Adding upstream version 5.1.upstream/5.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.\"
+.\" MAN PAGE COMMENTS to
+.\"
+.\"	Chet Ramey
+.\"	Case Western Reserve University
+.\"	chet.ramey@case.edu
+.\"
+.\"	Last Change: Wed Sep 23 09:28:31 EDT 2020
+.\"
+.\" bash_builtins, strip all but Built-Ins section
+.if \n(zZ=1 .ig zZ
+.if \n(zY=1 .ig zY
+.TH BASH 1 "2020 October 29" "GNU Bash 5.1"
+.\"
+.\" There's some problem with having a `@'
+.\" in a tagged paragraph with the BSD man macros.
+.\" It has to do with `@' appearing in the }1 macro.
+.\" This is a problem on 4.3 BSD and Ultrix, but Sun
+.\" appears to have fixed it.
+.\" If you're seeing the characters
+.\" `@u-3p' appearing before the lines reading
+.\" `possible-hostname-completions
+.\" and `complete-hostname' down in READLINE,
+.\" then uncomment this redefinition.
+.\"
+.\" .de }1
+.\" .ds ]X \&\\*(]B\\
+.\" .nr )E 0
+.\" .if !"\\$1"" .nr )I \\$1n
+.\" .}f
+.\" .ll \\n(LLu
+.\" .in \\n()Ru+\\n(INu+\\n()Iu
+.\" .ti \\n(INu
+.\" .ie !\\n()Iu+\\n()Ru-\w\\*(]Xu-3p \{\\*(]X
+.\" .br\}
+.\" .el \\*(]X\h|\\n()Iu+\\n()Ru\c
+.\" .}f
+.\" ..
+.\"
+.\" File Name macro.  This used to be `.PN', for Path Name,
+.\" but Sun doesn't seem to like that very much.
+.\"
+.de FN
+\fI\|\\$1\|\fP
+..
+.SH NAME
+bash \- GNU Bourne-Again SHell
+.SH SYNOPSIS
+.B bash
+[options]
+[command_string | file]
+.SH COPYRIGHT
+.if n Bash is Copyright (C) 1989-2020 by the Free Software Foundation, Inc.
+.if t Bash is Copyright \(co 1989-2020 by the Free Software Foundation, Inc.
+.SH DESCRIPTION
+.B Bash
+is an \fBsh\fR-compatible command language interpreter that
+executes commands read from the standard input or from a file.
+.B Bash
+also incorporates useful features from the \fIKorn\fP and \fIC\fP
+shells (\fBksh\fP and \fBcsh\fP).
+.PP
+.B Bash
+is intended to be a conformant implementation of the
+Shell and Utilities portion of the IEEE POSIX specification
+(IEEE Standard 1003.1).
+.B Bash
+can be configured to be POSIX-conformant by default.
+.SH OPTIONS
+All of the single-character shell options documented in the
+description of the \fBset\fR builtin command, including \fB\-o\fP,
+can be used as options when the shell is invoked.
+In addition, \fBbash\fR
+interprets the following options when it is invoked:
+.PP
+.PD 0
+.TP 10
+.B \-c
+If the
+.B \-c
+option is present, then commands are read from the first non-option argument
+.IR command_string .
+If there are arguments after the
+.IR command_string ,
+the first argument is assigned to
+.B $0
+and any remaining arguments are assigned to the positional parameters.
+The assignment to
+.B $0
+sets the name of the shell, which is used in warning and error messages.
+.TP
+.B \-i
+If the
+.B \-i
+option is present, the shell is
+.IR interactive .
+.TP
+.B \-l
+Make
+.B bash
+act as if it had been invoked as a login shell (see
+.SM
+.B INVOCATION
+below).
+.TP
+.B \-r
+If the
+.B \-r
+option is present, the shell becomes
+.I restricted
+(see
+.SM
+.B "RESTRICTED SHELL"
+below).
+.TP
+.B \-s
+If the
+.B \-s
+option is present, or if no arguments remain after option
+processing, then commands are read from the standard input.
+This option allows the positional parameters to be set
+when invoking an interactive shell or when reading input
+through a pipe.
+.TP
+.B \-D
+A list of all double-quoted strings preceded by \fB$\fP
+is printed on the standard output.
+These are the strings that
+are subject to language translation when the current locale
+is not \fBC\fP or \fBPOSIX\fP.
+This implies the \fB\-n\fP option; no commands will be executed.
+.TP
+.B [\-+]O [\fIshopt_option\fP]
+\fIshopt_option\fP is one of the shell options accepted by the
+\fBshopt\fP builtin (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
+\fB+O\fP unsets it.
+If \fIshopt_option\fP is not supplied, the names and values of the shell
+options accepted by \fBshopt\fP are printed on the standard output.
+If the invocation option is \fB+O\fP, the output is displayed in a format
+that may be reused as input.
+.TP
+.B \-\-
+A
+.B \-\-
+signals the end of options and disables further option processing.
+Any arguments after the
+.B \-\-
+are treated as filenames and arguments.  An argument of
+.B \-
+is equivalent to \fB\-\-\fP.
+.PD
+.PP
+.B Bash
+also interprets a number of multi-character options.
+These options must appear on the command line before the
+single-character options to be recognized.
+.PP
+.PD 0
+.TP
+.B \-\-debugger
+Arrange for the debugger profile to be executed before the shell
+starts.
+Turns on extended debugging mode (see the description of the
+.B extdebug
+option to the
+.B shopt
+builtin below).
+.TP
+.B \-\-dump\-po\-strings
+Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
+\fBpo\fP (portable object) file format.
+.TP
+.B \-\-dump\-strings
+Equivalent to \fB\-D\fP.
+.TP
+.B \-\-help
+Display a usage message on standard output and exit successfully.
+.TP
+\fB\-\-init\-file\fP \fIfile\fP
+.PD 0
+.TP
+\fB\-\-rcfile\fP \fIfile\fP
+.PD
+Execute commands from
+.I file
+instead of the standard personal initialization file
+.I ~/.bashrc
+if the shell is interactive (see
+.SM
+.B INVOCATION
+below).
+.TP
+.B \-\-login
+Equivalent to \fB\-l\fP.
+.TP
+.B \-\-noediting
+Do not use the GNU
+.B readline
+library to read command lines when the shell is interactive.
+.TP
+.B \-\-noprofile
+Do not read either the system-wide startup file
+.FN /etc/profile
+or any of the personal initialization files
+.IR ~/.bash_profile ,
+.IR ~/.bash_login ,
+or
+.IR ~/.profile .
+By default,
+.B bash
+reads these files when it is invoked as a login shell (see
+.SM
+.B INVOCATION
+below).
+.TP
+.B \-\-norc
+Do not read and execute the personal initialization file
+.I ~/.bashrc
+if the shell is interactive.
+This option is on by default if the shell is invoked as
+.BR sh .
+.TP
+.B \-\-posix
+Change the behavior of \fBbash\fP where the default operation differs
+from the POSIX standard to match the standard (\fIposix mode\fP).
+See
+.SM
+.B "SEE ALSO"
+below for a reference to a document that details how posix mode affects
+bash's behavior.
+.TP
+.B \-\-restricted
+The shell becomes restricted (see
+.SM
+.B "RESTRICTED SHELL"
+below).
+.TP
+.B \-\-verbose
+Equivalent to \fB\-v\fP.
+.TP
+.B \-\-version
+Show version information for this instance of
+.B bash
+on the standard output and exit successfully.
+.PD
+.SH ARGUMENTS
+If arguments remain after option processing, and neither the
+.B \-c
+nor the
+.B \-s
+option has been supplied, the first argument is assumed to
+be the name of a file containing shell commands.
+If
+.B bash
+is invoked in this fashion,
+.B $0
+is set to the name of the file, and the positional parameters
+are set to the remaining arguments.
+.B Bash
+reads and executes commands from this file, then exits.
+\fBBash\fP's exit status is the exit status of the last command
+executed in the script.
+If no commands are executed, the exit status is 0.
+An attempt is first made to open the file in the current directory, and,
+if no file is found, then the shell searches the directories in
+.SM
+.B PATH
+for the script.
+.SH INVOCATION
+A \fIlogin shell\fP is one whose first character of argument zero is a
+.BR \- ,
+or one started with the
+.B \-\-login
+option.
+.PP
+An \fIinteractive\fP shell is one started without non-option arguments
+(unless \fB\-s\fP is specified)
+and without the
+.B \-c
+option
+whose standard input and error are
+both connected to terminals (as determined by
+.IR isatty (3)),
+or one started with the
+.B \-i
+option.
+.SM
+.B PS1
+is set and
+.B $\-
+includes
+.B i
+if
+.B bash
+is interactive,
+allowing a shell script or a startup file to test this state.
+.PP
+The following paragraphs describe how
+.B bash
+executes its startup files.
+If any of the files exist but cannot be read,
+.B bash
+reports an error.
+Tildes are expanded in filenames as described below under
+.B "Tilde Expansion"
+in the
+.SM
+.B EXPANSION
+section.
+.PP
+When
+.B bash
+is invoked as an interactive login shell, or as a non-interactive shell
+with the \fB\-\-login\fP option, it first reads and
+executes commands from the file \fI/etc/profile\fP, if that
+file exists.
+After reading that file, it looks for \fI~/.bash_profile\fP,
+\fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
+and executes commands from the first one that exists and is readable.
+The
+.B \-\-noprofile
+option may be used when the shell is started to inhibit this behavior.
+.PP
+When an interactive login shell exits,
+or a non-interactive login shell executes the \fBexit\fP builtin command,
+.B bash
+reads and executes commands from the file \fI~/.bash_logout\fP, if it
+exists.
+.PP
+When an interactive shell that is not a login shell is started,
+.B bash
+reads and executes commands from \fI~/.bashrc\fP, if that file exists.
+This may be inhibited by using the
+.B \-\-norc
+option.
+The \fB\-\-rcfile\fP \fIfile\fP option will force
+.B bash
+to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
+.PP
+When
+.B bash
+is started non-interactively, to run a shell script, for example, it
+looks for the variable
+.SM
+.B BASH_ENV
+in the environment, expands its value if it appears there, and uses the
+expanded value as the name of a file to read and execute.
+.B Bash
+behaves as if the following command were executed:
+.sp .5
+.RS
+.if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
+.if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
+.RE
+.sp .5
+but the value of the
+.SM
+.B PATH
+variable is not used to search for the filename.
+.PP
+If
+.B bash
+is invoked with the name
+.BR sh ,
+it tries to mimic the startup behavior of historical versions of
+.B sh
+as closely as possible,
+while conforming to the POSIX standard as well.
+When invoked as an interactive login shell, or a non-interactive
+shell with the \fB\-\-login\fP option, it first attempts to
+read and execute commands from
+.I /etc/profile
+and
+.IR ~/.profile ,
+in that order.
+The
+.B \-\-noprofile
+option may be used to inhibit this behavior.
+When invoked as an interactive shell with the name
+.BR sh ,
+.B bash
+looks for the variable
+.SM
+.BR ENV ,
+expands its value if it is defined, and uses the
+expanded value as the name of a file to read and execute.
+Since a shell invoked as
+.B sh
+does not attempt to read and execute commands from any other startup
+files, the
+.B \-\-rcfile
+option has no effect.
+A non-interactive shell invoked with the name
+.B sh
+does not attempt to read any other startup files.
+When invoked as
+.BR sh ,
+.B bash
+enters
+.I posix
+mode after the startup files are read.
+.PP
+When
+.B bash
+is started in
+.I posix
+mode, as with the
+.B \-\-posix
+command line option, it follows the POSIX standard for startup files.
+In this mode, interactive shells expand the
+.SM
+.B ENV
+variable and commands are read and executed from the file
+whose name is the expanded value.
+No other startup files are read.
+.PP
+.B Bash
+attempts to determine when it is being run with its standard input
+connected to a network connection, as when executed by the remote shell
+daemon, usually \fIrshd\fP, or the secure shell daemon \fIsshd\fP.
+If
+.B bash
+determines it is being run in this fashion, it reads and executes
+commands from \fI~/.bashrc\fP, if that file exists and is readable.
+It will not do this if invoked as \fBsh\fP.
+The
+.B \-\-norc
+option may be used to inhibit this behavior, and the
+.B \-\-rcfile
+option may be used to force another file to be read, but neither
+\fIrshd\fP nor \fIsshd\fP generally invoke the shell with those options
+or allow them to be specified.
+.PP
+If the shell is started with the effective user (group) id not equal to the
+real user (group) id, and the \fB\-p\fP option is not supplied, no startup
+files are read, shell functions are not inherited from the environment, the
+.SM
+.BR SHELLOPTS ,
+.SM
+.BR BASHOPTS ,
+.SM
+.BR CDPATH ,
+and
+.SM
+.B GLOBIGNORE
+variables, if they appear in the environment, are ignored,
+and the effective user id is set to the real user id.
+If the \fB\-p\fP option is supplied at invocation, the startup behavior is
+the same, but the effective user id is not reset.
+.SH DEFINITIONS
+The following definitions are used throughout the rest of this
+document.
+.PD 0
+.TP
+.B blank
+A space or tab.
+.TP
+.B word
+A sequence of characters considered as a single unit by the shell.
+Also known as a
+.BR token .
+.TP
+.B name
+A
+.I word
+consisting only of alphanumeric characters and underscores, and
+beginning with an alphabetic character or an underscore.  Also
+referred to as an
+.BR identifier .
+.TP
+.B metacharacter
+A character that, when unquoted, separates words.  One of the following:
+.br
+.RS
+.PP
+.if t \fB|  &  ;  (  )  <  >  space  tab  newline\fP
+.if n \fB|  & ; ( ) < > space tab newline\fP
+.RE
+.TP
+.B control operator
+A \fItoken\fP that performs a control function.  It is one of the following
+symbols:
+.RS
+.PP
+.if t \fB||  &  &&  ;  ;;  ;&  ;;&  (  )  |  |&    <newline>\fP
+.if n \fB|| & && ; ;; ;& ;;& ( ) | |& <newline>\fP
+.RE
+.PD
+.SH "RESERVED WORDS"
+\fIReserved words\fP are words that have a special meaning to the shell.
+The following words are recognized as reserved when unquoted and either
+the first word of a command (see
+.SM
+.B SHELL GRAMMAR
+below), the third word of a
+.B case
+or
+.B select
+command
+(only \fBin\fP is valid), or the third word of a
+.B for
+command (only \fBin\fP and \fBdo\fP are valid):
+.if t .RS
+.PP
+.B
+.if n ! case  coproc  do done elif else esac fi for function if in select then until while { } time [[ ]]
+.if t !    case    coproc    do    done    elif    else    esac    fi    for    function    if    in    select    then    until    while    {    }    time    [[    ]]
+.if t .RE
+.SH "SHELL GRAMMAR"
+.SS Simple Commands
+A \fIsimple command\fP is a sequence of optional variable assignments
+followed by \fBblank\fP-separated words and redirections, and
+terminated by a \fIcontrol operator\fP.  The first word
+specifies the command to be executed, and is passed as argument zero.
+The remaining words are passed as arguments to the invoked command.
+.PP
+The return value of a \fIsimple command\fP is its exit status, or
+128+\fIn\^\fP if the command is terminated by signal
+.IR n .
+.SS Pipelines
+A \fIpipeline\fP is a sequence of one or more commands separated by
+one of the control operators
+.B |
+or \fB|&\fP.
+The format for a pipeline is:
+.RS
+.PP
+[\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ [\fB|\fP\(bv\fB|&\fP] \fIcommand2\fP ... ]
+.RE
+.PP
+The standard output of
+.I command
+is connected via a pipe to the standard input of
+.IR command2 .
+This connection is performed before any redirections specified by the
+command (see
+.SM
+.B REDIRECTION
+below).
+If \fB|&\fP is used, \fIcommand\fP's standard error, in addition to its
+standard output, is connected to
+\fIcommand2\fP's standard input through the pipe;
+it is shorthand for \fB2>&1 |\fP.
+This implicit redirection of the standard error to the standard output is
+performed after any redirections specified by the command.
+.PP
+The return status of a pipeline is the exit status of the last
+command, unless the \fBpipefail\fP option is enabled.
+If \fBpipefail\fP 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
+.B !
+precedes a pipeline, the exit status of that pipeline 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.
+.PP
+If the
+.B time
+reserved word precedes a pipeline, the elapsed as well as user and
+system time consumed by its execution are reported when the pipeline
+terminates.
+The \fB\-p\fP option changes the output format to that specified by POSIX.
+When the shell is in \fIposix mode\fP, it does not recognize
+\fBtime\fP as a reserved word if the next token begins with a `-'.
+The
+.SM
+.B TIMEFORMAT
+variable may be set to a format string that specifies how the timing
+information should be displayed; see the description of
+.SM
+.B TIMEFORMAT
+under
+.B "Shell Variables"
+below.
+.PP
+When the shell is in \fIposix mode\fP, \fBtime\fP
+may be followed by a newline.  In this case, the shell displays the
+total user and system time consumed by the shell and its children.
+The
+.SM
+.B TIMEFORMAT
+variable may be used to specify the format of
+the time information.
+.PP
+Each command in a pipeline is executed as a separate process (i.e., in a
+subshell).
+See
+.SM
+\fBCOMMAND EXECUTION ENVIRONMENT\fP
+for a description of a subshell environment.
+If the \fBlastpipe\fP option is enabled using the \fBshopt\fP builtin
+(see the description of \fBshopt\fP below),
+the last element of a pipeline may be run by the shell process.
+.SS Lists
+A \fIlist\fP is a sequence of one or more pipelines separated by one
+of the operators
+.BR ; ,
+.BR & ,
+.BR && ,
+or
+.BR || ,
+and optionally terminated by one of
+.BR ; ,
+.BR & ,
+or
+.BR <newline> .
+.PP
+Of these list operators,
+.B &&
+and
+.B ||
+have equal precedence, followed by
+.B ;
+and
+.BR & ,
+which have equal precedence.
+.PP
+A sequence of one or more newlines may appear in a \fIlist\fP instead
+of a semicolon to delimit commands.
+.PP
+If a command is terminated by the control operator
+.BR & ,
+the shell executes the command in the \fIbackground\fP
+in a subshell.
+The shell does not wait for the command to
+finish, and the return status is 0.
+These are referred to as \fIasynchronous\fP commands.
+Commands separated by a
+.B ;
+are executed sequentially; the shell waits for each
+command to terminate in turn.  The return status is the
+exit status of the last command executed.
+.PP
+AND and OR lists are sequences of one or more pipelines separated by the
+\fB&&\fP and \fB||\fP control operators, respectively.
+AND and OR lists are executed with left associativity.
+An AND list has the form
+.RS
+.PP
+\fIcommand1\fP \fB&&\fP \fIcommand2\fP
+.RE
+.PP
+.I command2
+is executed if, and only if,
+.I command1
+returns an exit status of zero (success).
+.PP
+An OR list has the form
+.RS
+.PP
+\fIcommand1\fP \fB||\fP \fIcommand2\fP
+.RE
+.PP
+.I command2
+is executed if, and only if,
+.I command1
+returns a non-zero exit status.
+The return status of
+AND and OR lists is the exit status of the last command
+executed in the list.
+.SS Compound Commands
+A \fIcompound command\fP is one of the following.
+In most cases a \fIlist\fP in a command's description may be separated from
+the rest of the command by one or more newlines, and may be followed by a
+newline in place of a semicolon.
+.TP
+(\fIlist\fP)
+\fIlist\fP is executed in a subshell environment (see
+.SM
+\fBCOMMAND EXECUTION ENVIRONMENT\fP
+below).
+Variable assignments and builtin
+commands that affect the shell's environment do not remain in effect
+after the command completes.  The return status is the exit status of
+\fIlist\fP.
+.TP
+{ \fIlist\fP; }
+\fIlist\fP is simply executed in the current shell environment.
+\fIlist\fP must be terminated with a newline or semicolon.
+This is known as a \fIgroup command\fP.
+The return status is the exit status of
+\fIlist\fP.
+Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
+\fB}\fP are \fIreserved words\fP and must occur where a reserved
+word is permitted to be recognized.  Since they do not cause a word
+break, they must be separated from \fIlist\fP by whitespace or another
+shell metacharacter.
+.TP
+((\fIexpression\fP))
+The \fIexpression\fP is evaluated according to the rules described
+below under
+.SM
+.BR "ARITHMETIC EVALUATION" .
+If the value of the expression is non-zero, the return status is 0;
+otherwise the return status is 1.  This is exactly equivalent to
+\fBlet "\fIexpression\fP"\fR.
+.TP
+\fB[[\fP \fIexpression\fP \fB]]\fP
+Return a status of 0 or 1 depending on the evaluation of
+the conditional expression \fIexpression\fP.
+Expressions are composed of the primaries described below under
+.SM
+.BR "CONDITIONAL EXPRESSIONS" .
+Word splitting and pathname expansion are not performed on the words
+between the \fB[[\fP and \fB]]\fP; tilde expansion,
+parameter and variable expansion,
+arithmetic expansion, command substitution, process
+substitution, and quote removal are performed.
+Conditional operators such as \fB\-f\fP must be unquoted to be recognized
+as primaries.
+.if t .sp 0.5
+.if n .sp 1
+When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
+lexicographically using the current locale.
+.if t .sp 0.5
+.if n .sp 1
+When the \fB==\fP and \fB!=\fP operators are used, the string to the
+right of the operator is considered a pattern and matched according
+to the rules described below under \fBPattern Matching\fP,
+as if the \fBextglob\fP shell option were enabled.
+The \fB=\fP operator is equivalent to \fB==\fP.
+If the
+.B nocasematch
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+The return value is 0 if the string matches (\fB==\fP) or does not match
+(\fB!=\fP) the pattern, and 1 otherwise.
+Any part of the pattern may be quoted to force the quoted portion
+to be matched as a string.
+.if t .sp 0.5
+.if n .sp 1
+An additional binary operator, \fB=~\fP, is available, with the same
+precedence as \fB==\fP and \fB!=\fP.
+When it is used, the string to the right of the operator is considered
+a POSIX extended regular expression and matched accordingly
+(using the POSIX \fIregcomp\fP and \fIregexec\fP interfaces
+usually described in \fIregex\fP(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
+.B nocasematch
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+Any part of the pattern may be quoted to force the quoted portion
+to be matched as a string.
+Bracket expressions in regular expressions must be treated carefully,
+since normal quoting characters lose their meanings between brackets.
+If the pattern is stored in a shell variable, quoting the variable
+expansion forces the entire pattern to be matched as a string.
+.if t .sp 0.5
+.if n .sp 1
+The pattern will match if it matches any part of the string.
+Anchor the pattern using the \fB^\fP and \fB$\fP regular expression
+operators to force it to match the entire string.
+The array variable
+.SM
+.B BASH_REMATCH
+records which parts of the string matched the pattern.
+The element of
+.SM
+.B BASH_REMATCH
+with index 0 contains the portion of
+the string matching the entire regular expression.
+Substrings matched by parenthesized subexpressions within the regular
+expression are saved in the remaining
+.SM
+.B BASH_REMATCH
+indices. The element of
+.SM
+.B BASH_REMATCH
+with index \fIn\fP is the portion of the
+string matching the \fIn\fPth parenthesized subexpression.
+.if t .sp 0.5
+.if n .sp 1
+Expressions may be combined using the following operators, listed
+in decreasing order of precedence:
+.if t .sp 0.5
+.if n .sp 1
+.RS
+.PD 0
+.TP
+.B ( \fIexpression\fP )
+Returns the value of \fIexpression\fP.
+This may be used to override the normal precedence of operators.
+.TP
+.B ! \fIexpression\fP
+True if
+.I expression
+is false.
+.TP
+\fIexpression1\fP \fB&&\fP \fIexpression2\fP
+True if both
+.I expression1
+and
+.I expression2
+are true.
+.TP
+\fIexpression1\fP \fB||\fP \fIexpression2\fP
+True if either
+.I expression1
+or
+.I expression2
+is true.
+.PD
+.LP
+The \fB&&\fP and \fB||\fP
+operators do not evaluate \fIexpression2\fP if the value of
+\fIexpression1\fP is sufficient to determine the return value of
+the entire conditional expression.
+.RE
+.TP
+\fBfor\fP \fIname\fP [ [ \fBin\fP [ \fIword ...\fP ] ] ; ] \fBdo\fP \fIlist\fP ; \fBdone\fP
+The list of words following \fBin\fP is expanded, generating a list
+of items.
+The variable \fIname\fP is set to each element of this list
+in turn, and \fIlist\fP is executed each time.
+If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
+\fIlist\fP once for each positional parameter that is set (see
+.SM
+.B PARAMETERS
+below).
+The return status is the exit status of the last command that executes.
+If the expansion of the items following \fBin\fP results in an empty
+list, no commands are executed, and the return status is 0.
+.TP
+\fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
+First, the arithmetic expression \fIexpr1\fP is evaluated according
+to the rules described below under
+.SM
+.BR "ARITHMETIC EVALUATION" .
+The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
+until it evaluates to zero.
+Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
+executed and the arithmetic expression \fIexpr3\fP is evaluated.
+If any expression is omitted, it behaves as if it evaluates to 1.
+The return value is the exit status of the last command in \fIlist\fP
+that is executed, or false if any of the expressions is invalid.
+.TP
+\fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
+The list of words following \fBin\fP is expanded, generating a list
+of items.  The set of expanded words is printed on the standard
+error, each preceded by a number.  If the \fBin\fP
+\fIword\fP is omitted, the positional parameters are printed (see
+.SM
+.B PARAMETERS
+below).  The
+.SM
+.B PS3
+prompt is then displayed and a line read from the standard input.
+If the line consists of a number corresponding to one of
+the displayed words, then the value of
+.I name
+is set to that word.  If the line is empty, the words and prompt
+are displayed again.  If EOF is read, the command completes.  Any
+other value read causes
+.I name
+to be set to null.  The line read is saved in the variable
+.SM
+.BR REPLY .
+The
+.I list
+is executed after each selection until a
+.B break
+command is executed.
+The exit status of
+.B select
+is the exit status of the last command executed in
+.IR list ,
+or zero if no commands were executed.
+.TP
+\fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
+... ) \fIlist\fP ;; ] ... \fBesac\fP
+A \fBcase\fP command first expands \fIword\fP, and tries to match
+it against each \fIpattern\fP in turn, using the matching rules
+described under
+.B Pattern Matching
+below.
+The \fIword\fP is expanded using tilde
+expansion, parameter and variable expansion, arithmetic expansion,
+command substitution, process substitution and quote removal.
+Each \fIpattern\fP examined is expanded using tilde
+expansion, parameter and variable expansion, arithmetic expansion,
+command substitution, and process substitution.
+If the
+.B nocasematch
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+When a match is found, the corresponding \fIlist\fP is executed.
+If the \fB;;\fP operator is used, no subsequent matches are attempted after
+the first pattern match.
+Using \fB;&\fP in place of \fB;;\fP causes execution to continue with
+the \fIlist\fP associated with the next set of patterns.
+Using \fB;;&\fP in place of \fB;;\fP causes the shell to test the next
+pattern list in the statement, if any, and execute any associated \fIlist\fP
+on a successful match,
+continuing the case statement execution as if the pattern list had not matched.
+The exit status is zero if no
+pattern matches.  Otherwise, it is the exit status of the
+last command executed in \fIlist\fP.
+.TP
+\fBif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; \
+[ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
+[ \fBelse\fP \fIlist\fP; ] \fBfi\fP
+The
+.B if
+.I list
+is executed.  If its exit status is zero, the
+\fBthen\fP \fIlist\fP is executed.  Otherwise, each \fBelif\fP
+\fIlist\fP is executed in turn, and if its exit status is zero,
+the corresponding \fBthen\fP \fIlist\fP is executed and the
+command completes.  Otherwise, the \fBelse\fP \fIlist\fP is
+executed, if present.  The exit status is the exit status of the
+last command executed, or zero if no condition tested true.
+.TP
+\fBwhile\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
+.PD 0
+.TP
+\fBuntil\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
+.PD
+The \fBwhile\fP command continuously executes the list
+\fIlist-2\fP as long as the last command in the list \fIlist-1\fP returns
+an exit status of zero.  The \fBuntil\fP command is identical
+to the \fBwhile\fP command, except that the test is negated:
+.I list-2
+is executed as long as the last command in
+.I list-1
+returns a non-zero exit status.
+The exit status of the \fBwhile\fP and \fBuntil\fP commands
+is the exit status
+of the last command executed in \fIlist-2\fP, or zero if
+none was executed.
+.SS Coprocesses
+A \fIcoprocess\fP is a shell command preceded by the \fBcoproc\fP reserved
+word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the \fB&\fP control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+.PP
+The format for a coprocess is:
+.RS
+.PP
+\fBcoproc\fP [\fINAME\fP] \fIcommand\fP [\fIredirections\fP]
+.RE
+.PP
+This creates a coprocess named \fINAME\fP.
+If \fINAME\fP is not supplied, the default name is \fBCOPROC\fP.
+\fINAME\fP must not be supplied if \fIcommand\fP is a \fIsimple
+command\fP (see above); otherwise, it is interpreted as the first word
+of the simple command.
+When the coprocess is executed, the shell creates an array variable (see
+.B Arrays
+below) named \fINAME\fP in the context of the executing shell.
+The standard output of
+.I command
+is connected via a pipe to a file descriptor in the executing shell,
+and that file descriptor is assigned to \fINAME\fP[0].
+The standard input of
+.I command
+is connected via a pipe to a file descriptor in the executing shell,
+and that file descriptor is assigned to \fINAME\fP[1].
+This pipe is established before any redirections specified by the
+command (see
+.SM
+.B REDIRECTION
+below).
+The file descriptors can be utilized as arguments to shell commands
+and redirections using standard word expansions.
+Other than those created to execute command and process substitutions,
+the file descriptors are not available in subshells.
+The process ID of the shell spawned to execute the coprocess is
+available as the value of the variable \fINAME\fP_PID.
+The \fBwait\fP
+builtin command may be used to wait for the coprocess to terminate.
+.PP
+Since the coprocess is created as an asynchronous command,
+the \fBcoproc\fP command always returns success.
+The return status of a coprocess is the exit status of \fIcommand\fP.
+.SS Shell Function Definitions
+A shell function is an object that is called like a simple command and
+executes a compound command with a new set of positional parameters.
+Shell functions are declared as follows:
+.TP
+\fIfname\fP () \fIcompound\-command\fP [\fIredirection\fP]
+.PD 0
+.TP
+\fBfunction\fP \fIfname\fP [()] \fIcompound\-command\fP [\fIredirection\fP]
+.PD
+This defines a function named \fIfname\fP.
+The reserved word \fBfunction\fP is optional.
+If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
+The \fIbody\fP of the function is the compound command
+.I compound\-command
+(see \fBCompound Commands\fP above).
+That command is usually a \fIlist\fP of commands between { and }, but
+may be any command listed under \fBCompound Commands\fP above,
+with one exception: If the \fBfunction\fP reserved word is used, but the
+parentheses are not supplied, the braces are required.
+\fIcompound\-command\fP is executed whenever \fIfname\fP is specified as the
+name of a simple command.
+When in \fIposix mode\fP, \fIfname\fP must be a valid shell \fIname\fP
+and may not be the name of one of the
+POSIX \fIspecial builtins\fP.
+In default mode, a function name can be any unquoted shell word that does
+not contain \fB$\fP.
+Any redirections (see
+.SM
+.B REDIRECTION
+below) specified when a function is defined are performed
+when the function is executed.
+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.  (See
+.SM
+.B FUNCTIONS
+below.)
+.SH COMMENTS
+In a non-interactive shell, or an interactive shell in which the
+.B interactive_comments
+option to the
+.B shopt
+builtin is enabled (see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below), a word beginning with
+.B #
+causes that word and all remaining characters on that line to
+be ignored.  An interactive shell without the
+.B interactive_comments
+option enabled does not allow comments.  The
+.B interactive_comments
+option is on by default in interactive shells.
+.SH QUOTING
+\fIQuoting\fP is used to remove the special meaning of certain
+characters or words to the shell.  Quoting can be used to
+disable special treatment for special characters, to prevent
+reserved words from being recognized as such, and to prevent
+parameter expansion.
+.PP
+Each of the \fImetacharacters\fP listed above under
+.SM
+.B DEFINITIONS
+has special meaning to the shell and must be quoted if it is to
+represent itself.
+.PP
+When the command history expansion facilities are being used
+(see
+.SM
+.B HISTORY EXPANSION
+below), the
+\fIhistory expansion\fP character, usually \fB!\fP, must be quoted
+to prevent history expansion.
+.PP
+There are three quoting mechanisms: the
+.IR "escape character" ,
+single quotes, and double quotes.
+.PP
+A non-quoted backslash (\fB\e\fP) is the
+.IR "escape character" .
+It preserves the literal value of the next character that follows,
+with the exception of <newline>.  If a \fB\e\fP<newline> pair
+appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
+is treated as a line continuation (that is, it is removed from the
+input stream and effectively ignored).
+.PP
+Enclosing characters in single quotes preserves the literal value
+of each character within the quotes.  A single quote may not occur
+between single quotes, even when preceded by a backslash.
+.PP
+Enclosing characters in double quotes preserves the literal value
+of all characters within the quotes, with the exception of
+.BR $ ,
+.BR \` ,
+.BR \e ,
+and, when history expansion is enabled,
+.BR ! .
+When the shell is in \fIposix mode\fP, the \fB!\fP has no special meaning
+within double quotes, even when history expansion is enabled.
+The characters
+.B $
+and
+.B \`
+retain their special meaning within double quotes.  The backslash
+retains its special meaning only when followed by one of the following
+characters:
+.BR $ ,
+.BR \` ,
+\^\fB"\fP\^,
+.BR \e ,
+or
+.BR <newline> .
+A double quote may be quoted within double quotes by preceding it with
+a backslash.
+If enabled, history expansion will be performed unless an
+.B !
+appearing in double quotes is escaped using a backslash.
+The backslash preceding the
+.B !
+is not removed.
+.PP
+The special parameters
+.B *
+and
+.B @
+have special meaning when in double
+quotes (see
+.SM
+.B PARAMETERS
+below).
+.PP
+Words of the form \fB$\fP\(aq\fIstring\fP\(aq are treated specially.  The
+word expands to \fIstring\fP, with backslash-escaped characters replaced
+as specified by the ANSI C standard.  Backslash escape sequences, if
+present, are decoded as follows:
+.RS
+.PD 0
+.TP
+.B \ea
+alert (bell)
+.TP
+.B \eb
+backspace
+.TP
+.B \ee
+.TP
+.B \eE
+an escape character
+.TP
+.B \ef
+form feed
+.TP
+.B \en
+new line
+.TP
+.B \er
+carriage return
+.TP
+.B \et
+horizontal tab
+.TP
+.B \ev
+vertical tab
+.TP
+.B \e\e
+backslash
+.TP
+.B \e\(aq
+single quote
+.TP
+.B \e\(dq
+double quote
+.TP
+.B \e?
+question mark
+.TP
+.B \e\fInnn\fP
+the eight-bit character whose value is the octal value \fInnn\fP
+(one to three octal digits)
+.TP
+.B \ex\fIHH\fP
+the eight-bit character whose value is the hexadecimal value \fIHH\fP
+(one or two hex digits)
+.TP
+.B \eu\fIHHHH\fP
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+\fIHHHH\fP (one to four hex digits)
+.TP
+.B \eU\fIHHHHHHHH\fP
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+\fIHHHHHHHH\fP (one to eight hex digits)
+.TP
+.B \ec\fIx\fP
+a control-\fIx\fP character
+.PD
+.RE
+.LP
+The expanded result is single-quoted, as if the dollar sign had
+not been present.
+.PP
+A double-quoted string preceded by a dollar sign (\fB$\fP\(dq\fIstring\fP\(dq)
+will cause the string to be translated according to the current locale.
+The \fIgettext\fP infrastructure performs the message catalog lookup and
+translation, using the \fBLC_MESSAGES\fP and \fBTEXTDOMAIN\fP shell
+variables.
+If the current locale is \fBC\fP or \fBPOSIX\fP,
+or if there are no translations available,
+the dollar sign is ignored.
+If the string is translated and replaced, the replacement is
+double-quoted.
+.SH PARAMETERS
+A
+.I parameter
+is an entity that stores values.
+It can be a
+.IR name ,
+a number, or one of the special characters listed below under
+.BR "Special Parameters" .
+A
+.I variable
+is a parameter denoted by a
+.IR name .
+A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
+Attributes are assigned using the
+.B declare
+builtin command (see
+.B declare
+below in
+.SM
+.BR "SHELL BUILTIN COMMANDS" ).
+.PP
+A parameter is set if it has been assigned a value.  The null string is
+a valid value.  Once a variable is set, it may be unset only by using
+the
+.B unset
+builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.PP
+A
+.I variable
+may be assigned to by a statement of the form
+.RS
+.PP
+\fIname\fP=[\fIvalue\fP]
+.RE
+.PP
+If
+.I value
+is not given, the variable is assigned the null string.  All
+.I values
+undergo tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote
+removal (see
+.SM
+.B EXPANSION
+below).  If the variable has its
+.B integer
+attribute set, then
+.I value
+is evaluated as an arithmetic expression even if the $((...)) expansion is
+not used (see
+.B "Arithmetic Expansion"
+below).
+Word splitting is not performed, with the exception
+of \fB"$@"\fP as explained below under
+.BR "Special Parameters" .
+Pathname expansion is not performed.
+Assignment statements may also appear as arguments to the
+.BR alias ,
+.BR declare ,
+.BR typeset ,
+.BR export ,
+.BR readonly ,
+and
+.B local
+builtin commands (\fIdeclaration\fP commands).
+When in \fIposix mode\fP, these builtins may appear in a command after
+one or more instances of the \fBcommand\fP builtin and retain these
+assignment statement properties.
+.PP
+In the context where an assignment statement is assigning a value
+to a shell variable or array index, the += operator can be used to
+append to or add to the variable's previous value.
+This includes arguments to builtin commands such as \fBdeclare\fP that
+accept assignment statements (\fIdeclaration\fP commands).
+When += is applied to a variable for which the \fIinteger\fP attribute has been
+set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
+variable's current value, which is also evaluated.
+When += is applied to an array variable using compound assignment (see
+.B Arrays
+below), the
+variable's value is not unset (as it is when using =), and new values are
+appended to the array beginning at one greater than the array's maximum index
+(for indexed arrays) or added as additional key\-value pairs in an
+associative array.
+When applied to a string-valued variable, \fIvalue\fP is expanded and
+appended to the variable's value.
+.PP
+A variable can be assigned the \fInameref\fP attribute using the
+\fB\-n\fP option to the \fBdeclare\fP or \fBlocal\fP builtin commands
+(see the descriptions of \fBdeclare\fP and \fBlocal\fP below)
+to create a \fInameref\fP, or a reference to another variable.
+This allows variables to be manipulated indirectly.
+Whenever the nameref variable is referenced, assigned to, unset, or has
+its attributes modified (other than using or changing the \fInameref\fP
+attribute itself), the
+operation is actually performed on the variable specified by the nameref
+variable's value.
+A nameref is commonly used within shell functions to refer to a variable
+whose name is passed as an argument to the function.
+For instance, if a variable name is passed to a shell function as its first
+argument, running
+.sp .5
+.RS
+.if t \f(CWdeclare -n ref=$1\fP
+.if n declare -n ref=$1
+.RE
+.sp .5
+inside the function creates a nameref variable \fBref\fP whose value is
+the variable name passed as the first argument.
+References and assignments to \fBref\fP, and changes to its attributes,
+are treated as references, assignments, and attribute modifications
+to the variable whose name was passed as \fB$1\fP.
+If the control variable in a \fBfor\fP loop has the nameref attribute,
+the list of words can be a list of shell variables, and a name reference
+will be established for each word in the list, in turn, when the loop is
+executed.
+Array variables cannot be given the \fBnameref\fP attribute.
+However, nameref variables can reference array variables and subscripted
+array variables.
+Namerefs can be unset using the \fB\-n\fP option to the \fBunset\fP builtin.
+Otherwise, if \fBunset\fP is executed with the name of a nameref variable
+as an argument, the variable referenced by the nameref variable will be unset.
+.SS Positional Parameters
+A
+.I positional parameter
+is a parameter denoted by one or more
+digits, other than the single digit 0.  Positional parameters are
+assigned from the shell's arguments when it is invoked,
+and may be reassigned using the
+.B set
+builtin command.  Positional parameters may not be assigned to
+with assignment statements.  The positional parameters are
+temporarily replaced when a shell function is executed (see
+.SM
+.B FUNCTIONS
+below).
+.PP
+When a positional parameter consisting of more than a single
+digit is expanded, it must be enclosed in braces (see
+.SM
+.B EXPANSION
+below).
+.SS Special Parameters
+The shell treats several parameters specially.  These parameters may
+only be referenced; assignment to them is not allowed.
