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.\" MAN PAGE COMMENTS to
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.\" Case Western Reserve University
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.\" chet.ramey@case.edu
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.\" Last Change: Sun Feb 2 16:21:40 EST 2014
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.\" bash_builtins, strip all but Built-Ins section
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.TH BASH 1 "2014 February 2" "GNU Bash 4.3"
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.\" There's some problem with having a `@'
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.\" in a tagged paragraph with the BSD man macros.
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.\" It has to do with `@' appearing in the }1 macro.
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.\" This is a problem on 4.3 BSD and Ultrix, but Sun
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.\" appears to have fixed it.
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.\" If you're seeing the characters
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.\" `@u-3p' appearing before the lines reading
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.\" `possible-hostname-completions
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.\" and `complete-hostname' down in READLINE,
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.\" then uncomment this redefinition.
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.if !"\\$1"" .nr )I \\$1n
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.in \\n()Ru+\\n(INu+\\n()Iu
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.ie !\\n()Iu+\\n()Ru-\w\\*(]Xu-3p \{\\*(]X
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.el \\*(]X\h|\\n()Iu+\\n()Ru\c
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.\" File Name macro. This used to be `.PN', for Path Name,
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.\" but Sun doesn't seem to like that very much.
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bash \- GNU Bourne-Again SHell
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[command_string | file]
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.if n Bash is Copyright (C) 1989-2013 by the Free Software Foundation, Inc.
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.if t Bash is Copyright \(co 1989-2013 by the Free Software Foundation, Inc.
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is an \fBsh\fR-compatible command language interpreter that
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executes commands read from the standard input or from a file.
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also incorporates useful features from the \fIKorn\fP and \fIC\fP
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shells (\fBksh\fP and \fBcsh\fP).
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is intended to be a conformant implementation of the
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Shell and Utilities portion of the IEEE POSIX specification
66
(IEEE Standard 1003.1).
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can be configured to be POSIX-conformant by default.
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All of the single-character shell options documented in the
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description of the \fBset\fR builtin command can be used as options
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when the shell is invoked.
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In addition, \fBbash\fR
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interprets the following options when it is invoked:
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option is present, then commands are read from the first non-option argument
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If there are arguments after the
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they are assigned to the positional parameters, starting with
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option is present, the shell is
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act as if it had been invoked as a login shell (see
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option is present, the shell becomes
109
.B "RESTRICTED SHELL"
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option is present, or if no arguments remain after option
116
processing, then commands are read from the standard input.
117
This option allows the positional parameters to be set
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when invoking an interactive shell.
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A list of all double-quoted strings preceded by \fB$\fP
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is printed on the standard output.
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These are the strings that
124
are subject to language translation when the current locale
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is not \fBC\fP or \fBPOSIX\fP.
126
This implies the \fB\-n\fP option; no commands will be executed.
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.B [\-+]O [\fIshopt_option\fP]
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\fIshopt_option\fP is one of the shell options accepted by the
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\fBshopt\fP builtin (see
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.B SHELL BUILTIN COMMANDS
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If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
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If \fIshopt_option\fP is not supplied, the names and values of the shell
137
options accepted by \fBshopt\fP are printed on the standard output.
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If the invocation option is \fB+O\fP, the output is displayed in a format
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that may be reused as input.
144
signals the end of options and disables further option processing.
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Any arguments after the
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are treated as filenames and arguments. An argument of
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is equivalent to \fB\-\-\fP.
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also interprets a number of multi-character options.
154
These options must appear on the command line before the
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single-character options to be recognized.
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Arrange for the debugger profile to be executed before the shell
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Turns on extended debugging mode (see the description of the
168
.B \-\-dump\-po\-strings
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Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
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\fBpo\fP (portable object) file format.
173
Equivalent to \fB\-D\fP.
176
Display a usage message on standard output and exit successfully.
178
\fB\-\-init\-file\fP \fIfile\fP
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\fB\-\-rcfile\fP \fIfile\fP
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Execute commands from
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instead of the standard personal initialization file
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if the shell is interactive (see
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Equivalent to \fB\-l\fP.
198
library to read command lines when the shell is interactive.
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Do not read either the system-wide startup file
203
or any of the personal initialization files
204
.IR ~/.bash_profile ,
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reads these files when it is invoked as a login shell (see
216
Do not read and execute the personal initialization file
218
if the shell is interactive.
219
This option is on by default if the shell is invoked as
223
Change the behavior of \fBbash\fP where the default operation differs
224
from the POSIX standard to match the standard (\fIposix mode\fP).
228
below for a reference to a document that details how posix mode affects
232
The shell becomes restricted (see
234
.B "RESTRICTED SHELL"
238
Equivalent to \fB\-v\fP.
241
Show version information for this instance of
243
on the standard output and exit successfully.
246
If arguments remain after option processing, and neither the
250
option has been supplied, the first argument is assumed to
251
be the name of a file containing shell commands.
254
is invoked in this fashion,
256
is set to the name of the file, and the positional parameters
257
are set to the remaining arguments.
259
reads and executes commands from this file, then exits.
260
\fBBash\fP's exit status is the exit status of the last command
261
executed in the script.
262
If no commands are executed, the exit status is 0.
263
An attempt is first made to open the file in the current directory, and,
264
if no file is found, then the shell searches the directories in
269
A \fIlogin shell\fP is one whose first character of argument zero is a
271
or one started with the
275
An \fIinteractive\fP shell is one started without non-option arguments
279
whose standard input and error are
280
both connected to terminals (as determined by
282
or one started with the
294
allowing a shell script or a startup file to test this state.
296
The following paragraphs describe how
298
executes its startup files.
299
If any of the files exist but cannot be read,
302
Tildes are expanded in filenames as described below under
311
is invoked as an interactive login shell, or as a non-interactive shell
312
with the \fB\-\-login\fP option, it first reads and
313
executes commands from the file \fI/etc/profile\fP, if that
315
After reading that file, it looks for \fI~/.bash_profile\fP,
316
\fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
317
and executes commands from the first one that exists and is readable.
320
option may be used when the shell is started to inhibit this behavior.
322
When a login shell exits,
324
reads and executes commands from the file \fI~/.bash_logout\fP, if it
327
When an interactive shell that is not a login shell is started,
329
reads and executes commands from \fI~/.bashrc\fP, if that file exists.
330
This may be inhibited by using the
333
The \fB\-\-rcfile\fP \fIfile\fP option will force
335
to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
339
is started non-interactively, to run a shell script, for example, it
340
looks for the variable
343
in the environment, expands its value if it appears there, and uses the
344
expanded value as the name of a file to read and execute.
346
behaves as if the following command were executed:
349
.if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
350
.if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
356
variable is not used to search for the filename.
360
is invoked with the name
362
it tries to mimic the startup behavior of historical versions of
364
as closely as possible,
365
while conforming to the POSIX standard as well.
366
When invoked as an interactive login shell, or a non-interactive
367
shell with the \fB\-\-login\fP option, it first attempts to
368
read and execute commands from
375
option may be used to inhibit this behavior.
376
When invoked as an interactive shell with the name
379
looks for the variable
382
expands its value if it is defined, and uses the
383
expanded value as the name of a file to read and execute.
384
Since a shell invoked as
386
does not attempt to read and execute commands from any other startup
389
option has no effect.
390
A non-interactive shell invoked with the name
392
does not attempt to read any other startup files.
398
mode after the startup files are read.
406
command line option, it follows the POSIX standard for startup files.
407
In this mode, interactive shells expand the
410
variable and commands are read and executed from the file
411
whose name is the expanded value.
412
No other startup files are read.
415
attempts to determine when it is being run with its standard input
416
connected to a network connection, as when executed by the remote shell
417
daemon, usually \fIrshd\fP, or the secure shell daemon \fIsshd\fP.
420
determines it is being run in this fashion, it reads and executes
421
commands from \fI~/.bashrc\fP, if that file exists and is readable.
422
It will not do this if invoked as \fBsh\fP.
425
option may be used to inhibit this behavior, and the
427
option may be used to force another file to be read, but neither
428
\fIrshd\fP nor \fIsshd\fP generally invoke the shell with those options
429
or allow them to be specified.
431
If the shell is started with the effective user (group) id not equal to the
432
real user (group) id, and the \fB\-p\fP option is not supplied, no startup
433
files are read, shell functions are not inherited from the environment, the
443
variables, if they appear in the environment, are ignored,
444
and the effective user id is set to the real user id.
445
If the \fB\-p\fP option is supplied at invocation, the startup behavior is
446
the same, but the effective user id is not reset.
449
The following definitions are used throughout the rest of this
457
A sequence of characters considered as a single unit by the shell.
464
consisting only of alphanumeric characters and underscores, and
465
beginning with an alphabetic character or an underscore. Also
470
A character that, when unquoted, separates words. One of the following:
474
.if t \fB| & ; ( ) < > space tab\fP
475
.if n \fB| & ; ( ) < > space tab\fP
480
A \fItoken\fP that performs a control function. It is one of the following
484
.if t \fB|| & && ; ;; ( ) | |& <newline>\fP
485
.if n \fB|| & && ; ;; ( ) | |& <newline>\fP
489
\fIReserved words\fP are words that have a special meaning to the shell.
490
The following words are recognized as reserved when unquoted and either
491
the first word of a simple command (see
494
below) or the third word of a
502
.if n ! case coproc do done elif else esac fi for function if in select then until while { } time [[ ]]
503
.if t ! case coproc do done elif else esac fi for function if in select then until while { } time [[ ]]
508
A \fIsimple command\fP is a sequence of optional variable assignments
509
followed by \fBblank\fP-separated words and redirections, and
510
terminated by a \fIcontrol operator\fP. The first word
511
specifies the command to be executed, and is passed as argument zero.
512
The remaining words are passed as arguments to the invoked command.
514
The return value of a \fIsimple command\fP is its exit status, or
515
128+\fIn\^\fP if the command is terminated by signal
519
A \fIpipeline\fP is a sequence of one or more commands separated by
520
one of the control operators
523
The format for a pipeline is:
526
[\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ [\fB|\fP\(bv\fB|&\fP] \fIcommand2\fP ... ]
529
The standard output of
531
is connected via a pipe to the standard input of
533
This connection is performed before any redirections specified by the
538
If \fB|&\fP is used, \fIcommand\fP's standard error, in addition to its
539
standard output, is connected to
540
\fIcommand2\fP's standard input through the pipe;
541
it is shorthand for \fB2>&1 |\fP.
542
This implicit redirection of the standard error to the standard output is
543
performed after any redirections specified by the command.
545
The return status of a pipeline is the exit status of the last
546
command, unless the \fBpipefail\fP option is enabled.
547
If \fBpipefail\fP is enabled, the pipeline's return status is the
548
value of the last (rightmost) command to exit with a non-zero status,
549
or zero if all commands exit successfully.
552
precedes a pipeline, the exit status of that pipeline is the logical
553
negation of the exit status as described above.
554
The shell waits for all commands in the pipeline to
555
terminate before returning a value.
559
reserved word precedes a pipeline, the elapsed as well as user and
560
system time consumed by its execution are reported when the pipeline
562
The \fB\-p\fP option changes the output format to that specified by POSIX.
563
When the shell is in \fIposix mode\fP, it does not recognize
564
\fBtime\fP as a reserved word if the next token begins with a `-'.
568
variable may be set to a format string that specifies how the timing
569
information should be displayed; see the description of
576
When the shell is in \fIposix mode\fP, \fBtime\fP
577
may be followed by a newline. In this case, the shell displays the
578
total user and system time consumed by the shell and its children.
582
variable may be used to specify the format of
583
the time information.
585
Each command in a pipeline is executed as a separate process (i.e., in a
589
A \fIlist\fP is a sequence of one or more pipelines separated by one
596
and optionally terminated by one of
602
Of these list operators,
606
have equal precedence, followed by
610
which have equal precedence.
612
A sequence of one or more newlines may appear in a \fIlist\fP instead
613
of a semicolon to delimit commands.
615
If a command is terminated by the control operator
617
the shell executes the command in the \fIbackground\fP
618
in a subshell. The shell does not wait for the command to
619
finish, and the return status is 0. Commands separated by a
621
are executed sequentially; the shell waits for each
622
command to terminate in turn. The return status is the
623
exit status of the last command executed.
625
AND and OR lists are sequences of one of more pipelines separated by the
626
\fB&&\fP and \fB||\fP control operators, respectively.
627
AND and OR lists are executed with left associativity.
628
An AND list has the form
631
\fIcommand1\fP \fB&&\fP \fIcommand2\fP
635
is executed if, and only if,
637
returns an exit status of zero.
639
An OR list has the form
642
\fIcommand1\fP \fB||\fP \fIcommand2\fP
647
is executed if and only if
649
returns a non-zero exit status.
651
AND and OR lists is the exit status of the last command
652
executed in the list.
653
.SS Compound Commands
655
A \fIcompound command\fP is one of the following.
656
In most cases a \fIlist\fP in a command's description may be separated from
657
the rest of the command by one or more newlines, and may be followed by a
658
newline in place of a semicolon.
661
\fIlist\fP is executed in a subshell environment (see
663
\fBCOMMAND EXECUTION ENVIRONMENT\fP
665
Variable assignments and builtin
666
commands that affect the shell's environment do not remain in effect
667
after the command completes. The return status is the exit status of
671
\fIlist\fP is simply executed in the current shell environment.
672
\fIlist\fP must be terminated with a newline or semicolon.
673
This is known as a \fIgroup command\fP.
674
The return status is the exit status of
676
Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
677
\fB}\fP are \fIreserved words\fP and must occur where a reserved
678
word is permitted to be recognized. Since they do not cause a word
679
break, they must be separated from \fIlist\fP by whitespace or another
683
The \fIexpression\fP is evaluated according to the rules described
686
.BR "ARITHMETIC EVALUATION" .
687
If the value of the expression is non-zero, the return status is 0;
688
otherwise the return status is 1. This is exactly equivalent to
689
\fBlet "\fIexpression\fP"\fR.
691
\fB[[\fP \fIexpression\fP \fB]]\fP
692
Return a status of 0 or 1 depending on the evaluation of
693
the conditional expression \fIexpression\fP.
694
Expressions are composed of the primaries described below under
696
.BR "CONDITIONAL EXPRESSIONS" .
697
Word splitting and pathname expansion are not performed on the words
698
between the \fB[[\fP and \fB]]\fP; tilde expansion,
699
parameter and variable expansion,
700
arithmetic expansion, command substitution, process
701
substitution, and quote removal are performed.
702
Conditional operators such as \fB\-f\fP must be unquoted to be recognized
706
When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
707
lexicographically using the current locale.
710
When the \fB==\fP and \fB!=\fP operators are used, the string to the
711
right of the operator is considered a pattern and matched according
712
to the rules described below under \fBPattern Matching\fP,
713
as if the \fBextglob\fP shell option were enabled.
714
The \fB=\fP operator is equivalent to \fB==\fP.
717
is enabled, the match is performed without regard to the case
718
of alphabetic characters.
719
The return value is 0 if the string matches (\fB==\fP) or does not match
720
(\fB!=\fP) the pattern, and 1 otherwise.
721
Any part of the pattern may be quoted to force the quoted portion
722
to be matched as a string.
725
An additional binary operator, \fB=~\fP, is available, with the same
726
precedence as \fB==\fP and \fB!=\fP.
727
When it is used, the string to the right of the operator is considered
728
an extended regular expression and matched accordingly (as in \fIregex\fP(3)).
729
The return value is 0 if the string matches
730
the pattern, and 1 otherwise.
731
If the regular expression is syntactically incorrect, the conditional
732
expression's return value is 2.
735
is enabled, the match is performed without regard to the case
736
of alphabetic characters.
737
Any part of the pattern may be quoted to force the quoted portion
738
to be matched as a string.
739
Bracket expressions in regular expressions must be treated carefully,
740
since normal quoting characters lose their meanings between brackets.
741
If the pattern is stored in a shell variable, quoting the variable
742
expansion forces the entire pattern to be matched as a string.
743
Substrings matched by parenthesized subexpressions within the regular
744
expression are saved in the array variable
750
with index 0 is the portion of the string
751
matching the entire regular expression.
755
with index \fIn\fP is the portion of the
756
string matching the \fIn\fPth parenthesized subexpression.
759
Expressions may be combined using the following operators, listed
760
in decreasing order of precedence:
766
.B ( \fIexpression\fP )
767
Returns the value of \fIexpression\fP.
768
This may be used to override the normal precedence of operators.
770
.B ! \fIexpression\fP
775
\fIexpression1\fP \fB&&\fP \fIexpression2\fP
782
\fIexpression1\fP \fB||\fP \fIexpression2\fP
790
The \fB&&\fP and \fB||\fP
791
operators do not evaluate \fIexpression2\fP if the value of
792
\fIexpression1\fP is sufficient to determine the return value of
793
the entire conditional expression.
796
\fBfor\fP \fIname\fP [ [ \fBin\fP [ \fIword ...\fP ] ] ; ] \fBdo\fP \fIlist\fP ; \fBdone\fP
797
The list of words following \fBin\fP is expanded, generating a list
799
The variable \fIname\fP is set to each element of this list
800
in turn, and \fIlist\fP is executed each time.
801
If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
802
\fIlist\fP once for each positional parameter that is set (see
806
The return status is the exit status of the last command that executes.
807
If the expansion of the items following \fBin\fP results in an empty
808
list, no commands are executed, and the return status is 0.
810
\fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
811
First, the arithmetic expression \fIexpr1\fP is evaluated according
812
to the rules described below under
814
.BR "ARITHMETIC EVALUATION" .
815
The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
816
until it evaluates to zero.
817
Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
818
executed and the arithmetic expression \fIexpr3\fP is evaluated.
819
If any expression is omitted, it behaves as if it evaluates to 1.
820
The return value is the exit status of the last command in \fIlist\fP
821
that is executed, or false if any of the expressions is invalid.
823
\fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
824
The list of words following \fBin\fP is expanded, generating a list
825
of items. The set of expanded words is printed on the standard
826
error, each preceded by a number. If the \fBin\fP
827
\fIword\fP is omitted, the positional parameters are printed (see
833
prompt is then displayed and a line read from the standard input.
834
If the line consists of a number corresponding to one of
835
the displayed words, then the value of
837
is set to that word. If the line is empty, the words and prompt
838
are displayed again. If EOF is read, the command completes. Any
839
other value read causes
841
to be set to null. The line read is saved in the variable
846
is executed after each selection until a
851
is the exit status of the last command executed in
853
or zero if no commands were executed.
855
\fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
856
... ) \fIlist\fP ;; ] ... \fBesac\fP
857
A \fBcase\fP command first expands \fIword\fP, and tries to match
858
it against each \fIpattern\fP in turn, using the same matching rules
859
as for pathname expansion (see
860
.B Pathname Expansion
862
The \fIword\fP is expanded using tilde
863
expansion, parameter and variable expansion, arithmetic substitution,
864
command substitution, process substitution and quote removal.
865
Each \fIpattern\fP examined is expanded using tilde
866
expansion, parameter and variable expansion, arithmetic substitution,
867
command substitution, and process substitution.
870
is enabled, the match is performed without regard to the case
871
of alphabetic characters.
872
When a match is found, the corresponding \fIlist\fP is executed.
873
If the \fB;;\fP operator is used, no subsequent matches are attempted after
874
the first pattern match.
875
Using \fB;&\fP in place of \fB;;\fP causes execution to continue with
876
the \fIlist\fP associated with the next set of patterns.
877
Using \fB;;&\fP in place of \fB;;\fP causes the shell to test the next
878
pattern list in the statement, if any, and execute any associated \fIlist\fP
879
on a successful match.
880
The exit status is zero if no
881
pattern matches. Otherwise, it is the exit status of the
882
last command executed in \fIlist\fP.
884
\fBif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; \
885
[ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
886
[ \fBelse\fP \fIlist\fP; ] \fBfi\fP
890
is executed. If its exit status is zero, the
891
\fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
892
\fIlist\fP is executed in turn, and if its exit status is zero,
893
the corresponding \fBthen\fP \fIlist\fP is executed and the
894
command completes. Otherwise, the \fBelse\fP \fIlist\fP is
895
executed, if present. The exit status is the exit status of the
896
last command executed, or zero if no condition tested true.
898
\fBwhile\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
901
\fBuntil\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
903
The \fBwhile\fP command continuously executes the list
904
\fIlist-2\fP as long as the last command in the list \fIlist-1\fP returns
905
an exit status of zero. The \fBuntil\fP command is identical
906
to the \fBwhile\fP command, except that the test is negated;
908
is executed as long as the last command in
910
returns a non-zero exit status.
911
The exit status of the \fBwhile\fP and \fBuntil\fP commands
913
of the last command executed in \fIlist-2\fP, or zero if
917
A \fIcoprocess\fP is a shell command preceded by the \fBcoproc\fP reserved
919
A coprocess is executed asynchronously in a subshell, as if the command
920
had been terminated with the \fB&\fP control operator, with a two-way pipe
921
established between the executing shell and the coprocess.
923
The format for a coprocess is:
926
\fBcoproc\fP [\fINAME\fP] \fIcommand\fP [\fIredirections\fP]
929
This creates a coprocess named \fINAME\fP.
930
If \fINAME\fP is not supplied, the default name is \fBCOPROC\fP.
931
\fINAME\fP must not be supplied if \fIcommand\fP is a \fIsimple
932
command\fP (see above); otherwise, it is interpreted as the first word
933
of the simple command.
934
When the coprocess is executed, the shell creates an array variable (see
936
below) named \fINAME\fP in the context of the executing shell.
937
The standard output of
939
is connected via a pipe to a file descriptor in the executing shell,
940
and that file descriptor is assigned to \fINAME\fP[0].
941
The standard input of
943
is connected via a pipe to a file descriptor in the executing shell,
944
and that file descriptor is assigned to \fINAME\fP[1].
945
This pipe is established before any redirections specified by the
950
The file descriptors can be utilized as arguments to shell commands
951
and redirections using standard word expansions.
952
The file descriptors are not available in subshells.
953
The process ID of the shell spawned to execute the coprocess is
954
available as the value of the variable \fINAME\fP_PID.
956
builtin command may be used to wait for the coprocess to terminate.
958
Since the coprocess is created as an asynchronous command,
959
the \fBcoproc\fP command always returns success.
960
The return status of a coprocess is the exit status of \fIcommand\fP.
961
.SS Shell Function Definitions
963
A shell function is an object that is called like a simple command and
964
executes a compound command with a new set of positional parameters.
965
Shell functions are declared as follows:
967
\fIname\fP () \fIcompound\-command\fP [\fIredirection\fP]
970
\fBfunction\fP \fIname\fP [()] \fIcompound\-command\fP [\fIredirection\fP]
972
This defines a function named \fIname\fP.
973
The reserved word \fBfunction\fP is optional.
974
If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
975
The \fIbody\fP of the function is the compound command
977
(see \fBCompound Commands\fP above).
978
That command is usually a \fIlist\fP of commands between { and }, but
979
may be any command listed under \fBCompound Commands\fP above.
980
\fIcompound\-command\fP is executed whenever \fIname\fP is specified as the
981
name of a simple command.
982
When in \fIposix mode\fP, \fIname\fP may not be the name of one of the
983
POSIX \fIspecial builtins\fP.
984
Any redirections (see
987
below) specified when a function is defined are performed
988
when the function is executed.
989
The exit status of a function definition is zero unless a syntax error
990
occurs or a readonly function with the same name already exists.
991
When executed, the exit status of a function is the exit status of the
992
last command executed in the body. (See
997
In a non-interactive shell, or an interactive shell in which the
998
.B interactive_comments
1001
builtin is enabled (see
1003
.B "SHELL BUILTIN COMMANDS"
1004
below), a word beginning with
1006
causes that word and all remaining characters on that line to
1007
be ignored. An interactive shell without the
1008
.B interactive_comments
1009
option enabled does not allow comments. The
1010
.B interactive_comments
1011
option is on by default in interactive shells.
1013
\fIQuoting\fP is used to remove the special meaning of certain
1014
characters or words to the shell. Quoting can be used to
1015
disable special treatment for special characters, to prevent
1016
reserved words from being recognized as such, and to prevent
1017
parameter expansion.
1019
Each of the \fImetacharacters\fP listed above under
1022
has special meaning to the shell and must be quoted if it is to
1025
When the command history expansion facilities are being used
1028
.B HISTORY EXPANSION
1030
\fIhistory expansion\fP character, usually \fB!\fP, must be quoted
1031
to prevent history expansion.
1033
There are three quoting mechanisms: the
1034
.IR "escape character" ,
1035
single quotes, and double quotes.
1037
A non-quoted backslash (\fB\e\fP) is the
1038
.IR "escape character" .
1039
It preserves the literal value of the next character that follows,
1040
with the exception of <newline>. If a \fB\e\fP<newline> pair
1041
appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
1042
is treated as a line continuation (that is, it is removed from the
1043
input stream and effectively ignored).
1045
Enclosing characters in single quotes preserves the literal value
1046
of each character within the quotes. A single quote may not occur
1047
between single quotes, even when preceded by a backslash.
1049
Enclosing characters in double quotes preserves the literal value
1050
of all characters within the quotes, with the exception of
1054
and, when history expansion is enabled,
1060
retain their special meaning within double quotes. The backslash
1061
retains its special meaning only when followed by one of the following
1069
A double quote may be quoted within double quotes by preceding it with
1071
If enabled, history expansion will be performed unless an
1073
appearing in double quotes is escaped using a backslash.
