-This is bash.info, produced by makeinfo version 4.5 from
-/usr/homes/chet/src/bash/src/doc/bashref.texi.
+This is bash.info, produced by makeinfo version 4.8 from
+/Users/chet/src/bash/src/doc/bashref.texi.
-This text is a brief description of the features that are present in
-the Bash shell (version 3.0-alpha, 29 May 2003).
+ This text is a brief description of the features that are present in
+the Bash shell (version 3.2, 14 December 2007).
- This is Edition 3.0, last updated 29 May 2003, of `The GNU Bash
-Reference Manual', for `Bash', Version 3.0-alpha.
+ This is Edition 3.2, last updated 14 December 2007, of `The GNU Bash
+Reference Manual', for `Bash', Version 3.2.
- Copyright (C) 1988-2003 Free Software Foundation, Inc.
+ Copyright (C) 1988-2007 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
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
- Version 1.1 or any later version published by the Free Software
+ Version 1.2 or any later version published by the Free Software
Foundation; with no Invariant Sections, with the Front-Cover texts
- being "A GNU Manual," and with the Back-Cover Texts as in (a)
+ being "A GNU Manual", and with the Back-Cover Texts as in (a)
below. A copy of the license is included in the section entitled
- "GNU Free Documentation License."
+ "GNU Free Documentation License".
+
+ (a) The FSF's Back-Cover Text is: "You are free to copy and modify
+ this GNU Manual. Buying copies from GNU Press supports the FSF in
+ developing GNU and promoting software freedom."
- (a) The FSF's Back-Cover Text is: "You have freedom to copy and
- modify this GNU Manual, like GNU software. Copies published by
- the Free Software Foundation raise funds for GNU development."
-
INFO-DIR-SECTION Basics
START-INFO-DIR-ENTRY
* Bash: (bash). The GNU Bourne-Again SHell.
Bash Features
*************
- This text is a brief description of the features that are present in
-the Bash shell (version 3.0-alpha, 29 May 2003)..
+This text is a brief description of the features that are present in
+the Bash shell (version 3.2, 14 December 2007).
- This is Edition 3.0, last updated 29 May 2003, of `The GNU Bash
-Reference Manual', for `Bash', Version 3.0-alpha.
+ This is Edition 3.2, last updated 14 December 2007, of `The GNU Bash
+Reference Manual', for `Bash', Version 3.2.
Bash contains features that appear in other popular shells, and some
features that only appear in Bash. Some of the shells that Bash has
* Menu:
* Introduction:: An introduction to the shell.
-
* Definitions:: Some definitions used in the rest of this
manual.
-
* Basic Shell Features:: The shell "building blocks".
-
* 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.
-
-* Copying This Manual:: Copying this manual.
-
-* 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: bash.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: bash.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: bash.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
-What is a shell?
-================
+1.2 What is a shell?
+====================
+
+At its base, a shell is simply a macro processor that executes
+commands. The term macro processor means functionality where text and
+symbols are expanded to create larger expressions.
- At its base, a shell is simply a macro processor that executes
-commands. A Unix shell is both a command interpreter, which provides
-the user interface to the rich set of GNU utilities, and a programming
-language, allowing these utilitites to be combined. Files containing
+ A Unix shell is both a command interpreter and a programming
+language. As a command interpreter, the shell provides the user
+interface to the rich set of GNU utilities. The programming language
+features allow these utilities to be combined. Files containing
commands can be created, and become commands themselves. These new
commands have the same status as system commands in directories 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
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: bash.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
+ A `token' that performs a control function. It is a `newline' or
one of the following: `||', `&&', `&', `;', `;;', `|', `(', or `)'.
`exit status'
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.
\1f
File: bash.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
\1f
File: bash.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: bash.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
\1f
File: bash.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.
+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: bash.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: bash.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: bash.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
-Double Quotes
-.............
-
- Enclosing characters in double quotes (`"') preserves the literal
-value of all characters within the quotes, with the exception of `$',
-``', and `\'. The characters `$' and ``' retain their special meaning
-within double quotes (*note Shell Expansions::). The backslash retains
-its special meaning only when followed by one of the following
-characters: `$', ``', `"', `\', or `newline'. Within double quotes,
-backslashes that are followed by one of these characters are removed.
-Backslashes preceding characters without a special meaning are left
-unmodified. A double quote may be quoted within double quotes by
-preceding it with a backslash. When command history is being used, the
-double quote may not be used to quote the history expansion character.
+3.1.2.3 Double Quotes
+.....................
+
+Enclosing characters in double quotes (`"') preserves the literal value
+of all characters within the quotes, with the exception of `$', ``',
+`\', and, when history expansion is enabled, `!'. The characters `$'
+and ``' retain their special meaning within double quotes (*note Shell
+Expansions::). The backslash retains its special meaning only when
+followed by one of the following characters: `$', ``', `"', `\', or
+`newline'. Within double quotes, backslashes that are followed by one
+of these characters are removed. Backslashes preceding characters
+without a special meaning are left unmodified. A double quote may be
+quoted within double quotes by preceding it with a backslash. If
+enabled, history expansion will be performed unless an `!' appearing in
+double quotes is escaped using a backslash. The backslash preceding
+the `!' is not removed.
The special parameters `*' and `@' have special meaning when in
double quotes (*note Shell Parameter Expansion::).
\1f
File: bash.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)
\1f
File: bash.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.
\1f
File: bash.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: bash.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.
\1f
File: bash.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: bash.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 `|'.
The format for a pipeline is
[`time' [`-p']] [`!'] COMMAND1 [`|' COMMAND2 ...]
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: bash.info, Node: Lists, Next: Looping Constructs, Prev: Pipelines, Up: Shell Commands
+File: bash.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.
command executed in the list.
\1f
-File: bash.info, Node: Looping Constructs, Next: Conditional Constructs, Prev: Lists, Up: Shell Commands
+File: bash.info, Node: Compound Commands, Prev: Lists, Up: Shell Commands
-Looping Constructs
-------------------
+3.2.4 Compound Commands
+-----------------------
+
+* Menu:
- Bash supports the following looping constructs.
+* Looping Constructs:: Shell commands for iterative action.
+* Conditional Constructs:: Shell commands for conditional execution.
+* Command Grouping:: Ways to group commands.
+
+ Compound commands are the shell programming constructs. Each
+construct begins with a reserved word or control operator and is
+terminated by a corresponding reserved word or operator. Any
+redirections (*note Redirections::) associated with a compound command
+apply to all commands within that compound command unless explicitly
+overridden.
+
+ Bash provides looping constructs, conditional commands, and
+mechanisms to group commands and execute them as a unit.
+
+\1f
+File: bash.info, Node: Looping Constructs, Next: Conditional Constructs, Up: Compound Commands
+
+3.2.4.1 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.
may be used to control loop execution.
\1f
-File: bash.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Shell Commands
+File: bash.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Compound Commands
-Conditional Constructs
-----------------------
+3.2.4.2 Conditional Constructs
+..............................
`if'
The syntax of the `if' command is:
`case WORD in [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]... esac'
`case' will selectively execute the COMMAND-LIST corresponding to
- the first PATTERN that matches WORD. The `|' is used to separate
+ the first PATTERN that matches WORD. If the shell option
+ `nocasematch' (see the description of `shopt' in *Note The Shopt
+ Builtin::) is enabled, the match is performed without regard to
+ the case of alphabetic characters. The `|' is used to separate
multiple patterns, and the `)' operator terminates a pattern list.
A list of patterns and an associated command-list is known as a
CLAUSE. Each clause must be terminated with `;;'. The WORD
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
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.
`[[...]]'
When the `==' and `!=' operators are used, the string to the right
of the operator is considered a pattern and matched according to
- the rules described below in *Note Pattern Matching::. The return
- value is 0 if the string matches or does not match the pattern,
- respectively, and 1 otherwise. Any part of the pattern may be
- quoted to force it to be matched as a string.
+ the rules described below in *Note Pattern Matching::. If the
+ shell option `nocasematch' (see the description of `shopt' in
+ *Note The Shopt Builtin::) is enabled, the match is performed
+ without regard to the case of alphabetic characters. The return
+ value is 0 if the string matches (`==') or does not match
+ (`!=')the pattern, and 1 otherwise. Any part of the pattern may
+ be quoted to force it to be matched as a string.
+
+ An additional binary operator, `=~', is available, with the same
+ precedence as `==' and `!='. When it is used, the string to the
+ right of the operator is considered an extended regular expression
+ and matched accordingly (as in regex3)). The return value is 0 if
+ the string matches the pattern, and 1 otherwise. If the regular
+ expression is syntactically incorrect, the conditional
+ expression's return value is 2. If the shell option `nocasematch'
+ (see the description of `shopt' in *Note The Shopt Builtin::) is
+ enabled, the match is performed without regard to the case of
+ alphabetic characters. Any part of the pattern may be quoted to
+ force it to be matched as a string. Substrings matched by
+ parenthesized subexpressions within the regular expression are
+ saved in the array variable `BASH_REMATCH'. The element of
+ `BASH_REMATCH' with index 0 is the portion of the string matching
+ the entire regular expression. The element of `BASH_REMATCH' with
+ index N is the portion of the string matching the Nth
+ parenthesized subexpression.
Expressions may be combined using the following operators, listed
in decreasing order of precedence:
`EXPRESSION1 || EXPRESSION2'
True if either EXPRESSION1 or EXPRESSION2 is true.
-
The `&&' and `||' operators do not evaluate EXPRESSION2 if the
value of EXPRESSION1 is sufficient to determine the return value
of the entire conditional expression.
\1f
-File: bash.info, Node: Command Grouping, Prev: Conditional Constructs, Up: Shell Commands
+File: bash.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: bash.info, Node: Shell Functions, Next: Shell Parameters, Prev: Shell Commands, Up: Basic Shell Features
-Shell Functions
-===============
+3.3 Shell Functions
+===================
- Shell functions are a way to group commands for later execution
-using a single name for the group. They are executed just like a
-"regular" command. When the name of a shell function is used as a
-simple command name, the list of commands associated with that function
-name is executed. Shell functions are executed in the current shell
-context; no new process is created to interpret them.
+Shell functions are a way to group commands for later execution using a
+single name for the group. They are executed just like a "regular"
+command. When the name of a shell function is used as a simple command
+name, the list of commands associated with that function name is
+executed. Shell functions are executed in the current shell context;
+no new process is created to interpret them.
- Functions are declared using this syntax:
- [ `function' ] NAME () { COMMAND-LIST; }
+ Functions are declared using this syntax:
+ [ `function' ] NAME () COMPOUND-COMMAND [ REDIRECTIONS ]
This defines a shell function named NAME. The reserved word
`function' is optional. 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 by a semicolon, a `&', 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. 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
+positional parameters is updated to reflect the change. Special
parameter `0' is unchanged. The first element of the `FUNCNAME'
variable is set to the name of the function while the function is
executing. All other aspects of the shell execution environment are
identical between a function and its caller with the exception that the
-`DEBUG' trap below) is 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' trap). *Note Bourne Shell Builtins::,
-for the description of the `trap' builtin.