+.PD 0
+.TP
+.B *
+Expands to the positional parameters, starting from one.
+When the expansion is not within double quotes, each positional parameter
+expands to a separate word.
+In contexts where it is performed, those words
+are subject to further word splitting and pathname expansion.
+When the expansion occurs within double quotes, it expands to a single word
+with the value of each parameter separated by the first character of the
+.SM
+.B IFS
+special variable.  That is, "\fB$*\fP" is equivalent
+to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
+.I c
+is the first character of the value of the
+.SM
+.B IFS
+variable.  If
+.SM
+.B IFS
+is unset, the parameters are separated by spaces.
+If
+.SM
+.B IFS
+is null, the parameters are joined without intervening separators.
+.TP
+.B @
+Expands to the positional parameters, starting from one.
+In contexts where word splitting is performed, this expands each
+positional parameter to a separate word; if not within double
+quotes, these words are subject to word splitting.
+In contexts where word splitting is not performed,
+this expands to a single word
+with each positional parameter separated by a space.
+When the
+expansion occurs within double quotes, each parameter expands to a
+separate word.  That is, "\fB$@\fP" is equivalent to
+"\fB$1\fP" "\fB$2\fP" ...
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the original
+word, and the expansion of the last parameter is joined with the last
+part of the original word.
+When there are no positional parameters, "\fB$@\fP" and
+.B $@
+expand to nothing (i.e., they are removed).
+.TP
+.B #
+Expands to the number of positional parameters in decimal.
+.TP
+.B ?
+Expands to the exit status of the most recently executed foreground
+pipeline.
+.TP
+.B \-
+Expands to the current option flags as specified upon invocation,
+by the
+.B set
+builtin command, or those set by the shell itself
+(such as the
+.B \-i
+option).
+.TP
+.B $
+Expands to the process ID of the shell.  In a () subshell, it
+expands to the process ID of the current shell, not the
+subshell.
+.TP
+.B !
+Expands to the process ID of the job most recently placed into the
+background, whether executed as an asynchronous command or using
+the \fBbg\fP builtin (see
+.SM
+.B "JOB CONTROL"
+below).
+.TP
+.B 0
+Expands to the name of the shell or shell script.  This is set at
+shell initialization.  If
+.B bash
+is invoked with a file of commands,
+.B $0
+is set to the name of that file.  If
+.B bash
+is started with the
+.B \-c
+option, then
+.B $0
+is set to the first argument after the string to be
+executed, if one is present.  Otherwise, it is set
+to the filename used to invoke
+.BR bash ,
+as given by argument zero.
+.PD
+.SS Shell Variables
+The following variables are set by the shell:
+.PP
+.PD 0
+.TP
+.B _
+At shell startup, set to the 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 simple
+command executed in the foreground, after expansion.
+Also set to the full pathname used to invoke each command executed
+and placed in the environment exported to that command.
+When checking mail, this parameter holds the name of the mail file
+currently being checked.
+.TP
+.B BASH
+Expands to the full filename used to invoke this instance of
+.BR bash .
+.TP
+.B BASHOPTS
+A colon-separated list of enabled shell options.  Each word in
+the list is a valid argument for the
+.B \-s
+option to the
+.B shopt
+builtin command (see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).  The options appearing in
+.SM
+.B BASHOPTS
+are those reported as
+.I on
+by \fBshopt\fP.
+If this variable is in the environment when
+.B bash
+starts up, each shell option in the list will be enabled before
+reading any startup files.
+This variable is read-only.
+.TP
+.B BASHPID
+Expands to the process ID of the current \fBbash\fP process.
+This differs from \fB$$\fP under certain circumstances, such as subshells
+that do not require \fBbash\fP to be re-initialized.
+Assignments to
+.SM
+.B BASHPID
+have no effect.
+If
+.B BASHPID
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B BASH_ALIASES
+An associative array variable whose members correspond to the internal
+list of aliases as maintained by the \fBalias\fP builtin.
+Elements added to this array appear in the alias list; however,
+unsetting array elements currently does not cause aliases to be removed
+from the alias list.
+If
+.B BASH_ALIASES
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B BASH_ARGC
+An array variable whose values are the number of parameters in each
+frame of the current \fBbash\fP execution call stack.
+The number of
+parameters to the current subroutine (shell function or script executed
+with \fB.\fP or \fBsource\fP) is at the top of the stack.
+When a subroutine is executed, the number of parameters passed is pushed onto
+.SM
+.BR BASH_ARGC .
+The shell sets
+.SM
+.B BASH_ARGC
+only when in extended debugging mode (see the description of the
+.B extdebug
+option to the
+.B shopt
+builtin below).
+Setting \fBextdebug\fP after the shell has started to execute a script,
+or referencing this variable when \fBextdebug\fP is not set,
+may result in inconsistent values.
+.TP
+.B BASH_ARGV
+An array variable containing all of the parameters in the current \fBbash\fP
+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
+.SM
+.BR BASH_ARGV .
+The shell sets
+.SM
+.B BASH_ARGV
+only when in extended debugging mode
+(see the description of the
+.B extdebug
+option to the
+.B shopt
+builtin below).
+Setting \fBextdebug\fP after the shell has started to execute a script,
+or referencing this variable when \fBextdebug\fP is not set,
+may result in inconsistent values.
+.TP
+.B BASH_ARGV0
+When referenced, this variable expands to the name of the shell or shell
+script (identical to
+.BR $0 ;
+see the description of special parameter 0 above).
+Assignment to
+.B BASH_ARGV0
+causes the value assigned to also be assigned to \fB$0\fP.
+If
+.B BASH_ARGV0
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B BASH_CMDS
+An associative array variable whose members correspond to the internal
+hash table of commands as maintained by the \fBhash\fP builtin.
+Elements added to this array appear in the hash table; however,
+unsetting array elements currently does not cause command names to be removed
+from the hash table.
+If
+.B BASH_CMDS
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B BASH_COMMAND
+The command currently being executed or about to be executed, unless the
+shell is executing a command as the result of a trap,
+in which case it is the command executing at the time of the trap.
+If
+.B BASH_COMMAND
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B BASH_EXECUTION_STRING
+The command argument to the \fB\-c\fP invocation option.
+.TP
+.B BASH_LINENO
+An array variable whose members are the line numbers in source files
+where each corresponding member of
+.SM
+.B FUNCNAME
+was invoked.
+\fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
+file (\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP) where
+\fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called
+(or \fB${BASH_LINENO[\fP\fI$i-1\fP\fB]}\fP if referenced within another
+shell function).
+Use
+.SM
+.B LINENO
+to obtain the current line number.
+.TP
+.B BASH_LOADABLES_PATH
+A colon-separated list of directories in which the shell looks for
+dynamically loadable builtins specified by the
+.B enable
+command.
+.TP
+.B BASH_REMATCH
+An array variable whose members are assigned by the \fB=~\fP binary
+operator to the \fB[[\fP conditional command.
+The element with index 0 is the portion of the string
+matching the entire regular expression.
+The element with index \fIn\fP is the portion of the
+string matching the \fIn\fPth parenthesized subexpression.
+.TP
+.B BASH_SOURCE
+An array variable whose members are the source filenames
+where the corresponding shell function names in the
+.SM
+.B FUNCNAME
+array variable are defined.
+The shell function
+\fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP is defined in the file
+\fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fP and called from
+\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP.
+.TP
+.B BASH_SUBSHELL
+Incremented by one within each subshell or subshell environment when
+the shell begins executing in that environment.
+The initial value is 0.
+If
+.B BASH_SUBSHELL
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B BASH_VERSINFO
+A readonly array variable whose members hold version information for
+this instance of
+.BR bash .
+The values assigned to the array members are as follows:
+.sp .5
+.RS
+.TP 24
+.B BASH_VERSINFO[\fR0\fP]
+The major version number (the \fIrelease\fP).
+.TP
+.B BASH_VERSINFO[\fR1\fP]
+The minor version number (the \fIversion\fP).
+.TP
+.B BASH_VERSINFO[\fR2\fP]
+The patch level.
+.TP
+.B BASH_VERSINFO[\fR3\fP]
+The build version.
+.TP
+.B BASH_VERSINFO[\fR4\fP]
+The release status (e.g., \fIbeta1\fP).
+.TP
+.B BASH_VERSINFO[\fR5\fP]
+The value of
+.SM
+.BR MACHTYPE .
+.RE
+.TP
+.B BASH_VERSION
+Expands to a string describing the version of this instance of
+.BR bash .
+.TP
+.B COMP_CWORD
+An index into \fB${COMP_WORDS}\fP of the word containing the current
+cursor position.
+This variable is available only in shell functions invoked by the
+programmable completion facilities (see \fBProgrammable Completion\fP
+below).
+.TP
+.B COMP_KEY
+The key (or final key of a key sequence) used to invoke the current
+completion function.
+.TP
+.B COMP_LINE
+The current command line.
+This variable is available only in shell functions and external
+commands invoked by the
+programmable completion facilities (see \fBProgrammable Completion\fP
+below).
+.TP
+.B COMP_POINT
+The index of the current cursor position relative to the beginning of
+the current command.
+If the current cursor position is at the end of the current command,
+the value of this variable is equal to \fB${#COMP_LINE}\fP.
+This variable is available only in shell functions and external
+commands invoked by the
+programmable completion facilities (see \fBProgrammable Completion\fP
+below).
+.TP
+.B COMP_TYPE
+Set to an integer value corresponding to the type of completion attempted
+that caused a completion function to be called:
+\fITAB\fP, for normal completion,
+\fI?\fP, for listing completions after successive tabs,
+\fI!\fP, for listing alternatives on partial word completion,
+\fI@\fP, to list completions if the word is not unmodified,
+or
+\fI%\fP, for menu completion.
+This variable is available only in shell functions and external
+commands invoked by the
+programmable completion facilities (see \fBProgrammable Completion\fP
+below).
+.TP
+.B COMP_WORDBREAKS
+The set of characters that the \fBreadline\fP library treats as word
+separators when performing word completion.
+If
+.SM
+.B COMP_WORDBREAKS
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B COMP_WORDS
+An array variable (see \fBArrays\fP below) consisting of the individual
+words in the current command line.
+The line is split into words as \fBreadline\fP would split it, using
+.SM
+.B COMP_WORDBREAKS
+as described above.
+This variable is available only in shell functions invoked by the
+programmable completion facilities (see \fBProgrammable Completion\fP
+below).
+.TP
+.B COPROC
+An array variable (see \fBArrays\fP below) created to hold the file descriptors
+for output from and input to an unnamed coprocess (see \fBCoprocesses\fP
+above).
+.TP
+.B DIRSTACK
+An array variable (see
+.B Arrays
+below) containing the current contents of the directory stack.
+Directories appear in the stack in the order they are displayed by the
+.B dirs
+builtin.
+Assigning to members of this array variable may be used to modify
+directories already in the stack, but the
+.B pushd
+and
+.B popd
+builtins must be used to add and remove directories.
+Assignment to this variable will not change the current directory.
+If
+.SM
+.B DIRSTACK
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B EPOCHREALTIME
+Each time this parameter is referenced, it expands to the number of seconds
+since the Unix Epoch (see \fItime\fP\fR(3)\fP) as a floating point value
+with micro-second granularity.
+Assignments to
+.SM
+.B EPOCHREALTIME
+are ignored.
+If
+.SM
+.B EPOCHREALTIME
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B EPOCHSECONDS
+Each time this parameter is referenced, it expands to the number of seconds
+since the Unix Epoch (see \fItime\fP\fR(3)\fP).
+Assignments to
+.SM
+.B EPOCHSECONDS
+are ignored.
+If
+.SM
+.B EPOCHSECONDS
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B EUID
+Expands to the effective user ID of the current user, initialized at
+shell startup.  This variable is readonly.
+.TP
+.B FUNCNAME
+An array variable containing the names of all shell functions
+currently in the execution call stack.
+The element with index 0 is the name of any currently-executing
+shell function.
+The bottom-most element (the one with the highest index) is
+.if t \f(CW"main"\fP.
+.if n "main".
+This variable exists only when a shell function is executing.
+Assignments to
+.SM
+.B FUNCNAME
+have no effect.
+If
+.SM
+.B FUNCNAME
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.if t .sp 0.5
+.if n .sp 1
+This variable can be used with \fBBASH_LINENO\fP and \fBBASH_SOURCE\fP.
+Each element of \fBFUNCNAME\fP has corresponding elements in
+\fBBASH_LINENO\fP and \fBBASH_SOURCE\fP to describe the call stack.
+For instance, \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called from the file
+\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP at line number
+\fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP.
+The \fBcaller\fP builtin displays the current call stack using this
+information.
+.TP
+.B GROUPS
+An array variable containing the list of groups of which the current
+user is a member.
+Assignments to
+.SM
+.B GROUPS
+have no effect.
+If
+.SM
+.B GROUPS
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B HISTCMD
+The history number, or index in the history list, of the current
+command.
+Assignments to
+.SM
+.B HISTCMD
+are ignored.
+If
+.SM
+.B HISTCMD
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B HOSTNAME
+Automatically set to the name of the current host.
+.TP
+.B HOSTTYPE
+Automatically set to a string that uniquely
+describes the type of machine on which
+.B bash
+is executing.
+The default is system-dependent.
+.TP
+.B LINENO
+Each time this parameter is referenced, the shell substitutes
+a decimal number representing the current sequential line number
+(starting with 1) within a script or function.  When not in a
+script or function, the value substituted is not guaranteed to
+be meaningful.
+If
+.SM
+.B LINENO
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B MACHTYPE
+Automatically set to a string that fully describes the system
+type on which
+.B bash
+is executing, in the standard GNU \fIcpu-company-system\fP format.
+The default is system-dependent.
+.TP
+.B MAPFILE
+An array variable (see \fBArrays\fP below) created to hold the text
+read by the \fBmapfile\fP builtin when no variable name is supplied.
+.TP
+.B OLDPWD
+The previous working directory as set by the
+.B cd
+command.
+.TP
+.B OPTARG
+The value of the last option argument processed by the
+.B getopts
+builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.TP
+.B OPTIND
+The index of the next argument to be processed by the
+.B getopts
+builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.TP
+.B OSTYPE
+Automatically set to a string that
+describes the operating system on which
+.B bash
+is executing.
+The default is system-dependent.
+.TP
+.B PIPESTATUS
+An array variable (see
+.B Arrays
+below) containing a list of exit status values from the processes
+in the most-recently-executed foreground pipeline (which may
+contain only a single command).
+.TP
+.B PPID
+The process ID of the shell's parent.  This variable is readonly.
+.TP
+.B PWD
+The current working directory as set by the
+.B cd
+command.
+.TP
+.B RANDOM
+Each time this parameter is referenced, it expands to a random integer
+between 0 and 32767.
+Assigning
+a value to
+.SM
+.BR RANDOM
+initializes (seeds) the sequence of random numbers.
+If
+.SM
+.B RANDOM
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B READLINE_LINE
+The contents of the
+.B readline
+line buffer, for use with
+.if t \f(CWbind -x\fP
+.if n "bind -x"
+(see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).
+.TP
+.B READLINE_MARK
+The position of the mark (saved insertion point) in the
+.B readline
+line buffer, for use with
+.if t \f(CWbind -x\fP
+.if n "bind -x"
+(see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).
+The characters between the insertion point and the mark are often
+called the \fIregion\fP.
+.TP
+.B READLINE_POINT
+The position of the insertion point in the
+.B readline
+line buffer, for use with
+.if t \f(CWbind -x\fP
+.if n "bind -x"
+(see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).
+.TP
+.B REPLY
+Set to the line of input read by the
+.B read
+builtin command when no arguments are supplied.
+.TP
+.B SECONDS
+Each time this parameter is
+referenced, the number of seconds since shell invocation is returned.  If a
+value is assigned to
+.SM
+.BR SECONDS ,
+the value returned upon subsequent
+references is
+the number of seconds since the assignment plus the value assigned.
+The number of seconds at shell invocation and the current time is always
+determined by querying the system clock.
+If
+.SM
+.B SECONDS
+is unset, it loses its special properties, even if it is
+subsequently reset.
+.TP
+.B SHELLOPTS
+A colon-separated list of enabled shell options.  Each word in
+the list is a valid argument for the
+.B \-o
+option to the
+.B set
+builtin command (see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).  The options appearing in
+.SM
+.B SHELLOPTS
+are those reported as
+.I on
+by \fBset \-o\fP.
+If this variable is in the environment when
+.B bash
+starts up, each shell option in the list will be enabled before
+reading any startup files.
+This variable is read-only.
+.TP
+.B SHLVL
+Incremented by one each time an instance of
+.B bash
+is started.
+.TP
+.B SRANDOM
+This variable expands to a 32-bit pseudo-random number each time it is
+referenced. The random number generator is not linear on systems that
+support \f(CW/dev/urandom\fP or \fIarc4random\fP, so each returned number
+has no relationship to the numbers preceding it.
+The random number generator cannot be seeded, so assignments to this
+variable have no effect.
+If
+.SM
+.B SRANDOM
+is unset, it loses its special properties,
+even if it is subsequently reset.
+.TP
+.B UID
+Expands to the user ID of the current user, initialized at shell startup.
+This variable is readonly.
+.PD
+.PP
+The following variables are used by the shell.  In some cases,
+.B bash
+assigns a default value to a variable; these cases are noted
+below.
+.PP
+.PD 0
+.TP
+.B BASH_COMPAT
+The value is used to set the shell's compatibility level.
+See
+.SM
+.B SHELL COMPATIBILITY MODE
+below for a description of the various compatibility
+levels and their effects.
+The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
+corresponding to the desired compatibility level.
+If \fBBASH_COMPAT\fP is unset or set to the empty string, the compatibility
+level is set to the default for the current version.
+If \fBBASH_COMPAT\fP is set to a value that is not one of the valid
+compatibility levels, the shell prints an error message and sets the
+compatibility level to the default for the current version.
+The valid values correspond to the compatibility levels
+described below under
+.SM
+.BR BSHELL COMPATIBILITY MODE .
+For example, 4.2 and 42 are valid values that correspond
+to the \fBcompat42\fP \fBshopt\fP option
+and set the compatibility level to 42.
+The current version is also a valid value.
+.TP
+.B BASH_ENV
+If this parameter is set when \fBbash\fP is executing a shell script,
+its value is interpreted as a filename containing commands to
+initialize the shell, as in
+.IR ~/.bashrc .
+The value of
+.SM
+.B BASH_ENV
+is subjected to parameter expansion, command substitution, and arithmetic
+expansion before being interpreted as a filename.
+.SM
+.B PATH
+is not used to search for the resultant filename.
+.TP
+.B BASH_XTRACEFD
+If set to an integer corresponding to a valid file descriptor, \fBbash\fP
+will write the trace output generated when
+.if t \f(CWset -x\fP
+.if n \fIset -x\fP
+is enabled to that file descriptor.
+The file descriptor is closed when
+.SM
+.B BASH_XTRACEFD
+is unset or assigned a new value.
+Unsetting
+.SM
+.B BASH_XTRACEFD
+or assigning it the empty string causes the
+trace output to be sent to the standard error.
+Note that setting
+.SM
+.B BASH_XTRACEFD
+to 2 (the standard error file
+descriptor) and then unsetting it will result in the standard error
+being closed.
+.TP
+.B CDPATH
+The search path for the
+.B cd
+command.
+This is a colon-separated list of directories in which the shell looks
+for destination directories specified by the
+.B cd
+command.
+A sample value is
+.if t \f(CW".:~:/usr"\fP.
+.if n ".:~:/usr".
+.TP
+.B CHILD_MAX
+Set the number of exited child status values for the shell to remember.
+Bash will not allow this value to be decreased below a POSIX-mandated
+minimum, and there is a maximum value (currently 8192) that this may
+not exceed.
+The minimum value is system-dependent.
+.TP
+.B COLUMNS
+Used by the \fBselect\fP compound command to determine the terminal width
+when printing selection lists.
+Automatically set if the
+.B checkwinsize
+option is enabled or in an interactive shell upon receipt of a
+.SM
+.BR SIGWINCH .
+.TP
+.B COMPREPLY
+An array variable from which \fBbash\fP reads the possible completions
+generated by a shell function invoked by the programmable completion
+facility (see \fBProgrammable Completion\fP below).
+Each array element contains one possible completion.
+.TP
+.B EMACS
+If \fBbash\fP finds this variable in the environment when the shell starts
+with value
+.if t \f(CWt\fP,
+.if n "t",
+it assumes that the shell is running in an Emacs shell buffer and disables
+line editing.
+.TP
+.B ENV
+Expanded and executed similarly to
+.SM
+.B BASH_ENV
+(see \fBINVOCATION\fP above)
+when an interactive shell is invoked in \fIposix mode\fP.
+.TP
+.B EXECIGNORE
+A colon-separated list of shell patterns (see \fBPattern Matching\fP)
+defining the list of filenames to be ignored by command search using
+\fBPATH\fP.
+Files whose full pathnames match one of these patterns are not considered
+executable files for the purposes of completion and command execution
+via \fBPATH\fP lookup.
+This does not affect the behavior of the \fB[\fP, \fBtest\fP, and \fB[[\fP
+commands.
+Full pathnames in the command hash table are not subject to \fBEXECIGNORE\fP.
+Use this variable to ignore shared library files that have the executable
+bit set, but are not executable files.
+The pattern matching honors the setting of the \fBextglob\fP shell
+option.
+.TP
+.B FCEDIT
+The default editor for the
+.B fc
+builtin command.
+.TP
+.B FIGNORE
+A colon-separated list of suffixes to ignore when performing
+filename completion (see
+.SM
+.B READLINE
+below).
+A filename whose suffix matches one of the entries in
+.SM
+.B FIGNORE
+is excluded from the list of matched filenames.
+A sample value is
+.if t \f(CW".o:~"\fP.
+.if n ".o:~".
+.TP
+.B FUNCNEST
+If set to a numeric value greater than 0, defines a maximum function
+nesting level.  Function invocations that exceed this nesting level
+will cause the current command to abort.
+.TP
+.B GLOBIGNORE
+A colon-separated list of patterns defining the set of file names to
+be ignored by pathname expansion.
+If a file name matched by a pathname expansion pattern also matches one
+of the patterns in
+.SM
+.BR GLOBIGNORE ,
+it is removed from the list of matches.
+.TP
+.B HISTCONTROL
+A colon-separated list of values controlling how commands are saved on
+the history list.
+If the list of values includes
+.IR ignorespace ,
+lines which begin with a
+.B space
+character are not saved in the history list.
+A value of
+.I ignoredups
+causes lines matching the previous history entry to not be saved.
+A value of
+.I ignoreboth
+is shorthand for \fIignorespace\fP and \fIignoredups\fP.
+A value of
+.I 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
+.SM
+.B 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
+.SM
+.BR 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
+.SM
+.BR HISTCONTROL .
+.TP
+.B HISTFILE
+The name of the file in which command history is saved (see
+.SM
+.B HISTORY
+below).  The default value is \fI~/.bash_history\fP.  If unset, the
+command history is not saved when a shell exits.
+.TP
+.B HISTFILESIZE
+The maximum number of lines contained in the history file.  When this
+variable is assigned a value, the history file is truncated, if
+necessary,
+to contain no more than that number of lines by removing the oldest entries.
+The history file is also truncated to this size after
+writing it when a shell exits.
+If the value is 0, the history file is truncated to zero size.
+Non-numeric values and numeric values less than zero inhibit truncation.
+The shell sets the default value to the value of \fBHISTSIZE\fP
+after reading any startup files.
+.TP
+.B HISTIGNORE
+A colon-separated list of patterns used to decide which command lines
+should be saved on the history list.  Each pattern is anchored at the
+beginning of the line and must match the complete line (no implicit
+`\fB*\fP' is appended).  Each pattern is tested against the line
+after the checks specified by
+.SM
+.B HISTCONTROL
+are applied.
+In addition to the normal shell pattern matching characters, `\fB&\fP'
+matches the previous history line.  `\fB&\fP' may be escaped using a
+backslash; the backslash is removed before attempting a match.
+The second and subsequent lines of a multi-line compound command are
+not tested, and are added to the history regardless of the value of
+.SM
+.BR HISTIGNORE .
+The pattern matching honors the setting of the \fBextglob\fP shell
+option.
+.TP
+.B HISTSIZE
+The number of commands to remember in the command history (see
+.SM
+.B HISTORY
+below).
+If the value is 0, commands are not saved in the history list.
+Numeric values less than zero result in every command being saved
+on the history list (there is no limit).
+The shell sets the default value to 500 after reading any startup files.
+.TP
+.B HISTTIMEFORMAT
+If this variable is set and not null, its value is used as a format string
+for \fIstrftime\fP(3) to print the time stamp associated with each history
+entry displayed by the \fBhistory\fP 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.
+.TP
+.B HOME
+The home directory of the current user; the default argument for the
+\fBcd\fP builtin command.
+The value of this variable is also used when performing tilde expansion.
+.TP
+.B HOSTFILE
+Contains the name of a file in the same format as
+.FN /etc/hosts
+that should be read when the shell needs to complete a
+hostname.
+The list of possible hostname completions may be changed while the
+shell is running;
+the next time hostname completion is attempted after the
+value is changed,
+.B bash
+adds the contents of the new file to the existing list.
+If
+.SM
+.B HOSTFILE
+is set, but has no value, or does not name a readable file,
+\fBbash\fP attempts to read
+.FN /etc/hosts
+to obtain the list of possible hostname completions.
+When
+.SM
+.B HOSTFILE
+is unset, the hostname list is cleared.
+.TP
+.B IFS
+The
+.I Internal Field Separator
+that is used
+for word splitting after expansion and to
+split lines into words with the
+.B read
+builtin command.  The default value is
+``<space><tab><newline>''.
+.TP
+.B IGNOREEOF
+Controls the
+action of an interactive shell on receipt of an
+.SM
+.B EOF
+character as the sole input.  If set, the value is the number of
+consecutive
+.SM
+.B EOF
+characters which must be
+typed as the first characters on an input line before
+.B bash
+exits.  If the variable exists but does not have a numeric value, or
+has no value, the default value is 10.  If it does not exist,
+.SM
+.B EOF
+signifies the end of input to the shell.
+.TP
+.B INPUTRC
+The filename for the
+.B readline
+startup file, overriding the default of
+.FN ~/.inputrc
+(see
+.SM
+.B READLINE
+below).
+.TP
+.B INSIDE_EMACS
+If this variable appears in the environment when the shell starts,
+\fBbash\fP assumes that it is running inside an Emacs shell buffer
+and may disable line editing, depending on the value of \fBTERM\fP.
+.TP
+.B LANG
+Used to determine the locale category for any category not specifically
+selected with a variable starting with \fBLC_\fP.
+.TP
+.B LC_ALL
+This variable overrides the value of
+.SM
+.B LANG
+and any other
+\fBLC_\fP variable specifying a locale category.
+.TP
+.B LC_COLLATE
+This variable determines the collation order used when sorting the
+results of pathname expansion, and determines the behavior of range
+expressions, equivalence classes, and collating sequences within
+pathname expansion and pattern matching.
+.TP
+.B LC_CTYPE
+This variable determines the interpretation of characters and the
+behavior of character classes within pathname expansion and pattern
+matching.
+.TP
+.B LC_MESSAGES
+This variable determines the locale used to translate double-quoted
+strings preceded by a \fB$\fP.
+.TP
+.B LC_NUMERIC
+This variable determines the locale category used for number formatting.
+.TP
+.B LC_TIME
+This variable determines the locale category used for data and time
+formatting.
+.TP
+.B LINES
+Used by the \fBselect\fP compound command to determine the column length
+for printing selection lists.
+Automatically set if the
+.B checkwinsize
+option is enabled or in an interactive shell upon receipt of a
+.SM
+.BR SIGWINCH .
+.TP
+.B MAIL
+If this parameter is set to a file or directory name and the
+.SM
+.B MAILPATH
+variable is not set,
+.B bash
+informs the user of the arrival of mail in the specified file or
+Maildir-format directory.
+.TP
+.B MAILCHECK
+Specifies how
+often (in seconds)
+.B bash
+checks for mail.  The default is 60 seconds.  When it is time to check
+for mail, the shell does so before displaying the primary prompt.
+If this variable is unset, or set to a value that is not a number
+greater than or equal to zero, the shell disables mail checking.
+.TP
+.B MAILPATH
+A colon-separated list of filenames to be checked for mail.
+The message to be printed when mail arrives in a particular file
+may be specified by separating the filename from the message with a `?'.
+When used in the text of the message, \fB$_\fP expands to the name of
+the current mailfile.
+Example:
+.RS
+.PP
+\fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
+.PP
+.B Bash
+can be configured to supply
+a default value for this variable (there is no value by default),
+but the location of the user
+mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
+.RE
+.TP
+.B OPTERR
+If set to the value 1,
+.B bash
+displays error messages generated by the
+.B getopts
+builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.SM
+.B OPTERR
+is initialized to 1 each time the shell is invoked or a shell
+script is executed.
+.TP
+.B PATH
+The search path for commands.  It
+is a colon-separated list of directories in which
+the shell looks for commands (see
+.SM
+.B COMMAND EXECUTION
+below).
+A zero-length (null) directory name in the value of
+.SM
+.B PATH
+indicates the current directory.
+A null directory name may appear as two adjacent colons, or as an initial
+or trailing colon.
+The default path is system-dependent,
+and is set by the administrator who installs
+.BR bash .
+A common value is
+.na
+.if t \f(CW/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin\fP.
+.if n ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
+.ad
+.TP
+.B POSIXLY_CORRECT
+If this variable is in the environment when \fBbash\fP starts, the shell
+enters \fIposix mode\fP before reading the startup files, as if the
+.B \-\-posix
+invocation option had been supplied.  If it is set while the shell is
+running, \fBbash\fP enables \fIposix mode\fP, as if the command
+.if t \f(CWset -o posix\fP
+.if n \fIset -o posix\fP
+had been executed.
+When the shell enters \fIposix mode\fP, it sets this variable if it was
+not already set.
+.TP
+.B PROMPT_COMMAND
+If this variable is set, and is an array,
+the value of each set element is executed as a command
+prior to issuing each primary prompt.
+If this is set but not an array variable, 
+its value is used as a command to execute instead.
+.TP
+.B 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 \fB\ew\fP and
+\fB\eW\fP prompt string escapes (see
+.SM
+.B PROMPTING
+below).  Characters removed are replaced with an ellipsis.
+.TP
+.B PS0
+The value of this parameter is expanded (see
+.SM
+.B PROMPTING
+below) and displayed by interactive shells after reading a command
+and before the command is executed.
+.TP
+.B PS1
+The value of this parameter is expanded (see
+.SM
+.B PROMPTING
+below) and used as the primary prompt string.  The default value is
+``\fB\es\-\ev\e$ \fP''.
+.TP
+.B PS2
+The value of this parameter is expanded as with
+.SM
+.B PS1
+and used as the secondary prompt string.  The default is
+``\fB> \fP''.
+.TP
+.B PS3
+The value of this parameter is used as the prompt for the
+.B select
+command (see
+.SM
+.B SHELL GRAMMAR
+above).
+.TP
+.B PS4
+The value of this parameter is expanded as with
+.SM
+.B PS1
+and the value is printed before each command
+.B bash
+displays during an execution trace.  The first character of
+the expanded value of
+.SM
+.B PS4
+is replicated multiple times, as necessary, to indicate multiple
+levels of indirection.  The default is ``\fB+ \fP''.
+.TP
+.B SHELL
+This variable expands to the full pathname to the shell.
+If it is not set when the shell starts,
+.B bash
+assigns to it the full pathname of the current user's login shell.
+.TP
+.B TIMEFORMAT
+The value of this parameter is used as a format string specifying
+how the timing information for pipelines prefixed with the
+.B time
+reserved word should be displayed.
+The \fB%\fP character introduces an escape sequence that is
+expanded to a time value or other information.
+The escape sequences and their meanings are as follows; the
+braces denote optional portions.
+.sp .5
+.RS
+.PD 0
+.TP 10
+.B %%
+A literal \fB%\fP.
+.TP
+.B %[\fIp\fP][l]R
+The elapsed time in seconds.
+.TP
+.B %[\fIp\fP][l]U
+The number of CPU seconds spent in user mode.
+.TP
+.B %[\fIp\fP][l]S
+The number of CPU seconds spent in system mode.
+.TP
+.B %P
+The CPU percentage, computed as (%U + %S) / %R.
+.PD
+.RE
+.IP
+The optional \fIp\fP is a digit specifying the \fIprecision\fP,
+the number of fractional digits after a decimal point.
+A value of 0 causes no decimal point or fraction to be output.
+At most three places after the decimal point may be specified;
+values of \fIp\fP greater than 3 are changed to 3.
+If \fIp\fP is not specified, the value 3 is used.
+.IP
+The optional \fBl\fP specifies a longer format, including
+minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
+The value of \fIp\fP determines whether or not the fraction is
+included.
+.IP
+If this variable is not set, \fBbash\fP acts as if it had the
+value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\et%3lS\(aq\fP.
+If the value is null, no timing information is displayed.
+A trailing newline is added when the format string is displayed.
+.PD 0
+.TP
+.B TMOUT
+If set to a value greater than zero,
+.SM
+.B TMOUT
+is treated as the
+default timeout for the \fBread\fP builtin.
+The \fBselect\fP command terminates if input does not arrive
+after
+.SM
+.B TMOUT
+seconds when input is coming from a terminal.
+In an interactive shell, the value is interpreted as the
+number of seconds to wait for a line of input after issuing the
+primary prompt.
+.B Bash
+terminates after waiting for that number of seconds if a complete
+line of input does not arrive.
+.TP
+.B TMPDIR
+If set, \fBbash\fP uses its value as the name of a directory in which
+\fBbash\fP creates temporary files for the shell's use.
+.TP
+.B auto_resume
+This variable controls how the shell interacts with the user and
+job control.  If this variable is set, single word simple
+commands without redirections are treated as candidates for resumption
+of an existing stopped job.  There is no ambiguity allowed; if there is
+more than one job beginning with the string typed, the job most recently
+accessed is selected.  The
+.I name
+of a stopped job, in this context, is the command line used to
+start it.
+If set to the value
+.IR exact ,
+the string supplied must match the name of a stopped job exactly;
+if set to
+.IR substring ,
+the string supplied needs to match a substring of the name of a
+stopped job.  The
+.I substring
+value provides functionality analogous to the
+.B %?
+job identifier (see
+.SM
+.B JOB CONTROL
+below).  If set to any other value, the supplied string must
+be a prefix of a stopped job's name; this provides functionality
+analogous to the \fB%\fP\fIstring\fP job identifier.
+.TP
+.B histchars
+The two or three characters which control history expansion
+and tokenization (see
+.SM
+.B HISTORY EXPANSION
+below).  The first character is the \fIhistory expansion\fP character,
+the character which signals the start of a history
+expansion, normally `\fB!\fP'.
+The second character is the \fIquick substitution\fP
+character, which is used as shorthand for re-running the previous
+command entered, substituting one string for another in the command.
+The default is `\fB^\fP'.
+The optional third character is the character
+which indicates that the remainder of the line is a comment when found
+as the first character of a word, normally `\fB#\fP'.  The history
+comment character causes history substitution to be skipped for the
+remaining words on the line.  It does not necessarily cause the shell
+parser to treat the rest of the line as a comment.
+.PD
+.SS Arrays
+.B Bash
+provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array; the
+.B declare
+builtin will explicitly declare an array.
+There is no maximum
+limit on the size of an array, nor any requirement that members
+be indexed or assigned contiguously.
+Indexed arrays are referenced using integers (including arithmetic
+expressions) and are zero-based; associative arrays are referenced
+using arbitrary strings.
+Unless otherwise noted, indexed array indices must be non-negative integers.
+.PP
+An indexed array is created automatically if any variable is assigned to
+using the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP.  The
+.I subscript
+is treated as an arithmetic expression that must evaluate to a number.
+To explicitly declare an indexed array, use
+.B declare \-a \fIname\fP
+(see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.B declare \-a \fIname\fP[\fIsubscript\fP]
+is also accepted; the \fIsubscript\fP is ignored.
+.PP
+Associative arrays are created using
+.BR "declare \-A \fIname\fP" .
+.PP
+Attributes may be
+specified for an array variable using the
+.B declare
+and
+.B readonly
+builtins.  Each attribute applies to all members of an array.
+.PP
+Arrays are assigned to using compound assignments of the form
+\fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
+\fIvalue\fP may be of the form [\fIsubscript\fP]=\fIstring\fP.
+Indexed array assignments do not require anything but \fIstring\fP.
+Each \fIvalue\fP in the list is expanded using all the shell expansions
+described below under
+.SM
+.BR EXPANSION .
+When assigning to indexed arrays, if the optional brackets and subscript
+are 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.
+.PP
+When assigning to an associative array, the words in a compound assignment
+may be either assignment statements, for which the subscript is required,
+or a list of words that is interpreted as a sequence of alternating keys
+and values:
+\fIname\fP=\fB( \fP\fIkey1 value1 key2 value2\fP ...\fB)\fP.
+These are treated identically to
+\fIname\fP=\fB(\fP [\fIkey1\fP]=\fIvalue1\fP [\fIkey2\fP]=\fIvalue2\fP ...\fB)\fP.
+The first word in the list determines how the remaining words
+are interpreted; all assignments in a list must be of the same type.
+When using key/value pairs, the keys may not be missing or empty;
+a final missing value is treated like the empty string.
+.PP
+This syntax is also accepted by the
+.B declare
+builtin.  Individual array elements may be assigned to using the
+\fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
+When assigning to an indexed array, if
+.I name
+is subscripted by a negative number, that number is
+interpreted as relative to one greater than the maximum index of
+\fIname\fP, so negative indices count back from the end of the
+array, and an index of \-1 references the last element.
+.PP
+Any element of an array may be referenced using
+${\fIname\fP[\fIsubscript\fP]}.  The braces are required to avoid
+conflicts with pathname expansion.  If
+\fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
+all members of \fIname\fP.  These subscripts differ only when the
+word appears within double quotes.  If the word is double-quoted,
+${\fIname\fP[*]} expands to a single
+word with the value of each array member separated by the first
+character of the
+.SM
+.B IFS
+special variable, and ${\fIname\fP[@]} expands each element of
+\fIname\fP to a separate word.  When there are no array members,
+${\fIname\fP[@]} 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 \fB*\fP and \fB@\fP (see
+.B Special Parameters
+above).  ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
+${\fIname\fP[\fIsubscript\fP]}.  If \fIsubscript\fP is \fB*\fP or
+\fB@\fP, the expansion is the number of elements in the array.
+If the
+.I subscript
+used to reference an element of an indexed array
+evaluates to a number less than zero, it is
+interpreted as relative to one greater than the maximum index of the array,
+so negative indices count back from the end of the
+array, and an index of \-1 references the last element.
+.PP
+Referencing an array variable without a subscript is equivalent to
+referencing the array with a subscript of 0.
+Any reference to a variable using a valid subscript is legal, and
+.B bash
+will create an array if necessary.
+.PP
+An array variable is considered set if a subscript has been assigned a
+value.  The null string is a valid value.
+.PP
+It is possible to obtain the keys (indices) of an array as well as the values.
+${\fB!\fP\fIname\fP[\fI@\fP]} and ${\fB!\fP\fIname\fP[\fI*\fP]}
+expand to the indices assigned in array variable \fIname\fP.
+The treatment when in double quotes is similar to the expansion of the
+special parameters \fI@\fP and \fI*\fP within double quotes.
+.PP
+The
+.B unset
+builtin is used to destroy arrays.  \fBunset\fP \fIname\fP[\fIsubscript\fP]
+destroys the array element at index \fIsubscript\fP,
+for both indexed and associative arrays.
+Negative subscripts to indexed arrays are interpreted as described above.
+Unsetting the last element of an array variable does not unset the variable.
+\fBunset\fP \fIname\fP, where \fIname\fP is an array, or
+\fBunset\fP \fIname\fP[\fIsubscript\fP], where
+\fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
+.PP
+When using a variable name with a subscript as an argument to a command,
+such as with \fBunset\fP, without using the word expansion syntax
+described above, the argument is subject to pathname expansion.
+If pathname expansion is not desired, the argument should be quoted.
+.PP
+The
+.BR declare ,
+.BR local ,
+and
+.B readonly
+builtins each accept a
+.B \-a
+option to specify an indexed array and a
+.B \-A
+option to specify an associative array.
+If both options are supplied,
+.B \-A
+takes precedence.
+The
+.B read
+builtin accepts a
+.B \-a
+option to assign a list of words read from the standard input
+to an array.  The
+.B set
+and
+.B declare
+builtins display array values in a way that allows them to be
+reused as assignments.