1074
The backslash preceding the
1078
The special parameters
1082
have special meaning when in double
1088
Words of the form \fB$\fP\(aq\fIstring\fP\(aq are treated specially. The
1089
word expands to \fIstring\fP, with backslash-escaped characters replaced
1090
as specified by the ANSI C standard. Backslash escape sequences, if
1091
present, are decoded as follows:
1131
the eight-bit character whose value is the octal value \fInnn\fP
1132
(one to three digits)
1135
the eight-bit character whose value is the hexadecimal value \fIHH\fP
1136
(one or two hex digits)
1139
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
1140
\fIHHHH\fP (one to four hex digits)
1142
.B \eU\fIHHHHHHHH\fP
1143
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
1144
\fIHHHHHHHH\fP (one to eight hex digits)
1147
a control-\fIx\fP character
1151
The expanded result is single-quoted, as if the dollar sign had
1154
A double-quoted string preceded by a dollar sign (\fB$\fP\(dq\fIstring\fP\(dq)
1155
will cause the string to be translated according to the current locale.
1156
If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
1158
If the string is translated and replaced, the replacement is
1163
is an entity that stores values.
1166
a number, or one of the special characters listed below under
1167
.BR "Special Parameters" .
1170
is a parameter denoted by a
1172
A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
1173
Attributes are assigned using the
1175
builtin command (see
1179
.BR "SHELL BUILTIN COMMANDS" ).
1181
A parameter is set if it has been assigned a value. The null string is
1182
a valid value. Once a variable is set, it may be unset only by using
1185
builtin command (see
1187
.B SHELL BUILTIN COMMANDS
1192
may be assigned to by a statement of the form
1195
\fIname\fP=[\fIvalue\fP]
1200
is not given, the variable is assigned the null string. All
1202
undergo tilde expansion, parameter and variable expansion,
1203
command substitution, arithmetic expansion, and quote
1207
below). If the variable has its
1211
is evaluated as an arithmetic expression even if the $((...)) expansion is
1213
.B "Arithmetic Expansion"
1215
Word splitting is not performed, with the exception
1216
of \fB"$@"\fP as explained below under
1217
.BR "Special Parameters" .
1218
Pathname expansion is not performed.
1219
Assignment statements may also appear as arguments to the
1228
When in \fIposix mode\fP, these builtins may appear in a command after
1229
one or more instances of the \fBcommand\fP builtin and retain these
1230
assignment statement properties.
1232
In the context where an assignment statement is assigning a value
1233
to a shell variable or array index, the += operator can be used to
1234
append to or add to the variable's previous value.
1235
When += is applied to a variable for which the \fIinteger\fP attribute has been
1236
set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
1237
variable's current value, which is also evaluated.
1238
When += is applied to an array variable using compound assignment (see
1241
variable's value is not unset (as it is when using =), and new values are
1242
appended to the array beginning at one greater than the array's maximum index
1243
(for indexed arrays) or added as additional key\-value pairs in an
1245
When applied to a string-valued variable, \fIvalue\fP is expanded and
1246
appended to the variable's value.
1248
A variable can be assigned the \fInameref\fP attribute using the
1249
\fB\-n\fP option to the \fBdeclare\fP or \fBlocal\fP builtin commands
1250
(see the descriptions of \fBdeclare\fP and \fBlocal\fP below)
1251
to create a \fInameref\fP, or a reference to another variable.
1252
This allows variables to be manipulated indirectly.
1253
Whenever the nameref variable is referenced or assigned to, the operation
1254
is actually performed on the variable specified by the nameref variable's
1256
A nameref is commonly used within shell functions to refer to a variable
1257
whose name is passed as an argument to the function.
1258
For instance, if a variable name is passed to a shell function as its first
1262
.if t \f(CWdeclare -n ref=$1\fP
1263
.if n declare -n ref=$1
1266
inside the function creates a nameref variable \fBref\fP whose value is
1267
the variable name passed as the first argument.
1268
References and assignments to \fBref\fP are treated as references and
1269
assignments to the variable whose name was passed as \fB$1\fP.
1270
If the control variable in a \fBfor\fP loop has the nameref attribute,
1271
the list of words can be a list of shell variables, and a name reference
1272
will be established for each word in the list, in turn, when the loop is
1274
Array variables cannot be given the \fB\-n\fP attribute.
1275
However, nameref variables can reference array variables and subscripted
1277
Namerefs can be unset using the \fB\-n\fP option to the \fBunset\fP builtin.
1278
Otherwise, if \fBunset\fP is executed with the name of a nameref variable
1279
as an argument, the variable referenced by the nameref variable will be unset.
1280
.SS Positional Parameters
1283
.I positional parameter
1284
is a parameter denoted by one or more
1285
digits, other than the single digit 0. Positional parameters are
1286
assigned from the shell's arguments when it is invoked,
1287
and may be reassigned using the
1289
builtin command. Positional parameters may not be assigned to
1290
with assignment statements. The positional parameters are
1291
temporarily replaced when a shell function is executed (see
1296
When a positional parameter consisting of more than a single
1297
digit is expanded, it must be enclosed in braces (see
1301
.SS Special Parameters
1303
The shell treats several parameters specially. These parameters may
1304
only be referenced; assignment to them is not allowed.
1308
Expands to the positional parameters, starting from one.
1309
When the expansion is not within double quotes, each positional parameter
1310
expands to a separate word.
1311
In contexts where it is performed, those words
1312
are subject to further word splitting and pathname expansion.
1313
When the expansion occurs within double quotes, it expands to a single word
1314
with the value of each parameter separated by the first character
1318
special variable. That is, "\fB$*\fP" is equivalent
1319
to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1321
is the first character of the value of the
1327
is unset, the parameters are separated by spaces.
1331
is null, the parameters are joined without intervening separators.
1334
Expands to the positional parameters, starting from one. When the
1335
expansion occurs within double quotes, each parameter expands to a
1336
separate word. That is, "\fB$@\fP" is equivalent to
1337
"\fB$1\fP" "\fB$2\fP" ...
1338
If the double-quoted expansion occurs within a word, the expansion of
1339
the first parameter is joined with the beginning part of the original
1340
word, and the expansion of the last parameter is joined with the last
1341
part of the original word.
1342
When there are no positional parameters, "\fB$@\fP" and
1344
expand to nothing (i.e., they are removed).
1347
Expands to the number of positional parameters in decimal.
1350
Expands to the exit status of the most recently executed foreground
1354
Expands to the current option flags as specified upon invocation,
1357
builtin command, or those set by the shell itself
1363
Expands to the process ID of the shell. In a () subshell, it
1364
expands to the process ID of the current shell, not the
1368
Expands to the process ID of the job most recently placed into the
1369
background, whether executed as an asynchronous command or using
1370
the \fBbg\fP builtin (see
1376
Expands to the name of the shell or shell script. This is set at
1377
shell initialization. If
1379
is invoked with a file of commands,
1381
is set to the name of that file. If
1387
is set to the first argument after the string to be
1388
executed, if one is present. Otherwise, it is set
1389
to the filename used to invoke
1391
as given by argument zero.
1394
At shell startup, set to the absolute pathname used to invoke the
1395
shell or shell script being executed as passed in the environment
1397
Subsequently, expands to the last argument to the previous command,
1399
Also set to the full pathname used to invoke each command executed
1400
and placed in the environment exported to that command.
1401
When checking mail, this parameter holds the name of the mail file
1402
currently being checked.
1406
The following variables are set by the shell:
1411
Expands to the full filename used to invoke this instance of
1415
A colon-separated list of enabled shell options. Each word in
1416
the list is a valid argument for the
1420
builtin command (see
1422
.B "SHELL BUILTIN COMMANDS"
1423
below). The options appearing in
1426
are those reported as
1429
If this variable is in the environment when
1431
starts up, each shell option in the list will be enabled before
1432
reading any startup files.
1433
This variable is read-only.
1436
Expands to the process ID of the current \fBbash\fP process.
1437
This differs from \fB$$\fP under certain circumstances, such as subshells
1438
that do not require \fBbash\fP to be re-initialized.
1441
An associative array variable whose members correspond to the internal
1442
list of aliases as maintained by the \fBalias\fP builtin.
1443
Elements added to this array appear in the alias list; unsetting array
1444
elements cause aliases to be removed from the alias list.
1447
An array variable whose values are the number of parameters in each
1448
frame of the current \fBbash\fP execution call stack.
1450
parameters to the current subroutine (shell function or script executed
1451
with \fB.\fP or \fBsource\fP) is at the top of the stack.
1452
When a subroutine is executed, the number of parameters passed is pushed onto
1458
only when in extended debugging mode (see the description of the
1465
An array variable containing all of the parameters in the current \fBbash\fP
1466
execution call stack. The final parameter of the last subroutine call
1467
is at the top of the stack; the first parameter of the initial call is
1468
at the bottom. When a subroutine is executed, the parameters supplied
1475
only when in extended debugging mode
1476
(see the description of the
1483
An associative array variable whose members correspond to the internal
1484
hash table of commands as maintained by the \fBhash\fP builtin.
1485
Elements added to this array appear in the hash table; unsetting array
1486
elements cause commands to be removed from the hash table.
1489
The command currently being executed or about to be executed, unless the
1490
shell is executing a command as the result of a trap,
1491
in which case it is the command executing at the time of the trap.
1493
.B BASH_EXECUTION_STRING
1494
The command argument to the \fB\-c\fP invocation option.
1497
An array variable whose members are the line numbers in source files
1498
where each corresponding member of
1502
\fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
1503
file (\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP) where
1504
\fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called
1505
(or \fB${BASH_LINENO[\fP\fI$i-1\fP\fB]}\fP if referenced within another
1510
to obtain the current line number.
1513
An array variable whose members are assigned by the \fB=~\fP binary
1514
operator to the \fB[[\fP conditional command.
1515
The element with index 0 is the portion of the string
1516
matching the entire regular expression.
1517
The element with index \fIn\fP is the portion of the
1518
string matching the \fIn\fPth parenthesized subexpression.
1519
This variable is read-only.
1522
An array variable whose members are the source filenames
1523
where the corresponding shell function names in the
1526
array variable are defined.
1528
\fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP is defined in the file
1529
\fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fP and called from
1530
\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP.
1533
Incremented by one within each subshell or subshell environment when
1534
the shell begins executing in that environment.
1535
The initial value is 0.
1538
A readonly array variable whose members hold version information for
1541
The values assigned to the array members are as follows:
1545
.B BASH_VERSINFO[\fR0\fP]
1546
The major version number (the \fIrelease\fP).
1548
.B BASH_VERSINFO[\fR1\fP]
1549
The minor version number (the \fIversion\fP).
1551
.B BASH_VERSINFO[\fR2\fP]
1554
.B BASH_VERSINFO[\fR3\fP]
1557
.B BASH_VERSINFO[\fR4\fP]
1558
The release status (e.g., \fIbeta1\fP).
1560
.B BASH_VERSINFO[\fR5\fP]
1567
Expands to a string describing the version of this instance of
1571
An index into \fB${COMP_WORDS}\fP of the word containing the current
1573
This variable is available only in shell functions invoked by the
1574
programmable completion facilities (see \fBProgrammable Completion\fP
1578
The key (or final key of a key sequence) used to invoke the current
1579
completion function.
1582
The current command line.
1583
This variable is available only in shell functions and external
1584
commands invoked by the
1585
programmable completion facilities (see \fBProgrammable Completion\fP
1589
The index of the current cursor position relative to the beginning of
1590
the current command.
1591
If the current cursor position is at the end of the current command,
1592
the value of this variable is equal to \fB${#COMP_LINE}\fP.
1593
This variable is available only in shell functions and external
1594
commands invoked by the
1595
programmable completion facilities (see \fBProgrammable Completion\fP
1599
Set to an integer value corresponding to the type of completion attempted
1600
that caused a completion function to be called:
1601
\fITAB\fP, for normal completion,
1602
\fI?\fP, for listing completions after successive tabs,
1603
\fI!\fP, for listing alternatives on partial word completion,
1604
\fI@\fP, to list completions if the word is not unmodified,
1606
\fI%\fP, for menu completion.
1607
This variable is available only in shell functions and external
1608
commands invoked by the
1609
programmable completion facilities (see \fBProgrammable Completion\fP
1613
The set of characters that the \fBreadline\fP library treats as word
1614
separators when performing word completion.
1618
is unset, it loses its special properties, even if it is
1622
An array variable (see \fBArrays\fP below) consisting of the individual
1623
words in the current command line.
1624
The line is split into words as \fBreadline\fP would split it, using
1628
This variable is available only in shell functions invoked by the
1629
programmable completion facilities (see \fBProgrammable Completion\fP
1633
An array variable (see \fBArrays\fP below) created to hold the file descriptors
1634
for output from and input to an unnamed coprocess (see \fBCoprocesses\fP
1638
An array variable (see
1640
below) containing the current contents of the directory stack.
1641
Directories appear in the stack in the order they are displayed by the
1644
Assigning to members of this array variable may be used to modify
1645
directories already in the stack, but the
1649
builtins must be used to add and remove directories.
1650
Assignment to this variable will not change the current directory.
1654
is unset, it loses its special properties, even if it is
1658
Expands to the effective user ID of the current user, initialized at
1659
shell startup. This variable is readonly.
1662
An array variable containing the names of all shell functions
1663
currently in the execution call stack.
1664
The element with index 0 is the name of any currently-executing
1666
The bottom-most element (the one with the highest index) is
1667
.if t \f(CW"main"\fP.
1669
This variable exists only when a shell function is executing.
1673
have no effect and return an error status.
1677
is unset, it loses its special properties, even if it is
1681
This variable can be used with \fBBASH_LINENO\fP and \fBBASH_SOURCE\fP.
1682
Each element of \fBFUNCNAME\fP has corresponding elements in
1683
\fBBASH_LINENO\fP and \fBBASH_SOURCE\fP to describe the call stack.
1684
For instance, \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called from the file
1685
\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP at line number
1686
\fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP.
1687
The \fBcaller\fP builtin displays the current call stack using this
1691
An array variable containing the list of groups of which the current
1696
have no effect and return an error status.
1700
is unset, it loses its special properties, even if it is
1704
The history number, or index in the history list, of the current
1709
is unset, it loses its special properties, even if it is
1713
Automatically set to the name of the current host.
1716
Automatically set to a string that uniquely
1717
describes the type of machine on which
1720
The default is system-dependent.
1723
Each time this parameter is referenced, the shell substitutes
1724
a decimal number representing the current sequential line number
1725
(starting with 1) within a script or function. When not in a
1726
script or function, the value substituted is not guaranteed to
1731
is unset, it loses its special properties, even if it is
1735
Automatically set to a string that fully describes the system
1738
is executing, in the standard GNU \fIcpu-company-system\fP format.
1739
The default is system-dependent.
1742
An array variable (see \fBArrays\fP below) created to hold the text
1743
read by the \fBmapfile\fP builtin when no variable name is supplied.
1746
The previous working directory as set by the
1751
The value of the last option argument processed by the
1753
builtin command (see
1755
.B SHELL BUILTIN COMMANDS
1759
The index of the next argument to be processed by the
1761
builtin command (see
1763
.B SHELL BUILTIN COMMANDS
1767
Automatically set to a string that
1768
describes the operating system on which
1771
The default is system-dependent.
1774
An array variable (see
1776
below) containing a list of exit status values from the processes
1777
in the most-recently-executed foreground pipeline (which may
1778
contain only a single command).
1781
The process ID of the shell's parent. This variable is readonly.
1784
The current working directory as set by the
1789
Each time this parameter is referenced, a random integer between
1791
generated. The sequence of random numbers may be initialized by assigning
1798
is unset, it loses its special properties, even if it is
1804
line buffer, for use with
1805
.if t \f(CWbind -x\fP
1809
.B "SHELL BUILTIN COMMANDS"
1813
The position of the insertion point in the
1815
line buffer, for use with
1816
.if t \f(CWbind -x\fP
1820
.B "SHELL BUILTIN COMMANDS"
1824
Set to the line of input read by the
1826
builtin command when no arguments are supplied.
1829
Each time this parameter is
1830
referenced, the number of seconds since shell invocation is returned. If a
1831
value is assigned to
1834
the value returned upon subsequent
1836
the number of seconds since the assignment plus the value assigned.
1840
is unset, it loses its special properties, even if it is
1844
A colon-separated list of enabled shell options. Each word in
1845
the list is a valid argument for the
1849
builtin command (see
1851
.B "SHELL BUILTIN COMMANDS"
1852
below). The options appearing in
1855
are those reported as
1858
If this variable is in the environment when
1860
starts up, each shell option in the list will be enabled before
1861
reading any startup files.
1862
This variable is read-only.
1865
Incremented by one each time an instance of
1870
Expands to the user ID of the current user, initialized at shell startup.
1871
This variable is readonly.
1874
The following variables are used by the shell. In some cases,
1876
assigns a default value to a variable; these cases are noted
1882
The value is used to set the shell's compatibility level.
1883
See the description of the \fBshopt\fP builtin below under
1884
\fBSHELL BUILTIN COMMANDS\fP
1885
for a description of the various compatibility
1886
levels and their effects.
1887
The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
1888
corresponding to the desired compatibility level.
1889
If \fBBASH_COMPAT\fP is unset or set to the empty string, the compatibility
1890
level is set to the default for the current version.
1891
If \fBBASH_COMPAT\fP is set to a value that is not one of the valid
1892
compatibility levels, the shell prints an error message and sets the
1893
compatibility level to the default for the current version.
1894
The valid compatibility levels correspond to the compatibility options
1895
accepted by the \fBshopt\fP builtin described below (for example,
1896
\fBcompat42\fP means that 4.2 and 42 are valid values).
1897
The current version is also a valid value.
1900
If this parameter is set when \fBbash\fP is executing a shell script,
1901
its value is interpreted as a filename containing commands to
1902
initialize the shell, as in
1907
is subjected to parameter expansion, command substitution, and arithmetic
1908
expansion before being interpreted as a filename.
1911
is not used to search for the resultant filename.
1914
If set to an integer corresponding to a valid file descriptor, \fBbash\fP
1915
will write the trace output generated when
1916
.if t \f(CWset -x\fP
1918
is enabled to that file descriptor.
1919
The file descriptor is closed when
1922
is unset or assigned a new value.
1926
or assigning it the empty string causes the
1927
trace output to be sent to the standard error.
1931
to 2 (the standard error file
1932
descriptor) and then unsetting it will result in the standard error
1936
The search path for the
1939
This is a colon-separated list of directories in which the shell looks
1940
for destination directories specified by the
1944
.if t \f(CW".:~:/usr"\fP.
1948
Set the number of exited child status values for the shell to remember.
1949
Bash will not allow this value to be decreased below a POSIX-mandated
1950
minimum, and there is a maximum value (currently 8192) that this may
1952
The minimum value is system-dependent.
1955
Used by the \fBselect\fP compound command to determine the terminal width
1956
when printing selection lists.
1957
Automatically set if the
1959
option is enabled or in an interactive shell upon receipt of a
1964
An array variable from which \fBbash\fP reads the possible completions
1965
generated by a shell function invoked by the programmable completion
1966
facility (see \fBProgrammable Completion\fP below).
1967
Each array element contains one possible completion.
1970
If \fBbash\fP finds this variable in the environment when the shell starts
1974
it assumes that the shell is running in an Emacs shell buffer and disables
1981
used when the shell is invoked in POSIX mode.
1984
The default editor for the
1989
A colon-separated list of suffixes to ignore when performing
1990
filename completion (see
1994
A filename whose suffix matches one of the entries in
1997
is excluded from the list of matched filenames.
1999
.if t \f(CW".o:~"\fP.
2001
(Quoting is needed when assigning a value to this variable,
2002
which contains tildes).
2005
If set to a numeric value greater than 0, defines a maximum function
2006
nesting level. Function invocations that exceed this nesting level
2007
will cause the current command to abort.
2010
A colon-separated list of patterns defining the set of filenames to
2011
be ignored by pathname expansion.
2012
If a filename matched by a pathname expansion pattern also matches one
2016
it is removed from the list of matches.
2019
A colon-separated list of values controlling how commands are saved on
2021
If the list of values includes
2023
lines which begin with a
2025
character are not saved in the history list.
2028
causes lines matching the previous history entry to not be saved.
2031
is shorthand for \fIignorespace\fP and \fIignoredups\fP.
2034
causes all previous lines matching the current line to be removed from
2035
the history list before that line is saved.
2036
Any value not in the above list is ignored.
2040
is unset, or does not include a valid value,
2041
all lines read by the shell parser are saved on the history list,
2042
subject to the value of
2045
The second and subsequent lines of a multi-line compound command are
2046
not tested, and are added to the history regardless of the value of
2051
The name of the file in which command history is saved (see
2054
below). The default value is \fI~/.bash_history\fP. If unset, the
2055
command history is not saved when a shell exits.
2058
The maximum number of lines contained in the history file. When this
2059
variable is assigned a value, the history file is truncated, if
2061
to contain no more than that number of lines by removing the oldest entries.
2062
The history file is also truncated to this size after
2063
writing it when a shell exits.
2064
If the value is 0, the history file is truncated to zero size.
2065
Non-numeric values and numeric values less than zero inhibit truncation.
2066
The shell sets the default value to the value of \fBHISTSIZE\fP
2067
after reading any startup files.
2070
A colon-separated list of patterns used to decide which command lines
2071
should be saved on the history list. Each pattern is anchored at the
2072
beginning of the line and must match the complete line (no implicit
2073
`\fB*\fP' is appended). Each pattern is tested against the line
2074
after the checks specified by
2078
In addition to the normal shell pattern matching characters, `\fB&\fP'
2079
matches the previous history line. `\fB&\fP' may be escaped using a
2080
backslash; the backslash is removed before attempting a match.
2081
The second and subsequent lines of a multi-line compound command are
2082
not tested, and are added to the history regardless of the value of
2087
The number of commands to remember in the command history (see
2091
If the value is 0, commands are not saved in the history list.
2092
Numeric values less than zero result in every command being saved
2093
on the history list (there is no limit).
2094
The shell sets the default value to 500 after reading any startup files.
2097
If this variable is set and not null, its value is used as a format string
2098
for \fIstrftime\fP(3) to print the time stamp associated with each history
2099
entry displayed by the \fBhistory\fP builtin.
2100
If this variable is set, time stamps are written to the history file so
2101
they may be preserved across shell sessions.
2102
This uses the history comment character to distinguish timestamps from
2103
other history lines.
2106
The home directory of the current user; the default argument for the
2107
\fBcd\fP builtin command.
2108
The value of this variable is also used when performing tilde expansion.
2111
Contains the name of a file in the same format as
2113
that should be read when the shell needs to complete a
2115
The list of possible hostname completions may be changed while the
2117
the next time hostname completion is attempted after the
2120
adds the contents of the new file to the existing list.
2124
is set, but has no value, or does not name a readable file,
2125
\fBbash\fP attempts to read
2127
to obtain the list of possible hostname completions.
2131
is unset, the hostname list is cleared.
2135
.I Internal Field Separator
2137
for word splitting after expansion and to
2138
split lines into words with the
2140
builtin command. The default value is
2141
``<space><tab><newline>''.
2145
action of an interactive shell on receipt of an
2148
character as the sole input. If set, the value is the number of
2152
characters which must be
2153
typed as the first characters on an input line before
2155
exits. If the variable exists but does not have a numeric value, or
2156
has no value, the default value is 10. If it does not exist,
2159
signifies the end of input to the shell.
2162
The filename for the
2164
startup file, overriding the default of
2172
Used to determine the locale category for any category not specifically
2173
selected with a variable starting with \fBLC_\fP.
2176
This variable overrides the value of
2180
\fBLC_\fP variable specifying a locale category.
2183
This variable determines the collation order used when sorting the
2184
results of pathname expansion, and determines the behavior of range
2185
expressions, equivalence classes, and collating sequences within
2186
pathname expansion and pattern matching.
2189
This variable determines the interpretation of characters and the
2190
behavior of character classes within pathname expansion and pattern
2194
This variable determines the locale used to translate double-quoted
2195
strings preceded by a \fB$\fP.
2198
This variable determines the locale category used for number formatting.
2201
Used by the \fBselect\fP compound command to determine the column length
2202
for printing selection lists.
2203
Automatically set if the
2205
option is enabled or in an interactive shell upon receipt of a
2210
If this parameter is set to a file or directory name and the
2213
variable is not set,
2215
informs the user of the arrival of mail in the specified file or
2216
Maildir-format directory.
2222
checks for mail. The default is 60 seconds. When it is time to check
2223
for mail, the shell does so before displaying the primary prompt.
2224
If this variable is unset, or set to a value that is not a number
2225
greater than or equal to zero, the shell disables mail checking.
2228
A colon-separated list of filenames to be checked for mail.
2229
The message to be printed when mail arrives in a particular file
2230
may be specified by separating the filename from the message with a `?'.
2231
When used in the text of the message, \fB$_\fP expands to the name of
2232
the current mailfile.
2236
\fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
2239
supplies a default value for this variable, but the location of the user
2240
mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
2244
If set to the value 1,
2246
displays error messages generated by the
2248
builtin command (see
2250
.B SHELL BUILTIN COMMANDS
2254
is initialized to 1 each time the shell is invoked or a shell
2258
The search path for commands. It
2259
is a colon-separated list of directories in which
2260
the shell looks for commands (see
2262
.B COMMAND EXECUTION
2264
A zero-length (null) directory name in the value of
2267
indicates the current directory.