+`DEBUG' and `RETURN' traps are not inherited unless the function has
+been given the `trace' attribute using the `declare' builtin or the `-o
+functrace' option has been enabled with the `set' builtin, (in which
+case all functions inherit the `DEBUG' and `RETURN' traps). *Note
+Bourne Shell Builtins::, for the description of the `trap' builtin.
If the builtin command `return' is executed in a function, the
function completes and execution resumes with the next command after
\1f
File: bash.info, Node: Shell Parameters, Next: Shell Expansions, Prev: Shell Functions, Up: Basic Shell Features
-Shell Parameters
-================
+3.4 Shell Parameters
+====================
* Menu:
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, then VALUE is
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 `declare', `typeset', `export', `readonly', and
-`local' builtin commands.
+arguments to the `alias', `declare', `typeset', `export', `readonly',
+and `local' builtin commands.
+
+ In the context where an assignment statement is assigning a value to
+a shell variable or array index (*note Arrays::), the `+=' operator can
+be used to append to or add to the variable's previous value. When
+`+=' is applied to a variable for which the integer attribute has been
+set, VALUE is evaluated as an arithmetic expression and added to the
+variable's current value, which is also evaluated. When `+=' is
+applied to an array variable using compound assignment (*note
+Arrays::), the variable's value is not unset (as it is when using `='),
+and new values are appended to the array beginning at one greater than
+the array's maximum index. When applied to a string-valued variable,
+VALUE is expanded and appended to the variable's value.
\1f
File: bash.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: bash.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
-Special Parameters
-------------------
+3.4.2 Special Parameters
+------------------------
- The shell treats several parameters specially. These parameters may
+The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed.
`*'
Expands to the positional parameters, starting from one. When the
expansion occurs within double quotes, each parameter expands to a
separate word. That is, `"$@"' is equivalent to `"$1" "$2" ...'.
- When there are no positional parameters, `"$@"' and `$@' expand to
- nothing (i.e., they are removed).
+ If the double-quoted expansion occurs within a word, the expansion
+ of the first parameter is joined with the beginning part of the
+ original word, and the expansion of the last parameter is joined
+ with the last part of the original word. When there are no
+ positional parameters, `"$@"' and `$@' expand to nothing (i.e.,
+ they are removed).
`#'
Expands to the number of positional parameters in decimal.
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: bash.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
\1f
File: bash.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.
Patterns to be brace expanded take the form of an optional PREAMBLE,
-followed by either a series of comma-separated strings or a sequnce
+followed by either a series of comma-separated strings or a seqeunce
expression between a pair of braces, followed by an optional POSTSCRIPT.
The preamble is prefixed to each string contained within the braces, and
the postscript is then appended to each resulting string, expanding left
\1f
File: bash.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 file names with
+tildes in assignments to `PATH', `MAILPATH', and `CDPATH', and the
+shell assigns the expanded value.
The following table shows how Bash treats unquoted tilde-prefixes:
\1f
File: bash.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 `$' character introduces parameter expansion, command substitution,
+or arithmetic expansion. The parameter name or symbol to be expanded
+may be enclosed in braces, which are optional but serve to protect the
+variable to be expanded from characters immediately following it which
+could be interpreted as part of the name.
When braces are used, the matching ending brace is the first `}' not
escaped by a backslash or within a quoted string, and not within an
`${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.
`${PARAMETER:?WORD}'
If PARAMETER is null or unset, the expansion of WORD (or a message
is `@', the result is LENGTH positional parameters beginning at
OFFSET. If PARAMETER is an array name indexed by `@' or `*', the
result is the LENGTH members of the array beginning with
- `${PARAMETER[OFFSET]}'. Substring indexing is zero-based unless
- the positional parameters are used, in which case the indexing
- starts at 1.
+ `${PARAMETER[OFFSET]}'. A negative OFFSET is taken relative to
+ one greater than the maximum index of the specified array. Note
+ that a negative offset must be separated from the colon by at least
+ one space to avoid being confused with the `:-' expansion.
+ Substring indexing is zero-based unless the positional parameters
+ are used, in which case the indexing starts at 1 by default. If
+ OFFSET is 0, and the positional parameters are used, `$@' is
+ prefixed to the list.
`${!PREFIX*}'
`${!PREFIX@}'
Expands to the names of variables whose names begin with PREFIX,
separated by the first character of the `IFS' special variable.
+ When `@' is used and the expansion appears within double quotes,
+ each variable name expands to a separate word.
`${!NAME[@]}'
`${!NAME[*]}'
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
\1f
File: bash.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: bash.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:
$(( EXPRESSION ))
\1f
File: bash.info, Node: Process Substitution, Next: Word Splitting, Prev: Arithmetic Expansion, Up: Shell Expansions
-Process Substitution
---------------------
+3.5.6 Process Substitution
+--------------------------
- Process substitution is supported on systems that support named
-pipes (FIFOs) or the `/dev/fd' method of naming open files. It takes
-the form of
+Process substitution is supported on systems that support named pipes
+(FIFOs) or the `/dev/fd' method of naming open files. It takes the
+form of
<(LIST)
-
-or
+ or
>(LIST)
-
-The process LIST is run with its input or output connected to a FIFO or
-some file in `/dev/fd'. The name of this file is passed as an argument
-to the current command as the result of the expansion. If the
+ The process LIST is run with its input or output connected to a FIFO
+or some file in `/dev/fd'. The name of this file is passed as an
+argument to the current command as the result of the expansion. If the
`>(LIST)' form is used, writing to the file will provide input for
LIST. If the `<(LIST)' form is used, the file passed as an argument
should be read to obtain the output of LIST. Note that no space may
\1f
File: bash.info, Node: Word Splitting, Next: Filename Expansion, Prev: Process Substitution, Up: Shell Expansions
-Word Splitting
---------------
+3.5.7 Word Splitting
+--------------------
- The shell scans the results of parameter expansion, command
+The shell scans the results of parameter expansion, command
substitution, and arithmetic expansion that did not occur within double
quotes for word splitting.
The shell treats each character of `$IFS' as a delimiter, and splits
the results of the other expansions into words on these characters. If
`IFS' is unset, or its value is exactly `<space><tab><newline>', the
-default, then any sequence of `IFS' characters serves to delimit words.
-If `IFS' has a value other than the default, then sequences of the
-whitespace characters `space' and `tab' are ignored at the beginning
-and end of the word, as long as the whitespace character is in the
-value of `IFS' (an `IFS' whitespace character). Any character in `IFS'
-that is not `IFS' whitespace, along with any adjacent `IFS' whitespace
-characters, delimits a field. A sequence of `IFS' whitespace
-characters is also treated as a delimiter. If the value of `IFS' is
-null, no word splitting occurs.
+default, then sequences of ` <space>', `<tab>', and `<newline>' at the
+beginning and end of the results of the previous expansions are
+ignored, and any sequence of `IFS' characters not at the beginning or
+end serves to delimit words. If `IFS' has a value other than the
+default, then sequences of the whitespace characters `space' and `tab'
+are ignored at the beginning and end of the word, as long as the
+whitespace character is in the value of `IFS' (an `IFS' whitespace
+character). Any character in `IFS' that is not `IFS' whitespace, along
+with any adjacent `IFS' whitespace characters, delimits a field. A
+sequence of `IFS' whitespace characters is also treated as a delimiter.
+If the value of `IFS' is null, no word splitting occurs.
Explicit null arguments (`""' or `''') are retained. Unquoted
implicit null arguments, resulting from the expansion of parameters
\1f
File: bash.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
-Filename Expansion
-------------------
+3.5.8 Filename Expansion
+------------------------
* Menu:
names matching the pattern. If no matching file names are found, and
the shell option `nullglob' is disabled, the word is left unchanged.
If the `nullglob' option is set, and no matches are found, the word is
-removed. If the shell option `nocaseglob' is enabled, the match is
-performed without regard to the case of alphabetic characters.
+removed. If the `failglob' shell option is set, and no matches are
+found, an error message is printed and the command is not executed. If
+the shell option `nocaseglob' is enabled, the match is performed
+without regard to the case of alphabetic characters.
When a pattern is used for filename generation, the character `.' at
the start of a filename or immediately following a slash must be
matching a file name, the slash character must always be matched
explicitly. In other cases, the `.' character is not treated specially.
- See the description of `shopt' in *Note Bash Builtins::, for a
-description of the `nocaseglob', `nullglob', and `dotglob' options.
+ See the description of `shopt' in *Note The Shopt Builtin::, for a
+description of the `nocaseglob', `nullglob', `failglob', and `dotglob'
+options.
The `GLOBIGNORE' shell variable may be used to restrict the set of
filenames matching a pattern. If `GLOBIGNORE' is set, each matching
\1f
File: bash.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. 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.
+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:
`*'
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 word xdigit
-
A character class matches any character belonging to that class.
The `word' character class matches letters, digits, and the
character `_'.
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: bash.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: bash.info, Node: Redirections, Next: Executing Commands, Prev: Shell Expansions, Up: Basic Shell Features
-Redirections
-============
+3.6 Redirections
+================
- Before a command is executed, its input and output may be REDIRECTED
+Before a command is executed, its input and output may be REDIRECTED
using a special notation interpreted by the shell. Redirection may
also be used to open and close files for the current shell execution
environment. The following redirection operators may precede or appear
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 duplicated as standard output before the standard
+output was redirected to DIRLIST.
Bash handles several filenames specially when they are used in
redirections, as described in the following table:
A failure to open or create a file causes the redirection to fail.
-Redirecting Input
------------------
+ Redirections using file descriptors greater than 9 should be used
+with care, as they may conflict with file descriptors the shell uses
+internally.
+
+3.6.1 Redirecting Input
+-----------------------
- Redirection of input causes the file whose name results from the
+Redirection of input causes the file whose name results from the
expansion of WORD to be opened for reading on file descriptor `n', or
the standard input (file descriptor 0) if `n' is not specified.
The general format for redirecting input is:
[N]<WORD
-Redirecting Output
-------------------
+3.6.2 Redirecting Output
+------------------------
- Redirection of output causes the file whose name results from the
+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
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.
The general format for appending output is:
[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
+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.
There are two formats for redirecting standard output and standard
error:
&>WORD
-
-and
+ and
>&WORD
-
-Of the two forms, the first is preferred. This is semantically
+ Of the two forms, the first is preferred. This is semantically
equivalent to
>WORD 2>&1
-Here Documents
---------------
+3.6.5 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.
DELIMITER. This allows here-documents within shell scripts to be
indented in a natural fashion.
-Here Strings
-------------
+3.6.6 Here Strings
+------------------
- A variant of here documents, the format is:
+A variant of here documents, the format is:
<<< WORD
The WORD is expanded and supplied to the command on its standard
input.