+.SH EXPANSION
+Expansion is performed on the command line after it has been split into
+words.  There are seven kinds of expansion performed:
+.IR "brace expansion" ,
+.IR "tilde expansion" ,
+.IR "parameter and variable expansion" ,
+.IR "command substitution" ,
+.IR "arithmetic expansion" ,
+.IR "word splitting" ,
+and
+.IR "pathname expansion" .
+.PP
+The order of expansions is:
+brace expansion;
+tilde expansion, parameter and variable expansion, arithmetic expansion,
+and command substitution (done in a left-to-right fashion);
+word splitting;
+and pathname expansion.
+.PP
+On systems that can support it, there is an additional expansion
+available: \fIprocess substitution\fP.
+This is performed at the
+same time as tilde, parameter, variable, and arithmetic expansion and
+command substitution.
+.PP
+After these expansions are performed, quote characters present in the
+original word are removed unless they have been quoted themselves
+(\fIquote removal\fP).
+.PP
+Only brace expansion, word splitting, and pathname expansion
+can increase the number of words of the expansion; other expansions
+expand a single word to a single word.
+The only exceptions to this are the expansions of
+"\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP",
+and, in most cases, \fB$*\fP and \fB${\fP\fIname\fP\fB[*]}\fP
+as explained above (see
+.SM
+.BR PARAMETERS ).
+.SS Brace Expansion
+.I "Brace expansion"
+is a mechanism by which arbitrary strings
+may be generated.  This mechanism is similar to
+\fIpathname expansion\fP, but the filenames generated
+need not exist.  Patterns to be brace expanded take
+the form of an optional
+.IR preamble ,
+followed by either a series of comma-separated strings or
+a sequence expression between a pair of braces, followed by
+an optional
+.IR postscript .
+The preamble is prefixed to each string contained
+within the braces, and the postscript is then appended
+to each resulting string, expanding left to right.
+.PP
+Brace expansions may be nested.  The results of each expanded
+string are not sorted; left to right order is preserved.
+For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
+.PP
+A sequence expression takes the form
+\fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB[..\fP\fIincr\fP\fB]}\fP,
+where \fIx\fP and \fIy\fP are either integers or single characters,
+and \fIincr\fP, an optional increment, is an integer.
+When integers are supplied, the expression expands to each number between
+\fIx\fP and \fIy\fP, inclusive.
+Supplied integers may be prefixed with \fI0\fP to force each term to have the
+same width.
+When either \fIx\fP or \fPy\fP 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 \fIx\fP and \fIy\fP, inclusive,
+using the default C locale.
+Note that both \fIx\fP and \fIy\fP 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.
+.PP
+Brace expansion is performed before any other expansions,
+and any characters special to other expansions are preserved
+in the result.  It is strictly textual.
+.B Bash
+does not apply any syntactic interpretation to the context of the
+expansion or the text between the braces.
+.PP
+A correctly-formed brace expansion must contain unquoted opening
+and closing braces, and at least one unquoted comma or a valid
+sequence expression.
+Any incorrectly formed brace expansion is left unchanged.
+A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
+being considered part of a brace expression.
+To avoid conflicts with parameter expansion, the string \fB${\fP
+is not considered eligible for brace expansion, and inhibits brace
+expansion until the closing \fB}\fP.
+.PP
+This construct is typically used as shorthand when the common
+prefix of the strings to be generated is longer than in the
+above example:
+.RS
+.PP
+mkdir /usr/local/src/bash/{old,new,dist,bugs}
+.RE
+or
+.RS
+chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+.RE
+.PP
+Brace expansion introduces a slight incompatibility with
+historical versions of
+.BR sh .
+.B sh
+does not treat opening or closing braces specially when they
+appear as part of a word, and preserves them in the output.
+.B Bash
+removes braces from words as a consequence of brace
+expansion.  For example, a word entered to
+.B sh
+as \fIfile{1,2}\fP
+appears identically in the output.  The same word is
+output as
+.I file1 file2
+after expansion by
+.BR bash .
+If strict compatibility with
+.B sh
+is desired, start
+.B bash
+with the
+.B +B
+option or disable brace expansion with the
+.B +B
+option to the
+.B set
+command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.SS Tilde Expansion
+If a word begins with an unquoted tilde character (`\fB~\fP'), all of
+the characters preceding the first unquoted slash (or all characters,
+if there is no unquoted slash) are considered a \fItilde-prefix\fP.
+If none of the characters in the tilde-prefix are quoted, the
+characters in the tilde-prefix following the tilde are treated as a
+possible \fIlogin name\fP.
+If this login name is the null string, the tilde is replaced with the
+value of the shell parameter
+.SM
+.BR HOME .
+If
+.SM
+.B HOME
+is unset, the home directory of the user executing the shell is
+substituted instead.
+Otherwise, the tilde-prefix is replaced with the home directory
+associated with the specified login name.
+.PP
+If the tilde-prefix is a `~+', the value of the shell variable
+.SM
+.B PWD
+replaces the tilde-prefix.
+If the tilde-prefix is a `~\-', the value of the shell variable
+.SM
+.BR OLDPWD ,
+if it is set, is substituted.
+If the characters following the tilde in the tilde-prefix consist
+of a number \fIN\fP, optionally prefixed
+by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
+element from the directory stack, as it would be displayed by the
+.B dirs
+builtin invoked with the tilde-prefix as an argument.
+If the characters following the tilde in the tilde-prefix consist of a
+number without a leading `+' or `\-', `+' is assumed.
+.PP
+If the login name is invalid, or the tilde expansion fails, the word
+is unchanged.
+.PP
+Each variable assignment is checked for unquoted tilde-prefixes immediately
+following a
+.B :
+or the first
+.BR = .
+In these cases, tilde expansion is also performed.
+Consequently, one may use filenames with tildes in assignments to
+.SM
+.BR PATH ,
+.SM
+.BR MAILPATH ,
+and
+.SM
+.BR CDPATH ,
+and the shell assigns the expanded value.
+.PP
+Bash also performs tilde expansion on words satisfying the conditions of
+variable assignments (as described above under
+.SM
+.BR PARAMETERS )
+when they appear as arguments to simple commands.
+Bash does not do this, except for the \fIdeclaration\fP commands listed
+above, when in \fIposix mode\fP.
+.SS Parameter Expansion
+The `\fB$\fP' character introduces parameter expansion,
+command substitution, or arithmetic expansion.  The parameter name
+or symbol to be expanded may be enclosed in braces, which
+are optional but serve to protect the variable to be expanded from
+characters immediately following it which could be
+interpreted as part of the name.
+.PP
+When braces are used, the matching ending brace is the first `\fB}\fP'
+not escaped by a backslash or within a quoted string, and not within an
+embedded arithmetic expansion, command substitution, or parameter
+expansion.
+.PP
+.PD 0
+.TP
+${\fIparameter\fP}
+The value of \fIparameter\fP is substituted.  The braces are required
+when
+.I parameter
+is a positional parameter with more than one digit,
+or when
+.I parameter
+is followed by a character which is not to be
+interpreted as part of its name.
+The \fIparameter\fP is a shell parameter as described above
+\fBPARAMETERS\fP) or an array reference (\fBArrays\fP).
+.PD
+.PP
+If the first character of \fIparameter\fP is an exclamation point (\fB!\fP),
+and \fIparameter\fP is not a \fInameref\fP,
+it introduces a level of indirection.
+\fBBash\fP uses the value formed by expanding the rest of
+\fIparameter\fP as the new \fIparameter\fP; this is then
+expanded and that value is used in the rest of the expansion, rather
+than the expansion of the original \fIparameter\fP.
+This is known as \fIindirect expansion\fP.
+The value is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+If \fIparameter\fP is a nameref, this expands to the name of the
+parameter referenced by \fIparameter\fP instead of performing the
+complete indirect expansion.
+The exceptions to this are the expansions of ${\fB!\fP\fIprefix\fP\fB*\fP} and
+${\fB!\fP\fIname\fP[\fI@\fP]} described below.
+The exclamation point must immediately follow the left brace in order to
+introduce indirection.
+.PP
+In each of the cases below, \fIword\fP is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+.PP
+When not performing substring expansion, using the forms documented below
+(e.g., \fB:-\fP),
+\fBbash\fP tests for a parameter that is unset or null.  Omitting the colon
+results in a test only for a parameter that is unset.
+.PP
+.PD 0
+.TP
+${\fIparameter\fP\fB:\-\fP\fIword\fP}
+\fBUse Default Values\fP.  If
+.I parameter
+is unset or null, the expansion of
+.I word
+is substituted.  Otherwise, the value of
+.I parameter
+is substituted.
+.TP
+${\fIparameter\fP\fB:=\fP\fIword\fP}
+\fBAssign Default Values\fP.
+If
+.I parameter
+is unset or null, the expansion of
+.I word
+is assigned to
+.IR parameter .
+The value of
+.I parameter
+is then substituted.  Positional parameters and special parameters may
+not be assigned to in this way.
+.TP
+${\fIparameter\fP\fB:?\fP\fIword\fP}
+\fBDisplay Error if Null or Unset\fP.
+If
+.I parameter
+is null or unset, the expansion of \fIword\fP (or a message to that effect
+if
+.I word
+is not present) is written to the standard error and the shell, if it
+is not interactive, exits.  Otherwise, the value of \fIparameter\fP is
+substituted.
+.TP
+${\fIparameter\fP\fB:+\fP\fIword\fP}
+\fBUse Alternate Value\fP.
+If
+.I parameter
+is null or unset, nothing is substituted, otherwise the expansion of
+.I word
+is substituted.
+.TP
+${\fIparameter\fP\fB:\fP\fIoffset\fP}
+.PD 0
+.TP
+${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
+.PD
+\fBSubstring Expansion\fP.
+Expands to up to \fIlength\fP characters of the value of \fIparameter\fP
+starting at the character specified by \fIoffset\fP.
+If \fIparameter\fP is \fB@\fP, an indexed array subscripted by
+\fB@\fP or \fB*\fP, or an associative array name, the results differ as
+described below.
+If \fIlength\fP is omitted, expands to the substring of the value of
+\fIparameter\fP starting at the character specified by \fIoffset\fP
+and extending to the end of the value.
+\fIlength\fP and \fIoffset\fP are arithmetic expressions (see
+.SM
+.B
+ARITHMETIC EVALUATION
+below).
+.sp 1
+If \fIoffset\fP evaluates to a number less than zero, the value
+is used as an offset in characters
+from the end of the value of \fIparameter\fP.
+If \fIlength\fP evaluates to a number less than zero,
+it is interpreted as an offset in characters
+from the end of the value of \fIparameter\fP rather than
+a number of characters, and the expansion is the characters between
+\fIoffset\fP and that result.
+Note that a negative offset must be separated from the colon by at least
+one space to avoid being confused with the \fB:-\fP expansion.
+.sp 1
+If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
+parameters beginning at \fIoffset\fP.
+A negative \fIoffset\fP is taken relative to one greater than the greatest
+positional parameter, so an offset of \-1 evaluates to the last positional
+parameter.
+It is an expansion error if \fIlength\fP evaluates to a number less than
+zero.
+.sp 1
+If \fIparameter\fP is an indexed array name subscripted by @ or *,
+the result is the \fIlength\fP
+members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
+A negative \fIoffset\fP is taken relative to one greater than the maximum
+index of the specified array.
+It is an expansion error if \fIlength\fP evaluates to a number less than
+zero.
+.sp 1
+Substring expansion applied to an associative array produces undefined
+results.
+.sp 1
+Substring indexing is zero-based unless the positional parameters
+are used, in which case the indexing starts at 1 by default.
+If \fIoffset\fP is 0, and the positional parameters are used, \fB$0\fP is
+prefixed to the list.
+.TP
+${\fB!\fP\fIprefix\fP\fB*\fP}
+.PD 0
+.TP
+${\fB!\fP\fIprefix\fP\fB@\fP}
+.PD
+\fBNames matching prefix\fP.
+Expands to the names of variables whose names begin with \fIprefix\fP,
+separated by the first character of the
+.SM
+.B IFS
+special variable.
+When \fI@\fP is used and the expansion appears within double quotes, each
+variable name expands to a separate word.
+.TP
+${\fB!\fP\fIname\fP[\fI@\fP]}
+.PD 0
+.TP
+${\fB!\fP\fIname\fP[\fI*\fP]}
+.PD
+\fBList of array keys\fP.
+If \fIname\fP is an array variable, expands to the list of array indices
+(keys) assigned in \fIname\fP.
+If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
+otherwise.
+When \fI@\fP is used and the expansion appears within double quotes, each
+key expands to a separate word.
+.TP
+${\fB#\fP\fIparameter\fP}
+\fBParameter length\fP.
+The length in characters of the value of \fIparameter\fP is substituted.
+If
+.I parameter
+is
+.B *
+or
+.BR @ ,
+the value substituted is the number of positional parameters.
+If
+.I parameter
+is an array name subscripted by
+.B *
+or
+.BR @ ,
+the value substituted is the number of elements in the array.
+If
+.I parameter
+is an indexed array name subscripted by a negative number, that number is
+interpreted as relative to one greater than the maximum index of
+\fIparameter\fP, so negative indices count back from the end of the
+array, and an index of \-1 references the last element.
+.TP
+${\fIparameter\fP\fB#\fP\fIword\fP}
+.PD 0
+.TP
+${\fIparameter\fP\fB##\fP\fIword\fP}
+.PD
+\fBRemove matching prefix pattern\fP.
+The
+.I word
+is expanded to produce a pattern just as in pathname
+expansion, and matched against the expanded value of
+.I parameter
+using the rules described under
+.B Pattern Matching
+below.
+If the pattern matches the beginning of
+the value of
+.IR parameter ,
+then the result of the expansion is the expanded value of
+.I parameter
+with the shortest matching pattern (the ``\fB#\fP'' case) or the
+longest matching pattern (the ``\fB##\fP'' case) deleted.
+If
+.I parameter
+is
+.B @
+or
+.BR * ,
+the pattern removal operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+.I parameter
+is an array variable subscripted with
+.B @
+or
+.BR * ,
+the pattern removal operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+.TP
+${\fIparameter\fP\fB%\fP\fIword\fP}
+.PD 0
+.TP
+${\fIparameter\fP\fB%%\fP\fIword\fP}
+.PD
+\fBRemove matching suffix pattern\fP.
+The \fIword\fP is expanded to produce a pattern just as in
+pathname expansion, and matched against the expanded value of
+.I parameter
+using the rules described under
+.B Pattern Matching
+below.
+If the pattern matches a trailing portion of the expanded value of
+.IR parameter ,
+then the result of the expansion is the expanded value of
+.I parameter
+with the shortest matching pattern (the ``\fB%\fP'' case) or the
+longest matching pattern (the ``\fB%%\fP'' case) deleted.
+If
+.I parameter
+is
+.B @
+or
+.BR * ,
+the pattern removal operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+.I parameter
+is an array variable subscripted with
+.B @
+or
+.BR * ,
+the pattern removal operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+.TP
+${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
+\fBPattern substitution\fP.
+The \fIpattern\fP is expanded to produce a pattern just as in
+pathname expansion,
+\fIParameter\fP is expanded and the longest match of \fIpattern\fP
+against its value is replaced with \fIstring\fP.
+The match is performed using the rules described under
+.B Pattern Matching
+below.
+If \fIpattern\fP begins with \fB/\fP, all matches of \fIpattern\fP are
+replaced with \fIstring\fP.  Normally only the first match is replaced.
+If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
+of the expanded value of \fIparameter\fP.
+If \fIpattern\fP begins with \fB%\fP, it must match at the end
+of the expanded value of \fIparameter\fP.
+If \fIstring\fP is null, matches of \fIpattern\fP are deleted
+and the \fB/\fP following \fIpattern\fP may be omitted.
+If the
+.B nocasematch
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+If
+.I parameter
+is
+.B @
+or
+.BR * ,
+the substitution operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+.I parameter
+is an array variable subscripted with
+.B @
+or
+.BR * ,
+the substitution operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+.TP
+${\fIparameter\fP\fB^\fP\fIpattern\fP}
+.PD 0
+.TP
+${\fIparameter\fP\fB^^\fP\fIpattern\fP}
+.TP
+${\fIparameter\fP\fB,\fP\fIpattern\fP}
+.TP
+${\fIparameter\fP\fB,,\fP\fIpattern\fP}
+.PD
+\fBCase modification\fP.
+This expansion modifies the case of alphabetic characters in \fIparameter\fP.
+The \fIpattern\fP is expanded to produce a pattern just as in
+pathname expansion.
+Each character in the expanded value of \fIparameter\fP is tested against
+\fIpattern\fP, and, if it matches the pattern, its case is converted.
+The pattern should not attempt to match more than one character.
+The \fB^\fP operator converts lowercase letters matching \fIpattern\fP
+to uppercase; the \fB,\fP operator converts matching uppercase letters
+to lowercase.
+The \fB^^\fP and \fB,,\fP expansions convert each matched character in the
+expanded value; the \fB^\fP and \fB,\fP expansions match and convert only
+the first character in the expanded value.
+If \fIpattern\fP is omitted, it is treated like a \fB?\fP, which matches
+every character.
+If
+.I parameter
+is
+.B @
+or
+.BR * ,
+the case modification operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+.I parameter
+is an array variable subscripted with
+.B @
+or
+.BR * ,
+the case modification operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+.TP
+${\fIparameter\fP\fB@\fP\fIoperator\fP}
+\fBParameter transformation\fP.
+The expansion is either a transformation of the value of \fIparameter\fP
+or information about \fIparameter\fP itself, depending on the value of
+\fIoperator\fP.  Each \fIoperator\fP is a single letter:
+.sp 1
+.RS
+.PD 0
+.TP
+.B U
+The expansion is a string that is the value of \fIparameter\fP with lowercase
+alphabetic characters converted to uppercase.
+.TP
+.B u
+The expansion is a string that is the value of \fIparameter\fP with the first
+character converted to uppercase, if it is alphabetic.
+.TP
+.B L
+The expansion is a string that is the value of \fIparameter\fP with uppercase
+alphabetic characters converted to lowercase.
+.TP
+.B Q
+The expansion is a string that is the value of \fIparameter\fP quoted in a
+format that can be reused as input.
+.TP
+.B E
+The expansion is a string that is the value of \fIparameter\fP with backslash
+escape sequences expanded as with the \fB$'...'\fP quoting mechanism.
+.TP
+.B P
+The expansion is a string that is the result of expanding the value of
+\fIparameter\fP as if it were a prompt string (see \fBPROMPTING\fP below).
+.TP
+.B A
+The expansion is a string in the form of
+an assignment statement or \fBdeclare\fP command that, if
+evaluated, will recreate \fIparameter\fP with its attributes and value.
+.TP
+.B K
+Produces a possibly-quoted version of the value of \fIparameter\fP,
+except that it prints the values of
+indexed and associative arrays as a sequence of quoted key-value pairs
+(see \fBArrays\fP above).
+.TP
+.B a
+The expansion is a string consisting of flag values representing
+\fIparameter\fP's attributes.
+.PD
+.PP
+If
+.I parameter
+is
+.B @
+or
+.BR * ,
+the operation is applied to each positional
+parameter in turn, and the expansion is the resultant list.
+If
+.I parameter
+is an array variable subscripted with
+.B @
+or
+.BR * ,
+the operation is applied to each member of the
+array in turn, and the expansion is the resultant list.
+.sp 1
+The result of the expansion is subject to word splitting and pathname
+expansion as described below.
+.RE
+.SS Command Substitution
+\fICommand substitution\fP allows the output of a command to replace
+the command name.  There are two forms:
+.RS
+.PP
+\fB$(\fP\fIcommand\fP\|\fB)\fP
+.RE
+or
+.RS
+\fB\`\fP\fIcommand\fP\fB\`\fP
+.RE
+.PP
+.B Bash
+performs the expansion by executing \fIcommand\fP in a subshell environment
+and replacing the command substitution with the standard output of the
+command, with any trailing newlines deleted.
+Embedded newlines are not deleted, but they may be removed during
+word splitting.
+The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
+the equivalent but faster \fB$(< \fIfile\fP)\fR.
+.PP
+When the old-style backquote form of substitution is used,
+backslash retains its literal meaning except when followed by
+.BR $ ,
+.BR \` ,
+or
+.BR \e .
+The first backquote not preceded by a backslash terminates the
+command substitution.
+When using the $(\^\fIcommand\fP\|) form, all characters between the
+parentheses make up the command; none are treated specially.
+.PP
+Command substitutions may be nested.  To nest when using the backquoted form,
+escape the inner backquotes with backslashes.
+.PP
+If the substitution appears within double quotes, word splitting and
+pathname expansion are not performed on the results.
+.SS Arithmetic Expansion
+Arithmetic expansion allows the evaluation of an arithmetic expression
+and the substitution of the result.  The format for arithmetic expansion is:
+.RS
+.PP
+\fB$((\fP\fIexpression\fP\fB))\fP
+.RE
+.PP
+The
+.I expression
+is treated as if it were within double quotes, but a double quote
+inside the parentheses is not treated specially.
+All tokens in the expression undergo parameter and variable expansion,
+command substitution, and quote removal.
+The result is treated as the arithmetic expression to be evaluated.
+Arithmetic expansions may be nested.
+.PP
+The evaluation is performed according to the rules listed below under
+.SM
+.BR "ARITHMETIC EVALUATION" .
+If
+.I expression
+is invalid,
+.B bash
+prints a message indicating failure and no substitution occurs.
+.SS Process Substitution
+\fIProcess substitution\fP allows a process's input or output to be
+referred to using a filename.
+It takes the form of
+\fB<(\fP\fIlist\^\fP\fB)\fP
+or
+\fB>(\fP\fIlist\^\fP\fB)\fP.
+The process \fIlist\fP is run asynchronously, and its input or output
+appears as a filename.
+This filename is
+passed as an argument to the current command as the result of the
+expansion.
+If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
+the file will provide input for \fIlist\fP.  If the
+\fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
+argument should be read to obtain the output of \fIlist\fP.
+Process substitution is supported on systems that support named
+pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
+.PP
+When available, process substitution is performed
+simultaneously with parameter and variable expansion,
+command substitution,
+and arithmetic expansion.
+.SS Word Splitting
+The shell scans the results of
+parameter expansion,
+command substitution,
+and
+arithmetic expansion
+that did not occur within double quotes for
+.IR "word splitting" .
+.PP
+The shell treats each character of
+.SM
+.B IFS
+as a delimiter, and splits the results of the other
+expansions into words using these characters as field terminators.
+If
+.SM
+.B IFS
+is unset, or its
+value is exactly
+.BR <space><tab><newline> ,
+the default, then
+sequences of
+.BR <space> ,
+.BR <tab> ,
+and
+.B <newline>
+at the beginning and end of the results of the previous
+expansions are ignored, and
+any sequence of
+.SM
+.B IFS
+characters not at the beginning or end serves to delimit words.
+If
+.SM
+.B IFS
+has a value other than the default, then sequences of
+the whitespace characters
+.BR space ,
+.BR tab ,
+and
+.B newline
+are ignored at the beginning and end of the
+word, as long as the whitespace character is in the
+value of
+.SM
+.B IFS
+(an
+.SM
+.B IFS
+whitespace character).
+Any character in
+.SM
+.B IFS
+that is not
+.SM
+.B IFS
+whitespace, along with any adjacent
+.SM
+.B IFS
+whitespace characters, delimits a field.
+A sequence of
+.SM
+.B IFS
+whitespace characters is also treated as a delimiter.
+If the value of
+.SM
+.B IFS
+is null, no word splitting occurs.
+.PP
+Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) are retained
+and passed to commands as empty strings.
+Unquoted implicit null arguments, resulting from the expansion of
+parameters that have no values, are removed.
+If a parameter with no value is expanded within double quotes, a
+null argument results and is retained
+and passed to a command as an empty string.
+When a quoted null argument appears as part of a word whose expansion is
+non-null, the null argument is removed.
+That is, the word
+\f(CW\-d\(aq\^\(aq\fP becomes \f(CW\-d\fP after word splitting and
+null argument removal.
+.PP
+Note that if no expansion occurs, no splitting
+is performed.
+.SS Pathname Expansion
+After word splitting,
+unless the
+.B \-f
+option has been set,
+.B bash
+scans each word for the characters
+.BR * ,
+.BR ? ,
+and
+.BR [ .
+If one of these characters appears, and is not quoted, then the word is
+regarded as a
+.IR pattern ,
+and replaced with an alphabetically sorted list of
+filenames matching the pattern
+(see
+.SM
+.B "Pattern Matching"
+below).
+If no matching filenames are found,
+and the shell option
+.B nullglob
+is not enabled, the word is left unchanged.
+If the
+.B nullglob
+option is set, and no matches are found,
+the word is removed.
+If the
+.B 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
+.B nocaseglob
+is enabled, the match is performed without regard to the case
+of alphabetic characters.
+When a pattern is used for pathname expansion,
+the character
+.B ``.''
+at the start of a name or immediately following a slash
+must be matched explicitly, unless the shell option
+.B dotglob
+is set.
+The filenames
+.B ``.''
+and
+.B ``..''
+must always be matched explicitly, even if
+.B dotglob
+is set.
+In other cases, the
+.B ``.''
+character is not treated specially.
+When matching a pathname, the slash character must always be
+matched explicitly by a slash in the pattern, but in other matching
+contexts it can be matched by a special pattern character as described
+below under
+.SM
+.BR "Pattern Matching" .
+See the description of
+.B shopt
+below under
+.SM
+.B SHELL BUILTIN COMMANDS
+for a description of the
+.BR nocaseglob ,
+.BR nullglob ,
+.BR failglob ,
+and
+.B dotglob
+shell options.
+.PP
+The
+.SM
+.B GLOBIGNORE
+shell variable may be used to restrict the set of file names matching a
+.IR pattern .
+If
+.SM
+.B GLOBIGNORE
+is set, each matching file name that also matches one of the patterns in
+.SM
+.B GLOBIGNORE
+is removed from the list of matches.
+If the \fBnocaseglob\fP option is set, the matching against the patterns in
+.SM
+.B GLOBIGNORE
+is performed without regard to case.
+The filenames
+.B ``.''
+and
+.B ``..''
+are always ignored when
+.SM
+.B GLOBIGNORE
+is set and not null.  However, setting
+.SM
+.B GLOBIGNORE
+to a non-null value has the effect of enabling the
+.B dotglob
+shell option, so all other filenames beginning with a
+.B ``.''
+will match.
+To get the old behavior of ignoring filenames beginning with a
+.BR ``.'' ,
+make
+.B ``.*''
+one of the patterns in
+.SM
+.BR GLOBIGNORE .
+The
+.B dotglob
+option is disabled when
+.SM
+.B GLOBIGNORE
+is unset.
+The pattern matching honors the setting of the \fBextglob\fP shell
+option.
+.PP
+\fBPattern Matching\fP
+.PP
+Any character that appears in a pattern, other than the special pattern
+characters described below, matches itself.  The NUL character may not
+occur in a pattern.  A backslash escapes the following character; the
+escaping backslash is discarded when matching.
+The special pattern characters must be quoted if
+they are to be matched literally.
+.PP
+The special pattern characters have the following meanings:
+.PP
+.PD 0
+.RS
+.TP
+.B *
+Matches any string, including the null string.
+When the \fBglobstar\fP shell option is enabled, and \fB*\fP is used in
+a pathname expansion context, two adjacent \fB*\fPs used as a single
+pattern will match all files and zero or more directories and
+subdirectories.
+If followed by a \fB/\fP, two adjacent \fB*\fPs will match only directories
+and subdirectories.
+.TP
+.B ?
+Matches any single character.
+.TP
+.B [...]
+Matches any one of the enclosed characters.  A pair of characters
+separated by a hyphen denotes a
+\fIrange expression\fP;
+any character that falls between those two characters, inclusive,
+using the current locale's collating sequence and character set,
+is matched.  If the first character following the
+.B [
+is a
+.B !
+or a
+.B ^
+then any character not enclosed is matched.
+The sorting order of characters in range expressions is determined by
+the current locale and the values of the
+.SM
+.B LC_COLLATE
+or
+.SM
+.B LC_ALL
+shell variables, if set.
+To obtain the traditional interpretation of range expressions, where
+.B [a\-d]
+is equivalent to
+.BR [abcd] ,
+set value of the
+.B LC_ALL
+shell variable to
+.BR C ,
+or enable the
+.B globasciiranges
+shell option.
+A
+.B \-
+may be matched by including it as the first or last character
+in the set.
+A
+.B ]
+may be matched by including it as the first character
+in the set.
+.br
+.if t .sp 0.5
+.if n .sp 1
+Within
+.B [
+and
+.BR ] ,
+\fIcharacter classes\fP can be specified using the syntax
+\fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
+following classes defined in the POSIX standard:
+.PP
+.RS
+.B
+.if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
+.if t alnum   alpha   ascii   blank   cntrl   digit   graph   lower   print   punct   space   upper   word   xdigit
+.br
+A character class matches any character belonging to that class.
+The \fBword\fP character class matches letters, digits, and the character _.
+.br
+.if t .sp 0.5
+.if n .sp 1
+Within
+.B [
+and
+.BR ] ,
+an \fIequivalence class\fP can be specified using the syntax
+\fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
+same collation weight (as defined by the current locale) as
+the character \fIc\fP.
+.br
+.if t .sp 0.5
+.if n .sp 1
+Within
+.B [
+and
+.BR ] ,
+the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
+\fIsymbol\fP.
+.RE
+.RE
+.PD
+.PP
+If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
+builtin, several extended pattern matching operators are recognized.
+In the following description, a \fIpattern-list\fP is a list of one
+or more patterns separated by a \fB|\fP.
+Composite patterns may be formed using one or more of the following
+sub-patterns:
+.sp 1
+.PD 0
+.RS
+.TP
+\fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
+Matches zero or one occurrence of the given patterns
+.TP
+\fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
+Matches zero or more occurrences of the given patterns
+.TP
+\fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
+Matches one or more occurrences of the given patterns
+.TP
+\fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
+Matches one of the given patterns
+.TP
+\fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
+Matches anything except one of the given patterns
+.RE
+.PD
+.PP
+Complicated extended pattern matching against long strings is slow,
+especially when the patterns contain alternations and the strings
+contain multiple matches.
+Using separate matches against shorter strings, or using arrays of
+strings instead of a single long string, may be faster.
+.SS Quote Removal
+After the preceding expansions, all unquoted occurrences of the
+characters
+.BR \e ,
+.BR \(aq ,
+and \^\f3"\fP\^ that did not result from one of the above
+expansions are removed.
+.SH REDIRECTION
+Before a command is executed, its input and output
+may be
+.I redirected
+using a special notation interpreted by the shell.
+Redirection allows commands' file handles to be
+duplicated, opened, closed,
+made to refer to different files,
+and can change the files the command reads from and writes to.
+Redirection may also be used to modify file handles in the
+current shell execution environment.
+The following redirection
+operators may precede or appear anywhere within a
+.I simple command
+or may follow a
+.IR command .
+Redirections are processed in the order they appear, from
+left to right.
+.PP
+Each redirection that may be preceded by a file descriptor number
+may instead be preceded by a word of the form {\fIvarname\fP}.
+In this case, for each redirection operator except
+>&- and <&-, the shell will allocate a file descriptor greater
+than or equal to 10 and assign it to \fIvarname\fP.
+If >&- or <&- is preceded
+by {\fIvarname\fP}, the value of \fIvarname\fP defines the file
+descriptor to close.
+If {\fIvarname\fP} is supplied, the redirection persists beyond
+the scope of the command, allowing the shell programmer to manage
+the file descriptor himself.
+.PP
+In the following descriptions, if the file descriptor number is
+omitted, and the first character of the redirection operator is
+.BR < ,
+the redirection refers to the standard input (file descriptor
+0).  If the first character of the redirection operator is
+.BR > ,
+the redirection refers to the standard output (file descriptor
+1).
+.PP
+The word following the redirection operator in the following
+descriptions, unless otherwise noted, is subjected to
+brace expansion, tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, quote removal,
+pathname expansion, and word splitting.
+If it expands to more than one word,
+.B bash
+reports an error.
+.PP
+Note that the order of redirections is significant.  For example,
+the command
+.RS
+.PP
+ls \fB>\fP dirlist 2\fB>&\fP1
+.RE
+.PP
+directs both standard output and standard error to the file
+.IR dirlist ,
+while the command
+.RS
+.PP
+ls 2\fB>&\fP1 \fB>\fP dirlist
+.RE
+.PP
+directs only the standard output to file
+.IR dirlist ,
+because the standard error was duplicated from the standard output
+before the standard output was redirected to
+.IR dirlist .
+.PP
+\fBBash\fP handles several filenames specially when they are used in
+redirections, as described in the following table.
+If the operating system on which \fBbash\fP is running provides these
+special files, bash will use them; otherwise it will emulate them
+internally with the behavior described below.
+.RS
+.PP
+.PD 0
+.TP
+.B /dev/fd/\fIfd\fP
+If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
+.TP
+.B /dev/stdin
+File descriptor 0 is duplicated.
+.TP
+.B /dev/stdout
+File descriptor 1 is duplicated.
+.TP
+.B /dev/stderr
+File descriptor 2 is duplicated.
+.TP
+.B /dev/tcp/\fIhost\fP/\fIport\fP
+If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
+is an integer port number or service name, \fBbash\fP attempts to open
+the corresponding TCP socket.
+.TP
+.B /dev/udp/\fIhost\fP/\fIport\fP
+If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
+is an integer port number or service name, \fBbash\fP attempts to open
+the corresponding UDP socket.
+.PD
+.RE
+.PP
+A failure to open or create a file causes the redirection to fail.
+.PP
+Redirections using file descriptors greater than 9 should be used with
+care, as they may conflict with file descriptors the shell uses
+internally.
+.SS Redirecting Input
+Redirection of input causes the file whose name results from
+the expansion of
+.I word
+to be opened for reading on file descriptor
+.IR n ,
+or the standard input (file descriptor 0) if
+.I n
+is not specified.
+.PP
+The general format for redirecting input is:
+.RS
+.PP
+[\fIn\fP]\fB<\fP\fIword\fP
+.RE
+.SS Redirecting Output
+Redirection of output causes the file whose name results from
+the expansion of
+.I word
+to be opened for writing on file descriptor
+.IR n ,
+or the standard output (file descriptor 1) if
+.I n
+is not specified.  If the file does not exist it is created;
+if it does exist it is truncated to zero size.
+.PP
+The general format for redirecting output is:
+.RS
+.PP
+[\fIn\fP]\fB>\fP\fIword\fP
+.RE
+.PP
+If the redirection operator is
+.BR > ,
+and the
+.B noclobber
+option to the
+.B set
+builtin has been enabled, the redirection will fail if the file
+whose name results from the expansion of \fIword\fP exists and is
+a regular file.
+If the redirection operator is
+.BR >| ,
+or the redirection operator is
+.B >
+and the
+.B noclobber
+option to the
+.B set
+builtin command is not enabled, the redirection is attempted even
+if the file named by \fIword\fP exists.
+.SS Appending Redirected Output
+Redirection of output in this fashion
+causes the file whose name results from
+the expansion of
+.I word
+to be opened for appending on file descriptor
+.IR n ,
+or the standard output (file descriptor 1) if
+.I n
+is not specified.  If the file does not exist it is created.
+.PP
+The general format for appending output is:
+.RS
+.PP
+[\fIn\fP]\fB>>\fP\fIword\fP
+.RE
+.SS Redirecting 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 redirected to the file whose name is the
+expansion of
+.IR word .
+.PP
+There are two formats for redirecting standard output and
+standard error:
+.RS
+.PP
+\fB&>\fP\fIword\fP
+.RE
+and
+.RS
+\fB>&\fP\fIword\fP
+.RE
+.PP
+Of the two forms, the first is preferred.
+This is semantically equivalent to
+.RS
+.PP
+\fB>\fP\fIword\fP 2\fB>&\fP1
+.RE
+.PP
+When using the second form, \fIword\fP may not expand to a number or
+\fB\-\fP.  If it does, other redirection operators apply
+(see \fBDuplicating File Descriptors\fP below) for compatibility
+reasons.
+.SS 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
+.IR word .
+.PP
+The format for appending standard output and standard error is:
+.RS
+.PP
+\fB&>>\fP\fIword\fP
+.RE
+.PP
+This is semantically equivalent to
+.RS
+.PP
+\fB>>\fP\fIword\fP 2\fB>&\fP1
+.RE
+.PP
+(see \fBDuplicating File Descriptors\fP below).
+.SS Here Documents
+This type of redirection instructs the shell to read input from the
+current source until a line containing only
+.I delimiter
+(with no trailing blanks)
+is seen.  All of
+the lines read up to that point are then used as the standard
+input (or file descriptor \fIn\fP if \fIn\fP is specified) for a command.
+.PP
+The format of here-documents is:
+.RS
+.PP
+.nf
+[\fIn\fP]\fB<<\fP[\fB\-\fP]\fIword\fP
+        \fIhere-document\fP
+\fIdelimiter\fP
+.fi
+.RE
+.PP
+No parameter and variable expansion, command substitution,
+arithmetic expansion, or pathname expansion is performed on
+.IR word .
+If any part of
+.I word
+is quoted, the
+.I delimiter
+is the result of quote removal on
+.IR word ,
+and the lines in the here-document are not expanded.
+If \fIword\fP is unquoted,
+all lines of the here-document are subjected to
+parameter expansion, command substitution, and arithmetic expansion,
+the character sequence
+.B \e<newline>
+is ignored, and
+.B \e
+must be used to quote the characters
+.BR \e ,
+.BR $ ,
+and
+.BR \` .
+.PP
+If the redirection operator is
+.BR <<\- ,
+then all leading tab characters are stripped from input lines and the
+line containing
+.IR delimiter .
+This allows
+here-documents within shell scripts to be indented in a
+natural fashion.
+.SS "Here Strings"
+A variant of here documents, the format is:
+.RS
+.PP
+.nf
+[\fIn\fP]\fB<<<\fP\fIword\fP
+.fi
+.RE
+.PP
+The \fIword\fP undergoes
+tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal.
+Pathname expansion and word splitting are not performed.
+The result is supplied as a single string, with a newline appended,
+to the command on its
+standard input (or file descriptor \fIn\fP if \fIn\fP is specified).
+.SS "Duplicating File Descriptors"
+The redirection operator
+.RS
+.PP
+[\fIn\fP]\fB<&\fP\fIword\fP
+.RE
+.PP
+is used to duplicate input file descriptors.
+If
+.I word
+expands to one or more digits, the file descriptor denoted by
+.I n
+is made to be a copy of that file descriptor.
+If the digits in
+.I word
+do not specify a file descriptor open for input, a redirection error occurs.
+If
+.I word
+evaluates to
+.BR \- ,
+file descriptor
+.I n
+is closed.  If
+.I n
+is not specified, the standard input (file descriptor 0) is used.
+.PP
+The operator
+.RS
+.PP
+[\fIn\fP]\fB>&\fP\fIword\fP
+.RE
+.PP
+is used similarly to duplicate output file descriptors.  If
+.I n
+is not specified, the standard output (file descriptor 1) is used.
+If the digits in
+.I word
+do not specify a file descriptor open for output, a redirection error occurs.
+If
+.I word
+evaluates to
+.BR \- ,
+file descriptor
+.I n
+is closed.
+As a special case, if \fIn\fP is omitted, and \fIword\fP does not
+expand to one or more digits or \fB\-\fP, the standard output and standard
+error are redirected as described previously.
+.SS "Moving File Descriptors"
+The redirection operator
+.RS
+.PP
+[\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
+.RE
+.PP
+moves the file descriptor \fIdigit\fP to file descriptor
+.IR n ,
+or the standard input (file descriptor 0) if \fIn\fP is not specified.
+\fIdigit\fP is closed after being duplicated to \fIn\fP.
+.PP
+Similarly, the redirection operator
+.RS
+.PP
+[\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
+.RE
+.PP
+moves the file descriptor \fIdigit\fP to file descriptor
+.IR n ,
+or the standard output (file descriptor 1) if \fIn\fP is not specified.
+.SS "Opening File Descriptors for Reading and Writing"
+The redirection operator
+.RS
+.PP
+[\fIn\fP]\fB<>\fP\fIword\fP
+.RE
+.PP
+causes the file whose name is the expansion of
+.I word
+to be opened for both reading and writing on file descriptor
+.IR n ,
+or on file descriptor 0 if
+.I n
+is not specified.  If the file does not exist, it is created.
+.SH ALIASES
+\fIAliases\fP allow a string to be substituted for a word when it is used
+as the first word of a simple command.
+The shell maintains a list of aliases that may be set and unset with the
+.B alias
+and
+.B unalias
+builtin commands (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+The first word of each simple command, if unquoted,
+is checked to see if it has an
+alias.  If so, that word is replaced by the text of the alias.