2268
A null directory name may appear as two adjacent colons, or as an initial
2270
The default path is system-dependent,
2271
and is set by the administrator who installs
2274
.if t \f(CW/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin\fP.
2275
.if n ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
2278
If this variable is in the environment when \fBbash\fP starts, the shell
2279
enters \fIposix mode\fP before reading the startup files, as if the
2281
invocation option had been supplied. If it is set while the shell is
2282
running, \fBbash\fP enables \fIposix mode\fP, as if the command
2283
.if t \f(CWset -o posix\fP
2284
.if n \fIset -o posix\fP
2288
If set, the value is executed as a command prior to issuing each primary
2292
If set to a number greater than zero, the value is used as the number of
2293
trailing directory components to retain when expanding the \fB\ew\fP and
2294
\fB\eW\fP prompt string escapes (see
2297
below). Characters removed are replaced with an ellipsis.
2300
The value of this parameter is expanded (see
2303
below) and used as the primary prompt string. The default value is
2304
``\fB\es\-\ev\e$ \fP''.
2307
The value of this parameter is expanded as with
2310
and used as the secondary prompt string. The default is
2314
The value of this parameter is used as the prompt for the
2322
The value of this parameter is expanded as with
2325
and the value is printed before each command
2327
displays during an execution trace. The first character of
2330
is replicated multiple times, as necessary, to indicate multiple
2331
levels of indirection. The default is ``\fB+ \fP''.
2334
The full pathname to the shell is kept in this environment variable.
2335
If it is not set when the shell starts,
2337
assigns to it the full pathname of the current user's login shell.
2340
The value of this parameter is used as a format string specifying
2341
how the timing information for pipelines prefixed with the
2343
reserved word should be displayed.
2344
The \fB%\fP character introduces an escape sequence that is
2345
expanded to a time value or other information.
2346
The escape sequences and their meanings are as follows; the
2347
braces denote optional portions.
2356
The elapsed time in seconds.
2359
The number of CPU seconds spent in user mode.
2362
The number of CPU seconds spent in system mode.
2365
The CPU percentage, computed as (%U + %S) / %R.
2369
The optional \fIp\fP is a digit specifying the \fIprecision\fP,
2370
the number of fractional digits after a decimal point.
2371
A value of 0 causes no decimal point or fraction to be output.
2372
At most three places after the decimal point may be specified;
2373
values of \fIp\fP greater than 3 are changed to 3.
2374
If \fIp\fP is not specified, the value 3 is used.
2376
The optional \fBl\fP specifies a longer format, including
2377
minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
2378
The value of \fIp\fP determines whether or not the fraction is
2381
If this variable is not set, \fBbash\fP acts as if it had the
2382
value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\et%3lS\(aq\fP.
2383
If the value is null, no timing information is displayed.
2384
A trailing newline is added when the format string is displayed.
2388
If set to a value greater than zero,
2392
default timeout for the \fBread\fP builtin.
2393
The \fBselect\fP command terminates if input does not arrive
2397
seconds when input is coming from a terminal.
2398
In an interactive shell, the value is interpreted as the
2399
number of seconds to wait for a line of input after issuing the
2402
terminates after waiting for that number of seconds if a complete
2403
line of input does not arrive.
2406
If set, \fBbash\fP uses its value as the name of a directory in which
2407
\fBbash\fP creates temporary files for the shell's use.
2410
This variable controls how the shell interacts with the user and
2411
job control. If this variable is set, single word simple
2412
commands without redirections are treated as candidates for resumption
2413
of an existing stopped job. There is no ambiguity allowed; if there is
2414
more than one job beginning with the string typed, the job most recently
2415
accessed is selected. The
2417
of a stopped job, in this context, is the command line used to
2421
the string supplied must match the name of a stopped job exactly;
2424
the string supplied needs to match a substring of the name of a
2427
value provides functionality analogous to the
2432
below). If set to any other value, the supplied string must
2433
be a prefix of a stopped job's name; this provides functionality
2434
analogous to the \fB%\fP\fIstring\fP job identifier.
2437
The two or three characters which control history expansion
2438
and tokenization (see
2440
.B HISTORY EXPANSION
2441
below). The first character is the \fIhistory expansion\fP character,
2442
the character which signals the start of a history
2443
expansion, normally `\fB!\fP'.
2444
The second character is the \fIquick substitution\fP
2445
character, which is used as shorthand for re-running the previous
2446
command entered, substituting one string for another in the command.
2447
The default is `\fB^\fP'.
2448
The optional third character is the character
2449
which indicates that the remainder of the line is a comment when found
2450
as the first character of a word, normally `\fB#\fP'. The history
2451
comment character causes history substitution to be skipped for the
2452
remaining words on the line. It does not necessarily cause the shell
2453
parser to treat the rest of the line as a comment.
2457
provides one-dimensional indexed and associative array variables.
2458
Any variable may be used as an indexed array; the
2460
builtin will explicitly declare an array.
2462
limit on the size of an array, nor any requirement that members
2463
be indexed or assigned contiguously.
2464
Indexed arrays are referenced using integers (including arithmetic
2465
expressions) and are zero-based; associative arrays are referenced
2466
using arbitrary strings.
2467
Unless otherwise noted, indexed array indices must be non-negative integers.
2469
An indexed array is created automatically if any variable is assigned to
2470
using the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
2472
is treated as an arithmetic expression that must evaluate to a number.
2473
To explicitly declare an indexed array, use
2474
.B declare \-a \fIname\fP
2477
.B SHELL BUILTIN COMMANDS
2479
.B declare \-a \fIname\fP[\fIsubscript\fP]
2480
is also accepted; the \fIsubscript\fP is ignored.
2482
Associative arrays are created using
2483
.BR "declare \-A \fIname\fP" .
2486
specified for an array variable using the
2490
builtins. Each attribute applies to all members of an array.
2492
Arrays are assigned to using compound assignments of the form
2493
\fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
2494
\fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP.
2495
Indexed array assignments do not require anything but \fIstring\fP.
2496
When assigning to indexed arrays, if the optional brackets and subscript
2497
are supplied, that index is assigned to;
2498
otherwise the index of the element assigned is the last index assigned
2499
to by the statement plus one. Indexing starts at zero.
2501
When assigning to an associative array, the subscript is required.
2503
This syntax is also accepted by the
2505
builtin. Individual array elements may be assigned to using the
2506
\fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
2507
When assigning to an indexed array, if
2509
is subscripted by a negative number, that number is
2510
interpreted as relative to one greater than the maximum index of
2511
\fIname\fP, so negative indices count back from the end of the
2512
array, and an index of \-1 references the last element.
2514
Any element of an array may be referenced using
2515
${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
2516
conflicts with pathname expansion. If
2517
\fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
2518
all members of \fIname\fP. These subscripts differ only when the
2519
word appears within double quotes. If the word is double-quoted,
2520
${\fIname\fP[*]} expands to a single
2521
word with the value of each array member separated by the first
2525
special variable, and ${\fIname\fP[@]} expands each element of
2526
\fIname\fP to a separate word. When there are no array members,
2527
${\fIname\fP[@]} expands to nothing.
2528
If the double-quoted expansion occurs within a word, the expansion of
2529
the first parameter is joined with the beginning part of the original
2530
word, and the expansion of the last parameter is joined with the last
2531
part of the original word.
2532
This is analogous to the expansion
2533
of the special parameters \fB*\fP and \fB@\fP (see
2534
.B Special Parameters
2535
above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
2536
${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
2537
\fB@\fP, the expansion is the number of elements in the array.
2538
Referencing an array variable without a subscript is equivalent to
2539
referencing the array with a subscript of 0.
2542
used to reference an element of an indexed array
2543
evaluates to a number less than zero, it is
2544
interpreted as relative to one greater than the maximum index of the array,
2545
so negative indices count back from the end of the
2546
array, and an index of \-1 references the last element.
2548
An array variable is considered set if a subscript has been assigned a
2549
value. The null string is a valid value.
2551
It is possible to obtain the keys (indices) of an array as well as the values.
2552
${\fB!\fP\fIname\fP[\fI@\fP]} and ${\fB!\fP\fIname\fP[\fI*\fP]}
2553
expand to the indices assigned in array variable \fIname\fP.
2554
The treatment when in double quotes is similar to the expansion of the
2555
special parameters \fI@\fP and \fI*\fP within double quotes.
2559
builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
2560
destroys the array element at index \fIsubscript\fP.
2561
Negative subscripts to indexed arrays are interpreted as described above.
2562
Care must be taken to avoid unwanted side effects caused by pathname
2564
\fBunset\fP \fIname\fP, where \fIname\fP is an array, or
2565
\fBunset\fP \fIname\fP[\fIsubscript\fP], where
2566
\fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
2573
builtins each accept a
2575
option to specify an indexed array and a
2577
option to specify an associative array.
2578
If both options are supplied,
2585
option to assign a list of words read from the standard input
2590
builtins display array values in a way that allows them to be
2591
reused as assignments.
2593
Expansion is performed on the command line after it has been split into
2594
words. There are seven kinds of expansion performed:
2595
.IR "brace expansion" ,
2596
.IR "tilde expansion" ,
2597
.IR "parameter and variable expansion" ,
2598
.IR "command substitution" ,
2599
.IR "arithmetic expansion" ,
2600
.IR "word splitting" ,
2602
.IR "pathname expansion" .
2604
The order of expansions is:
2606
tilde expansion, parameter and variable expansion, arithmetic expansion,
2607
and command substitution (done in a left-to-right fashion);
2609
and pathname expansion.
2611
On systems that can support it, there is an additional expansion
2612
available: \fIprocess substitution\fP.
2613
This is performed at the
2614
same time as tilde, parameter, variable, and arithmetic expansion and
2615
command substitution.
2617
Only brace expansion, word splitting, and pathname expansion
2618
can change the number of words of the expansion; other expansions
2619
expand a single word to a single word.
2620
The only exceptions to this are the expansions of
2621
"\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
2622
as explained above (see
2627
.I "Brace expansion"
2628
is a mechanism by which arbitrary strings
2629
may be generated. This mechanism is similar to
2630
\fIpathname expansion\fP, but the filenames generated
2631
need not exist. Patterns to be brace expanded take
2632
the form of an optional
2634
followed by either a series of comma-separated strings or
2635
a sequence expression between a pair of braces, followed by
2638
The preamble is prefixed to each string contained
2639
within the braces, and the postscript is then appended
2640
to each resulting string, expanding left to right.
2642
Brace expansions may be nested. The results of each expanded
2643
string are not sorted; left to right order is preserved.
2644
For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
2646
A sequence expression takes the form
2647
\fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB[..\fP\fIincr\fP\fB]}\fP,
2648
where \fIx\fP and \fIy\fP are either integers or single characters,
2649
and \fIincr\fP, an optional increment, is an integer.
2650
When integers are supplied, the expression expands to each number between
2651
\fIx\fP and \fIy\fP, inclusive.
2652
Supplied integers may be prefixed with \fI0\fP to force each term to have the
2654
When either \fIx\fP or \fPy\fP begins with a zero, the shell
2655
attempts to force all generated terms to contain the same number of digits,
2656
zero-padding where necessary.
2657
When characters are supplied, the expression expands to each character
2658
lexicographically between \fIx\fP and \fIy\fP, inclusive,
2659
using the default C locale.
2660
Note that both \fIx\fP and \fIy\fP must be of the same type.
2661
When the increment is supplied, it is used as the difference between
2662
each term. The default increment is 1 or -1 as appropriate.
2664
Brace expansion is performed before any other expansions,
2665
and any characters special to other expansions are preserved
2666
in the result. It is strictly textual.
2668
does not apply any syntactic interpretation to the context of the
2669
expansion or the text between the braces.
2671
A correctly-formed brace expansion must contain unquoted opening
2672
and closing braces, and at least one unquoted comma or a valid
2673
sequence expression.
2674
Any incorrectly formed brace expansion is left unchanged.
2675
A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
2676
being considered part of a brace expression.
2677
To avoid conflicts with parameter expansion, the string \fB${\fP
2678
is not considered eligible for brace expansion.
2680
This construct is typically used as shorthand when the common
2681
prefix of the strings to be generated is longer than in the
2685
mkdir /usr/local/src/bash/{old,new,dist,bugs}
2689
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2692
Brace expansion introduces a slight incompatibility with
2693
historical versions of
2696
does not treat opening or closing braces specially when they
2697
appear as part of a word, and preserves them in the output.
2699
removes braces from words as a consequence of brace
2700
expansion. For example, a word entered to
2703
appears identically in the output. The same word is
2708
If strict compatibility with
2714
option or disable brace expansion with the
2720
.B SHELL BUILTIN COMMANDS
2724
If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2725
the characters preceding the first unquoted slash (or all characters,
2726
if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2727
If none of the characters in the tilde-prefix are quoted, the
2728
characters in the tilde-prefix following the tilde are treated as a
2729
possible \fIlogin name\fP.
2730
If this login name is the null string, the tilde is replaced with the
2731
value of the shell parameter
2737
is unset, the home directory of the user executing the shell is
2738
substituted instead.
2739
Otherwise, the tilde-prefix is replaced with the home directory
2740
associated with the specified login name.
2742
If the tilde-prefix is a `~+', the value of the shell variable
2745
replaces the tilde-prefix.
2746
If the tilde-prefix is a `~\-', the value of the shell variable
2749
if it is set, is substituted.
2750
If the characters following the tilde in the tilde-prefix consist
2751
of a number \fIN\fP, optionally prefixed
2752
by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2753
element from the directory stack, as it would be displayed by the
2755
builtin invoked with the tilde-prefix as an argument.
2756
If the characters following the tilde in the tilde-prefix consist of a
2757
number without a leading `+' or `\-', `+' is assumed.
2759
If the login name is invalid, or the tilde expansion fails, the word
2762
Each variable assignment is checked for unquoted tilde-prefixes immediately
2767
In these cases, tilde expansion is also performed.
2768
Consequently, one may use filenames with tildes in assignments to
2776
and the shell assigns the expanded value.
2777
.SS Parameter Expansion
2779
The `\fB$\fP' character introduces parameter expansion,
2780
command substitution, or arithmetic expansion. The parameter name
2781
or symbol to be expanded may be enclosed in braces, which
2782
are optional but serve to protect the variable to be expanded from
2783
characters immediately following it which could be
2784
interpreted as part of the name.
2786
When braces are used, the matching ending brace is the first `\fB}\fP'
2787
not escaped by a backslash or within a quoted string, and not within an
2788
embedded arithmetic expansion, command substitution, or parameter
2794
The value of \fIparameter\fP is substituted. The braces are required
2797
is a positional parameter with more than one digit,
2800
is followed by a character which is not to be
2801
interpreted as part of its name.
2802
The \fIparameter\fP is a shell parameter as described above
2803
\fBPARAMETERS\fP) or an array reference (\fBArrays\fP).
2806
If the first character of \fIparameter\fP is an exclamation point (\fB!\fP),
2807
it introduces a level of variable indirection.
2808
\fBBash\fP uses the value of the variable formed from the rest of
2809
\fIparameter\fP as the name of the variable; this variable is then
2810
expanded and that value is used in the rest of the substitution, rather
2811
than the value of \fIparameter\fP itself.
2812
This is known as \fIindirect expansion\fP.
2813
The exceptions to this are the expansions of ${\fB!\fP\fIprefix\fP\fB*\fP} and
2814
${\fB!\fP\fIname\fP[\fI@\fP]} described below.
2815
The exclamation point must immediately follow the left brace in order to
2816
introduce indirection.
2818
In each of the cases below, \fIword\fP is subject to tilde expansion,
2819
parameter expansion, command substitution, and arithmetic expansion.
2821
When not performing substring expansion, using the forms documented below
2823
\fBbash\fP tests for a parameter that is unset or null. Omitting the colon
2824
results in a test only for a parameter that is unset.
2828
${\fIparameter\fP\fB:\-\fP\fIword\fP}
2829
\fBUse Default Values\fP. If
2831
is unset or null, the expansion of
2833
is substituted. Otherwise, the value of
2837
${\fIparameter\fP\fB:=\fP\fIword\fP}
2838
\fBAssign Default Values\fP.
2841
is unset or null, the expansion of
2847
is then substituted. Positional parameters and special parameters may
2848
not be assigned to in this way.
2850
${\fIparameter\fP\fB:?\fP\fIword\fP}
2851
\fBDisplay Error if Null or Unset\fP.
2854
is null or unset, the expansion of \fIword\fP (or a message to that effect
2857
is not present) is written to the standard error and the shell, if it
2858
is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2861
${\fIparameter\fP\fB:+\fP\fIword\fP}
2862
\fBUse Alternate Value\fP.
2865
is null or unset, nothing is substituted, otherwise the expansion of
2869
${\fIparameter\fP\fB:\fP\fIoffset\fP}
2872
${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2874
\fBSubstring Expansion\fP.
2875
Expands to up to \fIlength\fP characters of the value of \fIparameter\fP
2876
starting at the character specified by \fIoffset\fP.
2877
If \fIparameter\fP is \fB@\fP, an indexed array subscripted by
2878
\fB@\fP or \fB*\fP, or an associative array name, the results differ as
2880
If \fIlength\fP is omitted, expands to the substring of the value of
2881
\fIparameter\fP starting at the character specified by \fIoffset\fP
2882
and extending to the end of the value.
2883
\fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2886
ARITHMETIC EVALUATION
2889
If \fIoffset\fP evaluates to a number less than zero, the value
2890
is used as an offset in characters
2891
from the end of the value of \fIparameter\fP.
2892
If \fIlength\fP evaluates to a number less than zero,
2893
it is interpreted as an offset in characters
2894
from the end of the value of \fIparameter\fP rather than
2895
a number of characters, and the expansion is the characters between
2896
\fIoffset\fP and that result.
2897
Note that a negative offset must be separated from the colon by at least
2898
one space to avoid being confused with the \fB:-\fP expansion.
2900
If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2901
parameters beginning at \fIoffset\fP.
2902
A negative \fIoffset\fP is taken relative to one greater than the greatest
2903
positional parameter, so an offset of -1 evaluates to the last positional
2905
It is an expansion error if \fIlength\fP evaluates to a number less than
2908
If \fIparameter\fP is an indexed array name subscripted by @ or *,
2909
the result is the \fIlength\fP
2910
members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2911
A negative \fIoffset\fP is taken relative to one greater than the maximum
2912
index of the specified array.
2913
It is an expansion error if \fIlength\fP evaluates to a number less than
2916
Substring expansion applied to an associative array produces undefined
2919
Substring indexing is zero-based unless the positional parameters
2920
are used, in which case the indexing starts at 1 by default.
2921
If \fIoffset\fP is 0, and the positional parameters are used, \fB$0\fP is
2922
prefixed to the list.
2924
${\fB!\fP\fIprefix\fP\fB*\fP}
2927
${\fB!\fP\fIprefix\fP\fB@\fP}
2929
\fBNames matching prefix\fP.
2930
Expands to the names of variables whose names begin with \fIprefix\fP,
2931
separated by the first character of the
2935
When \fI@\fP is used and the expansion appears within double quotes, each
2936
variable name expands to a separate word.
2938
${\fB!\fP\fIname\fP[\fI@\fP]}
2941
${\fB!\fP\fIname\fP[\fI*\fP]}
2943
\fBList of array keys\fP.
2944
If \fIname\fP is an array variable, expands to the list of array indices
2945
(keys) assigned in \fIname\fP.
2946
If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
2948
When \fI@\fP is used and the expansion appears within double quotes, each
2949
key expands to a separate word.
2951
${\fB#\fP\fIparameter\fP}
2952
\fBParameter length\fP.
2953
The length in characters of the value of \fIparameter\fP is substituted.
2960
the value substituted is the number of positional parameters.
2963
is an array name subscripted by
2967
the value substituted is the number of elements in the array.
2970
is an indexed array name subscripted by a negative number, that number is
2971
interpreted as relative to one greater than the maximum index of
2972
\fIparameter\fP, so negative indices count back from the end of the
2973
array, and an index of \-1 references the last element.
2975
${\fIparameter\fP\fB#\fP\fIword\fP}
2978
${\fIparameter\fP\fB##\fP\fIword\fP}
2980
\fBRemove matching prefix pattern\fP.
2983
is expanded to produce a pattern just as in pathname
2984
expansion. If the pattern matches the beginning of
2987
then the result of the expansion is the expanded value of
2989
with the shortest matching pattern (the ``\fB#\fP'' case) or the
2990
longest matching pattern (the ``\fB##\fP'' case) deleted.
2997
the pattern removal operation is applied to each positional
2998
parameter in turn, and the expansion is the resultant list.
3001
is an array variable subscripted with
3005
the pattern removal operation is applied to each member of the
3006
array in turn, and the expansion is the resultant list.
3008
${\fIparameter\fP\fB%\fP\fIword\fP}
3011
${\fIparameter\fP\fB%%\fP\fIword\fP}
3013
\fBRemove matching suffix pattern\fP.
3014
The \fIword\fP is expanded to produce a pattern just as in
3016
If the pattern matches a trailing portion of the expanded value of
3018
then the result of the expansion is the expanded value of
3020
with the shortest matching pattern (the ``\fB%\fP'' case) or the
3021
longest matching pattern (the ``\fB%%\fP'' case) deleted.
3028
the pattern removal operation is applied to each positional
3029
parameter in turn, and the expansion is the resultant list.
3032
is an array variable subscripted with
3036
the pattern removal operation is applied to each member of the
3037
array in turn, and the expansion is the resultant list.
3039
${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
3040
\fBPattern substitution\fP.
3041
The \fIpattern\fP is expanded to produce a pattern just as in
3043
\fIParameter\fP is expanded and the longest match of \fIpattern\fP
3044
against its value is replaced with \fIstring\fP.
3045
If \fIpattern\fP begins with \fB/\fP, all matches of \fIpattern\fP are
3046
replaced with \fIstring\fP. Normally only the first match is replaced.
3047
If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
3048
of the expanded value of \fIparameter\fP.
3049
If \fIpattern\fP begins with \fB%\fP, it must match at the end
3050
of the expanded value of \fIparameter\fP.
3051
If \fIstring\fP is null, matches of \fIpattern\fP are deleted
3052
and the \fB/\fP following \fIpattern\fP may be omitted.
3059
the substitution operation is applied to each positional
3060
parameter in turn, and the expansion is the resultant list.
3063
is an array variable subscripted with
3067
the substitution operation is applied to each member of the
3068
array in turn, and the expansion is the resultant list.
3070
${\fIparameter\fP\fB^\fP\fIpattern\fP}
3073
${\fIparameter\fP\fB^^\fP\fIpattern\fP}
3075
${\fIparameter\fP\fB,\fP\fIpattern\fP}
3077
${\fIparameter\fP\fB,,\fP\fIpattern\fP}
3079
\fBCase modification\fP.
3080
This expansion modifies the case of alphabetic characters in \fIparameter\fP.
3081
The \fIpattern\fP is expanded to produce a pattern just as in
3083
Each character in the expanded value of \fIparameter\fP is tested against
3084
\fIpattern\fP, and, if it matches the pattern, its case is converted.
3085
The pattern should not attempt to match more than one character.
3086
The \fB^\fP operator converts lowercase letters matching \fIpattern\fP
3087
to uppercase; the \fB,\fP operator converts matching uppercase letters
3089
The \fB^^\fP and \fB,,\fP expansions convert each matched character in the
3090
expanded value; the \fB^\fP and \fB,\fP expansions match and convert only
3091
the first character in the expanded value.
3092
If \fIpattern\fP is omitted, it is treated like a \fB?\fP, which matches
3100
the case modification operation is applied to each positional
3101
parameter in turn, and the expansion is the resultant list.
3104
is an array variable subscripted with
3108
the case modification operation is applied to each member of the
3109
array in turn, and the expansion is the resultant list.
3110
.SS Command Substitution
3112
\fICommand substitution\fP allows the output of a command to replace
3113
the command name. There are two forms:
3116
\fB$(\fP\fIcommand\fP\|\fB)\fP
3120
\fB\`\fP\fIcommand\fP\fB\`\fP
3124
performs the expansion by executing \fIcommand\fP and
3125
replacing the command substitution with the standard output of the
3126
command, with any trailing newlines deleted.
3127
Embedded newlines are not deleted, but they may be removed during
3129
The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
3130
the equivalent but faster \fB$(< \fIfile\fP)\fR.
3132
When the old-style backquote form of substitution is used,
3133
backslash retains its literal meaning except when followed by
3138
The first backquote not preceded by a backslash terminates the
3139
command substitution.
3140
When using the $(\^\fIcommand\fP\|) form, all characters between the
3141
parentheses make up the command; none are treated specially.
3143
Command substitutions may be nested. To nest when using the backquoted form,
3144
escape the inner backquotes with backslashes.
3146
If the substitution appears within double quotes, word splitting and
3147
pathname expansion are not performed on the results.
3148
.SS Arithmetic Expansion
3150
Arithmetic expansion allows the evaluation of an arithmetic expression
3151
and the substitution of the result. The format for arithmetic expansion is:
3154
\fB$((\fP\fIexpression\fP\fB))\fP
3157
The old format \fB$[\fP\fIexpression\fP\fB]\fP is deprecated and will
3158
be removed in upcoming versions of bash.
3162
is treated as if it were within double quotes, but a double quote
3163
inside the parentheses is not treated specially.
3164
All tokens in the expression undergo parameter and variable expansion,
3165
command substitution, and quote removal.