-Duplicating File Descriptors
-----------------------------
+3.6.7 Duplicating File Descriptors
+----------------------------------
- The redirection operator
+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
+ is used to duplicate input file descriptors. If WORD expands to one
+or more digits, the file descriptor denoted by N is made to be a copy
+of that file descriptor. If the digits in WORD do not specify a file
descriptor open for input, a redirection error occurs. If WORD
evaluates to `-', file descriptor N is closed. If N is not specified,
the standard input (file descriptor 0) is used.
The operator
[N]>&WORD
-
-is used similarly to duplicate output file descriptors. If N is not
+ 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.
-Moving File Descriptors
------------------------
+3.6.8 Moving File Descriptors
+-----------------------------
- The redirection operator
+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.
+ 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.
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.
-moves the file descriptor DIGIT to file descriptor N, or the standard
-output (file descriptor 1) if N is not specified.
-
-Opening File Descriptors for Reading and Writing
-------------------------------------------------
+3.6.9 Opening File Descriptors for Reading and Writing
+------------------------------------------------------
- The redirection operator
+The redirection operator
[N]<>WORD
-
-causes the file whose name is the expansion of WORD to be opened for
+ 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: bash.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: bash.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: bash.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.
\1f
File: bash.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::)
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.
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'.
\1f
File: bash.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'.
\1f
File: bash.info, Node: Exit Status, Next: Signals, Prev: Environment, Up: Executing Commands
-Exit Status
------------
+3.7.5 Exit Status
+-----------------
- For the shell's purposes, a command which exits with a zero exit
-status has succeeded. A non-zero exit status indicates failure. This
+For the shell's purposes, a command which exits with a zero exit status
+has succeeded. A non-zero exit status indicates failure. This
seemingly counter-intuitive scheme is used so there is one well-defined
way to indicate success and a variety of ways to indicate various
failure modes. When a command terminates on a fatal signal whose
\1f
File: bash.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, an interactive shell resends the `SIGHUP' to all jobs, running
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: bash.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. The shell first searches
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
\1f
File: bash.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.
+For example, the `:', `true', `false', and `test' builtins do not
+accept options.
+
\1f
File: bash.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)'
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
+ dash at the beginning of the zeroth argument passed to COMMAND.
+ This is what the `login' program does. The `-c' option causes
+ COMMAND to be executed with an empty environment. If `-a' is
+ supplied, the shell passes NAME as the zeroth argument to COMMAND.
+ If no COMMAND is specified, redirections may be used to affect the
current shell environment. If there are no redirection errors, the
return status is zero; otherwise the return status is non-zero.
character found.
`hash'
- hash [-'r] [-p FILENAME] [-dt] [NAME]
+ hash [-r] [-p FILENAME] [-dt] [NAME]
Remember the full pathnames of commands specified as NAME
arguments, so they need not be searched for on subsequent
invocations. The commands are found by searching through the
`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.
Evaluate a conditional expression EXPR. Each operator and operand
must be a separate argument. Expressions are composed of the
primaries described below in *Note Bash Conditional Expressions::.
+ `test' does not accept any options, nor does it accept and ignore
+ an argument of `--' as signifying the end of options.
When the `[' form is used, the last argument to the command must
be a `]'.
Expressions may be combined using the following operators, listed
- in decreasing order of precedence.
+ in decreasing order of precedence. The evaluation depends on the
+ number of arguments; see below.
`! EXPR'
True if EXPR is false.
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
`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. The `-l' option causes the shell to
- print a list of signal names and their corresponding numbers.
-
- 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'
+ receives signal SIGSPEC. If ARG is absent (and there is a single
+ SIGSPEC) or equal to `-', each specified signal's disposition is
+ reset to the value it had when the shell was started. If ARG is
+ the null string, then the signal specified by each SIGSPEC is
+ ignored by the shell and commands it invokes. If ARG is not
+ present and `-p' has been supplied, the shell displays the trap
+ commands associated with each SIGSPEC. If no arguments are
+ supplied, or only `-p' is given, `trap' prints the list of commands
+ associated with each signal number in a form that may be reused as
+ shell input. The `-l' option causes the shell to print a list of
+ signal names and their corresponding numbers. Each SIGSPEC is
+ either a signal name or a signal number. Signal names are case
+ insensitive and the `SIG' prefix is optional. If a SIGSPEC is `0'
or `EXIT', ARG is executed when the shell exits. If a SIGSPEC is
`DEBUG', the command ARG is executed before every simple command,
`for' command, `case' command, `select' command, every arithmetic
`for' command, and before the first command executes in a shell
function. Refer to the description of the `extglob' option to the
- `shopt' builtin (*note Bash Builtins::) for details of its effect
- on the `DEBUG' trap. If a SIGSPEC is `ERR', the command ARG is
- executed whenever a simple command has a non-zero exit status.
- The `ERR' trap is not executed if the failed command is part of the
- command list immediately following an `until' or `while' keyword,
- part of the test in an `if' statement, part of a `&&' or `||'
- list, or if the command's return status is being inverted using
- `!'. If a SIGSPEC is `RETURN', the command ARG is executed each
- time a shell function or a script executed with the `.' or
+ `shopt' builtin (*note The Shopt Builtin::) for details of its
+ effect on the `DEBUG' trap. If a SIGSPEC is `ERR', the command ARG
+ is executed whenever a simple command has a non-zero exit status,
+ subject to the following conditions. The `ERR' trap is not
+ executed if the failed command is part of the command list
+ immediately following an `until' or `while' keyword, part of the
+ test in an `if' statement, part of a command executed in a `&&' or
+ `||' list, or if the command's return status is being inverted
+ using `!'. These are the same conditions obeyed by the `errexit'
+ option. If a SIGSPEC is `RETURN', the command ARG is executed
+ each time a shell function or a script executed with the `.' or
`source' builtins finishes executing.
Signals ignored upon entry to the shell cannot be trapped or reset.
- Trapped signals are reset to their original values in a child
- process when it is created.
+ Trapped signals that are not being ignored are reset to their
+ original values in a child process when it is created.
The return status is zero unless a SIGSPEC does not specify a
valid signal.
zero unless a NAME is readonly.
\1f
-File: bash.info, Node: Bash Builtins, Next: The Set Builtin, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
+File: bash.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] ...]
Display current Readline (*note Command Line Editing::) key and
function bindings, bind a key sequence to a Readline function or
macro, or set a Readline variable. Each non-option argument is a
- command as it would appear in a a Readline initialization file
+ 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
`caller'
caller [EXPR]
Returns the context of any active subroutine call (a shell
- function or a script executed with the `.' or `source' builtins.
+ 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
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. If the `extdebug' shell
- option is enabled using `shopt' (*note Bash Builtins::), the
+ option is enabled using `shopt' (*note The Shopt Builtin::), the
source file name and line number where the function is defined are
displayed as well. `-F' implies `-f'. The following options can
be used to restrict output to variables with the specified
`-t'
Give each NAME the `trace' attribute. Traced functions
- inherit the `DEBUG' trap from the calling shell. The trace
- attribute has no special meaning for variables.
+ inherit the `DEBUG' and `RETURN' traps from the calling shell.
+ The trace attribute has no special meaning for variables.
`-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. If a variable name is followed by =VALUE, the
- value of the variable is set to VALUE.
+ Using `+' instead of `-' turns off the attribute instead, with the
+ exceptions that `+a' may not be used to destroy an array variable
+ and `+r' will not remove the readonly attribute. When used in a
+ function, `declare' makes each NAME local, as with the `local'
+ command. If a variable name is followed by =VALUE, the value of
+ the variable is set to VALUE.
The return status is zero unless an invalid option is encountered,
an attempt is made to define a function using `-f foo=bar', an
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:
+ default. `echo' does not interpret `--' to mean the end of
+ options.
+
+ `echo' interprets the following escape sequences:
`\a'
alert (bell)
the eight-bit character whose value is the octal value NNN
(zero to three octal digits)
- `\NNN'
- the eight-bit character whose value is the octal value NNN
- (one to three octal digits)
-
`\xHH'
the eight-bit character whose value is the hexadecimal value
HH (one or two 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
Exit a login shell, returning a status of N to the shell's parent.
`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
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.
+ in the corresponding ARGUMENT, (except that `\c' terminates
+ output, backslashes in `\'', `\"', and `\?' are not removed, and
+ octal escapes beginning with `\0' may contain up to four digits),
+ and `%q' causes `printf' to output the corresponding ARGUMENT in a
+ format that can be reused as shell input.
+
+ The `-v' option causes the output to be assigned to the variable
+ VAR rather than being printed to the standard output.
The FORMAT is reused as necessary to consume all of the ARGUMENTS.
If the FORMAT requires more ARGUMENTS than are supplied, the extra
Read input from file descriptor FD.
-`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:
+`source'
+ source FILENAME
+ A synonym for `.' (*note Bourne Shell Builtins::).
- `-s'
- Enable (set) each OPTNAME.
+`type'
+ type [-afptP] [NAME ...]
+ For each NAME, indicate how it would be interpreted if used as a
+ command name.
- `-u'
- Disable (unset) each OPTNAME.
+ If the `-t' option is used, `type' prints a single word which is
+ one of `alias', `function', `builtin', `file' or `keyword', if
+ NAME is an alias, shell function, shell builtin, disk file, or
+ shell reserved word, respectively. If the NAME is not found, then
+ nothing is printed, and `type' returns a failure status.
- `-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.
+ If the `-p' option is used, `type' either returns the name of the
+ disk file that would be executed, or nothing if `-t' would not
+ return `file'.
- `-o'
- Restricts the values of OPTNAME to be those defined for the
- `-o' option to the `set' builtin (*note The Set Builtin::).
+ The `-P' option forces a path search for each NAME, even if `-t'
+ would not return `file'.
- If either `-s' or `-u' is used with no OPTNAME arguments, the
- display is limited to those options which are set or unset,
- respectively.
+ If a command is hashed, `-p' and `-P' print the hashed value, not
+ necessarily the file that appears first in `$PATH'.
- Unless otherwise noted, the `shopt' options are disabled (off) by
- default.
+ 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 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.
+ If the `-f' option is used, `type' does not attempt to find shell
+ functions, as with the `command' builtin.
- 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.
+ The return status is zero if any of the NAMES are found, non-zero
+ if none are found.
- `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.
+`typeset'
+ typeset [-afFrxi] [-p] [NAME[=VALUE] ...]
+ The `typeset' command is supplied for compatibility with the Korn
+ shell; however, it has been deprecated in favor of the `declare'
+ builtin command.
- `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.
+`ulimit'
+ ulimit [-acdefilmnpqrstuvxSH] [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.
- `checkwinsize'
- If set, Bash checks the window size after each command and,
- if necessary, updates the values of `LINES' and `COLUMNS'.