+The characters \fB/\fP, \fB$\fP, \fB\`\fP, and \fB=\fP and
+any of the shell \fImetacharacters\fP 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
+.B ls
+to
+.BR "ls \-F" ,
+for instance, and
+.B bash
+does not try to recursively expand the replacement text.
+If the last character of the alias value is a
+.IR blank ,
+then the next command
+word following the alias is also checked for alias expansion.
+.PP
+Aliases are created and listed with the
+.B alias
+command, and removed with the
+.B unalias
+command.
+.PP
+There is no mechanism for using arguments in the replacement text.
+If arguments are needed, a shell function should be used (see
+.SM
+.B FUNCTIONS
+below).
+.PP
+Aliases are not expanded when the shell is not interactive, unless
+the
+.B expand_aliases
+shell option is set using
+.B shopt
+(see the description of
+.B shopt
+under
+.SM
+\fBSHELL BUILTIN COMMANDS\fP
+below).
+.PP
+The rules concerning the definition and use of aliases are
+somewhat confusing.
+.B Bash
+always reads at least one complete line of input,
+and all lines that make up a compound command,
+before executing any of the commands on that line or the compound command.
+Aliases are expanded when a
+command is read, not when it is executed.  Therefore, an
+alias definition appearing on the same line as another
+command does not take effect until the next line of input is read.
+The commands following the alias definition
+on that line are not affected by the new alias.
+This behavior is also an issue when functions are executed.
+Aliases are expanded when a function definition is read,
+not when the function is executed, because a function definition
+is itself a command.  As a consequence, aliases
+defined in a function are not available until after that
+function is executed.  To be safe, always put
+alias definitions on a separate line, and do not use
+.B alias
+in compound commands.
+.PP
+For almost every purpose, aliases are superseded by
+shell functions.
+.SH FUNCTIONS
+A shell function, defined as described above under
+.SM
+.BR "SHELL GRAMMAR" ,
+stores a series of commands for later execution.
+When the name of a shell function is used as a simple command name,
+the list of commands associated with that function name is executed.
+Functions are executed in the context of the
+current shell; no new process is created to interpret
+them (contrast this with the execution of a shell script).
+When a function is executed, the arguments to the
+function become the positional parameters
+during its execution.
+The special parameter
+.B #
+is updated to reflect the change.  Special parameter \fB0\fP
+is unchanged.
+The first element of the
+.SM
+.B FUNCNAME
+variable is set to the name of the function while the function
+is executing.
+.PP
+All other aspects of the shell execution
+environment are identical between a function and its caller
+with these exceptions: the
+.SM
+.B DEBUG
+and
+.B RETURN
+traps (see the description of the
+.B trap
+builtin under
+.SM
+.B SHELL BUILTIN COMMANDS
+below) are not inherited unless the function has been given the
+\fBtrace\fP attribute (see the description of the
+.SM
+.B declare
+builtin below) or the
+\fB\-o functrace\fP shell option has been enabled with
+the \fBset\fP builtin
+(in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps),
+and the
+.SM
+.B ERR
+trap is not inherited unless the \fB\-o errtrace\fP shell option has
+been enabled.
+.PP
+Variables local to the function may be declared with the
+.B local
+builtin command.  Ordinarily, variables and their values
+are shared between the function and its caller.
+If a variable is declared \fBlocal\fP, the variable's visible scope
+is restricted to that function and its children (including the functions
+it calls).
+Local variables "shadow" variables with the same name declared at
+previous scopes.
+For instance, a local variable declared in a function
+hides a global variable of the same name: references and assignments
+refer to the local variable, leaving the global variable unmodified.
+When the function returns, the global variable is once again visible.
+.PP
+The shell uses \fIdynamic scoping\fP to control a variable's visibility
+within functions.
+With dynamic scoping, visible variables and their values
+are a result of the sequence of function calls that caused execution
+to reach the current function.
+The value of a variable that a function sees depends
+on its value within its caller, if any, whether that caller is
+the "global" scope or another shell function.
+This is also the value that a local variable
+declaration "shadows", and the value that is restored when the function
+returns.
+.PP
+For example, if a variable \fIvar\fP is declared as local in function
+\fIfunc1\fP, and \fIfunc1\fP calls another function \fIfunc2\fP,
+references to \fIvar\fP made from within \fIfunc2\fP will resolve to the
+local variable \fIvar\fP from \fIfunc1\fP, shadowing any global variable
+named \fIvar\fP.
+.PP
+The \fBunset\fP builtin also acts using the same dynamic scope: if a
+variable is local to the current scope, \fBunset\fP will unset it;
+otherwise the unset will refer to the variable found in any calling scope
+as described above.
+If a variable at the current local scope is unset, it will remain so
+until it is reset in that scope or until the function returns.
+Once the function returns, any instance of the variable at a previous
+scope will become visible.
+If the unset acts on a variable at a previous scope, any instance of a
+variable with that name that had been shadowed will become visible.
+.PP
+The \fBFUNCNEST\fP variable, if set to a numeric value greater
+than 0, defines a maximum function nesting level.  Function
+invocations that exceed the limit cause the entire command to
+abort.
+.PP
+If the builtin command
+.B return
+is executed in a function, the function completes and
+execution resumes with the next command after the function
+call.
+Any command associated with the \fBRETURN\fP trap is executed
+before execution resumes.
+When a function completes, the values of the
+positional parameters and the special parameter
+.B #
+are restored to the values they had prior to the function's
+execution.
+.PP
+Function names and definitions may be listed with the
+.B \-f
+option to the
+.B declare
+or
+.B typeset
+builtin commands.  The
+.B \-F
+option to
+.B declare
+or
+.B typeset
+will list the function names only
+(and optionally the source file and line number, if the \fBextdebug\fP
+shell option is enabled).
+Functions may be exported so that subshells
+automatically have them defined with the
+.B \-f
+option to the
+.B export
+builtin.
+A function definition may be deleted using the \fB\-f\fP option to
+the
+.B unset
+builtin.
+.PP
+Functions may be recursive.
+The \fBFUNCNEST\fP variable may be used to limit the depth of the
+function call stack and restrict the number of function invocations.
+By default, no limit is imposed on the number of recursive calls.
+.SH "ARITHMETIC EVALUATION"
+The shell allows arithmetic expressions to be evaluated, under
+certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
+commands, the \fB((\fP compound command, and \fBArithmetic Expansion\fP).
+Evaluation is done in fixed-width integers with no check for overflow,
+though division by 0 is trapped and flagged as an error.
+The operators and their precedence, associativity, and values
+are the same as in the C language.
+The following list of operators is grouped into levels of
+equal-precedence operators.
+The levels are listed in order of decreasing precedence.
+.PP
+.PD 0
+.TP
+.B \fIid\fP++ \fIid\fP\-\-
+variable post-increment and post-decrement
+.TP
+.B \- +
+unary minus and plus
+.TP
+.B ++\fIid\fP \-\-\fIid\fP
+variable pre-increment and pre-decrement
+.TP
+.B ! ~
+logical and bitwise negation
+.TP
+.B **
+exponentiation
+.TP
+.B * / %
+multiplication, division, remainder
+.TP
+.B + \-
+addition, subtraction
+.TP
+.B << >>
+left and right bitwise shifts
+.TP
+.B <= >= < >
+comparison
+.TP
+.B == !=
+equality and inequality
+.TP
+.B &
+bitwise AND
+.TP
+.B ^
+bitwise exclusive OR
+.TP
+.B |
+bitwise OR
+.TP
+.B &&
+logical AND
+.TP
+.B ||
+logical OR
+.TP
+.B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
+conditional operator
+.TP
+.B = *= /= %= += \-= <<= >>= &= ^= |=
+assignment
+.TP
+.B \fIexpr1\fP , \fIexpr2\fP
+comma
+.PD
+.PP
+Shell variables are allowed as operands; parameter expansion is
+performed before the expression is evaluated.
+Within an expression, shell variables may also be referenced by name
+without using the parameter expansion syntax.
+A shell variable that is null or unset evaluates to 0 when referenced
+by name without using the parameter expansion syntax.
+The value of a variable is evaluated as an arithmetic expression
+when it is referenced, or when a variable which has been given the
+\fIinteger\fP attribute using \fBdeclare \-i\fP is assigned a value.
+A null value evaluates to 0.
+A shell variable need not have its \fIinteger\fP attribute
+turned on to be used in an expression.
+.PP
+Integer constants follow the C language definition, without suffixes or
+character constants.
+Constants with a leading 0 are interpreted as octal numbers.
+A leading 0x or 0X denotes hexadecimal.
+Otherwise, numbers take the form [\fIbase#\fP]n, where the optional \fIbase\fP
+is a decimal number between 2 and 64 representing the arithmetic
+base, and \fIn\fP is a number in that base.
+If \fIbase#\fP is omitted, then base 10 is used.
+When specifying \fIn\fP,
+if a non-digit is required,
+the digits greater than 9 are represented by the lowercase letters,
+the uppercase letters, @, and _, in that order.
+If \fIbase\fP is less than or equal to 36, lowercase and uppercase
+letters may be used interchangeably to represent numbers between 10
+and 35.
+.PP
+Operators are evaluated in order of precedence.  Sub-expressions in
+parentheses are evaluated first and may override the precedence
+rules above.
+.SH "CONDITIONAL EXPRESSIONS"
+Conditional expressions are used by the \fB[[\fP compound command and
+the \fBtest\fP and \fB[\fP builtin commands to test file attributes
+and perform string and arithmetic comparisons.
+The \fBtest\fP and \fB[\fP commands determine their behavior based on
+the number of arguments; see the descriptions of those commands for any
+other command-specific actions.
+.PP
+Expressions are formed from the following unary or binary primaries.
+\fBBash\fP handles several filenames specially when they are used in
+expressions.
+If the operating system on which \fBbash\fP is running provides these
+special files, bash will use them; otherwise it will emulate them
+internally with this behavior:
+If any \fIfile\fP argument to one of the primaries is of the form
+\fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
+If the \fIfile\fP argument to one of the primaries is one of
+\fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
+descriptor 0, 1, or 2, respectively, is checked.
+.PP
+Unless otherwise specified, primaries that operate on files follow symbolic
+links and operate on the target of the link, rather than the link itself.
+.if t .sp 0.5
+.if n .sp 1
+When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
+lexicographically using the current locale.
+The \fBtest\fP command sorts using ASCII ordering.
+.sp 1
+.PD 0
+.TP
+.B \-a \fIfile\fP
+True if \fIfile\fP exists.
+.TP
+.B \-b \fIfile\fP
+True if \fIfile\fP exists and is a block special file.
+.TP
+.B \-c \fIfile\fP
+True if \fIfile\fP exists and is a character special file.
+.TP
+.B \-d \fIfile\fP
+True if \fIfile\fP exists and is a directory.
+.TP
+.B \-e \fIfile\fP
+True if \fIfile\fP exists.
+.TP
+.B \-f \fIfile\fP
+True if \fIfile\fP exists and is a regular file.
+.TP
+.B \-g \fIfile\fP
+True if \fIfile\fP exists and is set-group-id.
+.TP
+.B \-h \fIfile\fP
+True if \fIfile\fP exists and is a symbolic link.
+.TP
+.B \-k \fIfile\fP
+True if \fIfile\fP exists and its ``sticky'' bit is set.
+.TP
+.B \-p \fIfile\fP
+True if \fIfile\fP exists and is a named pipe (FIFO).
+.TP
+.B \-r \fIfile\fP
+True if \fIfile\fP exists and is readable.
+.TP
+.B \-s \fIfile\fP
+True if \fIfile\fP exists and has a size greater than zero.
+.TP
+.B \-t \fIfd\fP
+True if file descriptor
+.I fd
+is open and refers to a terminal.
+.TP
+.B \-u \fIfile\fP
+True if \fIfile\fP exists and its set-user-id bit is set.
+.TP
+.B \-w \fIfile\fP
+True if \fIfile\fP exists and is writable.
+.TP
+.B \-x \fIfile\fP
+True if \fIfile\fP exists and is executable.
+.TP
+.B \-G \fIfile\fP
+True if \fIfile\fP exists and is owned by the effective group id.
+.TP
+.B \-L \fIfile\fP
+True if \fIfile\fP exists and is a symbolic link.
+.TP
+.B \-N \fIfile\fP
+True if \fIfile\fP exists and has been modified since it was last read.
+.TP
+.B \-O \fIfile\fP
+True if \fIfile\fP exists and is owned by the effective user id.
+.TP
+.B \-S \fIfile\fP
+True if \fIfile\fP exists and is a socket.
+.TP
+\fIfile1\fP \fB\-ef\fP \fIfile2\fP
+True if \fIfile1\fP and \fIfile2\fP refer to the same device and
+inode numbers.
+.TP
+\fIfile1\fP \-\fBnt\fP \fIfile2\fP
+True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
+or if \fIfile1\fP exists and \fPfile2\fP does not.
+.TP
+\fIfile1\fP \-\fBot\fP \fIfile2\fP
+True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
+and \fIfile1\fP does not.
+.TP
+.B \-o \fIoptname\fP
+True if the shell option
+.I optname
+is enabled.
+See the list of options under the description of the
+.B \-o
+option to the
+.B set
+builtin below.
+.TP
+.B \-v \fIvarname\fP
+True if the shell variable
+.I varname
+is set (has been assigned a value).
+.TP
+.B \-R \fIvarname\fP
+True if the shell variable
+.I varname
+is set and is a name reference.
+.TP
+.B \-z \fIstring\fP
+True if the length of \fIstring\fP is zero.
+.TP
+\fIstring\fP
+.PD 0
+.TP
+.B \-n \fIstring\fP
+.PD
+True if the length of
+.I string
+is non-zero.
+.TP
+\fIstring1\fP \fB==\fP \fIstring2\fP
+.PD 0
+.TP
+\fIstring1\fP \fB=\fP \fIstring2\fP
+.PD
+True if the strings are equal.  \fB=\fP should be used
+with the \fBtest\fP command for POSIX conformance.
+When used with the \fB[[\fP command, this performs pattern matching as
+described above (\fBCompound Commands\fP).
+.TP
+\fIstring1\fP \fB!=\fP \fIstring2\fP
+True if the strings are not equal.
+.TP
+\fIstring1\fP \fB<\fP \fIstring2\fP
+True if \fIstring1\fP sorts before \fIstring2\fP lexicographically.
+.TP
+\fIstring1\fP \fB>\fP \fIstring2\fP
+True if \fIstring1\fP sorts after \fIstring2\fP lexicographically.
+.TP
+.I \fIarg1\fP \fBOP\fP \fIarg2\fP
+.SM
+.B OP
+is one of
+.BR \-eq ,
+.BR \-ne ,
+.BR \-lt ,
+.BR \-le ,
+.BR \-gt ,
+or
+.BR \-ge .
+These arithmetic binary operators return true if \fIarg1\fP
+is equal to, not equal to, less than, less than or equal to,
+greater than, or greater than or equal to \fIarg2\fP, respectively.
+.I Arg1
+and
+.I arg2
+may be positive or negative integers.
+When used with the \fB[[\fP command,
+.I Arg1
+and
+.I Arg2
+are evaluated as arithmetic expressions (see
+.SM
+.B "ARITHMETIC EVALUATION"
+above).
+.PD
+.SH "SIMPLE COMMAND EXPANSION"
+When a simple command is executed, the shell performs the following
+expansions, assignments, and redirections, from left to right, in
+the following order.
+.IP 1.
+The words that the parser has marked as variable assignments (those
+preceding the command name) and redirections are saved for later
+processing.
+.IP 2.
+The words that are not variable assignments or redirections are
+expanded.  If any words remain after expansion, the first word
+is taken to be the name of the command and the remaining words are
+the arguments.
+.IP 3.
+Redirections are performed as described above under
+.SM
+.BR REDIRECTION .
+.IP 4.
+The text after the \fB=\fP in each variable assignment undergoes tilde
+expansion, parameter expansion, command substitution, arithmetic expansion,
+and quote removal before being assigned to the variable.
+.PP
+If no command name results, the variable assignments affect the current
+shell environment.  Otherwise, the variables are added to the environment
+of the executed command and do not affect the current shell environment.
+If any of the assignments attempts to assign a value to a readonly variable,
+an error occurs, and the command exits with a non-zero status.
+.PP
+If no command name results, redirections are performed, but do not
+affect the current shell environment.  A redirection error causes the
+command to exit with a non-zero status.
+.PP
+If there is a command name left after expansion, execution proceeds as
+described below.  Otherwise, the command exits.  If one of the expansions
+contained a command substitution, the exit status of the command is
+the exit status of the last command substitution performed.  If there
+were no command substitutions, the command exits with a status of zero.
+.SH "COMMAND EXECUTION"
+After a command has been split into words, if it results in a
+simple command and an optional list of arguments, the following
+actions are taken.
+.PP
+If the command name contains no slashes, the shell attempts to
+locate it.  If there exists a shell function by that name, that
+function is invoked as described above in
+.SM
+.BR FUNCTIONS .
+If the name does not match a function, the shell searches for
+it in the list of shell builtins.  If a match is found, that
+builtin is invoked.
+.PP
+If the name is neither a shell function nor a builtin,
+and contains no slashes,
+.B bash
+searches each element of the
+.SM
+.B PATH
+for a directory containing an executable file by that name.
+.B Bash
+uses a hash table to remember the full pathnames of executable
+files (see
+.B hash
+under
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).
+A full search of the directories in
+.SM
+.B PATH
+is performed only if the command is not found in the hash table.
+If the search is unsuccessful, the shell searches for a defined shell
+function named \fBcommand_not_found_handle\fP.
+If that function exists, it is invoked in a separate execution environment
+with the original command and
+the original command's arguments as its arguments, and the function's
+exit status becomes the exit status of that subshell.
+If that function is not defined, the shell prints an error
+message and returns an exit status of 127.
+.PP
+If the search is successful, or if the command name contains
+one or more slashes, the shell executes the named program in a
+separate execution environment.
+Argument 0 is set to the name given, and the remaining arguments
+to the command are set to the arguments given, if any.
+.PP
+If this execution fails because the file is not in executable
+format, and the file is not a directory, it is assumed to be
+a \fIshell script\fP, a file
+containing shell commands.  A subshell is spawned to execute
+it.  This subshell reinitializes itself, so
+that the effect is as if a new shell had been invoked
+to handle the script, with the exception that the locations of
+commands remembered by the parent (see
+.B hash
+below under
+.SM
+\fBSHELL BUILTIN COMMANDS\fP)
+are retained by the child.
+.PP
+If the program is a file beginning with
+.BR #! ,
+the remainder of the first line specifies an interpreter
+for the program.  The shell executes the
+specified interpreter on operating systems that do not
+handle this executable format themselves.  The arguments to the
+interpreter consist of a single optional argument following the
+interpreter name on the first line of the program, followed
+by the name of the program, followed by the command
+arguments, if any.
+.SH COMMAND EXECUTION ENVIRONMENT
+The shell has an \fIexecution environment\fP, which consists of the
+following:
+.IP \(bu
+open files inherited by the shell at invocation, as modified by
+redirections supplied to the \fBexec\fP builtin
+.IP \(bu
+the current working directory as set by \fBcd\fP, \fBpushd\fP, or
+\fBpopd\fP, or inherited by the shell at invocation
+.IP \(bu
+the file creation mode mask as set by \fBumask\fP or inherited from
+the shell's parent
+.IP \(bu
+current traps set by \fBtrap\fP
+.IP \(bu
+shell parameters that are set by variable assignment or with \fBset\fP
+or inherited from the shell's parent in the environment
+.IP \(bu
+shell functions defined during execution or inherited from the shell's
+parent in the environment
+.IP \(bu
+options enabled at invocation (either by default or with command-line
+arguments) or by \fBset\fP
+.IP \(bu
+options enabled by \fBshopt\fP
+.IP \(bu
+shell aliases defined with \fBalias\fP
+.IP \(bu
+various process IDs, including those of background jobs, the value
+of \fB$$\fP, and the value of
+.SM
+.B PPID
+.PP
+When a simple command other than a builtin or shell function
+is to be executed, it
+is invoked in a separate execution environment that consists of
+the following.  Unless otherwise noted, the values are inherited
+from the shell.
+.if n .sp 1
+.IP \(bu
+the shell's open files, plus any modifications and additions specified
+by redirections to the command
+.IP \(bu
+the current working directory
+.IP \(bu
+the file creation mode mask
+.IP \(bu
+shell variables and functions marked for export, along with variables
+exported for the command, passed in the environment
+.IP \(bu
+traps caught by the shell are reset to the values inherited from the
+shell's parent, and traps ignored by the shell are ignored
+.PP
+A command invoked in this separate environment cannot affect the
+shell's execution environment.
+.PP
+Command substitution, commands grouped with parentheses,
+and asynchronous commands are invoked in a
+subshell environment that is a duplicate of the shell environment,
+except that traps caught by the shell are reset to the values
+that the shell inherited from its parent at invocation.  Builtin
+commands that are invoked as part of a pipeline are also executed in a
+subshell environment.  Changes made to the subshell environment
+cannot affect the shell's execution environment.
+.PP
+Subshells spawned to execute command substitutions inherit the value of
+the \fB\-e\fP option from the parent shell.  When not in \fIposix mode\fP,
+\fBbash\fP clears the \fB\-e\fP option in such subshells.
+.PP
+If a command is followed by a \fB&\fP and job control is not active, the
+default standard input for the command is the empty file \fI/dev/null\fP.
+Otherwise, the invoked command inherits the file descriptors of the calling
+shell as modified by redirections.
+.SH ENVIRONMENT
+When a program is invoked it is given an array of strings
+called the
+.IR environment .
+This is a list of
+\fIname\fP\-\fIvalue\fP pairs, of the form
+.IR "name\fR=\fPvalue" .
+.PP
+The shell provides several ways to manipulate the environment.
+On invocation, the shell scans its own environment and
+creates a parameter for each name found, automatically marking
+it for
+.I export
+to child processes.  Executed commands inherit the environment.
+The
+.B export
+and
+.B declare \-x
+commands allow parameters and functions to be added to and
+deleted from the environment.  If the value of a parameter
+in the environment is modified, the new value becomes part
+of the environment, replacing the old.  The environment
+inherited by any executed command consists of the shell's
+initial environment, whose values may be modified in the shell,
+less any pairs removed by the
+.B unset
+command, plus any additions via the
+.B export
+and
+.B declare \-x
+commands.
+.PP
+The environment for any
+.I simple command
+or function may be augmented temporarily by prefixing it with
+parameter assignments, as described above in
+.SM
+.BR PARAMETERS .
+These assignment statements affect only the environment seen
+by that command.
+.PP
+If the
+.B \-k
+option is set (see the
+.B set
+builtin command below), then
+.I all
+parameter assignments are placed in the environment for a command,
+not just those that precede the command name.
+.PP
+When
+.B bash
+invokes an external command, the variable
+.B _
+is set to the full filename of the command and passed to that
+command in its environment.
+.SH "EXIT STATUS"
+The exit status of an executed command is the value returned by the
+\fIwaitpid\fP 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.
+.PP
+For the shell's purposes, a command which exits with a
+zero exit status has succeeded.  An exit status of zero
+indicates success.  A non-zero exit status indicates failure.
+When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
+the value of 128+\fIN\fP as the exit status.
+.PP
+If a command is not found, the child process created to
+execute it returns a status of 127.  If a command is found
+but is not executable, the return status is 126.
+.PP
+If a command fails because of an error during expansion or redirection,
+the exit status is greater than zero.
+.PP
+Shell builtin commands return a status of 0 (\fItrue\fP) if
+successful, and non-zero (\fIfalse\fP) if an error occurs
+while they execute.
+All builtins return an exit status of 2 to indicate incorrect usage,
+generally invalid options or missing arguments.
+.PP
+\fBBash\fP itself returns the exit status of the last command
+executed, unless a syntax error occurs, in which case it exits
+with a non-zero value.  See also the \fBexit\fP builtin
+command below.
+.SH SIGNALS
+When \fBbash\fP is interactive, in the absence of any traps, it ignores
+.SM
+.B SIGTERM
+(so that \fBkill 0\fP does not kill an interactive shell),
+and
+.SM
+.B SIGINT
+is caught and handled (so that the \fBwait\fP builtin is interruptible).
+In all cases, \fBbash\fP ignores
+.SM
+.BR SIGQUIT .
+If job control is in effect,
+.B bash
+ignores
+.SM
+.BR SIGTTIN ,
+.SM
+.BR SIGTTOU ,
+and
+.SM
+.BR SIGTSTP .
+.PP
+Non-builtin commands run by \fBbash\fP have signal handlers
+set to the values inherited by the shell from its parent.
+When job control is not in effect, asynchronous commands
+ignore
+.SM
+.B SIGINT
+and
+.SM
+.B SIGQUIT
+in addition to these inherited handlers.
+Commands run as a result of command substitution ignore the
+keyboard-generated job control signals
+.SM
+.BR SIGTTIN ,
+.SM
+.BR SIGTTOU ,
+and
+.SM
+.BR SIGTSTP .
+.PP
+The shell exits by default upon receipt of a
+.SM
+.BR SIGHUP .
+Before exiting, an interactive shell resends the
+.SM
+.B SIGHUP
+to all jobs, running or stopped.
+Stopped jobs are sent
+.SM
+.B SIGCONT
+to ensure that they receive the
+.SM
+.BR SIGHUP .
+To prevent the shell from
+sending the signal to a particular job, it should be removed from the
+jobs table with the
+.B disown
+builtin (see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below) or marked
+to not receive
+.SM
+.B SIGHUP
+using
+.BR "disown \-h" .
+.PP
+If the
+.B huponexit
+shell option has been set with
+.BR shopt ,
+.B bash
+sends a
+.SM
+.B SIGHUP
+to all jobs when an interactive login shell exits.
+.PP
+If \fBbash\fP 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 \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
+builtin, the reception of a signal for which a trap has been set will
+cause the \fBwait\fP builtin to return immediately with an exit status
+greater than 128, immediately after which the trap is executed.
+.SH "JOB CONTROL"
+.I Job control
+refers to the ability to selectively stop (\fIsuspend\fP)
+the execution of processes and continue (\fIresume\fP)
+their execution at a later point.  A user typically employs
+this facility via an interactive interface supplied jointly
+by the operating system kernel's terminal driver and
+.BR bash .
+.PP
+The shell associates a
+.I job
+with each pipeline.  It keeps a table of currently executing
+jobs, which may be listed with the
+.B jobs
+command.  When
+.B bash
+starts a job asynchronously (in the
+.IR background ),
+it prints a line that looks like:
+.RS
+.PP
+[1] 25647
+.RE
+.PP
+indicating that this job is job number 1 and that the process ID
+of the last process in the pipeline associated with this job is 25647.
+All of the processes in a single pipeline are members of the same job.
+.B Bash
+uses the
+.I job
+abstraction as the basis for job control.
+.PP
+To facilitate the implementation of the user interface to job
+control, the operating system maintains the notion of a \fIcurrent terminal
+process group ID\fP.  Members of this process group (processes whose
+process group ID is equal to the current terminal process group ID)
+receive keyboard-generated signals such as
+.SM
+.BR SIGINT .
+These processes are said to be in the
+.IR foreground .
+.I Background
+processes are those whose process group ID differs from the terminal's;
+such processes are immune to keyboard-generated signals.
+Only foreground processes are allowed to read from or, if the
+user so specifies with \f(CWstty tostop\fP, write to the
+terminal.
+Background processes which attempt to read from (write to when
+\f(CWstty tostop\fP is in effect) the
+terminal are sent a
+.SM
+.B SIGTTIN (SIGTTOU)
+signal by the kernel's terminal driver,
+which, unless caught, suspends the process.
+.PP
+If the operating system on which
+.B bash
+is running supports
+job control,
+.B bash
+contains facilities to use it.
+Typing the
+.I suspend
+character (typically
+.BR ^Z ,
+Control-Z) while a process is running
+causes that process to be stopped and returns control to
+.BR bash .
+Typing the
+.I "delayed suspend"
+character (typically
+.BR ^Y ,
+Control-Y) causes the process to be stopped when it
+attempts to read input from the terminal, and control to
+be returned to
+.BR bash .
+The user may then manipulate the state of this job, using the
+.B bg
+command to continue it in the background, the
+.B fg
+command to continue it in the foreground, or
+the
+.B kill
+command to kill it.  A \fB^Z\fP takes effect immediately,
+and has the additional side effect of causing pending output
+and typeahead to be discarded.
+.PP
+There are a number of ways to refer to a job in the shell.
+The character
+.B %
+introduces a job specification (\fIjobspec\fP).  Job number
+.I n
+may be referred to as
+.BR %n .
+A job may also be referred to using a prefix of the name used to
+start it, or using a substring that appears in its command line.
+For example,
+.B %ce
+refers to a stopped
+job whose command name begins with
+.BR ce .
+If a prefix matches more than one job,
+.B bash
+reports an error.  Using
+.BR %?ce ,
+on the other hand, refers to any job containing the string
+.B ce
+in its command line.  If the substring matches more than one job,
+.B bash
+reports an error.  The symbols
+.B %%
+and
+.B %+
+refer to the shell's notion of the
+.IR "current job" ,
+which is the last job stopped while it was in
+the foreground or started in the background.
+The
+.I "previous job"
+may be referenced using
+.BR %\- .
+If there is only a single job, \fB%+\fP and \fB%\-\fP can both be used
+to refer to that job.
+In output pertaining to jobs (e.g., the output of the
+.B jobs
+command), the current job is always flagged with a
+.BR + ,
+and the previous job with a
+.BR \- .
+A single % (with no accompanying job specification) also refers to the
+current job.
+.PP
+Simply naming a job can be used to bring it into the
+foreground:
+.B %1
+is a synonym for
+\fB``fg %1''\fP,
+bringing job 1 from the background into the foreground.
+Similarly,
+.B ``%1 &''
+resumes job 1 in the background, equivalent to
+\fB``bg %1''\fP.
+.PP
+The shell learns immediately whenever a job changes state.
+Normally,
+.B bash
+waits until it is about to print a prompt before reporting
+changes in a job's status so as to not interrupt
+any other output.  If the
+.B \-b
+option to the
+.B set
+builtin command
+is enabled,
+.B bash
+reports such changes immediately.
+Any trap on
+.SM
+.B SIGCHLD
+is executed for each child that exits.
+.PP
+If an attempt to exit
+.B bash
+is made while jobs are stopped (or, if the \fBcheckjobs\fP shell option has
+been enabled using the \fBshopt\fP builtin, running), the shell prints a
+warning message, and, if the \fBcheckjobs\fP option is enabled, lists the
+jobs and their statuses.
+The
+.B jobs
+command may then be used to inspect their status.
+If a second attempt to exit is made without an intervening command,
+the shell does not print another warning, and any stopped
+jobs are terminated.
+.PP
+When the shell is waiting for a job or process using the \fBwait\fP
+builtin, and job control is enabled, \fBwait\fP will return when the
+job changes state. The \fB\-f\fP option causes \fBwait\fP to wait
+until the job or process terminates before returning.
+.SH PROMPTING
+When executing interactively,
+.B bash
+displays the primary prompt
+.SM
+.B PS1
+when it is ready to read a command, and the secondary prompt
+.SM
+.B PS2
+when it needs more input to complete a command.
+.B Bash
+displays
+.SM
+.B PS0
+after it reads a command but before executing it.
+.B Bash
+displays
+.SM
+.B PS4
+as described above
+before tracing each command when the \fB\-x\fP option is enabled.
+.B Bash
+allows these prompt strings to be customized by inserting a number of
+backslash-escaped special characters that are decoded as follows:
+.RS
+.PD 0
+.TP
+.B \ea
+an ASCII bell character (07)
+.TP
+.B \ed
+the date in "Weekday Month Date" format (e.g., "Tue May 26")
+.TP
+.B \eD{\fIformat\fP}
+the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
+into the prompt string; an empty \fIformat\fP results in a locale-specific
+time representation.  The braces are required
+.TP
+.B \ee
+an ASCII escape character (033)
+.TP
+.B \eh
+the hostname up to the first `.'
+.TP
+.B \eH
+the hostname
+.TP
+.B \ej
+the number of jobs currently managed by the shell
+.TP
+.B \el
+the basename of the shell's terminal device name
+.TP
+.B \en
+newline
+.TP
+.B \er
+carriage return
+.TP
+.B \es
+the name of the shell, the basename of
+.B $0
+(the portion following the final slash)
+.TP
+.B \et
+the current time in 24-hour HH:MM:SS format
+.TP
+.B \eT
+the current time in 12-hour HH:MM:SS format
+.TP
+.B \e@
+the current time in 12-hour am/pm format
+.TP
+.B \eA
+the current time in 24-hour HH:MM format
+.TP
+.B \eu
+the username of the current user
+.TP
+.B \ev
+the version of \fBbash\fP (e.g., 2.00)
+.TP
+.B \eV
+the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
+.TP
+.B \ew
+the current working directory, with
+.SM
+.B $HOME
+abbreviated with a tilde
+(uses the value of the
+.SM
+.B PROMPT_DIRTRIM
+variable)
+.TP
+.B \eW
+the basename of the current working directory, with
+.SM
+.B $HOME
+abbreviated with a tilde
+.TP
+.B \e!
+the history number of this command
+.TP
+.B \e#
+the command number of this command
+.TP
+.B \e$
+if the effective UID is 0, a
+.BR # ,
+otherwise a
+.B $
+.TP
+.B \e\fInnn\fP
+the character corresponding to the octal number \fInnn\fP
+.TP
+.B \e\e
+a backslash
+.TP
+.B \e[
+begin a sequence of non-printing characters, which could be used to
+embed a terminal control sequence into the prompt
+.TP
+.B \e]
+end a sequence of non-printing characters
+.PD
+.RE
+.PP
+The command number and the history number are usually different:
+the history number of a command is its position in the history
+list, which may include commands restored from the history file
+(see
+.SM
+.B HISTORY
+below), while the command number is the position in the sequence
+of commands executed during the current shell session.
+After the string is decoded, it is expanded via
+parameter expansion, command substitution, arithmetic
+expansion, and quote removal, subject to the value of the
+.B promptvars
+shell option (see the description of the
+.B shopt
+command under
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below).
+This can have unwanted side effects if escaped portions of the string
+appear within command substitution or contain characters special to
+word expansion.
+.SH READLINE
+This is the library that handles reading input when using an interactive
+shell, unless the
+.B \-\-noediting
+option is given at shell invocation.
+Line editing is also used when using the \fB\-e\fP option to the
+\fBread\fP builtin.
+By default, the line editing commands are similar to those of Emacs.
+A vi-style line editing interface is also available.
+Line editing can be enabled at any time using the
+.B \-o emacs
+or
+.B \-o vi
+options to the
+.B set
+builtin (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+To turn off line editing after the shell is running, use the
+.B +o emacs
+or
+.B +o vi
+options to the
+.B set
+builtin.
+.SS "Readline Notation"
+In this section, the Emacs-style notation is used to denote
+keystrokes.  Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
+means Control\-N.  Similarly,
+.I meta
+keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X.  (On keyboards
+without a
+.I meta
+key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
+then the
+.I x
+key.  This makes ESC the \fImeta prefix\fP.
+The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
+or press the Escape key
+then hold the Control key while pressing the
+.I x
+key.)
+.PP
+Readline commands may be given numeric
+.IR arguments ,
+which normally act as a repeat count.
+Sometimes, however, it is the sign of the argument that is significant.
+Passing a negative argument to a command that acts in the forward
+direction (e.g., \fBkill\-line\fP) causes that command to act in a
+backward direction.
+Commands whose behavior with arguments deviates from this are noted
+below.
+.PP
+When a command is described as \fIkilling\fP text, the text
+deleted is saved for possible future retrieval
+(\fIyanking\fP).  The killed text is saved in a
+\fIkill ring\fP.  Consecutive kills cause the text to be
+accumulated into one unit, which can be yanked all at once.
+Commands which do not kill text separate the chunks of text
+on the kill ring.
+.SS "Readline Initialization"
+Readline is customized by putting commands in an initialization
+file (the \fIinputrc\fP file).
+The name of this file is taken from the value of the
+.SM
+.B INPUTRC
+variable.  If that variable is unset, the default is
+.IR ~/.inputrc .
+If that file  does not exist or cannot be read, the ultimate default is
+.IR /etc/inputrc .
+When a program which uses the readline library starts up, the
+initialization file is read, and the key bindings and variables
+are set.
+There are only a few basic constructs allowed in the
+readline initialization file.
+Blank lines are ignored.
+Lines beginning with a \fB#\fP are comments.
+Lines beginning with a \fB$\fP indicate conditional constructs.
+Other lines denote key bindings and variable settings.
+.PP
+The default key-bindings may be changed with an
+.I inputrc
+file.
+Other programs that use this library may add their own commands
+and bindings.
+.PP
+For example, placing
+.RS
+.PP
+M\-Control\-u: universal\-argument
+.RE
+or
+.RS
+C\-Meta\-u: universal\-argument
+.RE
+into the
+.I inputrc
+would make M\-C\-u execute the readline command
+.IR universal\-argument .
+.PP
+The following symbolic character names are recognized:
+.IR RUBOUT ,
+.IR DEL ,
+.IR ESC ,
+.IR LFD ,
+.IR NEWLINE ,
+.IR RET ,
+.IR RETURN ,
+.IR SPC ,
+.IR SPACE ,
+and
+.IR TAB .
+.PP
+In addition to command names, readline allows keys to be bound
+to a string that is inserted when the key is pressed (a \fImacro\fP).
+.SS "Readline Key Bindings"
+The syntax for controlling key bindings in the
+.I inputrc
+file is simple.  All that is required is the name of the
+command or the text of a macro and a key sequence to which
+it should be bound.  The name may be specified in one of two ways:
+as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
+prefixes, or as a key sequence.
+.PP
+When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
+.I keyname
+is the name of a key spelled out in English.  For example:
+.sp
+.RS
+Control-u: universal\-argument
+.br
+Meta-Rubout: backward-kill-word
+.br
+Control-o: "> output"
+.RE
+.LP
+In the above example,
+.I C\-u
+is bound to the function
+.BR universal\-argument ,
+.I M\-DEL
+is bound to the function
+.BR backward\-kill\-word ,
+and
+.I C\-o
+is bound to run the macro
+expressed on the right hand side (that is, to insert the text
+.if t \f(CW> output\fP
+.if n ``> output''
+into the line).
+.PP
+In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
+.B keyseq
+differs from
+.B keyname
+above in that strings denoting
+an entire key sequence may be specified by placing the sequence
+within double quotes.  Some GNU Emacs style key escapes can be
+used, as in the following example, but the symbolic character names
+are not recognized.
+.sp
+.RS
+"\eC\-u": universal\-argument
+.br
+"\eC\-x\eC\-r": re\-read\-init\-file
+.br
+"\ee[11~": "Function Key 1"
+.RE
+.PP
+In this example,
+.I C\-u
+is again bound to the function
+.BR universal\-argument .
+.I "C\-x C\-r"
+is bound to the function
+.BR re\-read\-init\-file ,
+and
+.I "ESC [ 1 1 ~"
+is bound to insert the text
+.if t \f(CWFunction Key 1\fP.
+.if n ``Function Key 1''.
+.PP
+The full set of GNU Emacs style escape sequences is
+.RS
+.PD 0
+.TP
+.B \eC\-
+control prefix
+.TP
+.B \eM\-
+meta prefix
+.TP
+.B \ee
+an escape character
+.TP
+.B \e\e
+backslash
+.TP
+.B \e"
+literal "
+.TP
+.B \e\(aq
+literal \(aq
+.RE
+.PD
+.PP
+In addition to the GNU Emacs style escape sequences, a second
+set of backslash escapes is available:
+.RS
+.PD 0
+.TP
+.B \ea
+alert (bell)
+.TP
+.B \eb
+backspace
+.TP
+.B \ed
+delete
+.TP
+.B \ef
+form feed
+.TP
+.B \en
+newline
+.TP
+.B \er
+carriage return
+.TP
+.B \et
+horizontal tab
+.TP
+.B \ev
+vertical tab
+.TP
+.B \e\fInnn\fP
+the eight-bit character whose value is the octal value \fInnn\fP
+(one to three digits)
+.TP
+.B \ex\fIHH\fP
+the eight-bit character whose value is the hexadecimal value \fIHH\fP
+(one or two hex digits)
+.RE
+.PD
+.PP
+When entering the text of a macro, single or double quotes must
+be used to indicate a macro definition.
+Unquoted text is assumed to be a function name.
+In the macro body, the backslash escapes described above are expanded.
+Backslash will quote any other character in the macro text,
+including " and \(aq.
+.PP
+.B Bash
+allows the current readline key bindings to be displayed or modified
+with the
+.B bind
+builtin command.  The editing mode may be switched during interactive
+use by using the
+.B \-o
+option to the
+.B set
+builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.SS "Readline Variables"
+Readline has variables that can be used to further customize its
+behavior.  A variable may be set in the
+.I inputrc
+file with a statement of the form
+.RS
+.PP
+\fBset\fP \fIvariable\-name\fP \fIvalue\fP
+.RE
+or using the \fBbind\fP builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).