3166
The result is treated as the arithmetic expression to be evaluated.
3167
Arithmetic expansions may be nested.
3169
The evaluation is performed according to the rules listed below under
3171
.BR "ARITHMETIC EVALUATION" .
3176
prints a message indicating failure and no substitution occurs.
3177
.SS Process Substitution
3179
\fIProcess substitution\fP is supported on systems that support named
3180
pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
3181
It takes the form of
3182
\fB<(\fP\fIlist\^\fP\fB)\fP
3184
\fB>(\fP\fIlist\^\fP\fB)\fP.
3185
The process \fIlist\fP is run with its input or output connected to a
3186
\fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
3187
passed as an argument to the current command as the result of the
3188
expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
3189
the file will provide input for \fIlist\fP. If the
3190
\fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
3191
argument should be read to obtain the output of \fIlist\fP.
3193
When available, process substitution is performed
3194
simultaneously with parameter and variable expansion,
3195
command substitution,
3196
and arithmetic expansion.
3199
The shell scans the results of
3200
parameter expansion,
3201
command substitution,
3203
arithmetic expansion
3204
that did not occur within double quotes for
3205
.IR "word splitting" .
3207
The shell treats each character of
3210
as a delimiter, and splits the results of the other
3211
expansions into words using these characters as field terminators.
3217
.BR <space><tab><newline> ,
3224
at the beginning and end of the results of the previous
3225
expansions are ignored, and
3229
characters not at the beginning or end serves to delimit words.
3233
has a value other than the default, then sequences of
3234
the whitespace characters
3238
are ignored at the beginning and end of the
3239
word, as long as the whitespace character is in the
3246
whitespace character).
3253
whitespace, along with any adjacent
3256
whitespace characters, delimits a field.
3260
whitespace characters is also treated as a delimiter.
3264
is null, no word splitting occurs.
3266
Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) are retained.
3267
Unquoted implicit null arguments, resulting from the expansion of
3268
parameters that have no values, are removed.
3269
If a parameter with no value is expanded within double quotes, a
3270
null argument results and is retained.
3272
Note that if no expansion occurs, no splitting
3274
.SS Pathname Expansion
3276
After word splitting,
3279
option has been set,
3281
scans each word for the characters
3286
If one of these characters appears, then the word is
3289
and replaced with an alphabetically sorted list of
3290
filenames matching the pattern
3293
.B "Pattern Matching"
3295
If no matching filenames are found,
3296
and the shell option
3298
is not enabled, the word is left unchanged.
3301
option is set, and no matches are found,
3302
the word is removed.
3305
shell option is set, and no matches are found, an error message
3306
is printed and the command is not executed.
3309
is enabled, the match is performed without regard to the case
3310
of alphabetic characters.
3311
When a pattern is used for pathname expansion,
3314
at the start of a name or immediately following a slash
3315
must be matched explicitly, unless the shell option
3318
When matching a pathname, the slash character must always be
3322
character is not treated specially.
3323
See the description of
3327
.B SHELL BUILTIN COMMANDS
3328
for a description of the
3339
shell variable may be used to restrict the set of filenames matching a
3344
is set, each matching filename that also matches one of the patterns in
3347
is removed from the list of matches.
3352
are always ignored when
3355
is set and not null. However, setting
3358
to a non-null value has the effect of enabling the
3360
shell option, so all other filenames beginning with a
3363
To get the old behavior of ignoring filenames beginning with a
3367
one of the patterns in
3372
option is disabled when
3377
\fBPattern Matching\fP
3379
Any character that appears in a pattern, other than the special pattern
3380
characters described below, matches itself. The NUL character may not
3381
occur in a pattern. A backslash escapes the following character; the
3382
escaping backslash is discarded when matching.
3383
The special pattern characters must be quoted if
3384
they are to be matched literally.
3386
The special pattern characters have the following meanings:
3392
Matches any string, including the null string.
3393
When the \fBglobstar\fP shell option is enabled, and \fB*\fP is used in
3394
a pathname expansion context, two adjacent \fB*\fPs used as a single
3395
pattern will match all files and zero or more directories and
3397
If followed by a \fB/\fP, two adjacent \fB*\fPs will match only directories
3401
Matches any single character.
3404
Matches any one of the enclosed characters. A pair of characters
3405
separated by a hyphen denotes a
3406
\fIrange expression\fP;
3407
any character that falls between those two characters, inclusive,
3408
using the current locale's collating sequence and character set,
3409
is matched. If the first character following the
3415
then any character not enclosed is matched.
3416
The sorting order of characters in range expressions is determined by
3417
the current locale and the values of the
3423
shell variables, if set.
3424
To obtain the traditional interpretation of range expressions, where
3437
may be matched by including it as the first or last character
3441
may be matched by including it as the first character
3450
\fIcharacter classes\fP can be specified using the syntax
3451
\fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
3452
following classes defined in the POSIX standard:
3456
.if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3457
.if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3459
A character class matches any character belonging to that class.
3460
The \fBword\fP character class matches letters, digits, and the character _.
3468
an \fIequivalence class\fP can be specified using the syntax
3469
\fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
3470
same collation weight (as defined by the current locale) as
3471
the character \fIc\fP.
3479
the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
3485
If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
3486
builtin, several extended pattern matching operators are recognized.
3487
In the following description, a \fIpattern-list\fP is a list of one
3488
or more patterns separated by a \fB|\fP.
3489
Composite patterns may be formed using one or more of the following
3495
\fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
3496
Matches zero or one occurrence of the given patterns
3498
\fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
3499
Matches zero or more occurrences of the given patterns
3501
\fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
3502
Matches one or more occurrences of the given patterns
3504
\fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
3505
Matches one of the given patterns
3507
\fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
3508
Matches anything except one of the given patterns
3513
After the preceding expansions, all unquoted occurrences of the
3517
and \^\f3"\fP\^ that did not result from one of the above
3518
expansions are removed.
3520
Before a command is executed, its input and output
3523
using a special notation interpreted by the shell.
3524
Redirection allows commands' file handles to be
3525
duplicated, opened, closed,
3526
made to refer to different files,
3527
and can change the files the command reads from and writes to.
3528
Redirection may also be used to modify file handles in the
3529
current shell execution environment.
3530
The following redirection
3531
operators may precede or appear anywhere within a
3535
Redirections are processed in the order they appear, from
3538
Each redirection that may be preceded by a file descriptor number
3539
may instead be preceded by a word of the form {\fIvarname\fP}.
3540
In this case, for each redirection operator except
3541
>&- and <&-, the shell will allocate a file descriptor greater
3542
than or equal to 10 and assign it to \fIvarname\fP.
3543
If >&- or <&- is preceded
3544
by {\fIvarname\fP}, the value of \fIvarname\fP defines the file
3545
descriptor to close.
3547
In the following descriptions, if the file descriptor number is
3548
omitted, and the first character of the redirection operator is
3550
the redirection refers to the standard input (file descriptor
3551
0). If the first character of the redirection operator is
3553
the redirection refers to the standard output (file descriptor
3556
The word following the redirection operator in the following
3557
descriptions, unless otherwise noted, is subjected to
3558
brace expansion, tilde expansion, parameter and variable expansion,
3559
command substitution, arithmetic expansion, quote removal,
3560
pathname expansion, and word splitting.
3561
If it expands to more than one word,
3565
Note that the order of redirections is significant. For example,
3569
ls \fB>\fP dirlist 2\fB>&\fP1
3572
directs both standard output and standard error to the file
3577
ls 2\fB>&\fP1 \fB>\fP dirlist
3580
directs only the standard output to file
3582
because the standard error was duplicated from the standard output
3583
before the standard output was redirected to
3586
\fBBash\fP handles several filenames specially when they are used in
3587
redirections, as described in the following table:
3593
If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
3596
File descriptor 0 is duplicated.
3599
File descriptor 1 is duplicated.
3602
File descriptor 2 is duplicated.
3604
.B /dev/tcp/\fIhost\fP/\fIport\fP
3605
If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3606
is an integer port number or service name, \fBbash\fP attempts to open
3607
the corresponding TCP socket.
3609
.B /dev/udp/\fIhost\fP/\fIport\fP
3610
If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3611
is an integer port number or service name, \fBbash\fP attempts to open
3612
the corresponding UDP socket.
3616
A failure to open or create a file causes the redirection to fail.
3618
Redirections using file descriptors greater than 9 should be used with
3619
care, as they may conflict with file descriptors the shell uses
3621
.SS Redirecting Input
3623
Redirection of input causes the file whose name results from
3626
to be opened for reading on file descriptor
3628
or the standard input (file descriptor 0) if
3632
The general format for redirecting input is:
3635
[\fIn\fP]\fB<\fP\fIword\fP
3637
.SS Redirecting Output
3639
Redirection of output causes the file whose name results from
3642
to be opened for writing on file descriptor
3644
or the standard output (file descriptor 1) if
3646
is not specified. If the file does not exist it is created;
3647
if it does exist it is truncated to zero size.
3649
The general format for redirecting output is:
3652
[\fIn\fP]\fB>\fP\fIword\fP
3655
If the redirection operator is
3661
builtin has been enabled, the redirection will fail if the file
3662
whose name results from the expansion of \fIword\fP exists and is
3664
If the redirection operator is
3666
or the redirection operator is
3672
builtin command is not enabled, the redirection is attempted even
3673
if the file named by \fIword\fP exists.
3674
.SS Appending Redirected Output
3676
Redirection of output in this fashion
3677
causes the file whose name results from
3680
to be opened for appending on file descriptor
3682
or the standard output (file descriptor 1) if
3684
is not specified. If the file does not exist it is created.
3686
The general format for appending output is:
3689
[\fIn\fP]\fB>>\fP\fIword\fP
3692
.SS Redirecting Standard Output and Standard Error
3694
This construct allows both the
3695
standard output (file descriptor 1) and
3696
the standard error output (file descriptor 2)
3697
to be redirected to the file whose name is the
3701
There are two formats for redirecting standard output and
3712
Of the two forms, the first is preferred.
3713
This is semantically equivalent to
3716
\fB>\fP\fIword\fP 2\fB>&\fP1
3719
When using the second form, \fIword\fP may not expand to a number or
3720
\fB\-\fP. If it does, other redirection operators apply
3721
(see \fBDuplicating File Descriptors\fP below) for compatibility
3723
.SS Appending Standard Output and Standard Error
3725
This construct allows both the
3726
standard output (file descriptor 1) and
3727
the standard error output (file descriptor 2)
3728
to be appended to the file whose name is the
3732
The format for appending standard output and standard error is:
3738
This is semantically equivalent to
3741
\fB>>\fP\fIword\fP 2\fB>&\fP1
3744
(see \fBDuplicating File Descriptors\fP below).
3747
This type of redirection instructs the shell to read input from the
3748
current source until a line containing only
3750
(with no trailing blanks)
3752
the lines read up to that point are then used as the standard
3753
input for a command.
3755
The format of here-documents is:
3759
\fB<<\fP[\fB\-\fP]\fIword\fP
3765
No parameter and variable expansion, command substitution,
3766
arithmetic expansion, or pathname expansion is performed on
3768
If any characters in
3772
is the result of quote removal on
3774
and the lines in the here-document are not expanded.
3775
If \fIword\fP is unquoted,
3776
all lines of the here-document are subjected to
3777
parameter expansion, command substitution, and arithmetic expansion,
3778
the character sequence
3782
must be used to quote the characters
3788
If the redirection operator is
3790
then all leading tab characters are stripped from input lines and the
3794
here-documents within shell scripts to be indented in a
3797
A variant of here documents, the format is:
3805
The \fIword\fP undergoes
3806
brace expansion, tilde expansion, parameter and variable expansion,
3807
command substitution, arithmetic expansion, and quote removal.
3808
Pathname expansion and word splitting are not performed.
3809
The result is supplied as a single string to the command on its
3811
.SS "Duplicating File Descriptors"
3813
The redirection operator
3816
[\fIn\fP]\fB<&\fP\fIword\fP
3819
is used to duplicate input file descriptors.
3822
expands to one or more digits, the file descriptor denoted by
3824
is made to be a copy of that file descriptor.
3827
do not specify a file descriptor open for input, a redirection error occurs.
3836
is not specified, the standard input (file descriptor 0) is used.
3841
[\fIn\fP]\fB>&\fP\fIword\fP
3844
is used similarly to duplicate output file descriptors. If
3846
is not specified, the standard output (file descriptor 1) is used.
3849
do not specify a file descriptor open for output, a redirection error occurs.
3857
As a special case, if \fIn\fP is omitted, and \fIword\fP does not
3858
expand to one or more digits or \fB\-\fP, the standard output and standard
3859
error are redirected as described previously.
3860
.SS "Moving File Descriptors"
3862
The redirection operator
3865
[\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
3868
moves the file descriptor \fIdigit\fP to file descriptor
3870
or the standard input (file descriptor 0) if \fIn\fP is not specified.
3871
\fIdigit\fP is closed after being duplicated to \fIn\fP.
3873
Similarly, the redirection operator
3876
[\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
3879
moves the file descriptor \fIdigit\fP to file descriptor
3881
or the standard output (file descriptor 1) if \fIn\fP is not specified.
3882
.SS "Opening File Descriptors for Reading and Writing"
3884
The redirection operator
3887
[\fIn\fP]\fB<>\fP\fIword\fP
3890
causes the file whose name is the expansion of
3892
to be opened for both reading and writing on file descriptor
3894
or on file descriptor 0 if
3896
is not specified. If the file does not exist, it is created.
3898
\fIAliases\fP allow a string to be substituted for a word when it is used
3899
as the first word of a simple command.
3900
The shell maintains a list of aliases that may be set and unset with the
3904
builtin commands (see
3906
.B SHELL BUILTIN COMMANDS
3908
The first word of each simple command, if unquoted,
3909
is checked to see if it has an
3910
alias. If so, that word is replaced by the text of the alias.
3911
The characters \fB/\fP, \fB$\fP, \fB\`\fP, and \fB=\fP and
3912
any of the shell \fImetacharacters\fP or quoting characters
3913
listed above may not appear in an alias name.
3914
The replacement text may contain any valid shell input,
3915
including shell metacharacters.
3916
The first word of the replacement text is tested
3917
for aliases, but a word that is identical to an alias being expanded
3918
is not expanded a second time.
3919
This means that one may alias
3925
does not try to recursively expand the replacement text.
3926
If the last character of the alias value is a
3928
then the next command
3929
word following the alias is also checked for alias expansion.
3931
Aliases are created and listed with the
3933
command, and removed with the
3937
There is no mechanism for using arguments in the replacement text.
3938
If arguments are needed, a shell function should be used (see
3943
Aliases are not expanded when the shell is not interactive, unless
3946
shell option is set using
3948
(see the description of
3952
\fBSHELL BUILTIN COMMANDS\fP
3955
The rules concerning the definition and use of aliases are
3958
always reads at least one complete line
3959
of input before executing any
3960
of the commands on that line. Aliases are expanded when a
3961
command is read, not when it is executed. Therefore, an
3962
alias definition appearing on the same line as another
3963
command does not take effect until the next line of input is read.
3964
The commands following the alias definition
3965
on that line are not affected by the new alias.
3966
This behavior is also an issue when functions are executed.
3967
Aliases are expanded when a function definition is read,
3968
not when the function is executed, because a function definition
3969
is itself a compound command. As a consequence, aliases
3970
defined in a function are not available until after that
3971
function is executed. To be safe, always put
3972
alias definitions on a separate line, and do not use
3974
in compound commands.
3976
For almost every purpose, aliases are superseded by
3979
A shell function, defined as described above under
3981
.BR "SHELL GRAMMAR" ,
3982
stores a series of commands for later execution.
3983
When the name of a shell function is used as a simple command name,
3984
the list of commands associated with that function name is executed.
3985
Functions are executed in the context of the
3986
current shell; no new process is created to interpret
3987
them (contrast this with the execution of a shell script).
3988
When a function is executed, the arguments to the
3989
function become the positional parameters
3990
during its execution.
3991
The special parameter
3993
is updated to reflect the change. Special parameter \fB0\fP
3995
The first element of the
3998
variable is set to the name of the function while the function
4001
All other aspects of the shell execution
4002
environment are identical between a function and its caller
4003
with these exceptions: the
4008
traps (see the description of the
4012
.B SHELL BUILTIN COMMANDS
4013
below) are not inherited unless the function has been given the
4014
\fBtrace\fP attribute (see the description of the
4017
builtin below) or the
4018
\fB\-o functrace\fP shell option has been enabled with
4019
the \fBset\fP builtin
4020
(in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps),
4024
trap is not inherited unless the \fB\-o errtrace\fP shell option has
4027
Variables local to the function may be declared with the
4029
builtin command. Ordinarily, variables and their values
4030
are shared between the function and its caller.
4032
The \fBFUNCNEST\fP variable, if set to a numeric value greater
4033
than 0, defines a maximum function nesting level. Function
4034
invocations that exceed the limit cause the entire command to
4037
If the builtin command
4039
is executed in a function, the function completes and
4040
execution resumes with the next command after the function
4042
Any command associated with the \fBRETURN\fP trap is executed
4043
before execution resumes.
4044
When a function completes, the values of the
4045
positional parameters and the special parameter
4047
are restored to the values they had prior to the function's
4050
Function names and definitions may be listed with the
4056
builtin commands. The
4062
will list the function names only
4063
(and optionally the source file and line number, if the \fBextdebug\fP
4064
shell option is enabled).
4065
Functions may be exported so that subshells
4066
automatically have them defined with the
4071
A function definition may be deleted using the \fB\-f\fP option to
4075
Note that shell functions and variables with the same name may result
4076
in multiple identically-named entries in the environment passed to the
4078
Care should be taken in cases where this may cause a problem.
4080
Functions may be recursive.
4081
The \fBFUNCNEST\fP variable may be used to limit the depth of the
4082
function call stack and restrict the number of function invocations.
4083
By default, no limit is imposed on the number of recursive calls.
4084
.SH "ARITHMETIC EVALUATION"
4085
The shell allows arithmetic expressions to be evaluated, under
4086
certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
4087
commands and \fBArithmetic Expansion\fP).
4088
Evaluation is done in fixed-width integers with no check for overflow,
4089
though division by 0 is trapped and flagged as an error.
4090
The operators and their precedence, associativity, and values
4091
are the same as in the C language.
4092
The following list of operators is grouped into levels of
4093
equal-precedence operators.
4094
The levels are listed in order of decreasing precedence.
4098
.B \fIid\fP++ \fIid\fP\-\-
4099
variable post-increment and post-decrement
4101
.B ++\fIid\fP \-\-\fIid\fP
4102
variable pre-increment and pre-decrement
4105
unary minus and plus
4108
logical and bitwise negation
4114
multiplication, division, remainder
4117
addition, subtraction
4120
left and right bitwise shifts
4126
equality and inequality
4132
bitwise exclusive OR
4143
.B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
4144
conditional operator
4146
.B = *= /= %= += \-= <<= >>= &= ^= |=
4149
.B \fIexpr1\fP , \fIexpr2\fP
4153
Shell variables are allowed as operands; parameter expansion is
4154
performed before the expression is evaluated.
4155
Within an expression, shell variables may also be referenced by name
4156
without using the parameter expansion syntax.
4157
A shell variable that is null or unset evaluates to 0 when referenced
4158
by name without using the parameter expansion syntax.
4159
The value of a variable is evaluated as an arithmetic expression
4160
when it is referenced, or when a variable which has been given the
4161
\fIinteger\fP attribute using \fBdeclare -i\fP is assigned a value.
4162
A null value evaluates to 0.
4163
A shell variable need not have its \fIinteger\fP attribute
4164
turned on to be used in an expression.
4166
Constants with a leading 0 are interpreted as octal numbers.
4167
A leading 0x or 0X denotes hexadecimal.
4168
Otherwise, numbers take the form [\fIbase#\fP]n, where the optional \fIbase\fP
4169
is a decimal number between 2 and 64 representing the arithmetic
4170
base, and \fIn\fP is a number in that base.
4171
If \fIbase#\fP is omitted, then base 10 is used.
4172
When specifying \fIn\fP,
4173
the digits greater< than 9 are represented by the lowercase letters,
4174
the uppercase letters, @, and _, in that order.
4175
If \fIbase\fP is less than or equal to 36, lowercase and uppercase
4176
letters may be used interchangeably to represent numbers between 10
4179
Operators are evaluated in order of precedence. Sub-expressions in
4180
parentheses are evaluated first and may override the precedence
4182
.SH "CONDITIONAL EXPRESSIONS"
4183
Conditional expressions are used by the \fB[[\fP compound command and
4184
the \fBtest\fP and \fB[\fP builtin commands to test file attributes
4185
and perform string and arithmetic comparisons.
4186
Expressions are formed from the following unary or binary primaries.
4187
If any \fIfile\fP argument to one of the primaries is of the form
4188
\fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
4189
If the \fIfile\fP argument to one of the primaries is one of
4190
\fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
4191
descriptor 0, 1, or 2, respectively, is checked.
4193
Unless otherwise specified, primaries that operate on files follow symbolic
4194
links and operate on the target of the link, rather than the link itself.
4197
When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
4198
lexicographically using the current locale.
4199
The \fBtest\fP command sorts using ASCII ordering.
4204
True if \fIfile\fP exists.
4207
True if \fIfile\fP exists and is a block special file.
4210
True if \fIfile\fP exists and is a character special file.
4213
True if \fIfile\fP exists and is a directory.
4216
True if \fIfile\fP exists.
4219
True if \fIfile\fP exists and is a regular file.
4222
True if \fIfile\fP exists and is set-group-id.
4225
True if \fIfile\fP exists and is a symbolic link.
4228
True if \fIfile\fP exists and its ``sticky'' bit is set.
4231
True if \fIfile\fP exists and is a named pipe (FIFO).
4234
True if \fIfile\fP exists and is readable.
4237
True if \fIfile\fP exists and has a size greater than zero.
4240
True if file descriptor
4242
is open and refers to a terminal.
4245
True if \fIfile\fP exists and its set-user-id bit is set.
4248
True if \fIfile\fP exists and is writable.
4251
True if \fIfile\fP exists and is executable.
4254
True if \fIfile\fP exists and is owned by the effective group id.
4257
True if \fIfile\fP exists and is a symbolic link.
4260
True if \fIfile\fP exists and has been modified since it was last read.
4263
True if \fIfile\fP exists and is owned by the effective user id.
4266
True if \fIfile\fP exists and is a socket.
4268
\fIfile1\fP \fB\-ef\fP \fIfile2\fP
4269
True if \fIfile1\fP and \fIfile2\fP refer to the same device and
4272
\fIfile1\fP \-\fBnt\fP \fIfile2\fP
4273
True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
4274
or if \fIfile1\fP exists and \fPfile2\fP does not.
4276
\fIfile1\fP \-\fBot\fP \fIfile2\fP
4277
True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
4278
and \fIfile1\fP does not.
4280
.B \-o \fIoptname\fP
4281
True if the shell option
4284
See the list of options under the description of the
4290
.B \-v \fIvarname\fP
4291
True if the shell variable
4293
is set (has been assigned a value).
4295
.B \-R \fIvarname\fP
4296
True if the shell variable
4298
is set and is a name reference.
4301
True if the length of \fIstring\fP is zero.
4308
True if the length of
4312
\fIstring1\fP \fB==\fP \fIstring2\fP
4315
\fIstring1\fP \fB=\fP \fIstring2\fP
4317
True if the strings are equal. \fB=\fP should be used
4318
with the \fBtest\fP command for POSIX conformance.
4319
When used with the \fB[[\fP command, this performs pattern matching as
4320
described above (\fBCompound Commands\fP).
4322
\fIstring1\fP \fB!=\fP \fIstring2\fP
4323
True if the strings are not equal.
4325
\fIstring1\fP \fB<\fP \fIstring2\fP
4326
True if \fIstring1\fP sorts before \fIstring2\fP lexicographically.
4328
\fIstring1\fP \fB>\fP \fIstring2\fP
4329
True if \fIstring1\fP sorts after \fIstring2\fP lexicographically.
4331
.I \fIarg1\fP \fBOP\fP \fIarg2\fP
4342
These arithmetic binary operators return true if \fIarg1\fP
4343
is equal to, not equal to, less than, less than or equal to,
4344
greater than, or greater than or equal to \fIarg2\fP, respectively.
4348
may be positive or negative integers.
4350
.SH "SIMPLE COMMAND EXPANSION"
4351
When a simple command is executed, the shell performs the following
4352
expansions, assignments, and redirections, from left to right.
4354
The words that the parser has marked as variable assignments (those
4355
preceding the command name) and redirections are saved for later
4358
The words that are not variable assignments or redirections are
4359
expanded. If any words remain after expansion, the first word
4360
is taken to be the name of the command and the remaining words are
4363
Redirections are performed as described above under
4367
The text after the \fB=\fP in each variable assignment undergoes tilde
4368
expansion, parameter expansion, command substitution, arithmetic expansion,
4369
and quote removal before being assigned to the variable.
4371
If no command name results, the variable assignments affect the current
4372
shell environment. Otherwise, the variables are added to the environment
4373
of the executed command and do not affect the current shell environment.
4374
If any of the assignments attempts to assign a value to a readonly variable,
4375
an error occurs, and the command exits with a non-zero status.
4377
If no command name results, redirections are performed, but do not
4378
affect the current shell environment. A redirection error causes the
4379
command to exit with a non-zero status.