+ `-H'
+ Change and report the hard limit associated with a resource.
- `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.
+ `-a'
+ All current limits are reported.
- `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.
-
- `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.
-
- `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.
-
- `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.
-
- `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.
-
- `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 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.
-
-`source'
- source FILENAME
- A synonym for `.' (*note Bourne Shell Builtins::).
-
-`type'
- type [-afptP] [NAME ...]
- For each NAME, indicate how it would be interpreted if used as a
- command name.
-
- If the `-t' option is used, `type' prints a single word which is
- one of `alias', `function', `builtin', `file' or `keyword', if
- NAME is an alias, shell function, shell builtin, disk file, or
- shell reserved word, respectively. If the NAME is not found, then
- nothing is printed, and `type' returns a failure status.
-
- If the `-p' option is used, `type' either returns the name of the
- disk file that would be executed, or nothing if `-t' would not
- return `file'.
-
- 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, 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.
-
- 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 any of the NAMES are found, non-zero
- if none are found.
-
-`typeset'
- typeset [-afFrxi] [-p] [NAME[=VALUE] ...]
- The `typeset' command is supplied for compatibility with the Korn
- shell; however, it has been deprecated in favor of the `declare'
- builtin command.
-
-`ulimit'
- ulimit [-acdflmnpstuvSH] [LIMIT]
- `ulimit' provides control over the resources available to processes
- started by the shell, on systems that allow such control. If an
- option is given, it is interpreted as follows:
- `-S'
- Change and report the soft limit associated with a resource.
-
- `-H'
- Change and report the hard limit associated with a resource.
-
- `-a'
- All current limits are reported.
-
- `-c'
- The maximum size of core files created.
+ `-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.
`-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.
`-v'
The maximum amount of virtual memory available to the process.
+ `-x'
+ The maximum number of file locks.
+
If LIMIT is given, it is the new value of the specified resource;
the special LIMIT values `hard', `soft', and `unlimited' stand for
the current hard limit, the current soft limit, and no limit,
- respectively. Otherwise, the current value of the soft limit for
- the specified resource is printed, unless the `-H' option is
+ 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,
\1f
-File: bash.info, Node: The Set Builtin, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
+File: bash.info, Node: Modifying Shell Behavior, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
-The Set Builtin
-===============
+4.3 Modifying Shell Behavior
+============================
- This builtin is so complicated that it deserves its own section.
+* Menu:
+
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
+
+\1f
+File: bash.info, Node: The Set Builtin, Next: The Shopt Builtin, Up: Modifying Shell Behavior
+
+4.3.1 The Set Builtin
+---------------------
+
+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] [ARGUMENT ...]
+ set [+abefhkmnptuvxBCEHPT] [+o OPTION] [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:
Commands::) exits with a non-zero status, unless the command
that fails is part of the command list immediately following
a `while' or `until' keyword, part of the test in an `if'
- statement, part of a `&&' or `||' list, or if the command's
- return status is being inverted using `!'. A trap on `ERR',
+ statement, part of a command executed in a `&&' or `||b' list,
+ any command in a pipeline but the last, or if the command's
+ return status is being inverted using `!'. Failing simple
+ commands that are part of shell functions or command lists
+ enclosed in braces or parentheses satisfying the above
+ conditions do not cause the shell to exit. A trap on `ERR',
if set, is executed before the shell exits.
`-f'
`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'.
Print shell input lines as they are read.
`-x'
- Print a trace of simple commands, \fBfor\fP commands,
- \fBcase\fP commands, \fBselect\fP commands, and arithmetic
- \fBfor\fP 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.
+ 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
$ cd ..; pwd
/usr/local
- `-T'
- If set, any trap on `DEBUG' is inherited by shell functions,
- command substitutions, and commands executed in a subshell
- environment. The `DEBUG' trap is normally not inherited in
- such cases.
+ `-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: bash.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 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:
+ `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.
+
+ `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 `ERROR' 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
+ pathname 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.
+
+ `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.
+
+ `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 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.
- `--'
- 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
- `-'.
+ `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.
- `-'
- 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.
+ `xpg_echo'
+ If set, the `echo' builtin expands backslash-escape sequences
+ by default.
- 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 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 return status is always zero unless an invalid option is
- supplied.
\1f
-File: bash.info, Node: Special Builtins, Prev: The Set Builtin, Up: Shell Builtin Commands
+File: bash.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
\1f
File: bash.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
-Shell Variables
-***************
+5 Shell Variables
+*****************
* Menu:
\1f
File: bash.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
\1f
File: bash.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.
+`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_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'.
+ 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 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_COMMAND'
The command currently being executed or about to be executed,
An array variable whose members are the line numbers in source
files corresponding to each member of FUNCNAME.
`${BASH_LINENO[$i]}' is the line number in the source file where
- `${FUNCNAME[$i + 1]}' was called. The corresponding source file
- name is `${BASH_SOURCE[$i + 1]}'. Use `LINENO' to obtain the
- current line number.
+ `${FUNCNAME[$i]}' was called (or `${BASH_LINENO[$i-1]}' if
+ referenced within another shell function). The corresponding
+ source file name is `${BASH_SOURCE[$i]}'. Use `LINENO' to obtain
+ the current line number.
+
+`BASH_REMATCH'
+ An array variable whose members are assigned by the `=~' binary
+ operator to the `[[' conditional command (*note Conditional
+ Constructs::). The element with index 0 is the portion of the
+ string matching the entire regular expression. The element with
+ index N is the portion of the string matching the Nth
+ parenthesized subexpression. This variable is read-only.
`BASH_SOURCE'
An array variable whose members are the source filenames
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'
`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::).
+ current command line. The words are split on shell metacharacters
+ as the shell parser would separate them. This variable is
+ available only in shell functions invoked by the programmable
+ completion facilities (*note Programmable Completion::).
`COMPREPLY'
An array variable from which Bash reads the possible completions
An array variable containing the names of all shell functions
currently in the execution call stack. The element with index 0
is the name of any currently-executing shell function. The
- bottom-most element is "main". This variable exists only when a
+ bottom-most element is `"main"'. This variable exists only when a
shell function is executing. Assignments to `FUNCNAME' have no
effect and return an error status. If `FUNCNAME' is unset, it
loses its special properties, even if it is subsequently reset.
`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 necessary, by removing the oldest entries, to contain no more
+ than that number of lines. The history file is also truncated to
+ this size after writing it when an interactive shell exits. The
+ default value is 500.
`HISTIGNORE'
A colon-separated list of patterns used to decide which command
The maximum number of commands to remember on the history list.
The default value is 500.
+`HISTTIMEFORMAT'
+ If this variable is set and not null, its value is used as a
+ format string for STRFTIME to print the time stamp associated with
+ each history entry displayed by the `history' builtin. If this
+ variable is set, time stamps are written to the history file so
+ they may be preserved across shell sessions. This uses the
+ history comment character to distinguish timestamps from other
+ history lines.
+
`HOSTFILE'
Contains the name of a file in the same format as `/etc/hosts' that
should be read when the shell needs to complete a hostname. The
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'
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
if input does not arrive after `TMOUT' seconds when input is coming
from a terminal.
- In an interative shell, the value is interpreted as the number of
+ In an interactive shell, the value is interpreted as the number of
seconds to wait for input after issuing the primary prompt when
the shell is interactive. Bash terminates after that number of
seconds if input does not arrive.
+`TMPDIR'
+ If set, Bash uses its value as the name of a directory in which
+ Bash creates temporary files for the shell's use.
+
`UID'
The numeric real user id of the current user. This variable is
readonly.
\1f
File: bash.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 section describes features unique to Bash.
* Menu:
\1f
File: bash.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 ...]
`--debugger'
Arrange for the debugger profile to be executed before the shell
- starts. Turns on extended debugging mode (see *Note Bash
- Builtins:: for a description of the `extdebug' option to the
- `shopt' builtin) and shell function tracing (see *Note The Set
- Builtin:: for a description of the `-o functrace' option).
+ starts. Turns on extended debugging mode (see *Note The Shopt
+ Builtin:: for a description of the `extdebug' option to the `shopt'
+ builtin) and shell function tracing (see *Note The Set Builtin::
+ for a description of the `-o functrace' option).
`--dump-po-strings'
A list of all double-quoted strings preceded by `$' is printed on
- the standard ouput in the GNU `gettext' PO (portable object) file
+ the standard output in the GNU `gettext' PO (portable object) file
format. Equivalent to `-D' except for the output format.
`--dump-strings'
Equivalent to `-D'.
`--help'
- Display a usage message on standard output and exit sucessfully.
+ Display a usage message on standard output and exit successfully.
`--init-file FILENAME'
`--rcfile FILENAME'
`--posix'
Change the behavior of Bash where the default operation differs
- from the POSIX 1003.2 standard to match the standard. This is
- intended to make Bash behave as a strict superset of that
- standard. *Note Bash POSIX Mode::, for a description of the Bash
- POSIX mode.
+ from the POSIX standard to match the standard. This is intended
+ to make Bash behave as a strict superset of that standard. *Note
+ Bash POSIX Mode::, for a description of the Bash POSIX mode.
`--restricted'
Make the shell a restricted shell (*note The Restricted Shell::).
`-D'
A list of all double-quoted strings preceded by `$' 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 Shell Builtin Commands::). If SHOPT_OPTION is
- present, `-O' sets the value of that option; `+O' unsets it. If
+ 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
\1f
File: bash.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 file names as described above under Tilde Expansion (*note
+Tilde Expansion::).
Interactive shells are described in *Note Interactive Shells::.
Invoked as an interactive login shell, or with `--login'
........................................................
- When Bash is invoked as an interactive login shell, or as a
+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
+file name.
As noted above, if a non-interactive shell is invoked with the
`--login' option, Bash attempts to read and execute commands from the
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 a network connection, as if by the remote shell daemon,
+usually `rshd', or the secure shell daemon `sshd'. If Bash determines
+it is being run in this fashion, it reads and executes commands from
+`~/.bashrc', if that file exists and is readable. It will not do this
+if invoked as `sh'. The `--norc' option may be used to inhibit this
+behavior, and the `--rcfile' option may be used to force another file
+to be read, but `rshd' does not generally invoke the shell with those
+options or allow them to be specified.
Invoked with unequal effective and real UID/GIDs
................................................
- If Bash is started with the effective user (group) id not equal to
-the real user (group) id, and the `-p' option is not supplied, no
-startup files are read, shell functions are not inherited from the
-environment, the `SHELLOPTS' variable, if it appears in the
-environment, is ignored, and the effective user id is set to the real
-user id. If the `-p' option is supplied at invocation, the startup
-behavior is the same, but the effective user id is not reset.
+If Bash is started with the effective user (group) id not equal to the
+real user (group) id, and the `-p' option is not supplied, no startup
+files are read, shell functions are not inherited from the environment,
+the `SHELLOPTS' variable, if it appears in the environment, is ignored,
+and the effective user id is set to the real user id. If the `-p'
+option is supplied at invocation, the startup behavior is the same, but
+the effective user id is not reset.
