell Variables.
+ (line 13)
* horizontal-scroll-mode: Readline Init File Syntax.
-* HOSTFILE: Bash Variables.
-* HOSTNAME: Bash Variables.
-* HOSTTYPE: Bash Variables.
+ (line 146)
+* HOSTFILE: Bash Variables. (line 382)
+* HOSTNAME: Bash Variables. (line 393)
+* HOSTTYPE: Bash Variables. (line 396)
* IFS: Bourne Shell Variables.
-* IGNOREEOF: Bash Variables.
+ (line 18)
+* IGNOREEOF: Bash Variables. (line 399)
* input-meta: Readline Init File Syntax.
-* INPUTRC: Bash Variables.
+ (line 153)
+* INPUTRC: Bash Variables. (line 409)
* isearch-terminators: Readline Init File Syntax.
+ (line 160)
* keymap: Readline Init File Syntax.
-* LANG: Bash Variables.
-* LC_ALL: Bash Variables.
-* LC_COLLATE: Bash Variables.
-* LC_CTYPE: Bash Variables.
-* LC_MESSAGES: Bash Variables.
-* LC_NUMERIC: Bash Variables.
-* LINENO: Bash Variables.
-* LINES: Bash Variables.
-* MACHTYPE: Bash Variables.
+ (line 167)
+* LANG: Bash Variables. (line 413)
+* LC_ALL: Bash Variables. (line 417)
+* LC_COLLATE: Bash Variables. (line 421)
+* LC_CTYPE: Bash Variables. (line 428)
+* LC_MESSAGES <1>: Locale Translation. (line 11)
+* LC_MESSAGES: Bash Variables. (line 433)
+* LC_NUMERIC: Bash Variables. (line 437)
+* LINENO: Bash Variables. (line 441)
+* LINES: Bash Variables. (line 445)
+* MACHTYPE: Bash Variables. (line 451)
* MAIL: Bourne Shell Variables.
-* MAILCHECK: Bash Variables.
+ (line 22)
+* MAILCHECK: Bash Variables. (line 455)
* MAILPATH: Bourne Shell Variables.
+ (line 27)
+* MAPFILE: Bash Variables. (line 463)
* mark-modified-lines: Readline Init File Syntax.
+ (line 196)
+* mark-symlinked-directories: Readline Init File Syntax.
+ (line 201)
+* match-hidden-files: Readline Init File Syntax.
+ (line 206)
+* menu-complete-display-prefix: Readline Init File Syntax.
+ (line 213)
* meta-flag: Readline Init File Syntax.
-* OLDPWD: Bash Variables.
+ (line 153)
+* OLDPWD: Bash Variables. (line 467)
* OPTARG: Bourne Shell Variables.
-* OPTERR: Bash Variables.
+ (line 34)
+* OPTERR: Bash Variables. (line 470)
* OPTIND: Bourne Shell Variables.
-* OSTYPE: Bash Variables.
+ (line 38)
+* OSTYPE: Bash Variables. (line 474)
* output-meta: Readline Init File Syntax.
+ (line 218)
+* page-completions: Readline Init File Syntax.
+ (line 223)
* PATH: Bourne Shell Variables.
-* PIPESTATUS: Bash Variables.
-* PPID: Bash Variables.
-* PROMPT_COMMAND: Bash Variables.
+ (line 42)
+* PIPESTATUS: Bash Variables. (line 477)
+* POSIXLY_CORRECT: Bash Variables. (line 482)
+* PPID: Bash Variables. (line 491)
+* PROMPT_COMMAND: Bash Variables. (line 495)
+* PROMPT_DIRTRIM: Bash Variables. (line 499)
* 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 505)
+* PS4: Bash Variables. (line 510)
+* PWD: Bash Variables. (line 516)
+* RANDOM: Bash Variables. (line 519)
+* READLINE_LINE: Bash Variables. (line 524)
+* READLINE_POINT: Bash Variables. (line 528)
+* REPLY: Bash Variables. (line 532)
+* revert-all-at-newline: Readline Init File Syntax.