4381
If there is a command name left after expansion, execution proceeds as
4382
described below. Otherwise, the command exits. If one of the expansions
4383
contained a command substitution, the exit status of the command is
4384
the exit status of the last command substitution performed. If there
4385
were no command substitutions, the command exits with a status of zero.
4386
.SH "COMMAND EXECUTION"
4387
After a command has been split into words, if it results in a
4388
simple command and an optional list of arguments, the following
4391
If the command name contains no slashes, the shell attempts to
4392
locate it. If there exists a shell function by that name, that
4393
function is invoked as described above in
4396
If the name does not match a function, the shell searches for
4397
it in the list of shell builtins. If a match is found, that
4400
If the name is neither a shell function nor a builtin,
4401
and contains no slashes,
4403
searches each element of the
4406
for a directory containing an executable file by that name.
4408
uses a hash table to remember the full pathnames of executable
4413
.B "SHELL BUILTIN COMMANDS"
4415
A full search of the directories in
4418
is performed only if the command is not found in the hash table.
4419
If the search is unsuccessful, the shell searches for a defined shell
4420
function named \fBcommand_not_found_handle\fP.
4421
If that function exists, it is invoked with the original command and
4422
the original command's arguments as its arguments, and the function's
4423
exit status becomes the exit status of the shell.
4424
If that function is not defined, the shell prints an error
4425
message and returns an exit status of 127.
4427
If the search is successful, or if the command name contains
4428
one or more slashes, the shell executes the named program in a
4429
separate execution environment.
4430
Argument 0 is set to the name given, and the remaining arguments
4431
to the command are set to the arguments given, if any.
4433
If this execution fails because the file is not in executable
4434
format, and the file is not a directory, it is assumed to be
4435
a \fIshell script\fP, a file
4436
containing shell commands. A subshell is spawned to execute
4437
it. This subshell reinitializes itself, so
4438
that the effect is as if a new shell had been invoked
4439
to handle the script, with the exception that the locations of
4440
commands remembered by the parent (see
4444
\fBSHELL BUILTIN COMMANDS\fP)
4445
are retained by the child.
4447
If the program is a file beginning with
4449
the remainder of the first line specifies an interpreter
4450
for the program. The shell executes the
4451
specified interpreter on operating systems that do not
4452
handle this executable format themselves. The arguments to the
4453
interpreter consist of a single optional argument following the
4454
interpreter name on the first line of the program, followed
4455
by the name of the program, followed by the command
4457
.SH COMMAND EXECUTION ENVIRONMENT
4458
The shell has an \fIexecution environment\fP, which consists of the
4461
open files inherited by the shell at invocation, as modified by
4462
redirections supplied to the \fBexec\fP builtin
4464
the current working directory as set by \fBcd\fP, \fBpushd\fP, or
4465
\fBpopd\fP, or inherited by the shell at invocation
4467
the file creation mode mask as set by \fBumask\fP or inherited from
4470
current traps set by \fBtrap\fP
4472
shell parameters that are set by variable assignment or with \fBset\fP
4473
or inherited from the shell's parent in the environment
4475
shell functions defined during execution or inherited from the shell's
4476
parent in the environment
4478
options enabled at invocation (either by default or with command-line
4479
arguments) or by \fBset\fP
4481
options enabled by \fBshopt\fP
4483
shell aliases defined with \fBalias\fP
4485
various process IDs, including those of background jobs, the value
4486
of \fB$$\fP, and the value of
4490
When a simple command other than a builtin or shell function
4491
is to be executed, it
4492
is invoked in a separate execution environment that consists of
4493
the following. Unless otherwise noted, the values are inherited
4497
the shell's open files, plus any modifications and additions specified
4498
by redirections to the command
4500
the current working directory
4502
the file creation mode mask
4504
shell variables and functions marked for export, along with variables
4505
exported for the command, passed in the environment
4507
traps caught by the shell are reset to the values inherited from the
4508
shell's parent, and traps ignored by the shell are ignored
4510
A command invoked in this separate environment cannot affect the
4511
shell's execution environment.
4513
Command substitution, commands grouped with parentheses,
4514
and asynchronous commands are invoked in a
4515
subshell environment that is a duplicate of the shell environment,
4516
except that traps caught by the shell are reset to the values
4517
that the shell inherited from its parent at invocation. Builtin
4518
commands that are invoked as part of a pipeline are also executed in a
4519
subshell environment. Changes made to the subshell environment
4520
cannot affect the shell's execution environment.
4522
Subshells spawned to execute command substitutions inherit the value of
4523
the \fB\-e\fP option from the parent shell. When not in \fIposix\fP mode,
4524
\fBbash\fP clears the \fB\-e\fP option in such subshells.
4526
If a command is followed by a \fB&\fP and job control is not active, the
4527
default standard input for the command is the empty file \fI/dev/null\fP.
4528
Otherwise, the invoked command inherits the file descriptors of the calling
4529
shell as modified by redirections.
4531
When a program is invoked it is given an array of strings
4535
\fIname\fP\-\fIvalue\fP pairs, of the form
4536
.IR "name\fR=\fPvalue" .
4538
The shell provides several ways to manipulate the environment.
4539
On invocation, the shell scans its own environment and
4540
creates a parameter for each name found, automatically marking
4543
to child processes. Executed commands inherit the environment.
4548
commands allow parameters and functions to be added to and
4549
deleted from the environment. If the value of a parameter
4550
in the environment is modified, the new value becomes part
4551
of the environment, replacing the old. The environment
4552
inherited by any executed command consists of the shell's
4553
initial environment, whose values may be modified in the shell,
4554
less any pairs removed by the
4556
command, plus any additions via the
4562
The environment for any
4564
or function may be augmented temporarily by prefixing it with
4565
parameter assignments, as described above in
4568
These assignment statements affect only the environment seen
4573
option is set (see the
4575
builtin command below), then
4577
parameter assignments are placed in the environment for a command,
4578
not just those that precede the command name.
4582
invokes an external command, the variable
4584
is set to the full filename of the command and passed to that
4585
command in its environment.
4588
The exit status of an executed command is the value returned by the
4589
\fIwaitpid\fP system call or equivalent function. Exit statuses
4590
fall between 0 and 255, though, as explained below, the shell may
4591
use values above 125 specially. Exit statuses from shell builtins and
4592
compound commands are also limited to this range. Under certain
4593
circumstances, the shell will use special values to indicate specific
4596
For the shell's purposes, a command which exits with a
4597
zero exit status has succeeded. An exit status of zero
4598
indicates success. A non-zero exit status indicates failure.
4599
When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
4600
the value of 128+\fIN\fP as the exit status.
4602
If a command is not found, the child process created to
4603
execute it returns a status of 127. If a command is found
4604
but is not executable, the return status is 126.
4606
If a command fails because of an error during expansion or redirection,
4607
the exit status is greater than zero.
4609
Shell builtin commands return a status of 0 (\fItrue\fP) if
4610
successful, and non-zero (\fIfalse\fP) if an error occurs
4612
All builtins return an exit status of 2 to indicate incorrect usage.
4614
\fBBash\fP itself returns the exit status of the last command
4615
executed, unless a syntax error occurs, in which case it exits
4616
with a non-zero value. See also the \fBexit\fP builtin
4619
When \fBbash\fP is interactive, in the absence of any traps, it ignores
4622
(so that \fBkill 0\fP does not kill an interactive shell),
4626
is caught and handled (so that the \fBwait\fP builtin is interruptible).
4627
In all cases, \fBbash\fP ignores
4630
If job control is in effect,
4641
Non-builtin commands run by \fBbash\fP have signal handlers
4642
set to the values inherited by the shell from its parent.
4643
When job control is not in effect, asynchronous commands
4650
in addition to these inherited handlers.
4651
Commands run as a result of command substitution ignore the
4652
keyboard-generated job control signals
4661
The shell exits by default upon receipt of a
4664
Before exiting, an interactive shell resends the
4667
to all jobs, running or stopped.
4668
Stopped jobs are sent
4671
to ensure that they receive the
4674
To prevent the shell from
4675
sending the signal to a particular job, it should be removed from the
4680
.B "SHELL BUILTIN COMMANDS"
4690
shell option has been set with
4696
to all jobs when an interactive login shell exits.
4698
If \fBbash\fP is waiting for a command to complete and receives a signal
4699
for which a trap has been set, the trap will not be executed until
4700
the command completes.
4701
When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
4702
builtin, the reception of a signal for which a trap has been set will
4703
cause the \fBwait\fP builtin to return immediately with an exit status
4704
greater than 128, immediately after which the trap is executed.
4707
refers to the ability to selectively stop (\fIsuspend\fP)
4708
the execution of processes and continue (\fIresume\fP)
4709
their execution at a later point. A user typically employs
4710
this facility via an interactive interface supplied jointly
4711
by the operating system kernel's terminal driver and
4714
The shell associates a
4716
with each pipeline. It keeps a table of currently executing
4717
jobs, which may be listed with the
4721
starts a job asynchronously (in the
4723
it prints a line that looks like:
4729
indicating that this job is job number 1 and that the process ID
4730
of the last process in the pipeline associated with this job is 25647.
4731
All of the processes in a single pipeline are members of the same job.
4735
abstraction as the basis for job control.
4737
To facilitate the implementation of the user interface to job
4738
control, the operating system maintains the notion of a \fIcurrent terminal
4739
process group ID\fP. Members of this process group (processes whose
4740
process group ID is equal to the current terminal process group ID)
4741
receive keyboard-generated signals such as
4744
These processes are said to be in the
4747
processes are those whose process group ID differs from the terminal's;
4748
such processes are immune to keyboard-generated signals.
4749
Only foreground processes are allowed to read from or, if the
4750
user so specifies with \f(CWstty tostop\fP, write to the
4752
Background processes which attempt to read from (write to when
4753
\f(CWstty tostop\fP is in effect) the
4756
.B SIGTTIN (SIGTTOU)
4757
signal by the kernel's terminal driver,
4758
which, unless caught, suspends the process.
4760
If the operating system on which
4765
contains facilities to use it.
4768
character (typically
4770
Control-Z) while a process is running
4771
causes that process to be stopped and returns control to
4774
.I "delayed suspend"
4775
character (typically
4777
Control-Y) causes the process to be stopped when it
4778
attempts to read input from the terminal, and control to
4781
The user may then manipulate the state of this job, using the
4783
command to continue it in the background, the
4785
command to continue it in the foreground, or
4788
command to kill it. A \fB^Z\fP takes effect immediately,
4789
and has the additional side effect of causing pending output
4790
and typeahead to be discarded.
4792
There are a number of ways to refer to a job in the shell.
4795
introduces a job specification (\fIjobspec\fP). Job number
4797
may be referred to as
4799
A job may also be referred to using a prefix of the name used to
4800
start it, or using a substring that appears in its command line.
4805
job. If a prefix matches more than one job,
4807
reports an error. Using
4809
on the other hand, refers to any job containing the string
4811
in its command line. If the substring matches more than one job,
4813
reports an error. The symbols
4817
refer to the shell's notion of the
4819
which is the last job stopped while it was in
4820
the foreground or started in the background.
4823
may be referenced using
4825
If there is only a single job, \fB%+\fP and \fB%\-\fP can both be used
4826
to refer to that job.
4827
In output pertaining to jobs (e.g., the output of the
4829
command), the current job is always flagged with a
4831
and the previous job with a
4833
A single % (with no accompanying job specification) also refers to the
4836
Simply naming a job can be used to bring it into the
4841
bringing job 1 from the background into the foreground.
4844
resumes job 1 in the background, equivalent to
4847
The shell learns immediately whenever a job changes state.
4850
waits until it is about to print a prompt before reporting
4851
changes in a job's status so as to not interrupt
4852
any other output. If the
4859
reports such changes immediately.
4863
is executed for each child that exits.
4865
If an attempt to exit
4867
is made while jobs are stopped (or, if the \fBcheckjobs\fP shell option has
4868
been enabled using the \fBshopt\fP builtin, running), the shell prints a
4869
warning message, and, if the \fBcheckjobs\fP option is enabled, lists the
4870
jobs and their statuses.
4873
command may then be used to inspect their status.
4874
If a second attempt to exit is made without an intervening command,
4875
the shell does not print another warning, and any stopped
4876
jobs are terminated.
4878
When executing interactively,
4880
displays the primary prompt
4883
when it is ready to read a command, and the secondary prompt
4886
when it needs more input to complete a command.
4888
allows these prompt strings to be customized by inserting a number of
4889
backslash-escaped special characters that are decoded as follows:
4894
an ASCII bell character (07)
4897
the date in "Weekday Month Date" format (e.g., "Tue May 26")
4899
.B \eD{\fIformat\fP}
4900
the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
4901
into the prompt string; an empty \fIformat\fP results in a locale-specific
4902
time representation. The braces are required
4905
an ASCII escape character (033)
4908
the hostname up to the first `.'
4914
the number of jobs currently managed by the shell
4917
the basename of the shell's terminal device name
4926
the name of the shell, the basename of
4928
(the portion following the final slash)
4931
the current time in 24-hour HH:MM:SS format
4934
the current time in 12-hour HH:MM:SS format
4937
the current time in 12-hour am/pm format
4940
the current time in 24-hour HH:MM format
4943
the username of the current user
4946
the version of \fBbash\fP (e.g., 2.00)
4949
the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
4952
the current working directory, with
4955
abbreviated with a tilde
4956
(uses the value of the
4962
the basename of the current working directory, with
4965
abbreviated with a tilde
4968
the history number of this command
4971
the command number of this command
4974
if the effective UID is 0, a
4980
the character corresponding to the octal number \fInnn\fP
4986
begin a sequence of non-printing characters, which could be used to
4987
embed a terminal control sequence into the prompt
4990
end a sequence of non-printing characters
4994
The command number and the history number are usually different:
4995
the history number of a command is its position in the history
4996
list, which may include commands restored from the history file
5000
below), while the command number is the position in the sequence
5001
of commands executed during the current shell session.
5002
After the string is decoded, it is expanded via
5003
parameter expansion, command substitution, arithmetic
5004
expansion, and quote removal, subject to the value of the
5006
shell option (see the description of the
5010
.B "SHELL BUILTIN COMMANDS"
5013
This is the library that handles reading input when using an interactive
5016
option is given at shell invocation.
5017
Line editing is also used when using the \fB\-e\fP option to the
5019
By default, the line editing commands are similar to those of Emacs.
5020
A vi-style line editing interface is also available.
5021
Line editing can be enabled at any time using the
5029
.B SHELL BUILTIN COMMANDS
5031
To turn off line editing after the shell is running, use the
5038
.SS "Readline Notation"
5040
In this section, the Emacs-style notation is used to denote
5041
keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
5042
means Control\-N. Similarly,
5044
keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
5047
key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
5050
key. This makes ESC the \fImeta prefix\fP.
5051
The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
5052
or press the Escape key
5053
then hold the Control key while pressing the
5057
Readline commands may be given numeric
5059
which normally act as a repeat count.
5060
Sometimes, however, it is the sign of the argument that is significant.
5061
Passing a negative argument to a command that acts in the forward
5062
direction (e.g., \fBkill\-line\fP) causes that command to act in a
5064
Commands whose behavior with arguments deviates from this are noted
5067
When a command is described as \fIkilling\fP text, the text
5068
deleted is saved for possible future retrieval
5069
(\fIyanking\fP). The killed text is saved in a
5070
\fIkill ring\fP. Consecutive kills cause the text to be
5071
accumulated into one unit, which can be yanked all at once.
5072
Commands which do not kill text separate the chunks of text
5074
.SS "Readline Initialization"
5076
Readline is customized by putting commands in an initialization
5077
file (the \fIinputrc\fP file).
5078
The name of this file is taken from the value of the
5081
variable. If that variable is unset, the default is
5083
When a program which uses the readline library starts up, the
5084
initialization file is read, and the key bindings and variables
5086
There are only a few basic constructs allowed in the
5087
readline initialization file.
5088
Blank lines are ignored.
5089
Lines beginning with a \fB#\fP are comments.
5090
Lines beginning with a \fB$\fP indicate conditional constructs.
5091
Other lines denote key bindings and variable settings.
5093
The default key-bindings may be changed with an
5096
Other programs that use this library may add their own commands
5099
For example, placing
5102
M\-Control\-u: universal\-argument
5106
C\-Meta\-u: universal\-argument
5110
would make M\-C\-u execute the readline command
5111
.IR universal\-argument .
5113
The following symbolic character names are recognized:
5126
In addition to command names, readline allows keys to be bound
5127
to a string that is inserted when the key is pressed (a \fImacro\fP).
5128
.SS "Readline Key Bindings"
5130
The syntax for controlling key bindings in the
5132
file is simple. All that is required is the name of the
5133
command or the text of a macro and a key sequence to which
5134
it should be bound. The name may be specified in one of two ways:
5135
as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
5136
prefixes, or as a key sequence.
5138
When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
5140
is the name of a key spelled out in English. For example:
5143
Control-u: universal\-argument
5145
Meta-Rubout: backward-kill-word
5147
Control-o: "> output"
5150
In the above example,
5152
is bound to the function
5153
.BR universal\-argument ,
5155
is bound to the function
5156
.BR backward\-kill\-word ,
5159
is bound to run the macro
5160
expressed on the right hand side (that is, to insert the text
5161
.if t \f(CW> output\fP
5165
In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
5169
above in that strings denoting
5170
an entire key sequence may be specified by placing the sequence
5171
within double quotes. Some GNU Emacs style key escapes can be
5172
used, as in the following example, but the symbolic character names
5176
"\eC\-u": universal\-argument
5178
"\eC\-x\eC\-r": re\-read\-init\-file
5180
"\ee[11~": "Function Key 1"
5185
is again bound to the function
5186
.BR universal\-argument .
5188
is bound to the function
5189
.BR re\-read\-init\-file ,
5192
is bound to insert the text
5193
.if t \f(CWFunction Key 1\fP.
5194
.if n ``Function Key 1''.
5196
The full set of GNU Emacs style escape sequences is
5220
In addition to the GNU Emacs style escape sequences, a second
5221
set of backslash escapes is available:
5250
the eight-bit character whose value is the octal value \fInnn\fP
5251
(one to three digits)
5254
the eight-bit character whose value is the hexadecimal value \fIHH\fP
5255
(one or two hex digits)
5259
When entering the text of a macro, single or double quotes must
5260
be used to indicate a macro definition.
5261
Unquoted text is assumed to be a function name.
5262
In the macro body, the backslash escapes described above are expanded.
5263
Backslash will quote any other character in the macro text,
5264
including " and \(aq.
5267
allows the current readline key bindings to be displayed or modified
5270
builtin command. The editing mode may be switched during interactive
5275
builtin command (see
5277
.B SHELL BUILTIN COMMANDS
5279
.SS "Readline Variables"
5281
Readline has variables that can be used to further customize its
5282
behavior. A variable may be set in the
5284
file with a statement of the form
5287
\fBset\fP \fIvariable\-name\fP \fIvalue\fP
5290
Except where noted, readline variables can take the values
5294
(without regard to case).
5295
Unrecognized variable names are ignored.
5296
When a variable value is read, empty or null values, "on" (case-insensitive),
5297
and "1" are equivalent to \fBOn\fP. All other values are equivalent to
5299
The variables and their default values are:
5303
.B bell\-style (audible)
5304
Controls what happens when readline wants to ring the terminal bell.
5305
If set to \fBnone\fP, readline never rings the bell. If set to
5306
\fBvisible\fP, readline uses a visible bell if one is available.
5307
If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
5309
.B bind\-tty\-special\-chars (On)
5310
If set to \fBOn\fP, readline attempts to bind the control characters
5311
treated specially by the kernel's terminal driver to their readline
5314
.B colored\-stats (Off)
5315
If set to \fBOn\fP, readline displays possible completions using different
5316
colors to indicate their file type.
5317
The color definitions are taken from the value of the \fBLS_COLORS\fP
5318
environment variable.
5320
.B comment\-begin (``#'')
5321
The string that is inserted when the readline
5323
command is executed.
5324
This command is bound to
5326
in emacs mode and to
5330
.B completion\-ignore\-case (Off)
5331
If set to \fBOn\fP, readline performs filename matching and completion
5332
in a case\-insensitive fashion.
5334
.B completion\-prefix\-display\-length (0)
5335
The length in characters of the common prefix of a list of possible
5336
completions that is displayed without modification. When set to a
5337
value greater than zero, common prefixes longer than this value are
5338
replaced with an ellipsis when displaying possible completions.
5340
.B completion\-query\-items (100)
5341
This determines when the user is queried about viewing
5342
the number of possible completions
5343
generated by the \fBpossible\-completions\fP command.
5344
It may be set to any integer value greater than or equal to
5345
zero. If the number of possible completions is greater than
5346
or equal to the value of this variable, the user is asked whether
5347
or not he wishes to view them; otherwise they are simply listed
5350
.B convert\-meta (On)
5351
If set to \fBOn\fP, readline will convert characters with the
5352
eighth bit set to an ASCII key sequence
5353
by stripping the eighth bit and prefixing an
5354
escape character (in effect, using escape as the \fImeta prefix\fP).
5356
.B disable\-completion (Off)
5357
If set to \fBOn\fP, readline will inhibit word completion. Completion
5358
characters will be inserted into the line as if they had been
5359
mapped to \fBself-insert\fP.
5361
.B editing\-mode (emacs)
5362
Controls whether readline begins with a set of key bindings similar
5363
to \fIEmacs\fP or \fIvi\fP.
5365
can be set to either
5370
.B echo\-control\-characters (On)
5371
When set to \fBOn\fP, on operating systems that indicate they support it,
5372
readline echoes a character corresponding to a signal generated from the
5375
.B enable\-keypad (Off)
5376
When set to \fBOn\fP, readline will try to enable the application
5377
keypad when it is called. Some systems need this to enable the
5380
.B enable\-meta\-key (On)
5381
When set to \fBOn\fP, readline will try to enable any meta modifier
5382
key the terminal claims to support when it is called. On many terminals,
5383
the meta key is used to send eight-bit characters.
5385
.B expand\-tilde (Off)
5386
If set to \fBOn\fP, tilde expansion is performed when readline
5387
attempts word completion.
5389
.B history\-preserve\-point (Off)
5390
If set to \fBOn\fP, the history code attempts to place point at the
5391
same location on each history line retrieved with \fBprevious-history\fP
5392
or \fBnext-history\fP.
5394
.B history\-size (0)
5395
Set the maximum number of history entries saved in the history list.
5396
If set to zero, any existing history entries are deleted and no new entries
5398
If set to a value less than zero, the number of history entries is not
5400
By default, the number of history entries is not limited.
5402
.B horizontal\-scroll\-mode (Off)
5403
When set to \fBOn\fP, makes readline use a single line for display,
5404
scrolling the input horizontally on a single screen line when it
5405
becomes longer than the screen width rather than wrapping to a new line.
5407
.B input\-meta (Off)
5408
If set to \fBOn\fP, readline will enable eight-bit input (that is,
5409
it will not strip the high bit from the characters it reads),
5410
regardless of what the terminal claims it can support. The name
5412
is a synonym for this variable.
5414
.B isearch\-terminators (``C\-[C\-J'')
5415
The string of characters that should terminate an incremental
5416
search without subsequently executing the character as a command.
5417
If this variable has not been given a value, the characters
5418
\fIESC\fP and \fIC\-J\fP will terminate an incremental search.
5421
Set the current readline keymap. The set of valid keymap names is
5422
\fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
5425
\fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
5426
equivalent to \fIemacs\-standard\fP. The default value is
5430
also affects the default keymap.
5432
.B keyseq\-timeout (500)
5433
Specifies the duration \fIreadline\fP will wait for a character when reading an
5434
ambiguous key sequence (one that can form a complete key sequence using
5435
the input read so far, or can take additional input to complete a longer
5437
If no input is received within the timeout, \fIreadline\fP will use the shorter
5438
but complete key sequence.
5439
The value is specified in milliseconds, so a value of 1000 means that
5440
\fIreadline\fP will wait one second for additional input.
5441
If this variable is set to a value less than or equal to zero, or to a
5442
non-numeric value, \fIreadline\fP will wait until another key is pressed to
5443
decide which key sequence to complete.
5445
.B mark\-directories (On)
5446
If set to \fBOn\fP, completed directory names have a slash
5449
.B mark\-modified\-lines (Off)
5450
If set to \fBOn\fP, history lines that have been modified are displayed
5451
with a preceding asterisk (\fB*\fP).
5453
.B mark\-symlinked\-directories (Off)
5454
If set to \fBOn\fP, completed names which are symbolic links to directories
5455
have a slash appended (subject to the value of
5456
\fBmark\-directories\fP).
5458
.B match\-hidden\-files (On)
5459
This variable, when set to \fBOn\fP, causes readline to match files whose
5460
names begin with a `.' (hidden files) when performing filename
5462
If set to \fBOff\fP, the leading `.' must be
5463
supplied by the user in the filename to be completed.
5465
.B menu\-complete\-display\-prefix (Off)
5466
If set to \fBOn\fP, menu completion displays the common prefix of the
5467
list of possible completions (which may be empty) before cycling through
5470
.B output\-meta (Off)
5471
If set to \fBOn\fP, readline will display characters with the
5472
eighth bit set directly rather than as a meta-prefixed escape
5475
.B page\-completions (On)
5476
If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
5477
to display a screenful of possible completions at a time.
5479
.B print\-completions\-horizontally (Off)
5480
If set to \fBOn\fP, readline will display completions with matches
5481
sorted horizontally in alphabetical order, rather than down the screen.