\1f
File: bash.info, Node: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
-Interactive Shells
-==================
+6.3 Interactive Shells
+======================
* Menu:
\1f
File: bash.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: bash.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: bash.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
((*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: bash.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.
+ 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.
\1f
File: bash.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' and the `-i' option to the
-`declare' builtins.
+The shell allows arithmetic expressions to be evaluated, as one of the
+shell expansions or by the `let' and the `-i' option to the `declare'
+builtins.
Evaluation is done in fixed-width integers with no check for
overflow, though division by 0 is trapped and flagged as an error. The
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
+and uppercase letters may be used interchangeably to represent numbers
between 10 and 35.
Operators are evaluated in order of precedence. Sub-expressions in
\1f
File: bash.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 space or tab character, then the next command word following the
+alias is also checked for alias expansion.
Aliases are created and listed with the `alias' command, and removed
with the `unalias' command.
(*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: bash.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
+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
to a number greater than or equal to zero. To explicitly declare an
array, use
declare -a NAME
-
-The syntax
+ The syntax
declare -a NAME[SUBSCRIPT]
-
-is also accepted; the SUBSCRIPT is ignored. Attributes may be
+ 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.
Arrays are assigned to using compound assignments of the form
name=(value1 ... valueN)
-
-where each VALUE is of the form `[[SUBSCRIPT]=]'STRING. If the
+ 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
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 `${name['SUBSCRIPT`]}'. If SUBSCRIPT is `@' or `*', the expansion
-is the number of elements in the array. Referencing an array variable
-without a subscript is equivalent to referencing element zero.
+to nothing. If the double-quoted expansion occurs within a word, the
+expansion of the first parameter is joined with the beginning part of
+the original word, and the expansion of the last parameter is joined
+with the last part of the original word. This is analogous to the
+expansion of the special parameters `@' and `*'.
+`${#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 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[SUBSCRIPT] destroys the array element at index SUBSCRIPT. Care
+must be taken to avoid unwanted side effects caused by filename
+generation. `unset' NAME, where NAME is an array, removes the entire
+array. A subscript of `*' or `@' also removes the entire array.
The `declare', `local', and `readonly' builtins each accept a `-a'
option to specify an array. The `read' builtin accepts a `-a' option
\1f
File: bash.info, Node: The Directory Stack, Next: Printing a Prompt, Prev: Arrays, Up: Bash Features
-The Directory Stack
-===================
+6.8 The Directory Stack
+=======================
* Menu:
\1f
File: bash.info, Node: Directory Stack Builtins, Up: The Directory Stack
-Directory Stack Builtins
-------------------------
+6.8.1 Directory Stack Builtins
+------------------------------
`dirs'
dirs [+N | -N] [-clpv]
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.
\1f
File: bash.info, Node: Printing a 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.
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.
`\W'
- The basename of `$PWD'.
+ The basename of `$PWD', with `$HOME' abbreviated with a tilde.
`\!'
The history number of this command.
\1f
File: bash.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
-The Restricted Shell
-====================
+6.10 The Restricted Shell
+=========================
- If Bash is started with the name `rbash', or the `--restricted' or
-`-r' option is supplied at invocation, the shell becomes restricted. A
+If Bash is started with the name `rbash', or the `--restricted' or `-r'
+option is supplied at invocation, the shell becomes restricted. A
restricted shell is used to set up an environment more controlled than
the standard shell. A restricted shell behaves identically to `bash'
with the exception that the following are disallowed or not performed:
\1f
File: bash.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 1003.2 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 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.
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.
10. 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
+ 11. The `kill' builtin does not accept signal names with a `SIG'
+ prefix.
+
+ 12. Non-interactive shells exit if FILENAME in `.' FILENAME is not
found.
- 12. Non-interactive shells exit if a syntax error in an arithmetic
+ 13. 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
+ 14. 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
+ 15. 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
+ 16. Function names must be valid shell `name's. That is, they may not
contain characters other than letters, digits, and underscores, and
may not start with a digit. Declaring a function with an invalid
name causes a fatal syntax error in non-interactive shells.
- 16. POSIX 1003.2 `special' builtins are found before shell functions
- during command lookup.
+ 17. POSIX special builtins are found before shell functions during
+ command lookup.
- 17. If a POSIX 1003.2 special builtin returns an error status, a
+ 18. 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
22. Process substitution is not available.
- 23. Assignment statements preceding POSIX 1003.2 special builtins
- persist in the shell environment after the builtin completes.
+ 23. 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
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.
+ in the format required by POSIX.
26. The `trap' builtin displays signal names without the leading `SIG'.
- 27. The `.' and `source' builtins do not search the current directory
+ 27. The `trap' builtin doesn't check the first argument for a possible
+ signal specification and revert the signal handling to the original
+ disposition if it is, unless that argument consists solely of
+ digits and is a valid signal number. If users want to reset the
+ handler for a given signal to the original disposition, they
+ should use `-' as the first argument.
+
+ 28. 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
+ 29. Subshells spawned to execute command substitutions inherit the
value of the `-e' option from the parent shell. When not in POSIX
mode, Bash clears the `-e' option in such subshells.
- 29. Alias expansion is always enabled, even in non-interactive shells.
+ 30. Alias expansion is always enabled, even in non-interactive shells.
+
+ 31. 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
+ 32. When the `set' builtin is invoked without options, it does not
display shell function names and definitions.
- 31. When the `set' builtin is invoked without options, it displays
+ 33. When the `set' builtin is invoked without options, it displays
variable values without quotes, unless they contain shell
metacharacters, even if the result contains nonprinting characters.
- 32. When the `cd' builtin is invoked in LOGICAL mode, and the pathname
+ 34. When the `cd' builtin is invoked in LOGICAL mode, and the pathname
constructed from `$PWD' and the directory name supplied as an
argument does not refer to an existing directory, `cd' will fail
instead of falling back to PHYSICAL mode.
- There is other POSIX 1003.2 behavior that Bash does not implement.
-Specifically:
+ 35. When the `pwd' builtin is supplied the `-P' option, it resets
+ `$PWD' to a pathname containing no symlinks.
+
+ 36. The `pwd' builtin verifies that the value it prints is the same as
+ the current directory, even if it is not asked to check the file
+ system with the `-P' option.
+
+ 37. When listing the history, the `fc' builtin does not include an
+ indication of whether or not a history entry has been modified.
+
+ 38. The default editor used by `fc' is `ed'.
+
+ 39. The `type' and `command' builtins will not report a non-executable
+ file as having been found, though the shell will attempt to
+ execute such a file if it is the only so-named file found in
+ `$PATH'.
- 1. Assignment statements affect the execution environment of all
- builtins, not just special ones.
+ 40. The `vi' editing mode will invoke the `vi' editor directly when
+ the `v' command is run, instead of checking `$FCEDIT' and
+ `$EDITOR'.
- 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.
+ 41. When the `xpg_echo' option is enabled, Bash does not attempt to
+ interpret any arguments to `echo' as options. Each argument is
+ displayed, after escape characters are converted.
- 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: bash.info, Node: Job Control, Next: Using History Interactively, Prev: Bash Features, Up: Top
+File: bash.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: bash.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.
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
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
+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 `%-'. 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
`-'.
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 while jobs are stopped, the shell
-prints a message warning that there are stopped jobs. The `jobs'
+ 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: bash.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]
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 [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.
\1f
File: bash.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
\1f
-File: bash.info, Node: Command Line Editing, Next: Installing Bash, Prev: Using History Interactively, Up: Top
+File: bash.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.
\1f
File: bash.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: bash.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: bash.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: bash.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: bash.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.
\1f
File: bash.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: bash.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".
\1f
File: bash.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: bash.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.
+
`comment-begin'
The string to insert at the beginning of the line when the
`insert-comment' command is executed. The default value is
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'.
+ 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
If set to `on', tilde expansion is performed when Readline
attempts word completion. The default is `off'.
- If set to `on', the history code attempts to place point at
- the same location on each history line retrieved with
- `previous-history' or `next-history'.
+ `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'.
`horizontal-scroll-mode'
This variable can be set to either `on' or `off'. Setting it
`show-all-if-unmodified'
This alters the default behavior of the completion functions
- in a fashion similar to SHOW-ALL-IF-AMBIGUOUS. 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'.
+ 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'.
`visible-stats'
If set to `on', a character denoting a file's type is
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).
\1f
File: bash.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: bash.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
# First, include any systemwide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc
-
+
#
# Set various bindings for emacs mode.
-
+
set editing-mode emacs
-
+
$if mode=emacs
-
+
Meta-Control-h: backward-kill-word Text after the function name is ignored
-
+
#
# Arrow keys in keypad mode
#
#"\M-\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
$if Bash
# edit the path
# Edit variable on current line.
"\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
$endif
-
+
# use a visible bell if one is available
set bell-style visible
-
+
# don't strip characters to 7 bits when reading
set input-meta on
-
+
# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off
-
+
# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on
-
+
# if there are more than 150 possible completions for
# a word, ask the user if he wants to see all of them
set completion-query-items 150
-
+
# For FTP
$if Ftp
"\C-xg": "get \M-?"
\1f
File: bash.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
-Bindable Readline Commands
-==========================
+8.4 Bindable Readline Commands
+==============================
* Menu:
\1f
File: bash.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
-Commands For Moving
--------------------
+8.4.1 Commands For Moving
+-------------------------
`beginning-of-line (C-a)'
Move to the start of the current line.
\1f
File: bash.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
-Commands For Manipulating The History
--------------------------------------
+8.4.2 Commands For Manipulating The History
+-------------------------------------------
`accept-line (Newline or Return)'
Accept the line regardless of where the cursor is. If this line is
second word on the previous line) at point. With an argument N,
insert the Nth word from the previous command (the words in the
previous command begin with word 0). A negative argument inserts
- the Nth word from the end of the previous command.
+ the Nth word from the end of the previous command. Once the
+ argument N is computed, the argument is extracted as if the `!N'
+ history expansion had been specified.
`yank-last-arg (M-. or M-_)'
Insert last argument to the previous command (the last word of the
previous history entry). With an argument, behave exactly like
`yank-nth-arg'. Successive calls to `yank-last-arg' move back
through the history list, inserting the last argument of each line
- in turn.
+ in turn. The history expansion facilities are used to extract the
+ last argument, as if the `!$' history expansion had been specified.
\1f
File: bash.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
+--------------------------------
`delete-char (C-d)'
Delete the character at point. If point is at the beginning of
\1f
File: bash.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, 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: bash.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: bash.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
\1f
File: bash.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.
\1f
File: bash.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
`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 `$FCEDIT',
+ result as shell commands. Bash attempts to invoke `$VISUAL',
`$EDITOR', and `emacs' as the editor, in that order.
\1f
File: bash.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.
