@settitle Bash Reference Manual
@c %**end of header
-@ignore
-Last Change: Tue Nov 13 12:48:51 EST 2001
-@end ignore
-
-@set EDITION 2.5a
-@set VERSION 2.05a
-@set UPDATED 13 November 2001
-@set UPDATE-MONTH November 2001
-
-@iftex
-@finalout
-@end iftex
-
@setchapternewpage odd
-@defcodeindex bt
-@defcodeindex rw
-@set BashFeatures
-@ifinfo
-@dircategory Utilities
-@direntry
- * Bash: (bash). The GNU Bourne-Again SHell.
-@end direntry
+@include version.texi
-@format
+@copying
This text is a brief description of the features that are present in
-the Bash shell.
+the Bash shell (version @value{VERSION}, @value{UPDATED}).
This is Edition @value{EDITION}, last updated @value{UPDATED},
of @cite{The GNU Bash Reference Manual},
for @code{Bash}, Version @value{VERSION}.
-Copyright (C) 1991-2001 Free Software Foundation, Inc.
+Copyright @copyright{} 1988--2009 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.
-@ignore
-Permission is granted to process this file through TeX and print the
-results, provided the printed document carries copying permission
-notice identical to this one except for the removal of this paragraph
-(this paragraph not being relevant to the printed manual).
-
-@end ignore
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
-
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Free Software Foundation.
-@end format
-@end ifinfo
+@quotation
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with the Front-Cover texts being ``A GNU Manual'',
+and with the Back-Cover Texts as in (a) below. A copy of the license is
+included in the section entitled ``GNU Free Documentation License''.
+
+(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.''
+
+@end quotation
+@end copying
+
+@defcodeindex bt
+@defcodeindex rw
+@set BashFeatures
+
+@dircategory Basics
+@direntry
+* Bash: (bash). The GNU Bourne-Again SHell.
+@end direntry
+
+@finalout
@titlepage
@title Bash Reference Manual
@subtitle Reference Documentation for Bash
@subtitle Edition @value{EDITION}, for @code{Bash} Version @value{VERSION}.
-@subtitle @value{UPDATE-MONTH}
+@subtitle @value{UPDATED-MONTH}
@author Chet Ramey, Case Western Reserve University
@author Brian Fox, Free Software Foundation
+
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1991-1999 Free Software Foundation, Inc.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
+@insertcopying
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided that the entire
-resulting derived work is distributed under the terms of a permission
-notice identical to this one.
+@sp 1
+Published by the Free Software Foundation @*
+59 Temple Place, Suite 330, @*
+Boston, MA 02111-1307 @*
+USA @*
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions,
-except that this permission notice may be stated in a translation approved
-by the Free Software Foundation.
@end titlepage
-@ifinfo
+@contents
+
+@ifnottex
@node Top, Introduction, (dir), (dir)
@top Bash Features
-@end ifinfo
-@ifinfo
This text is a brief description of the features that are present in
-the Bash shell.
+the Bash shell (version @value{VERSION}, @value{UPDATED}).
This is Edition @value{EDITION}, last updated @value{UPDATED},
of @cite{The GNU Bash Reference Manual},
for @code{Bash}, Version @value{VERSION}.
-Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
-
Bash contains features that appear in other popular shells, and some
features that only appear in Bash. Some of the shells that Bash has
borrowed concepts from are the Bourne Shell (@file{sh}), the Korn Shell
@menu
* Introduction:: An introduction to the shell.
-
* Definitions:: Some definitions used in the rest of this
manual.
-
* Basic Shell Features:: The shell "building blocks".
-
* Shell Builtin Commands:: Commands that are a part of the shell.
-
* Shell Variables:: Variables used or set by Bash.
-
* Bash Features:: Features found only in Bash.
-
-* Job Control:: A chapter describing what job control is
- and how Bash allows you to use it.
-
-* Using History Interactively:: Chapter dealing with history expansion
- rules.
-
+* Job Control:: What job control is and how Bash allows you
+ to use it.
* Command Line Editing:: Chapter describing the command line
editing features.
-
+* Using History Interactively:: Command History Expansion
* Installing Bash:: How to build and install Bash on your system.
-
* Reporting Bugs:: How to report bugs in Bash.
-
* Major Differences From The Bourne Shell:: A terse list of the differences
between Bash and historical
versions of /bin/sh.
-
-* Builtin Index:: Index of Bash builtin commands.
-
-* Reserved Word Index:: Index of Bash reserved words.
-
-* Variable Index:: Quick reference helps you find the
- variable you want.
-
-* Function Index:: Index of bindable Readline functions.
-
-* Concept Index:: General index for concepts described in
- this manual.
+* GNU Free Documentation License:: Copying and sharing this documentation.
+* Indexes:: Various indexes for this manual.
@end menu
-@end ifinfo
+@end ifnottex
@node Introduction
@chapter Introduction
@menu
* What is Bash?:: A short description of Bash.
-
* What is a shell?:: A brief introduction to shells.
@end menu
for the @sc{gnu} operating system.
The name is an acronym for the @samp{Bourne-Again SHell},
a pun on Stephen Bourne, the author of the direct ancestor of
-the current Unix shell @code{/bin/sh},
+the current Unix shell @code{sh},
which appeared in the Seventh Edition Bell Labs Research version
of Unix.
Bash is largely compatible with @code{sh} and incorporates useful
features from the Korn shell @code{ksh} and the C shell @code{csh}.
It is intended to be a conformant implementation of the @sc{ieee}
-@sc{posix} Shell and Tools specification (@sc{ieee} Working Group 1003.2).
+@sc{posix} Shell and Tools portion of the @sc{ieee} @sc{posix}
+specification (@sc{ieee} Standard 1003.1).
It offers functional improvements over @code{sh} for both interactive and
programming use.
Like other @sc{gnu} software, Bash is quite portable. It currently runs
on nearly every version of Unix and a few other operating systems @minus{}
independently-supported ports exist for @sc{ms-dos}, @sc{os/2},
-Windows @sc{95/98}, and Windows @sc{nt}.
+and Windows platforms.
@node What is a shell?
@section What is a shell?
At its base, a shell is simply a macro processor that executes
-commands. A Unix shell is both a command interpreter, which
-provides the user interface to the rich set of @sc{gnu} utilities,
-and a programming language, allowing these utilitites to be
-combined. Files containing commands can be created, and become
+commands. The term macro processor means functionality where text
+and symbols are expanded to create larger expressions.
+
+A Unix shell is both a command interpreter and a programming
+language. As a command interpreter, the shell provides the user
+interface to the rich set of @sc{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 @file{/bin}, allowing users
-or groups to establish custom environments.
+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 @sc{gnu} commands, both synchronously and
asynchronously.
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.
Shells also provide a small set of built-in
commands (@dfn{builtins}) implementing functionality impossible
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
+editing, command history and aliases. Each of these features is
described in this manual.
@node Definitions
@item POSIX
@cindex POSIX
A family of open system standards based on Unix. Bash
-is concerned with @sc{posix} 1003.2, the Shell and Tools Standard.
+is primarily concerned with the Shell and Utilities portion of the
+@sc{posix} 1003.1 standard.
@item blank
A space or tab character.
@item control operator
@cindex control operator
-A @code{word} that performs a control function. It is a @code{newline}
+A @code{token} that performs a control function. It is a @code{newline}
or one of the following:
@samp{||}, @samp{&&}, @samp{&}, @samp{;}, @samp{;;},
-@samp{|}, @samp{(}, or @samp{)}.
+@samp{|}, @samp{|&}, @samp{(}, or @samp{)}.
@item exit status
@cindex exit status
@cindex operator, shell
A @code{control operator} or a @code{redirection operator}.
@xref{Redirections}, for a list of redirection operators.
+Operators contain at least one unquoted @code{metacharacter}.
@item process group
@cindex process group
@item process group ID
@cindex process group ID
-A unique identifer that represents a @code{process group}
+A unique identifier that represents a @code{process group}
during its lifetime.
@item reserved word
@item special builtin
@cindex special builtin
A shell builtin command that has been classified as special by the
-@sc{posix} 1003.2 standard.
+@sc{posix} standard.
@item token
@cindex token
-A sequence of characters considered a single unit by the shell. It is
-either a @code{word} or an @code{operator}.
+A sequence of characters considered a single unit by the shell.
+It is either a @code{word} or an @code{operator}.
@item word
@cindex word
-A @code{token} that is not an @code{operator}.
+A sequence of characters treated as a unit by the shell.
+Words may not include unquoted @code{metacharacters}.
@end table
@node Basic Shell Features
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 @sc{posix}
-1003.2 specification for the `standard' Unix shell.
+The rules for evaluation and quoting are taken from the @sc{posix}
+specification for the `standard' Unix shell.
This chapter briefly summarizes the shell's `building blocks':
commands, control structures, shell functions, shell @i{parameters},
* Shell Syntax:: What your input means to the shell.
* Shell Commands:: The types of commands you can use.
* Shell Functions:: Grouping commands by name.
-* Shell Parameters:: Special shell variables.
-* Shell Expansions:: How Bash expands variables and the various
+* Shell Parameters:: How the shell stores values.
+* Shell Expansions:: How Bash expands parameters and the various
expansions available.
* Redirections:: A way to control where input and output go.
* Executing Commands:: What happens when you run a command.
@section 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.
@end 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.
@end menu
Each of the shell metacharacters (@pxref{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
+When the command history expansion facilities are being used
+(@pxref{History Interaction}), the
@var{history expansion} character, usually @samp{!}, must be quoted
to prevent history expansion. @xref{Bash History Facilities}, for
more details concerning history expansion.
+
There are three quoting mechanisms: the
@var{escape character}, single quotes, and double quotes.
Enclosing characters in double quotes (@samp{"}) preserves the literal value
of all characters within the quotes, with the exception of
-@samp{$}, @samp{`}, and @samp{\}.
+@samp{$}, @samp{`}, @samp{\},
+and, when history expansion is enabled, @samp{!}.
The characters @samp{$} and @samp{`}
retain their special meaning within double quotes (@pxref{Shell Expansions}).
The backslash retains its special meaning only when followed by one of
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 @samp{!}
+appearing in double quotes is escaped using a backslash.
+The backslash preceding the @samp{!} is not removed.
The special parameters @samp{*} and @samp{@@} have special meaning
when in double quotes (@pxref{Shell Parameter Expansion}).
@item \x@var{HH}
the eight-bit character whose value is the hexadecimal value @var{HH}
(one or two hex digits)
+@item \c@var{x}
+a control-@var{x} character
@end table
@noindent
In a non-interactive shell, or an interactive shell in which the
@code{interactive_comments} option to the @code{shopt}
-builtin is enabled (@pxref{Bash Builtins}),
+builtin is enabled (@pxref{The Shopt Builtin}),
a word beginning with @samp{#}
causes that word and all remaining characters on that line to
be ignored. An interactive shell without the @code{interactive_comments}
* Pipelines:: Connecting the input and output of several
commands.
* Lists:: How to execute commands sequentially.
-* Looping Constructs:: Shell commands for iterative action.
-* Conditional Constructs:: Shell commands for conditional execution.
-* Command Grouping:: Ways to group commands.
+* Compound Commands:: Shell commands for control flow.
+* Coprocesses:: Two-way communication between commands.
@end menu
@node Simple Commands
@cindex pipeline
@cindex commands, pipelines
-A @code{pipeline} is a sequence of simple commands separated by
-@samp{|}.
+A @code{pipeline} is a sequence of simple commands separated by one of
+the control operators @samp{|} or @samp{|&}.
@rwindex time
@rwindex !
@cindex command timing
The format for a pipeline is
@example
-[@code{time} [@code{-p}]] [@code{!}] @var{command1} [@code{|} @var{command2} @dots{}]
+[@code{time} [@code{-p}]] [@code{!}] @var{command1} [ [@code{|} or @code{|&}] @var{command2} @dots{}]
@end example
@noindent
The output of each command in the pipeline is connected via a pipe
to the input of the next command.
-That is, each command reads the previous command's output.
+That is, each command reads the previous command's output. This
+connection is performed before any redirections specified by the
+command.
+
+If @samp{|&} is used, the standard error of @var{command1} is connected to
+@var{command2}'s standard input through the pipe; it is shorthand for
+@code{2>&1 |}. This implicit redirection of the standard error is
+performed after any redirections specified by the command.
The reserved word @code{time} causes timing statistics
to be printed for the pipeline once it finishes.
Each command in a pipeline is executed in its own subshell
(@pxref{Command Execution Environment}). The exit
status of a pipeline is the exit status of the last command in the
-pipeline. If the reserved word @samp{!} precedes the pipeline, the
-exit status is the logical negation of the exit status of the last command.
+pipeline, unless the @code{pipefail} option is enabled
+(@pxref{The Set Builtin}).
+If @code{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 @samp{!} 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.
@node Lists
@subsection Lists of Commands
have equal precedence, followed by @samp{;} and @samp{&},
which have equal precedence.
+A sequence of one or more newlines may appear in a @code{list}
+to delimit commands, equivalent to a semicolon.
+
If a command is terminated by the control operator @samp{&},
the shell executes the command asynchronously in a subshell.
This is known as executing the command in the @var{background}.
waits for each command to terminate in turn. The return status is the
exit status of the last command executed.
-The control operators @samp{&&} and @samp{||}
-denote @sc{and} lists and @sc{or} lists, respectively.
+@sc{and} and @sc{or} lists are sequences of one or more pipelines
+separated by the control operators @samp{&&} and @samp{||},
+respectively. @sc{and} and @sc{or} lists are executed with left
+associativity.
+
An @sc{and} list has the form
@example
@var{command1} && @var{command2}
@sc{and} and @sc{or} lists is the exit status of the last command
executed in the list.
+@node Compound Commands
+@subsection Compound Commands
+@cindex commands, compound
+
+@menu
+* Looping Constructs:: Shell commands for iterative action.
+* Conditional Constructs:: Shell commands for conditional execution.
+* Command Grouping:: Ways to group commands.
+@end menu
+
+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 (@pxref{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.
+
@node Looping Constructs
-@subsection Looping Constructs
+@subsubsection Looping Constructs
@cindex commands, looping
Bash supports the following looping constructs.
may be used to control loop execution.
@node Conditional Constructs
-@subsection Conditional Constructs
+@subsubsection Conditional Constructs
@cindex commands, conditional
@table @code
@code{case} will selectively execute the @var{command-list} corresponding to
the first @var{pattern} that matches @var{word}.
+If the shell option @code{nocasematch}
+(see the description of @code{shopt} in @ref{The Shopt Builtin})
+is enabled, the match is performed without regard to the case
+of alphabetic characters.
The @samp{|} is used to separate multiple patterns, and the @samp{)}
operator terminates a pattern list.
A list of patterns and an associated command-list is known
-as a @var{clause}. Each clause must be terminated with @samp{;;}.
+as a @var{clause}.
+
+Each clause must be terminated with @samp{;;}, @samp{,&}, or @samp{;;&}.
The @var{word} undergoes tilde expansion, parameter expansion, command
substitution, arithmetic expansion, and quote removal before matching is
attempted. Each @var{pattern} undergoes tilde expansion, parameter
expansion, command substitution, and arithmetic expansion.
There may be an arbitrary number of @code{case} clauses, each terminated
-by a @samp{;;}. The first pattern that matches determines the
+by a @samp{;;}, @samp{;&}, or @samp{;;&}.
+The first pattern that matches determines the
command-list that is executed.
Here is an example using @code{case} in a script that could be used to
@end example
@noindent
+
+If the @samp{;;} operator is used, no subsequent matches are attempted after
+the first pattern match.
+Using @samp{;&} in place of @samp{;;} causes execution to continue with
+the @var{command-list} associated with the next clause, if any.
+Using @samp{;;&} in place of @samp{;;} causes the shell to test the patterns
+in the next clause, if any, and execute any associated @var{command-list}
+on a successful match.
+
The return status is zero if no @var{pattern} is matched. Otherwise, the
return status is the exit status of the @var{command-list} executed.
of items. The set of expanded words is printed on the standard
error output stream, each preceded by a number. If the
@samp{in @var{words}} is omitted, the positional parameters are printed,
-as if @samp{in "$@@"} had been specifed.
+as if @samp{in "$@@"} had been specified.
The @env{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
between the @samp{[[} and @samp{]]}; tilde expansion, parameter and
variable expansion, arithmetic expansion, command substitution, process
substitution, and quote removal are performed.
+Conditional operators such as @samp{-f} must be unquoted to be recognized
+as primaries.
When the @samp{==} and @samp{!=} operators are used, the string to the
right of the operator is considered a pattern and matched according
to the rules described below in @ref{Pattern Matching}.
-The return value is 0 if the string matches or does not match
-the pattern, respectively, and 1 otherwise.
+If the shell option @code{nocasematch}
+(see the description of @code{shopt} in @ref{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 (@samp{==}) or does not
+match (@samp{!=})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, @samp{=~}, is available, with the same
+precedence as @samp{==} and @samp{!=}.
+When it is used, the string to the right of the operator is considered
+an extended regular expression and matched accordingly (as in @i{regex}3)).