+.PP
+Except where noted, readline variables can take the values
+.B On
+or
+.B Off
+(without regard to case).
+Unrecognized variable names are ignored.
+When a variable value is read, empty or null values, "on" (case-insensitive),
+and "1" are equivalent to \fBOn\fP.  All other values are equivalent to
+\fBOff\fP.
+The variables and their default values are:
+.PP
+.PD 0
+.TP
+.B bell\-style (audible)
+Controls what happens when readline wants to ring the terminal bell.
+If set to \fBnone\fP, readline never rings the bell.  If set to
+\fBvisible\fP, readline uses a visible bell if one is available.
+If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
+.TP
+.B bind\-tty\-special\-chars (On)
+If set to \fBOn\fP, readline attempts to bind the control characters
+treated specially by the kernel's terminal driver to their readline
+equivalents.
+.TP
+.B blink\-matching\-paren (Off)
+If set to \fBOn\fP, readline attempts to briefly move the cursor to an
+opening parenthesis when a closing parenthesis is inserted.
+.TP
+.B colored\-completion\-prefix (Off)
+If set to \fBOn\fP, when listing completions, readline displays the
+common prefix of the set of possible completions using a different color.
+The color definitions are taken from the value of the \fBLS_COLORS\fP
+environment variable.
+.TP
+.B colored\-stats (Off)
+If set to \fBOn\fP, readline displays possible completions using different
+colors to indicate their file type.
+The color definitions are taken from the value of the \fBLS_COLORS\fP
+environment variable.
+.TP
+.B comment\-begin (``#'')
+The string that is inserted when the readline
+.B insert\-comment
+command is executed.
+This command is bound to
+.B M\-#
+in emacs mode and to
+.B #
+in vi command mode.
+.TP
+.B completion\-display\-width (\-1)
+The number of screen columns used to display possible matches
+when performing completion.
+The value is ignored if it is less than 0 or greater than the terminal
+screen width.
+A value of 0 will cause matches to be displayed one per line.
+The default value is \-1.
+.TP
+.B completion\-ignore\-case (Off)
+If set to \fBOn\fP, readline performs filename matching and completion
+in a case\-insensitive fashion.
+.TP
+.B completion\-map\-case (Off)
+If set to \fBOn\fP, and \fBcompletion\-ignore\-case\fP is enabled, readline
+treats hyphens (\fI\-\fP) and underscores (\fI_\fP) as equivalent when
+performing case\-insensitive filename matching and completion.
+.TP
+.B completion\-prefix\-display\-length (0)
+The length in characters of the common prefix of a list of possible
+completions that is displayed without modification.  When set to a
+value greater than zero, common prefixes longer than this value are
+replaced with an ellipsis when displaying possible completions.
+.TP
+.B completion\-query\-items (100)
+This determines when the user is queried about viewing
+the number of possible completions
+generated by the \fBpossible\-completions\fP command.
+It may be set to any integer value greater than or equal to zero.
+If the number of possible completions is greater than
+or equal to the value of this variable,
+readline will ask whether or not the user wishes to view them;
+otherwise they are simply listed on the terminal.
+.TP
+.B convert\-meta (On)
+If set to \fBOn\fP, readline will convert characters with the
+eighth bit set to an ASCII key sequence
+by stripping the eighth bit and prefixing an
+escape character (in effect, using escape as the \fImeta prefix\fP).
+The default is \fIOn\fP, but readline will set it to \fIOff\fP if the
+locale contains eight-bit characters.
+.TP
+.B disable\-completion (Off)
+If set to \fBOn\fP, readline will inhibit word completion.  Completion
+characters will be inserted into the line as if they had been
+mapped to \fBself-insert\fP.
+.TP
+.B echo\-control\-characters (On)
+When set to \fBOn\fP, on operating systems that indicate they support it,
+readline echoes a character corresponding to a signal generated from the
+keyboard.
+.TP
+.B editing\-mode (emacs)
+Controls whether readline begins with a set of key bindings similar
+to \fIEmacs\fP or \fIvi\fP.
+.B editing\-mode
+can be set to either
+.B emacs
+or
+.BR vi .
+.TP
+.B emacs\-mode\-string (@)
+If the \fIshow\-mode\-in\-prompt\fP variable is enabled,
+this string is displayed immediately before the last line of the primary
+prompt when emacs editing mode is active.  The value is expanded like a
+key binding, so the standard set of meta- and control prefixes and
+backslash escape sequences is available.
+Use the \e1 and \e2 escapes to begin and end sequences of
+non-printing characters, which can be used to embed a terminal control
+sequence into the mode string.
+.TP
+.B enable\-bracketed\-paste (On)
+When set to \fBOn\fP, readline will configure the terminal in a way
+that will enable it to insert each paste into the editing buffer as a
+single string of characters, instead of treating each character as if
+it had been read from the keyboard.  This can prevent pasted characters
+from being interpreted as editing commands.
+.TP
+.B enable\-keypad (Off)
+When set to \fBOn\fP, readline will try to enable the application
+keypad when it is called.  Some systems need this to enable the
+arrow keys.
+.TP
+.B enable\-meta\-key (On)
+When set to \fBOn\fP, readline will try to enable any meta modifier
+key the terminal claims to support when it is called.  On many terminals,
+the meta key is used to send eight-bit characters.
+.TP
+.B expand\-tilde (Off)
+If set to \fBOn\fP, tilde expansion is performed when readline
+attempts word completion.
+.TP
+.B history\-preserve\-point (Off)
+If set to \fBOn\fP, the history code attempts to place point at the
+same location on each history line retrieved with \fBprevious-history\fP
+or \fBnext-history\fP.
+.TP
+.B history\-size (unset)
+Set the maximum number of history entries saved in the history list.
+If set to zero, any existing history entries are deleted and no new entries
+are saved.
+If set to a value less than zero, the number of history entries is not
+limited.
+By default, the number of history entries is set to the value of the
+\fBHISTSIZE\fP shell variable.
+If an attempt is made to set \fIhistory\-size\fP to a non-numeric value,
+the maximum number of history entries will be set to 500.
+.TP
+.B horizontal\-scroll\-mode (Off)
+When set to \fBOn\fP, makes readline use a single line for display,
+scrolling the input horizontally on a single screen line when it
+becomes longer than the screen width rather than wrapping to a new line.
+This setting is automatically enabled for terminals of height 1.
+.TP
+.B input\-meta (Off)
+If set to \fBOn\fP, readline will enable eight-bit input (that is,
+it will not strip the eighth bit from the characters it reads),
+regardless of what the terminal claims it can support.  The name
+.B meta\-flag
+is a synonym for this variable.
+The default is \fIOff\fP, but readline will set it to \fIOn\fP if the
+locale contains eight-bit characters.
+.TP
+.B isearch\-terminators (``C\-[C\-J'')
+The string of characters that should terminate an incremental
+search without subsequently executing the character as a command.
+If this variable has not been given a value, the characters
+\fIESC\fP and \fIC\-J\fP will terminate an incremental search.
+.TP
+.B keymap (emacs)
+Set the current readline keymap.  The set of valid keymap names is
+\fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
+vi\-command\fP, and
+.IR vi\-insert .
+\fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
+equivalent to \fIemacs\-standard\fP.  The default value is
+.IR emacs ;
+the value of
+.B editing\-mode
+also affects the default keymap.
+.TP
+.B keyseq\-timeout (500)
+Specifies the duration \fIreadline\fP will wait for a character when reading an
+ambiguous key sequence (one that can form a complete key sequence using
+the input read so far, or can take additional input to complete a longer
+key sequence).
+If no input is received within the timeout, \fIreadline\fP will use the shorter
+but complete key sequence.
+The value is specified in milliseconds, so a value of 1000 means that
+\fIreadline\fP will wait one second for additional input.
+If this variable is set to a value less than or equal to zero, or to a
+non-numeric value, \fIreadline\fP will wait until another key is pressed to
+decide which key sequence to complete.
+.TP
+.B mark\-directories (On)
+If set to \fBOn\fP, completed directory names have a slash
+appended.
+.TP
+.B mark\-modified\-lines (Off)
+If set to \fBOn\fP, history lines that have been modified are displayed
+with a preceding asterisk (\fB*\fP).
+.TP
+.B mark\-symlinked\-directories (Off)
+If set to \fBOn\fP, completed names which are symbolic links to directories
+have a slash appended (subject to the value of
+\fBmark\-directories\fP).
+.TP
+.B match\-hidden\-files (On)
+This variable, when set to \fBOn\fP, causes readline to match files whose
+names begin with a `.' (hidden files) when performing filename
+completion.
+If set to \fBOff\fP, the leading `.' must be
+supplied by the user in the filename to be completed.
+.TP
+.B menu\-complete\-display\-prefix (Off)
+If set to \fBOn\fP, menu completion displays the common prefix of the
+list of possible completions (which may be empty) before cycling through
+the list.
+.TP
+.B output\-meta (Off)
+If set to \fBOn\fP, readline will display characters with the
+eighth bit set directly rather than as a meta-prefixed escape
+sequence.
+The default is \fIOff\fP, but readline will set it to \fIOn\fP if the
+locale contains eight-bit characters.
+.TP
+.B page\-completions (On)
+If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
+to display a screenful of possible completions at a time.
+.TP
+.B print\-completions\-horizontally (Off)
+If set to \fBOn\fP, readline will display completions with matches
+sorted horizontally in alphabetical order, rather than down the screen.
+.TP
+.B revert\-all\-at\-newline (Off)
+If set to \fBOn\fP, readline will undo all changes to history lines
+before returning when \fBaccept\-line\fP is executed.  By default,
+history lines may be modified and retain individual undo lists across
+calls to \fBreadline\fP.
+.TP
+.B show\-all\-if\-ambiguous (Off)
+This alters the default behavior of the completion functions.  If
+set to
+.BR On ,
+words which have more than one possible completion cause the
+matches to be listed immediately instead of ringing the bell.
+.TP
+.B show\-all\-if\-unmodified (Off)
+This alters the default behavior of the completion functions in
+a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
+If set to
+.BR On ,
+words which have more than one possible completion without any
+possible partial completion (the possible completions don't share
+a common prefix) cause the matches to be listed immediately instead
+of ringing the bell.
+.TP
+.B show\-mode\-in\-prompt (Off)
+If set to \fBOn\fP, add a string to the beginning of the prompt
+indicating the editing mode: emacs, vi command, or vi insertion.
+The mode strings are user-settable (e.g., \fIemacs\-mode\-string\fP).
+.TP
+.B skip\-completed\-text (Off)
+If set to \fBOn\fP, this alters the default completion behavior when
+inserting a single match into the line.  It's only active when
+performing completion in the middle of a word.  If enabled, readline
+does not insert characters from the completion that match characters
+after point in the word being completed, so portions of the word
+following the cursor are not duplicated.
+.TP
+.B vi\-cmd\-mode\-string ((cmd))
+If the \fIshow\-mode\-in\-prompt\fP variable is enabled,
+this string is displayed immediately before the last line of the primary
+prompt when vi editing mode is active and in command mode.
+The value is expanded like a
+key binding, so the standard set of meta- and control prefixes and
+backslash escape sequences is available.
+Use the \e1 and \e2 escapes to begin and end sequences of
+non-printing characters, which can be used to embed a terminal control
+sequence into the mode string.
+.TP
+.B vi\-ins\-mode\-string ((ins))
+If the \fIshow\-mode\-in\-prompt\fP variable is enabled,
+this string is displayed immediately before the last line of the primary
+prompt when vi editing mode is active and in insertion mode.
+The value is expanded like a
+key binding, so the standard set of meta- and control prefixes and
+backslash escape sequences is available.
+Use the \e1 and \e2 escapes to begin and end sequences of
+non-printing characters, which can be used to embed a terminal control
+sequence into the mode string.
+.TP
+.B visible\-stats (Off)
+If set to \fBOn\fP, a character denoting a file's type as reported
+by \fIstat\fP(2) is appended to the filename when listing possible
+completions.
+.PD
+.SS "Readline Conditional Constructs"
+Readline implements a facility similar in spirit to the conditional
+compilation features of the C preprocessor which allows key
+bindings and variable settings to be performed as the result
+of tests.  There are four parser directives used.
+.IP \fB$if\fP
+The
+.B $if
+construct allows bindings to be made based on the
+editing mode, the terminal being used, or the application using
+readline.  The text of the test, after any comparison operator,
+ extends to the end of the line;
+unless otherwise noted, no characters are required to isolate it.
+.RS
+.IP \fBmode\fP
+The \fBmode=\fP form of the \fB$if\fP directive is used to test
+whether readline is in emacs or vi mode.
+This may be used in conjunction
+with the \fBset keymap\fP command, for instance, to set bindings in
+the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
+readline is starting out in emacs mode.
+.IP \fBterm\fP
+The \fBterm=\fP form may be used to include terminal-specific
+key bindings, perhaps to bind the key sequences output by the
+terminal's function keys.  The word on the right side of the
+.B =
+is tested against both the full name of the terminal and the portion
+of the terminal name before the first \fB\-\fP.  This allows
+.I sun
+to match both
+.I sun
+and
+.IR sun\-cmd ,
+for instance.
+.IP \fBversion\fP
+The \fBversion\fP test may be used to perform comparisons against
+specific readline versions.
+The \fBversion\fP expands to the current readline version.
+The set of comparison operators includes
+.BR = ,
+(and
+.BR == ),
+.BR != ,
+.BR <= ,
+.BR >= ,
+.BR < ,
+and
+.BR > .
+The version number supplied on the right side of the operator consists
+of a major version number, an optional decimal point, and an optional
+minor version (e.g., \fB7.1\fP). If the minor version is omitted, it
+is assumed to be \fB0\fP.
+The operator may be separated from the string \fBversion\fP
+and from the version number argument by whitespace.
+.IP \fBapplication\fP
+The \fBapplication\fP construct is used to include
+application-specific settings.  Each program using the readline
+library sets the \fIapplication name\fP, and an initialization
+file can test for a particular value.
+This could be used to bind key sequences to functions useful for
+a specific program.  For instance, the following command adds a
+key sequence that quotes the current or previous word in \fBbash\fP:
+.sp 1
+.RS
+.nf
+\fB$if\fP Bash
+# Quote the current or previous word
+"\eC\-xq": "\eeb\e"\eef\e""
+\fB$endif\fP
+.fi
+.RE
+.IP \fIvariable\fP
+The \fIvariable\fP construct provides simple equality tests for readline
+variables and values.
+The permitted comparison operators are \fI=\fP, \fI==\fP, and \fI!=\fP.
+The variable name must be separated from the comparison operator by
+whitespace; the operator may be separated from the value on the right hand
+side by whitespace.
+Both string and boolean variables may be tested. Boolean variables must be
+tested against the values \fIon\fP and \fIoff\fP.
+.RE
+.IP \fB$endif\fP
+This command, as seen in the previous example, terminates an
+\fB$if\fP command.
+.IP \fB$else\fP
+Commands in this branch of the \fB$if\fP directive are executed if
+the test fails.
+.IP \fB$include\fP
+This directive takes a single filename as an argument and reads commands
+and bindings from that file.  For example, the following directive
+would read \fI/etc/inputrc\fP:
+.sp 1
+.RS
+.nf
+\fB$include\fP \^ \fI/etc/inputrc\fP
+.fi
+.RE
+.SS Searching
+Readline provides commands for searching through the command history
+(see
+.SM
+.B HISTORY
+below) for lines containing a specified string.
+There are two search modes:
+.I incremental
+and
+.IR non-incremental .
+.PP
+Incremental searches begin before the user has finished typing the
+search string.
+As each character of the search string is typed, readline displays
+the next entry from the history matching the string typed so far.
+An incremental search requires only as many characters as needed to
+find the desired history entry.
+The characters present in the value of the \fBisearch-terminators\fP
+variable are used to terminate an incremental search.
+If that variable has not been assigned a value the Escape and
+Control-J characters will terminate an incremental search.
+Control-G will abort an incremental search and restore the original
+line.
+When the search is terminated, the history entry containing the
+search string becomes the current line.
+.PP
+To find other matching entries in the history list, type Control-S or
+Control-R as appropriate.
+This will search backward or forward in the history for the next
+entry matching the search string typed so far.
+Any other key sequence bound to a readline command will terminate
+the search and execute that command.
+For instance, a \fInewline\fP will terminate the search and accept
+the line, thereby executing the command from the history list.
+.PP
+Readline remembers the last incremental search string.  If two
+Control-Rs are typed without any intervening characters defining a
+new search string, any remembered search string is used.
+.PP
+Non-incremental searches read the entire search string before starting
+to search for matching history lines.  The search string may be
+typed by the user or be part of the contents of the current line.
+.SS "Readline Command Names"
+The following is a list of the names of the commands and the default
+key sequences to which they are bound.
+Command names without an accompanying key sequence are unbound by default.
+In the following descriptions, \fIpoint\fP refers to the current cursor
+position, and \fImark\fP refers to a cursor position saved by the
+\fBset\-mark\fP command.
+The text between the point and mark is referred to as the \fIregion\fP.
+.SS Commands for Moving
+.PD 0
+.TP
+.B beginning\-of\-line (C\-a)
+Move to the start of the current line.
+.TP
+.B end\-of\-line (C\-e)
+Move to the end of the line.
+.TP
+.B forward\-char (C\-f)
+Move forward a character.
+.TP
+.B backward\-char (C\-b)
+Move back a character.
+.TP
+.B forward\-word (M\-f)
+Move forward to the end of the next word.  Words are composed of
+alphanumeric characters (letters and digits).
+.TP
+.B backward\-word (M\-b)
+Move back to the start of the current or previous word.
+Words are composed of alphanumeric characters (letters and digits).
+.TP
+.B shell\-forward\-word
+Move forward to the end of the next word.
+Words are delimited by non-quoted shell metacharacters.
+.TP
+.B shell\-backward\-word
+Move back to the start of the current or previous word.
+Words are delimited by non-quoted shell metacharacters.
+.TP
+.B previous\-screen\-line
+Attempt to move point to the same physical screen column on the previous
+physical screen line. This will not have the desired effect if the current
+Readline line does not take up more than one physical line or if point is not
+greater than the length of the prompt plus the screen width.
+.TP
+.B next\-screen\-line
+Attempt to move point to the same physical screen column on the next
+physical screen line. This will not have the desired effect if the current
+Readline line does not take up more than one physical line or if the length
+of the current Readline line is not greater than the length of the prompt
+plus the screen width.
+.TP
+.B clear\-display (M\-C\-l)
+Clear the screen and, if possible, the terminal's scrollback buffer,
+then redraw the current line,
+leaving the current line at the top of the screen.
+.TP
+.B clear\-screen (C\-l)
+Clear the screen,
+then redraw the current line,
+leaving the current line at the top of the screen.
+With an argument, refresh the current line without clearing the
+screen.
+.TP
+.B redraw\-current\-line
+Refresh the current line.
+.PD
+.SS Commands for Manipulating the History
+.PD 0
+.TP
+.B accept\-line (Newline, Return)
+Accept the line regardless of where the cursor is.  If this line is
+non-empty, add it to the history list according to the state of the
+.SM
+.B HISTCONTROL
+variable.  If the line is a modified history
+line, then restore the history line to its original state.
+.TP
+.B previous\-history (C\-p)
+Fetch the previous command from the history list, moving back in
+the list.
+.TP
+.B next\-history (C\-n)
+Fetch the next command from the history list, moving forward in the
+list.
+.TP
+.B beginning\-of\-history (M\-<)
+Move to the first line in the history.
+.TP
+.B end\-of\-history (M\->)
+Move to the end of the input history, i.e., the line currently being
+entered.
+.TP
+.B reverse\-search\-history (C\-r)
+Search backward starting at the current line and moving `up' through
+the history as necessary.  This is an incremental search.
+.TP
+.B forward\-search\-history (C\-s)
+Search forward starting at the current line and moving `down' through
+the history as necessary.  This is an incremental search.
+.TP
+.B non\-incremental\-reverse\-search\-history (M\-p)
+Search backward through the history starting at the current line
+using a non-incremental search for a string supplied by the user.
+.TP
+.B non\-incremental\-forward\-search\-history (M\-n)
+Search forward through the history using a non-incremental search for
+a string supplied by the user.
+.TP
+.B history\-search\-forward
+Search forward through the history for the string of characters
+between the start of the current line and the point.
+This is a non-incremental search.
+.TP
+.B history\-search\-backward
+Search backward through the history for the string of characters
+between the start of the current line and the point.
+This is a non-incremental search.
+.TP
+.B history\-substring\-search\-backward
+Search backward through the history for the string of characters
+between the start of the current line and the current cursor
+position (the \fIpoint\fP).
+The search string may match anywhere in a history line.
+This is a non-incremental search.
+.TP
+.B history\-substring\-search\-forward
+Search forward through the history for the string of characters
+between the start of the current line and the point.
+The search string may match anywhere in a history line.
+This is a non-incremental search.
+.TP
+.B yank\-nth\-arg (M\-C\-y)
+Insert the first argument to the previous command (usually
+the second word on the previous line) at point.
+With an argument
+.IR n ,
+insert the \fIn\fPth word from the previous command (the words
+in the previous command begin with word 0).  A negative argument
+inserts the \fIn\fPth word from the end of the previous command.
+Once the argument \fIn\fP is computed, the argument is extracted
+as if the "!\fIn\fP" history expansion had been specified.
+.TP
+.B
+yank\-last\-arg (M\-.\^, M\-_\^)
+Insert the last argument to the previous command (the last word of
+the previous history entry).
+With a numeric argument, behave exactly like \fByank\-nth\-arg\fP.
+Successive calls to \fByank\-last\-arg\fP move back through the history
+list, inserting the last word (or the word specified by the argument to
+the first call) of each line in turn.
+Any numeric argument supplied to these successive calls determines
+the direction to move through the history.  A negative argument switches
+the direction through the history (back or forward).
+The history expansion facilities are used to extract the last word,
+as if the "!$" history expansion had been specified.
+.TP
+.B shell\-expand\-line (M\-C\-e)
+Expand the line as the shell does.  This
+performs alias and history expansion as well as all of the shell
+word expansions.  See
+.SM
+.B HISTORY EXPANSION
+below for a description of history expansion.
+.TP
+.B history\-expand\-line (M\-^)
+Perform history expansion on the current line.
+See
+.SM
+.B HISTORY EXPANSION
+below for a description of history expansion.
+.TP
+.B magic\-space
+Perform history expansion on the current line and insert a space.
+See
+.SM
+.B HISTORY EXPANSION
+below for a description of history expansion.
+.TP
+.B alias\-expand\-line
+Perform alias expansion on the current line.
+See
+.SM
+.B ALIASES
+above for a description of alias expansion.
+.TP
+.B history\-and\-alias\-expand\-line
+Perform history and alias expansion on the current line.
+.TP
+.B insert\-last\-argument (M\-.\^, M\-_\^)
+A synonym for \fByank\-last\-arg\fP.
+.TP
+.B operate\-and\-get\-next (C\-o)
+Accept the current line for execution and fetch the next line
+relative to the current line from the history for editing.
+A numeric argument, if supplied, specifies the history entry to use instead
+of the current line.
+.TP
+.B edit\-and\-execute\-command (C\-x C\-e)
+Invoke an editor on the current command line, and execute the result as shell
+commands.
+\fBBash\fP attempts to invoke
+.SM
+.BR $VISUAL ,
+.SM
+.BR $EDITOR ,
+and \fIemacs\fP as the editor, in that order.
+.PD
+.SS Commands for Changing Text
+.PD 0
+.TP
+.B \fIend\-of\-file\fP (usually C\-d)
+The character indicating end-of-file as set, for example, by
+.if t \f(CWstty\fP.
+.if n ``stty''.
+If this character is read when there are no characters
+on the line, and point is at the beginning of the line, Readline
+interprets it as the end of input and returns
+.SM
+.BR EOF .
+.TP
+.B delete\-char (C\-d)
+Delete the character at point.
+If this function is bound to the
+same character as the tty \fBEOF\fP character, as \fBC\-d\fP
+commonly is, see above for the effects.
+.TP
+.B backward\-delete\-char (Rubout)
+Delete the character behind the cursor.  When given a numeric argument,
+save the deleted text on the kill ring.
+.TP
+.B forward\-backward\-delete\-char
+Delete the character under the cursor, unless the cursor is at the
+end of the line, in which case the character behind the cursor is
+deleted.
+.TP
+.B quoted\-insert (C\-q, C\-v)
+Add the next character typed to the line verbatim.  This is
+how to insert characters like \fBC\-q\fP, for example.
+.TP
+.B tab\-insert (C\-v TAB)
+Insert a tab character.
+.TP
+.B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
+Insert the character typed.
+.TP
+.B transpose\-chars (C\-t)
+Drag the character before point forward over the character at point,
+moving point forward as well.
+If point is at the end of the line, then this transposes
+the two characters before point.
+Negative arguments have no effect.
+.TP
+.B transpose\-words (M\-t)
+Drag the word before point past the word after point,
+moving point over that word as well.
+If point is at the end of the line, this transposes
+the last two words on the line.
+.TP
+.B upcase\-word (M\-u)
+Uppercase the current (or following) word.  With a negative argument,
+uppercase the previous word, but do not move point.
+.TP
+.B downcase\-word (M\-l)
+Lowercase the current (or following) word.  With a negative argument,
+lowercase the previous word, but do not move point.
+.TP
+.B capitalize\-word (M\-c)
+Capitalize the current (or following) word.  With a negative argument,
+capitalize the previous word, but do not move point.
+.TP
+.B overwrite\-mode
+Toggle overwrite mode.  With an explicit positive numeric argument,
+switches to overwrite mode.  With an explicit non-positive numeric
+argument, switches to insert mode.  This command affects only
+\fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
+Each call to \fIreadline()\fP starts in insert mode.
+In overwrite mode, characters bound to \fBself\-insert\fP replace
+the text at point rather than pushing the text to the right.
+Characters bound to \fBbackward\-delete\-char\fP replace the character
+before point with a space.  By default, this command is unbound.
+.PD
+.SS Killing and Yanking
+.PD 0
+.TP
+.B kill\-line (C\-k)
+Kill the text from point to the end of the line.
+.TP
+.B backward\-kill\-line (C\-x Rubout)
+Kill backward to the beginning of the line.
+.TP
+.B unix\-line\-discard (C\-u)
+Kill backward from point to the beginning of the line.
+The killed text is saved on the kill-ring.
+.\" There is no real difference between this and backward-kill-line
+.TP
+.B kill\-whole\-line
+Kill all characters on the current line, no matter where point is.
+.TP
+.B kill\-word (M\-d)
+Kill from point to the end of the current word, or if between
+words, to the end of the next word.
+Word boundaries are the same as those used by \fBforward\-word\fP.
+.TP
+.B backward\-kill\-word (M\-Rubout)
+Kill the word behind point.
+Word boundaries are the same as those used by \fBbackward\-word\fP.
+.TP
+.B shell\-kill\-word
+Kill from point to the end of the current word, or if between
+words, to the end of the next word.
+Word boundaries are the same as those used by \fBshell\-forward\-word\fP.
+.TP
+.B shell\-backward\-kill\-word
+Kill the word behind point.
+Word boundaries are the same as those used by \fBshell\-backward\-word\fP.
+.TP
+.B unix\-word\-rubout (C\-w)
+Kill the word behind point, using white space as a word boundary.
+The killed text is saved on the kill-ring.
+.TP
+.B unix\-filename\-rubout
+Kill the word behind point, using white space and the slash character
+as the word boundaries.
+The killed text is saved on the kill-ring.
+.TP
+.B delete\-horizontal\-space (M\-\e)
+Delete all spaces and tabs around point.
+.TP
+.B kill\-region
+Kill the text in the current region.
+.TP
+.B copy\-region\-as\-kill
+Copy the text in the region to the kill buffer.
+.TP
+.B copy\-backward\-word
+Copy the word before point to the kill buffer.
+The word boundaries are the same as \fBbackward\-word\fP.
+.TP
+.B copy\-forward\-word
+Copy the word following point to the kill buffer.
+The word boundaries are the same as \fBforward\-word\fP.
+.TP
+.B yank (C\-y)
+Yank the top of the kill ring into the buffer at point.
+.TP
+.B yank\-pop (M\-y)
+Rotate the kill ring, and yank the new top.  Only works following
+.B yank
+or
+.BR yank\-pop .
+.PD
+.SS Numeric Arguments
+.PD 0
+.TP
+.B digit\-argument (M\-0, M\-1, ..., M\-\-)
+Add this digit to the argument already accumulating, or start a new
+argument.  M\-\- starts a negative argument.
+.TP
+.B universal\-argument
+This is another way to specify an argument.
+If this command is followed by one or more digits, optionally with a
+leading minus sign, those digits define the argument.
+If the command is followed by digits, executing
+.B universal\-argument
+again ends the numeric argument, but is otherwise ignored.
+As a special case, if this command is immediately followed by a
+character that is neither a digit nor minus sign, the argument count
+for the next command is multiplied by four.
+The argument count is initially one, so executing this function the
+first time makes the argument count four, a second time makes the
+argument count sixteen, and so on.
+.PD
+.SS Completing
+.PD 0
+.TP
+.B complete (TAB)
+Attempt to perform completion on the text before point.
+.B Bash
+attempts completion treating the text as a variable (if the
+text begins with \fB$\fP), username (if the text begins with
+\fB~\fP), hostname (if the text begins with \fB@\fP), or
+command (including aliases and functions) in turn.  If none
+of these produces a match, filename completion is attempted.
+.TP
+.B possible\-completions (M\-?)
+List the possible completions of the text before point.
+.TP
+.B insert\-completions (M\-*)
+Insert all completions of the text before point
+that would have been generated by
+\fBpossible\-completions\fP.
+.TP
+.B menu\-complete
+Similar to \fBcomplete\fP, but replaces the word to be completed
+with a single match from the list of possible completions.
+Repeated execution of \fBmenu\-complete\fP steps through the list
+of possible completions, inserting each match in turn.
+At the end of the list of completions, the bell is rung
+(subject to the setting of \fBbell\-style\fP)
+and the original text is restored.
+An argument of \fIn\fP moves \fIn\fP positions forward in the list
+of matches; a negative argument may be used to move backward
+through the list.
+This command is intended to be bound to \fBTAB\fP, but is unbound
+by default.
+.TP
+.B menu\-complete\-backward
+Identical to \fBmenu\-complete\fP, but moves backward through the list
+of possible completions, as if \fBmenu\-complete\fP had been given a
+negative argument.  This command is unbound by default.
+.TP
+.B delete\-char\-or\-list
+Deletes the character under the cursor if not at the beginning or
+end of the line (like \fBdelete\-char\fP).
+If at the end of the line, behaves identically to
+\fBpossible\-completions\fP.
+This command is unbound by default.
+.TP
+.B complete\-filename (M\-/)
+Attempt filename completion on the text before point.
+.TP
+.B possible\-filename\-completions (C\-x /)
+List the possible completions of the text before point,
+treating it as a filename.
+.TP
+.B complete\-username (M\-~)
+Attempt completion on the text before point, treating
+it as a username.
+.TP
+.B possible\-username\-completions (C\-x ~)
+List the possible completions of the text before point,
+treating it as a username.
+.TP
+.B complete\-variable (M\-$)
+Attempt completion on the text before point, treating
+it as a shell variable.
+.TP
+.B possible\-variable\-completions (C\-x $)
+List the possible completions of the text before point,
+treating it as a shell variable.
+.TP
+.B complete\-hostname (M\-@)
+Attempt completion on the text before point, treating
+it as a hostname.
+.TP
+.B possible\-hostname\-completions (C\-x @)
+List the possible completions of the text before point,
+treating it as a hostname.
+.TP
+.B complete\-command (M\-!)
+Attempt completion on the text before point, treating
+it as a command name.  Command completion attempts to
+match the text against aliases, reserved words, shell
+functions, shell builtins, and finally executable filenames,
+in that order.
+.TP
+.B possible\-command\-completions (C\-x !)
+List the possible completions of the text before point,
+treating it as a command name.
+.TP
+.B dynamic\-complete\-history (M\-TAB)
+Attempt completion on the text before point, comparing
+the text against lines from the history list for possible
+completion matches.
+.TP
+.B dabbrev\-expand
+Attempt menu completion on the text before point, comparing
+the text against lines from the history list for possible
+completion matches.
+.TP
+.B complete\-into\-braces (M\-{)
+Perform filename completion and insert the list of possible completions
+enclosed within braces so the list is available to the shell (see
+.B Brace Expansion
+above).
+.PD
+.SS Keyboard Macros
+.PD 0
+.TP
+.B start\-kbd\-macro (C\-x (\^)
+Begin saving the characters typed into the current keyboard macro.
+.TP
+.B end\-kbd\-macro (C\-x )\^)
+Stop saving the characters typed into the current keyboard macro
+and store the definition.
+.TP
+.B call\-last\-kbd\-macro (C\-x e)
+Re-execute the last keyboard macro defined, by making the characters
+in the macro appear as if typed at the keyboard.
+.TP
+.B print\-last\-kbd\-macro ()
+Print the last keyboard macro defined in a format suitable for the
+\fIinputrc\fP file.
+.PD
+.SS Miscellaneous
+.PD 0
+.TP
+.B re\-read\-init\-file (C\-x C\-r)
+Read in the contents of the \fIinputrc\fP file, and incorporate
+any bindings or variable assignments found there.
+.TP
+.B abort (C\-g)
+Abort the current editing command and
+ring the terminal's bell (subject to the setting of
+.BR bell\-style ).
+.TP
+.B do\-lowercase\-version (M\-A, M\-B, M\-\fIx\fP, ...)
+If the metafied character \fIx\fP is uppercase, run the command
+that is bound to the corresponding metafied lowercase character.
+The behavior is undefined if \fIx\fP is already lowercase.
+.TP
+.B prefix\-meta (ESC)
+Metafy the next character typed.
+.SM
+.B ESC
+.B f
+is equivalent to
+.BR Meta\-f .
+.TP
+.B undo (C\-_, C\-x C\-u)
+Incremental undo, separately remembered for each line.
+.TP
+.B revert\-line (M\-r)
+Undo all changes made to this line.  This is like executing the
+.B undo
+command enough times to return the line to its initial state.
+.TP
+.B tilde\-expand (M\-&)
+Perform tilde expansion on the current word.
+.TP
+.B set\-mark (C\-@, M\-<space>)
+Set the mark to the point.  If a
+numeric argument is supplied, the mark is set to that position.
+.TP
+.B exchange\-point\-and\-mark (C\-x C\-x)
+Swap the point with the mark.  The current cursor position is set to
+the saved position, and the old cursor position is saved as the mark.
+.TP
+.B character\-search (C\-])
+A character is read and point is moved to the next occurrence of that
+character.  A negative count searches for previous occurrences.
+.TP
+.B character\-search\-backward (M\-C\-])
+A character is read and point is moved to the previous occurrence of that
+character.  A negative count searches for subsequent occurrences.
+.TP
+.B skip\-csi\-sequence
+Read enough characters to consume a multi-key sequence such as those
+defined for keys like Home and End.  Such sequences begin with a
+Control Sequence Indicator (CSI), usually ESC\-[.  If this sequence is
+bound to "\e[", keys producing such sequences will have no effect
+unless explicitly bound to a readline command, instead of inserting
+stray characters into the editing buffer.  This is unbound by default,
+but usually bound to ESC\-[.
+.TP
+.B insert\-comment (M\-#)
+Without a numeric argument, the value of the readline
+.B comment\-begin
+variable is inserted at the beginning of the current line.
+If a numeric argument is supplied, this command acts as a toggle: if
+the characters at the beginning of the line do not match the value
+of \fBcomment\-begin\fP, the value is inserted, otherwise
+the characters in \fBcomment\-begin\fP are deleted from the beginning of
+the line.
+In either case, the line is accepted as if a newline had been typed.
+The default value of
+\fBcomment\-begin\fP causes this command to make the current line
+a shell comment.
+If a numeric argument causes the comment character to be removed, the line
+will be executed by the shell.
+.TP
+.B glob\-complete\-word (M\-g)
+The word before point is treated as a pattern for pathname expansion,
+with an asterisk implicitly appended.  This pattern is used to
+generate a list of matching filenames for possible completions.
+.TP
+.B glob\-expand\-word (C\-x *)
+The word before point is treated as a pattern for pathname expansion,
+and the list of matching filenames is inserted, replacing the word.
+If a numeric argument is supplied, an asterisk is appended before
+pathname expansion.
+.TP
+.B glob\-list\-expansions (C\-x g)
+The list of expansions that would have been generated by
+.B glob\-expand\-word
+is displayed, and the line is redrawn.
+If a numeric argument is supplied, an asterisk is appended before
+pathname expansion.
+.TP
+.B dump\-functions
+Print all of the functions and their key bindings to the
+readline output stream.  If a numeric argument is supplied,
+the output is formatted in such a way that it can be made part
+of an \fIinputrc\fP file.
+.TP
+.B dump\-variables
+Print all of the settable readline variables and their values to the
+readline output stream.  If a numeric argument is supplied,
+the output is formatted in such a way that it can be made part
+of an \fIinputrc\fP file.
+.TP
+.B dump\-macros
+Print all of the readline key sequences bound to macros and the
+strings they output.  If a numeric argument is supplied,
+the output is formatted in such a way that it can be made part
+of an \fIinputrc\fP file.
+.TP
+.B display\-shell\-version (C\-x C\-v)
+Display version information about the current instance of
+.BR bash .
+.PD
+.SS Programmable Completion
+When word completion is attempted for an argument to a command for
+which a completion specification (a \fIcompspec\fP) has been defined
+using the \fBcomplete\fP builtin (see
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below), the programmable completion facilities are invoked.
+.PP
+First, the command name is identified.
+If the command word is the empty string (completion attempted at the
+beginning of an empty line), any compspec defined with
+the \fB\-E\fP option to \fBcomplete\fP is used.
+If a compspec has been defined for that command, the
+compspec is used to generate the list of possible completions for the word.
+If the command word is a full pathname, a compspec for the full
+pathname is searched for first.
+If no compspec is found for the full pathname, an attempt is made to
+find a compspec for the portion following the final slash.
+If those searches do not result in a compspec, any compspec defined with
+the \fB\-D\fP option to \fBcomplete\fP is used as the default.
+If there is no default compspec, \fBbash\fP attempts alias expansion
+on the command word as a final resort, and attempts to find a compspec
+for the command word from any successful expansion.
+.PP
+Once a compspec has been found, it is used to generate the list of
+matching words.
+If a compspec is not found, the default \fBbash\fP completion as
+described above under \fBCompleting\fP is performed.
+.PP
+First, the actions specified by the compspec are used.
+Only matches which are prefixed by the word being completed are
+returned.
+When the
+.B \-f
+or
+.B \-d
+option is used for filename or directory name completion, the shell
+variable
+.SM
+.B FIGNORE
+is used to filter the matches.
+.PP
+Any completions specified by a pathname expansion pattern to the
+\fB\-G\fP option are generated next.
+The words generated by the pattern need not match the word
+being completed.
+The
+.SM
+.B GLOBIGNORE
+shell variable is not used to filter the matches, but the
+.SM
+.B FIGNORE
+variable is used.
+.PP
+Next, the string specified as the argument to the \fB\-W\fP option
+is considered.
+The string is first split using the characters in the
+.SM
+.B IFS
+special variable as delimiters.
+Shell quoting is honored.
+Each word is then expanded using
+brace expansion, tilde expansion, parameter and variable expansion,
+command substitution, and arithmetic expansion,
+as described above under
+.SM
+.BR EXPANSION .
+The results are split using the rules described above under
+\fBWord Splitting\fP.
+The results of the expansion are prefix-matched against the word being
+completed, and the matching words become the possible completions.
+.PP
+After these matches have been generated, any shell function or command
+specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
+When the command or function is invoked, the
+.SM
+.BR COMP_LINE ,
+.SM
+.BR COMP_POINT ,
+.SM
+.BR COMP_KEY ,
+and
+.SM
+.B COMP_TYPE
+variables are assigned values as described above under
+\fBShell Variables\fP.
+If a shell function is being invoked, the
+.SM
+.B COMP_WORDS
+and
+.SM
+.B COMP_CWORD
+variables are also set.
+When the function or command is invoked,
+the first argument (\fB$1\fP) is the name of the command whose arguments are
+being completed,
+the second argument (\fB$2\fP) is the word being completed,
+and the third argument (\fB$3\fP) is the word preceding the word being
+completed on the current command line.
+No filtering of the generated completions against the word being completed
+is performed; the function or command has complete freedom in generating
+the matches.
+.PP
+Any function specified with \fB\-F\fP is invoked first.