+ (line 233)
+* SECONDS: Bash Variables. (line 535)
+* SHELL: Bash Variables. (line 541)
+* SHELLOPTS: Bash Variables. (line 546)
+* SHLVL: Bash Variables. (line 555)
* show-all-if-ambiguous: Readline Init File Syntax.
-* TIMEFORMAT: Bash Variables.
-* TMOUT: Bash Variables.
-* UID: Bash Variables.
+ (line 239)
+* show-all-if-unmodified: Readline Init File Syntax.
+ (line 245)
+* show-mode-in-prompt: Readline Init File Syntax.
+ (line 254)
+* skip-completed-text: Readline Init File Syntax.
+ (line 259)
+* TEXTDOMAIN: Locale Translation. (line 11)
+* TEXTDOMAINDIR: Locale Translation. (line 11)
+* TIMEFORMAT: Bash Variables. (line 560)
+* TMOUT: Bash Variables. (line 598)
+* TMPDIR: Bash Variables. (line 610)
+* UID: Bash Variables. (line 614)
* visible-stats: Readline Init File Syntax.
+ (line 272)
\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 or 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 17)
+* 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 52)
* character-search (C-]): Miscellaneous Commands.
+ (line 41)
* character-search-backward (M-C-]): Miscellaneous Commands.
-* clear-screen (C-l): Commands For Moving.
+ (line 46)
+* clear-screen (C-l): Commands For Moving. (line 34)
* 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.
+ (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 12)
* delete-char-or-list (): Commands For Completion.
-* delete-horizontal-space (): Commands For Killing.
-* digit-argument (M-0, M-1, ... M--): Numeric Arguments.
+ (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 48)
* 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-file (usually C-d): Commands For Text. (line 6)
+* 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-backward-delete-char (): Commands For Text.
-* 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 21)
+* 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 52)
+* history-search-forward (): Commands For History. (line 46)
+* history-substr-search-backward (): Commands For History. (line 64)
+* history-substr-search-forward (): Commands For History. (line 58)
* 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 56)
* possible-completions (M-?): Commands For Completion.
+ (line 15)
* prefix-meta (<ESC>): Miscellaneous Commands.
-* previous-history (C-p): Commands For History.
-* quoted-insert (C-q or C-v): Commands For Text.
+ (line 18)
+* previous-history (C-p): Commands For History. (line 13)
+* print-last-kbd-macro (): Keyboard Macros. (line 17)
+* quoted-insert (C-q or C-v): Commands For Text. (line 26)
* 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 30)
* set-mark (C-@): Miscellaneous Commands.
-* start-kbd-macro (C-x (): Keyboard Macros.
-* transpose-chars (C-t): Commands For Text.
-* transpose-words (M-t): Commands For Text.
+ (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 33)
+* transpose-words (M-t): Commands For Text. (line 39)
* undo (C-_ or 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-. or M-_): Commands For History.
-* yank-nth-arg (M-C-y): Commands For History.
-* yank-pop (M-y): Commands For Killing.
+ (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 44)
+* yank (C-y): Commands For Killing. (line 68)
+* yank-last-arg (M-. or M-_): Commands For History. (line 79)
+* yank-nth-arg (M-C-y): Commands For History. (line 70)
+* yank-pop (M-y): Commands For Killing. (line 71)
\1f
-File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Top
+File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Indexes
-Concept Index
-*************
+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.
+ (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.
-* configuration: Basic Installation.
-* control operator: Definitions.
-* directory stack: The Directory Stack.
+ (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>: Definitions.
-* exit status: Exit Status.
-* 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: Programmable Completion Builtins.
-* identifier: Definitions.
-* initialization file, readline: Readline Init File.
-* installation: Basic Installation.
+ (line 6)
+* History, how to use: A Programmable Completion Example.
+ (line 114)
+* identifier: Definitions. (line 51)
+* initialization file, readline: Readline Init File. (line 6)
+* installation: Basic Installation. (line 6)
* interaction, readline: Readline Interaction.