+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 @code{nocasematch}
+(see the description of @code{shopt} in @ref{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 @code{BASH_REMATCH}.
+The element of @code{BASH_REMATCH} with index 0 is the portion of the string
+matching the entire regular expression.
+The element of @code{BASH_REMATCH} with index @var{n} is the portion of the
+string matching the @var{n}th parenthesized subexpression.
Expressions may be combined using the following operators, listed
in decreasing order of precedence:
True if either @var{expression1} or @var{expression2} is true.
@end table
@noindent
-The @code{&&} and @code{||} commands do not execute @var{expression2} if the
+The @code{&&} and @code{||} operators do not evaluate @var{expression2} if the
value of @var{expression1} is sufficient to determine the return
value of the entire conditional expression.
@end table
@node Command Grouping
-@subsection Grouping Commands
+@subsubsection Grouping Commands
@cindex commands, grouping
Bash provides two ways to group a list of commands to be executed
@end example
Placing a list of commands between parentheses causes a subshell
-to be created, and each of the commands in @var{list} to be executed
-in that subshell. Since the @var{list} is executed in a subshell,
-variable assignments do not remain in effect after the subshell completes.
+environment to be created (@pxref{Command Execution Environment}), and each
+of the commands in @var{list} to be executed in that subshell. Since the
+@var{list} is executed in a subshell, variable assignments do not remain in
+effect after the subshell completes.
@item @{@}
@rwindex @{
In addition to the creation of a subshell, there is a subtle difference
between these two constructs due to historical reasons. The braces
are @code{reserved words}, so they must be separated from the @var{list}
-by @code{blank}s. The parentheses are @code{operators}, and are
+by @code{blank}s or other shell metacharacters.
+The parentheses are @code{operators}, and are
recognized as separate tokens by the shell even if they are not separated
from the @var{list} by whitespace.
The exit status of both of these constructs is the exit status of
@var{list}.
+@node Coprocesses
+@subsection Coprocesses
+@cindex coprocess
+
+A @code{coprocess} is a shell command preceded by the @code{coproc}
+reserved word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the @samp{&} control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+
+The format for a coprocess is:
+@example
+@code{coproc} [@var{NAME}] @var{command} [@var{redirections}]
+@end example
+
+@noindent
+This creates a coprocess named @var{NAME}.
+If @var{NAME} is not supplied, the default name is @var{COPROC}.
+
+When the coproc is executed, the shell creates an array variable
+(@pxref{Arrays})
+named @var{NAME} in the context of the executing shell.
+The standard output of @var{command}
+is connected via a pipe to a file descriptor in the executing shell,
+and that file descriptor is assigned to @var{NAME}[0].
+The standard input of @var{command}
+is connected via a pipe to a file descriptor in the executing shell,
+and that file descriptor is assigned to @var{NAME}[1].
+This pipe is established before any redirections specified by the
+command (@pxref{Redirections}).
+The file descriptors can be utilized as arguments to shell commands
+and redirections using standard word expansions.
+
+The process id of the shell spawned to execute the coprocess is
+available as the value of the variable @var{NAME}_PID.
+The @code{wait}
+builtin command may be used to wait for the coprocess to terminate.
+
+The return status of a coprocess is the exit status of @var{command}.
+
@node Shell Functions
@section Shell Functions
@cindex shell function
Functions are declared using this syntax:
@rwindex function
@example
-[ @code{function} ] @var{name} () @{ @var{command-list}; @}
+[ @code{function} ] @var{name} () @var{compound-command} [ @var{redirections} ]
@end example
This defines a shell function named @var{name}. The reserved
word @code{function} is optional.
If the @code{function} reserved
word is supplied, the parentheses are optional.
-The @var{body} of the function is the @var{command-list} between @{ and @}.
-This list is executed whenever @var{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
+The @var{body} of the function is the compound command
+@var{compound-command} (@pxref{Compound Commands}).
+That command is usually a @var{list} enclosed between @{ and @}, but
+may be any compound command listed above.
+@var{compound-command} is executed whenever @var{name} is specified as the
+name of a command.
+Any redirections (@pxref{Redirections}) associated with the shell function
+are performed when the function is executed.
+
+A function definition may be deleted using the @option{-f} option to the
+@code{unset} builtin (@pxref{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
@code{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 @var{command-list} must be terminated with a semicolon
-or a newline.
+as such when they are separated from the command list
+by whitespace or another shell metacharacter.
+Also, when using the braces, the @var{list} must be terminated by a semicolon,
+a @samp{&}, or a newline.
When a function is executed, the arguments to the
function become the positional parameters
during its execution (@pxref{Positional Parameters}).
The special parameter @samp{#} that expands to the number of
positional parameters is updated to reflect the change.
-Positional parameter @code{0} is unchanged.
-The @env{FUNCNAME} variable is set to the name of the function
-while the function is executing.
+Special parameter @code{0} is unchanged.
+The first element of the @env{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 @env{DEBUG} and @env{RETURN} traps
+are not inherited unless the function has been given the
+@code{trace} attribute using the @code{declare} builtin or
+the @code{-o functrace} option has been enabled with
+the @code{set} builtin,
+(in which case all functions inherit the @env{DEBUG} and @env{RETURN} traps).
+@xref{Bourne Shell Builtins}, for the description of the
+@code{trap} builtin.
If the builtin command @code{return}
is executed in a function, the function completes and
execution resumes with the next command after the function
-call. When a function completes, the values of the
+call.
+Any command associated with the @code{RETURN} trap is executed
+before execution resumes.
+When a function completes, the values of the
positional parameters and the special parameter @samp{#}
are restored to the values they had prior to the function's
execution. If a numeric argument is given to @code{return},
@code{local} builtin. These variables are visible only to
the function and the commands it invokes.
+Function names and definitions may be listed with the
+@option{-f} option to the @code{declare} or @code{typeset}
+builtin commands (@pxref{Bash Builtins}).
+The @option{-F} option to @code{declare} or @code{typeset}
+will list the function names only
+(and optionally the source file and line number, if the @code{extdebug}
+shell option is enabled).
+Functions may be exported so that subshells
+automatically have them defined with the
+@option{-f} option to the @code{export} builtin
+(@pxref{Bourne Shell Builtins}).
+Note that shell functions and variables with the same name may result
+in multiple identically-named entries in the environment passed to the
+shell's children.
+Care should be taken in cases where this may cause a problem.
+
Functions may be recursive. No limit is placed on the number of
recursive calls.
@menu
* Positional Parameters:: The shell's command-line arguments.
-* Special Parameters:: Parameters with special meanings.
+* Special Parameters:: Parameters denoted by special characters.
@end menu
A @var{parameter} is an entity that stores values.
It can be a @code{name}, a number, or one of the special characters
listed below.
-For the shell's purposes, a @var{variable} is a parameter denoted by a
-@code{name}.
+A @var{variable} is a parameter denoted by a @code{name}.
A variable has a @var{value} and zero or more @var{attributes}.
Attributes are assigned using the @code{declare} builtin command
(see the description of the @code{declare} builtin in @ref{Bash Builtins}).
command substitution, arithmetic expansion, and quote
removal (detailed below). If the variable has its @code{integer}
attribute set, then @var{value}
-is subject to arithmetic expansion even if the @code{$((@dots{}))}
+is evaluated as an arithmetic expression even if the @code{$((@dots{}))}
expansion is not used (@pxref{Arithmetic Expansion}).
Word splitting is not performed, with the exception
of @code{"$@@"} as explained below.
Filename expansion is not performed.
Assignment statements may also appear as arguments to the
+@code{alias},
@code{declare}, @code{typeset}, @code{export}, @code{readonly},
and @code{local} builtin commands.
+In the context where an assignment statement is assigning a value
+to a shell variable or array index (@pxref{Arrays}), the @samp{+=}
+operator can be used to
+append to or add to the variable's previous value.
+When @samp{+=} is applied to a variable for which the integer attribute
+has been set, @var{value} is evaluated as an arithmetic expression and
+added to the variable's current value, which is also evaluated.
+When @samp{+=} is applied to an array variable using compound assignment
+(@pxref{Arrays}), the
+variable's value is not unset (as it is when using @samp{=}), and new
+values are appended to the array beginning at one greater than the array's
+maximum index (for indexed arrays), or added as additional key-value pairs
+in an associative array.
+When applied to a string-valued variable, @var{value} is expanded and
+appended to the variable's value.
+
@node Positional Parameters
@subsection Positional Parameters
@cindex parameters, positional
expansion occurs within double quotes, each parameter expands to a
separate word. That is, @code{"$@@"} is equivalent to
@code{"$1" "$2" @dots{}}.
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the original
+word, and the expansion of the last parameter is joined with the last
+part of the original word.
When there are no positional parameters, @code{"$@@"} and
@code{$@@}
expand to nothing (i.e., they are removed).
@item _
(An underscore.)
-At shell startup, set to the absolute filename of the shell or shell
-script being executed as passed in the argument list.
+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 of each command executed and placed in
-the environment exported to that command.
+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.
@end vtable
@var{filename expansion} (@pxref{Filename Expansion}),
but the file names generated need not exist.
Patterns to be brace expanded take the form of an optional @var{preamble},
-followed by a series of comma-separated strings between a pair of braces,
+followed by either a series of comma-separated strings or a seqeunce expression
+between a pair of braces,
followed by an optional @var{postscript}.
The preamble is prefixed to each string contained within the braces, and
the postscript is then appended to each resulting string, expanding left
ade ace abe
@end example
+A sequence expression takes the form @code{@{@var{x}..@var{y}[@var{incr}]@}},
+where @var{x} and @var{y} are either integers or single characters,
+and @var{incr}, an optional increment, is an integer.
+When integers are supplied, the expression expands to each number between
+@var{x} and @var{y}, inclusive.
+Supplied integers may be prefixed with @samp{0} to force each term to have the
+same width. When either @var{x} or @var{y} begins with a zero, the shell
+attempts to force all generated terms to contain the same number of digits,
+zero-padding where necessary.
+When characters are supplied, the expression expands to each character
+lexicographically between @var{x} and @var{y}, inclusive. Note that
+both @var{x} and @var{y} must be of the same type.
+When the increment is supplied, it is used as the difference between
+each term. The default increment is 1 or -1 as appropriate.
+
Brace expansion is performed before any other expansions,
and any characters special to other expansions are preserved
in the result. It is strictly textual. Bash
is not considered eligible for brace expansion.
A correctly-formed brace expansion must contain unquoted opening
-and closing braces, and at least one unquoted comma.
+and closing braces, and at least one unquoted comma or a valid
+sequence expression.
Any incorrectly formed brace expansion is left unchanged.
+A @{ or @samp{,} may be quoted with a backslash to prevent its
+being considered part of a brace expression.
+To avoid conflicts with parameter expansion, the string @samp{$@{}
+is not considered eligible for brace expansion.
+
This construct is typically used as shorthand when the common
prefix of the strings to be generated is longer than in the
above example:
left unchanged.
Each variable assignment is checked for unquoted tilde-prefixes immediately
-following a @samp{:} or @samp{=}.
+following a @samp{:} or the first @samp{=}.
In these cases, tilde expansion is also performed.
Consequently, one may use file names with tildes in assignments to
@env{PATH}, @env{MAILPATH}, and @env{CDPATH},
expanded and that value is used in the rest of the substitution, rather
than the value of @var{parameter} itself.
This is known as @code{indirect expansion}.
-The exception to this is the expansion of $@{!@var{prefix*@}}
+The exceptions to this are the expansions of $@{!@var{prefix*}@}
+and $@{!@var{name}[@@]@}
described below.
+The exclamation point must immediately follow the left brace in order to
+introduce indirection.
In each of the cases below, @var{word} is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
If @var{parameter}
is unset or null, the expansion of @var{word}
is assigned to @var{parameter}.
-The value of @var{parameter}
-is then substituted. Positional parameters and special parameters may
-not be assigned to in this way.
+The value of @var{parameter} is then substituted.
+Positional parameters and special parameters may not be assigned to
+in this way.
@item $@{@var{parameter}:?@var{word}@}
If @var{parameter}
is used as an offset from the end of the value of @var{parameter}.
If @var{parameter} is @samp{@@}, the result is @var{length} positional
parameters beginning at @var{offset}.
-If @var{parameter} is an array name indexed by @samp{@@} or @samp{*},
-the result is the @var{length}
+If @var{parameter} is an indexed array name subscripted
+by @samp{@@} or @samp{*}, the result is the @var{length}
members of the array beginning with @code{$@{@var{parameter}[@var{offset}]@}}.
+A negative @var{offset} is taken relative to one greater than the maximum
+index of the specified array.
+Substring expansion applied to an associative array produces undefined
+results.
+
+Note that a negative offset must be separated from the colon by at least
+one space to avoid being confused with the @samp{:-} expansion.
Substring indexing is zero-based unless the positional parameters
-are used, in which case the indexing starts at 1.
+are used, in which case the indexing starts at 1 by default.
+If @var{offset} is 0, and the positional parameters are used, @code{$@@} is
+prefixed to the list.
@item $@{!@var{prefix}*@}
+@itemx $@{!@var{prefix}@@@}
Expands to the names of variables whose names begin with @var{prefix},
separated by the first character of the @env{IFS} special variable.
+When @samp{@@} is used and the expansion appears within double quotes, each
+variable name expands to a separate word.
+
+@item $@{!@var{name}[@@]@}
+@itemx $@{!@var{name}[*]@}
+If @var{name} is an array variable, expands to the list of array indices
+(keys) assigned in @var{name}.
+If @var{name} is not an array, expands to 0 if @var{name} is set and null
+otherwise.
+When @samp{@@} is used and the expansion appears within double quotes, each
+key expands to a separate word.
@item $@{#@var{parameter}@}
The length in characters of the expanded value of @var{parameter} is
array in turn, and the expansion is the resultant list.
@item $@{@var{parameter}/@var{pattern}/@var{string}@}
-@itemx $@{@var{parameter}//@var{pattern}/@var{string}@}
The @var{pattern} is expanded to produce a pattern just as in
filename expansion.
@var{Parameter} is expanded and the longest match of @var{pattern}
against its value is replaced with @var{string}.
-In the first form, only the first match is replaced.
-The second form causes all matches of @var{pattern} to be
-replaced with @var{string}.
+If @var{pattern} begins with @samp{/}, all matches of @var{pattern} are
+replaced with @var{string}. Normally only the first match is replaced.
If @var{pattern} begins with @samp{#}, it must match at the beginning
of the expanded value of @var{parameter}.
If @var{pattern} begins with @samp{%}, it must match at the end
the substitution operation is applied to each member of the
array in turn, and the expansion is the resultant list.
+@item $@{@var{parameter}^@var{pattern}@}
+@itemx $@{@var{parameter}^^@var{pattern}@}
+@itemx $@{@var{parameter},@var{pattern}@}
+@itemx $@{@var{parameter},,@var{pattern}@}
+This expansion modifies the case of alphabetic characters in @var{parameter}.
+The @var{pattern} is expanded to produce a pattern just as in
+pathname expansion.
+The @samp{^} operator converts lowercase letters matching @var{pattern}
+to uppercase; the @samp{,} operator converts matching uppercase letters
+to lowercase.
+The @samp{^^} and @samp{,,} expansions convert each matched character in the
+expanded value; the @samp{^} and @samp{,} expansions match and convert only
+the first character.
+If @var{pattern} is omitted, it is treated like a @samp{?}, which matches
+every character.
+If @var{parameter} is @samp{@@} or @samp{*},
+the case modification operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If @var{parameter}
+is an array variable subscripted with @samp{@@} or @samp{*},
+the case modification operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+
@end table
@node Command Substitution
a double quote inside the parentheses is not treated specially.
All tokens in the expression undergo parameter expansion, command
substitution, and quote removal.
-Arithmetic substitutions may be nested.
+Arithmetic expansions may be nested.
The evaluation is performed according to the rules listed below
(@pxref{Shell Arithmetic}).
and arithmetic expansion that did not occur within double quotes for
word splitting.
-The shell treats each character of @env{$IFS}
-as a delimiter, and splits the results of the other
-expansions into words on these characters. If
-@env{IFS} is unset, or its value is exactly @code{<space><tab><newline>},
-the default, then any sequence of @env{IFS}
-characters serves to delimit words. If @env{IFS}
-has a value other than the default, then sequences of
+The shell treats each character of @env{$IFS} as a delimiter, and splits
+the results of the other expansions into words on these characters.
+If @env{IFS} is unset, or its value is exactly @code{<space><tab><newline>},
+the default, then sequences of
+@code{ <space>}, @code{<tab>}, and @code{<newline>}
+at the beginning and end of the results of the previous
+expansions are ignored, and any sequence of @env{IFS}
+characters not at the beginning or end serves to delimit words.
+If @env{IFS} has a value other than the default, then sequences of
the whitespace characters @code{space} and @code{tab}
are ignored at the beginning and end of the
word, as long as the whitespace character is in the
unchanged.
If the @code{nullglob} option is set, and no matches are found, the word
is removed.
+If the @code{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 @code{nocaseglob} is enabled, the match is performed
without regard to the case of alphabetic characters.
matched explicitly.