\1f
File: bash.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.
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 is the name of the
+command whose arguments are being completed, the second argument is the
+word being completed, and the third argument is the word preceding the
+word being completed on the current command line. No filtering of the
+generated completions against the word being completed is performed;
+the function or command has complete freedom in generating the matches.
Any function specified with `-F' is invoked first. The function may
use any of the shell facilities, including the `compgen' builtin
\1f
File: bash.info, Node: Programmable Completion Builtins, Prev: Programmable Completion, Up: Command Line Editing
-Programmable Completion Builtins
-================================
+8.7 Programmable Completion Builtins
+====================================
- Two builtin commands are available to manipulate the programmable
+Two builtin commands are available to manipulate the programmable
completion facilities.
`compgen'
`complete'
`complete [-abcdefgjksuv] [-o COMP-OPTION] [-A ACTION] [-G GLOBPAT] [-W WORDLIST]
- [-P PREFIX] [-S SUFFIX] [-X FILTERPAT] [-F FUNCTION]
- [-C COMMAND] NAME [NAME ...]'
+ [-F FUNCTION] [-C COMMAND] [-X FILTERPAT]
+ [-P PREFIX] [-S SUFFIX] NAME [NAME ...]'
`complete -pr [NAME ...]'
Specify how arguments to each NAME should be completed. If the
Tell Readline not to append a space (the default) to
words completed at the end of the line.
+ `plusdirs'
+ After any matches defined by the compspec are generated,
+ directory name completion is attempted and any matches
+ are added to the results of the other actions.
+
+
`-A ACTION'
The ACTION may be one of the following to generate a list of
possible completions:
for a NAME for which no specification exists, or an error occurs
adding a completion specification.
-
+
\1f
-File: bash.info, Node: Using History Interactively, Next: Command Line Editing, Prev: Job Control, Up: Top
+File: bash.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: bash.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 `$HISTSIZE' commands (default 500) is saved. The
+shell stores each command in the history list prior to parameter and
+variable expansion but after history expansion is performed, subject to
+the values of the shell variables `HISTIGNORE' and `HISTCONTROL'.
When the shell starts up, the history is initialized from the file
named by the `HISTFILE' variable (default `~/.bash_history'). The file
`$HISTFILESIZE' lines. If `HISTFILESIZE' is not set, no truncation is
performed.
+ 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
display or modify the history list and manipulate the history file.
\1f
File: bash.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
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
\1f
File: bash.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: bash.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.
`!'
Start a history substitution, except when followed by a space, tab,
\1f
File: bash.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
\1f
File: bash.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
\1f
-File: bash.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Command Line Editing, Up: Top
+File: bash.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: bash.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:
\1f
File: bash.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: bash.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: bash.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', or
by specifying a value for the `DESTDIR' `make' variable when running
\1f
File: bash.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
+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
\1f
File: bash.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: bash.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: bash.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
`--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 4.3 and later versions. If PREFIX is `yes' or
+ 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
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-debugger'
+ Include support for the bash debugger (distributed separately).
+
`--enable-directory-stack'
Include support for a `csh'-like directory stack and the `pushd',
`popd', and `dirs' builtins (*note The Directory Stack::).
This enables process substitution (*note Process Substitution::) if
the operating system provides the necessary support.
+`--enable-progcomp'
+ Enable the programmable completion facilities (*note Programmable
+ Completion::). If Readline is not enabled, this option has no
+ effect.
+
`--enable-prompt-string-decoding'
Turn on the interpretation of a number of backslash-escaped
characters in the `$PS1', `$PS2', `$PS3', and `$PS4' prompt
strings. See *Note Printing a Prompt::, for a complete list of
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-readline'
Include support for command-line editing and history with the Bash
version of the Readline library (*note Command Line Editing::).
Include the `select' builtin, which allows the generation of simple
menus (*note Conditional Constructs::).
+`--enable-separate-helpfiles'
+ Use external files for the documentation displayed by the `help'
+ builtin instead of storing the text internally.
+
+`--enable-single-help-strings'
+ Store the text displayed by the `help' builtin as a single string
+ for each help topic. This aids in translating the text to
+ different languages. You may need to disable this if your
+ compiler cannot handle very long string literals.
+
+`--enable-strict-posix-default'
+ Make Bash POSIX-conformant by default (*note Bash POSIX Mode::).
+
`--enable-usg-echo-default'
A synonym for `--enable-xpg-echo-default'.
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.
\1f
File: bash.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. The latest version of Bash is always available for FTP from
`ftp://ftp.gnu.org/pub/bash/'.
Please send all reports concerning this manual to <chet@po.CWRU.Edu>.
\1f
-File: bash.info, Node: Major Differences From The Bourne Shell, Next: Copying This Manual, Prev: Reporting Bugs, Up: Top
+File: bash.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::).
and `compgen', 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::).
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::).
+ * 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::), and allows these
- options to be set and unset at shell invocation (*note Invoking
- Bash::).
+ optional capabilities (*note The Shopt Builtin::), and allows
+ these options to be set and unset at shell invocation (*note
+ Invoking Bash::).
* Bash has much more optional behavior controllable with the `set'
builtin (*note The Set Builtin::).
+ * The `-x' (`xtrace') option displays commands other than simple
+ commands when performing an execution trace (*note The Set
+ Builtin::).
+
* The `test' builtin (*note Bourne Shell Builtins::) is slightly
different, as it implements the POSIX algorithm, which specifies
the behavior based on the number of arguments.
+ * Bash includes the `caller' builtin, which displays the context of
+ any active subroutine call (a shell function or a script executed
+ with the `.' or `source' builtins). This supports the bash
+ debugger.
+
* The `trap' builtin (*note Bourne Shell Builtins::) allows a
`DEBUG' pseudo-signal specification, similar to `EXIT'. Commands
specified with a `DEBUG' trap are executed before every simple
`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.
+ 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::).
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.
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: bash.info, Node: Copying This Manual, Next: Builtin Index, Prev: Major Differences From The Bourne Shell, Up: Top
-
-Copying This Manual
-*******************
-
-* Menu:
-
-* GNU Free Documentation License:: License for copying this manual.
-
-\1f
-File: bash.info, Node: GNU Free Documentation License, Up: Copying This Manual
+File: bash.info, Node: GNU Free Documentation License, Next: Indexes, Prev: Major Differences From The Bourne Shell, Up: Top
-GNU Free Documentation License
-==============================
+Appendix C GNU Free Documentation License
+*****************************************
Version 1.2, November 2002
+
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
- 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
-
+ 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
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 an aggregate, this
+ 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.
Free Software Foundation.
ADDENDUM: How to use this License for your documents
-----------------------------------------------------
+====================================================
- To use this License in a document you have written, include a copy of
+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:
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
- with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
- A copy of the license is included in the section entitled ``GNU
+ 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
permit their use in free software.
\1f
-File: bash.info, Node: Builtin Index, Next: Reserved Word Index, Prev: Copying This Manual, Up: Top
+File: bash.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: bash.info, Node: Builtin Index, Next: Reserved Word Index, Up: Indexes
-Index of Shell Builtin Commands
-*******************************
+D.1 Index of Shell Builtin Commands
+===================================
+\0\b[index\0\b]
* Menu:
* .: Bourne Shell Builtins.
+ (line 16)
* :: Bourne Shell Builtins.
+ (line 11)
* [: Bourne Shell Builtins.
-* alias: Bash Builtins.
+ (line 212)
+* 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.
-* caller: Bash Builtins.
+ (line 29)
+* builtin: Bash Builtins. (line 92)
+* caller: Bash Builtins. (line 100)
* cd: Bourne Shell Builtins.
-* command: Bash Builtins.
+ (line 36)
+* command: Bash Builtins. (line 117)
* compgen: Programmable Completion Builtins.
+ (line 10)
* complete: Programmable Completion Builtins.
+ (line 28)
* continue: Bourne Shell Builtins.
-* declare: Bash Builtins.
+ (line 55)
+* declare: Bash Builtins. (line 136)
* dirs: Directory Stack Builtins.
+ (line 7)
* disown: Job Control Builtins.
-* echo: Bash Builtins.
-* enable: Bash Builtins.
+ (line 83)
+* echo: Bash Builtins. (line 193)
+* enable: Bash Builtins. (line 245)
* eval: Bourne Shell Builtins.
+ (line 63)
* exec: Bourne Shell Builtins.
+ (line 70)
* exit: Bourne Shell Builtins.
+ (line 82)
* export: Bourne Shell Builtins.
+ (line 88)
* fc: Bash History Builtins.
+ (line 10)
* fg: Job Control Builtins.
+ (line 16)
* getopts: Bourne Shell Builtins.
+ (line 103)
* hash: Bourne Shell Builtins.
-* help: Bash Builtins.
+ (line 145)
+* help: Bash Builtins. (line 273)
* history: Bash History Builtins.
+ (line 39)
* jobs: Job Control Builtins.
+ (line 25)
* kill: Job Control Builtins.
-* let: Bash Builtins.
-* local: Bash Builtins.
-* logout: Bash Builtins.
+ (line 57)
+* let: Bash Builtins. (line 282)
+* local: Bash Builtins. (line 289)
+* logout: Bash Builtins. (line 299)
* popd: Directory Stack Builtins.
-* printf: Bash Builtins.
+ (line 37)
+* printf: Bash Builtins. (line 303)
* pushd: Directory Stack Builtins.
+ (line 58)
* pwd: Bourne Shell Builtins.
-* read: Bash Builtins.
+ (line 163)
+* read: Bash Builtins. (line 328)
* readonly: Bourne Shell Builtins.
+ (line 172)
* return: Bourne Shell Builtins.
-* set: The Set Builtin.
+ (line 187)
+* set: The Set Builtin. (line 11)
* shift: Bourne Shell Builtins.
-* shopt: Bash Builtins.
-* source: Bash Builtins.
+ (line 200)
+* shopt: The Shopt Builtin. (line 9)
+* source: Bash Builtins. (line 389)
* suspend: Job Control Builtins.
+ (line 94)
* test: Bourne Shell Builtins.
+ (line 212)
* times: Bourne Shell Builtins.
+ (line 280)
* trap: Bourne Shell Builtins.
-* type: Bash Builtins.
-* typeset: Bash Builtins.
-* ulimit: Bash Builtins.
+ (line 285)
+* type: Bash Builtins. (line 393)
+* typeset: Bash Builtins. (line 424)
+* ulimit: Bash Builtins. (line 430)
* umask: Bourne Shell Builtins.
-* unalias: Bash Builtins.
+ (line 326)
+* unalias: Bash Builtins. (line 510)
* unset: Bourne Shell Builtins.
+ (line 343)
* wait: Job Control Builtins.
+ (line 73)
\1f
-File: bash.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Top
+File: bash.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 8)
* [[: Conditional Constructs.
+ (line 108)
* ]]: Conditional Constructs.
+ (line 108)
* case: Conditional Constructs.