5483
.B revert\-all\-at\-newline (Off)
5484
If set to \fBOn\fP, readline will undo all changes to history lines
5485
before returning when \fBaccept\-line\fP is executed. By default,
5486
history lines may be modified and retain individual undo lists across
5487
calls to \fBreadline\fP.
5489
.B show\-all\-if\-ambiguous (Off)
5490
This alters the default behavior of the completion functions. If
5493
words which have more than one possible completion cause the
5494
matches to be listed immediately instead of ringing the bell.
5496
.B show\-all\-if\-unmodified (Off)
5497
This alters the default behavior of the completion functions in
5498
a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
5501
words which have more than one possible completion without any
5502
possible partial completion (the possible completions don't share
5503
a common prefix) cause the matches to be listed immediately instead
5504
of ringing the bell.
5506
.B show\-mode\-in\-prompt (Off)
5507
If set to \fBOn\fP, add a character to the beginning of the prompt
5508
indicating the editing mode: emacs (@), vi command (:) or vi
5511
.B skip\-completed\-text (Off)
5512
If set to \fBOn\fP, this alters the default completion behavior when
5513
inserting a single match into the line. It's only active when
5514
performing completion in the middle of a word. If enabled, readline
5515
does not insert characters from the completion that match characters
5516
after point in the word being completed, so portions of the word
5517
following the cursor are not duplicated.
5519
.B visible\-stats (Off)
5520
If set to \fBOn\fP, a character denoting a file's type as reported
5521
by \fIstat\fP(2) is appended to the filename when listing possible
5524
.SS "Readline Conditional Constructs"
5526
Readline implements a facility similar in spirit to the conditional
5527
compilation features of the C preprocessor which allows key
5528
bindings and variable settings to be performed as the result
5529
of tests. There are four parser directives used.
5533
construct allows bindings to be made based on the
5534
editing mode, the terminal being used, or the application using
5535
readline. The text of the test extends to the end of the line;
5536
no characters are required to isolate it.
5539
The \fBmode=\fP form of the \fB$if\fP directive is used to test
5540
whether readline is in emacs or vi mode.
5541
This may be used in conjunction
5542
with the \fBset keymap\fP command, for instance, to set bindings in
5543
the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
5544
readline is starting out in emacs mode.
5546
The \fBterm=\fP form may be used to include terminal-specific
5547
key bindings, perhaps to bind the key sequences output by the
5548
terminal's function keys. The word on the right side of the
5550
is tested against the both full name of the terminal and the portion
5551
of the terminal name before the first \fB\-\fP. This allows
5558
.IP \fBapplication\fP
5559
The \fBapplication\fP construct is used to include
5560
application-specific settings. Each program using the readline
5561
library sets the \fIapplication name\fP, and an initialization
5562
file can test for a particular value.
5563
This could be used to bind key sequences to functions useful for
5564
a specific program. For instance, the following command adds a
5565
key sequence that quotes the current or previous word in \fBbash\fP:
5570
# Quote the current or previous word
5571
"\eC\-xq": "\eeb\e"\eef\e""
5577
This command, as seen in the previous example, terminates an
5580
Commands in this branch of the \fB$if\fP directive are executed if
5583
This directive takes a single filename as an argument and reads commands
5584
and bindings from that file. For example, the following directive
5585
would read \fI/etc/inputrc\fP:
5589
\fB$include\fP \^ \fI/etc/inputrc\fP
5594
Readline provides commands for searching through the command history
5598
below) for lines containing a specified string.
5599
There are two search modes:
5602
.IR non-incremental .
5604
Incremental searches begin before the user has finished typing the
5606
As each character of the search string is typed, readline displays
5607
the next entry from the history matching the string typed so far.
5608
An incremental search requires only as many characters as needed to
5609
find the desired history entry.
5610
The characters present in the value of the \fBisearch-terminators\fP
5611
variable are used to terminate an incremental search.
5612
If that variable has not been assigned a value the Escape and
5613
Control-J characters will terminate an incremental search.
5614
Control-G will abort an incremental search and restore the original
5616
When the search is terminated, the history entry containing the
5617
search string becomes the current line.
5619
To find other matching entries in the history list, type Control-S or
5620
Control-R as appropriate.
5621
This will search backward or forward in the history for the next
5622
entry matching the search string typed so far.
5623
Any other key sequence bound to a readline command will terminate
5624
the search and execute that command.
5625
For instance, a \fInewline\fP will terminate the search and accept
5626
the line, thereby executing the command from the history list.
5628
Readline remembers the last incremental search string. If two
5629
Control-Rs are typed without any intervening characters defining a
5630
new search string, any remembered search string is used.
5632
Non-incremental searches read the entire search string before starting
5633
to search for matching history lines. The search string may be
5634
typed by the user or be part of the contents of the current line.
5635
.SS "Readline Command Names"
5637
The following is a list of the names of the commands and the default
5638
key sequences to which they are bound.
5639
Command names without an accompanying key sequence are unbound by default.
5640
In the following descriptions, \fIpoint\fP refers to the current cursor
5641
position, and \fImark\fP refers to a cursor position saved by the
5642
\fBset\-mark\fP command.
5643
The text between the point and mark is referred to as the \fIregion\fP.
5644
.SS Commands for Moving
5648
.B beginning\-of\-line (C\-a)
5649
Move to the start of the current line.
5651
.B end\-of\-line (C\-e)
5652
Move to the end of the line.
5654
.B forward\-char (C\-f)
5655
Move forward a character.
5657
.B backward\-char (C\-b)
5658
Move back a character.
5660
.B forward\-word (M\-f)
5661
Move forward to the end of the next word. Words are composed of
5662
alphanumeric characters (letters and digits).
5664
.B backward\-word (M\-b)
5665
Move back to the start of the current or previous word.
5666
Words are composed of alphanumeric characters (letters and digits).
5668
.B shell\-forward\-word
5669
Move forward to the end of the next word.
5670
Words are delimited by non-quoted shell metacharacters.
5672
.B shell\-backward\-word
5673
Move back to the start of the current or previous word.
5674
Words are delimited by non-quoted shell metacharacters.
5676
.B clear\-screen (C\-l)
5677
Clear the screen leaving the current line at the top of the screen.
5678
With an argument, refresh the current line without clearing the
5681
.B redraw\-current\-line
5682
Refresh the current line.
5684
.SS Commands for Manipulating the History
5688
.B accept\-line (Newline, Return)
5689
Accept the line regardless of where the cursor is. If this line is
5690
non-empty, add it to the history list according to the state of the
5693
variable. If the line is a modified history
5694
line, then restore the history line to its original state.
5696
.B previous\-history (C\-p)
5697
Fetch the previous command from the history list, moving back in
5700
.B next\-history (C\-n)
5701
Fetch the next command from the history list, moving forward in the
5704
.B beginning\-of\-history (M\-<)
5705
Move to the first line in the history.
5707
.B end\-of\-history (M\->)
5708
Move to the end of the input history, i.e., the line currently being
5711
.B reverse\-search\-history (C\-r)
5712
Search backward starting at the current line and moving `up' through
5713
the history as necessary. This is an incremental search.
5715
.B forward\-search\-history (C\-s)
5716
Search forward starting at the current line and moving `down' through
5717
the history as necessary. This is an incremental search.
5719
.B non\-incremental\-reverse\-search\-history (M\-p)
5720
Search backward through the history starting at the current line
5721
using a non-incremental search for a string supplied by the user.
5723
.B non\-incremental\-forward\-search\-history (M\-n)
5724
Search forward through the history using a non-incremental search for
5725
a string supplied by the user.
5727
.B history\-search\-forward
5728
Search forward through the history for the string of characters
5729
between the start of the current line and the point.
5730
This is a non-incremental search.
5732
.B history\-search\-backward
5733
Search backward through the history for the string of characters
5734
between the start of the current line and the point.
5735
This is a non-incremental search.
5737
.B yank\-nth\-arg (M\-C\-y)
5738
Insert the first argument to the previous command (usually
5739
the second word on the previous line) at point.
5742
insert the \fIn\fPth word from the previous command (the words
5743
in the previous command begin with word 0). A negative argument
5744
inserts the \fIn\fPth word from the end of the previous command.
5745
Once the argument \fIn\fP is computed, the argument is extracted
5746
as if the "!\fIn\fP" history expansion had been specified.
5749
yank\-last\-arg (M\-.\^, M\-_\^)
5750
Insert the last argument to the previous command (the last word of
5751
the previous history entry).
5752
With a numeric argument, behave exactly like \fByank\-nth\-arg\fP.
5753
Successive calls to \fByank\-last\-arg\fP move back through the history
5754
list, inserting the last word (or the word specified by the argument to
5755
the first call) of each line in turn.
5756
Any numeric argument supplied to these successive calls determines
5757
the direction to move through the history. A negative argument switches
5758
the direction through the history (back or forward).
5759
The history expansion facilities are used to extract the last word,
5760
as if the "!$" history expansion had been specified.
5762
.B shell\-expand\-line (M\-C\-e)
5763
Expand the line as the shell does. This
5764
performs alias and history expansion as well as all of the shell
5765
word expansions. See
5767
.B HISTORY EXPANSION
5768
below for a description of history expansion.
5770
.B history\-expand\-line (M\-^)
5771
Perform history expansion on the current line.
5774
.B HISTORY EXPANSION
5775
below for a description of history expansion.
5778
Perform history expansion on the current line and insert a space.
5781
.B HISTORY EXPANSION
5782
below for a description of history expansion.
5784
.B alias\-expand\-line
5785
Perform alias expansion on the current line.
5789
above for a description of alias expansion.
5791
.B history\-and\-alias\-expand\-line
5792
Perform history and alias expansion on the current line.
5794
.B insert\-last\-argument (M\-.\^, M\-_\^)
5795
A synonym for \fByank\-last\-arg\fP.
5797
.B operate\-and\-get\-next (C\-o)
5798
Accept the current line for execution and fetch the next line
5799
relative to the current line from the history for editing. Any
5800
argument is ignored.
5802
.B edit\-and\-execute\-command (C\-xC\-e)
5803
Invoke an editor on the current command line, and execute the result as shell
5805
\fBBash\fP attempts to invoke
5810
and \fIemacs\fP as the editor, in that order.
5812
.SS Commands for Changing Text
5816
.B \fIend\-of\-file\fP (usually C\-d)
5817
The character indicating end-of-file as set, for example, by
5820
If this character is read when there are no characters
5821
on the line, and point is at the beginning of the line, Readline
5822
interprets it as the end of input and returns
5826
.B delete\-char (C\-d)
5827
Delete the character at point.
5828
If this function is bound to the
5829
same character as the tty \fBEOF\fP character, as \fBC\-d\fP
5830
commonly is, see above for the effects.
5832
.B backward\-delete\-char (Rubout)
5833
Delete the character behind the cursor. When given a numeric argument,
5834
save the deleted text on the kill ring.
5836
.B forward\-backward\-delete\-char
5837
Delete the character under the cursor, unless the cursor is at the
5838
end of the line, in which case the character behind the cursor is
5841
.B quoted\-insert (C\-q, C\-v)
5842
Add the next character typed to the line verbatim. This is
5843
how to insert characters like \fBC\-q\fP, for example.
5845
.B tab\-insert (C\-v TAB)
5846
Insert a tab character.
5848
.B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
5849
Insert the character typed.
5851
.B transpose\-chars (C\-t)
5852
Drag the character before point forward over the character at point,
5853
moving point forward as well.
5854
If point is at the end of the line, then this transposes
5855
the two characters before point.
5856
Negative arguments have no effect.
5858
.B transpose\-words (M\-t)
5859
Drag the word before point past the word after point,
5860
moving point over that word as well.
5861
If point is at the end of the line, this transposes
5862
the last two words on the line.
5864
.B upcase\-word (M\-u)
5865
Uppercase the current (or following) word. With a negative argument,
5866
uppercase the previous word, but do not move point.
5868
.B downcase\-word (M\-l)
5869
Lowercase the current (or following) word. With a negative argument,
5870
lowercase the previous word, but do not move point.
5872
.B capitalize\-word (M\-c)
5873
Capitalize the current (or following) word. With a negative argument,
5874
capitalize the previous word, but do not move point.
5877
Toggle overwrite mode. With an explicit positive numeric argument,
5878
switches to overwrite mode. With an explicit non-positive numeric
5879
argument, switches to insert mode. This command affects only
5880
\fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
5881
Each call to \fIreadline()\fP starts in insert mode.
5882
In overwrite mode, characters bound to \fBself\-insert\fP replace
5883
the text at point rather than pushing the text to the right.
5884
Characters bound to \fBbackward\-delete\-char\fP replace the character
5885
before point with a space. By default, this command is unbound.
5887
.SS Killing and Yanking
5891
.B kill\-line (C\-k)
5892
Kill the text from point to the end of the line.
5894
.B backward\-kill\-line (C\-x Rubout)
5895
Kill backward to the beginning of the line.
5897
.B unix\-line\-discard (C\-u)
5898
Kill backward from point to the beginning of the line.
5899
The killed text is saved on the kill-ring.
5900
.\" There is no real difference between this and backward-kill-line
5902
.B kill\-whole\-line
5903
Kill all characters on the current line, no matter where point is.
5905
.B kill\-word (M\-d)
5906
Kill from point to the end of the current word, or if between
5907
words, to the end of the next word.
5908
Word boundaries are the same as those used by \fBforward\-word\fP.
5910
.B backward\-kill\-word (M\-Rubout)
5911
Kill the word behind point.
5912
Word boundaries are the same as those used by \fBbackward\-word\fP.
5914
.B shell\-kill\-word (M\-d)
5915
Kill from point to the end of the current word, or if between
5916
words, to the end of the next word.
5917
Word boundaries are the same as those used by \fBshell\-forward\-word\fP.
5919
.B shell\-backward\-kill\-word (M\-Rubout)
5920
Kill the word behind point.
5921
Word boundaries are the same as those used by \fBshell\-backward\-word\fP.
5923
.B unix\-word\-rubout (C\-w)
5924
Kill the word behind point, using white space as a word boundary.
5925
The killed text is saved on the kill-ring.
5927
.B unix\-filename\-rubout
5928
Kill the word behind point, using white space and the slash character
5929
as the word boundaries.
5930
The killed text is saved on the kill-ring.
5932
.B delete\-horizontal\-space (M\-\e)
5933
Delete all spaces and tabs around point.
5936
Kill the text in the current region.
5938
.B copy\-region\-as\-kill
5939
Copy the text in the region to the kill buffer.
5941
.B copy\-backward\-word
5942
Copy the word before point to the kill buffer.
5943
The word boundaries are the same as \fBbackward\-word\fP.
5945
.B copy\-forward\-word
5946
Copy the word following point to the kill buffer.
5947
The word boundaries are the same as \fBforward\-word\fP.
5950
Yank the top of the kill ring into the buffer at point.
5953
Rotate the kill ring, and yank the new top. Only works following
5958
.SS Numeric Arguments
5962
.B digit\-argument (M\-0, M\-1, ..., M\-\-)
5963
Add this digit to the argument already accumulating, or start a new
5964
argument. M\-\- starts a negative argument.
5966
.B universal\-argument
5967
This is another way to specify an argument.
5968
If this command is followed by one or more digits, optionally with a
5969
leading minus sign, those digits define the argument.
5970
If the command is followed by digits, executing
5971
.B universal\-argument
5972
again ends the numeric argument, but is otherwise ignored.
5973
As a special case, if this command is immediately followed by a
5974
character that is neither a digit or minus sign, the argument count
5975
for the next command is multiplied by four.
5976
The argument count is initially one, so executing this function the
5977
first time makes the argument count four, a second time makes the
5978
argument count sixteen, and so on.
5985
Attempt to perform completion on the text before point.
5987
attempts completion treating the text as a variable (if the
5988
text begins with \fB$\fP), username (if the text begins with
5989
\fB~\fP), hostname (if the text begins with \fB@\fP), or
5990
command (including aliases and functions) in turn. If none
5991
of these produces a match, filename completion is attempted.
5993
.B possible\-completions (M\-?)
5994
List the possible completions of the text before point.
5996
.B insert\-completions (M\-*)
5997
Insert all completions of the text before point
5998
that would have been generated by
5999
\fBpossible\-completions\fP.
6002
Similar to \fBcomplete\fP, but replaces the word to be completed
6003
with a single match from the list of possible completions.
6004
Repeated execution of \fBmenu\-complete\fP steps through the list
6005
of possible completions, inserting each match in turn.
6006
At the end of the list of completions, the bell is rung
6007
(subject to the setting of \fBbell\-style\fP)
6008
and the original text is restored.
6009
An argument of \fIn\fP moves \fIn\fP positions forward in the list
6010
of matches; a negative argument may be used to move backward
6012
This command is intended to be bound to \fBTAB\fP, but is unbound
6015
.B menu\-complete\-backward
6016
Identical to \fBmenu\-complete\fP, but moves backward through the list
6017
of possible completions, as if \fBmenu\-complete\fP had been given a
6018
negative argument. This command is unbound by default.
6020
.B delete\-char\-or\-list
6021
Deletes the character under the cursor if not at the beginning or
6022
end of the line (like \fBdelete\-char\fP).
6023
If at the end of the line, behaves identically to
6024
\fBpossible\-completions\fP.
6025
This command is unbound by default.
6027
.B complete\-filename (M\-/)
6028
Attempt filename completion on the text before point.
6030
.B possible\-filename\-completions (C\-x /)
6031
List the possible completions of the text before point,
6032
treating it as a filename.
6034
.B complete\-username (M\-~)
6035
Attempt completion on the text before point, treating
6038
.B possible\-username\-completions (C\-x ~)
6039
List the possible completions of the text before point,
6040
treating it as a username.
6042
.B complete\-variable (M\-$)
6043
Attempt completion on the text before point, treating
6044
it as a shell variable.
6046
.B possible\-variable\-completions (C\-x $)
6047
List the possible completions of the text before point,
6048
treating it as a shell variable.
6050
.B complete\-hostname (M\-@)
6051
Attempt completion on the text before point, treating
6054
.B possible\-hostname\-completions (C\-x @)
6055
List the possible completions of the text before point,
6056
treating it as a hostname.
6058
.B complete\-command (M\-!)
6059
Attempt completion on the text before point, treating
6060
it as a command name. Command completion attempts to
6061
match the text against aliases, reserved words, shell
6062
functions, shell builtins, and finally executable filenames,
6065
.B possible\-command\-completions (C\-x !)
6066
List the possible completions of the text before point,
6067
treating it as a command name.
6069
.B dynamic\-complete\-history (M\-TAB)
6070
Attempt completion on the text before point, comparing
6071
the text against lines from the history list for possible
6075
Attempt menu completion on the text before point, comparing
6076
the text against lines from the history list for possible
6079
.B complete\-into\-braces (M\-{)
6080
Perform filename completion and insert the list of possible completions
6081
enclosed within braces so the list is available to the shell (see
6089
.B start\-kbd\-macro (C\-x (\^)
6090
Begin saving the characters typed into the current keyboard macro.
6092
.B end\-kbd\-macro (C\-x )\^)
6093
Stop saving the characters typed into the current keyboard macro
6094
and store the definition.
6096
.B call\-last\-kbd\-macro (C\-x e)
6097
Re-execute the last keyboard macro defined, by making the characters
6098
in the macro appear as if typed at the keyboard.
6100
.B print\-last\-kbd\-macro ()
6101
Print the last keyboard macro defined in a format suitable for the
6108
.B re\-read\-init\-file (C\-x C\-r)
6109
Read in the contents of the \fIinputrc\fP file, and incorporate
6110
any bindings or variable assignments found there.
6113
Abort the current editing command and
6114
ring the terminal's bell (subject to the setting of
6117
.B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
6118
If the metafied character \fIx\fP is lowercase, run the command
6119
that is bound to the corresponding uppercase character.
6121
.B prefix\-meta (ESC)
6122
Metafy the next character typed.
6129
.B undo (C\-_, C\-x C\-u)
6130
Incremental undo, separately remembered for each line.
6132
.B revert\-line (M\-r)
6133
Undo all changes made to this line. This is like executing the
6135
command enough times to return the line to its initial state.
6137
.B tilde\-expand (M\-&)
6138
Perform tilde expansion on the current word.
6140
.B set\-mark (C\-@, M\-<space>)
6141
Set the mark to the point. If a
6142
numeric argument is supplied, the mark is set to that position.
6144
.B exchange\-point\-and\-mark (C\-x C\-x)
6145
Swap the point with the mark. The current cursor position is set to
6146
the saved position, and the old cursor position is saved as the mark.
6148
.B character\-search (C\-])
6149
A character is read and point is moved to the next occurrence of that
6150
character. A negative count searches for previous occurrences.
6152
.B character\-search\-backward (M\-C\-])
6153
A character is read and point is moved to the previous occurrence of that
6154
character. A negative count searches for subsequent occurrences.
6156
.B skip\-csi\-sequence
6157
Read enough characters to consume a multi-key sequence such as those
6158
defined for keys like Home and End. Such sequences begin with a
6159
Control Sequence Indicator (CSI), usually ESC\-[. If this sequence is
6160
bound to "\e[", keys producing such sequences will have no effect
6161
unless explicitly bound to a readline command, instead of inserting
6162
stray characters into the editing buffer. This is unbound by default,
6163
but usually bound to ESC\-[.
6165
.B insert\-comment (M\-#)
6166
Without a numeric argument, the value of the readline
6168
variable is inserted at the beginning of the current line.
6169
If a numeric argument is supplied, this command acts as a toggle: if
6170
the characters at the beginning of the line do not match the value
6171
of \fBcomment\-begin\fP, the value is inserted, otherwise
6172
the characters in \fBcomment\-begin\fP are deleted from the beginning of
6174
In either case, the line is accepted as if a newline had been typed.
6175
The default value of
6176
\fBcomment\-begin\fP causes this command to make the current line
6178
If a numeric argument causes the comment character to be removed, the line
6179
will be executed by the shell.
6181
.B glob\-complete\-word (M\-g)
6182
The word before point is treated as a pattern for pathname expansion,
6183
with an asterisk implicitly appended. This pattern is used to
6184
generate a list of matching filenames for possible completions.
6186
.B glob\-expand\-word (C\-x *)
6187
The word before point is treated as a pattern for pathname expansion,
6188
and the list of matching filenames is inserted, replacing the word.
6189
If a numeric argument is supplied, an asterisk is appended before
6192
.B glob\-list\-expansions (C\-x g)
6193
The list of expansions that would have been generated by
6194
.B glob\-expand\-word
6195
is displayed, and the line is redrawn.
6196
If a numeric argument is supplied, an asterisk is appended before
6200
Print all of the functions and their key bindings to the
6201
readline output stream. If a numeric argument is supplied,
6202
the output is formatted in such a way that it can be made part
6203
of an \fIinputrc\fP file.
6206
Print all of the settable readline variables and their values to the
6207
readline output stream. If a numeric argument is supplied,
6208
the output is formatted in such a way that it can be made part
6209
of an \fIinputrc\fP file.
6212
Print all of the readline key sequences bound to macros and the
6213
strings they output. If a numeric argument is supplied,
6214
the output is formatted in such a way that it can be made part
6215
of an \fIinputrc\fP file.
6217
.B display\-shell\-version (C\-x C\-v)
6218
Display version information about the current instance of
6221
.SS Programmable Completion
6223
When word completion is attempted for an argument to a command for
6224
which a completion specification (a \fIcompspec\fP) has been defined
6225
using the \fBcomplete\fP builtin (see
6227
.B "SHELL BUILTIN COMMANDS"
6228
below), the programmable completion facilities are invoked.
6230
First, the command name is identified.
6231
If the command word is the empty string (completion attempted at the
6232
beginning of an empty line), any compspec defined with
6233
the \fB\-E\fP option to \fBcomplete\fP is used.
6234
If a compspec has been defined for that command, the
6235
compspec is used to generate the list of possible completions for the word.
6236
If the command word is a full pathname, a compspec for the full
6237
pathname is searched for first.
6238
If no compspec is found for the full pathname, an attempt is made to
6239
find a compspec for the portion following the final slash.
6240
If those searches do not result in a compspec, any compspec defined with
6241
the \fB\-D\fP option to \fBcomplete\fP is used as the default.
6243
Once a compspec has been found, it is used to generate the list of
6245
If a compspec is not found, the default \fBbash\fP completion as
6246
described above under \fBCompleting\fP is performed.
6248
First, the actions specified by the compspec are used.
6249
Only matches which are prefixed by the word being completed are
6255
option is used for filename or directory name completion, the shell
6259
is used to filter the matches.
6261
Any completions specified by a pathname expansion pattern to the
6262
\fB\-G\fP option are generated next.
6263
The words generated by the pattern need not match the word
6268
shell variable is not used to filter the matches, but the
6273
Next, the string specified as the argument to the \fB\-W\fP option
6275
The string is first split using the characters in the
6278
special variable as delimiters.
6279
Shell quoting is honored.
6280
Each word is then expanded using
6281
brace expansion, tilde expansion, parameter and variable expansion,
6282
command substitution, and arithmetic expansion,
6283
as described above under
6286
The results are split using the rules described above under
6287
\fBWord Splitting\fP.
6288
The results of the expansion are prefix-matched against the word being
6289
completed, and the matching words become the possible completions.
6291
After these matches have been generated, any shell function or command
6292
specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
6293
When the command or function is invoked, the
6303
variables are assigned values as described above under
6304
\fBShell Variables\fP.