In other cases, the @samp{.} character is not treated specially.
-See the description of @code{shopt} in @ref{Bash Builtins},
+See the description of @code{shopt} in @ref{The Shopt Builtin},
for a description of the @code{nocaseglob}, @code{nullglob},
-and @code{dotglob} options.
+@code{failglob}, and @code{dotglob} options.
The @env{GLOBIGNORE}
shell variable may be used to restrict the set of filenames matching a
is set, each matching filename that also matches one of the patterns in
@env{GLOBIGNORE} is removed from the list of matches. The filenames
@file{.} and @file{..}
-are always ignored, even when @env{GLOBIGNORE}
-is set. However, setting @env{GLOBIGNORE} has the effect of
+are always ignored when @env{GLOBIGNORE}
+is set and not null.
+However, setting @env{GLOBIGNORE} to a non-null value has the effect of
enabling the @code{dotglob}
shell option, so all other filenames beginning with a
@samp{.} will match.
@cindex matching, pattern
Any character that appears in a pattern, other than the special pattern
-characters described below, matches itself. The @sc{nul} character may not
-occur in a pattern. The special pattern characters must be quoted if
-they are to be matched literally.
+characters described below, matches itself.
+The @sc{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:
@table @code
@item *
Matches any string, including the null string.
+When the @code{globstar} shell option is enabled, and @samp{*} is used in
+a filename expansion context, two adjacent @samp{*}s used as a single
+pattern will match all files and zero or more directories and
+subdirectories.
+If followed by a @samp{/}, two adjacent @samp{*}s will match only
+directories and subdirectories.
@item ?
Matches any single character.
@item [@dots{}]
Within @samp{[} and @samp{]}, @var{character classes} can be specified
using the syntax
@code{[:}@var{class}@code{:]}, where @var{class} is one of the
-following classes defined in the @sc{posix} 1003.2 standard:
+following classes defined in the @sc{posix} standard:
@example
alnum alpha ascii blank cntrl digit graph lower
-print punct space upper xdigit
+print punct space upper word xdigit
@end example
@noindent
A character class matches any character belonging to that class.
+The @code{word} character class matches letters, digits, and the character
+@samp{_}.
Within @samp{[} and @samp{]}, an @var{equivalence class} can be
specified using the syntax @code{[=}@var{c}@code{=]}, which
Matches one or more occurrences of the given patterns.
@item @@(@var{pattern-list})
-Matches exactly one of the given patterns.
+Matches one of the given patterns.
@item !(@var{pattern-list})
Matches anything except one of the given patterns.
A failure to open or create a file causes the redirection to fail.
+Redirections using file descriptors greater than 9 should be used with
+care, as they may conflict with file descriptors the shell uses
+internally.
+
@subsection Redirecting Input
Redirection of input causes the file whose name results from
the expansion of @var{word}
The general format for redirecting input is:
@example
-[n]<@var{word}
+[@var{n}]<@var{word}
@end example
@subsection Redirecting Output
Redirection of output causes the file whose name results from
the expansion of @var{word}
-to be opened for writing on file descriptor @code{n},
-or the standard output (file descriptor 1) if @code{n}
+to be opened for writing on file descriptor @var{n},
+or the standard output (file descriptor 1) if @var{n}
is not specified. If the file does not exist it is created;
if it does exist it is truncated to zero size.
The general format for redirecting output is:
@example
-[n]>[|]@var{word}
+[@var{n}]>[|]@var{word}
@end example
If the redirection operator is @samp{>}, and the @code{noclobber}
Redirection of output in this fashion
causes the file whose name results from
the expansion of @var{word}
-to be opened for appending on file descriptor @code{n},
-or the standard output (file descriptor 1) if @code{n}
+to be opened for appending on file descriptor @var{n},
+or the standard output (file descriptor 1) if @var{n}
is not specified. If the file does not exist it is created.
The general format for appending output is:
@example
-[n]>>@var{word}
+[@var{n}]>>@var{word}
@end example
@subsection Redirecting Standard Output and Standard Error
-Bash allows both the
+This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be redirected to the file whose name is the
-expansion of @var{word} with this construct.
+expansion of @var{word}.
There are two formats for redirecting standard output and
standard error:
>@var{word} 2>&1
@end example
+@subsection Appending Standard Output and Standard Error
+This construct allows both the
+standard output (file descriptor 1) and
+the standard error output (file descriptor 2)
+to be appended to the file whose name is the
+expansion of @var{word}.
+
+The format for appending standard output and standard error is:
+@example
+&>>@var{word}
+@end example
+@noindent
+This is semantically equivalent to
+@example
+>>@var{word} 2>&1
+@end example
+
@subsection Here Documents
This type of redirection instructs the shell to read input from the
current source until a line containing only @var{word}
the lines read up to that point are then used as the standard
input for a command.
-The format of here-documents is as follows:
+The format of here-documents is:
@example
<<[@minus{}]@var{word}
@var{here-document}
This allows here-documents within shell scripts to be indented in a
natural fashion.
+@subsection Here Strings
+A variant of here documents, the format is:
+@example
+<<< @var{word}
+@end example
+
+The @var{word} is expanded and supplied to the command on its standard
+input.
+
@subsection Duplicating File Descriptors
The redirection operator
@example
-[n]<&@var{word}
+[@var{n}]<&@var{word}
@end example
@noindent
is used to duplicate input file descriptors.
If @var{word}
-expands to one or more digits, the file descriptor denoted by @code{n}
+expands to one or more digits, the file descriptor denoted by @var{n}
is made to be a copy of that file descriptor.
If the digits in @var{word} do not specify a file descriptor open for
input, a redirection error occurs.
If @var{word}
-evaluates to @samp{-}, file descriptor @code{n} is closed. If
-@code{n} is not specified, the standard input (file descriptor 0) is used.
+evaluates to @samp{-}, file descriptor @var{n} is closed. If
+@var{n} is not specified, the standard input (file descriptor 0) is used.
The operator
@example
-[n]>&@var{word}
+[@var{n}]>&@var{word}
@end example
@noindent
is used similarly to duplicate output file descriptors. If
-@code{n}
-is not specified, the standard output (file descriptor 1) is used.
+@var{n} is not specified, the standard output (file descriptor 1) is used.
If the digits in @var{word} do not specify a file descriptor open for
output, a redirection error occurs.
-As a special case, if @code{n} is omitted, and @var{word} does not
+As a special case, if @var{n} is omitted, and @var{word} does not
expand to one or more digits, the standard output and standard
error are redirected as described previously.
+@subsection Moving File Descriptors
+The redirection operator
+@example
+[@var{n}]<&@var{digit}-
+@end example
+@noindent
+moves the file descriptor @var{digit} to file descriptor @var{n},
+or the standard input (file descriptor 0) if @var{n} is not specified.
+@var{digit} is closed after being duplicated to @var{n}.
+
+Similarly, the redirection operator
+@example
+[@var{n}]>&@var{digit}-
+@end example
+@noindent
+moves the file descriptor @var{digit} to file descriptor @var{n},
+or the standard output (file descriptor 1) if @var{n} is not specified.
+
@subsection Opening File Descriptors for Reading and Writing
The redirection operator
@example
-[n]<>@var{word}
+[@var{n}]<>@var{word}
@end example
@noindent
causes the file whose name is the expansion of @var{word}
to be opened for both reading and writing on file descriptor
-@code{n}, or on file descriptor 0 if @code{n}
+@var{n}, or on file descriptor 0 if @var{n}
is not specified. If the file does not exist, it is created.
@node 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.
-
@end menu
@node Simple Command Expansion
(see the description of @code{hash} in @ref{Bourne Shell Builtins}).
A full search of the directories in @env{$PATH}
is performed only if the command is not found in the hash table.
-If the search is unsuccessful, the shell prints an error
+If the search is unsuccessful, the shell searches for a defined shell
+function named @code{command_not_found_handle}.
+If that function exists, it is invoked with the original command and
+the original command's arguments as its arguments, and the function's
+exit status becomes the exit status of the shell.
+If that function is not defined, the shell prints an error
message and returns an exit status of 127.
@item
arguments) or by @code{set}
@item
-options enabled by @code{shopt}
+options enabled by @code{shopt} (@pxref{The Shopt Builtin})
@item
shell aliases defined with @code{alias} (@pxref{Aliases})
the file creation mode mask
@item
-shell variables marked for export, along with variables exported for
-the command, passed in the environment (@pxref{Environment})
+shell variables and functions marked for export, along with variables
+exported for the command, passed in the environment (@pxref{Environment})
@item
traps caught by the shell are reset to the values inherited from the
A command invoked in this separate environment cannot affect the
shell's execution environment.
-Command substitution and asynchronous commands are invoked in a
+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
in a subshell environment. Changes made to the subshell environment
cannot affect the shell's execution environment.
+Subshells spawned to execute command substitutions inherit the value of
+the @option{-e} option from the parent shell. When not in @sc{posix} mode,
+Bash clears the @option{-e} option in such subshells.
+
If a command is followed by a @samp{&} and job control is not active, the
default standard input for the command is the empty file @file{/dev/null}.
Otherwise, the invoked command inherits the file descriptors of the calling
@subsection Exit Status
@cindex exit status
+The exit status of an executed command is the value returned by the
+@var{waitpid} system call or equivalent function. Exit statuses
+fall between 0 and 255, though, as explained below, the shell may
+use values above 125 specially. Exit statuses from shell builtins and
+compound commands are also limited to this range. Under certain
+circumstances, the shell will use special values to indicate specific
+failure modes.
+
For the shell's purposes, a command which exits with a
zero exit status has succeeded.
A non-zero exit status indicates failure.
If job control is in effect (@pxref{Job Control}), Bash
ignores @code{SIGTTIN}, @code{SIGTTOU}, and @code{SIGTSTP}.
-Commands started by Bash have signal handlers set to the
+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 @code{SIGINT} and @code{SIGQUIT} as well.
+ignore @code{SIGINT} and @code{SIGQUIT} in addition to these inherited
+handlers.
Commands run as a result of
command substitution ignore the keyboard-generated job control signals
@code{SIGTTIN}, @code{SIGTTOU}, and @code{SIGTSTP}.
to not receive @code{SIGHUP} using @code{disown -h}.
If the @code{huponexit} shell option has been set with @code{shopt}
-(@pxref{Bash Builtins}), Bash sends a @code{SIGHUP} to all jobs when
+(@pxref{The Shopt Builtin}), Bash sends a @code{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.
+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 @code{wait} builtin, the reception of a signal for
which a trap has been set will cause the @code{wait} builtin to return
* 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.
@end menu
Builtin commands are contained within the shell itself.
Builtin commands are necessary to implement functionality impossible
or inconvenient to obtain with separate utilities.
-This section briefly the builtins which Bash inherits from
+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.
Many of the builtins have been extended by @sc{posix} or Bash.
+Unless otherwise noted, each builtin command documented as accepting
+options preceded by @samp{-} accepts @samp{--}
+to signify the end of the options.
+For example, the @code{:}, @code{true}, @code{false}, and @code{test}
+builtins do not accept options.
+
@node Bourne Shell Builtins
@section Bourne Shell Builtins
The following shell builtin commands are inherited from the Bourne Shell.
-These commands are implemented as specified by the @sc{posix} 1003.2 standard.
+These commands are implemented as specified by the @sc{posix} standard.
@table @code
@item : @r{(a colon)}
@item cd
@btindex cd
@example
-cd [-LP] [@var{directory}]
+cd [-L|-P] [@var{directory}]
@end example
-Change the current working directory to @var{directory}. If @var{directory}
-is not given, the value of the @env{HOME} shell variable is used. If the
-shell variable @env{CDPATH} exists, it is used as a search path. If
-@var{directory} begins with a slash, @env{CDPATH} is not used.
-The @option{-P} option means
-to not follow symbolic links; symbolic links are followed by default
-or with the @option{-L} option.
+Change the current working directory to @var{directory}.
+If @var{directory} is not given, the value of the @env{HOME} shell
+variable is used.
+If the shell variable @env{CDPATH} exists, it is used as a search path.
+If @var{directory} begins with a slash, @env{CDPATH} is not used.
+
+The @option{-P} option means to not follow symbolic links; symbolic
+links are followed by default or with the @option{-L} option.
If @var{directory} is @samp{-}, it is equivalent to @env{$OLDPWD}.
+
+If a non-empty directory name from @env{CDPATH} is used, or if
+@samp{-} is the first argument, and the directory change is
+successful, the absolute pathname of the new working directory is
+written to the standard output.
+
The return status is zero if the directory is successfully changed,
non-zero otherwise.
If @var{command}
is supplied, it replaces the shell without creating a new process.
If the @option{-l} option is supplied, the shell places a dash at the
-beginning of the zeroth arg passed to @var{command}.
+beginning of the zeroth argument passed to @var{command}.
This is what the @code{login} program does.
The @option{-c} option causes @var{command} to be executed with an empty
environment.
If no @var{names} are supplied, or if the @option{-p} option is given, a
list of exported names is displayed.
The @option{-p} option displays output in a form that may be reused as input.
+If a variable name is followed by =@var{value}, the value of
+the variable is set to @var{value}.
+
The return status is zero unless an invalid option is supplied, one of
the names is not a valid shell variable name, or @option{-f} is supplied
with a name that is not a shell function.
@item hash
@btindex hash
@example
-hash [-r] [-p @var{filename}] [-t] [@var{name}]
+hash [-r] [-p @var{filename}] [-dt] [@var{name}]
@end example
Remember the full pathnames of commands specified as @var{name} arguments,
so they need not be searched for on subsequent invocations.
The @option{-p} option inhibits the path search, and @var{filename} is
used as the location of @var{name}.
The @option{-r} option causes the shell to forget all remembered locations.
+The @option{-d} option causes the shell to forget the remembered location
+of each @var{name}.
If the @option{-t} option is supplied, the full pathname to which each
@var{name} corresponds is printed. If multiple @var{name} arguments are
supplied with @option{-t} the @var{name} is printed before the hashed
full pathname.
-If no arguments are given, information about remembered commands is printed.
+The @option{-l} option causes output to be displayed in a format
+that may be reused as input.
+If no arguments are given, or if only @option{-l} is supplied,
+information about remembered commands is printed.
The return status is zero unless a @var{name} is not found or an invalid
option is supplied.
@item readonly
@btindex readonly
@example
-readonly [-apf] [@var{name}] @dots{}
+readonly [-aApf] [@var{name}[=@var{value}]] @dots{}
@end example
Mark each @var{name} as readonly.
The values of these names may not be changed by subsequent assignment.
If the @option{-f} option is supplied, each @var{name} refers to a shell
function.
-The @option{-a} option means each @var{name} refers to an array variable.
+The @option{-a} option means each @var{name} refers to an indexed
+array variable; the @option{-A} option means each @var{name} refers
+to an associative array variable.
If no @var{name} arguments are given, or if the @option{-p}
option is supplied, a list of all readonly names is printed.
The @option{-p} option causes output to be displayed in a format that
may be reused as input.
+If a variable name is followed by =@var{value}, the value of
+the variable is set to @var{value}.
The return status is zero unless an invalid option is supplied, one of
the @var{name} arguments is not a valid shell variable or function name,
or the @option{-f} option is supplied with a name that is not a shell function.
with the @code{.} (or @code{source}) builtin, returning either @var{n} or
the exit status of the last command executed within the script as the exit
status of the script.
+Any command associated with the @code{RETURN} trap is executed
+before execution resumes after the function or script.
The return status is non-zero if @code{return} is used outside a function
and not during the execution of a script by @code{.} or @code{source}.
@end example
Shift the positional parameters to the left by @var{n}.
The positional parameters from @var{n}+1 @dots{} @code{$#} are
-renamed to @code{$1} @dots{} @code{$#}-@var{n}+1.
-Parameters represented by the numbers @code{$#} to @var{n}+1 are unset.
+renamed to @code{$1} @dots{} @code{$#}-@var{n}.
+Parameters represented by the numbers @code{$#} to @code{$#}-@var{n}+1
+are unset.
@var{n} must be a non-negative number less than or equal to @code{$#}.
If @var{n} is zero or greater than @code{$#}, the positional parameters
are not changed.
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described below in
@ref{Bash Conditional Expressions}.
+@code{test} does not accept any options, nor does it accept and ignore
+an argument of @option{--} as signifying the end of options.
When the @code{[} form is used, the last argument to the command must
be a @code{]}.
Expressions may be combined using the following operators, listed in
decreasing order of precedence.
+The evaluation depends on the number of arguments; see below.
@table @code
@item ! @var{expr}
operators (@pxref{Bash Conditional Expressions}), the
result of the expression is the result of the binary test using the
first and third arguments as operands.
+The @samp{-a} and @samp{-o} operators are considered binary operators
+when there are three arguments.
If the first argument is @samp{!}, the value is the negation of
the two-argument test using the second and third arguments.
If the first argument is exactly @samp{(} and the third argument is
exactly @samp{)}, the result is the one-argument test of the second
argument.
Otherwise, the expression is false.
-The @samp{-a} and @samp{-o} operators are considered binary operators
-in this case.