+The function may use any of the shell facilities, including the
+\fBcompgen\fP builtin described below, to generate the matches.
+It must put the possible completions in the
+.SM
+.B COMPREPLY
+array variable, one per array element.
+.PP
+Next, any command specified with the \fB\-C\fP option is invoked
+in an environment equivalent to command substitution.
+It should print a list of completions, one per line, to the
+standard output.
+Backslash may be used to escape a newline, if necessary.
+.PP
+After all of the possible completions are generated, any filter
+specified with the \fB\-X\fP option is applied to the list.
+The filter is a pattern as used for pathname expansion; a \fB&\fP
+in the pattern is replaced with the text of the word being completed.
+A literal \fB&\fP may be escaped with a backslash; the backslash
+is removed before attempting a match.
+Any completion that matches the pattern will be removed from the list.
+A leading \fB!\fP negates the pattern; in this case any completion
+not matching the pattern will be removed.
+If the
+.B nocasematch
+shell option is enabled, the match is performed without regard to the case
+of alphabetic characters.
+.PP
+Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
+options are added to each member of the completion list, and the result is
+returned to the readline completion code as the list of possible
+completions.
+.PP
+If the previously-applied actions do not generate any matches, and the
+\fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
+compspec was defined, directory name completion is attempted.
+.PP
+If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
+compspec was defined, directory name completion is attempted and any
+matches are added to the results of the other actions.
+.PP
+By default, if a compspec is found, whatever it generates is returned
+to the completion code as the full set of possible completions.
+The default \fBbash\fP completions are not attempted, and the readline
+default of filename completion is disabled.
+If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
+the compspec was defined, the \fBbash\fP default completions are attempted
+if the compspec generates no matches.
+If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
+compspec was defined, readline's default completion will be performed
+if the compspec (and, if attempted, the default \fBbash\fP completions)
+generate no matches.
+.PP
+When a compspec indicates that directory name completion is desired,
+the programmable completion functions force readline to append a slash
+to completed names which are symbolic links to directories, subject to
+the value of the \fBmark\-directories\fP readline variable, regardless
+of the setting of the \fBmark-symlinked\-directories\fP readline variable.
+.PP
+There is some support for dynamically modifying completions.  This is
+most useful when used in combination with a default completion specified
+with \fBcomplete \-D\fP.
+It's possible for shell functions executed as completion
+handlers to indicate that completion should be retried by returning an
+exit status of 124.  If a shell function returns 124, and changes
+the compspec associated with the command on which completion is being
+attempted (supplied as the first argument when the function is executed),
+programmable completion restarts from the beginning, with an
+attempt to find a new compspec for that command.  This allows a set of
+completions to be built dynamically as completion is attempted, rather than
+being loaded all at once.
+.PP
+For instance, assuming that there is a library of compspecs, each kept in a
+file corresponding to the name of the command, the following default
+completion function would load completions dynamically:
+.PP
+\f(CW_completion_loader()
+.br
+{
+.br
+	. "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
+.br
+}
+.br
+complete -D -F _completion_loader -o bashdefault -o default
+.br
+\fP
+.SH HISTORY
+When the
+.B \-o history
+option to the
+.B set
+builtin is enabled, the shell provides access to the
+\fIcommand history\fP,
+the list of commands previously typed.
+The value of the
+.SM
+.B HISTSIZE
+variable is used as the
+number of commands to save in a history list.
+The text of the last
+.SM
+.B HISTSIZE
+commands (default 500) is saved.  The shell
+stores each command in the history list prior to parameter and
+variable expansion (see
+.SM
+.B EXPANSION
+above) but after history expansion is performed, subject to the
+values of the shell variables
+.SM
+.B HISTIGNORE
+and
+.SM
+.BR HISTCONTROL .
+.PP
+On startup, the history is initialized from the file named by
+the variable
+.SM
+.B HISTFILE
+(default \fI~/.bash_history\fP).
+The file named by the value of
+.SM
+.B HISTFILE
+is truncated, if necessary, to contain no more than
+the number of lines specified by the value of
+.SM
+.BR HISTFILESIZE .
+If \fBHISTFILESIZE\fP is unset, or set to null, a non-numeric value,
+or a numeric value less than zero, the history file is not truncated.
+When the history file is read,
+lines beginning with the history comment character followed immediately
+by a digit are interpreted as timestamps for the following history line.
+These timestamps are optionally displayed depending on the value of the
+.SM
+.B HISTTIMEFORMAT
+variable.
+When a shell with history enabled exits, the last
+.SM
+.B $HISTSIZE
+lines are copied from the history list to
+.SM
+.BR $HISTFILE .
+If the
+.B histappend
+shell option is enabled
+(see the description of
+.B shopt
+under
+.SM
+.B "SHELL BUILTIN COMMANDS"
+below), the lines are appended to the history file,
+otherwise the history file is overwritten.
+If
+.SM
+.B HISTFILE
+is unset, or if the history file is unwritable, the history is
+not saved.
+If the
+.SM
+.B HISTTIMEFORMAT
+variable is set, time stamps are written to the history file, marked
+with the history comment character, so
+they may be preserved across shell sessions.
+This uses the history comment character to distinguish timestamps from
+other history lines.
+After saving the history, the history file is truncated
+to contain no more than
+.SM
+.B HISTFILESIZE
+lines.  If
+.SM
+.B HISTFILESIZE
+is unset, or set to null, a non-numeric value,
+or a numeric value less than zero, the history file is not truncated.
+.PP
+The builtin command
+.B fc
+(see
+.SM
+.B SHELL BUILTIN COMMANDS
+below) may be used to list or edit and re-execute a portion of
+the history list.
+The
+.B history
+builtin may be used to display or modify the history list and
+manipulate the history file.
+When using command-line editing, search commands
+are available in each editing mode that provide access to the
+history list.
+.PP
+The shell allows control over which commands are saved on the history
+list.  The
+.SM
+.B HISTCONTROL
+and
+.SM
+.B HISTIGNORE
+variables may be set to cause the shell to save only a subset of the
+commands entered.
+The
+.B cmdhist
+shell option, if enabled, causes the shell to attempt to save each
+line of a multi-line command in the same history entry, adding
+semicolons where necessary to preserve syntactic correctness.
+The
+.B lithist
+shell option causes the shell to save the command with embedded newlines
+instead of semicolons.  See the description of the
+.B shopt
+builtin below under
+.SM
+.B "SHELL BUILTIN COMMANDS"
+for information on setting and unsetting shell options.
+.SH "HISTORY EXPANSION"
+The shell supports a history expansion feature that
+is similar to the history expansion in
+.BR csh .
+This section describes what syntax features are available.  This
+feature is enabled by default for interactive shells, and can be
+disabled using the
+.B +H
+option to the
+.B set
+builtin command (see
+.SM
+.B SHELL BUILTIN COMMANDS
+below).  Non-interactive shells do not perform history expansion
+by default.
+.PP
+History expansions introduce words from the history list into
+the input stream, making it easy to repeat commands, insert the
+arguments to a previous command into the current input line, or
+fix errors in previous commands quickly.
+.PP
+History expansion is performed immediately after a complete line
+is read, before the shell breaks it into words, and is performed
+on each line individually without taking quoting on previous lines into
+account.
+It takes place in two parts.
+The first is to determine which line from the history list
+to use during substitution.
+The second is to select portions of that line for inclusion into
+the current one.
+The line selected from the history is the \fIevent\fP,
+and the portions of that line that are acted upon are \fIwords\fP.
+Various \fImodifiers\fP are available to manipulate the selected words.
+The line is broken into words in the same fashion as when reading input,
+so that several \fImetacharacter\fP-separated words surrounded by
+quotes are considered one word.
+History expansions are introduced by the appearance of the
+history expansion character, which is \^\fB!\fP\^ by default.
+Only backslash (\^\fB\e\fP\^) and single quotes can quote
+the history expansion character, but the history expansion character is
+also treated as quoted if it immediately precedes the closing double quote
+in a double-quoted string.
+.PP
+Several characters inhibit history expansion if found immediately
+following the history expansion character, even if it is unquoted:
+space, tab, newline, carriage return, and \fB=\fP.
+If the \fBextglob\fP shell option is enabled, \fB(\fP will also
+inhibit expansion.
+.PP
+Several shell options settable with the
+.B shopt
+builtin may be used to tailor the behavior of history expansion.
+If the
+.B histverify
+shell option is enabled (see the description of the
+.B shopt
+builtin below), and
+.B readline
+is being used, history substitutions are not immediately passed to
+the shell parser.
+Instead, the expanded line is reloaded into the
+.B readline
+editing buffer for further modification.
+If
+.B readline
+is being used, and the
+.B histreedit
+shell option is enabled, a failed history substitution will be reloaded
+into the
+.B readline
+editing buffer for correction.
+The
+.B \-p
+option to the
+.B history
+builtin command may be used to see what a history expansion will
+do before using it.
+The
+.B \-s
+option to the
+.B history
+builtin may be used to add commands to the end of the history list
+without actually executing them, so that they are available for
+subsequent recall.
+.PP
+The shell allows control of the various characters used by the
+history expansion mechanism (see the description of
+.B histchars
+above under
+.BR "Shell Variables" ).
+The shell uses
+the history comment character to mark history timestamps when
+writing the history file.
+.SS Event Designators
+An event designator is a reference to a command line entry in the
+history list.
+Unless the reference is absolute, events are relative to the current
+position in the history list.
+.PP
+.PD 0
+.TP
+.B !
+Start a history substitution, except when followed by a
+.BR blank ,
+newline, carriage return, =
+or ( (when the \fBextglob\fP shell option is enabled using
+the \fBshopt\fP builtin).
+.TP
+.B !\fIn\fR
+Refer to command line
+.IR n .
+.TP
+.B !\-\fIn\fR
+Refer to the current command minus
+.IR n .
+.TP
+.B !!
+Refer to the previous command.  This is a synonym for `!\-1'.
+.TP
+.B !\fIstring\fR
+Refer to the most recent command preceding the current position in the
+history list starting with
+.IR string .
+.TP
+.B !?\fIstring\fR\fB[?]\fR
+Refer to the most recent command preceding the current position in the
+history list containing
+.IR string .
+The trailing \fB?\fP may be omitted if
+.I string
+is followed immediately by a newline.
+If \fIstring\fP is missing, the string from the most recent search is used;
+it is an error if there is no previous search string.
+.TP
+.B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
+Quick substitution.  Repeat the previous command, replacing
+.I string1
+with
+.IR string2 .
+Equivalent to
+``!!:s\d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u''
+(see \fBModifiers\fP below).
+.TP
+.B !#
+The entire command line typed so far.
+.PD
+.SS Word Designators
+Word designators are used to select desired words from the event.
+A
+.B :
+separates the event specification from the word designator.
+It may be omitted if the word designator begins with a
+.BR ^ ,
+.BR $ ,
+.BR * ,
+.BR \- ,
+or
+.BR % .
+Words are numbered from the beginning of the line,
+with the first word being denoted by 0 (zero).
+Words are inserted into the current line separated by single spaces.
+.PP
+.PD 0
+.TP
+.B 0 (zero)
+The zeroth word.  For the shell, this is the command
+word.
+.TP
+.I n
+The \fIn\fRth word.
+.TP
+.B ^
+The first argument.  That is, word 1.
+.TP
+.B $
+The last word.  This is usually the last argument, but will expand to the
+zeroth word if there is only one word in the line.
+.TP
+.B %
+The first word matched by the most recent `?\fIstring\fR?' search,
+if the search string begins with a character that is part of a word.
+.TP
+.I x\fB\-\fPy
+A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
+.TP
+.B *
+All of the words but the zeroth.  This is a synonym
+for `\fI1\-$\fP'.  It is not an error to use
+.B *
+if there is just one
+word in the event; the empty string is returned in that case.
+.TP
+.B x*
+Abbreviates \fIx\-$\fP.
+.TP
+.B x\-
+Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
+If \fBx\fP is missing, it defaults to 0.
+.PD
+.PP
+If a word designator is supplied without an event specification, the
+previous command is used as the event.
+.SS Modifiers
+After the optional word designator, there may appear a sequence of
+one or more of the following modifiers, each preceded by a `:'.
+These modify, or edit, the word or words selected from the history event.
+.PP
+.PD 0
+.TP
+.B h
+Remove a trailing filename component, leaving only the head.
+.TP
+.B t
+Remove all leading filename components, leaving the tail.
+.TP
+.B r
+Remove a trailing suffix of the form \fI.xxx\fP, leaving the
+basename.
+.TP
+.B e
+Remove all but the trailing suffix.
+.TP
+.B p
+Print the new command but do not execute it.
+.TP
+.B q
+Quote the substituted words, escaping further substitutions.
+.TP
+.B x
+Quote the substituted words as with
+.BR q ,
+but break into words at
+.B blanks
+and newlines.
+The \fBq\fP and \fBx\fP modifiers are mutually exclusive; the last one
+supplied is used.
+.TP
+.B s/\fIold\fP/\fInew\fP/
+Substitute
+.I new
+for the first occurrence of
+.I old
+in the event line.
+Any character may be used as the delimiter in place of /.
+The final delimiter is optional if it is the last character of the
+event line.
+The delimiter may be quoted in
+.I old
+and
+.I new
+with a single backslash.  If & appears in
+.IR new ,
+it is replaced by
+.IR old .
+A single backslash will quote the &.
+If
+.I old
+is null, it is set to the last
+.I old
+substituted, or, if no previous history substitutions took place,
+the last
+.I string
+in a
+.B !?\fIstring\fR\fB[?]\fR
+search.
+If
+.I new
+is null, each matching
+.I old
+is deleted.
+.TP
+.B &
+Repeat the previous substitution.
+.TP
+.B g
+Cause changes to be applied over the entire event line.  This is
+used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
+or `\fB:&\fP'.  If used with
+`\fB:s\fP', any delimiter can be used
+in place of /, and the final delimiter is optional
+if it is the last character of the event line.
+An \fBa\fP may be used as a synonym for \fBg\fP.
+.TP
+.B G
+Apply the following `\fBs\fP' or `\fB&\fP' modifier once to each word
+in the event line.
+.PD
+.SH "SHELL BUILTIN COMMANDS"
+.\" start of bash_builtins
+.zZ
+.PP
+Unless otherwise noted, each builtin command documented in this
+section as accepting options preceded by
+.B \-
+accepts
+.B \-\-
+to signify the end of the options.
+The \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP/\fB[\fP builtins
+do not accept options and do not treat \fB\-\-\fP specially.
+The \fBexit\fP, \fBlogout\fP, \fBreturn\fP,
+\fBbreak\fP, \fBcontinue\fP, \fBlet\fP,
+and \fBshift\fP builtins accept and process arguments beginning with
+\fB\-\fP without requiring \fB\-\-\fP.
+Other builtins that accept arguments but are not specified as accepting
+options interpret arguments beginning with \fB\-\fP as invalid options and
+require \fB\-\-\fP to prevent this interpretation.
+.sp .5
+.PD 0
+.TP
+\fB:\fP [\fIarguments\fP]
+.PD
+No effect; the command does nothing beyond expanding
+.I arguments
+and performing any specified
+redirections.
+The return status is zero.
+.TP
+\fB .\| \fP \fIfilename\fP [\fIarguments\fP]
+.PD 0
+.TP
+\fBsource\fP \fIfilename\fP [\fIarguments\fP]
+.PD
+Read and execute commands from
+.I filename
+in the current
+shell environment and return the exit status of the last command
+executed from
+.IR filename .
+If
+.I filename
+does not contain a slash, filenames in
+.SM
+.B PATH
+are used to find the directory containing
+.IR filename .
+The file searched for in
+.SM
+.B PATH
+need not be executable.
+When \fBbash\fP is not in \fIposix mode\fP, the current directory is
+searched if no file is found in
+.SM
+.BR PATH .
+If the
+.B sourcepath
+option to the
+.B shopt
+builtin command is turned off, the
+.SM
+.B PATH
+is not searched.
+If any \fIarguments\fP are supplied, they become the positional
+parameters when \fIfilename\fP is executed.  Otherwise the positional
+parameters are unchanged.
+If the \fB\-T\fP option is enabled, \fBsource\fP inherits any trap on
+\fBDEBUG\fP; if it is not, any \fBDEBUG\fP trap string is saved and
+restored around the call to \fBsource\fP, and \fBsource\fP unsets the
+\fBDEBUG\fP trap while it executes.
+If \fB\-T\fP is not set, and the sourced file changes
+the \fBDEBUG\fP trap, the new value is retained when \fBsource\fP completes.
+The return status is the status of the last command exited within
+the script (0 if no commands are executed), and false if
+.I filename
+is not found or cannot be read.
+.TP
+\fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
+\fBAlias\fP with no arguments or with the
+.B \-p
+option prints the list of aliases in the form
+\fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
+When arguments are supplied, an alias is defined for
+each \fIname\fP whose \fIvalue\fP is given.
+A trailing space in \fIvalue\fP causes the next word to be
+checked for alias substitution when the alias is expanded.
+For each \fIname\fP in the argument list for which no \fIvalue\fP
+is supplied, the name and value of the alias is printed.
+\fBAlias\fP returns true unless a \fIname\fP is given for which
+no alias has been defined.
+.TP
+\fBbg\fP [\fIjobspec\fP ...]
+Resume each suspended job \fIjobspec\fP in the background, as if it
+had been started with
+.BR & .
+If
+.I jobspec
+is not present, the shell's notion of the \fIcurrent job\fP is used.
+.B bg
+.I jobspec
+returns 0 unless run when job control is disabled or, when run with
+job control enabled, any specified \fIjobspec\fP was not found
+or was started without job control.
+.TP
+\fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSVX\fP]
+.PD 0
+.TP
+\fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
+.TP
+\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
+.TP
+\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
+.TP
+\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
+.TP
+\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIreadline\-command\fP
+.PD
+Display current
+.B readline
+key and function bindings, bind a key sequence to a
+.B readline
+function or macro, or set a
+.B readline
+variable.
+Each non-option argument is a command as it would appear in
+.IR .inputrc ,
+but each binding or command must be passed as a separate argument;
+e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
+Options, if supplied, have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-m \fIkeymap\fP
+Use
+.I keymap
+as the keymap to be affected by the subsequent bindings.
+Acceptable
+.I keymap
+names are
+\fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
+vi\-move, vi\-command\fP, and
+.IR vi\-insert .
+\fIvi\fP is equivalent to \fIvi\-command\fP (\fIvi\-move\fP is also
+a synonym); \fIemacs\fP is
+equivalent to \fIemacs\-standard\fP.
+.TP
+.B \-l
+List the names of all \fBreadline\fP functions.
+.TP
+.B \-p
+Display \fBreadline\fP function names and bindings in such a way
+that they can be re-read.
+.TP
+.B \-P
+List current \fBreadline\fP function names and bindings.
+.TP
+.B \-s
+Display \fBreadline\fP key sequences bound to macros and the strings
+they output in such a way that they can be re-read.
+.TP
+.B \-S
+Display \fBreadline\fP key sequences bound to macros and the strings
+they output.
+.TP
+.B \-v
+Display \fBreadline\fP variable names and values in such a way that they
+can be re-read.
+.TP
+.B \-V
+List current \fBreadline\fP variable names and values.
+.TP
+.B \-f \fIfilename\fP
+Read key bindings from \fIfilename\fP.
+.TP
+.B \-q \fIfunction\fP
+Query about which keys invoke the named \fIfunction\fP.
+.TP
+.B \-u \fIfunction\fP
+Unbind all keys bound to the named \fIfunction\fP.
+.TP
+.B \-r \fIkeyseq\fP
+Remove any current binding for \fIkeyseq\fP.
+.TP
+.B \-x \fIkeyseq\fP:\fIshell\-command\fP
+Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
+entered.
+When \fIshell\-command\fP is executed, the shell sets the
+.SM
+.B READLINE_LINE
+variable to the contents of the \fBreadline\fP line buffer and the
+.SM
+.B READLINE_POINT
+and
+.SM
+.B READLINE_MARK
+variables to the current location of the insertion point and the saved
+insertion point (the mark), respectively.
+If the executed command changes the value of any of
+.SM
+.BR READLINE_LINE ,
+.SM
+.BR READLINE_POINT ,
+or
+.SM
+.BR READLINE_MARK ,
+those new values will be reflected in the editing state.
+.TP
+.B \-X
+List all key sequences bound to shell commands and the associated commands
+in a format that can be reused as input.
+.PD
+.PP
+The return value is 0 unless an unrecognized option is given or an
+error occurred.
+.RE
+.TP
+\fBbreak\fP [\fIn\fP]
+Exit from within a
+.BR for ,
+.BR while ,
+.BR until ,
+or
+.B select
+loop.  If \fIn\fP is specified, break \fIn\fP levels.
+.I n
+must be \(>= 1.  If
+.I n
+is greater than the number of enclosing loops, all enclosing loops
+are exited.
+The return value is 0 unless \fIn\fP is not greater than or equal to 1.
+.TP
+\fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
+Execute the specified shell builtin, passing it
+.IR arguments ,
+and return its exit status.
+This is useful when defining a
+function whose name is the same as a shell builtin,
+retaining the functionality of the builtin within the function.
+The \fBcd\fP builtin is commonly redefined this way.
+The return status is false if
+.I shell\-builtin
+is not a shell builtin command.
+.TP
+\fBcaller\fP [\fIexpr\fP]
+Returns the context of any active subroutine call (a shell function or
+a script executed with the \fB.\fP or \fBsource\fP builtins).
+Without \fIexpr\fP, \fBcaller\fP displays the line number and source
+filename of the current subroutine call.
+If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
+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 \fIexpr\fP does not correspond to a valid position in the
+call stack.
+.TP
+\fBcd\fP [\fB\-L\fP|[\fB\-P\fP [\fB\-e\fP]] [\-@]] [\fIdir\fP]
+Change the current directory to \fIdir\fP.
+if \fIdir\fP is not supplied, the value of the
+.SM
+.B HOME
+shell variable is the default.
+Any additional arguments following \fIdir\fP are ignored.
+The variable
+.SM
+.B CDPATH
+defines the search path for the directory containing
+.IR dir :
+each directory name in
+.SM
+.B CDPATH
+is searched for \fIdir\fP.
+Alternative directory names in
+.SM
+.B CDPATH
+are separated by a colon (:).  A null directory name in
+.SM
+.B CDPATH
+is the same as the current directory, i.e., ``\fB.\fP''.  If
+.I dir
+begins with a slash (/),
+then
+.SM
+.B CDPATH
+is not used.  The
+.B \-P
+option causes \fBcd\fP to use the physical directory structure
+by resolving symbolic links while traversing \fIdir\fP and
+before processing instances of \fI..\fP in \fIdir\fP (see also the
+.B \-P
+option to the
+.B set
+builtin command); the
+.B \-L
+option forces symbolic links to be followed by resolving the link
+after processing instances of \fI..\fP in \fIdir\fP.
+If \fI..\fP appears in \fIdir\fP, it is processed by removing the
+immediately previous pathname component from \fIdir\fP, back to a slash
+or the beginning of \fIdir\fP.
+If the
+.B \-e
+option is supplied with
+.BR \-P ,
+and the current working directory cannot be successfully determined
+after a successful directory change, \fBcd\fP will return an unsuccessful
+status.
+On systems that support it, the \fB\-@\fP option presents the extended
+attributes associated with a file as a directory.
+An argument of
+.B \-
+is converted to
+.SM
+.B $OLDPWD
+before the directory change is attempted.
+If a non-empty directory name from
+.SM
+.B CDPATH
+is used, or if
+\fB\-\fP 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 value is true if the directory was successfully changed;
+false otherwise.
+.TP
+\fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
+Run
+.I command
+with
+.I args
+suppressing the normal shell function lookup.
+Only builtin commands or commands found in the
+.SM
+.B PATH
+are executed.  If the
+.B \-p
+option is given, the search for
+.I command
+is performed using a default value for
+.SM
+.B PATH
+that is guaranteed to find all of the standard utilities.
+If either the
+.B \-V
+or
+.B \-v
+option is supplied, a description of
+.I command
+is printed.  The
+.B \-v
+option causes a single word indicating the command or filename
+used to invoke
+.I command
+to be displayed; the
+.B \-V
+option produces a more verbose description.
+If the
+.B \-V
+or
+.B \-v
+option is supplied, the exit status is 0 if
+.I command
+was found, and 1 if not.  If neither option is supplied and
+an error occurred or
+.I command
+cannot be found, the exit status is 127.  Otherwise, the exit status of the
+.B command
+builtin is the exit status of
+.IR command .
+.TP
+\fBcompgen\fP [\fIoption\fP] [\fIword\fP]
+Generate possible completion matches for \fIword\fP according to
+the \fIoption\fPs, which may be any option accepted by the
+.B complete
+builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
+the matches to the standard output.
+When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
+set by the programmable completion facilities, while available, will not
+have useful values.
+.sp 1
+The matches will be generated in the same way as if the programmable
+completion code had generated them directly from a completion specification
+with the same flags.
+If \fIword\fP is specified, only those completions matching \fIword\fP
+will be displayed.
+.sp 1
+The return value is true unless an invalid option is supplied, or no
+matches were generated.
+.TP
+\fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-DEI\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP]
+.br
+[\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] [\fB\-X\fP \fIfilterpat\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP] \fIname\fP [\fIname ...\fP]
+.PD 0
+.TP
+\fBcomplete\fP \fB\-pr\fP [\fB\-DEI\fP] [\fIname\fP ...]
+.PD
+Specify how arguments to each \fIname\fP should be completed.
+If the \fB\-p\fP option is supplied, or if no options are supplied,
+existing completion specifications are printed in a way that allows
+them to be reused as input.
+The \fB\-r\fP option removes a completion specification for
+each \fIname\fP, or, if no \fIname\fPs are supplied, all
+completion specifications.
+The \fB\-D\fP option indicates that other supplied options and actions should
+apply to the ``default'' command completion; that is, completion attempted
+on a command for which no completion has previously been defined.
+The \fB\-E\fP option indicates that other supplied options and actions should
+apply to ``empty'' command completion; that is, completion attempted on a
+blank line.
+The \fB\-I\fP option indicates that other supplied options and actions should
+apply to completion on the initial non-assignment word on the line, or after
+a command delimiter such as \fB;\fP or \fB|\fP, which is usually command
+name completion.
+If multiple options are supplied, the \fB\-D\fP option takes precedence
+over \fB\-E\fP, and both take precedence over \fB\-I\fP.
+If any of \fB\-D\fP, \fB\-E\fP, or \fB\-I\fP are supplied, any other
+\fIname\fP arguments are ignored; these completions only apply to the case
+specified by the option.
+.sp 1
+The process of applying these completion specifications when word completion
+is attempted is described above under \fBProgrammable Completion\fP.
+.sp 1
+Other options, if specified, have the following meanings.
+The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
+(and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
+should be quoted to protect them from expansion before the
+.B complete
+builtin is invoked.
+.RS
+.PD 0
+.TP 8
+\fB\-o\fP \fIcomp-option\fP
+The \fIcomp-option\fP controls several aspects of the compspec's behavior
+beyond the simple generation of completions.
+\fIcomp-option\fP may be one of:
+.RS
+.TP 8
+.B bashdefault
+Perform the rest of the default \fBbash\fP completions if the compspec
+generates no matches.
+.TP 8
+.B default
+Use readline's default filename completion if the compspec generates
+no matches.
+.TP 8
+.B dirnames
+Perform directory name completion if the compspec generates no matches.
+.TP 8
+.B filenames
+Tell readline that the compspec generates filenames, so it can perform any
+filename\-specific processing (like adding a slash to directory names,
+quoting special characters, or suppressing trailing spaces).
+Intended to be used with shell functions.
+.TP 8
+.B noquote
+Tell readline not to quote the completed words if they are filenames
+(quoting filenames is the default).
+.TP 8
+.B nosort
+Tell readline not to sort the list of possible completions alphabetically.
+.TP 8
+.B nospace
+Tell readline not to append a space (the default) to words completed at
+the end of the line.
+.TP 8
+.B plusdirs
+After any matches defined by the compspec are generated,
+directory name completion is attempted and any
+matches are added to the results of the other actions.
+.RE
+.TP 8
+\fB\-A\fP \fIaction\fP
+The \fIaction\fP may be one of the following to generate a list of possible
+completions:
+.RS
+.TP 8
+.B alias
+Alias names.  May also be specified as \fB\-a\fP.
+.TP 8
+.B arrayvar
+Array variable names.
+.TP 8
+.B binding
+\fBReadline\fP key binding names.
+.TP 8
+.B builtin
+Names of shell builtin commands.  May also be specified as \fB\-b\fP.
+.TP 8
+.B command
+Command names.  May also be specified as \fB\-c\fP.
+.TP 8
+.B directory
+Directory names.  May also be specified as \fB\-d\fP.
+.TP 8
+.B disabled
+Names of disabled shell builtins.
+.TP 8
+.B enabled
+Names of enabled shell builtins.
+.TP 8
+.B export
+Names of exported shell variables.  May also be specified as \fB\-e\fP.
+.TP 8
+.B file
+File names.  May also be specified as \fB\-f\fP.
+.TP 8
+.B function
+Names of shell functions.
+.TP 8
+.B group
+Group names.  May also be specified as \fB\-g\fP.
+.TP 8
+.B helptopic
+Help topics as accepted by the \fBhelp\fP builtin.
+.TP 8
+.B hostname
+Hostnames, as taken from the file specified by the
+.SM
+.B HOSTFILE
+shell variable.
+.TP 8
+.B job
+Job names, if job control is active.  May also be specified as \fB\-j\fP.
+.TP 8
+.B keyword
+Shell reserved words.  May also be specified as \fB\-k\fP.
+.TP 8
+.B running
+Names of running jobs, if job control is active.
+.TP 8
+.B service
+Service names.  May also be specified as \fB\-s\fP.
+.TP 8
+.B setopt
+Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
+.TP 8
+.B shopt
+Shell option names as accepted by the \fBshopt\fP builtin.
+.TP 8
+.B signal
+Signal names.
+.TP 8
+.B stopped
+Names of stopped jobs, if job control is active.
+.TP 8
+.B user
+User names.  May also be specified as \fB\-u\fP.
+.TP 8
+.B variable
+Names of all shell variables.  May also be specified as \fB\-v\fP.
+.RE
+.TP 8
+\fB\-C\fP \fIcommand\fP
+\fIcommand\fP is executed in a subshell environment, and its output is
+used as the possible completions.
+.TP 8
+\fB\-F\fP \fIfunction\fP
+The shell function \fIfunction\fP is executed in the current shell
+environment.
+When the function is executed,
+the first argument (\fB$1\fP) is the name of the command whose arguments are
+being completed,
+the second argument (\fB$2\fP) is the word being completed,
+and the third argument (\fB$3\fP) is the word preceding the word being
+completed on the current command line.
+When it finishes, the possible completions are retrieved from the value
+of the
+.SM
+.B COMPREPLY
+array variable.
+.TP 8
+\fB\-G\fP \fIglobpat\fP
+The pathname expansion pattern \fIglobpat\fP is expanded to generate
+the possible completions.
+.TP 8
+\fB\-P\fP \fIprefix\fP
+\fIprefix\fP is added at the beginning of each possible completion
+after all other options have been applied.
+.TP 8
+\fB\-S\fP \fIsuffix\fP
+\fIsuffix\fP is appended to each possible completion
+after all other options have been applied.
+.TP 8
+\fB\-W\fP \fIwordlist\fP
+The \fIwordlist\fP is split using the characters in the
+.SM
+.B IFS
+special variable as delimiters, and each resultant word is expanded.
+Shell quoting is honored within \fIwordlist\fP,
+in order to provide a
+mechanism for the words to contain shell metacharacters or characters
+in the value of
+.SM
+.BR IFS .
+The possible completions are the members of the resultant list which
+match the word being completed.
+.TP 8
+\fB\-X\fP \fIfilterpat\fP
+\fIfilterpat\fP is a pattern as used for pathname expansion.
+It is applied to the list of possible completions generated by the
+preceding options and arguments, and each completion matching
+\fIfilterpat\fP is removed from the list.
+A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
+case, any completion not matching \fIfilterpat\fP is removed.
+.PD
+.PP
+The return value is true unless an invalid option is supplied, an option
+other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
+argument, an attempt is made to remove a completion specification for
+a \fIname\fP for which no specification exists, or
+an error occurs adding a completion specification.
+.RE
+.TP
+\fBcompopt\fP [\fB\-o\fP \fIoption\fP] [\fB\-DEI\fP] [\fB+o\fP \fIoption\fP] [\fIname\fP]
+Modify completion options for each \fIname\fP according to the
+\fIoption\fPs, or for the
+currently-executing completion if no \fIname\fPs are supplied.
+If no \fIoption\fPs are given, display the completion options for each
+\fIname\fP or the current completion.
+The possible values of \fIoption\fP are those valid for the \fBcomplete\fP
+builtin described above.
+The \fB\-D\fP option indicates that other supplied options should
+apply to the ``default'' command completion; that is, completion attempted
+on a command for which no completion has previously been defined.
+The \fB\-E\fP option indicates that other supplied options should
+apply to ``empty'' command completion; that is, completion attempted on a
+blank line.
+The \fB\-I\fP option indicates that other supplied options should
+apply to completion on the initial non-assignment word on the line,
+or after a command delimiter such as \fB;\fP or \fB|\fP, which is usually
+command name completion.
+.sp 1
+The return value is true unless an invalid option is supplied, an attempt
+is made to modify the options for a \fIname\fP for which no completion
+specification exists, or an output error occurs.
+.TP
+\fBcontinue\fP [\fIn\fP]
+Resume the next iteration of the enclosing
+.BR for ,
+.BR while ,
+.BR until ,
+or
+.B select
+loop.
+If
+.I n
+is specified, resume at the \fIn\fPth enclosing loop.
+.I n
+must be \(>= 1.  If
+.I n
+is greater than the number of enclosing loops, the last enclosing loop
+(the ``top-level'' loop) is resumed.
+The return value is 0 unless \fIn\fP is not greater than or equal to 1.
+.TP
+\fBdeclare\fP [\fB\-aAfFgiIlnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
+.PD 0
+.TP
+\fBtypeset\fP [\fB\-aAfFgiIlnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
+.PD
+Declare variables and/or give them attributes.
+If no \fIname\fPs are given then display the values of variables.
+The
+.B \-p
+option will display the attributes and values of each
+.IR name .
+When
+.B \-p
+is used with \fIname\fP arguments, additional options,
+other than \fB\-f\fP and \fB\-F\fP, are ignored.
+When
+.B \-p
+is supplied without \fIname\fP arguments, it will display the attributes
+and values of all variables having the attributes specified by the
+additional options.
+If no other options are supplied with \fB\-p\fP, \fBdeclare\fP will display
+the attributes and values of all shell variables.  The \fB\-f\fP option
+will restrict the display to shell functions.
+The
+.B \-F
+option inhibits the display of function definitions; only the
+function name and attributes are printed.
+If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
+the source file name and line number where each \fIname\fP
+is defined are displayed as well.  The
+.B \-F
+option implies
+.BR \-f .
+The
+.B \-g
+option forces variables to be created or modified at the global scope,
+even when \fBdeclare\fP is executed in a shell function.
+It is ignored in all other cases.
+The
+.B \-I
+option causes local variables to inherit the attributes
+(except the \fInameref\fP attribute) 
+and value of any existing variable with the same
+\fIname\fP at a surrounding scope.
+If there is no existing variable, the local variable is initially unset.
+The following options can
+be used to restrict output to variables with the specified attribute or
+to give variables attributes:
+.RS
+.PD 0
+.TP
+.B \-a
+Each \fIname\fP is an indexed array variable (see
+.B Arrays
+above).
+.TP
+.B \-A
+Each \fIname\fP is an associative array variable (see
+.B Arrays
+above).
+.TP
+.B \-f
+Use function names only.
+.TP
+.B \-i
+The variable is treated as an integer; arithmetic evaluation (see
+.SM
+.B "ARITHMETIC EVALUATION"
+above) is performed when the variable is assigned a value.
+.TP
+.B \-l
+When the variable is assigned a value, all upper-case characters are
+converted to lower-case.
+The upper-case attribute is disabled.
+.TP
+.B \-n
+Give each \fIname\fP the \fInameref\fP attribute, making
+it a name reference to another variable.
+That other variable is defined by the value of \fIname\fP.
+All references, assignments, and attribute modifications
+to \fIname\fP, except those using or changing the
+\fB\-n\fP attribute itself, are performed on the variable referenced by
+\fIname\fP's value.
+The nameref attribute cannot be applied to array variables.
+.TP
+.B \-r
+Make \fIname\fPs readonly.  These names cannot then be assigned values
+by subsequent assignment statements or unset.
+.TP
+.B \-t
+Give each \fIname\fP the \fItrace\fP attribute.
+Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
+the calling shell.
+The trace attribute has no special meaning for variables.
+.TP
+.B \-u
+When the variable is assigned a value, all lower-case characters are
+converted to upper-case.
+The lower-case attribute is disabled.
+.TP
+.B \-x
+Mark \fIname\fPs for export to subsequent commands via the environment.
+.PD
+.PP
+Using `+' instead of `\-'
+turns off the attribute instead,
+with the exceptions that \fB+a\fP and \fB+A\fP
+may not be used to destroy array variables and \fB+r\fP will not
+remove the readonly attribute.
+When used in a function,
+.B declare
+and
+.B typeset
+make each
+\fIname\fP local, as with the
+.B local
+command,
+unless the \fB\-g\fP option is supplied.
+If a variable name is followed by =\fIvalue\fP, the value of
+the variable is set to \fIvalue\fP.
+When using \fB\-a\fP or \fB\-A\fP and the compound assignment syntax to
+create array variables, additional attributes do not take effect until
+subsequent assignments.
+The return value is 0 unless an invalid option is encountered,
+an attempt is made to define a function using
+.if n ``\-f foo=bar'',
+.if t \f(CW\-f foo=bar\fP,
+an attempt is made to assign a value to a readonly variable,
+an attempt is made to assign a value to an array variable without
+using the compound assignment syntax (see
+.B Arrays
+above), one of the \fInames\fP is not a valid shell variable name,
+an attempt is made to turn off readonly status for a readonly variable,
+an attempt is made to turn off array status for an array variable,
+or an attempt is made to display a non-existent function with \fB\-f\fP.
+.RE
+.TP
+.B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
+Without options, displays the list of currently remembered directories.
+The default display is on a single line with directory names separated
+by spaces.
+Directories are added to the list with the
+.B pushd
+command; the
+.B popd
+command removes entries from the list.
+The current directory is always the first directory in the stack.
+.RS
+.PD 0
+.TP
+.B \-c
+Clears the directory stack by deleting all of the entries.
+.TP
+.B \-l
+Produces a listing using full pathnames;
+the default listing format uses a tilde to denote the home directory.
+.TP
+.B \-p
+Print the directory stack with one entry per line.
+.TP
+.B \-v
+Print the directory stack with one entry per line,
+prefixing each entry with its index in the stack.
+.TP
+\fB+\fP\fIn\fP
+Displays the \fIn\fPth entry counting from the left of the list
+shown by
+.B dirs
+when invoked without options, starting with zero.
+.TP
+\fB\-\fP\fIn\fP
+Displays the \fIn\fPth entry counting from the right of the list
+shown by
+.B dirs
+when invoked without options, starting with zero.
+.PD
+.PP
+The return value is 0 unless an
+invalid option is supplied or \fIn\fP indexes beyond the end
+of the directory stack.
+.RE
+.TP
+\fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ... | \fIpid\fP ... ]
+Without options, remove each
+.I jobspec
+from the table of active jobs.
+If
+.I jobspec
+is not present, and neither the \fB\-a\fP nor the \fB\-r\fP option
+is supplied, the \fIcurrent job\fP is used.
+If the \fB\-h\fP option is given, each
+.I jobspec
+is not removed from the table, but is marked so that
+.SM
+.B SIGHUP
+is not sent to the job if the shell receives a
+.SM
+.BR SIGHUP .
+If no
+.I jobspec
+is supplied, the
+.B \-a
+option means to remove or mark all jobs; the
+.B \-r
+option without a
+.I jobspec
+argument restricts operation to running jobs.
+The return value is 0 unless a
+.I jobspec
+does not specify a valid job.
+.TP
+\fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
+Output the \fIarg\fPs, separated by spaces, followed by a newline.
+The return status is 0 unless a write error occurs.
+If \fB\-n\fP is specified, the trailing newline is
+suppressed.  If the \fB\-e\fP option is given, interpretation of
+the following backslash-escaped characters is enabled.  The
+.B \-E
+option disables the interpretation of these escape characters,
+even on systems where they are interpreted by default.
+The \fBxpg_echo\fP shell option may be used to
+dynamically determine whether or not \fBecho\fP expands these
+escape characters by default.