-* interactive shell <1>: Interactive Shells.
-* 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 125)
+* 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 122)
+* 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.
+ (line 6)
* programmable completion: Programmable Completion.
-* prompting: Printing a Prompt.
-* quoting: Quoting.
-* quoting, ANSI: ANSI-C Quoting.
+ (line 6)
+* prompting: Controlling the Prompt.
+ (line 6)
+* quoting: Quoting. (line 6)
+* quoting, ANSI: ANSI-C Quoting. (line 6)
* Readline, how to use: Job Control Variables.
-* redirection: Redirections.
-* reserved word: Definitions.
+ (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.
-* shell, interactive: Interactive Shells.
-* signal: Definitions.
-* signal handling: Signals.
-* special builtin <1>: Definitions.
-* special builtin: Special Builtins.
-* startup files: Bash Startup Files.
-* suspending jobs: Job Control Basics.
-* tilde expansion: Tilde Expansion.
-* token: Definitions.
-* variable, shell: Shell Parameters.
+ (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.
-* word: Definitions.
-* word splitting: Word Splitting.
+ (line 37)
+* word: Definitions. (line 90)
+* word splitting: Word Splitting. (line 6)
* yanking text: Readline Killing Commands.
+ (line 6)
\1f
Tag Table:
-Node: Top\7f1157
-Node: Introduction\7f3286
-Node: What is Bash?\7f3511
-Node: What is a shell?\7f4612
-Node: Definitions\7f6846
-Node: Basic Shell Features\7f9512
-Node: Shell Syntax\7f10736
-Node: Shell Operation\7f11760
-Node: Quoting\7f13045
-Node: Escape Character\7f14304
-Node: Single Quotes\7f14776
-Node: Double Quotes\7f15111
-Node: ANSI-C Quoting\7f16012
-Node: Locale Translation\7f16915
-Node: Comments\7f17690
-Node: Shell Commands\7f18295
-Node: Simple Commands\7f19176
-Node: Pipelines\7f19797
-Node: Lists\7f21322
-Node: Looping Constructs\7f22835
-Node: Conditional Constructs\7f25279
-Node: Command Grouping\7f31220
-Node: Shell Functions\7f32597
-Node: Shell Parameters\7f35134
-Node: Positional Parameters\7f36459
-Node: Special Parameters\7f37350
-Node: Shell Expansions\7f40008
-Node: Brace Expansion\7f41928
-Node: Tilde Expansion\7f43597
-Node: Shell Parameter Expansion\7f45928
-Node: Command Substitution\7f52728
-Node: Arithmetic Expansion\7f54050
-Node: Process Substitution\7f54894
-Node: Word Splitting\7f55931
-Node: Filename Expansion\7f57383
-Node: Pattern Matching\7f59341
-Node: Quote Removal\7f62472
-Node: Redirections\7f62758
-Node: Executing Commands\7f69629
-Node: Simple Command Expansion\7f70296
-Node: Command Search and Execution\7f72217
-Node: Command Execution Environment\7f74214
-Node: Environment\7f76667
-Node: Exit Status\7f78318
-Node: Signals\7f79513
-Node: Shell Scripts\7f81405
-Node: Shell Builtin Commands\7f83788
-Node: Bourne Shell Builtins\7f85218
-Node: Bash Builtins\7f100145
-Node: The Set Builtin\7f124177
-Node: Special Builtins\7f131034
-Node: Shell Variables\7f132006
-Node: Bourne Shell Variables\7f132442
-Node: Bash Variables\7f134221
-Node: Bash Features\7f149565
-Node: Invoking Bash\7f150447
-Node: Bash Startup Files\7f155232
-Node: Interactive Shells\7f160102
-Node: What is an Interactive Shell?\7f160504
-Node: Is this Shell Interactive?\7f161139
-Node: Interactive Shell Behavior\7f161945
-Node: Bash Conditional Expressions\7f165212