@item 4 arguments
If the first argument is @samp{!}, the result is the negation of
trap [-lp] [@var{arg}] [@var{sigspec} @dots{}]
@end example
The commands in @var{arg} are to be read and executed when the
-shell receives signal @var{sigspec}. If @var{arg} is absent or
-equal to @samp{-}, all specified signals are reset to the values
-they had when the shell was started.
+shell receives signal @var{sigspec}. If @var{arg} is absent (and
+there is a single @var{sigspec}) or
+equal to @samp{-}, each specified signal's disposition is reset
+to the value it had when the shell was started.
If @var{arg} is the null string, then the signal specified by
each @var{sigspec} is ignored by the shell and commands it invokes.
If @var{arg} is not present and @option{-p} has been supplied,
only @option{-p} is given, @code{trap} prints the list of commands
associated with each signal number in a form that may be reused as
shell input.
-Each @var{sigspec} is either a signal name such as @code{SIGINT} (with
-or without the @code{SIG} prefix) or a signal number.
+The @option{-l} option causes the shell to print a list of signal names
+and their corresponding numbers.
+Each @var{sigspec} is either a signal name or a signal number.
+Signal names are case insensitive and the @code{SIG} prefix is optional.
If a @var{sigspec}
is @code{0} or @code{EXIT}, @var{arg} is executed when the shell exits.
If a @var{sigspec} is @code{DEBUG}, the command @var{arg} is executed
-after every simple command.
+before every simple command, @code{for} command, @code{case} command,
+@code{select} command, every arithmetic @code{for} command, and before
+the first command executes in a shell function.
+Refer to the description of the @code{extglob} option to the
+@code{shopt} builtin (@pxref{The Shopt Builtin}) for details of its
+effect on the @code{DEBUG} trap.
If a @var{sigspec} is @code{ERR}, the command @var{arg}
-is executed whenever a simple command has a non-zero exit status.
-The @code{ERR} trap is not executed if the failed command is part of an
-@code{until} or @code{while} loop, part of an @code{if} statement,
-part of a @code{&&} or @code{||} list, or if the command's return
+is executed whenever a simple command has a non-zero exit status,
+subject to the following conditions.
+The @code{ERR} trap is not executed if the failed command is part of the
+command list immediately following an @code{until} or @code{while} keyword,
+part of the test in an @code{if} statement,
+part of a command executed in a @code{&&} or @code{||} list,
+or if the command's return
status is being inverted using @code{!}.
-The @option{-l} option causes the shell to print a list of signal names
-and their corresponding numbers.
+These are the same conditions obeyed by the @code{errexit} option.
+If a @var{sigspec} is @code{RETURN}, the command @var{arg} is executed
+each time a shell function or a script executed with the @code{.} or
+@code{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 @var{sigspec} does not specify a
valid signal.
If the @option{-f} option is given, the @var{name}s refer to shell
functions, and the function definition is removed.
Readonly variables and functions may not be unset.
-The return status is zero unless a @var{name} does not exist or is
-readonly.
+The return status is zero unless a @var{name} is readonly.
@end table
@node Bash Builtins
This section describes builtin commands which are unique to
or have been extended in Bash.
-Some of these commands are specified in the @sc{posix} 1003.2 standard.
+Some of these commands are specified in the @sc{posix} standard.
@table @code
bind [-m @var{keymap}] -f @var{filename}
bind [-m @var{keymap}] -x @var{keyseq:shell-command}
bind [-m @var{keymap}] @var{keyseq:function-name}
+bind @var{readline-command}
@end example
Display current Readline (@pxref{Command Line Editing})
-key and function bindings, or
-bind a key sequence to a Readline function or macro. The
-binding syntax accepted is identical to that of
-a Readline initialization file (@pxref{Readline Init File}),
-but each binding must be passed as a separate argument: e.g.,
+key and function bindings,
+bind a key sequence to a Readline function or macro,
+or set a Readline variable.
+Each non-option argument is a command as it would appear in a
+Readline initialization file (@pxref{Readline Init File}),
+but each binding or command must be passed as a separate argument; e.g.,
@samp{"\C-x\C-r":re-read-init-file}.
+
Options, if supplied, have the following meanings:
@table @code
@item -x @var{keyseq:shell-command}
Cause @var{shell-command} to be executed whenever @var{keyseq} is
entered.
-
+When @var{shell-command} is executed, the shell sets the
+@code{READLINE_LINE} variable to the contents of the Readline line
+buffer and the @code{READLINE_POINT} variable to the current location
+of the insertion point.
+If the executed command changes the value of @code{READLINE_LINE} or
+@code{READLINE_POINT}, those new values will be reflected in the
+editing state.
@end table
@noindent
The return status is non-zero if @var{shell-builtin} is not a shell
builtin command.
+@item caller
+@btindex caller
+@example
+caller [@var{expr}]
+@end example
+Returns the context of any active subroutine call (a shell function or
+a script executed with the @code{.} or @code{source} builtins).
+
+Without @var{expr}, @code{caller} displays the line number and source
+filename of the current subroutine call.
+If a non-negative integer is supplied as @var{expr}, @code{caller}
+displays the line number, subroutine name, and source file corresponding
+to that position in the current execution call stack. This extra
+information may be used, for example, to print a stack trace. The
+current frame is frame 0.
+
+The return value is 0 unless the shell is not executing a subroutine
+call or @var{expr} does not correspond to a valid position in the
+call stack.
+
@item command
@btindex command
@example
@item declare
@btindex declare
@example
-declare [-afFrxi] [-p] [@var{name}[=@var{value}]]
+declare [-aAfFilrtux] [-p] [@var{name}[=@var{value}] @dots{}]
@end example
Declare variables and give them attributes. If no @var{name}s
are given, then display the values of variables instead.
The @option{-p} option will display the attributes and values of each
-@var{name}. When @option{-p} is used, additional options are ignored.
+@var{name}.
+When @option{-p} is used with @var{name} arguments, additional options
+are ignored.
+
+When @option{-p} is supplied without @var{name} arguments, @code{declare}
+will display the attributes and values of all variables having the
+attributes specified by the additional options.
+If no other options are supplied with @option{-p}, @code{declare} will
+display the attributes and values of all shell variables. The @option{-f}
+option will restrict the display to shell functions.
+
The @option{-F} option inhibits the display of function definitions;
-only the function name and attributes are printed. @option{-F} implies
-@option{-f}. The following options can be used to restrict output
-to variables with the specified attributes or to give variables
-attributes:
+only the function name and attributes are printed.
+If the @code{extdebug} shell option is enabled using @code{shopt}
+(@pxref{The Shopt Builtin}), the source file name and line number where
+the function is defined are displayed as well.
+@option{-F} implies @option{-f}.
+The following options can be used to restrict output to variables with
+the specified attributes or to give variables attributes:
@table @code
@item -a
-Each @var{name} is an array variable (@pxref{Arrays}).
+Each @var{name} is an indexed array variable (@pxref{Arrays}).
+
+@item -A
+Each @var{name} is an associative array variable (@pxref{Arrays}).
@item -f
Use function names only.
an integer; arithmetic evaluation (@pxref{Shell Arithmetic}) is
performed when the variable is assigned a value.
+@item -l
+When the variable is assigned a value, all upper-case characters are
+converted to lower-case.
+The upper-case attribute is disabled.
+
@item -r
Make @var{name}s readonly. These names cannot then be assigned values
by subsequent assignment statements or unset.
+@item -t
+Give each @var{name} the @code{trace} attribute.
+Traced functions inherit the @code{DEBUG} and @code{RETURN} traps from
+the calling shell.
+The trace attribute has no special meaning for variables.
+
+@item -u
+When the variable is assigned a value, all lower-case characters are
+converted to upper-case.
+The lower-case attribute is disabled.
+
@item -x
Mark each @var{name} for export to subsequent commands via
the environment.
@end table
-Using @samp{+} instead of @samp{-} turns off the attribute instead.
+Using @samp{+} instead of @samp{-} turns off the attribute instead,
+with the exceptions that @samp{+a}
+may not be used to destroy an array variable and @samp{+r} will not
+remove the readonly attribute.
When used in a function, @code{declare} makes each @var{name} local,
-as with the @code{local} command.
+as with the @code{local} command. If a variable name is followed by
+=@var{value}, the value of the variable is set to @var{value}.
The return status is zero unless an invalid option is encountered,
an attempt is made to define a function using @samp{-f foo=bar},
The @code{xpg_echo} shell option may be used to
dynamically determine whether or not @code{echo} expands these
escape characters by default.
+@code{echo} does not interpret @option{--} to mean the end of options.
+
@code{echo} interprets the following escape sequences:
@table @code
@item \a
@item \b
backspace
@item \c
-suppress trailing newline
+suppress further output
@item \e
escape
@item \f
vertical tab
@item \\
backslash
-@item \@var{nnn}
+@item \0@var{nnn}
the eight-bit character whose value is the octal value @var{nnn}
-(one to three digits)
+(zero to three octal digits)
@item \x@var{HH}
the eight-bit character whose value is the hexadecimal value @var{HH}
(one or two hex digits)
@item enable
@btindex enable
@example
-enable [-n] [-p] [-f @var{filename}] [-ads] [@var{name} @dots{}]
+enable [-a] [-dnps] [-f @var{filename}] [@var{name} @dots{}]
@end example
Enable and disable builtin shell commands.
Disabling a builtin allows a disk command which has the same name
@item help
@btindex help
@example
-help [-s] [@var{pattern}]
+help [-dms] [@var{pattern}]
@end example
Display helpful information about builtin commands.
If @var{pattern} is specified, @code{help} gives detailed help
on all commands matching @var{pattern}, otherwise a list of
the builtins is printed.
-The @option{-s} option restricts the information displayed to a short
-usage synopsis.
+
+Options, if supplied, have the following meanings:
+
+@table @code
+@item -d
+Display a short description of each @var{pattern}
+@item -m
+Display the description of each @var{pattern} in a manpage-like format
+@item -s
+Display only a short usage synopsis for each @var{pattern}
+@end table
+
The return status is zero unless no command matches @var{pattern}.
@item let
@item local
@btindex local
@example
-local [@var{option}] @var{name}[=@var{value}]
+local [@var{option}] @var{name}[=@var{value}] @dots{}
@end example
For each argument, a local variable named @var{name} is created,
and assigned @var{value}.
Exit a login shell, returning a status of @var{n} to the shell's
parent.
+@item mapfile
+@btindex mapfile
+@example
+mapfile [-n @var{count}] [-O @var{origin}] [-s @var{count}] [-t] [-u @var{fd}] [
+-C @var{callback}] [-c @var{quantum}] [@var{array}]
+@end example
+Read lines from the standard input into array variable @var{array},
+or from file descriptor @var{fd}
+if the @option{-u} option is supplied.
+The variable @code{MAPFILE} is the default @var{array}.
+Options, if supplied, have the following meanings:
+@table @code
+
+@item -n
+Copy at most @var{count} lines. If @var{count} is 0, all lines are copied.
+@item -O
+Begin assigning to @var{array} at index @var{origin}.
+The default index is 0.
+@item -s
+Discard the first @var{count} lines read.
+@item -t
+Remove a trailing line from each line read.
+@item -u
+Read lines from file descriptor @var{fd} instead of the standard input.
+@item -C
+Evaluate @var{callback} each time @var{quantum}P lines are read.
+The @option{-c} option specifies @var{quantum}.
+@item -c
+Specify the number of lines read between each call to @var{callback}.
+@end table
+
+If @option{-C} is specified without @option{-c},
+the default quantum is 5000.
+
+If not supplied with an explicit origin, @code{mapfile} will clear @var{array}
+before assigning to it.
+
+@code{mapfile} returns successfully unless an invalid option or option
+argument is supplied, or @var{array} is invalid or unassignable.
+
@item printf
@btindex printf
@example
-@code{printf} @var{format} [@var{arguments}]
+printf [-v @var{var}] @var{format} [@var{arguments}]
@end example
Write the formatted @var{arguments} to the standard output under the
control of the @var{format}.
@var{argument}.
In addition to the standard @code{printf(1)} formats, @samp{%b} causes
@code{printf} to expand backslash escape sequences in the corresponding
-@var{argument}, and @samp{%q} causes @code{printf} to output the
+@var{argument},
+(except that @samp{\c} terminates output, backslashes in
+@samp{\'}, @samp{\"}, and @samp{\?} are not removed, and octal escapes
+beginning with @samp{\0} may contain up to four digits),
+and @samp{%q} causes @code{printf} to output the
corresponding @var{argument} in a format that can be reused as shell input.
+The @option{-v} option causes the output to be assigned to the variable
+@var{var} rather than being printed to the standard output.
+
The @var{format} is reused as necessary to consume all of the @var{arguments}.
If the @var{format} requires more @var{arguments} than are supplied, the
extra format specifications behave as if a zero value or null string, as
@item read
@btindex read
@example
-read [-ers] [-a @var{aname}] [-p @var{prompt}] [-t @var{timeout}] [-n @var{nchars}] [-d @var{delim}] [@var{name} @dots{}]
+read [-ers] [-a @var{aname}] [-d @var{delim}] [-i @var{text}] [-n @var{nchars}] [-p @var{prompt}] [-t @var{timeout}] [-u @var{fd}] [@var{name} @dots{}]
@end example
-One line is read from the standard input, and the first word
+One line is read from the standard input, or from the file descriptor
+@var{fd} supplied as an argument to the @option{-u} option, and the first word
is assigned to the first @var{name}, the second word to the second @var{name},
and so on, with leftover words and their intervening separators assigned
to the last @var{name}.
-If there are fewer words read from the standard input than names,
+If there are fewer words read from the input stream than names,
the remaining names are assigned empty values.
The characters in the value of the @env{IFS} variable
are used to split the line into words.
meaning for the next character read and for line continuation.
If no names are supplied, the line read is assigned to the
variable @env{REPLY}.
-The return code is zero, unless end-of-file is encountered or @code{read}
-times out.
+The return code is zero, unless end-of-file is encountered, @code{read}
+times out (in which case the return code is greater than 128), or an
+invalid file descriptor is supplied as the argument to @option{-u}.
+
Options, if supplied, have the following meanings:
@table @code
@item -e
Readline (@pxref{Command Line Editing}) is used to obtain the line.
+Readline uses the current (or default, if line editing was not previously
+active) editing settings.
+
+@item -i @var{text}
+If Readline is being used to read the line, @var{text} is placed into
+the editing buffer before editing begins.
@item -n @var{nchars}
@code{read} returns after reading @var{nchars} characters rather than
@item -t @var{timeout}
Cause @code{read} to time out and return failure if a complete line of
input is not read within @var{timeout} seconds.
-This option has no effect if @code{read} is not reading input from the
-terminal or a pipe.
+@var{timeout} may be a decimal number with a fractional portion following
+the decimal point.
+This option is only effective if @code{read} is reading input from a
+terminal, pipe, or other special file; it has no effect when reading
+from regular files.
+If @var{timeout} is 0, @code{read} returns success if input is available on
+the specified file descriptor, failure otherwise.
+The exit status is greater than 128 if the timeout is exceeded.
+
+@item -u @var{fd}
+Read input from file descriptor @var{fd}.
@end table
-@item shopt
-@btindex shopt
+@item source
+@btindex source
@example
-shopt [-pqsu] [-o] [@var{optname} @dots{}]
+source @var{filename}
@end example
-Toggle the values of variables controlling optional shell behavior.
-With no options, or with the @option{-p} option, a list of all settable
-options is displayed, with an indication of whether or not each is set.
-The @option{-p} option causes output to be displayed in a form that
-may be reused as input.
-Other options have the following meanings:
+A synonym for @code{.} (@pxref{Bourne Shell Builtins}).
-@table @code
-@item -s
-Enable (set) each @var{optname}.
+@item type
+@btindex type
+@example
+type [-afptP] [@var{name} @dots{}]
+@end example
+For each @var{name}, indicate how it would be interpreted if used as a
+command name.
-@item -u
-Disable (unset) each @var{optname}.
+If the @option{-t} option is used, @code{type} prints a single word
+which is one of @samp{alias}, @samp{function}, @samp{builtin},
+@samp{file} or @samp{keyword},
+if @var{name} is an alias, shell function, shell builtin,
+disk file, or shell reserved word, respectively.
+If the @var{name} is not found, then nothing is printed, and
+@code{type} returns a failure status.
-@item -q
-Suppresses normal output; the return status
-indicates whether the @var{optname} is set or unset.
-If multiple @var{optname} arguments are given with @option{-q},
-the return status is zero if all @var{optnames} are enabled;
-non-zero otherwise.
+If the @option{-p} option is used, @code{type} either returns the name
+of the disk file that would be executed, or nothing if @option{-t}
+would not return @samp{file}.
-@item -o
-Restricts the values of
-@var{optname} to be those defined for the @option{-o} option to the
-@code{set} builtin (@pxref{The Set Builtin}).
-@end table
+The @option{-P} option forces a path search for each @var{name}, even if
+@option{-t} would not return @samp{file}.
-If either @option{-s} or @option{-u}
-is used with no @var{optname} arguments, the display is limited to
-those options which are set or unset, respectively.