+.B echo
+does not interpret \fB\-\-\fP to mean the end of options.
+.B echo
+interprets the following escape sequences:
+.RS
+.PD 0
+.TP
+.B \ea
+alert (bell)
+.TP
+.B \eb
+backspace
+.TP
+.B \ec
+suppress further output
+.TP
+.B \ee
+.TP
+.B \eE
+an escape character
+.TP
+.B \ef
+form feed
+.TP
+.B \en
+new line
+.TP
+.B \er
+carriage return
+.TP
+.B \et
+horizontal tab
+.TP
+.B \ev
+vertical tab
+.TP
+.B \e\e
+backslash
+.TP
+.B \e0\fInnn\fP
+the eight-bit character whose value is the octal value \fInnn\fP
+(zero to three octal digits)
+.TP
+.B \ex\fIHH\fP
+the eight-bit character whose value is the hexadecimal value \fIHH\fP
+(one or two hex digits)
+.TP
+.B \eu\fIHHHH\fP
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+\fIHHHH\fP (one to four hex digits)
+.TP
+.B \eU\fIHHHHHHHH\fP
+the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
+\fIHHHHHHHH\fP (one to eight hex digits)
+.PD
+.RE
+.TP
+\fBenable\fP [\fB\-a\fP] [\fB\-dnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
+Enable and disable builtin shell commands.
+Disabling a builtin allows a disk command which has the same name
+as a shell builtin to be executed without specifying a full pathname,
+even though the shell normally searches for builtins before disk commands.
+If \fB\-n\fP is used, each \fIname\fP
+is disabled; otherwise,
+\fInames\fP are enabled.  For example, to use the
+.B test
+binary found via the
+.SM
+.B PATH
+instead of the shell builtin version, run
+.if t \f(CWenable -n test\fP.
+.if n ``enable -n test''.
+The
+.B \-f
+option means to load the new builtin command
+.I name
+from shared object
+.IR filename ,
+on systems that support dynamic loading.  The
+.B \-d
+option will delete a builtin previously loaded with
+.BR \-f .
+If no \fIname\fP arguments are given, or if the
+.B \-p
+option is supplied, a list of shell builtins is printed.
+With no other option arguments, the list consists of all enabled
+shell builtins.
+If \fB\-n\fP is supplied, only disabled builtins are printed.
+If \fB\-a\fP is supplied, the list printed includes all builtins, with an
+indication of whether or not each is enabled.
+If \fB\-s\fP is supplied, the output is restricted to the POSIX
+\fIspecial\fP builtins.
+The return value is 0 unless a
+.I name
+is not a shell builtin or there is an error loading a new builtin
+from a shared object.
+.TP
+\fBeval\fP [\fIarg\fP ...]
+The \fIarg\fPs are read and concatenated together into a single
+command.  This command is then read and executed by the shell, and
+its exit status is returned as the value of
+.BR eval .
+If there are no
+.IR args ,
+or only null arguments,
+.B eval
+returns 0.
+.TP
+\fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
+If
+.I command
+is specified, it replaces the shell.
+No new process is created.  The
+.I arguments
+become the arguments to \fIcommand\fP.
+If the
+.B \-l
+option is supplied,
+the shell places a dash at the beginning of the zeroth argument passed to
+.IR command .
+This is what
+.IR login (1)
+does.  The
+.B \-c
+option causes
+.I command
+to be executed with an empty environment.  If
+.B \-a
+is supplied, the shell passes
+.I name
+as the zeroth argument to the executed command.
+If
+.I command
+cannot be executed for some reason, a non-interactive shell exits,
+unless the
+.B execfail
+shell option
+is enabled.  In that case, it returns failure.
+An interactive shell returns failure if the file cannot be executed.
+A subshell exits unconditionally if \fBexec\fP fails.
+If
+.I command
+is not specified, any redirections take effect in the current shell,
+and the return status is 0.  If there is a redirection error, the
+return status is 1.
+.TP
+\fBexit\fP [\fIn\fP]
+Cause the shell to exit
+with a status of \fIn\fP.  If
+.I n
+is omitted, the exit status
+is that of the last command executed.
+A trap on
+.SM
+.B EXIT
+is executed before the shell terminates.
+.TP
+\fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
+.PD 0
+.TP
+.B export \-p
+.PD
+The supplied
+.I names
+are marked for automatic export to the environment of
+subsequently executed commands.  If the
+.B \-f
+option is given, the
+.I names
+refer to functions.
+If no
+.I names
+are given, or if the
+.B \-p
+option is supplied, a list
+of names of all exported variables is printed.
+The
+.B \-n
+option causes the export property to be removed from each
+\fIname\fP.
+If a variable name is followed by =\fIword\fP, the value of
+the variable is set to \fIword\fP.
+.B export
+returns an exit status of 0 unless an invalid option is
+encountered,
+one of the \fInames\fP is not a valid shell variable name, or
+.B \-f
+is supplied with a
+.I name
+that is not a function.
+.TP
+\fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-lnr\fP] [\fIfirst\fP] [\fIlast\fP]
+.PD 0
+.TP
+\fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
+.PD
+The first form selects a range of commands from
+.I first
+to
+.I last
+from the history list and displays or edits and re-executes them.
+.I First
+and
+.I last
+may be specified as a string (to locate the last command beginning
+with that string) or as a number (an index into the history list,
+where a negative number is used as an offset from the current
+command number).
+When listing, a \fIfirst\fP or \fIlast\fP of
+0 is equivalent to \-1 and \-0 is equivalent to the current
+command (usually the \fBfc\fP command); otherwise 0 is equivalent to \-1
+and \-0 is invalid.
+If
+.I last
+is not specified, it is set to
+the current command for listing (so that
+.if n ``fc \-l \-10''
+.if t \f(CWfc \-l \-10\fP
+prints the last 10 commands) and to
+.I first
+otherwise.
+If
+.I first
+is not specified, it is set to the previous
+command for editing and \-16 for listing.
+.sp 1
+The
+.B \-n
+option suppresses
+the command numbers when listing.  The
+.B \-r
+option reverses the order of
+the commands.  If the
+.B \-l
+option is given,
+the commands are listed on
+standard output.  Otherwise, the editor given by
+.I ename
+is invoked
+on a file containing those commands.  If
+.I ename
+is not given, the
+value of the
+.SM
+.B FCEDIT
+variable is used, and
+the value of
+.SM
+.B EDITOR
+if
+.SM
+.B FCEDIT
+is not set.  If neither variable is set,
+.FN vi
+is used.  When editing is complete, the edited commands are
+echoed and executed.
+.sp 1
+In the second form, \fIcommand\fP is re-executed after each instance
+of \fIpat\fP is replaced by \fIrep\fP.
+\fICommand\fP is interpreted the same as \fIfirst\fP above.
+A useful alias to use with this is
+.if n ``r="fc -s"'',
+.if t \f(CWr='fc \-s'\fP,
+so that typing
+.if n ``r cc''
+.if t \f(CWr cc\fP
+runs the last command beginning with
+.if n ``cc''
+.if t \f(CWcc\fP
+and typing
+.if n ``r''
+.if t \f(CWr\fP
+re-executes the last command.
+.sp 1
+If the first form is used, the return value is 0 unless an invalid
+option is encountered or
+.I first
+or
+.I last
+specify history lines out of range.
+If the
+.B \-e
+option is supplied, the return value is the value of the last
+command executed or failure if an error occurs with the temporary
+file of commands.  If the second form is used, the return status
+is that of the command re-executed, unless
+.I cmd
+does not specify a valid history line, in which case
+.B fc
+returns failure.
+.TP
+\fBfg\fP [\fIjobspec\fP]
+Resume
+.I jobspec
+in the foreground, and make it the current job.
+If
+.I jobspec
+is not present, the shell's notion of the \fIcurrent job\fP is used.
+The return value is that of the command placed into the foreground,
+or failure if run when job control is disabled or, when run with
+job control enabled, if
+.I jobspec
+does not specify a valid job or
+.I jobspec
+specifies a job that was started without job control.
+.TP
+\fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIarg ...\fP]
+.B getopts
+is used by shell procedures to parse positional parameters.
+.I optstring
+contains the option characters to be recognized; if a character
+is followed by a colon, the option is expected to have an
+argument, which should be separated from it by white space.
+The colon and question mark characters may not be used as
+option characters.
+Each time it is invoked,
+.B getopts
+places the next option in the shell variable
+.IR name ,
+initializing
+.I name
+if it does not exist,
+and the index of the next argument to be processed into the
+variable
+.SM
+.BR OPTIND .
+.SM
+.B OPTIND
+is initialized to 1 each time the shell or a shell script
+is invoked.  When an option requires an argument,
+.B getopts
+places that argument into the variable
+.SM
+.BR OPTARG .
+The shell does not reset
+.SM
+.B OPTIND
+automatically; it must be manually reset between multiple
+calls to
+.B getopts
+within the same shell invocation if a new set of parameters
+is to be used.
+.sp 1
+When the end of options is encountered, \fBgetopts\fP exits with a
+return value greater than zero.
+.SM
+.B OPTIND
+is set to the index of the first non-option argument,
+and \fIname\fP is set to ?.
+.sp 1
+.B getopts
+normally parses the positional parameters, but if more arguments are
+supplied as
+.I arg
+values,
+.B getopts
+parses those instead.
+.sp 1
+.B getopts
+can report errors in two ways.  If the first character of
+.I optstring
+is a colon,
+.I silent
+error reporting is used.  In normal operation, diagnostic messages
+are printed when invalid options or missing option arguments are
+encountered.
+If the variable
+.SM
+.B OPTERR
+is set to 0, no error messages will be displayed, even if the first
+character of
+.I optstring
+is not a colon.
+.sp 1
+If an invalid option is seen,
+.B getopts
+places ? into
+.I name
+and, if not silent,
+prints an error message and unsets
+.SM
+.BR OPTARG .
+If
+.B getopts
+is silent,
+the option character found is placed in
+.SM
+.B OPTARG
+and no diagnostic message is printed.
+.sp 1
+If a required argument is not found, and
+.B getopts
+is not silent,
+a question mark (\^\fB?\fP\^) is placed in
+.IR name ,
+.SM
+.B OPTARG
+is unset, and a diagnostic message is printed.
+If
+.B getopts
+is silent, then a colon (\^\fB:\fP\^) is placed in
+.I name
+and
+.SM
+.B OPTARG
+is set to the option character found.
+.sp 1
+.B getopts
+returns true if an option, specified or unspecified, is found.
+It returns false if the end of options is encountered or an
+error occurs.
+.TP
+\fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
+Each time \fBhash\fP is invoked,
+the full pathname of the command
+.I name
+is determined by searching
+the directories in
+.B $PATH
+and remembered.  Any previously-remembered pathname is discarded.
+If the
+.B \-p
+option is supplied, no path search is performed, and
+.I filename
+is used as the full filename of the command.
+The
+.B \-r
+option causes the shell to forget all
+remembered locations.
+The
+.B \-d
+option causes the shell to forget the remembered location of each \fIname\fP.
+If the
+.B \-t
+option is supplied, the full pathname to which each \fIname\fP corresponds
+is printed.  If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
+the \fIname\fP is printed before the hashed full pathname.
+The
+.B \-l
+option causes output to be displayed in a format that may be reused as input.
+If no arguments are given, or if only \fB\-l\fP is supplied,
+information about remembered commands is printed.
+The return status is true unless a
+.I name
+is not found or an invalid option is supplied.
+.TP
+\fBhelp\fP [\fB\-dms\fP] [\fIpattern\fP]
+Display helpful information about builtin commands.  If
+.I pattern
+is specified,
+.B help
+gives detailed help on all commands matching
+.IR pattern ;
+otherwise help for all the builtins and shell control structures
+is printed.
+.RS
+.PD 0
+.TP
+.B \-d
+Display a short description of each \fIpattern\fP
+.TP
+.B \-m
+Display the description of each \fIpattern\fP in a manpage-like format
+.TP
+.B \-s
+Display only a short usage synopsis for each \fIpattern\fP
+.PD
+.PP
+The return status is 0 unless no command matches
+.IR pattern .
+.RE
+.TP
+\fBhistory [\fIn\fP]
+.PD 0
+.TP
+\fBhistory\fP \fB\-c\fP
+.TP
+\fBhistory \-d\fP \fIoffset\fP
+.TP
+\fBhistory \-d\fP \fIstart\fP\-\fIend\fP
+.TP
+\fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
+.TP
+\fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
+.TP
+\fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
+.PD
+With no options, display the command
+history list with line numbers.  Lines listed
+with a
+.B *
+have been modified.  An argument of
+.I n
+lists only the last
+.I n
+lines.
+If the shell variable
+.SM
+.B HISTTIMEFORMAT
+is set and not null,
+it is used as a format string for \fIstrftime\fP(3) to display
+the time stamp associated with each displayed history entry.
+No intervening blank is printed between the formatted time stamp
+and the history line.
+If \fIfilename\fP is supplied, it is used as the
+name of the history file; if not, the value of
+.SM
+.B HISTFILE
+is used.  Options, if supplied, have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-c
+Clear the history list by deleting all the entries.
+.TP
+\fB\-d\fP \fIoffset\fP
+Delete the history entry at position \fIoffset\fP.
+If \fIoffset\fP is negative, it is interpreted as relative to one greater
+than the last history position, so negative indices count back from the
+end of the history, and an index of \-1 refers to the current
+\fBhistory -d\fP command.
+.TP
+\fB\-d\fP \fIstart\fP\-\fIend\fP
+Delete the history entries between positions \fIstart\fP and \fIend\fP,
+inclusive.  Positive and negative values for \fIstart\fP and \fIend\fP
+are interpreted as described above.
+.TP
+.B \-a
+Append the ``new'' history lines to the history file.
+These are history lines entered since the beginning of the current
+\fBbash\fP session, but not already appended to the history file.
+.TP
+.B \-n
+Read the history lines not already read from the history
+file into the current history list.  These are lines
+appended to the history file since the beginning of the
+current \fBbash\fP session.
+.TP
+.B \-r
+Read the contents of the history file
+and append them to the current history list.
+.TP
+.B \-w
+Write the current history list to the history file, overwriting the
+history file's contents.
+.TP
+.B \-p
+Perform history substitution on the following \fIargs\fP and display
+the result on the standard output.
+Does not store the results in the history list.
+Each \fIarg\fP must be quoted to disable normal history expansion.
+.TP
+.B \-s
+Store the
+.I args
+in the history list as a single entry.  The last command in the
+history list is removed before the
+.I args
+are added.
+.PD
+.PP
+If the
+.SM
+.B HISTTIMEFORMAT
+variable is set, the time stamp information
+associated with each history entry is written to the history file,
+marked with the history comment character.
+When the history file is read, lines beginning with the history
+comment character followed immediately by a digit are interpreted
+as timestamps for the following history entry.
+The return value is 0 unless an invalid option is encountered, an
+error occurs while reading or writing the history file, an invalid
+\fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
+history expansion supplied as an argument to \fB\-p\fP fails.
+.RE
+.TP
+\fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
+.PD 0
+.TP
+\fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
+.PD
+The first form lists the active jobs.  The options have the following
+meanings:
+.RS
+.PD 0
+.TP
+.B \-l
+List process IDs
+in addition to the normal information.
+.TP
+.B \-n
+Display information only about jobs that have changed status since
+the user was last notified of their status.
+.TP
+.B \-p
+List only the process ID of the job's process group
+leader.
+.TP
+.B \-r
+Display only running jobs.
+.TP
+.B \-s
+Display only stopped jobs.
+.PD
+.PP
+If
+.I jobspec
+is given, output is restricted to information about that job.
+The return status is 0 unless an invalid option is encountered
+or an invalid
+.I jobspec
+is supplied.
+.PP
+If the
+.B \-x
+option is supplied,
+.B jobs
+replaces any
+.I jobspec
+found in
+.I command
+or
+.I args
+with the corresponding process group ID, and executes
+.I command
+passing it
+.IR args ,
+returning its exit status.
+.RE
+.TP
+\fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
+.PD 0
+.TP
+\fBkill\fP \fB\-l\fP|\fB\-L\fP [\fIsigspec\fP | \fIexit_status\fP]
+.PD
+Send the signal named by
+.I sigspec
+or
+.I signum
+to the processes named by
+.I pid
+or
+.IR jobspec .
+.I sigspec
+is either a case-insensitive signal name such as
+.SM
+.B SIGKILL
+(with or without the
+.SM
+.B SIG
+prefix) or a signal number;
+.I signum
+is a signal number.
+If
+.I sigspec
+is not present, then
+.SM
+.B SIGTERM
+is assumed.
+An argument of
+.B \-l
+lists the signal names.
+If any arguments are supplied when
+.B \-l
+is given, the names of the signals corresponding to the arguments are
+listed, and the return status is 0.
+The \fIexit_status\fP argument to
+.B \-l
+is a number specifying either a signal number or the exit status of
+a process terminated by a signal.
+The
+.B \-L
+option is equivalent to \fB\-l\fP.
+.B kill
+returns true if at least one signal was successfully sent, or false
+if an error occurs or an invalid option is encountered.
+.TP
+\fBlet\fP \fIarg\fP [\fIarg\fP ...]
+Each
+.I arg
+is an arithmetic expression to be evaluated (see
+.SM
+.B "ARITHMETIC EVALUATION"
+above).
+If the last
+.I arg
+evaluates to 0,
+.B let
+returns 1; 0 is returned otherwise.
+.TP
+\fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ... | \- ]
+For each argument, a local variable named
+.I name
+is created, and assigned
+.IR value .
+The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
+When
+.B local
+is used within a function, it causes the variable
+.I name
+to have a visible scope restricted to that function and its children.
+If \fIname\fP is \-, the set of shell options is made local to the function
+in which \fBlocal\fP is invoked: shell options changed using the
+\fBset\fP builtin inside the function are restored to their original values
+when the function returns.
+The restore is effected as if a series of \fBset\fP commands were executed
+to restore the values that were in place before the function.
+With no operands,
+.B local
+writes a list of local variables to the standard output.  It is
+an error to use
+.B local
+when not within a function.  The return status is 0 unless
+.B local
+is used outside a function, an invalid
+.I name
+is supplied, or
+\fIname\fP is a readonly variable.
+.TP
+.B logout
+Exit a login shell.
+.TP
+\fBmapfile\fP [\fB\-d\fP \fIdelim\fP] [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
+.PD 0
+.TP
+\fBreadarray\fP [\fB\-d\fP \fIdelim\fP] [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
+.PD
+Read lines from the standard input into the indexed array variable
+.IR array ,
+or from file descriptor
+.I fd
+if the
+.B \-u
+option is supplied.
+The variable
+.SM
+.B MAPFILE
+is the default \fIarray\fP.
+Options, if supplied, have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-d
+The first character of \fIdelim\fP is used to terminate each input line,
+rather than newline.
+If \fIdelim\fP is the empty string, \fBmapfile\fP will terminate a line
+when it reads a NUL character.
+.TP
+.B \-n
+Copy at most
+.I count
+lines.  If \fIcount\fP is 0, all lines are copied.
+.TP
+.B \-O
+Begin assigning to
+.I array
+at index
+.IR origin .
+The default index is 0.
+.TP
+.B \-s
+Discard the first \fIcount\fP lines read.
+.TP
+.B \-t
+Remove a trailing \fIdelim\fP (default newline) from each line read.
+.TP
+.B \-u
+Read lines from file descriptor \fIfd\fP instead of the standard input.
+.TP
+.B \-C
+Evaluate
+.I callback
+each time \fIquantum\fP lines are read.  The \fB\-c\fP option specifies
+.IR quantum .
+.TP
+.B \-c
+Specify the number of lines read between each call to
+.IR callback .
+.PD
+.PP
+If
+.B \-C
+is specified without
+.BR \-c ,
+the default quantum is 5000.
+When \fIcallback\fP is evaluated, it is supplied the index of the next
+array element to be assigned and the line to be assigned to that element
+as additional arguments.
+\fIcallback\fP is evaluated after the line is read but before the
+array element is assigned.
+.PP
+If not supplied with an explicit origin, \fBmapfile\fP will clear \fIarray\fP
+before assigning to it.
+.PP
+\fBmapfile\fP returns successfully unless an invalid option or option
+argument is supplied, \fIarray\fP is invalid or unassignable, or if
+\fIarray\fP is not an indexed array.
+.RE
+.TP
+\fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
+Removes entries from the directory stack.  With no arguments,
+removes the top directory from the stack, and performs a
+.B cd
+to the new top directory.
+Arguments, if supplied, have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-n
+Suppresses the normal change of directory when removing directories
+from the stack, so that only the stack is manipulated.
+.TP
+\fB+\fP\fIn\fP
+Removes the \fIn\fPth entry counting from the left of the list
+shown by
+.BR dirs ,
+starting with zero.  For example:
+.if n ``popd +0''
+.if t \f(CWpopd +0\fP
+removes the first directory,
+.if n ``popd +1''
+.if t \f(CWpopd +1\fP
+the second.
+.TP
+\fB\-\fP\fIn\fP
+Removes the \fIn\fPth entry counting from the right of the list
+shown by
+.BR dirs ,
+starting with zero.  For example:
+.if n ``popd -0''
+.if t \f(CWpopd -0\fP
+removes the last directory,
+.if n ``popd -1''
+.if t \f(CWpopd -1\fP
+the next to last.
+.PD
+.PP
+If the
+.B popd
+command is successful, a
+.B dirs
+is performed as well, and the return status is 0.
+.B popd
+returns false if an invalid option is encountered, the directory stack
+is empty, a non-existent directory stack entry is specified, or the
+directory change fails.
+.RE
+.TP
+\fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
+Write the formatted \fIarguments\fP to the standard output under the
+control of the \fIformat\fP.
+The \fB\-v\fP option causes the output to be assigned to the variable
+\fIvar\fP rather than being printed to the standard output.
+.sp 1
+The \fIformat\fP is a character string which contains three types of objects:
+plain characters, which are simply copied to standard output, character
+escape sequences, which are converted and copied to the standard output, and
+format specifications, each of which causes printing of the next successive
+\fIargument\fP.
+In addition to the standard \fIprintf\fP(1) format specifications,
+\fBprintf\fP interprets the following extensions:
+.RS
+.PD 0
+.TP
+.B %b
+causes
+\fBprintf\fP to expand backslash escape sequences in the corresponding
+\fIargument\fP
+in the same way as \fBecho \-e\fP.
+.TP
+.B %q
+causes \fBprintf\fP to output the corresponding
+\fIargument\fP in a format that can be reused as shell input.
+.TP
+.B %(\fIdatefmt\fP)T
+causes \fBprintf\fP to output the date-time string resulting from using
+\fIdatefmt\fP as a format string for \fIstrftime\fP(3).
+The corresponding \fIargument\fP is an integer representing the number of
+seconds since the epoch.
+Two special argument values may be used: \-1 represents the current
+time, and \-2 represents the time the shell was invoked.
+If no argument is specified, conversion behaves as if \-1 had been given.
+This is an exception to the usual \fBprintf\fP behavior.
+.PD
+.PP
+The %b, %q, and %T directives all use the field width and precision
+arguments from the format specification and write that many bytes from
+(or use that wide a field for) the expanded argument, which usually
+contains more characters than the original.
+.PP
+Arguments to non-string format specifiers are treated as C constants,
+except that a leading plus or minus sign is allowed, and if the leading
+character is a single or double quote, the value is the ASCII value of
+the following character.
+.PP
+The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
+If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
+extra format specifications behave as if a zero value or null string, as
+appropriate, had been supplied.
+The return value is zero on success, non-zero on failure.
+.RE
+.TP
+\fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
+.PD 0
+.TP
+\fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
+.PD
+Adds a directory to the top of the directory stack, or rotates
+the stack, making the new top of the stack the current working
+directory.  With no arguments, \fBpushd\fP exchanges the top two directories
+and returns 0, unless the directory stack is empty.
+Arguments, if supplied, have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-n
+Suppresses the normal change of directory when rotating or
+adding directories to the stack, so that only the stack is manipulated.
+.TP
+\fB+\fP\fIn\fP
+Rotates the stack so that the \fIn\fPth directory
+(counting from the left of the list shown by
+.BR dirs ,
+starting with zero)
+is at the top.
+.TP
+\fB\-\fP\fIn\fP
+Rotates the stack so that the \fIn\fPth directory
+(counting from the right of the list shown by
+.BR dirs ,
+starting with zero) is at the top.
+.TP
+.I dir
+Adds
+.I dir
+to the directory stack at the top, making it the
+new current working directory as if it had been supplied as the argument
+to the \fBcd\fP builtin.
+.PD
+.PP
+If the
+.B pushd
+command is successful, a
+.B dirs
+is performed as well.
+If the first form is used,
+.B pushd
+returns 0 unless the cd to
+.I dir
+fails.  With the second form,
+.B pushd
+returns 0 unless the directory stack is empty,
+a non-existent directory stack element is specified,
+or the directory change to the specified new current directory
+fails.
+.RE
+.TP
+\fBpwd\fP [\fB\-LP\fP]
+Print the absolute pathname of the current working directory.
+The pathname printed contains no symbolic links if the
+.B \-P
+option is supplied or the
+.B \-o physical
+option to the
+.B set
+builtin command is enabled.
+If the
+.B \-L
+option is used, the pathname printed may contain symbolic links.
+The return status is 0 unless an error occurs while
+reading the name of the current directory or an
+invalid option is supplied.
+.TP
+\fBread\fP [\fB\-ers\fP] [\fB\-a\fP \fIaname\fP] [\fB\-d\fP \fIdelim\fP] [\fB\-i\fP \fItext\fP] [\fB\-n\fP \fInchars\fP] [\fB\-N\fP \fInchars\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-u\fP \fIfd\fP] [\fIname\fP ...]
+One line is read from the standard input, or from the file descriptor
+\fIfd\fP supplied as an argument to the \fB\-u\fP option,
+split into words as described above under \fBWord Splitting\fP,
+and the first word
+is assigned to the first
+.IR name ,
+the second word to the second
+.IR name ,
+and so on.
+If there are more words than names, the remaining words and their
+intervening delimiters are assigned to the last
+.IR name .
+If there are fewer words read from the input stream than names,
+the remaining names are assigned empty values.
+The characters in
+.SM
+.B IFS
+are used to split the line into words using the same rules the shell
+uses for expansion (described above under \fBWord Splitting\fP).
+The backslash character (\fB\e\fP) may be used to remove any special
+meaning for the next character read and for line continuation.
+Options, if supplied, have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-a \fIaname\fP
+The words are assigned to sequential indices
+of the array variable
+.IR aname ,
+starting at 0.
+.I aname
+is unset before any new values are assigned.
+Other \fIname\fP arguments are ignored.
+.TP
+.B \-d \fIdelim\fP
+The first character of \fIdelim\fP is used to terminate the input line,
+rather than newline.
+If \fIdelim\fP is the empty string, \fBread\fP will terminate a line
+when it reads a NUL character.
+.TP
+.B \-e
+If the standard input
+is coming from a terminal,
+.B readline
+(see
+.SM
+.B READLINE
+above) is used to obtain the line.
+Readline uses the current (or default, if line editing was not previously
+active) editing settings, but uses Readline's default filename completion.
+.TP
+.B \-i \fItext\fP
+If
+.B readline
+is being used to read the line, \fItext\fP is placed into the editing
+buffer before editing begins.
+.TP
+.B \-n \fInchars\fP
+\fBread\fP returns after reading \fInchars\fP characters rather than
+waiting for a complete line of input, but honors a delimiter if fewer
+than \fInchars\fP characters are read before the delimiter.
+.TP
+.B \-N \fInchars\fP
+\fBread\fP returns after reading exactly \fInchars\fP characters rather
+than waiting for a complete line of input, unless EOF is encountered or
+\fBread\fP times out.
+Delimiter characters encountered in the input are
+not treated specially and do not cause \fBread\fP to return until
+\fInchars\fP characters are read.
+The result is not split on the characters in \fBIFS\fP; the intent is
+that the variable is assigned exactly the characters read
+(with the exception of backslash; see the \fB\-r\fP option below).
+.TP
+.B \-p \fIprompt\fP
+Display \fIprompt\fP on standard error, without a
+trailing newline, before attempting to read any input.  The prompt
+is displayed only if input is coming from a terminal.
+.TP
+.B \-r
+Backslash does not act as an escape character.
+The backslash is considered to be part of the line.
+In particular, a backslash-newline pair may not then be used as a line
+continuation.
+.TP
+.B \-s
+Silent mode.  If input is coming from a terminal, characters are
+not echoed.
+.TP
+.B \-t \fItimeout\fP
+Cause \fBread\fP to time out and return failure if a complete line of
+input (or a specified number of characters)
+is not read within \fItimeout\fP seconds.
+\fItimeout\fP may be a decimal number with a fractional portion following
+the decimal point.
+This option is only effective if \fBread\fP is reading input from a
+terminal, pipe, or other special file; it has no effect when reading
+from regular files.
+If \fBread\fP times out, \fBread\fP saves any partial input read into
+the specified variable \fIname\fP.
+If \fItimeout\fP is 0, \fBread\fP returns immediately, without trying to
+read any data.  The exit status is 0 if input is available on
+the specified file descriptor, non-zero otherwise.
+The exit status is greater than 128 if the timeout is exceeded.
+.TP
+.B \-u \fIfd\fP
+Read input from file descriptor \fIfd\fP.
+.PD
+.PP
+If no
+.I names
+are supplied, the line read,
+without the ending delimiter but otherwise unmodified,
+is assigned to the variable
+.SM
+.BR REPLY .
+The exit status is zero, unless end-of-file is encountered, \fBread\fP
+times out (in which case the status is greater than 128),
+a variable assignment error (such as assigning to a readonly variable) occurs,
+or an invalid file descriptor is supplied as the argument to \fB\-u\fP.
+.RE
+.TP
+\fBreadonly\fP [\fB\-aAf\fP] [\fB\-p\fP] [\fIname\fP[=\fIword\fP] ...]
+.PD
+The given
+\fInames\fP are marked readonly; the values of these
+.I names
+may not be changed by subsequent assignment.
+If the
+.B \-f
+option is supplied, the functions corresponding to the
+\fInames\fP are so
+marked.
+The
+.B \-a
+option restricts the variables to indexed arrays; the
+.B \-A
+option restricts the variables to associative arrays.
+If both options are supplied,
+.B \-A
+takes precedence.
+If no
+.I name
+arguments are given, or if the
+.B \-p
+option is supplied, a list of all readonly names is printed.
+The other options may be used to restrict the output to a subset of
+the set of readonly names.
+The
+.B \-p
+option causes output to be displayed in a format that
+may be reused as input.
+If a variable name is followed by =\fIword\fP, the value of
+the variable is set to \fIword\fP.
+The return status is 0 unless an invalid option is encountered,
+one of the
+.I names
+is not a valid shell variable name, or
+.B \-f
+is supplied with a
+.I name
+that is not a function.
+.TP
+\fBreturn\fP [\fIn\fP]
+Causes a function to stop executing and return the value specified by
+.I n
+to its caller.
+If
+.I n
+is omitted, the return status is that of the last command
+executed in the function body.
+If \fBreturn\fP is executed by a trap handler, the last command used to
+determine the status is the last command executed before the trap handler.
+If \fBreturn\fP is executed during a \fBDEBUG\fP trap, the last command
+used to determine the status is the last command executed by the trap
+handler before \fBreturn\fP was invoked.
+If
+.B return
+is used outside a function,
+but during execution of a script by the
+.B .
+(\fBsource\fP) command, it causes the shell to stop executing
+that script and return either
+.I n
+or the exit status of the last command executed within the
+script as the exit status of the script.
+If \fIn\fP is supplied, the return value is its least significant
+8 bits.
+The return status is non-zero if
+.B return
+is supplied a non-numeric argument, or
+is used outside a
+function and not during execution of a script by \fB.\fP\^ or \fBsource\fP.
+Any command associated with the \fBRETURN\fP trap is executed
+before execution resumes after the function or script.
+.TP
+\fBset\fP [\fB\-\-abefhkmnptuvxBCEHPT\fP] [\fB\-o\fP \fIoption\-name\fP] [\fIarg\fP ...]
+.PD 0
+.TP
+\fBset\fP [\fB+abefhkmnptuvxBCEHPT\fP] [\fB+o\fP \fIoption\-name\fP] [\fIarg\fP ...]
+.PD
+Without options, the name and value of each shell variable are displayed
+in a format that can be reused as input
+for setting or resetting the currently-set variables.
+Read-only variables cannot be reset.
+In \fIposix mode\fP, only shell variables are listed.
+The output is sorted according to the current locale.
+When options are specified, they set or unset shell attributes.
+Any arguments remaining after option processing are treated
+as values for the positional parameters and are assigned, in order, to
+.BR $1 ,
+.BR $2 ,
+.B ...
+.BR $\fIn\fP .
+Options, if specified, have the following meanings:
+.RS
+.PD 0
+.TP 8
+.B \-a
+Each variable or function that is created or modified is given the
+export attribute and marked for export to the environment of
+subsequent commands.
+.TP 8
+.B \-b
+Report the status of terminated background jobs
+immediately, rather than before the next primary prompt.  This is
+effective only when job control is enabled.
+.TP 8
+.B \-e
+Exit immediately if a
+\fIpipeline\fP (which may consist of a single \fIsimple command\fP),
+a \fIlist\fP,
+or a \fIcompound command\fP
+(see
+.SM
+.B SHELL GRAMMAR
+above), exits with a non-zero status.
+The shell does not exit if the
+command that fails is part of the command list immediately following a
+.B while
+or
+.B until
+keyword,
+part of the test following the
+.B if
+or
+.B elif
+reserved words, part of any command executed in a
+.B &&
+or
+.B ||
+list except the command following the final \fB&&\fP or \fB||\fP,
+any command in a pipeline but the last,
+or if the command's return value is
+being inverted with
+.BR ! .
+If a compound command other than a subshell
+returns a non-zero status because a command failed
+while \fB\-e\fP was being ignored, the shell does not exit.
+A trap on \fBERR\fP, if set, is executed before the shell exits.
+This option applies to the shell environment and each subshell environment
+separately (see
+.SM
+.B "COMMAND EXECUTION ENVIRONMENT"
+above), and may cause
+subshells to exit before executing all the commands in the subshell.
+.if t .sp 0.5
+.if n .sp 1
+If a compound command or shell function executes in a context
+where \fB\-e\fP is being ignored,
+none of the commands executed within the compound command or function body
+will be affected by the \fB\-e\fP setting, even if \fB\-e\fP is set
+and a command returns a failure status.
+If a compound command or shell function sets \fB\-e\fP while executing in
+a context where \fB\-e\fP is ignored, that setting will not have any
+effect until the compound command or the command containing the function
+call completes.
+.TP 8
+.B \-f
+Disable pathname expansion.
+.TP 8
+.B \-h
+Remember the location of commands as they are looked up for execution.
+This is enabled by default.
+.TP 8
+.B \-k
+All arguments in the form of assignment statements
+are placed in the environment for a command, not just
+those that precede the command name.
+.TP 8
+.B \-m
+Monitor mode.  Job control is enabled.  This option is on
+by default for interactive shells on systems that support
+it (see
+.SM
+.B JOB CONTROL
+above).
+All processes run in a separate process group.
+When a background job completes, the shell prints a line
+containing its exit status.
+.TP 8
+.B \-n
+Read commands but do not execute them.
+This may be used to check a shell script for syntax errors.
+This is ignored by interactive shells.
+.TP 8
+.B \-o \fIoption\-name\fP
+The \fIoption\-name\fP can be one of the following:
+.RS
+.TP 8
+.B allexport
+Same as
+.BR \-a .
+.TP 8
+.B braceexpand
+Same as
+.BR \-B .
+.TP 8
+.B emacs
+Use an emacs-style command line editing interface.  This is enabled
+by default when the shell is interactive, unless the shell is started
+with the
+.B \-\-noediting
+option.
+This also affects the editing interface used for \fBread \-e\fP.
+.TP 8
+.B errexit
+Same as
+.BR \-e .
+.TP 8
+.B errtrace
+Same as
+.BR \-E .
+.TP 8
+.B functrace
+Same as
+.BR \-T .
+.TP 8
+.B hashall
+Same as
+.BR \-h .
+.TP 8
+.B histexpand
+Same as
+.BR \-H .
+.TP 8
+.B history
+Enable command history, as described above under
+.SM
+.BR HISTORY .
+This option is on by default in interactive shells.
+.TP 8
+.B ignoreeof
+The effect is as if the shell command
+.if t \f(CWIGNOREEOF=10\fP
+.if n ``IGNOREEOF=10''
+had been executed
+(see
+.B Shell Variables
+above).
+.TP 8
+.B keyword
+Same as
+.BR \-k .
+.TP 8
+.B monitor
+Same as
+.BR \-m .
+.TP 8
+.B noclobber
+Same as
+.BR \-C .
+.TP 8
+.B noexec
+Same as
+.BR \-n .
+.TP 8
+.B noglob
+Same as
+.BR \-f .
+.TP 8
+.B nolog
+Currently ignored.
+.TP 8
+.B notify
+Same as
+.BR \-b .
+.TP 8
+.B nounset
+Same as
+.BR \-u .
+.TP 8
+.B onecmd
+Same as
+.BR \-t .
+.TP 8
+.B physical
+Same as
+.BR \-P .
+.TP 8
+.B 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.
+.TP 8
+.B posix
+Change the behavior of
+.B bash
+where the default operation differs
+from the POSIX standard to match the standard (\fIposix mode\fP).
+See
+.SM
+.B "SEE ALSO"
+below for a reference to a document that details how posix mode affects
+bash's behavior.
+.TP 8
+.B privileged
+Same as
+.BR \-p .
+.TP 8
+.B verbose
+Same as
+.BR \-v .
+.TP 8
+.B vi
+Use a vi-style command line editing interface.
+This also affects the editing interface used for \fBread \-e\fP.
+.TP 8
+.B xtrace
+Same as
+.BR \-x .
+.sp .5
+.PP
+If
+.B \-o
+is supplied with no \fIoption\-name\fP, the values of the current options are
+printed.
+If
+.B +o
+is supplied with no \fIoption\-name\fP, a series of
+.B set
+commands to recreate the current option settings is displayed on
+the standard output.
+.RE
+.TP 8
+.B \-p
+Turn on
+.I privileged
+mode.  In this mode, the
+.SM
+.B $ENV
+and
+.SM
+.B $BASH_ENV
+files are not processed, shell functions are not inherited from the
+environment, and the
+.SM
+.BR SHELLOPTS ,
+.SM
+.BR BASHOPTS ,
+.SM
+.BR CDPATH ,
+and
+.SM
+.B 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 \fB\-p\fP option is not supplied, these actions
+are taken and the effective user id is set to the real user id.
+If the \fB\-p\fP option is supplied at startup, the effective user id is
+not reset.
+Turning this option off causes the effective user
+and group ids to be set to the real user and group ids.
+.TP 8
+.B \-t
+Exit after reading and executing one command.
+.TP 8
+.B \-u
+Treat unset variables and parameters other than the special
+parameters "@" and "*" as an error when performing
+parameter expansion.  If expansion is attempted on an
+unset variable or parameter, the shell prints an error message, and,
+if not interactive, exits with a non-zero status.
+.TP 8
+.B \-v
+Print shell input lines as they are read.
+.TP 8
+.B \-x
+After expanding each \fIsimple command\fP,
+\fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
+arithmetic \fBfor\fP command, display the expanded value of
+.SM
+.BR PS4 ,
+followed by the command and its expanded arguments
+or associated word list.
+.TP 8
+.B \-B
+The shell performs brace expansion (see
+.B Brace Expansion
+above).  This is on by default.
+.TP 8
+.B \-C
+If set,
+.B bash
+does not overwrite an existing file with the
+.BR > ,
+.BR >& ,
+and
+.B <>
+redirection operators.  This may be overridden when
+creating output files by using the redirection operator
+.B >|
+instead of
+.BR > .
+.TP 8
+.B \-E
+If set, any trap on \fBERR\fP is inherited by shell functions, command
+substitutions, and commands executed in a subshell environment.
+The \fBERR\fP trap is normally not inherited in such cases.
+.TP 8
+.B \-H
+Enable
+.B !
+style history substitution.  This option is on by
+default when the shell is interactive.
+.TP 8
+.B \-P
+If set, the shell does not resolve symbolic links when executing
+commands such as
+.B cd
+that change the current working directory.  It uses the
+physical directory structure instead.  By default,
+.B bash
+follows the logical chain of directories when performing commands
+which change the current directory.
+.TP 8
+.B \-T
+If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
+functions, command substitutions, and commands executed in a
+subshell environment.
+The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
+in such cases.
+.TP 8
+.B \-\-
+If no arguments follow this option, then the positional parameters are
+unset.  Otherwise, the positional parameters are set to the
+\fIarg\fPs, even if some of them begin with a
+.BR \- .