-Node: Shell Arithmetic\7f168506
-Node: Aliases\7f170937
-Node: Arrays\7f173440
-Node: The Directory Stack\7f176460
-Node: Directory Stack Builtins\7f177166
-Node: Printing a Prompt\7f180044
-Node: The Restricted Shell\7f182414
-Node: Bash POSIX Mode\7f183892
-Node: Job Control\7f189520
-Node: Job Control Basics\7f189986
-Node: Job Control Builtins\7f194200
-Node: Job Control Variables\7f198495
-Node: Command Line Editing\7f199644
-Node: Introduction and Notation\7f200642
-Node: Readline Interaction\7f202259
-Node: Readline Bare Essentials\7f203445
-Node: Readline Movement Commands\7f205225
-Node: Readline Killing Commands\7f206181
-Node: Readline Arguments\7f208090
-Node: Searching\7f209125
-Node: Readline Init File\7f211115
-Node: Readline Init File Syntax\7f212169
-Node: Conditional Init Constructs\7f222372
-Node: Sample Init File\7f224896
-Node: Bindable Readline Commands\7f228065
-Node: Commands For Moving\7f229264
-Node: Commands For History\7f230112
-Node: Commands For Text\7f233000
-Node: Commands For Killing\7f234933
-Node: Numeric Arguments\7f236883
-Node: Commands For Completion\7f238010
-Node: Keyboard Macros\7f241590
-Node: Miscellaneous Commands\7f242148
-Node: Readline vi Mode\7f246510
-Node: Programmable Completion\7f247419
-Node: Programmable Completion Builtins\7f252467
-Node: Using History Interactively\7f259374
-Node: Bash History Facilities\7f260053
-Node: Bash History Builtins\7f262613
-Node: History Interaction\7f266179
-Node: Event Designators\7f268730
-Node: Word Designators\7f269657
-Node: Modifiers\7f271286
-Node: Installing Bash\7f272603
-Node: Basic Installation\7f273745
-Node: Compilers and Options\7f276863
-Node: Compiling For Multiple Architectures\7f277597
-Node: Installation Names\7f279254
-Node: Specifying the System Type\7f279977
-Node: Sharing Defaults\7f280684
-Node: Operation Controls\7f281349
-Node: Optional Features\7f282300
-Node: Reporting Bugs\7f289705
-Node: Major Differences From The Bourne Shell\7f290802
-Node: Builtin Index\7f304814
-Node: Reserved Word Index\7f308405
-Node: Variable Index\7f309881
-Node: Function Index\7f315667
-Node: Concept Index\7f320157
+Node: Top\7f930
+Node: Introduction\7f2848
+Node: What is Bash?\7f3076
+Node: What is a shell?\7f4189
+Node: Definitions\7f6728
+Node: Basic Shell Features\7f9646
+Node: Shell Syntax\7f10865
+Node: Shell Operation\7f11895
+Node: Quoting\7f13189
+Node: Escape Character\7f14492
+Node: Single Quotes\7f14977
+Node: Double Quotes\7f15325
+Node: ANSI-C Quoting\7f16450
+Node: Locale Translation\7f17694
+Node: Comments\7f18590
+Node: Shell Commands\7f19208
+Node: Simple Commands\7f20080
+Node: Pipelines\7f20711
+Node: Lists\7f23449
+Node: Compound Commands\7f25178
+Node: Looping Constructs\7f26184
+Node: Conditional Constructs\7f28647
+Node: Command Grouping\7f39577
+Node: Coprocesses\7f41056
+Node: GNU Parallel\7f42889
+Node: Shell Functions\7f46875
+Node: Shell Parameters\7f51959
+Node: Positional Parameters\7f56088
+Node: Special Parameters\7f56988
+Node: Shell Expansions\7f60327
+Node: Brace Expansion\7f62270
+Node: Tilde Expansion\7f65051
+Node: Shell Parameter Expansion\7f67400
+Node: Command Substitution\7f79694
+Node: Arithmetic Expansion\7f81027
+Node: Process Substitution\7f81959
+Node: Word Splitting\7f83009
+Node: Filename Expansion\7f84657
+Node: Pattern Matching\7f86822