+If a command is hashed, @option{-p} and @option{-P} print the hashed value,
+not necessarily the file that appears first in @code{$PATH}.
-Unless otherwise noted, the @code{shopt} options are disabled (off)
-by default.
+If the @option{-a} option is used, @code{type} returns all of the places
+that contain an executable named @var{file}.
+This includes aliases and functions, if and only if the @option{-p} option
+is not also used.
-The return status when listing options is zero if all @var{optnames}
-are enabled, non-zero otherwise. When setting or unsetting options,
-the return status is zero unless an @var{optname} is not a valid shell
-option.
-
-The list of @code{shopt} options is:
-@table @code
-@item cdable_vars
-If this is set, an argument to the @code{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.
-
-@item cdspell
-If set, minor errors in the spelling of a directory component in a
-@code{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.
-
-@item 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.
-
-@item checkwinsize
-If set, Bash checks the window size after each command
-and, if necessary, updates the values of
-@env{LINES} and @env{COLUMNS}.
-
-@item 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.
-
-@item dotglob
-If set, Bash includes filenames beginning with a `.' in
-the results of filename expansion.
-
-@item execfail
-If this is set, a non-interactive shell will not exit if
-it cannot execute the file specified as an argument to the @code{exec}
-builtin command. An interactive shell does not exit if @code{exec}
-fails.
-
-@item expand_aliases
-If set, aliases are expanded as described below under Aliases,
-@ref{Aliases}.
-This option is enabled by default for interactive shells.
-
-@item extglob
-If set, the extended pattern matching features described above
-(@pxref{Pattern Matching}) are enabled.
-
-@item histappend
-If set, the history list is appended to the file named by the value
-of the @env{HISTFILE}
-variable when the shell exits, rather than overwriting the file.
+If the @option{-f} option is used, @code{type} does not attempt to find
+shell functions, as with the @code{command} builtin.
-@item histreedit
-If set, and Readline
-is being used, a user is given the opportunity to re-edit a
-failed history substitution.
-
-@item 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.
-
-@item hostcomplete
-If set, and Readline is being used, Bash will attempt to perform
-hostname completion when a word containing a @samp{@@} is being
-completed (@pxref{Commands For Completion}). This option is enabled
-by default.
-
-@item huponexit
-If set, Bash will send @code{SIGHUP} to all jobs when an interactive
-login shell exits (@pxref{Signals}).
-
-@item interactive_comments
-Allow a word beginning with @samp{#}
-to cause that word and all remaining characters on that
-line to be ignored in an interactive shell.
-This option is enabled by default.
-
-@item lithist
-If enabled, and the @code{cmdhist}
-option is enabled, multi-line commands are saved to the history with
-embedded newlines rather than using semicolon separators where possible.
-
-@item login_shell
-The shell sets this option if it is started as a login shell
-(@pxref{Invoking Bash}).
-The value may not be changed.
-
-@item mailwarn
-If set, and a file that Bash is checking for mail has been
-accessed since the last time it was checked, the message
-@code{"The mail in @var{mailfile} has been read"} is displayed.
-
-@item no_empty_cmd_completion
-If set, and Readline is being used, Bash will not attempt to search
-the @env{PATH} for possible completions when completion is attempted
-on an empty line.
-
-@item nocaseglob
-If set, Bash matches filenames in a case-insensitive fashion when
-performing filename expansion.
-
-@item nullglob
-If set, Bash allows filename patterns which match no
-files to expand to a null string, rather than themselves.
-
-@item progcomp
-If set, the programmable completion facilities
-(@pxref{Programmable Completion}) are enabled.
-This option is enabled by default.
-
-@item promptvars
-If set, prompt strings undergo variable and parameter expansion after
-being expanded (@pxref{Printing a Prompt}).
-This option is enabled by default.
-
-@item restricted_shell
-The shell sets this option if it is started in restricted mode
-(@pxref{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.
-
-@item shift_verbose
-If this is set, the @code{shift}
-builtin prints an error message when the shift count exceeds the
-number of positional parameters.
-
-@item sourcepath
-If set, the @code{source} builtin uses the value of @env{PATH}
-to find the directory containing the file supplied as an argument.
-This option is enabled by default.
-
-@item xpg_echo
-If set, the @code{echo} builtin expands backslash-escape sequences
-by default.
-
-@end table
-
-@noindent
-The return status when listing options is zero if all @var{optnames}
-are enabled, non-zero otherwise.
-When setting or unsetting options, the return status is zero unless an
-@var{optname} is not a valid shell option.
-
-@item source
-@btindex source
-@example
-source @var{filename}
-@end example
-A synonym for @code{.} (@pxref{Bourne Shell Builtins}).
-
-@item type
-@btindex type
-@example
-type [-atp] [@var{name} @dots{}]
-@end example
-For each @var{name}, indicate how it would be interpreted if used as a
-command name.
-
-If the @option{-t} option is used, @code{type} prints a single word
-which is one of @samp{alias}, @samp{function}, @samp{builtin},
-@samp{file} or @samp{keyword},
-if @var{name} is an alias, shell function, shell builtin,
-disk file, or shell reserved word, respectively.
-If the @var{name} is not found, then nothing is printed, and
-@code{type} returns a failure status.
-
-If the @option{-p} option is used, @code{type} either returns the name
-of the disk file that would be executed, or nothing if @option{-t}
-would not return @samp{file}.
-
-If the @option{-a} option is used, @code{type} returns all of the places
-that contain an executable named @var{file}.
-This includes aliases and functions, if and only if the @option{-p} option
-is not also used.
-
-The return status is zero if any of the @var{names} are found, non-zero
-if none are found.
+The return status is zero if all of the @var{names} are found, non-zero
+if any are not found.
@item typeset
@btindex typeset
@example
-typeset [-afFrxi] [-p] [@var{name}[=@var{value}]]
+typeset [-afFrxi] [-p] [@var{name}[=@var{value}] @dots{}]
@end example
The @code{typeset} command is supplied for compatibility with the Korn
shell; however, it has been deprecated in favor of the @code{declare}
@item ulimit
@btindex ulimit
@example
-ulimit [-acdflmnpstuvSH] [@var{limit}]
+ulimit [-abcdefilmnpqrstuvxHST] [@var{limit}]
@end example
@code{ulimit} provides control over the resources available to processes
started by the shell, on systems that allow such control. If an
@item -a
All current limits are reported.
+@item -b
+The maximum socket buffer size.
+
@item -c
The maximum size of core files created.
@item -d
The maximum size of a process's data segment.
+@item -e
+The maximum scheduling priority ("nice").
+
@item -f
-The maximum size of files created by the shell.
+The maximum size of files written by the shell and its children.
+
+@item -i
+The maximum number of pending signals.
@item -l
The maximum size that may be locked into memory.
@item -p
The pipe buffer size.
+@item -q
+The maximum number of bytes in POSIX message queues.
+
+@item -r
+The maximum real-time scheduling priority.
+
@item -s
The maximum stack size.
@item -v
The maximum amount of virtual memory available to the process.
+@item -x
+The maximum number of file locks.
+
+@item -T
+The maximum number of threads.
+
@end table
If @var{limit} is given, it is the new value of the specified resource;
the special @var{limit} values @code{hard}, @code{soft}, and
@code{unlimited} stand for the current hard limit, the current soft limit,
and no limit, respectively.
+A hard limit cannot be increased by a non-root user once it is set;
+a soft limit may be increased up to the value of the hard limit.
Otherwise, the current value of the soft limit for the specified resource
is printed, unless the @option{-H} option is supplied.
When setting new limits, if neither @option{-H} nor @option{-S} is supplied,
@end table
+@node Modifying Shell Behavior
+@section Modifying Shell Behavior
+
+@menu
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
+@end menu
+
@node The Set Builtin
-@section The Set Builtin
+@subsection The Set Builtin
-This builtin is so complicated that it deserves its own section.
+This builtin is so complicated that it deserves its own section. @code{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.
@table @code
@item set
@btindex set
@example
-set [--abefhkmnptuvxBCHP] [-o @var{option}] [@var{argument} @dots{}]
+set [--abefhkmnptuvxBCEHPT] [-o @var{option}] [@var{argument} @dots{}]
+set [+abefhkmnptuvxBCEHPT] [+o @var{option}] [@var{argument} @dots{}]
@end example
If no options or arguments are supplied, @code{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.
+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 @sc{posix} mode, only shell variables are listed.
When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:
@item -e
Exit immediately if a simple command (@pxref{Simple Commands}) exits
-with a non-zero status, unless the command that fails is part of an
-@code{until} or @code{while} loop, part of an @code{if} statement,
-part of a @code{&&} or @code{||} list, or if the command's return
-status is being inverted using @code{!}.
+with a non-zero status, unless the command that fails is part of the
+command list immediately following a @code{while} or @code{until} keyword,
+part of the test in an @code{if} statement,
+part of a command executed in a @code{&&} or @code{||b} list,
+any command in a pipeline but the last,
+or if the command's return status is being inverted using @code{!}.
+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 @code{ERR}, if set, is executed before the shell exits.
@item -f
@item emacs
Use an @code{emacs}-style line editing interface (@pxref{Command Line Editing}).
+This also affects the editing interface used for @code{read -e}.
@item errexit
Same as @code{-e}.
+@item errtrace
+Same as @code{-E}.
+
+@item functrace
+Same as @code{-T}.
+
@item hashall
Same as @code{-h}.
@item physical
Same as @code{-P}.
+@item 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.
+
@item posix
Change the behavior of Bash where the default operation differs
-from the @sc{posix} 1003.2 standard to match the standard
+from the @sc{posix} standard to match the standard
(@pxref{Bash POSIX Mode}).
This is intended to make Bash behave as a strict superset of that
standard.
@item vi
Use a @code{vi}-style line editing interface.
+This also affects the editing interface used for @code{read -e}.
@item xtrace
Same as @code{-x}.
Turn on privileged mode.
In this mode, the @env{$BASH_ENV} and @env{$ENV} files are not
processed, shell functions are not inherited from the environment,
-and the @env{SHELLOPTS} variable, if it appears in the environment,
-is ignored.
+and the @env{SHELLOPTS}, @env{CDPATH} and @env{GLOBIGNORE} variables,
+if they appear in the environment, are ignored.
If the shell is started with the effective user (group) id not equal to the
real user (group) id, and the @code{-p} option is not supplied, these actions
are taken and the effective user id is set to the real user id.
@item -t
Exit after reading and executing one command.
-@item -u
-Treat unset variables as an error when performing parameter expansion.
-An error message will be written to the standard error, and a non-interactive
-shell will exit.
+@item -u
+Treat unset variables as an error when performing parameter expansion.
+An error message will be written to the standard error, and a non-interactive
+shell will exit.
+
+@item -v
+Print shell input lines as they are read.
+
+@item -x
+Print a trace of simple commands, @code{for} commands, @code{case}
+commands, @code{select} commands, and arithmetic @code{for} commands
+and their arguments or associated word lists after they are
+expanded and before they are executed. The value of the @env{PS4}
+variable is expanded and the resultant value is printed before
+the command and its expanded arguments.
+
+@item -B
+The shell will perform brace expansion (@pxref{Brace Expansion}).
+This option is on by default.
+
+@item -C
+Prevent output redirection using @samp{>}, @samp{>&}, and @samp{<>}
+from overwriting existing files.
+
+@item -E
+If set, any trap on @code{ERR} is inherited by shell functions, command
+substitutions, and commands executed in a subshell environment.
+The @code{ERR} trap is normally not inherited in such cases.
+
+@item -H
+Enable @samp{!} style history substitution (@pxref{History Interaction}).
+This option is on by default for interactive shells.
+
+@item -P
+If set, do not follow symbolic links when performing commands such as
+@code{cd} which change the current directory. The physical directory
+is used instead. By default, Bash follows
+the logical chain of directories when performing commands
+which change the current directory.
+
+For example, if @file{/usr/sys} is a symbolic link to @file{/usr/local/sys}
+then:
+@example
+$ cd /usr/sys; echo $PWD
+/usr/sys
+$ cd ..; pwd
+/usr
+@end example
+
+@noindent
+If @code{set -P} is on, then:
+@example
+$ cd /usr/sys; echo $PWD
+/usr/local/sys
+$ cd ..; pwd
+/usr/local
+@end example
+
+@item -T
+If set, any trap on @code{DEBUG} and @code{RETURN} are inherited by
+shell functions, command substitutions, and commands executed
+in a subshell environment.
+The @code{DEBUG} and @code{RETURN} traps are normally not inherited
+in such cases.
+
+@item --
+If no arguments follow this option, then the positional parameters are
+unset. Otherwise, the positional parameters are set to the
+@var{arguments}, even if some of them begin with a @samp{-}.
+
+@item -
+Signal the end of options, cause all remaining @var{arguments}
+to be assigned to the positional parameters. The @option{-x}
+and @option{-v} options are turned off.
+If there are no arguments, the positional parameters remain unchanged.
+@end table
+
+Using @samp{+} rather than @samp{-} 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 @code{$-}.
+
+The remaining N @var{arguments} are positional parameters and are
+assigned, in order, to @code{$1}, @code{$2}, @dots{} @code{$N}.
+The special parameter @code{#} is set to N.
+
+The return status is always zero unless an invalid option is supplied.
+@end table
+
+@node The Shopt Builtin
+@subsection The Shopt Builtin
+
+This builtin allows you to change additional shell optional behavior.
+
+@table @code
+
+@item shopt
+@btindex shopt
+@example
+shopt [-pqsu] [-o] [@var{optname} @dots{}]
+@end example
+Toggle the values of variables controlling optional shell behavior.
+With no options, or with the @option{-p} option, a list of all settable
+options is displayed, with an indication of whether or not each is set.
+The @option{-p} option causes output to be displayed in a form that
+may be reused as input.
+Other options have the following meanings:
+
+@table @code
+@item -s
+Enable (set) each @var{optname}.
+
+@item -u
+Disable (unset) each @var{optname}.
+
+@item -q
+Suppresses normal output; the return status
+indicates whether the @var{optname} is set or unset.
+If multiple @var{optname} arguments are given with @option{-q},
+the return status is zero if all @var{optnames} are enabled;
+non-zero otherwise.
+
+@item -o
+Restricts the values of
+@var{optname} to be those defined for the @option{-o} option to the
+@code{set} builtin (@pxref{The Set Builtin}).
+@end table
+
+If either @option{-s} or @option{-u}
+is used with no @var{optname} arguments, the display is limited to
+those options which are set or unset, respectively.
+
+Unless otherwise noted, the @code{shopt} options are disabled (off)
+by default.
+
+The return status when listing options is zero if all @var{optnames}
+are enabled, non-zero otherwise. When setting or unsetting options,
+the return status is zero unless an @var{optname} is not a valid shell
+option.
+
+The list of @code{shopt} options is:
+@table @code
+
+@item autocd
+If set, a command name that is the name of a directory is executed as if
+it were the argument to the @code{cd} command.
+This option is only used by interactive shells.
+
+@item cdable_vars
+If this is set, an argument to the @code{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.
+
+@item cdspell
+If set, minor errors in the spelling of a directory component in a
+@code{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.
+
+@item 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.
+
+@item 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 (@pxref{Job Control}).
+The shell always postpones exiting if any jobs are stopped.
+
+@item checkwinsize
+If set, Bash checks the window size after each command
+and, if necessary, updates the values of
+@env{LINES} and @env{COLUMNS}.
+
+@item 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.
+
+@item compat31
+If set, Bash
+changes its behavior to that of version 3.1 with respect to quoted
+arguments to the conditional command's =~ operator.
+
+@item dirspell
+If set, Bash
+attempts spelling correction on directory names during word completion
+if the directory name initially supplied does not exist.
+
+@item dotglob
+If set, Bash includes filenames beginning with a `.' in
+the results of filename expansion.
+
+@item execfail
+If this is set, a non-interactive shell will not exit if
+it cannot execute the file specified as an argument to the @code{exec}
+builtin command. An interactive shell does not exit if @code{exec}
+fails.
+
+@item expand_aliases
+If set, aliases are expanded as described below under Aliases,
+@ref{Aliases}.
+This option is enabled by default for interactive shells.
+
+@item extdebug
+If set, behavior intended for use by debuggers is enabled:
+
+@enumerate
+@item
+The @option{-F} option to the @code{declare} builtin (@pxref{Bash Builtins})
+displays the source file name and line number corresponding to each function
+name supplied as an argument.
+
+@item
+If the command run by the @code{DEBUG} trap returns a non-zero value, the
+next command is skipped and not executed.
+
+@item
+If the command run by the @code{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 @code{.} or @code{source} builtins), a call to
+@code{return} is simulated.
+
+@item
+@code{BASH_ARGC} and @code{BASH_ARGV} are updated as described in their
+descriptions (@pxref{Bash Variables}).
+
+@item
+Function tracing is enabled: command substitution, shell functions, and
+subshells invoked with @code{( @var{command} )} inherit the
+@code{DEBUG} and @code{RETURN} traps.
+
+@item
+Error tracing is enabled: command substitution, shell functions, and
+subshells invoked with @code{( @var{command} )} inherit the
+@code{ERROR} trap.