6305
If a shell function is being invoked, the
6311
variables are also set.
6312
When the function or command is invoked,
6313
the first argument (\fB$1\fP) is the name of the command whose arguments are
6315
the second argument (\fB$2\fP) is the word being completed,
6316
and the third argument (\fB$3\fP) is the word preceding the word being
6317
completed on the current command line.
6318
No filtering of the generated completions against the word being completed
6319
is performed; the function or command has complete freedom in generating
6322
Any function specified with \fB\-F\fP is invoked first.
6323
The function may use any of the shell facilities, including the
6324
\fBcompgen\fP builtin described below, to generate the matches.
6325
It must put the possible completions in the
6328
array variable, one per array element.
6330
Next, any command specified with the \fB\-C\fP option is invoked
6331
in an environment equivalent to command substitution.
6332
It should print a list of completions, one per line, to the
6334
Backslash may be used to escape a newline, if necessary.
6336
After all of the possible completions are generated, any filter
6337
specified with the \fB\-X\fP option is applied to the list.
6338
The filter is a pattern as used for pathname expansion; a \fB&\fP
6339
in the pattern is replaced with the text of the word being completed.
6340
A literal \fB&\fP may be escaped with a backslash; the backslash
6341
is removed before attempting a match.
6342
Any completion that matches the pattern will be removed from the list.
6343
A leading \fB!\fP negates the pattern; in this case any completion
6344
not matching the pattern will be removed.
6346
Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
6347
options are added to each member of the completion list, and the result is
6348
returned to the readline completion code as the list of possible
6351
If the previously-applied actions do not generate any matches, and the
6352
\fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
6353
compspec was defined, directory name completion is attempted.
6355
If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
6356
compspec was defined, directory name completion is attempted and any
6357
matches are added to the results of the other actions.
6359
By default, if a compspec is found, whatever it generates is returned
6360
to the completion code as the full set of possible completions.
6361
The default \fBbash\fP completions are not attempted, and the readline
6362
default of filename completion is disabled.
6363
If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
6364
the compspec was defined, the \fBbash\fP default completions are attempted
6365
if the compspec generates no matches.
6366
If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
6367
compspec was defined, readline's default completion will be performed
6368
if the compspec (and, if attempted, the default \fBbash\fP completions)
6369
generate no matches.
6371
When a compspec indicates that directory name completion is desired,
6372
the programmable completion functions force readline to append a slash
6373
to completed names which are symbolic links to directories, subject to
6374
the value of the \fBmark\-directories\fP readline variable, regardless
6375
of the setting of the \fBmark-symlinked\-directories\fP readline variable.
6377
There is some support for dynamically modifying completions. This is
6378
most useful when used in combination with a default completion specified
6379
with \fBcomplete -D\fP.
6380
It's possible for shell functions executed as completion
6381
handlers to indicate that completion should be retried by returning an
6382
exit status of 124. If a shell function returns 124, and changes
6383
the compspec associated with the command on which completion is being
6384
attempted (supplied as the first argument when the function is executed),
6385
programmable completion restarts from the beginning, with an
6386
attempt to find a new compspec for that command. This allows a set of
6387
completions to be built dynamically as completion is attempted, rather than
6388
being loaded all at once.
6390
For instance, assuming that there is a library of compspecs, each kept in a
6391
file corresponding to the name of the command, the following default
6392
completion function would load completions dynamically:
6394
\f(CW_completion_loader()
6398
. "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
6402
complete -D -F _completion_loader -o bashdefault -o default
6410
builtin is enabled, the shell provides access to the
6411
\fIcommand history\fP,
6412
the list of commands previously typed.
6416
variable is used as the
6417
number of commands to save in a history list.
6418
The text of the last
6421
commands (default 500) is saved. The shell
6422
stores each command in the history list prior to parameter and
6423
variable expansion (see
6426
above) but after history expansion is performed, subject to the
6427
values of the shell variables
6434
On startup, the history is initialized from the file named by
6438
(default \fI~/.bash_history\fP).
6439
The file named by the value of
6442
is truncated, if necessary, to contain no more than
6443
the number of lines specified by the value of
6446
If \fBHISTFILESIZE\fP is unset, or set to null, a non-numeric value,
6447
or a numeric value less than zero, the history file is not truncated.
6448
When the history file is read,
6449
lines beginning with the history comment character followed immediately
6450
by a digit are interpreted as timestamps for the preceding history line.
6451
These timestamps are optionally displayed depending on the value of the
6455
When a shell with history enabled exits, the last
6458
lines are copied from the history list to
6463
shell option is enabled
6464
(see the description of
6468
.B "SHELL BUILTIN COMMANDS"
6469
below), the lines are appended to the history file,
6470
otherwise the history file is overwritten.
6474
is unset, or if the history file is unwritable, the history is
6479
variable is set, time stamps are written to the history file, marked
6480
with the history comment character, so
6481
they may be preserved across shell sessions.
6482
This uses the history comment character to distinguish timestamps from
6483
other history lines.
6484
After saving the history, the history file is truncated
6485
to contain no more than
6491
is unset, or set to null, a non-numeric value,
6492
or a numeric value less than zero, the history file is not truncated.
6498
.B SHELL BUILTIN COMMANDS
6499
below) may be used to list or edit and re-execute a portion of
6503
builtin may be used to display or modify the history list and
6504
manipulate the history file.
6505
When using command-line editing, search commands
6506
are available in each editing mode that provide access to the
6509
The shell allows control over which commands are saved on the history
6516
variables may be set to cause the shell to save only a subset of the
6520
shell option, if enabled, causes the shell to attempt to save each
6521
line of a multi-line command in the same history entry, adding
6522
semicolons where necessary to preserve syntactic correctness.
6525
shell option causes the shell to save the command with embedded newlines
6526
instead of semicolons. See the description of the
6530
.B "SHELL BUILTIN COMMANDS"
6531
for information on setting and unsetting shell options.
6532
.SH "HISTORY EXPANSION"
6534
The shell supports a history expansion feature that
6535
is similar to the history expansion in
6537
This section describes what syntax features are available. This
6538
feature is enabled by default for interactive shells, and can be
6543
builtin command (see
6545
.B SHELL BUILTIN COMMANDS
6546
below). Non-interactive shells do not perform history expansion
6549
History expansions introduce words from the history list into
6550
the input stream, making it easy to repeat commands, insert the
6551
arguments to a previous command into the current input line, or
6552
fix errors in previous commands quickly.
6554
History expansion is performed immediately after a complete line
6555
is read, before the shell breaks it into words.
6556
It takes place in two parts.
6557
The first is to determine which line from the history list
6558
to use during substitution.
6559
The second is to select portions of that line for inclusion into
6561
The line selected from the history is the \fIevent\fP,
6562
and the portions of that line that are acted upon are \fIwords\fP.
6563
Various \fImodifiers\fP are available to manipulate the selected words.
6564
The line is broken into words in the same fashion as when reading input,
6565
so that several \fImetacharacter\fP-separated words surrounded by
6566
quotes are considered one word.
6567
History expansions are introduced by the appearance of the
6568
history expansion character, which is \^\fB!\fP\^ by default.
6569
Only backslash (\^\fB\e\fP\^) and single quotes can quote
6570
the history expansion character.
6572
Several characters inhibit history expansion if found immediately
6573
following the history expansion character, even if it is unquoted:
6574
space, tab, newline, carriage return, and \fB=\fP.
6575
If the \fBextglob\fP shell option is enabled, \fB(\fP will also
6578
Several shell options settable with the
6580
builtin may be used to tailor the behavior of history expansion.
6583
shell option is enabled (see the description of the
6587
is being used, history substitutions are not immediately passed to
6589
Instead, the expanded line is reloaded into the
6591
editing buffer for further modification.
6594
is being used, and the
6596
shell option is enabled, a failed history substitution will be reloaded
6599
editing buffer for correction.
6604
builtin command may be used to see what a history expansion will
6610
builtin may be used to add commands to the end of the history list
6611
without actually executing them, so that they are available for
6614
The shell allows control of the various characters used by the
6615
history expansion mechanism (see the description of
6618
.BR "Shell Variables" ).
6620
the history comment character to mark history timestamps when
6621
writing the history file.
6622
.SS Event Designators
6624
An event designator is a reference to a command line entry in the
6626
Unless the reference is absolute, events are relative to the current
6627
position in the history list.
6632
Start a history substitution, except when followed by a
6634
newline, carriage return, =
6635
or ( (when the \fBextglob\fP shell option is enabled using
6636
the \fBshopt\fP builtin).
6639
Refer to command line
6643
Refer to the current command minus
6647
Refer to the previous command. This is a synonym for `!\-1'.
6650
Refer to the most recent command preceding the current position in the
6651
history list starting with
6654
.B !?\fIstring\fR\fB[?]\fR
6655
Refer to the most recent command preceding the current position in the
6656
history list containing
6658
The trailing \fB?\fP may be omitted if
6660
is followed immediately by a newline.
6662
.B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
6663
Quick substitution. Repeat the previous command, replacing
6668
``!!:s/\fIstring1\fP/\fIstring2\fP/''
6669
(see \fBModifiers\fP below).
6672
The entire command line typed so far.
6674
.SS Word Designators
6676
Word designators are used to select desired words from the event.
6679
separates the event specification from the word designator.
6680
It may be omitted if the word designator begins with a
6687
Words are numbered from the beginning of the line,
6688
with the first word being denoted by 0 (zero).
6689
Words are inserted into the current line separated by single spaces.
6694
The zeroth word. For the shell, this is the command
6701
The first argument. That is, word 1.
6704
The last word. This is usually the last argument, but will expand to the
6705
zeroth word if there is only one word in the line.
6708
The word matched by the most recent `?\fIstring\fR?' search.
6711
A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
6714
All of the words but the zeroth. This is a synonym
6715
for `\fI1\-$\fP'. It is not an error to use
6717
if there is just one
6718
word in the event; the empty string is returned in that case.
6721
Abbreviates \fIx\-$\fP.
6724
Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
6727
If a word designator is supplied without an event specification, the
6728
previous command is used as the event.
6731
After the optional word designator, there may appear a sequence of
6732
one or more of the following modifiers, each preceded by a `:'.
6738
Remove a trailing filename component, leaving only the head.
6741
Remove all leading filename components, leaving the tail.
6744
Remove a trailing suffix of the form \fI.xxx\fP, leaving the
6748
Remove all but the trailing suffix.
6751
Print the new command but do not execute it.
6754
Quote the substituted words, escaping further substitutions.
6757
Quote the substituted words as with
6759
but break into words at
6763
.B s/\fIold\fP/\fInew\fP/
6766
for the first occurrence of
6768
in the event line. Any delimiter can be used in place of /. The
6769
final delimiter is optional if it is the last character of the
6770
event line. The delimiter may be quoted in
6774
with a single backslash. If & appears in
6778
A single backslash will quote the &. If
6780
is null, it is set to the last
6782
substituted, or, if no previous history substitutions took place,
6786
.B !?\fIstring\fR\fB[?]\fR
6790
Repeat the previous substitution.
6793
Cause changes to be applied over the entire event line. This is
6794
used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
6795
or `\fB:&\fP'. If used with
6796
`\fB:s\fP', any delimiter can be used
6797
in place of /, and the final delimiter is optional
6798
if it is the last character of the event line.
6799
An \fBa\fP may be used as a synonym for \fBg\fP.
6802
Apply the following `\fBs\fP' modifier once to each word in the event line.
6804
.SH "SHELL BUILTIN COMMANDS"
6805
.\" start of bash_builtins
6808
Unless otherwise noted, each builtin command documented in this
6809
section as accepting options preceded by
6813
to signify the end of the options.
6814
The \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP builtins
6815
do not accept options and do not treat \fB\-\-\fP specially.
6816
The \fBexit\fP, \fBlogout\fP, \fBbreak\fP, \fBcontinue\fP, \fBlet\fP,
6817
and \fBshift\fP builtins accept and process arguments beginning with
6818
\fB\-\fP without requiring \fB\-\-\fP.
6819
Other builtins that accept arguments but are not specified as accepting
6820
options interpret arguments beginning with \fB\-\fP as invalid options and
6821
require \fB\-\-\fP to prevent this interpretation.
6825
\fB:\fP [\fIarguments\fP]
6827
No effect; the command does nothing beyond expanding
6829
and performing any specified
6830
redirections. A zero exit code is returned.
6832
\fB .\| \fP \fIfilename\fP [\fIarguments\fP]
6835
\fBsource\fP \fIfilename\fP [\fIarguments\fP]
6837
Read and execute commands from
6840
shell environment and return the exit status of the last command
6845
does not contain a slash, filenames in
6848
are used to find the directory containing
6850
The file searched for in
6853
need not be executable.
6854
When \fBbash\fP is not in \fIposix mode\fP, the current directory is
6855
searched if no file is found in
6862
builtin command is turned off, the
6866
If any \fIarguments\fP are supplied, they become the positional
6867
parameters when \fIfilename\fP is executed. Otherwise the positional
6868
parameters are unchanged.
6869
The return status is the status of the last command exited within
6870
the script (0 if no commands are executed), and false if
6872
is not found or cannot be read.
6874
\fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6875
\fBAlias\fP with no arguments or with the
6877
option prints the list of aliases in the form
6878
\fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
6879
When arguments are supplied, an alias is defined for
6880
each \fIname\fP whose \fIvalue\fP is given.
6881
A trailing space in \fIvalue\fP causes the next word to be
6882
checked for alias substitution when the alias is expanded.
6883
For each \fIname\fP in the argument list for which no \fIvalue\fP
6884
is supplied, the name and value of the alias is printed.
6885
\fBAlias\fP returns true unless a \fIname\fP is given for which
6886
no alias has been defined.
6888
\fBbg\fP [\fIjobspec\fP ...]
6889
Resume each suspended job \fIjobspec\fP in the background, as if it
6890
had been started with
6894
is not present, the shell's notion of the \fIcurrent job\fP is used.
6897
returns 0 unless run when job control is disabled or, when run with
6898
job control enabled, any specified \fIjobspec\fP was not found
6899
or was started without job control.
6901
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSVX\fP]
6904
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
6906
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
6908
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
6910
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
6912
\fBbind\fP \fIreadline\-command\fP
6916
key and function bindings, bind a key sequence to a
6918
function or macro, or set a
6921
Each non-option argument is a command as it would appear in
6923
but each binding or command must be passed as a separate argument;
6924
e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
6925
Options, if supplied, have the following meanings:
6932
as the keymap to be affected by the subsequent bindings.
6936
\fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
6937
vi\-move, vi\-command\fP, and
6939
\fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
6940
equivalent to \fIemacs\-standard\fP.
6943
List the names of all \fBreadline\fP functions.
6946
Display \fBreadline\fP function names and bindings in such a way
6947
that they can be re-read.
6950
List current \fBreadline\fP function names and bindings.
6953
Display \fBreadline\fP key sequences bound to macros and the strings
6954
they output in such a way that they can be re-read.
6957
Display \fBreadline\fP key sequences bound to macros and the strings
6961
Display \fBreadline\fP variable names and values in such a way that they
6965
List current \fBreadline\fP variable names and values.
6967
.B \-f \fIfilename\fP
6968
Read key bindings from \fIfilename\fP.
6970
.B \-q \fIfunction\fP
6971
Query about which keys invoke the named \fIfunction\fP.
6973
.B \-u \fIfunction\fP
6974
Unbind all keys bound to the named \fIfunction\fP.
6977
Remove any current binding for \fIkeyseq\fP.
6979
.B \-x \fIkeyseq\fP:\fIshell\-command\fP
6980
Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
6982
When \fIshell\-command\fP is executed, the shell sets the
6985
variable to the contents of the \fBreadline\fP line buffer and the
6988
variable to the current location of the insertion point.
6989
If the executed command changes the value of
6994
.BR READLINE_POINT ,
6995
those new values will be reflected in the editing state.
6998
List all key sequences bound to shell commands and the associated commands
6999
in a format that can be reused as input.
7002
The return value is 0 unless an unrecognized option is given or an
7006
\fBbreak\fP [\fIn\fP]
7013
loop. If \fIn\fP is specified, break \fIn\fP levels.
7017
is greater than the number of enclosing loops, all enclosing loops
7019
The return value is 0 unless \fIn\fP is not greater than or equal to 1.
7021
\fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
7022
Execute the specified shell builtin, passing it
7024
and return its exit status.
7025
This is useful when defining a
7026
function whose name is the same as a shell builtin,
7027
retaining the functionality of the builtin within the function.
7028
The \fBcd\fP builtin is commonly redefined this way.
7029
The return status is false if
7031
is not a shell builtin command.
7033
\fBcaller\fP [\fIexpr\fP]
7034
Returns the context of any active subroutine call (a shell function or
7035
a script executed with the \fB.\fP or \fBsource\fP builtins).
7036
Without \fIexpr\fP, \fBcaller\fP displays the line number and source
7037
filename of the current subroutine call.
7038
If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
7039
displays the line number, subroutine name, and source file corresponding
7040
to that position in the current execution call stack. This extra
7041
information may be used, for example, to print a stack trace. The
7042
current frame is frame 0.
7043
The return value is 0 unless the shell is not executing a subroutine
7044
call or \fIexpr\fP does not correspond to a valid position in the
7047
\fBcd\fP [\fB\-L\fP|[\fB\-P\fP [\fB\-e\fP]] [\-@]] [\fIdir\fP]
7048
Change the current directory to \fIdir\fP.
7049
if \fIdir\fP is not supplied, the value of the
7052
shell variable is the default.
7053
Any additional arguments following \fIdir\fP are ignored.
7057
defines the search path for the directory containing
7059
each directory name in
7062
is searched for \fIdir\fP.
7063
Alternative directory names in
7066
are separated by a colon (:). A null directory name in
7069
is the same as the current directory, i.e., ``\fB.\fP''. If
7071
begins with a slash (/),
7077
option causes \fBcd\fP to use the physical directory structure
7078
by resolving symbolic links while traversing \fIdir\fP and
7079
before processing instances of \fI..\fP in \fIdir\fP (see also the
7083
builtin command); the
7085
option forces symbolic links to be followed by resolving the link
7086
after processing instances of \fI..\fP in \fIdir\fP.
7087
If \fI..\fP appears in \fIdir\fP, it is processed by removing the
7088
immediately previous pathname component from \fIdir\fP, back to a slash
7089
or the beginning of \fIdir\fP.
7092
option is supplied with
7094
and the current working directory cannot be successfully determined
7095
after a successful directory change, \fBcd\fP will return an unsuccessful
7097
On systems that support it, the \fB\-@\fP option presents the extended
7098
attributes associated with a file as a directory.
7104
before the directory change is attempted.
7105
If a non-empty directory name from
7109
\fB\-\fP is the first argument, and the directory change is
7110
successful, the absolute pathname of the new working directory is
7111
written to the standard output.
7112
The return value is true if the directory was successfully changed;
7115
\fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
7120
suppressing the normal shell function lookup. Only builtin
7121
commands or commands found in the
7124
are executed. If the
7126
option is given, the search for
7128
is performed using a default value for
7131
that is guaranteed to find all of the standard utilities.
7136
option is supplied, a description of
7140
option causes a single word indicating the command or filename
7143
to be displayed; the
7145
option produces a more verbose description.
7150
option is supplied, the exit status is 0 if
7152
was found, and 1 if not. If neither option is supplied and
7153
an error occurred or
7155
cannot be found, the exit status is 127. Otherwise, the exit status of the
7157
builtin is the exit status of
7160
\fBcompgen\fP [\fIoption\fP] [\fIword\fP]
7161
Generate possible completion matches for \fIword\fP according to
7162
the \fIoption\fPs, which may be any option accepted by the
7164
builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
7165
the matches to the standard output.
7166
When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
7167
set by the programmable completion facilities, while available, will not
7170
The matches will be generated in the same way as if the programmable
7171
completion code had generated them directly from a completion specification
7172
with the same flags.
7173
If \fIword\fP is specified, only those completions matching \fIword\fP
7176
The return value is true unless an invalid option is supplied, or no
7177
matches were generated.
7179
\fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-DE\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP]
7181
[\fB\-X\fP \fIfilterpat\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP] \fIname\fP [\fIname ...\fP]
7184
\fBcomplete\fP \fB\-pr\fP [\fB\-DE\fP] [\fIname\fP ...]
7186
Specify how arguments to each \fIname\fP should be completed.
7187
If the \fB\-p\fP option is supplied, or if no options are supplied,
7188
existing completion specifications are printed in a way that allows
7189
them to be reused as input.
7190
The \fB\-r\fP option removes a completion specification for
7191
each \fIname\fP, or, if no \fIname\fPs are supplied, all
7192
completion specifications.
7193
The \fB\-D\fP option indicates that the remaining options and actions should
7194
apply to the ``default'' command completion; that is, completion attempted
7195
on a command for which no completion has previously been defined.
7196
The \fB\-E\fP option indicates that the remaining options and actions should
7197
apply to ``empty'' command completion; that is, completion attempted on a
7200
The process of applying these completion specifications when word completion
7201
is attempted is described above under \fBProgrammable Completion\fP.
7203
Other options, if specified, have the following meanings.
7204
The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
7205
(and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
7206
should be quoted to protect them from expansion before the
7212
\fB\-o\fP \fIcomp-option\fP
7213
The \fIcomp-option\fP controls several aspects of the compspec's behavior
7214
beyond the simple generation of completions.
7215
\fIcomp-option\fP may be one of:
7219
Perform the rest of the default \fBbash\fP completions if the compspec
7220
generates no matches.
7223
Use readline's default filename completion if the compspec generates
7227
Perform directory name completion if the compspec generates no matches.
7230
Tell readline that the compspec generates filenames, so it can perform any
7231
filename\-specific processing (like adding a slash to directory names,
7232
quoting special characters, or suppressing trailing spaces).
7233
Intended to be used with shell functions.
7236
Tell readline not to quote the completed words if they are filenames
7237
(quoting filenames is the default).
7240
Tell readline not to append a space (the default) to words completed at
7241
the end of the line.
7244
After any matches defined by the compspec are generated,
7245
directory name completion is attempted and any
7246
matches are added to the results of the other actions.
7249
\fB\-A\fP \fIaction\fP
7250
The \fIaction\fP may be one of the following to generate a list of possible
7255
Alias names. May also be specified as \fB\-a\fP.
7258
Array variable names.
7261
\fBReadline\fP key binding names.
7264
Names of shell builtin commands. May also be specified as \fB\-b\fP.
7267
Command names. May also be specified as \fB\-c\fP.
7270
Directory names. May also be specified as \fB\-d\fP.
7273
Names of disabled shell builtins.
7276
Names of enabled shell builtins.
7279
Names of exported shell variables. May also be specified as \fB\-e\fP.
7282
File names. May also be specified as \fB\-f\fP.
7285
Names of shell functions.
7288
Group names. May also be specified as \fB\-g\fP.
7291
Help topics as accepted by the \fBhelp\fP builtin.
7294
Hostnames, as taken from the file specified by the
7300
Job names, if job control is active. May also be specified as \fB\-j\fP.
7303
Shell reserved words. May also be specified as \fB\-k\fP.
7306
Names of running jobs, if job control is active.
7309
Service names. May also be specified as \fB\-s\fP.
7312
Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
7315
Shell option names as accepted by the \fBshopt\fP builtin.
7321
Names of stopped jobs, if job control is active.
7324
User names. May also be specified as \fB\-u\fP.
7327
Names of all shell variables. May also be specified as \fB\-v\fP.
7330
\fB\-C\fP \fIcommand\fP
7331
\fIcommand\fP is executed in a subshell environment, and its output is
7332
used as the possible completions.
7334
\fB\-F\fP \fIfunction\fP
7335
The shell function \fIfunction\fP is executed in the current shell
7337
When the function is executed,
7338
the first argument (\fB$1\fP) is the name of the command whose arguments are
7340
the second argument (\fB$2\fP) is the word being completed,
7341
and the third argument (\fB$3\fP) is the word preceding the word being
7342
completed on the current command line.
7343
When it finishes, the possible completions are retrieved from the value
7349
\fB\-G\fP \fIglobpat\fP
7350
The pathname expansion pattern \fIglobpat\fP is expanded to generate
7351
the possible completions.
7353
\fB\-P\fP \fIprefix\fP
7354
\fIprefix\fP is added at the beginning of each possible completion
7355
after all other options have been applied.
7357
\fB\-S\fP \fIsuffix\fP
7358
\fIsuffix\fP is appended to each possible completion
7359
after all other options have been applied.
7361
\fB\-W\fP \fIwordlist\fP
7362
The \fIwordlist\fP is split using the characters in the
7365
special variable as delimiters, and each resultant word is expanded.
7366
The possible completions are the members of the resultant list which
7367
match the word being completed.
7369
\fB\-X\fP \fIfilterpat\fP
7370
\fIfilterpat\fP is a pattern as used for pathname expansion.
7371
It is applied to the list of possible completions generated by the
7372
preceding options and arguments, and each completion matching
7373
\fIfilterpat\fP is removed from the list.
7374
A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
7375
case, any completion not matching \fIfilterpat\fP is removed.
7378
The return value is true unless an invalid option is supplied, an option
7379
other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
7380
argument, an attempt is made to remove a completion specification for
7381
a \fIname\fP for which no specification exists, or
7382
an error occurs adding a completion specification.