+Node: Quote Removal\7f90522
+Node: Redirections\7f90817
+Node: Executing Commands\7f99981
+Node: Simple Command Expansion\7f100651
+Node: Command Search and Execution\7f102581
+Node: Command Execution Environment\7f104918
+Node: Environment\7f107904
+Node: Exit Status\7f109563
+Node: Signals\7f111185
+Node: Shell Scripts\7f113153
+Node: Shell Builtin Commands\7f115671
+Node: Bourne Shell Builtins\7f117699
+Node: Bash Builtins\7f137606
+Node: Modifying Shell Behavior\7f165232
+Node: The Set Builtin\7f165577
+Node: The Shopt Builtin\7f175903
+Node: Special Builtins\7f190324
+Node: Shell Variables\7f191303
+Node: Bourne Shell Variables\7f191743
+Node: Bash Variables\7f193774
+Node: Bash Features\7f220649
+Node: Invoking Bash\7f221548
+Node: Bash Startup Files\7f227326
+Node: Interactive Shells\7f232355
+Node: What is an Interactive Shell?\7f232765
+Node: Is this Shell Interactive?\7f233414
+Node: Interactive Shell Behavior\7f234229
+Node: Bash Conditional Expressions\7f237517
+Node: Shell Arithmetic\7f241519
+Node: Aliases\7f244295
+Node: Arrays\7f246851
+Node: The Directory Stack\7f251832
+Node: Directory Stack Builtins\7f252551
+Node: Controlling the Prompt\7f255507
+Node: The Restricted Shell\7f258279
+Node: Bash POSIX Mode\7f260116
+Node: Job Control\7f269502
+Node: Job Control Basics\7f269962
+Node: Job Control Builtins\7f274681
+Node: Job Control Variables\7f279152
+Node: Command Line Editing\7f280310
+Node: Introduction and Notation\7f281982
+Node: Readline Interaction\7f283604
+Node: Readline Bare Essentials\7f284795
+Node: Readline Movement Commands\7f286584
+Node: Readline Killing Commands\7f287549
+Node: Readline Arguments\7f289469
+Node: Searching\7f290513
+Node: Readline Init File\7f292699
+Node: Readline Init File Syntax\7f293846
+Node: Conditional Init Constructs\7f310832
+Node: Sample Init File\7f313365
+Node: Bindable Readline Commands\7f316483
+Node: Commands For Moving\7f317690
+Node: Commands For History\7f318834
+Node: Commands For Text\7f323019
+Node: Commands For Killing\7f325948
+Node: Numeric Arguments\7f328405
+Node: Commands For Completion\7f329544
+Node: Keyboard Macros\7f333736
+Node: Miscellaneous Commands\7f334424
+Node: Readline vi Mode\7f340230
+Node: Programmable Completion\7f341137
+Node: Programmable Completion Builtins\7f348413
+Node: A Programmable Completion Example\7f358159
+Node: Using History Interactively\7f363409
+Node: Bash History Facilities\7f364093
+Node: Bash History Builtins\7f367092
+Node: History Interaction\7f371020
+Node: Event Designators\7f373725
+Node: Word Designators\7f374947
+Node: Modifiers\7f376586
+Node: Installing Bash\7f377990
+Node: Basic Installation\7f379127
+Node: Compilers and Options\7f381819
+Node: Compiling For Multiple Architectures\7f382560
+Node: Installation Names\7f384224
+Node: Specifying the System Type\7f385042
+Node: Sharing Defaults\7f385758
+Node: Operation Controls\7f386431
+Node: Optional Features\7f387389
+Node: Reporting Bugs\7f397453
+Node: Major Differences From The Bourne Shell\7f398651
+Node: GNU Free Documentation License\7f415510
+Node: Indexes\7f440706
+Node: Builtin Index\7f441160
+Node: Reserved Word Index\7f447987
+Node: Variable Index\7f450435
+Node: Function Index\7f464615
+Node: Concept Index\7f471916
\1f
End Tag Table
projects / platform / upstream / bash.git / blobdiff