+@end enumerate
+
+@item extglob
+If set, the extended pattern matching features described above
+(@pxref{Pattern Matching}) are enabled.
+
+@item extquote
+If set, @code{$'@var{string}'} and @code{$"@var{string}"} quoting is
+performed within @code{$@{@var{parameter}@}} expansions
+enclosed in double quotes. This option is enabled by default.
+
+@item failglob
+If set, patterns which fail to match filenames during pathname expansion
+result in an expansion error.
+
+@item force_fignore
+If set, the suffixes specified by the @env{FIGNORE} shell variable
+cause words to be ignored when performing word completion even if
+the ignored words are the only possible completions.
+@xref{Bash Variables}, for a description of @env{FIGNORE}.
+This option is enabled by default.
+
+@item globstar
+If set, the pattern @samp{**} used in a filename expansion context will
+match a files and zero or more directories and subdirectories.
+If the pattern is followed by a @samp{/}, only directories and
+subdirectories match.
+
+@item gnu_errfmt
+If set, shell error messages are written in the standard @sc{gnu} error
+message format.
+
+@item histappend
+If set, the history list is appended to the file named by the value
+of the @env{HISTFILE}
+variable when the shell exits, rather than overwriting the file.
+
+@item histreedit
+If set, and Readline
+is being used, a user is given the opportunity to re-edit a
+failed history substitution.
+
+@item 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.
+
+@item hostcomplete
+If set, and Readline is being used, Bash will attempt to perform
+hostname completion when a word containing a @samp{@@} is being
+completed (@pxref{Commands For Completion}). This option is enabled
+by default.
+
+@item huponexit
+If set, Bash will send @code{SIGHUP} to all jobs when an interactive
+login shell exits (@pxref{Signals}).
+
+@item interactive_comments
+Allow a word beginning with @samp{#}
+to cause that word and all remaining characters on that
+line to be ignored in an interactive shell.
+This option is enabled by default.
+
+@item lithist
+If enabled, and the @code{cmdhist}
+option is enabled, multi-line commands are saved to the history with
+embedded newlines rather than using semicolon separators where possible.
+
+@item login_shell
+The shell sets this option if it is started as a login shell
+(@pxref{Invoking Bash}).
+The value may not be changed.
+
+@item mailwarn
+If set, and a file that Bash is checking for mail has been
+accessed since the last time it was checked, the message
+@code{"The mail in @var{mailfile} has been read"} is displayed.
+
+@item no_empty_cmd_completion
+If set, and Readline is being used, Bash will not attempt to search
+the @env{PATH} for possible completions when completion is attempted
+on an empty line.
-@item -v
-Print shell input lines as they are read.
+@item nocaseglob
+If set, Bash matches filenames in a case-insensitive fashion when
+performing filename expansion.
-@item -x
-Print a trace of simple commands and their arguments after they are
-expanded and before they are executed.
+@item nocasematch
+If set, Bash matches patterns in a case-insensitive fashion when
+performing matching while executing @code{case} or @code{[[}
+conditional commands.
-@item -B
-The shell will perform brace expansion (@pxref{Brace Expansion}).
-This option is on by default.
+@item nullglob
+If set, Bash allows filename patterns which match no
+files to expand to a null string, rather than themselves.
-@item -C
-Prevent output redirection using @samp{>}, @samp{>&}, and @samp{<>}
-from overwriting existing files.
+@item progcomp
+If set, the programmable completion facilities
+(@pxref{Programmable Completion}) are enabled.
+This option is enabled by default.
-@item -H
-Enable @samp{!} style history substitution (@pxref{History Interaction}).
-This option is on by default for interactive shells.
+@item promptvars
+If set, prompt strings undergo
+parameter expansion, command substitution, arithmetic
+expansion, and quote removal after being expanded
+as described below (@pxref{Printing a Prompt}).
+This option is enabled by default.
-@item -P
-If set, do not follow symbolic links when performing commands such as
-@code{cd} which change the current directory. The physical directory
-is used instead. By default, Bash follows
-the logical chain of directories when performing commands
-which change the current directory.
+@item restricted_shell
+The shell sets this option if it is started in restricted mode
+(@pxref{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.
-For example, if @file{/usr/sys} is a symbolic link to @file{/usr/local/sys}
-then:
-@example
-$ cd /usr/sys; echo $PWD
-/usr/sys
-$ cd ..; pwd
-/usr
-@end example
+@item shift_verbose
+If this is set, the @code{shift}
+builtin prints an error message when the shift count exceeds the
+number of positional parameters.
-@noindent
-If @code{set -P} is on, then:
-@example
-$ cd /usr/sys; echo $PWD
-/usr/local/sys
-$ cd ..; pwd
-/usr/local
-@end example
+@item sourcepath
+If set, the @code{source} builtin uses the value of @env{PATH}
+to find the directory containing the file supplied as an argument.
+This option is enabled by default.
-@item --
-If no arguments follow this option, then the positional parameters are
-unset. Otherwise, the positional parameters are set to the
-@var{arguments}, even if some of them begin with a @samp{-}.
+@item xpg_echo
+If set, the @code{echo} builtin expands backslash-escape sequences
+by default.
-@item -
-Signal the end of options, cause all remaining @var{arguments}
-to be assigned to the positional parameters. The @option{-x}
-and @option{-v} options are turned off.
-If there are no arguments, the positional parameters remain unchanged.
@end table
-Using @samp{+} rather than @samp{-} 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 @code{$-}.
-
-The remaining N @var{arguments} are positional parameters and are
-assigned, in order, to @code{$1}, @code{$2}, @dots{} @code{$N}.
-The special parameter @code{#} is set to N.
+@noindent
+The return status when listing options is zero if all @var{optnames}
+are enabled, non-zero otherwise.
+When setting or unsetting options, the return status is zero unless an
+@var{optname} is not a valid shell option.
-The return status is always zero unless an invalid option is supplied.
@end table
@node Special Builtins
@section Special Builtins
@cindex special builtin
-For historical reasons, the @sc{posix} 1003.2 standard has classified
+For historical reasons, the @sc{posix} standard has classified
several builtin commands as @emph{special}.
When Bash is executing in @sc{posix} mode, the special builtins
differ from other builtin commands in three respects:
@item PATH
A colon-separated list of directories in which the shell looks for
commands.
+A zero-length (null) directory name in the value of @code{PATH} indicates the
+current directory.
+A null directory name may appear as two adjacent colons, or as an initial
+or trailing colon.
+
@item PS1
The primary prompt string. The default value is @samp{\s-\v\$ }.
@item BASH
The full pathname used to execute the current instance of Bash.
+@item BASHPID
+Expands to the process id of the current Bash process.
+This differs from @code{$$} under certain circumstances, such as subshells
+that do not require Bash to be re-initialized.
+
+@item BASH_ALIASES
+An associative array variable whose members correspond to the internal
+list of aliases as maintained by the @code{alias} builtin
+(@pxref{Bourne Shell Builtins}).
+Elements added to this array appear in the alias list; unsetting array
+elements cause aliases to be removed from the alias list.
+
+@item 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 @code{.} or @code{source}) is at the top of the stack. When a
+subroutine is executed, the number of parameters passed is pushed onto
+@code{BASH_ARGC}.
+The shell sets @code{BASH_ARGC} only when in extended debugging mode
+(see @ref{The Shopt Builtin}
+for a description of the @code{extdebug} option to the @code{shopt}
+builtin).
+
+@item 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 @code{BASH_ARGV}.
+The shell sets @code{BASH_ARGV} only when in extended debugging mode
+(see @ref{The Shopt Builtin}
+for a description of the @code{extdebug} option to the @code{shopt}
+builtin).
+
+@item BASH_CMDS
+An associative array variable whose members correspond to the internal
+hash table of commands as maintained by the @code{hash} builtin
+(@pxref{Bourne Shell Builtins}).
+Elements added to this array appear in the hash table; unsetting array
+elements cause commands to be removed from the hash table.
+
+@item BASH_COMMAND
+The command currently being executed or about to be executed, unless the
+shell is executing a command as the result of a trap,
+in which case it is the command executing at the time of the trap.
+
@item BASH_ENV
If this variable is set when Bash is invoked to execute a shell
script, its value is expanded and used as the name of a startup file
to read before executing the script. @xref{Bash Startup Files}.
-@item BASH_VERSION
-The version number of the current instance of Bash.
+@item BASH_EXECUTION_STRING
+The command argument to the @option{-c} invocation option.
+
+@item BASH_LINENO
+An array variable whose members are the line numbers in source files
+corresponding to each member of @var{FUNCNAME}.
+@code{$@{BASH_LINENO[$i]@}} is the line number in the source file where
+@code{$@{FUNCNAME[$i]@}} was called (or @code{$@{BASH_LINENO[$i-1]@}} if
+referenced within another shell function).
+The corresponding source file name is @code{$@{BASH_SOURCE[$i]@}}.
+Use @code{LINENO} to obtain the current line number.
+
+@item BASH_REMATCH
+An array variable whose members are assigned by the @samp{=~} binary
+operator to the @code{[[} conditional command
+(@pxref{Conditional Constructs}).
+The element with index 0 is the portion of the string
+matching the entire regular expression.
+The element with index @var{n} is the portion of the
+string matching the @var{n}th parenthesized subexpression.
+This variable is read-only.
+
+@item BASH_SOURCE
+An array variable whose members are the source filenames corresponding
+to the elements in the @code{FUNCNAME} array variable.
+
+@item BASH_SUBSHELL
+Incremented by one each time a subshell or subshell environment is spawned.
+The initial value is 0.
@item BASH_VERSINFO
A readonly array variable (@pxref{Arrays})
@end table
+@item BASH_VERSION
+The version number of the current instance of Bash.
+
@item COLUMNS
Used by the @code{select} builtin command to determine the terminal width
when printing selection lists. Automatically set upon receipt of a
commands invoked by the
programmable completion facilities (@pxref{Programmable Completion}).
+@item COMP_TYPE
+Set to an integer value corresponding to the type of completion attempted
+that caused a completion function to be called:
+@var{TAB}, for normal completion,
+@samp{?}, for listing completions after successive tabs,
+@samp{!}, for listing alternatives on partial word completion,
+@samp{@@}, to list completions if the word is not unmodified,
+or
+@samp{%}, for menu completion.
+This variable is available only in shell functions and external
+commands invoked by the
+programmable completion facilities (@pxref{Programmable Completion}).
+
+@item COMP_KEY
+The key (or final key of a key sequence) used to invoke the current
+completion function.
+
+@item COMP_WORDBREAKS
+The set of characters that the Readline library treats as word
+separators when performing word completion.
+If @code{COMP_WORDBREAKS} is unset, it loses its special properties,
+even if it is subsequently reset.
+
@item COMP_WORDS
An array variable consisting of the individual
words in the current command line.
+The words are split on shell metacharacters as the shell parser would
+separate them.
This variable is available only in shell functions invoked by the
programmable completion facilities (@pxref{Programmable Completion}).
If @env{DIRSTACK} is unset, it loses its special properties, even if
it is subsequently reset.
+@item EMACS
+If Bash finds this variable in the environment when the shell
+starts with value @samp{t}, it assumes that the shell is running in an
+emacs shell buffer and disables line editing.
+
@item EUID
The numeric effective user id of the current user. This variable
is readonly.
value is @samp{.o:~}
@item FUNCNAME
-The name of any currently-executing shell function.
+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 @code{"main"}.
This variable exists only when a shell function is executing.
Assignments to @env{FUNCNAME} have no effect and return an error status.
If @env{FUNCNAME} is unset, it loses its special properties, even if
even if it is subsequently reset.
@item HISTCONTROL
-A value of @samp{ignorespace} means to not enter lines which
-begin with a space or tab into the history list.
-A value of @samp{ignoredups} means to not enter lines which match the last
-entered line.
-A value of @samp{ignoreboth} combines the two options.
-Unset, or set to any other value than those above, means to save
-all lines on the history list.
+A colon-separated list of values controlling how commands are saved on
+the history list.
+If the list of values includes @samp{ignorespace}, lines which begin
+with a space character are not saved in the history list.
+A value of @samp{ignoredups} causes lines which match the previous
+history entry to not be saved.
+A value of @samp{ignoreboth} is shorthand for
+@samp{ignorespace} and @samp{ignoredups}.
+A value of @samp{erasedups} causes all previous lines matching the
+current line to be removed from the history list before that line
+is saved.
+Any value not in the above list is ignored.
+If @env{HISTCONTROL} is unset, or does not include a valid value,
+all lines read by the shell parser are saved on the history list,
+subject to the value of @env{HISTIGNORE}.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
@env{HISTCONTROL}.
@item 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.
+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.
The maximum number of commands to remember on the history list.
The default value is 500.
+@item HISTTIMEFORMAT
+If this variable is set and not null, its value is used as a format string
+for @var{strftime} to print the time stamp associated with each history
+entry displayed by the @code{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.
+
@item HOSTFILE
Contains the name of a file in the same format as @file{/etc/hosts} that
should be read when the shell needs to complete a hostname.
If set, the value is interpreted as a command to execute
before the printing of each primary prompt (@env{$PS1}).
+@item PROMPT_DIRTRIM
+If set to a number greater than zero, the value is used as the number of
+trailing directory components to retain when expanding the @code{\w} and
+@code{\W} prompt string escapes (@pxref{Printing a Prompt}).
+Characters removed are replaced with an ellipsis.
+
@item PS3
The value of this variable is used as the prompt for the
@code{select} command. If this variable is not set, the
becomes the value assigned plus the number of seconds
since the assignment.
+@item 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.
+
@item SHELLOPTS
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the @option{-o} option to the
A trailing newline is added when the format string is displayed.
@item TMOUT
-If set to a value greater than zero, the value is interpreted as
+If set to a value greater than zero, @code{TMOUT} is treated as the
+default timeout for the @code{read} builtin (@pxref{Bash Builtins}).
+The @code{select} command (@pxref{Conditional Constructs}) terminates
+if input does not arrive after @code{TMOUT} seconds when input is coming
+from a terminal.
+
+In an interactive shell, the value is interpreted as
the number of seconds to wait for input after issuing the primary
prompt when the shell is interactive.
Bash terminates after that number of seconds if input does
not arrive.
+@item TMPDIR
+If set, Bash uses its value as the name of a directory in which
+Bash creates temporary files for the shell's use.
+
@item UID
The numeric real user id of the current user. This variable is readonly.
In addition to the single-character shell command-line options
(@pxref{The Set Builtin}), there are several multi-character
options that you can use. These options must appear on the command
-line before the single-character options in order for them
-to be recognized.
+line before the single-character options to be recognized.
@table @code
+@item --debugger
+Arrange for the debugger profile to be executed before the shell
+starts. Turns on extended debugging mode (see @ref{The Shopt Builtin}
+for a description of the @code{extdebug} option to the @code{shopt}
+builtin) and shell function tracing
+(see @ref{The Set Builtin} for a description of the @code{-o functrace}
+option).
+
@item --dump-po-strings
A list of all double-quoted strings preceded by @samp{$}
-is printed on the standard ouput
+is printed on the standard output
in the @sc{gnu} @code{gettext} PO (portable object) file format.
Equivalent to @option{-D} except for the output format.
Equivalent to @option{-D}.
@item --help
-Display a usage message on standard output and exit sucessfully.
+Display a usage message on standard output and exit successfully.
@item --init-file @var{filename}
@itemx --rcfile @var{filename}
in an interactive shell.
@item --login
-Make this shell act as if it had been directly invoked by login.
-When the shell is interactive, this is equivalent to starting a
-login shell with @samp{exec -l bash}.
-When the shell is not interactive, the login shell startup files will
-be executed.
-@samp{exec bash --login}
-will replace the current shell with a Bash login shell.
-@xref{Bash Startup Files}, for a description of the special behavior
-of a login shell.
+Equivalent to @option{-l}.
@item --noediting
Do not use the @sc{gnu} Readline library (@pxref{Command Line Editing})
@item --posix
Change the behavior of Bash where the default operation differs
-from the @sc{posix} 1003.2 standard to match the standard. This
+from the @sc{posix} standard to match the standard. This
is intended to make Bash behave as a strict superset of that
standard. @xref{Bash POSIX Mode}, for a description of the Bash
@sc{posix} mode.
Force the shell to run interactively. Interactive shells are
described in @ref{Interactive Shells}.
+@item -l
+Make this shell act as if it had been directly invoked by login.
+When the shell is interactive, this is equivalent to starting a
+login shell with @samp{exec -l bash}.
+When the shell is not interactive, the login shell startup files will
+be executed.
+@samp{exec bash -l} or @samp{exec bash --login}
+will replace the current shell with a Bash login shell.
+@xref{Bash Startup Files}, for a description of the special behavior
+of a login shell.
+
@item -r
Make the shell a restricted shell (@pxref{The Restricted Shell}).
@item -D
A list of all double-quoted strings preceded by @samp{$}
-is printed on the standard ouput.
+is printed on the standard output.
These are the strings that
are subject to language translation when the current locale
is not @code{C} or @code{POSIX} (@pxref{Locale Translation}).