+.TP 8
+.B \-
+Signal the end of options, cause all remaining \fIarg\fPs to be
+assigned to the positional parameters.  The
+.B \-x
+and
+.B \-v
+options are turned off.
+If there are no \fIarg\fPs,
+the positional parameters remain unchanged.
+.PD
+.PP
+The options are off by default unless otherwise noted.
+Using + rather than \- causes these options to be turned off.
+The options can also be specified as arguments to an invocation of
+the shell.
+The current set of options may be found in
+.BR $\- .
+The return status is always true unless an invalid option is encountered.
+.RE
+.TP
+\fBshift\fP [\fIn\fP]
+The positional parameters from \fIn\fP+1 ... are renamed to
+.B $1
+.B ....
+Parameters represented by the numbers \fB$#\fP
+down to \fB$#\fP\-\fIn\fP+1 are unset.
+.I n
+must be a non-negative number less than or equal to \fB$#\fP.
+If
+.I n
+is 0, no parameters are changed.
+If
+.I n
+is not given, it is assumed to be 1.
+If
+.I n
+is greater than \fB$#\fP, the positional parameters are not changed.
+The return status is greater than zero if
+.I n
+is greater than
+.B $#
+or less than zero; otherwise 0.
+.TP
+\fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
+Toggle the values of settings controlling optional shell behavior.
+The settings can be either those listed below, or, if the
+.B \-o
+option is used, those available with the
+.B \-o
+option to the \fBset\fP builtin command.
+With no options, or with the
+.B \-p
+option, a list of all settable options is displayed, with
+an indication of whether or not each is set;
+if \fIoptnames\fP are supplied, the output is restricted to those options.
+The \fB\-p\fP option causes output to be displayed in a form that
+may be reused as input.
+Other options have the following meanings:
+.RS
+.PD 0
+.TP
+.B \-s
+Enable (set) each \fIoptname\fP.
+.TP
+.B \-u
+Disable (unset) each \fIoptname\fP.
+.TP
+.B \-q
+Suppresses normal output (quiet mode); the return status indicates
+whether the \fIoptname\fP is set or unset.
+If multiple \fIoptname\fP arguments are given with
+.BR \-q ,
+the return status is zero if all \fIoptnames\fP are enabled; non-zero
+otherwise.
+.TP
+.B \-o
+Restricts the values of \fIoptname\fP to be those defined for the
+.B \-o
+option to the
+.B set
+builtin.
+.PD
+.PP
+If either
+.B \-s
+or
+.B \-u
+is used with no \fIoptname\fP arguments,
+.B shopt
+shows only those options which are set or unset, respectively.
+Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
+by default.
+.PP
+The return status when listing options is zero if all \fIoptnames\fP
+are enabled, non-zero otherwise.  When setting or unsetting options,
+the return status is zero unless an \fIoptname\fP is not a valid shell
+option.
+.PP
+The list of \fBshopt\fP options is:
+.if t .sp .5v
+.if n .sp 1v
+.PD 0
+.TP 8
+.B assoc_expand_once
+If set, the shell suppresses multiple evaluation of associative array
+subscripts during arithmetic expression evaluation, while executing
+builtins that can perform variable assignments,
+and while executing builtins that perform array dereferencing.
+.TP 8
+.B autocd
+If set, a command name that is the name of a directory is executed as if
+it were the argument to the \fBcd\fP command.
+This option is only used by interactive shells.
+.TP 8
+.B cdable_vars
+If set, an argument to the
+.B 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.
+.TP 8
+.B cdspell
+If set, minor errors in the spelling of a directory component in a
+.B cd
+command will be corrected.
+The errors checked for are transposed characters,
+a missing character, and one character too many.
+If a correction is found, the corrected filename is printed,
+and the command proceeds.
+This option is only used by interactive shells.
+.TP 8
+.B checkhash
+If set, \fBbash\fP 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.
+.TP 8
+.B checkjobs
+If set, \fBbash\fP 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 (see
+.SM
+.B "JOB CONTROL"
+above).  The shell always
+postpones exiting if any jobs are stopped.
+.TP 8
+.B checkwinsize
+If set, \fBbash\fP checks the window size after each external (non-builtin)
+command and, if necessary, updates the values of
+.SM
+.B LINES
+and
+.SM
+.BR COLUMNS .
+This option is enabled by default.
+.TP 8
+.B cmdhist
+If set,
+.B 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.
+This option is enabled by default, but only has an effect if command
+history is enabled, as described above under
+.SM
+.BR HISTORY .
+.PD 0
+.TP 8
+.B compat31
+.TP 8
+.B compat32
+.TP 8
+.B compat40
+.TP 8
+.B compat41
+.TP 8
+.B compat42
+.TP 8
+.B compat43
+.TP 8
+.B compat44
+.PD
+These control aspects of the shell's compatibility mode
+(see
+.SM
+.B "SHELL COMPATIBILITY MODE"
+below).
+.TP 8
+.B complete_fullquote
+If set,
+.B bash
+quotes all shell metacharacters in filenames and directory names when
+performing completion.
+If not set,
+.B bash
+removes metacharacters such as the dollar sign from the set of
+characters that will be quoted in completed filenames
+when these metacharacters appear in shell variable references in words to be
+completed.
+This means that dollar signs in variable names that expand to directories
+will not be quoted;
+however, any dollar signs appearing in filenames will not be quoted, either.
+This is active only when bash is using backslashes to quote completed
+filenames.
+This variable is set by default, which is the default bash behavior in
+versions through 4.2.
+.TP 8
+.B direxpand
+If set,
+.B bash
+replaces directory names with the results of word expansion when performing
+filename completion.  This changes the contents of the readline editing
+buffer.
+If not set,
+.B bash
+attempts to preserve what the user typed.
+.TP 8
+.B dirspell
+If set,
+.B bash
+attempts spelling correction on directory names during word completion
+if the directory name initially supplied does not exist.
+.TP 8
+.B dotglob
+If set,
+.B bash
+includes filenames beginning with a `.' in the results of pathname
+expansion.
+The filenames
+.B ``.''
+and
+.B ``..''
+must always be matched explicitly, even if
+.B dotglob
+is set.
+.TP 8
+.B execfail
+If set, a non-interactive shell will not exit if
+it cannot execute the file specified as an argument to the
+.B exec
+builtin command.  An interactive shell does not exit if
+.B exec
+fails.
+.TP 8
+.B expand_aliases
+If set, aliases are expanded as described above under
+.SM
+.BR ALIASES .
+This option is enabled by default for interactive shells.
+.TP 8
+.B extdebug
+If set at shell invocation,
+or in a shell startup file,
+arrange to execute the debugger profile
+before the shell starts, identical to the \fB\-\-debugger\fP option.
+If set after invocation, behavior intended for use by debuggers is enabled:
+.RS
+.TP
+.B 1.
+The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
+file name and line number corresponding to each function name supplied
+as an argument.
+.TP
+.B 2.
+If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
+next command is skipped and not executed.
+.TP
+.B 3.
+If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
+shell is executing in a subroutine (a shell function or a shell script
+executed by the \fB.\fP or \fBsource\fP builtins), the shell simulates
+a call to \fBreturn\fP.
+.TP
+.B 4.
+.SM
+.B BASH_ARGC
+and
+.SM
+.B BASH_ARGV
+are updated as described in their descriptions above.
+.TP
+.B 5.
+Function tracing is enabled: command substitution, shell functions, and
+subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
+\fBDEBUG\fP and \fBRETURN\fP traps.
+.TP
+.B 6.
+Error tracing is enabled: command substitution, shell functions, and
+subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
+\fBERR\fP trap.
+.RE
+.TP 8
+.B extglob
+If set, the extended pattern matching features described above under
+\fBPathname Expansion\fP are enabled.
+.TP 8
+.B extquote
+If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
+performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
+enclosed in double quotes.  This option is enabled by default.
+.TP 8
+.B failglob
+If set, patterns which fail to match filenames during pathname expansion
+result in an expansion error.
+.TP 8
+.B force_fignore
+If set, the suffixes specified by the
+.SM
+.B FIGNORE
+shell variable
+cause words to be ignored when performing word completion even if
+the ignored words are the only possible completions.
+See
+.SM
+\fBSHELL VARIABLES\fP
+above for a description of
+.SM
+.BR FIGNORE .
+This option is enabled by default.
+.TP 8
+.B globasciiranges
+If set, range expressions used in pattern matching bracket expressions (see
+.SM
+.B Pattern Matching
+above) behave as if in the traditional C locale when performing
+comparisons.  That is, the current locale's collating sequence
+is not taken into account, so
+.B b
+will not collate between
+.B A
+and
+.BR B ,
+and upper-case and lower-case ASCII characters will collate together.
+.TP 8
+.B globstar
+If set, the pattern \fB**\fP used in a pathname expansion context will
+match all files and zero or more directories and subdirectories.
+If the pattern is followed by a \fB/\fP, only directories and
+subdirectories match.
+.TP 8
+.B gnu_errfmt
+If set, shell error messages are written in the standard GNU error
+message format.
+.TP 8
+.B histappend
+If set, the history list is appended to the file named by the value
+of the
+.SM
+.B HISTFILE
+variable when the shell exits, rather than overwriting the file.
+.TP 8
+.B histreedit
+If set, and
+.B readline
+is being used, a user is given the opportunity to re-edit a
+failed history substitution.
+.TP 8
+.B histverify
+If set, and
+.B 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 \fBreadline\fP editing buffer, allowing further modification.
+.TP 8
+.B hostcomplete
+If set, and
+.B readline
+is being used, \fBbash\fP will attempt to perform hostname completion when a
+word containing a \fB@\fP is being completed (see
+.B Completing
+under
+.SM
+.B READLINE
+above).
+This is enabled by default.
+.TP 8
+.B huponexit
+If set, \fBbash\fP will send
+.SM
+.B SIGHUP
+to all jobs when an interactive login shell exits.
+.TP 8
+.B inherit_errexit
+If set, command substitution inherits the value of the \fBerrexit\fP option,
+instead of unsetting it in the subshell environment.
+This option is enabled when \fIposix mode\fP is enabled.
+.TP 8
+.B interactive_comments
+If set, allow a word beginning with
+.B #
+to cause that word and all remaining characters on that
+line to be ignored in an interactive shell (see
+.SM
+.B COMMENTS
+above).  This option is enabled by default.
+.TP 8
+.B lastpipe
+If set, and job control is not active, the shell runs the last command of
+a pipeline not executed in the background in the current shell environment.
+.TP 8
+.B lithist
+If set, and the
+.B cmdhist
+option is enabled, multi-line commands are saved to the history with
+embedded newlines rather than using semicolon separators where possible.
+.TP 8
+.B localvar_inherit
+If set, local variables inherit the value and attributes of a variable of
+the same name that exists at a previous scope before any new value is
+assigned.  The nameref attribute is not inherited.
+.TP 8
+.B localvar_unset
+If set, calling \fBunset\fP on local variables in previous function scopes
+marks them so subsequent lookups find them unset until that function
+returns. This is identical to the behavior of unsetting local variables
+at the current function scope.
+.TP 8
+.B login_shell
+The shell sets this option if it is started as a login shell (see
+.SM
+.B "INVOCATION"
+above).
+The value may not be changed.
+.TP 8
+.B mailwarn
+If set, and a file that \fBbash\fP is checking for mail has been
+accessed since the last time it was checked, the message ``The mail in
+\fImailfile\fP has been read'' is displayed.
+.TP 8
+.B no_empty_cmd_completion
+If set, and
+.B readline
+is being used,
+.B bash
+will not attempt to search the
+.SM
+.B PATH
+for possible completions when
+completion is attempted on an empty line.
+.TP 8
+.B nocaseglob
+If set,
+.B bash
+matches filenames in a case\-insensitive fashion when performing pathname
+expansion (see
+.B Pathname Expansion
+above).
+.TP 8
+.B nocasematch
+If set,
+.B bash
+matches patterns in a case\-insensitive fashion when performing matching
+while executing \fBcase\fP or \fB[[\fP conditional commands,
+when performing pattern substitution word expansions,
+or when filtering possible completions as part of programmable completion.
+.TP 8
+.B nullglob
+If set,
+.B bash
+allows patterns which match no
+files (see
+.B Pathname Expansion
+above)
+to expand to a null string, rather than themselves.
+.TP 8
+.B progcomp
+If set, the programmable completion facilities (see
+\fBProgrammable Completion\fP above) are enabled.
+This option is enabled by default.
+.TP 8
+.B progcomp_alias
+If set, and programmable completion is enabled, \fBbash\fP treats a command
+name that doesn't have any completions as a possible alias and attempts
+alias expansion. If it has an alias, \fBbash\fP attempts programmable
+completion using the command word resulting from the expanded alias.
+.TP 8
+.B promptvars
+If set, prompt strings undergo
+parameter expansion, command substitution, arithmetic
+expansion, and quote removal after being expanded as described in
+.SM
+.B PROMPTING
+above.  This option is enabled by default.
+.TP 8
+.B restricted_shell
+The shell sets this option if it is started in restricted mode (see
+.SM
+.B "RESTRICTED SHELL"
+below).
+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.
+.TP 8
+.B shift_verbose
+If set, the
+.B shift
+builtin prints an error message when the shift count exceeds the
+number of positional parameters.
+.TP 8
+.B sourcepath
+If set, the
+\fBsource\fP (\fB.\fP) builtin uses the value of
+.SM
+.B PATH
+to find the directory containing the file supplied as an argument.
+This option is enabled by default.
+.TP 8
+.B xpg_echo
+If set, the \fBecho\fP builtin expands backslash-escape sequences
+by default.
+.RE
+.PD
+.TP
+\fBsuspend\fP [\fB\-f\fP]
+Suspend the execution of this shell until it receives a
+.SM
+.B SIGCONT
+signal.  A login shell cannot be suspended; the
+.B \-f
+option can be used to override this and force the suspension.
+The return status is 0 unless the shell is a login shell and
+.B \-f
+is not supplied, or if job control is not enabled.
+.TP
+\fBtest\fP \fIexpr\fP
+.PD 0
+.TP
+\fB[\fP \fIexpr\fP \fB]\fP
+Return a status of 0 (true) or 1 (false) depending on
+the evaluation of the conditional expression
+.IR expr .
+Each operator and operand must be a separate argument.
+.if \n(zZ=0 Expressions are composed of the primaries described above under
+.if \n(zZ=1 Expressions are composed of the primaries described in the \fBbash\fP manual page under
+.SM
+.BR "CONDITIONAL EXPRESSIONS" .
+\fBtest\fP does not accept any options, nor does it accept and ignore
+an argument of \fB\-\-\fP as signifying the end of options.
+.if t .sp 0.5
+.if n .sp 1
+Expressions may be combined using the following operators, listed
+in decreasing order of precedence.
+The evaluation depends on the number of arguments; see below.
+Operator precedence is used when there are five or more arguments.
+.RS
+.PD 0
+.TP
+.B ! \fIexpr\fP
+True if
+.I expr
+is false.
+.TP
+.B ( \fIexpr\fP )
+Returns the value of \fIexpr\fP.
+This may be used to override the normal precedence of operators.
+.TP
+\fIexpr1\fP \-\fBa\fP \fIexpr2\fP
+True if both
+.I expr1
+and
+.I expr2
+are true.
+.TP
+\fIexpr1\fP \-\fBo\fP \fIexpr2\fP
+True if either
+.I expr1
+or
+.I expr2
+is true.
+.PD
+.PP
+\fBtest\fP and \fB[\fP evaluate conditional
+expressions using a set of rules based on the number of arguments.
+.if t .sp 0.5
+.if n .sp 1
+.PD 0
+.TP
+0 arguments
+The expression is false.
+.TP
+1 argument
+The expression is true if and only if the argument is not null.
+.TP
+2 arguments
+If the first argument is \fB!\fP, the expression is true if and
+only if the second argument is null.
+If the first argument is one of the unary conditional operators listed above
+under
+.SM
+.BR "CONDITIONAL EXPRESSIONS" ,
+the expression is true if the unary test is true.
+If the first argument is not a valid unary conditional operator, the expression
+is false.
+.TP
+3 arguments
+The following conditions are applied in the order listed.
+If the second argument is one of the binary conditional operators listed above
+under
+.SM
+.BR "CONDITIONAL EXPRESSIONS" ,
+the result of the expression is the result of the binary test using
+the first and third arguments as operands.
+The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
+when there are three arguments.
+If the first argument is \fB!\fP, the value is the negation of
+the two-argument test using the second and third arguments.
+If the first argument is exactly \fB(\fP and the third argument is
+exactly \fB)\fP, the result is the one-argument test of the second
+argument.
+Otherwise, the expression is false.
+.TP
+4 arguments
+If the first argument is \fB!\fP, the result is the negation of
+the three-argument expression composed of the remaining arguments.
+Otherwise, the expression is parsed and evaluated according to
+precedence using the rules listed above.
+.TP
+5 or more arguments
+The expression is parsed and evaluated according to precedence
+using the rules listed above.
+.if t .sp 0.5
+.if n .sp 1
+.LP
+When used with \fBtest\fP or \fB[\fP, the \fB<\fP and \fB>\fP operators
+sort lexicographically using ASCII ordering.
+.RE
+.PD
+.TP
+.B times
+Print the accumulated user and system times for the shell and
+for processes run from the shell.  The return status is 0.
+.TP
+\fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
+The command
+.I arg
+is to be read and executed when the shell receives
+signal(s)
+.IR sigspec .
+If
+.I arg
+is absent (and there is a single \fIsigspec\fP) or
+.BR \- ,
+each specified signal is
+reset to its original disposition (the value it had
+upon entrance to the shell).
+If
+.I arg
+is the null string the signal specified by each
+.I sigspec
+is ignored by the shell and by the commands it invokes.
+If
+.I arg
+is not present and
+.B \-p
+has been supplied, then the trap commands associated with each
+.I sigspec
+are displayed.
+If no arguments are supplied or if only
+.B \-p
+is given,
+.B trap
+prints the list of commands associated with each signal.
+The
+.B \-l
+option causes the shell to print a list of signal names and
+their corresponding numbers.
+Each
+.I sigspec
+is either
+a signal name defined in <\fIsignal.h\fP>, or a signal number.
+Signal names are case insensitive and the
+.SM
+.B SIG
+prefix is optional.
+.if t .sp 0.5
+.if n .sp 1
+If a
+.I sigspec
+is
+.SM
+.B EXIT
+(0) the command
+.I arg
+is executed on exit from the shell.
+If a
+.I sigspec
+is
+.SM
+.BR DEBUG ,
+the command
+.I arg
+is executed before every \fIsimple command\fP, \fIfor\fP command,
+\fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
+command, and before the first command executes in a shell function (see
+.SM
+.B SHELL GRAMMAR
+above).
+Refer to the description of the \fBextdebug\fP option to the
+\fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
+If a
+.I sigspec
+is
+.SM
+.BR RETURN ,
+the command
+.I arg
+is executed each time a shell function or a script executed with
+the \fB.\fP or \fBsource\fP builtins finishes executing.
+.if t .sp 0.5
+.if n .sp 1
+If a
+.I sigspec
+is
+.SM
+.BR ERR ,
+the command
+.I arg
+is executed whenever
+a pipeline (which may consist of a single simple
+command), a list, or a compound command returns a
+non\-zero exit status,
+subject to the following conditions.
+The
+.SM
+.B ERR
+trap is not executed if the failed
+command is part of the command list immediately following a
+.B while
+or
+.B until
+keyword,
+part of the test in an
+.I if
+statement, part of a command executed in a
+.B &&
+or
+.B ||
+list except the command following the final \fB&&\fP or \fB||\fP,
+any command in a pipeline but the last,
+or if the command's return value is
+being inverted using
+.BR ! .
+These are the same conditions obeyed by the \fBerrexit\fP (\fB\-e\fP) option.
+.if t .sp 0.5
+.if n .sp 1
+Signals ignored upon entry to the shell cannot be trapped or reset.
+Trapped signals that are not being ignored are reset to their original
+values in a subshell or subshell environment when one is created.
+The return status is false if any
+.I sigspec
+is invalid; otherwise
+.B trap
+returns true.
+.TP
+\fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
+With no options,
+indicate how each
+.I name
+would be interpreted if used as a command name.
+If the
+.B \-t
+option is used,
+.B type
+prints a string which is one of
+.IR alias ,
+.IR keyword ,
+.IR function ,
+.IR builtin ,
+or
+.I file
+if
+.I name
+is an alias, shell reserved word, function, builtin, or disk file,
+respectively.
+If the
+.I name
+is not found, then nothing is printed, and an exit status of false
+is returned.
+If the
+.B \-p
+option is used,
+.B type
+either returns the name of the disk file
+that would be executed if
+.I name
+were specified as a command name,
+or nothing if
+.if t \f(CWtype -t name\fP
+.if n ``type -t name''
+would not return
+.IR file .
+The
+.B \-P
+option forces a
+.SM
+.B PATH
+search for each \fIname\fP, even if
+.if t \f(CWtype -t name\fP
+.if n ``type -t name''
+would not return
+.IR file .
+If a command is hashed,
+.B \-p
+and
+.B \-P
+print the hashed value, which is not necessarily the file that appears
+first in
+.SM
+.BR PATH .
+If the
+.B \-a
+option is used,
+.B type
+prints all of the places that contain
+an executable named
+.IR name .
+This includes aliases and functions,
+if and only if the
+.B \-p
+option is not also used.
+The table of hashed commands is not consulted
+when using
+.BR \-a .
+The
+.B \-f
+option suppresses shell function lookup, as with the \fBcommand\fP builtin.
+.B type
+returns true if all of the arguments are found, false if
+any are not found.
+.TP
+\fBulimit\fP [\fB\-HS\fP] \fB\-a\fP
+.PD 0
+.TP
+\fBulimit\fP [\fB\-HS\fP] [\fB\-bcdefiklmnpqrstuvxPRT\fP [\fIlimit\fP]]
+.PD
+Provides control over the resources available to the shell and to
+processes started by it, on systems that allow such control.
+The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
+set for the given resource.
+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.
+If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
+limits are set.
+The value of
+.I limit
+can be a number in the unit specified for the resource
+or one of the special values
+.BR hard ,
+.BR soft ,
+or
+.BR unlimited ,
+which stand for the current hard limit, the current soft limit, and
+no limit, respectively.
+If
+.I limit
+is omitted, the current value of the soft limit of the resource is
+printed, unless the \fB\-H\fP option is given.  When more than one
+resource is specified, the limit name and unit, if appropriate,
+are printed before the value.
+Other options are interpreted as follows:
+.RS
+.PD 0
+.TP
+.B \-a
+All current limits are reported; no limits are set
+.TP
+.B \-b
+The maximum socket buffer size
+.TP
+.B \-c
+The maximum size of core files created
+.TP
+.B \-d
+The maximum size of a process's data segment
+.TP
+.B \-e
+The maximum scheduling priority ("nice")
+.TP
+.B \-f
+The maximum size of files written by the shell and its children
+.TP
+.B \-i
+The maximum number of pending signals
+.TP
+.B \-k
+The maximum number of kqueues that may be allocated
+.TP
+.B \-l
+The maximum size that may be locked into memory
+.TP
+.B \-m
+The maximum resident set size (many systems do not honor this limit)
+.TP
+.B \-n
+The maximum number of open file descriptors (most systems do not
+allow this value to be set)
+.TP
+.B \-p
+The pipe size in 512-byte blocks (this may not be set)
+.TP
+.B \-q
+The maximum number of bytes in POSIX message queues
+.TP
+.B \-r
+The maximum real-time scheduling priority
+.TP
+.B \-s
+The maximum stack size
+.TP
+.B \-t
+The maximum amount of cpu time in seconds
+.TP
+.B \-u
+The maximum number of processes available to a single user
+.TP
+.B \-v
+The maximum amount of virtual memory available to the shell and, on
+some systems, to its children
+.TP
+.B \-x
+The maximum number of file locks
+.TP
+.B \-P
+The maximum number of pseudoterminals
+.TP
+.B \-R
+The maximum time a real-time process can run before blocking, in microseconds
+.TP
+.B \-T
+The maximum number of threads
+.PD
+.PP
+If
+.I limit
+is given, and the
+.B \-a
+option is not used,
+\fIlimit\fP is the new value of the specified resource.
+If no option is given, then
+.B \-f
+is assumed.  Values are in 1024-byte increments, except for
+.BR \-t ,
+which is in seconds;
+.BR \-R ,
+which is in microseconds;
+.BR \-p ,
+which is in units of 512-byte blocks;
+.BR \-P ,
+.BR \-T ,
+.BR \-b ,
+.BR \-k ,
+.BR \-n ,
+and
+.BR \-u ,
+which are unscaled values;
+and, when in posix mode,
+.B \-c
+and
+.BR \-f ,
+which are in 512-byte increments.
+The return status is 0 unless an invalid option or argument is supplied,
+or an error occurs while setting a new limit.
+.RE
+.TP
+\fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
+The user file-creation mask is set to
+.IR mode .
+If
+.I mode
+begins with a digit, it
+is interpreted as an octal number; otherwise
+it is interpreted as a symbolic mode mask similar
+to that accepted by
+.IR chmod (1).
+If
+.I mode
+is omitted, the current value of the mask is printed.
+The
+.B \-S
+option causes the mask to be printed in symbolic form; the
+default output is an octal number.
+If the
+.B \-p
+option is supplied, and
+.I mode
+is omitted, the output is in a form that may be reused as input.
+The return status is 0 if the mode was successfully changed or if
+no \fImode\fP argument was supplied, and false otherwise.
+.TP
+\fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
+Remove each \fIname\fP from the list of defined aliases.  If
+.B \-a
+is supplied, all alias definitions are removed.  The return
+value is true unless a supplied
+.I name
+is not a defined alias.
+.TP
+\fBunset\fP [\-\fBfv\fP] [\-\fBn\fP] [\fIname\fP ...]
+For each
+.IR name ,
+remove the corresponding variable or function.
+If the
+.B \-v
+option is given, each
+.I name
+refers to a shell variable, and that variable is removed.
+Read-only variables may not be unset.
+If
+.B \-f
+is specified, each
+.I name
+refers to a shell function, and the function definition
+is removed.
+If the
+.B \-n
+option is supplied, and \fIname\fP is a variable with the \fInameref\fP
+attribute, \fIname\fP will be unset rather than the variable it
+references.
+\fB\-n\fP has no effect if the \fB\-f\fP option is supplied.
+If no options are supplied, each \fIname\fP refers to a variable; if
+there is no variable by that name, a function with that name, if any, is
+unset.
+Each unset variable or function is removed from the environment
+passed to subsequent commands.
+If any of
+.SM
+.BR BASH_ALIASES ,
+.SM
+.BR BASH_ARGV0 ,
+.SM
+.BR BASH_CMDS ,
+.SM
+.BR BASH_COMMAND ,
+.SM
+.BR BASH_SUBSHELL ,
+.SM
+.BR BASHPID ,
+.SM
+.BR COMP_WORDBREAKS ,
+.SM
+.BR DIRSTACK ,
+.SM
+.BR EPOCHREALTIME ,
+.SM
+.BR EPOCHSECONDS ,
+.SM
+.BR FUNCNAME ,
+.SM
+.BR GROUPS ,
+.SM
+.BR HISTCMD ,
+.SM
+.BR LINENO ,
+.SM
+.BR RANDOM ,
+.SM
+.BR SECONDS ,
+or
+.SM
+.B SRANDOM
+are unset, they lose their special properties, even if they are
+subsequently reset.  The exit status is true unless a
+.I name
+is readonly.
+.TP
+\fBwait\fP [\fB\-fn\fP] [\fP\-p\fP \fIvarname\fP] [\fIid ...\fP]
+Wait for each specified child process and return its termination status.
+Each
+.I id
+may be a process
+ID or a job specification; if a job spec is given, all processes
+in that job's pipeline are waited for.  If
+.I id
+is not given,
+\fBwait\fP waits for all running background jobs and
+the last-executed process substitution, if its process id is the same as
+\fB$!\fP,
+and the return status is zero.
+If the \fB\-n\fP option is supplied,
+\fBwait\fP waits for a single job
+from the list of \fIid\fPs or, if no \fIid\fPs are supplied, any job,
+to complete and returns its exit status.
+If none of the supplied arguments is a child of the shell, or if no arguments
+are supplied and the shell has no unwaited-for children, the exit status
+is 127.
+If the \fB\-p\fP option is supplied, the process or job identifier of the job
+for which the exit status is returned is assigned to the variable
+\fIvarname\fP named by the option argument.
+The variable will be unset initially, before any assignment.
+This is useful only when the \fB\-n\fP option is supplied.
+Supplying the \fB\-f\fP option, when job control is enabled,
+forces \fBwait\fP to wait for \fIid\fP to terminate before returning
+its status, instead of returning when it changes status.
+If
+.I id
+specifies a non-existent process or job, the return status is
+127.  Otherwise, the return status is the exit status of the last
+process or job waited for.
+.SH "SHELL COMPATIBILITY MODE"
+Bash-4.0 introduced the concept of a `shell compatibility level', specified
+as a set of options to the shopt builtin
+.BR compat31 ,
+.BR compat32 ,
+.BR compat40 ,
+.BR compat41 ,
+and so on).
+There is only one current
+compatibility level -- each option is mutually exclusive.
+The compatibility level is intended to allow users to select behavior
+from previous versions that is incompatible with newer versions
+while they migrate scripts to use current features and
+behavior. It's intended to be a temporary solution.
+.PP
+This section does not mention behavior that is standard for a particular
+version (e.g., setting \fBcompat32\fP means that quoting the rhs of the regexp
+matching operator quotes special regexp characters in the word, which is
+default behavior in bash-3.2 and above). 
+.PP
+If a user enables, say, \fBcompat32\fP, it may affect the behavior of other
+compatibility levels up to and including the current compatibility level.
+The idea is that each compatibility level controls behavior that changed
+in that version of \fBbash\fP,
+but that behavior may have been present in earlier versions.
+For instance, the change to use locale-based comparisons with the \fB[[\fP
+command came in bash-4.1, and earlier versions used ASCII-based comparisons,
+so enabling \fBcompat32\fP will enable ASCII-based comparisons as well.
+That granularity may not be sufficient for
+all uses, and as a result users should employ compatibility levels carefully.
+Read the documentation for a particular feature to find out the
+current behavior.
+.PP
+Bash-4.3 introduced a new shell variable:
+.SM
+.BR BASH_COMPAT .
+The value assigned
+to this variable (a decimal version number like 4.2, or an integer
+corresponding to the \fBcompat\fP\fINN\fP option, like 42) determines the
+compatibility level.
+.PP
+Starting with bash-4.4, Bash has begun deprecating older compatibility
+levels.
+Eventually, the options will be removed in favor of
+.SM
+.BR BASH_COMPAT .
+.PP
+Bash-5.0 is the final version for which there will be an individual shopt
+option for the previous version. Users should use
+.SM
+.B BASH_COMPAT
+on bash-5.0 and later versions.
+.PP
+The following table describes the behavior changes controlled by each
+compatibility level setting.
+The \fBcompat\fP\fINN\fP tag is used as shorthand for setting the
+compatibility level
+to \fINN\fP using one of the following mechanisms.
+For versions prior to bash-5.0, the compatibility level may be set using
+the corresponding \fBcompat\fP\fINN\fP shopt option.
+For bash-4.3 and later versions, the
+.SM
+.B BASH_COMPAT
+variable is preferred,
+and it is required for bash-5.1 and later versions.
+.TP
+\fBcompat31\fP
+.PD 0
+.RS
+.IP \(bu
+quoting the rhs of the \fB[[\fP command's regexp matching operator (=~)
+has no special effect
+.RE
+.PD
+.TP
+\fBcompat32\fP
+.PD 0
+.RS
+.IP \(bu
+interrupting a command list such as "a ; b ; c" causes the execution
+of the next command in the list (in bash-4.0 and later versions,
+the shell acts as if it received the interrupt, so
+interrupting one command in a list aborts the execution of the
+entire list)
+.RE
+.PD
+.TP
+\fBcompat40\fP
+.PD 0
+.RS
+.IP \(bu
+the \fB<\fP and \fB>\fP operators to the \fB[[\fP command do not
+consider the current locale when comparing strings; they use ASCII
+ordering.
+Bash versions prior to bash-4.1 use ASCII collation and
+.IR strcmp (3);
+bash-4.1 and later use the current locale's collation sequence and
+.IR strcoll (3).
+.RE
+.PD
+.TP
+\fBcompat41\fP
+.PD 0
+.RS
+.IP \(bu
+in \fIposix\fP mode, \fBtime\fP may be followed by options and still be
+recognized as a reserved word (this is POSIX interpretation 267)
+.IP \(bu
+in \fIposix\fP mode, the parser requires that an even number of single
+quotes occur in the \fIword\fP portion of a double-quoted
+parameter expansion and treats them specially, so that characters within
+the single quotes are considered quoted
+(this is POSIX interpretation 221)
+.RE
+.PD
+.TP
+\fBcompat42\fP
+.PD 0
+.RS
+.IP \(bu
+the replacement string in double-quoted pattern substitution does not
+undergo quote removal, as it does in versions after bash-4.2
+.IP \(bu
+in posix mode, single quotes are considered special when expanding
+the \fIword\fP portion of a double-quoted parameter expansion
+and can be used to quote a closing brace or other special character
+(this is part of POSIX interpretation 221);
+in later versions, single quotes
+are not special within double-quoted word expansions
+.RE
+.PD
+.TP
+\fBcompat43\fP
+.PD 0
+.RS
+.IP \(bu
+the shell does not print a warning message if an attempt is made to
+use a quoted compound assignment as an argument to declare
+(declare -a foo='(1 2)'). Later versions warn that this usage is
+deprecated
+.IP \(bu
+word expansion errors are considered non-fatal errors that cause the
+current command to fail, even in posix mode
+(the default behavior is to make them fatal errors that cause the shell
+to exit)
+.IP \(bu
+when executing a shell function, the loop state (while/until/etc.)
+is not reset, so \fBbreak\fP or \fBcontinue\fP in that function will break
+or continue loops in the calling context. Bash-4.4 and later reset
+the loop state to prevent this
+.RE
+.PD
+.TP
+\fBcompat44\fP
+.PD 0
+.RS
+.IP \(bu
+the shell sets up the values used by
+.SM
+.B BASH_ARGV
+and
+.SM
+.B BASH_ARGC
+so they can expand to the shell's positional parameters even if extended
+debugging mode is not enabled
+.IP \(bu
+a subshell inherits loops from its parent context, so \fBbreak\fP
+or \fBcontinue\fP will cause the subshell to exit.
+Bash-5.0 and later reset the loop state to prevent the exit
+.IP \(bu
+variable assignments preceding builtins like \fBexport\fP and \fBreadonly\fP
+that set attributes continue to affect variables with the same
+name in the calling environment even if the shell is not in posix
+mode
+.RE
+.PD
+.TP
+\fBcompat50\fP
+.PD 0
+.RS
+.IP \(bu
+Bash-5.1 changed the way
+.SM
+.B $RANDOM
+is generated to introduce slightly
+more randomness. If the shell compatibility level is set to 50 or
+lower, it reverts to the method from bash-5.0 and previous versions,
+so seeding the random number generator by assigning a value to
+.SM
+.B RANDOM
+will produce the same sequence as in bash-5.0
+.IP \(bu
+If the command hash table is empty, bash versions prior to bash-5.1
+printed an informational message to that effect, even when producing
+output that can be reused as input. Bash-5.1 suppresses that message
+when the \fB\-l\fP option is supplied.
+.RE
+.PD
+.\" bash_builtins
+.if \n(zZ=1 .ig zZ
+.SH "RESTRICTED SHELL"
+.\" rbash.1
+.zY
+.PP
+If
+.B bash
+is started with the name
+.BR rbash ,
+or the
+.B \-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.
+It behaves identically to
+.B bash
+with the exception that the following are disallowed or not performed:
+.IP \(bu
+changing directories with \fBcd\fP
+.IP \(bu
+setting or unsetting the values of
+.SM
+.BR SHELL ,
+.SM
+.BR PATH ,
+.SM
+.BR HISTFILE ,
+.SM
+.BR ENV ,
+or
+.SM
+.B BASH_ENV
+.IP \(bu
+specifying command names containing
+.B /
+.IP \(bu
+specifying a filename containing a
+.B /
+as an argument to the
+.B .
+builtin command
+.IP \(bu
+specifying a filename containing a slash as an argument to the
+.B history
+builtin command
+.IP \(bu
+specifying a filename containing a slash as an argument to the
+.B \-p
+option to the
+.B hash
+builtin command
+.IP \(bu
+importing function definitions from the shell environment at startup
+.IP \(bu
+parsing the value of
+.SM
+.B SHELLOPTS
+from the shell environment at startup
+.IP \(bu
+redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
+.IP \(bu
+using the
+.B exec
+builtin command to replace the shell with another command
+.IP \(bu
+adding or deleting builtin commands with the
+.B \-f
+and
+.B \-d
+options to the
+.B enable
+builtin command
+.IP \(bu
+using the \fBenable\fP builtin command to enable disabled shell builtins
+.IP \(bu
+specifying the
+.B \-p
+option to the
+.B command
+builtin command
+.IP \(bu
+turning off restricted mode with
+\fBset +r\fP or \fBset +o restricted\fP.
+.PP
+These restrictions are enforced after any startup files are read.
+.PP
+.ie \n(zY=1 When a command that is found to be a shell script is executed,
+.el \{ When a command that is found to be a shell script is executed
+(see
+.SM
+.B "COMMAND EXECUTION"
+above),
+\}
+.B rbash
+turns off any restrictions in the shell spawned to execute the
+script.
+.\" end of rbash.1
+.if \n(zY=1 .ig zY
+.SH "SEE ALSO"
+.PD 0
+.TP
+\fIBash Reference Manual\fP, Brian Fox and Chet Ramey
+.TP
+\fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
+.TP
+\fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
+.TP
+\fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE --
+http://pubs.opengroup.org/onlinepubs/9699919799/
+.TP
+http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
+.TP
+\fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
+.TP
+\fIemacs\fP(1), \fIvi\fP(1)
+.TP
+\fIreadline\fP(3)
+.PD
+.SH FILES
+.PD 0
+.TP
+.FN /bin/bash
+The \fBbash\fP executable
+.TP
+.FN /etc/profile
+The systemwide initialization file, executed for login shells
+.TP
+.FN ~/.bash_profile
+The personal initialization file, executed for login shells
+.TP
+.FN ~/.bashrc
+The individual per-interactive-shell startup file
+.TP
+.FN ~/.bash_logout
+The individual login shell cleanup file, executed when a login shell exits
+.TP
+.FN ~/.inputrc
+Individual \fIreadline\fP initialization file
+.PD
+.SH AUTHORS
+Brian Fox, Free Software Foundation
+.br
+bfox@gnu.org
+.PP
+Chet Ramey, Case Western Reserve University
+.br
+chet.ramey@case.edu
+.SH BUG REPORTS
+If you find a bug in
+.B bash,
+you should report it.  But first, you should
+make sure that it really is a bug, and that it appears in the latest
+version of
+.BR bash .
+The latest version is always available from
+\fIftp://ftp.gnu.org/pub/gnu/bash/\fP.
+.PP
+Once you have determined that a bug actually exists, use the
+.I bashbug
+command to submit a bug report.
+If you have a fix, you are encouraged to mail that as well!
+Suggestions and `philosophical' bug reports may be mailed
+to \fIbug-bash@gnu.org\fP or posted to the Usenet
+newsgroup
+.BR gnu.bash.bug .
+.PP
+ALL bug reports should include:
+.PP
+.PD 0
+.TP 20
+The version number of \fBbash\fR
+.TP
+The hardware and operating system
+.TP
+The compiler used to compile
+.TP
+A description of the bug behaviour
+.TP
+A short script or `recipe' which exercises the bug
+.PD
+.PP
+.I bashbug
+inserts the first three items automatically into the template
+it provides for filing a bug report.
+.PP
+Comments and bug reports concerning
+this manual page should be directed to
+.IR chet.ramey@case.edu .
+.SH BUGS
+It's too big and too slow.
+.PP
+There are some subtle differences between
+.B bash
+and traditional versions of
+.BR sh ,
+mostly because of the
+.SM
+.B POSIX
+specification.
+.PP
+Aliases are confusing in some uses.
+.PP
+Shell builtin commands and functions are not stoppable/restartable.
+.PP
+Compound commands and command sequences of the form `a ; b ; c'
+are not handled gracefully when process suspension is attempted.
+When a process is stopped, the shell immediately executes the next
+command in the sequence.
+It suffices to place the sequence of commands between
+parentheses to force it into a subshell, which may be stopped as
+a unit.
+.PP
+Array variables may not (yet) be exported.
+.PP
+There may be only one active coprocess at a time.
+.zZ
+.zY