-* do: Looping Constructs.
-* done: Looping Constructs.
+ (line 28)
+* do: Looping Constructs. (line 12)
+* done: Looping Constructs. (line 12)
* elif: Conditional Constructs.
+ (line 7)
* else: Conditional Constructs.
+ (line 7)
* esac: Conditional Constructs.
+ (line 28)
* fi: Conditional Constructs.
-* for: Looping Constructs.
-* function: Shell Functions.
+ (line 7)
+* for: Looping Constructs. (line 29)
+* function: Shell Functions. (line 13)
* if: Conditional Constructs.
+ (line 7)
* in: Conditional Constructs.
+ (line 28)
* select: Conditional Constructs.
+ (line 67)
* then: Conditional Constructs.
-* time: Pipelines.
-* until: Looping Constructs.
-* while: Looping Constructs.
-* {: Command Grouping.
-* }: Command Grouping.
+ (line 7)
+* time: Pipelines. (line 8)
+* until: Looping Constructs. (line 12)
+* while: Looping Constructs. (line 20)
+* {: Command Grouping. (line 21)
+* }: Command Grouping. (line 21)
\1f
-File: bash.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Top
+File: bash.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Indexes
-Parameter and Variable Index
-****************************
+D.3 Parameter and Variable Index
+================================
+\0\b[index\0\b]
* Menu:
-* !: Special Parameters.
-* #: Special Parameters.
-* $: Special Parameters.
-* *: Special Parameters.
-* -: Special Parameters.
-* 0: Special Parameters.
-* ?: Special Parameters.
-* @: Special Parameters.
-* _: Special Parameters.
+* !: Special Parameters. (line 46)
+* #: Special Parameters. (line 30)
+* $: Special Parameters. (line 42)
+* *: Special Parameters. (line 9)
+* -: Special Parameters. (line 37)
+* 0: Special Parameters. (line 50)
+* ?: Special Parameters. (line 33)
+* @: Special Parameters. (line 19)
+* _: Special Parameters. (line 59)
* auto_resume: Job Control Variables.
-* BASH: Bash Variables.
-* BASH_ARGC: Bash Variables.
-* BASH_ARGV: Bash Variables.
-* BASH_COMMAND: Bash Variables.
-* BASH_ENV: Bash Variables.
-* BASH_EXECUTION_STRING: Bash Variables.
-* BASH_LINENO: Bash Variables.
-* BASH_SOURCE: Bash Variables.
-* BASH_SUBSHELL: Bash Variables.
-* BASH_VERSINFO: Bash Variables.
-* BASH_VERSION: Bash Variables.
+ (line 6)
+* BASH: Bash Variables. (line 13)
+* BASH_ARGC: Bash Variables. (line 21)
+* BASH_ARGV: Bash Variables. (line 31)
+* BASH_COMMAND: Bash Variables. (line 41)
+* BASH_ENV: Bash Variables. (line 46)
+* BASH_EXECUTION_STRING: Bash Variables. (line 52)
+* BASH_LINENO: Bash Variables. (line 55)
+* BASH_REMATCH: Bash Variables. (line 64)
+* BASH_SOURCE: Bash Variables. (line 72)
+* BASH_SUBSHELL: Bash Variables. (line 76)
+* BASH_VERSINFO: Bash Variables. (line 80)
+* BASH_VERSION: Bash Variables. (line 104)
+* BASHPID: Bash Variables. (line 16)
* bell-style: Readline Init File Syntax.
+ (line 38)
+* bind-tty-special-chars: Readline Init File Syntax.
+ (line 45)
* CDPATH: Bourne Shell Variables.
-* COLUMNS: Bash Variables.
+ (line 9)
+* COLUMNS: Bash Variables. (line 107)
* comment-begin: Readline Init File Syntax.
-* COMP_CWORD: Bash Variables.
-* COMP_LINE: Bash Variables.
-* COMP_POINT: Bash Variables.
-* COMP_WORDBREAKS: Bash Variables.
-* COMP_WORDS: Bash Variables.
+ (line 50)
+* COMP_CWORD: Bash Variables. (line 112)
+* COMP_KEY: Bash Variables. (line 141)
+* COMP_LINE: Bash Variables. (line 118)
+* COMP_POINT: Bash Variables. (line 123)
+* COMP_TYPE: Bash Variables. (line 131)
+* COMP_WORDBREAKS: Bash Variables. (line 145)
+* COMP_WORDS: Bash Variables. (line 151)
* completion-query-items: Readline Init File Syntax.
-* COMPREPLY: Bash Variables.
+ (line 60)
+* COMPREPLY: Bash Variables. (line 158)
* convert-meta: Readline Init File Syntax.
-* DIRSTACK: Bash Variables.
+ (line 70)
+* DIRSTACK: Bash Variables. (line 163)
* disable-completion: Readline Init File Syntax.
+ (line 76)
* editing-mode: Readline Init File Syntax.
-* EMACS: Bash Variables.
+ (line 81)
+* EMACS: Bash Variables. (line 173)
* enable-keypad: Readline Init File Syntax.
-* EUID: Bash Variables.
+ (line 87)
+* EUID: Bash Variables. (line 178)
* 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.
+ (line 92)
+* FCEDIT: Bash Variables. (line 182)
+* FIGNORE: Bash Variables. (line 186)
+* FUNCNAME: Bash Variables. (line 192)
+* GLOBIGNORE: Bash Variables. (line 201)
+* GROUPS: Bash Variables. (line 207)
+* histchars: Bash Variables. (line 213)
+* HISTCMD: Bash Variables. (line 228)
+* HISTCONTROL: Bash Variables. (line 233)
+* HISTFILE: Bash Variables. (line 249)
+* HISTFILESIZE: Bash Variables. (line 253)
+* HISTIGNORE: Bash Variables. (line 261)
* history-preserve-point: Readline Init File Syntax.
-* HISTSIZE: Bash Variables.
+ (line 96)
+* HISTSIZE: Bash Variables. (line 280)
+* HISTTIMEFORMAT: Bash Variables. (line 284)
* HOME: Bourne Shell Variables.
+ (line 13)
* horizontal-scroll-mode: Readline Init File Syntax.
-* HOSTFILE: Bash Variables.
-* HOSTNAME: Bash Variables.
-* HOSTTYPE: Bash Variables.
+ (line 102)
+* HOSTFILE: Bash Variables. (line 293)
+* HOSTNAME: Bash Variables. (line 304)
+* HOSTTYPE: Bash Variables. (line 307)
* IFS: Bourne Shell Variables.
-* IGNOREEOF: Bash Variables.
+ (line 18)
+* IGNOREEOF: Bash Variables. (line 310)
* input-meta: Readline Init File Syntax.
-* INPUTRC: Bash Variables.
+ (line 109)
+* INPUTRC: Bash Variables. (line 320)
* isearch-terminators: Readline Init File Syntax.
+ (line 116)
* keymap: Readline Init File Syntax.
-* LANG: Bash Variables.
-* LC_ALL: Bash Variables.
-* LC_COLLATE: Bash Variables.
-* LC_CTYPE: Bash Variables.
-* LC_MESSAGES <1>: Locale Translation.
-* LC_MESSAGES: Bash Variables.
-* LC_NUMERIC: Bash Variables.
-* LINENO: Bash Variables.
-* LINES: Bash Variables.
-* MACHTYPE: Bash Variables.
+ (line 123)
+* LANG: Bash Variables. (line 324)
+* LC_ALL: Bash Variables. (line 328)
+* LC_COLLATE: Bash Variables. (line 332)
+* LC_CTYPE: Bash Variables. (line 339)
+* LC_MESSAGES <1>: Locale Translation. (line 11)
+* LC_MESSAGES: Bash Variables. (line 344)
+* LC_NUMERIC: Bash Variables. (line 348)
+* LINENO: Bash Variables. (line 352)
+* LINES: Bash Variables. (line 356)
+* MACHTYPE: Bash Variables. (line 361)
* MAIL: Bourne Shell Variables.
-* MAILCHECK: Bash Variables.
+ (line 22)
+* MAILCHECK: Bash Variables. (line 365)
* MAILPATH: Bourne Shell Variables.
+ (line 27)
* mark-modified-lines: Readline Init File Syntax.
+ (line 136)
* mark-symlinked-directories: Readline Init File Syntax.
+ (line 141)
* match-hidden-files: Readline Init File Syntax.
+ (line 146)
* meta-flag: Readline Init File Syntax.
-* OLDPWD: Bash Variables.
+ (line 109)
+* OLDPWD: Bash Variables. (line 373)
* OPTARG: Bourne Shell Variables.
-* OPTERR: Bash Variables.
+ (line 34)
+* OPTERR: Bash Variables. (line 376)
* OPTIND: Bourne Shell Variables.
-* OSTYPE: Bash Variables.
+ (line 38)
+* OSTYPE: Bash Variables. (line 380)
* output-meta: Readline Init File Syntax.
+ (line 153)
* page-completions: Readline Init File Syntax.
+ (line 158)
* PATH: Bourne Shell Variables.
-* PIPESTATUS: Bash Variables.
-* POSIXLY_CORRECT: Bash Variables.
-* PPID: Bash Variables.
-* PROMPT_COMMAND: Bash Variables.
+ (line 42)
+* PIPESTATUS: Bash Variables. (line 383)
+* POSIXLY_CORRECT: Bash Variables. (line 388)
+* PPID: Bash Variables. (line 397)
+* PROMPT_COMMAND: Bash Variables. (line 401)
* 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 405)
+* PS4: Bash Variables. (line 410)
+* PWD: Bash Variables. (line 416)
+* RANDOM: Bash Variables. (line 419)
+* REPLY: Bash Variables. (line 424)
+* SECONDS: Bash Variables. (line 427)
+* SHELL: Bash Variables. (line 433)
+* SHELLOPTS: Bash Variables. (line 438)
+* SHLVL: Bash Variables. (line 447)
* show-all-if-ambiguous: Readline Init File Syntax.
+ (line 168)
* show-all-if-unmodified: Readline Init File Syntax.
-* TEXTDOMAIN: Locale Translation.
-* TEXTDOMAINDIR: Locale Translation.
-* TIMEFORMAT: Bash Variables.
-* TMOUT: Bash Variables.
-* UID: Bash Variables.
+ (line 174)
+* TEXTDOMAIN: Locale Translation. (line 11)
+* TEXTDOMAINDIR: Locale Translation. (line 11)
+* TIMEFORMAT: Bash Variables. (line 452)
+* TMOUT: Bash Variables. (line 490)
+* TMPDIR: Bash Variables. (line 502)
+* UID: Bash Variables. (line 506)
* visible-stats: Readline Init File Syntax.