@item [-+]O [@var{shopt_option}]
@var{shopt_option} is one of the shell options accepted by the
-@code{shopt} builtin (@pxref{Shell Builtin Commands}).
+@code{shopt} builtin (@pxref{The Shopt Builtin}).
If @var{shopt_option} is present, @option{-O} sets the value of that option;
@option{+O} unsets it.
If @var{shopt_option} is not supplied, the names and values of the shell
@section Bash Startup Files
@cindex startup files
-This section describs how Bash executes its startup files.
+This section describes how Bash executes its startup files.
If any of the files exist but cannot be read, Bash reports an error.
Tildes are expanded in file names as described above under
Tilde Expansion (@pxref{Tilde Expansion}).
@subsubheading Invoked by remote shell daemon
-Bash attempts to determine when it is being run by the remote shell
-daemon, usually @code{rshd}. If Bash determines it is being run by
-rshd, it reads and executes commands from @file{~/.bashrc}, if that
+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 @code{rshd}, or the secure shell daemon @code{sshd}.
+If Bash determines it is being run in
+this fashion, it reads and executes commands from @file{~/.bashrc}, if that
file exists and is readable.
It will not do this if invoked as @code{sh}.
The @option{--norc} option may be used to inhibit this behavior, and the
An interactive shell
is one started without non-option arguments, unless @option{-s} is
-specified, without specifiying the @option{-c} option, and
-whose input and output are both
+specified, without specifying the @option{-c} option, and
+whose input and error output are both
connected to terminals (as determined by @code{isatty(3)}),
or one started with the @option{-i} option.
@item
An interactive login shell sends a @code{SIGHUP} to all jobs on exit
-if the @code{hupoxexit} shell option has been enabled (@pxref{Signals}).
+if the @code{huponexit} shell option has been enabled (@pxref{Signals}).
@item
The @option{-n} invocation option is ignored, and @samp{set -n} has
@item
When running in @sc{posix} mode, a special builtin returning an error
status will not cause the shell to exit (@pxref{Bash POSIX Mode}).
+
@item
A failed @code{exec} will not cause the shell to exit
(@pxref{Bourne Shell Builtins}).
@item
Simple spelling correction for directory arguments to the @code{cd}
builtin is enabled by default (see the description of the @code{cdspell}
-option to the @code{shopt} builtin in @ref{Bash Builtins}).
+option to the @code{shopt} builtin in @ref{The Shopt Builtin}).
@item
The shell will check the value of the @env{TMOUT} variable and exit
@file{/dev/stdin}, @file{/dev/stdout}, or @file{/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.
+
@table @code
@item -a @var{file}
True if @var{file} exists.
True if @var{file} exists and has been modified since it was last read.
@item @var{file1} -nt @var{file2}
-True if @var{file1} is newer (according to
-modification date) than @var{file2}.
+True if @var{file1} is newer (according to modification date)
+than @var{file2}, or if @var{file1} exists and @var{file2} does not.
@item @var{file1} -ot @var{file2}
-True if @var{file1} is older than @var{file2}.
+True if @var{file1} is older than @var{file2},
+or if @var{file2} exists and @var{file1} does not.
@item @var{file1} -ef @var{file2}
-True if @var{file1} and @var{file2} have the same device and
+True if @var{file1} and @var{file2} refer to the same device and
inode numbers.
@item -o @var{optname}
@item @var{string1} == @var{string2}
True if the strings are equal.
-@samp{=} may be used in place of @samp{==}.
+@samp{=} may be used in place of @samp{==} for strict @sc{posix} compliance.
@item @var{string1} != @var{string2}
True if the strings are not equal.
@cindex arithmetic evaluation
The shell allows arithmetic expressions to be evaluated, as one of
-the shell expansions or by the @code{let} builtin.
+the shell expansions or by the @code{let} and the @option{-i} option
+to the @code{declare} builtins.
-Evaluation is done in long integers with no check for overflow,
+Evaluation is done in fixed-width integers with no check for overflow,
though division by 0 is trapped and flagged as an error.
-The operators and their precedence and associativity are the same
-as in the C language.
+The operators and their precedence, associativity, and values
+are the same as in the C language.
The following list of operators is grouped into levels of
equal-precedence operators.
The levels are listed in order of decreasing precedence.
logical OR
@item expr ? expr : expr
-conditional evaluation
+conditional operator
@item = *= /= %= += -= <<= >>= &= ^= |=
assignment
performed before the expression is evaluated.
Within an expression, shell variables may also be referenced by name
without using the parameter expansion syntax.
+A shell variable that is null or unset evaluates to 0 when referenced
+by name without using the parameter expansion syntax.
The value of a variable is evaluated as an arithmetic expression
-when it is referenced.
+when it is referenced, or when a variable which has been given the
+@var{integer} attribute using @samp{declare -i} is assigned a value.
+A null value evaluates to 0.
A shell variable need not have its integer attribute turned on
to be used in an expression.
The digits greater than 9 are represented by the lowercase letters,
the uppercase letters, @samp{@@}, and @samp{_}, in that order.
If @var{base} is less than or equal to 36, lowercase and uppercase
-letters may be used interchangably to represent numbers between 10
+letters may be used interchangeably to represent numbers between 10
and 35.
Operators are evaluated in order of precedence. Sub-expressions in
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 @samp{=}.
+The characters @samp{/}, @samp{$}, @samp{`}, @samp{=} 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
-@code{ls} to @code{"ls -F"},
+is not expanded a second time.
+This means that one may alias @code{ls} to @code{"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
Aliases are not expanded when the shell is not interactive,
unless the @code{expand_aliases} shell option is set using
-@code{shopt} (@pxref{Bash Builtins}).
+@code{shopt} (@pxref{The Shopt Builtin}).
The rules concerning the definition and use of aliases are
somewhat confusing. Bash
@section Arrays
@cindex arrays
-Bash provides one-dimensional array variables. Any variable may be used as
-an array; the @code{declare} builtin will explicitly declare an array.
+Bash provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array;
+the @code{declare} builtin will explicitly declare an array.
There is no maximum
limit on the size of an array, nor any requirement that members
-be indexed or assigned contiguously. Arrays are zero-based.
+be indexed or assigned contiguously.
+Indexed arrays are referenced using integers (including arithmetic
+expressions (@pxref{Shell Arithmetic}) and are zero-based;
+associative arrays use arbitrary strings.
-An array is created automatically if any variable is assigned to using
-the syntax
+An indexed array is created automatically if any variable is assigned to
+using the syntax
@example
name[@var{subscript}]=@var{value}
@end example
declare -a @var{name}[@var{subscript}]
@end example
@noindent
-is also accepted; the @var{subscript} is ignored. Attributes may be
+is also accepted; the @var{subscript} is ignored.
+
+Associative arrays are created using
+@example
+declare -A @var{name}.
+@end example
+
+Attributes may be
specified for an array variable using the @code{declare} and
@code{readonly} builtins. Each attribute applies to all members of
an array.
@end example
@noindent
where each
-@var{value} is of the form @code{[[@var{subscript}]=]}@var{string}. If
+@var{value} is of the form @code{[@var{subscript}]=}@var{string}.
+Indexed array assignments do not require the bracket and subscript.
+When assigning to indexed arrays, if
the optional subscript is supplied, that index is assigned to;
otherwise the index of the element assigned is the last index assigned
to by the statement plus one. Indexing starts at zero.
+
+When assigning to an associative array, the subscript is required.
+
This syntax is also accepted by the @code{declare}
builtin. Individual array elements may be assigned to using the
@code{name[}@var{subscript}@code{]=}@var{value} syntax introduced above.
conflicts with the shell's filename expansion operators. If the
@var{subscript} is @samp{@@} or @samp{*}, the word expands to all members
of the array @var{name}. These subscripts differ only when the word
-appears within double quotes. If the word is double-quoted,
+appears within double quotes.
+If the word is double-quoted,
@code{$@{name[*]@}} expands to a single word with
the value of each array member separated by the first character of the
@env{IFS} variable, and @code{$@{name[@@]@}} expands each element of
@var{name} to a separate word. When there are no array members,
-@code{$@{name[@@]@}} expands to nothing. This is analogous to the
+@code{$@{name[@@]@}} expands to nothing.
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the original
+word, and the expansion of the last parameter is joined with the last
+part of the original word.
+This is analogous to the
expansion of the special parameters @samp{@@} and @samp{*}.
@code{$@{#name[}@var{subscript}@code{]@}} expands to the length of
@code{$@{name[}@var{subscript}@code{]@}}.
If @var{subscript} is @samp{@@} or
@samp{*}, the expansion is the number of elements in the array.
Referencing an array variable without a subscript is equivalent to
-referencing element zero.
+referencing with a subscript of 0.
The @code{unset} builtin is used to destroy arrays.
@code{unset} @var{name}[@var{subscript}]
destroys the array element at index @var{subscript}.
+Care must be taken to avoid unwanted side effects caused by filename
+generation.
@code{unset} @var{name}, where @var{name} is an array, removes the
entire array. A subscript of @samp{*} or @samp{@@} also removes the
entire array.
The @code{declare}, @code{local}, and @code{readonly}
-builtins each accept a @option{-a}
-option to specify an array. The @code{read}
-builtin accepts a @option{-a}
+builtins each accept a @option{-a} option to specify an indexed
+array and a @option{-A} option to specify an associative array.
+The @code{read} builtin accepts a @option{-a}
option to assign a list of words read from the standard input
to an array, and can read values from the standard input into
individual array elements. The @code{set} and @code{declare}
@btindex pushd
@item pushd
@example
-pushd [@var{dir} | @var{+N} | @var{-N}] [-n]
+pushd [-n] [@var{+N} | @var{-N} | @var{dir} ]
@end example
Save the current directory on the top of the directory stack
With no arguments, @code{pushd} exchanges the top two directories.
@table @code
+@item -n
+Suppresses the normal change of directory when adding directories
+to the stack, so that only the stack is manipulated.
@item +@var{N}
Brings the @var{N}th directory (counting from the left of the
list printed by @code{dirs}, starting with zero) to the top of
Brings the @var{N}th directory (counting from the right of the
list printed by @code{dirs}, starting with zero) to the top of
the list by rotating the stack.
-@item -n
-Suppresses the normal change of directory when adding directories
-to the stack, so that only the stack is manipulated.
@item @var{dir}
Makes the current working directory be the top of the stack, and then
executes the equivalent of `@code{cd} @var{dir}'.
A bell character.
@item \d
The date, in "Weekday Month Date" format (e.g., "Tue May 26").
+@item \D@{@var{format}@}
+The @var{format} is passed to @code{strftime}(3) and the result is inserted
+into the prompt string; an empty @var{format} results in a locale-specific
+time representation. The braces are required.
@item \e
An escape character.
@item \h
@item \V
The release of Bash, version + patchlevel (e.g., 2.00.0)
@item \w
-The current working directory.
+The current working directory, with @env{$HOME} abbreviated with a tilde
+(uses the @env{$PROMPT_DIRTRIM} variable).
@item \W
-The basename of @env{$PWD}.
+The basename of @env{$PWD}, with @env{$HOME} abbreviated with a tilde.
@item \!
The history number of this command.
@item \#
If Bash is started with the name @code{rbash}, or the
@option{--restricted}
+or
+@option{-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 @code{bash}
-with the exception that the following are disallowed:
+with the exception that the following are disallowed or not performed:
+
@itemize @bullet
@item
Changing directories with the @code{cd} builtin.
Adding or deleting builtin commands with the
@option{-f} and @option{-d} options to the @code{enable} builtin.
@item
+Using the @code{enable} builtin command to enable disabled shell builtins.
+@item
Specifying the @option{-p} option to the @code{command} builtin.
@item
Turning off restricted mode with @samp{set +r} or @samp{set +o restricted}.
@end itemize
+These restrictions are enforced after any startup files are read.
+
+When a command that is found to be a shell script is executed
+(@pxref{Shell Scripts}), @code{rbash} turns off any restrictions in
+the shell spawned to execute the script.
+
@node Bash POSIX Mode
@section Bash POSIX Mode
@cindex POSIX Mode
Starting Bash with the @option{--posix} command-line option or executing
@samp{set -o posix} while Bash is running will cause Bash to conform more
-closely to the @sc{posix} 1003.2 standard by changing the behavior to
+closely to the @sc{posix} standard by changing the behavior to
match that specified by @sc{posix} in areas where the Bash default differs.
+When invoked as @code{sh}, Bash enters @sc{posix} mode after reading the
+startup files.
+
The following list is what's changed when `@sc{posix} mode' is in effect:
@enumerate
example, @code{SIGTSTP}.
@item
-Reserved words may not be aliased.
+The @code{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.
+
+@item
+Reserved words appearing in a context where reserved words are recognized
+do not undergo alias expansion.
@item
-The @sc{posix} 1003.2 @env{PS1} and @env{PS2} expansions of @samp{!} to
+The @sc{posix} @env{PS1} and @env{PS2} expansions of @samp{!} to
the history number and @samp{!!} to @samp{!} are enabled,
and parameter expansion is performed on the values of @env{PS1} and
@env{PS2} regardless of the setting of the @code{promptvars} option.
@item
-Interactive comments are enabled by default. (Bash has them on by
-default anyway.)
-
-@item
-The @sc{posix} 1003.2 startup files are executed (@env{$ENV}) rather than
+The @sc{posix} startup files are executed (@env{$ENV}) rather than
the normal Bash files.
@item
@item
The output of @samp{kill -l} prints all the signal names on a single line,
-separated by spaces.
+separated by spaces, without the @samp{SIG} prefix.
+
+@item
+The @code{kill} builtin does not accept signal names with a @samp{SIG}
+prefix.
@item
Non-interactive shells exit if @var{filename} in @code{.} @var{filename}
causes a fatal syntax error in non-interactive shells.
@item
-@sc{posix} 1003.2 `special' builtins are found before shell functions
+@sc{posix} special builtins are found before shell functions
during command lookup.
@item
-If a @sc{posix} 1003.2 special builtin returns an error status, a
+If a @sc{posix} special builtin returns an error status, a
non-interactive shell exits. The fatal errors are those listed in
-the POSIX.2 standard, and include things like passing incorrect options,
+the POSIX standard, and include things like passing incorrect options,
redirection errors, variable assignment errors for assignments preceding
the command name, and so on.
@item
-If the @code{cd} builtin finds a directory to change to
-using @env{$CDPATH}, the
-value it assigns to the @env{PWD} variable does not contain any
-symbolic links, as if @samp{cd -P} had been executed.
-
-@item
If @env{CDPATH} is set, the @code{cd} builtin will not implicitly
append the current directory to it. This means that @code{cd} will
fail if no valid directory name can be constructed from
Process substitution is not available.
@item
-Assignment statements preceding @sc{posix} 1003.2 special builtins
+Assignment statements preceding @sc{posix} special builtins
persist in the shell environment after the builtin completes.
@item
@item
The @code{export} and @code{readonly} builtin commands display their
-output in the format required by @sc{posix} 1003.2.
+output in the format required by @sc{posix}.
@item
The @code{trap} builtin displays signal names without the leading
@code{SIG}.
@item
+The @code{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 @samp{-} as the
+first argument.
+
+@item
The @code{.} and @code{source} builtins do not search the current directory
for the filename argument if it is not found by searching @env{PATH}.
Alias expansion is always enabled, even in non-interactive shells.
@item
+When the @code{alias} builtin displays alias definitions, it does not
+display them with a leading @samp{alias } unless the @option{-p} option
+is supplied.
+
+@item
When the @code{set} builtin is invoked without options, it does not display
shell function names and definitions.
When the @code{set} builtin is invoked without options, it displays
variable values without quotes, unless they contain shell metacharacters,
even if the result contains nonprinting characters.
+
+@item
+When the @code{cd} builtin is invoked in @var{logical} mode, and the pathname
+constructed from @code{$PWD} and the directory name supplied as an argument
+does not refer to an existing directory, @code{cd} will fail instead of
+falling back to @var{physical} mode.
+
+@item
+When the @code{pwd} builtin is supplied the @option{-P} option, it resets
+@code{$PWD} to a pathname containing no symlinks.
+
+@item
+The @code{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
+@option{-P} option.
+
+@item
+When listing the history, the @code{fc} builtin does not include an
+indication of whether or not a history entry has been modified.
+
+@item
+The default editor used by @code{fc} is @code{ed}.
+
+@item
+The @code{type} and @code{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 @code{$PATH}.
+
+@item
+The @code{vi} editing mode will invoke the @code{vi} editor directly when
+the @samp{v} command is run, instead of checking @code{$VISUAL} and
+@code{$EDITOR}.
+
+@item
+When the @code{xpg_echo} option is enabled, Bash does not attempt to interpret
+any arguments to @code{echo} as options. Each argument is displayed, after
+escape characters are converted.
+
+@item
+The @code{ulimit} builtin uses a block size of 512 bytes for the @option{-c}
+and @option{-f} options.
+
@end enumerate
-There is other @sc{posix} 1003.2 behavior that Bash does not implement.
+There is other @sc{posix} behavior that Bash does not implement by
+default even when in @sc{posix} mode.
Specifically:
@enumerate
-@item
-Assignment statements affect the execution environment of all
-builtins, not just special ones.
@item
-When a subshell is created to execute a shell script with execute permission,
-but without a leading @samp{#!}, Bash sets @code{$0} to the full pathname of
-the script as found by searching @code{$PATH}, rather than the command as
-typed by the user.
+The @code{fc} builtin checks @code{$EDITOR} as a program to edit history
+entries if @code{FCEDIT} is unset, rather than defaulting directly to
+@code{ed}. @code{fc} uses @code{ed} if @code{EDITOR} is unset.
@item
-When using @samp{.} to source a shell script found in @code{$PATH}, bash
-checks execute permission bits rather than read permission bits, just as
-if it were searching for a command.
+As noted above, Bash requires the @code{xpg_echo} option to be enabled for
+the @code{echo} builtin to be fully conformant.
@end enumerate
+Bash can be configured to be @sc{posix}-conformant by default, by specifying
+the @option{--enable-strict-posix-default} to @code{configure} when building
+(@pxref{Optional Features}).
+
@node Job Control
@chapter Job Control
causing pending output and typeahead to be discarded.
There are a number of ways to refer to a job in the shell. The
-character @samp{%} introduces a job name.
+character @samp{%} introduces a job specification (@var{jobspec}).
Job number @code{n} may be referred to as @samp{%n}.
-The symbols @samp{%%} and
-@samp{%+} 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 @samp{%-}. In output
-pertaining to jobs (e.g., the output of the @code{jobs} command),
-the current job is always flagged with a @samp{+}, and the
+The symbols @samp{%%} and @samp{%+} refer to the shell's notion of the
+current job, which is the last job stopped while it was in the foreground
+or started in the background.
+A single @samp{%} (with no accompanying job specification) also refers
+to the current job.
+The previous job may be referenced using @samp{%-}.
+If there is only a single job, @samp{%+} and @samp{%-} can both be used
+to refer to that job.
+In output pertaining to jobs (e.g., the output of the @code{jobs}
+command), the current job is always flagged with a @samp{+}, and the
previous job with a @samp{-}.
A job may also be referred to
Any trap on @code{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.
+If an attempt to exit Bash is made while jobs are stopped, (or running, if
+the @code{checkjobs} option is enabled -- see @ref{The Shopt Builtin}), the
+shell prints a warning message, and if the @code{checkjobs} option is
+enabled, lists the jobs and their statuses.
The @code{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.
+Bash does not print another warning, and any stopped jobs are terminated.
@node Job Control Builtins
@section Job Control Builtins
@item bg
@btindex bg
@example
-bg [@var{jobspec}]
+bg [@var{jobspec} @dots{}]
@end example
-Resume the suspended job @var{jobspec} in the background, as if it
+Resume each suspended job @var{jobspec} in the background, as if it
had been started with @samp{&}.
If @var{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 @var{jobspec} was
-not found or @var{jobspec} specifies a job that was started without
-job control.
+enabled, or, when run with job control enabled, any
+@var{jobspec} was not found or specifies a job
+that was started without job control.
@item fg
@btindex fg
@end example
Send a signal specified by @var{sigspec} or @var{signum} to the process
named by job specification @var{jobspec} or process @sc{id} @var{pid}.
-@var{sigspec} is either a signal name such as @code{SIGINT} (with or without
-the @code{SIG} prefix) or a signal number; @var{signum} is a signal number.
+@var{sigspec} is either a case-insensitive signal name such as
+@code{SIGINT} (with or without the @code{SIG} prefix)
+or a signal number; @var{signum} is a signal number.
If @var{sigspec} and @var{signum} are not present, @code{SIGTERM} is used.
The @option{-l} option lists the signal names.
If any arguments are supplied when @option{-l} is given, the names of the
@item wait
@btindex wait
@example
-wait [@var{jobspec} or @var{pid}]
+wait [@var{jobspec} or @var{pid} ...]
@end example
-Wait until the child process specified by process @sc{id} @var{pid} or job
-specification @var{jobspec} exits and return the exit status of the last
-command waited for.
+Wait until the child process specified by each process @sc{id} @var{pid}
+or job specification @var{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.
suspend [-f]
@end example
Suspend the execution of this shell until it receives a
-@code{SIGCONT} signal. The @option{-f} option means to suspend
-even if the shell is a login shell.
+@code{SIGCONT} signal.
+A login shell cannot be suspended; the @option{-f}
+option can be used to override this and force the suspension.
@end table
@set readline-appendix
@set history-appendix
@cindex Readline, how to use
-@include rluser.texinfo
+@include rluser.texi
@cindex History, how to use
-@include hsuser.texinfo
+@include hsuser.texi
@clear readline-appendix
@clear history-appendix
@sc{gnu} operating systems, nearly every version of Unix, and several
non-Unix systems such as BeOS and Interix.
Other independent ports exist for
-@sc{ms-dos}, @sc{os/2}, Windows @sc{95/98}, and Windows @sc{nt}.
+@sc{ms-dos}, @sc{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.
@end menu
@item --with-bash-malloc
Use the Bash version of
-@code{malloc} in @file{lib/malloc/malloc.c}. This is not the same
+@code{malloc} in the directory @file{lib/malloc}. This is not the same
@code{malloc} that appears in @sc{gnu} libc, but an older version
-derived from the 4.2 @sc{bsd} @code{malloc}. This @code{malloc} is
-very fast, but wastes some space on each allocation.
+originally derived from the 4.2 @sc{bsd} @code{malloc}. This @code{malloc}
+is very fast, but wastes some space on each allocation.
This option is enabled by default.
The @file{NOTES} file contains a list of systems for
which this should be turned off, and @code{configure} disables this
@item --with-installed-readline[=@var{PREFIX}]
Define this to make Bash link with a locally-installed version of Readline
rather than the version in @file{lib/readline}. This works only with
-Readline 4.2 and later versions. If @var{PREFIX} is @code{yes} or not
+Readline 5.0 and later versions. If @var{PREFIX} is @code{yes} or not
supplied, @code{configure} uses the values of the make variables
@code{includedir} and @code{libdir}, which are subdirectories of @code{prefix}
by default, to find the installed version of Readline if it is not in
@item --enable-largefile
Enable support for @uref{http://www.sas.com/standards/large_file/x_open.20Mar96.html,
large files} if the operating system requires special compiler options
-to build programs which can access large files.
+to build programs which can access large files. This is enabled by
+default, if the operating system provides large file support.
@item --enable-profiling
This builds a Bash binary that produces profiling information to be
( @code{b@{a,b@}c} @expansion{} @code{bac bbc} ).
See @ref{Brace Expansion}, for a complete description.
+@item --enable-casemod-attributes
+Include support for case-modifying attributes in the @code{declare} builtin
+and assignment statements. Variables with the @var{uppercase} attribute,
+for example, will have their values converted to uppercase upon assignment.
+
+@item --enable-casemod-expansion
+Include support for case-modifying word expansions.
+
@item --enable-command-timing
Include support for recognizing @code{time} as a reserved word and for
displaying timing statistics for the pipeline following @code{time}
This allows pipelines as well as shell builtins and functions to be timed.
@item --enable-cond-command
-Include support for the @code{[[} conditional command
+Include support for the @code{[[} conditional command.
+(@pxref{Conditional Constructs}).
+
+@item --enable-cond-regexp
+Include support for matching POSIX regular expressions using the
+@samp{=~} binary operator in the @code{[[} conditional command.
(@pxref{Conditional Constructs}).
+@item --enable-coprocesses
+Include support for coprocesses and the @code{coproc} reserved word
+(@pxref{Pipelines}).
+
+@item --enable-debugger
+Include support for the bash debugger (distributed separately).
+
@item --enable-directory-stack
Include support for a @code{csh}-like directory stack and the
@code{pushd}, @code{popd}, and @code{dirs} builtins
This enables the job control features (@pxref{Job Control}),
if the operating system supports them.
+@item --enable-multibyte
+This enables support for multibyte characters if the operating
+system provides the necessary support.
+
@item --enable-net-redirections
This enables the special handling of filenames of the form
@code{/dev/tcp/@var{host}/@var{port}} and
This enables process substitution (@pxref{Process Substitution}) if
the operating system provides the necessary support.
+@item --enable-progcomp
+Enable the programmable completion facilities
+(@pxref{Programmable Completion}).
+If Readline is not enabled, this option has no effect.
+
@item --enable-prompt-string-decoding
Turn on the interpretation of a number of backslash-escaped characters
in the @env{$PS1}, @env{$PS2}, @env{$PS3}, and @env{$PS4} prompt
strings. See @ref{Printing a Prompt}, for a complete list of prompt
string escape sequences.
-@item --enable-progcomp
-Enable the programmable completion facilities
-(@pxref{Programmable Completion}).
-If Readline is not enabled, this option has no effect.
-
@item --enable-readline
Include support for command-line editing and history with the Bash
version of the Readline library (@pxref{Command Line Editing}).
Include the @code{select} builtin, which allows the generation of simple
menus (@pxref{Conditional Constructs}).
+@item --enable-separate-helpfiles
+Use external files for the documentation displayed by the @code{help} builtin
+instead of storing the text internally.
+
+@item --enable-single-help-strings
+Store the text displayed by the @code{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.
+
+@item --enable-strict-posix-default
+Make Bash @sc{posix}-conformant by default (@pxref{Bash POSIX Mode}).
+
@item --enable-usg-echo-default
A synonym for @code{--enable-xpg-echo-default}.
without requiring the @option{-e} option.
This sets the default value of the @code{xpg_echo} shell option to @code{on},
which makes the Bash @code{echo} behave more like the version specified in
-the Single Unix Specification, version 2.
+the Single Unix Specification, version 3.
@xref{Bash Builtins}, for a description of the escape sequences that
@code{echo} recognizes.
Please report all bugs you find in Bash.
But first, you should
make sure that it really is a bug, and that it appears in the latest
-version of Bash that you have.
+version of Bash.
+The latest version of Bash is always available for FTP from
+@uref{ftp://ftp.gnu.org/pub/bash/}.
Once you have determined that a bug actually exists, use the
@code{bashbug} command to submit a bug report.
Bash implements essentially the same grammar, parameter and
variable expansion, redirection, and quoting as the Bourne Shell.
-Bash uses the @sc{posix} 1003.2 standard as the specification of
+Bash uses the @sc{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 @code{sh} included in SVR4.2 as
-the baseline reference.
+This section uses the version of @code{sh} included in SVR4.2 (the
+last version of the historical Bourne shell) as the baseline reference.
@itemize @bullet
@item
Bash provides a programmable word completion mechanism
-(@pxref{Programmable Completion}), and two builtin commands,
-@code{complete} and @code{compgen}, to manipulate it.
+(@pxref{Programmable Completion}), and builtin commands
+@code{complete}, @code{compgen}, and @code{compopt}, to
+manipulate it.
@item
Bash has command history (@pxref{Bash History Facilities}) and the
@code{history} and @code{fc} builtins to manipulate it.
+The Bash history list maintains timestamp information and uses the
+value of the @code{HISTTIMEFORMAT} variable to display it.
@item
Bash implements @code{csh}-like history expansion
Bash implements the @code{!} keyword to negate the return value of
a pipeline (@pxref{Pipelines}).
Very useful when an @code{if} statement needs to act only if a test fails.
+The Bash @samp{-o pipefail} option to @code{set} will cause a pipeline to
+return a failure status if any command fails.
@item
Bash has the @code{time} reserved word and command timing (@pxref{Pipelines}).
@item
Bash includes the @code{[[} compound command, which makes conditional
-testing part of the shell grammar (@pxref{Conditional Constructs}).
+testing part of the shell grammar (@pxref{Conditional Constructs}), including
+optional regular expression matching.
+
+@item
+Bash provides optional case-insensitive matching for the @code{case} and
+@code{[[} constructs.
@item
Bash includes brace expansion (@pxref{Brace Expansion}) and tilde
command.
@item
+Bash supports the @samp{+=} assignment operator, which appends to the value
+of the variable named on the left hand side.
+
+@item
Bash includes the @sc{posix} pattern removal @samp{%}, @samp{#}, @samp{%%}
and @samp{##} expansions to remove leading or trailing substrings from
variable values (@pxref{Shell Parameter Expansion}).
This closes a longstanding shell security hole.
@item
-Bash implements the full set of @sc{posix} 1003.2 filename expansion operators,
+Bash implements the full set of @sc{posix} filename expansion operators,
including @var{character classes}, @var{equivalence classes}, and
@var{collating symbols} (@pxref{Filename Expansion}).
file (@pxref{Redirections}).
@item
+Bash includes the @samp{<<<} redirection operator, allowing a string to
+be used as the standard input to a command.
+
+@item
+Bash implements the @samp{[n]<&@var{word}} and @samp{[n]>&@var{word}}
+redirection operators, which move one file descriptor to another.
+
+@item
Bash treats a number of filenames specially when they are
used in redirection operators (@pxref{Redirections}).
@item
Bash includes the @code{shopt} builtin, for finer control of shell
-optional capabilities (@pxref{Bash Builtins}), and allows these options
+optional capabilities (@pxref{The Shopt Builtin}), and allows these options
to be set and unset at shell invocation (@pxref{Invoking Bash}).
@item
builtin (@pxref{The Set Builtin}).
@item
+The @samp{-x} (@code{xtrace}) option displays commands other than
+simple commands when performing an execution trace
+(@pxref{The Set Builtin}).
+
+@item
The @code{test} builtin (@pxref{Bourne Shell Builtins})
is slightly different, as it implements the @sc{posix} algorithm,
which specifies the behavior based on the number of arguments.
@item
+Bash includes the @code{caller} builtin, which displays the context of
+any active subroutine call (a shell function or a script executed with
+the @code{.} or @code{source} builtins). This supports the bash
+debugger.
+
+@item
The @code{trap} builtin (@pxref{Bourne Shell Builtins}) allows a
@code{DEBUG} pseudo-signal specification, similar to @code{EXIT}.
-Commands specified with a @code{DEBUG} trap are executed after every
-simple command.
-The @code{DEBUG} trap is not inherited by shell functions.
+Commands specified with a @code{DEBUG} trap are executed before every
+simple command, @code{for} command, @code{case} command,
+@code{select} command, every arithmetic @code{for} command, and before
+the first command executes in a shell function.
+The @code{DEBUG} trap is not inherited by shell functions unless the
+function has been given the @code{trace} attribute or the
+@code{functrace} option has been enabled using the @code{shopt} builtin.
+The @code{extdebug} shell option has additional effects on the
+@code{DEBUG} trap.
The @code{trap} builtin (@pxref{Bourne Shell Builtins}) allows an
@code{ERR} pseudo-signal specification, similar to @code{EXIT} and @code{DEBUG}.
Commands specified with an @code{ERR} trap are executed after a simple
command fails, with a few exceptions.
-The @code{ERR} trap is not inherited by shell functions.
+The @code{ERR} trap is not inherited by shell functions unless the
+@code{-o errtrace} option to the @code{set} builtin is enabled.
+
+The @code{trap} builtin (@pxref{Bourne Shell Builtins}) allows a
+@code{RETURN} pseudo-signal specification, similar to
+@code{EXIT} and @code{DEBUG}.
+Commands specified with an @code{RETURN} trap are executed before
+execution resumes after a shell function or a shell script executed with
+@code{.} or @code{source} returns.
+The @code{RETURN} trap is not inherited by shell functions unless the
+function has been given the @code{trace} attribute or the
+@code{functrace} option has been enabled using the @code{shopt} builtin.
@item
The Bash @code{type} builtin is more extensive and gives more information
@code{SIGHUP}.
@item
+Bash includes a number of features to support a separate debugger for
+shell scripts.
+
+@item
The SVR4.2 shell has two privilege-related builtins
(@code{mldmode} and @code{priv}) not present in Bash.
@item
The SVR4.2 shell exits a script if any builtin fails; Bash exits
-a script only if one of the @sc{posix} 1003.2 special builtins fails, and
-only for certain failures, as enumerated in the @sc{posix} 1003.2 standard.
+a script only if one of the @sc{posix} special builtins fails, and
+only for certain failures, as enumerated in the @sc{posix} standard.
@item
The SVR4.2 shell behaves differently when invoked as @code{jsh}
(it turns on job control).
@end itemize
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
+
+@include fdl.texi
+
+@node Indexes
+@appendix 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.
+@end menu
+
@node Builtin Index
-@unnumbered Index of Shell Builtin Commands
+@appendixsec Index of Shell Builtin Commands
@printindex bt
@node Reserved Word Index
-@unnumbered Index of Shell Reserved Words
+@appendixsec Index of Shell Reserved Words
@printindex rw
@node Variable Index
-@unnumbered Parameter and Variable Index
+@appendixsec Parameter and Variable Index
@printindex vr
@node Function Index
-@unnumbered Function Index
+@appendixsec Function Index
@printindex fn
@node Concept Index
-@unnumbered Concept Index
+@appendixsec Concept Index
@printindex cp
-@contents
@bye
projects / platform / upstream / bash.git / blobdiff