+ (line 183)
\1f
-File: bash.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Top
+File: bash.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 11)
+* backward-kill-line (C-x Rubout): Commands For Killing. (line 9)
+* backward-kill-word (M-<DEL>): Commands For Killing. (line 24)
+* backward-word (M-b): Commands For Moving. (line 22)
+* beginning-of-history (M-<): Commands For History. (line 20)
+* beginning-of-line (C-a): Commands For Moving. (line 6)
+* call-last-kbd-macro (C-x e): Keyboard Macros. (line 13)
+* capitalize-word (M-c): Commands For Text. (line 46)
* character-search (C-]): Miscellaneous Commands.
+ (line 41)
* character-search-backward (M-C-]): Miscellaneous Commands.
-* clear-screen (C-l): Commands For Moving.
+ (line 46)
+* clear-screen (C-l): Commands For Moving. (line 26)
* 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 49)
+* copy-forward-word (): Commands For Killing. (line 54)
+* copy-region-as-kill (): Commands For Killing. (line 45)
+* delete-char (C-d): Commands For Text. (line 6)
* delete-char-or-list (): Commands For Completion.
-* delete-horizontal-space (): Commands For Killing.
-* digit-argument (M-0, M-1, ... M--): Numeric Arguments.
+ (line 34)
+* delete-horizontal-space (): Commands For Killing. (line 37)
+* digit-argument (M-0, M-1, ... M--): Numeric Arguments. (line 6)
* do-uppercase-version (M-a, M-b, M-X, ...): Miscellaneous Commands.
-* downcase-word (M-l): Commands For Text.
+ (line 14)
+* downcase-word (M-l): Commands For Text. (line 42)
* dump-functions (): Miscellaneous Commands.
+ (line 64)
* dump-macros (): Miscellaneous Commands.
+ (line 76)
* 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 70)
+* end-kbd-macro (C-x )): Keyboard Macros. (line 9)
+* end-of-history (M->): Commands For History. (line 23)
+* end-of-line (C-e): Commands For Moving. (line 9)
* exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
-* 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 15)
+* forward-char (C-f): Commands For Moving. (line 12)
+* forward-search-history (C-s): Commands For History. (line 31)
+* forward-word (M-f): Commands For Moving. (line 18)
+* history-search-backward (): Commands For History. (line 51)
+* history-search-forward (): Commands For History. (line 46)
* insert-comment (M-#): Miscellaneous Commands.
+ (line 51)
* insert-completions (M-*): Commands For Completion.
-* 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 18)
+* kill-line (C-k): Commands For Killing. (line 6)
+* kill-region (): Commands For Killing. (line 41)
+* 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 22)
+* next-history (C-n): Commands For History. (line 17)
* non-incremental-forward-search-history (M-n): Commands For History.
+ (line 41)
* non-incremental-reverse-search-history (M-p): Commands For History.
-* overwrite-mode (): Commands For Text.
+ (line 36)
+* overwrite-mode (): Commands For Text. (line 50)
* 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)
+* quoted-insert (C-q or C-v): Commands For Text. (line 20)
* re-read-init-file (C-x C-r): Miscellaneous Commands.
-* redraw-current-line (): Commands For Moving.
-* reverse-search-history (C-r): Commands For History.
+ (line 6)
+* redraw-current-line (): Commands For Moving. (line 30)
+* reverse-search-history (C-r): Commands For History. (line 27)
* revert-line (M-r): Miscellaneous Commands.
-* self-insert (a, b, A, 1, !, ...): Commands For Text.
+ (line 25)
+* self-insert (a, b, A, 1, !, ...): Commands For Text. (line 24)
* set-mark (C-@): Miscellaneous Commands.
-* start-kbd-macro (C-x (): Keyboard Macros.
-* transpose-chars (C-t): Commands For Text.
-* transpose-words (M-t): Commands For Text.
+ (line 32)
+* start-kbd-macro (C-x (): Keyboard Macros. (line 6)
+* transpose-chars (C-t): Commands For Text. (line 27)
+* transpose-words (M-t): Commands For Text. (line 33)
* undo (C-_ or C-x C-u): Miscellaneous Commands.
-* 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 32)
+* unix-line-discard (C-u): Commands For Killing. (line 12)
+* unix-word-rubout (C-w): Commands For Killing. (line 28)
+* upcase-word (M-u): Commands For Text. (line 38)
+* yank (C-y): Commands For Killing. (line 59)
+* yank-last-arg (M-. or M-_): Commands For History. (line 65)
+* yank-nth-arg (M-C-y): Commands For History. (line 56)
+* yank-pop (M-y): Commands For Killing. (line 62)
\1f
-File: bash.info, Node: Concept Index, Prev: Function Index, Up: Top
+File: bash.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 8)
+* 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)
+* 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 25)
+* 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.
-* FDL, GNU Free Documentation License: GNU Free Documentation License.
-* field: Definitions.
-* filename: Definitions.
-* filename expansion: Filename Expansion.
-* foreground: Job Control Basics.
-* functions, shell: Shell Functions.
+ (line 6)
+* field: Definitions. (line 29)
+* filename: Definitions. (line 34)
+* 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 7)
+* history expansion: History Interaction. (line 6)
* history list: Bash History Facilities.
+ (line 6)
* History, how to use: Programmable Completion Builtins.
-* identifier: Definitions.
-* initialization file, readline: Readline Init File.
-* installation: Basic Installation.
+ (line 209)
+* identifier: Definitions. (line 50)
+* 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.
-* internationalization: Locale Translation.
-* job: Definitions.
-* job control <1>: Job Control Basics.
-* job control: Definitions.
+ (line 6)
+* interactive shell <1>: Interactive Shells. (line 6)
+* interactive shell: Invoking Bash. (line 127)
+* internationalization: Locale Translation. (line 6)
+* job: Definitions. (line 37)
+* job control <1>: Job Control Basics. (line 6)
+* job control: Definitions. (line 41)
* kill ring: Readline Killing Commands.
+ (line 19)
* killing text: Readline Killing Commands.
-* localization: Locale Translation.
-* login shell: Invoking Bash.
-* matching, pattern: Pattern Matching.
-* metacharacter: Definitions.
-* name: Definitions.
-* native languages: Locale Translation.
+ (line 6)
+* localization: Locale Translation. (line 6)
+* login shell: Invoking Bash. (line 124)
+* matching, pattern: Pattern Matching. (line 6)
+* metacharacter: Definitions. (line 45)
+* name: Definitions. (line 50)
+* native languages: Locale Translation. (line 6)
* notation, readline: Readline Bare Essentials.
-* operator, shell: Definitions.
+ (line 6)
+* operator, shell: Definitions. (line 56)
* 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 60)
+* process group ID: Definitions. (line 64)
* process substitution: Process Substitution.
+ (line 6)
* programmable completion: Programmable Completion.
-* prompting: Printing a Prompt.
-* quoting: Quoting.
-* quoting, ANSI: ANSI-C Quoting.
+ (line 6)
+* prompting: Printing a Prompt. (line 6)
+* quoting: Quoting. (line 6)
+* quoting, ANSI: ANSI-C Quoting. (line 6)
* Readline, how to use: Job Control Variables.
-* redirection: Redirections.
-* reserved word: Definitions.
+ (line 24)
+* redirection: Redirections. (line 6)
+* reserved word: Definitions. (line 68)
* 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.
-* translation, native languages: Locale Translation.
-* variable, shell: Shell Parameters.
+ (line 6)
+* return status: Definitions. (line 73)
+* 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 76)
+* signal handling: Signals. (line 6)
+* special builtin <1>: Special Builtins. (line 6)
+* special builtin: Definitions. (line 80)
+* startup files: Bash Startup Files. (line 6)
+* suspending jobs: Job Control Basics. (line 6)
+* tilde expansion: Tilde Expansion. (line 6)
+* token: Definitions. (line 84)
+* 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 88)
+* word splitting: Word Splitting. (line 6)
* yanking text: Readline Killing Commands.
+ (line 6)
\1f
Tag Table:
-Node: Top\7f1363
-Node: Introduction\7f3512
-Node: What is Bash?\7f3737
-Node: What is a shell?\7f4838
-Node: Definitions\7f7072
-Node: Basic Shell Features\7f9812
-Node: Shell Syntax\7f11041
-Node: Shell Operation\7f12065
-Node: Quoting\7f13350
-Node: Escape Character\7f14612
-Node: Single Quotes\7f15084
-Node: Double Quotes\7f15419
-Node: ANSI-C Quoting\7f16432
-Node: Locale Translation\7f17375
-Node: Comments\7f18258
-Node: Shell Commands\7f18863
-Node: Simple Commands\7f19744
-Node: Pipelines\7f20365
-Node: Lists\7f21901
-Node: Looping Constructs\7f23524
-Node: Conditional Constructs\7f25969
-Node: Command Grouping\7f31985
-Node: Shell Functions\7f33362
-Node: Shell Parameters\7f37152
-Node: Positional Parameters\7f38714
-Node: Special Parameters\7f39605
-Node: Shell Expansions\7f42263
-Node: Brace Expansion\7f44183
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-Node: Shell Parameter Expansion\7f48831
-Node: Command Substitution\7f56085
-Node: Arithmetic Expansion\7f57407
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-Node: Word Splitting\7f59285
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-Node: Pattern Matching\7f62722
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-Node: Exit Status\7f82766
-Node: Signals\7f83961
-Node: Shell Scripts\7f85872
-Node: Shell Builtin Commands\7f88383
-Node: Bourne Shell Builtins\7f89813
-Node: Bash Builtins\7f106585
-Node: The Set Builtin\7f134397
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-Node: Readline Interaction\7f219854
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-Node: Copying This Manual\7f328729
-Node: GNU Free Documentation License\7f328983
-Node: Builtin Index\7f351376
-Node: Reserved Word Index\7f355003
-Node: Variable Index\7f356479
-Node: Function Index\7f363358
-Node: Concept Index\7f367908
+Node: Top\7f1348
+Node: Introduction\7f3187
+Node: What is Bash?\7f3415
+Node: What is a shell?\7f4528
+Node: Definitions\7f7068
+Node: Basic Shell Features\7f9837
+Node: Shell Syntax\7f11056
+Node: Shell Operation\7f12086
+Node: Quoting\7f13380
+Node: Escape Character\7f14683
+Node: Single Quotes\7f15168
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+Node: Shell Parameters\7f40745
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+Node: Shell Expansions\7f46939
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+Node: Readline Bare Essentials\7f236803
+Node: Readline Movement Commands\7f238592
+Node: Readline Killing Commands\7f239557
+Node: Readline Arguments\7f241477
+Node: Searching\7f242521
+Node: Readline Init File\7f244707
+Node: Readline Init File Syntax\7f245854
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+Node: Sample Init File\7f260762
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+Node: Indexes\7f371742
+Node: Builtin Index\7f372196
+Node: Reserved Word Index\7f378729
+Node: Variable Index\7f381177
+Node: Function Index\7f392341
+Node: Concept Index\7f399073
\1f
End Tag Table
projects / thirdparty / bash.git / commitdiff