7385
\fBcompopt\fP [\fB\-o\fP \fIoption\fP] [\fB\-DE\fP] [\fB+o\fP \fIoption\fP] [\fIname\fP]
7386
Modify completion options for each \fIname\fP according to the
7387
\fIoption\fPs, or for the
7388
currently-executing completion if no \fIname\fPs are supplied.
7389
If no \fIoption\fPs are given, display the completion options for each
7390
\fIname\fP or the current completion.
7391
The possible values of \fIoption\fP are those valid for the \fBcomplete\fP
7392
builtin described above.
7393
The \fB\-D\fP option indicates that the remaining options should
7394
apply to the ``default'' command completion; that is, completion attempted
7395
on a command for which no completion has previously been defined.
7396
The \fB\-E\fP option indicates that the remaining options should
7397
apply to ``empty'' command completion; that is, completion attempted on a
7400
The return value is true unless an invalid option is supplied, an attempt
7401
is made to modify the options for a \fIname\fP for which no completion
7402
specification exists, or an output error occurs.
7404
\fBcontinue\fP [\fIn\fP]
7405
Resume the next iteration of the enclosing
7414
is specified, resume at the \fIn\fPth enclosing loop.
7418
is greater than the number of enclosing loops, the last enclosing loop
7419
(the ``top-level'' loop) is resumed.
7420
The return value is 0 unless \fIn\fP is not greater than or equal to 1.
7422
\fBdeclare\fP [\fB\-aAfFgilnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
7425
\fBtypeset\fP [\fB\-aAfFgilnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
7427
Declare variables and/or give them attributes.
7428
If no \fIname\fPs are given then display the values of variables.
7431
option will display the attributes and values of each
7435
is used with \fIname\fP arguments, additional options,
7436
other than \fB\-f\fP and \fB\-F\fP, are ignored.
7439
is supplied without \fIname\fP arguments, it will display the attributes
7440
and values of all variables having the attributes specified by the
7442
If no other options are supplied with \fB\-p\fP, \fBdeclare\fP will display
7443
the attributes and values of all shell variables. The \fB\-f\fP option
7444
will restrict the display to shell functions.
7447
option inhibits the display of function definitions; only the
7448
function name and attributes are printed.
7449
If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
7450
the source file name and line number where the function is defined
7451
are displayed as well. The
7457
option forces variables to be created or modified at the global scope,
7458
even when \fBdeclare\fP is executed in a shell function.
7459
It is ignored in all other cases.
7460
The following options can
7461
be used to restrict output to variables with the specified attribute or
7462
to give variables attributes:
7467
Each \fIname\fP is an indexed array variable (see
7472
Each \fIname\fP is an associative array variable (see
7477
Use function names only.
7480
The variable is treated as an integer; arithmetic evaluation (see
7482
.B "ARITHMETIC EVALUATION"
7483
above) is performed when the variable is assigned a value.
7486
When the variable is assigned a value, all upper-case characters are
7487
converted to lower-case.
7488
The upper-case attribute is disabled.
7491
Give each \fIname\fP the \fInameref\fP attribute, making
7492
it a name reference to another variable.
7493
That other variable is defined by the value of \fIname\fP.
7494
All references and assignments to \fIname\fP, except for changing the
7495
\fB\-n\fP attribute itself, are performed on the variable referenced by
7497
The \fB\-n\fP attribute cannot be applied to array variables.
7500
Make \fIname\fPs readonly. These names cannot then be assigned values
7501
by subsequent assignment statements or unset.
7504
Give each \fIname\fP the \fItrace\fP attribute.
7505
Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
7507
The trace attribute has no special meaning for variables.
7510
When the variable is assigned a value, all lower-case characters are
7511
converted to upper-case.
7512
The lower-case attribute is disabled.
7515
Mark \fIname\fPs for export to subsequent commands via the environment.
7518
Using `+' instead of `\-'
7519
turns off the attribute instead,
7520
with the exceptions that \fB+a\fP
7521
may not be used to destroy an array variable and \fB+r\fP will not
7522
remove the readonly attribute.
7523
When used in a function,
7528
\fIname\fP local, as with the
7531
unless the \fB\-g\fP option is supplied.
7532
If a variable name is followed by =\fIvalue\fP, the value of
7533
the variable is set to \fIvalue\fP.
7534
When using \fB\-a\fP or \fB\-A\fP and the compound assignment syntax to
7535
create array variables, additional attributes do not take effect until
7536
subsequent assignments.
7537
The return value is 0 unless an invalid option is encountered,
7538
an attempt is made to define a function using
7539
.if n ``\-f foo=bar'',
7540
.if t \f(CW\-f foo=bar\fP,
7541
an attempt is made to assign a value to a readonly variable,
7542
an attempt is made to assign a value to an array variable without
7543
using the compound assignment syntax (see
7545
above), one of the \fInames\fP is not a valid shell variable name,
7546
an attempt is made to turn off readonly status for a readonly variable,
7547
an attempt is made to turn off array status for an array variable,
7548
or an attempt is made to display a non-existent function with \fB\-f\fP.
7551
.B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
7552
Without options, displays the list of currently remembered directories.
7553
The default display is on a single line with directory names separated
7555
Directories are added to the list with the
7559
command removes entries from the list.
7564
Clears the directory stack by deleting all of the entries.
7567
Produces a listing using full pathnames;
7568
the default listing format uses a tilde to denote the home directory.
7571
Print the directory stack with one entry per line.
7574
Print the directory stack with one entry per line,
7575
prefixing each entry with its index in the stack.
7578
Displays the \fIn\fPth entry counting from the left of the list
7581
when invoked without options, starting with zero.
7584
Displays the \fIn\fPth entry counting from the right of the list
7587
when invoked without options, starting with zero.
7590
The return value is 0 unless an
7591
invalid option is supplied or \fIn\fP indexes beyond the end
7592
of the directory stack.
7595
\fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
7596
Without options, remove each
7598
from the table of active jobs.
7601
is not present, and neither the \fB\-a\fP nor the \fB\-r\fP option
7602
is supplied, the \fIcurrent job\fP is used.
7603
If the \fB\-h\fP option is given, each
7605
is not removed from the table, but is marked so that
7608
is not sent to the job if the shell receives a
7615
option means to remove or mark all jobs; the
7619
argument restricts operation to running jobs.
7620
The return value is 0 unless a
7622
does not specify a valid job.
7624
\fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
7625
Output the \fIarg\fPs, separated by spaces, followed by a newline.
7626
The return status is 0 unless a write error occurs.
7627
If \fB\-n\fP is specified, the trailing newline is
7628
suppressed. If the \fB\-e\fP option is given, interpretation of
7629
the following backslash-escaped characters is enabled. The
7631
option disables the interpretation of these escape characters,
7632
even on systems where they are interpreted by default.
7633
The \fBxpg_echo\fP shell option may be used to
7634
dynamically determine whether or not \fBecho\fP expands these
7635
escape characters by default.
7637
does not interpret \fB\-\-\fP to mean the end of options.
7639
interprets the following escape sequences:
7650
suppress further output
7676
the eight-bit character whose value is the octal value \fInnn\fP
7677
(zero to three octal digits)
7680
the eight-bit character whose value is the hexadecimal value \fIHH\fP
7681
(one or two hex digits)
7684
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
7685
\fIHHHH\fP (one to four hex digits)
7687
.B \eU\fIHHHHHHHH\fP
7688
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
7689
\fIHHHHHHHH\fP (one to eight hex digits)
7693
\fBenable\fP [\fB\-a\fP] [\fB\-dnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
7694
Enable and disable builtin shell commands.
7695
Disabling a builtin allows a disk command which has the same name
7696
as a shell builtin to be executed without specifying a full pathname,
7697
even though the shell normally searches for builtins before disk commands.
7698
If \fB\-n\fP is used, each \fIname\fP
7699
is disabled; otherwise,
7700
\fInames\fP are enabled. For example, to use the
7702
binary found via the
7705
instead of the shell builtin version, run
7706
.if t \f(CWenable -n test\fP.
7707
.if n ``enable -n test''.
7710
option means to load the new builtin command
7714
on systems that support dynamic loading. The
7716
option will delete a builtin previously loaded with
7718
If no \fIname\fP arguments are given, or if the
7720
option is supplied, a list of shell builtins is printed.
7721
With no other option arguments, the list consists of all enabled
7723
If \fB\-n\fP is supplied, only disabled builtins are printed.
7724
If \fB\-a\fP is supplied, the list printed includes all builtins, with an
7725
indication of whether or not each is enabled.
7726
If \fB\-s\fP is supplied, the output is restricted to the POSIX
7727
\fIspecial\fP builtins.
7728
The return value is 0 unless a
7730
is not a shell builtin or there is an error loading a new builtin
7731
from a shared object.
7733
\fBeval\fP [\fIarg\fP ...]
7734
The \fIarg\fPs are read and concatenated together into a single
7735
command. This command is then read and executed by the shell, and
7736
its exit status is returned as the value of
7740
or only null arguments,
7744
\fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
7747
is specified, it replaces the shell.
7748
No new process is created. The
7750
become the arguments to \fIcommand\fP.
7754
the shell places a dash at the beginning of the zeroth argument passed to
7762
to be executed with an empty environment. If
7764
is supplied, the shell passes
7766
as the zeroth argument to the executed command.
7769
cannot be executed for some reason, a non-interactive shell exits,
7773
is enabled. In that case, it returns failure.
7774
An interactive shell returns failure if the file cannot be executed.
7777
is not specified, any redirections take effect in the current shell,
7778
and the return status is 0. If there is a redirection error, the
7781
\fBexit\fP [\fIn\fP]
7782
Cause the shell to exit
7783
with a status of \fIn\fP. If
7785
is omitted, the exit status
7786
is that of the last command executed.
7790
is executed before the shell terminates.
7792
\fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
7799
are marked for automatic export to the environment of
7800
subsequently executed commands. If the
7808
are given, or if the
7810
option is supplied, a list
7811
of names of all exported variables is printed.
7814
option causes the export property to be removed from each
7816
If a variable name is followed by =\fIword\fP, the value of
7817
the variable is set to \fIword\fP.
7819
returns an exit status of 0 unless an invalid option is
7821
one of the \fInames\fP is not a valid shell variable name, or
7825
that is not a function.
7827
\fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-lnr\fP] [\fIfirst\fP] [\fIlast\fP]
7830
\fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
7832
The first form selects a range of commands from
7836
from the history list and displays or edits and re-executes them.
7840
may be specified as a string (to locate the last command beginning
7841
with that string) or as a number (an index into the history list,
7842
where a negative number is used as an offset from the current
7845
is not specified it is set to
7846
the current command for listing (so that
7847
.if n ``fc \-l \-10''
7848
.if t \f(CWfc \-l \-10\fP
7849
prints the last 10 commands) and to
7854
is not specified it is set to the previous
7855
command for editing and \-16 for listing.
7860
the command numbers when listing. The
7862
option reverses the order of
7863
the commands. If the
7866
the commands are listed on
7867
standard output. Otherwise, the editor given by
7870
on a file containing those commands. If
7876
variable is used, and
7883
is not set. If neither variable is set,
7885
is used. When editing is complete, the edited commands are
7886
echoed and executed.
7888
In the second form, \fIcommand\fP is re-executed after each instance
7889
of \fIpat\fP is replaced by \fIrep\fP.
7890
\fICommand\fP is intepreted the same as \fIfirst\fP above.
7891
A useful alias to use with this is
7892
.if n ``r="fc -s"'',
7893
.if t \f(CWr='fc \-s'\fP,
7897
runs the last command beginning with
7903
re-executes the last command.
7905
If the first form is used, the return value is 0 unless an invalid
7906
option is encountered or
7910
specify history lines out of range.
7913
option is supplied, the return value is the value of the last
7914
command executed or failure if an error occurs with the temporary
7915
file of commands. If the second form is used, the return status
7916
is that of the command re-executed, unless
7918
does not specify a valid history line, in which case
7922
\fBfg\fP [\fIjobspec\fP]
7925
in the foreground, and make it the current job.
7928
is not present, the shell's notion of the \fIcurrent job\fP is used.
7929
The return value is that of the command placed into the foreground,
7930
or failure if run when job control is disabled or, when run with
7931
job control enabled, if
7933
does not specify a valid job or
7935
specifies a job that was started without job control.
7937
\fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
7939
is used by shell procedures to parse positional parameters.
7941
contains the option characters to be recognized; if a character
7942
is followed by a colon, the option is expected to have an
7943
argument, which should be separated from it by white space.
7944
The colon and question mark characters may not be used as
7946
Each time it is invoked,
7948
places the next option in the shell variable
7952
if it does not exist,
7953
and the index of the next argument to be processed into the
7959
is initialized to 1 each time the shell or a shell script
7960
is invoked. When an option requires an argument,
7962
places that argument into the variable
7965
The shell does not reset
7968
automatically; it must be manually reset between multiple
7971
within the same shell invocation if a new set of parameters
7974
When the end of options is encountered, \fBgetopts\fP exits with a
7975
return value greater than zero.
7978
is set to the index of the first non-option argument,
7979
and \fIname\fP is set to ?.
7982
normally parses the positional parameters, but if more arguments are
7986
parses those instead.
7989
can report errors in two ways. If the first character of
7993
error reporting is used. In normal operation, diagnostic messages
7994
are printed when invalid options or missing option arguments are
7999
is set to 0, no error messages will be displayed, even if the first
8004
If an invalid option is seen,
8009
prints an error message and unsets
8015
the option character found is placed in
8018
and no diagnostic message is printed.
8020
If a required argument is not found, and
8023
a question mark (\^\fB?\fP\^) is placed in
8027
is unset, and a diagnostic message is printed.
8030
is silent, then a colon (\^\fB:\fP\^) is placed in
8035
is set to the option character found.
8038
returns true if an option, specified or unspecified, is found.
8039
It returns false if the end of options is encountered or an
8042
\fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
8043
Each time \fBhash\fP is invoked,
8044
the full pathname of the command
8046
is determined by searching
8049
and remembered. Any previously-remembered pathname is discarded.
8052
option is supplied, no path search is performed, and
8054
is used as the full filename of the command.
8057
option causes the shell to forget all
8058
remembered locations.
8061
option causes the shell to forget the remembered location of each \fIname\fP.
8064
option is supplied, the full pathname to which each \fIname\fP corresponds
8065
is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
8066
the \fIname\fP is printed before the hashed full pathname.
8069
option causes output to be displayed in a format that may be reused as input.
8070
If no arguments are given, or if only \fB\-l\fP is supplied,
8071
information about remembered commands is printed.
8072
The return status is true unless a
8074
is not found or an invalid option is supplied.
8076
\fBhelp\fP [\fB\-dms\fP] [\fIpattern\fP]
8077
Display helpful information about builtin commands. If
8081
gives detailed help on all commands matching
8083
otherwise help for all the builtins and shell control structures
8089
Display a short description of each \fIpattern\fP
8092
Display the description of each \fIpattern\fP in a manpage-like format
8095
Display only a short usage synopsis for each \fIpattern\fP
8098
The return status is 0 unless no command matches
8102
\fBhistory [\fIn\fP]
8105
\fBhistory\fP \fB\-c\fP
8107
\fBhistory \-d\fP \fIoffset\fP
8109
\fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
8111
\fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
8113
\fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
8115
With no options, display the command
8116
history list with line numbers. Lines listed
8119
have been modified. An argument of
8124
If the shell variable
8127
is set and not null,
8128
it is used as a format string for \fIstrftime\fP(3) to display
8129
the time stamp associated with each displayed history entry.
8130
No intervening blank is printed between the formatted time stamp
8131
and the history line.
8132
If \fIfilename\fP is supplied, it is used as the
8133
name of the history file; if not, the value of
8136
is used. Options, if supplied, have the following meanings:
8141
Clear the history list by deleting all the entries.
8143
\fB\-d\fP \fIoffset\fP
8144
Delete the history entry at position \fIoffset\fP.
8147
Append the ``new'' history lines (history lines entered since the
8148
beginning of the current \fBbash\fP session) to the history file.
8151
Read the history lines not already read from the history
8152
file into the current history list. These are lines
8153
appended to the history file since the beginning of the
8154
current \fBbash\fP session.
8157
Read the contents of the history file
8158
and append them to the current history list.
8161
Write the current history list to the history file, overwriting the
8162
history file's contents.
8165
Perform history substitution on the following \fIargs\fP and display
8166
the result on the standard output.
8167
Does not store the results in the history list.
8168
Each \fIarg\fP must be quoted to disable normal history expansion.
8173
in the history list as a single entry. The last command in the
8174
history list is removed before the
8182
variable is set, the time stamp information
8183
associated with each history entry is written to the history file,
8184
marked with the history comment character.
8185
When the history file is read, lines beginning with the history
8186
comment character followed immediately by a digit are interpreted
8187
as timestamps for the previous history line.
8188
The return value is 0 unless an invalid option is encountered, an
8189
error occurs while reading or writing the history file, an invalid
8190
\fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
8191
history expansion supplied as an argument to \fB\-p\fP fails.
8194
\fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
8197
\fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
8199
The first form lists the active jobs. The options have the following
8206
in addition to the normal information.
8209
Display information only about jobs that have changed status since
8210
the user was last notified of their status.
8213
List only the process ID of the job's process group
8217
Display only running jobs.
8220
Display only stopped jobs.
8225
is given, output is restricted to information about that job.
8226
The return status is 0 unless an invalid option is encountered
8241
with the corresponding process group ID, and executes
8245
returning its exit status.
8248
\fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
8251
\fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
8253
Send the signal named by
8257
to the processes named by
8262
is either a case-insensitive signal name such as
8265
(with or without the
8268
prefix) or a signal number;
8273
is not present, then
8279
lists the signal names.
8280
If any arguments are supplied when
8282
is given, the names of the signals corresponding to the arguments are
8283
listed, and the return status is 0.
8284
The \fIexit_status\fP argument to
8286
is a number specifying either a signal number or the exit status of
8287
a process terminated by a signal.
8289
returns true if at least one signal was successfully sent, or false
8290
if an error occurs or an invalid option is encountered.
8292
\fBlet\fP \fIarg\fP [\fIarg\fP ...]
8295
is an arithmetic expression to be evaluated (see
8297
.B "ARITHMETIC EVALUATION"
8303
returns 1; 0 is returned otherwise.
8305
\fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
8306
For each argument, a local variable named
8308
is created, and assigned
8310
The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
8313
is used within a function, it causes the variable
8315
to have a visible scope restricted to that function and its children.
8318
writes a list of local variables to the standard output. It is
8321
when not within a function. The return status is 0 unless
8323
is used outside a function, an invalid
8326
\fIname\fP is a readonly variable.
8331
\fBmapfile\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]
8334
\fBreadarray\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]
8336
Read lines from the standard input into the indexed array variable
8338
or from file descriptor
8346
is the default \fIarray\fP.
8347
Options, if supplied, have the following meanings:
8354
lines. If \fIcount\fP is 0, all lines are copied.
8361
The default index is 0.
8364
Discard the first \fIcount\fP lines read.
8367
Remove a trailing newline from each line read.
8370
Read lines from file descriptor \fIfd\fP instead of the standard input.
8375
each time \fIquantum\fP lines are read. The \fB\-c\fP option specifies
8379
Specify the number of lines read between each call to
8385
is specified without
8387
the default quantum is 5000.
8388
When \fIcallback\fP is evaluated, it is supplied the index of the next
8389
array element to be assigned and the line to be assigned to that element
8390
as additional arguments.
8391
\fIcallback\fP is evaluated after the line is read but before the
8392
array element is assigned.
8394
If not supplied with an explicit origin, \fBmapfile\fP will clear \fIarray\fP
8395
before assigning to it.
8397
\fBmapfile\fP returns successfully unless an invalid option or option
8398
argument is supplied, \fIarray\fP is invalid or unassignable, or if
8399
\fIarray\fP is not an indexed array.
8402
\fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
8403
Removes entries from the directory stack. With no arguments,
8404
removes the top directory from the stack, and performs a
8406
to the new top directory.
8407
Arguments, if supplied, have the following meanings:
8412
Suppresses the normal change of directory when removing directories
8413
from the stack, so that only the stack is manipulated.
8416
Removes the \fIn\fPth entry counting from the left of the list
8419
starting with zero. For example:
8421
.if t \f(CWpopd +0\fP
8422
removes the first directory,
8424
.if t \f(CWpopd +1\fP
8428
Removes the \fIn\fPth entry counting from the right of the list
8431
starting with zero. For example:
8433
.if t \f(CWpopd -0\fP
8434
removes the last directory,
8436
.if t \f(CWpopd -1\fP
8442
command is successful, a
8444
is performed as well, and the return status is 0.
8446
returns false if an invalid option is encountered, the directory stack
8447
is empty, a non-existent directory stack entry is specified, or the
8448
directory change fails.
8451
\fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
8452
Write the formatted \fIarguments\fP to the standard output under the
8453
control of the \fIformat\fP.
8454
The \fB\-v\fP option causes the output to be assigned to the variable
8455
\fIvar\fP rather than being printed to the standard output.
8457
The \fIformat\fP is a character string which contains three types of objects:
8458
plain characters, which are simply copied to standard output, character
8459
escape sequences, which are converted and copied to the standard output, and
8460
format specifications, each of which causes printing of the next successive
8462
In addition to the standard \fIprintf\fP(1) format specifications,
8463
\fBprintf\fP interprets the following extensions:
8469
\fBprintf\fP to expand backslash escape sequences in the corresponding
8470
\fIargument\fP (except that \fB\ec\fP terminates output, backslashes in
8471
\fB\e\(aq\fP, \fB\e"\fP, and \fB\e?\fP are not removed, and octal escapes
8472
beginning with \fB\e0\fP may contain up to four digits).
8475
causes \fBprintf\fP to output the corresponding
8476
\fIargument\fP in a format that can be reused as shell input.
8478
.B %(\fIdatefmt\fP)T
8479
causes \fBprintf\fP to output the date-time string resulting from using
8480
\fIdatefmt\fP as a format string for \fIstrftime\fP(3).
8481
The corresponding \fIargument\fP is an integer representing the number of
8482
seconds since the epoch.
8483
Two special argument values may be used: -1 represents the current
8484
time, and -2 represents the time the shell was invoked.
8485
If no argument is specified, conversion behaves as if -1 had been given.
8486
This is an exception to the usual \fBprintf\fP behavior.
8489
Arguments to non-string format specifiers are treated as C constants,
8490
except that a leading plus or minus sign is allowed, and if the leading
8491
character is a single or double quote, the value is the ASCII value of
8492
the following character.
8494
The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
8495
If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
8496
extra format specifications behave as if a zero value or null string, as
8497
appropriate, had been supplied.
8498
The return value is zero on success, non-zero on failure.
8501
\fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
8504
\fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
8506
Adds a directory to the top of the directory stack, or rotates
8507
the stack, making the new top of the stack the current working
8508
directory. With no arguments, exchanges the top two directories
8509
and returns 0, unless the directory stack is empty.
8510
Arguments, if supplied, have the following meanings:
8515
Suppresses the normal change of directory when adding directories
8516
to the stack, so that only the stack is manipulated.
8519
Rotates the stack so that the \fIn\fPth directory
8520
(counting from the left of the list shown by
8526
Rotates the stack so that the \fIn\fPth directory
8527
(counting from the right of the list shown by
8529
starting with zero) is at the top.
8534
to the directory stack at the top, making it the
8535
new current working directory as if it had been supplied as the argument
8536
to the \fBcd\fP builtin.
8541
command is successful, a
8543
is performed as well.
8544
If the first form is used,
8546
returns 0 unless the cd to
8548
fails. With the second form,
8550
returns 0 unless the directory stack is empty,
8551
a non-existent directory stack element is specified,
8552
or the directory change to the specified new current directory
8556
\fBpwd\fP [\fB\-LP\fP]
8557
Print the absolute pathname of the current working directory.
8558
The pathname printed contains no symbolic links if the
8560
option is supplied or the
8564
builtin command is enabled.
8567
option is used, the pathname printed may contain symbolic links.
8568
The return status is 0 unless an error occurs while
8569
reading the name of the current directory or an
8570
invalid option is supplied.
8572
\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 ...]
8573
One line is read from the standard input, or from the file descriptor
8574
\fIfd\fP supplied as an argument to the \fB\-u\fP option, and the first word
8575
is assigned to the first
8577
the second word to the second
8579
and so on, with leftover words and their intervening separators assigned
8582
If there are fewer words read from the input stream than names,
8583
the remaining names are assigned empty values.
8587
are used to split the line into words using the same rules the shell
8588
uses for expansion (described above under \fBWord Splitting\fP).
8589
The backslash character (\fB\e\fP) may be used to remove any special
8590
meaning for the next character read and for line continuation.
8591
Options, if supplied, have the following meanings:
8596
The words are assigned to sequential indices
8597
of the array variable
8601
is unset before any new values are assigned.
8602
Other \fIname\fP arguments are ignored.
8605
The first character of \fIdelim\fP is used to terminate the input line,
8606
rather than newline.
8609
If the standard input
8610
is coming from a terminal,
8615
above) is used to obtain the line.
8616
Readline uses the current (or default, if line editing was not previously
8617
active) editing settings.
8622
is being used to read the line, \fItext\fP is placed into the editing
8623
buffer before editing begins.
8626
\fBread\fP returns after reading \fInchars\fP characters rather than
8627
waiting for a complete line of input, but honor a delimiter if fewer
8628
than \fInchars\fP characters are read before the delimiter.
8631
\fBread\fP returns after reading exactly \fInchars\fP characters rather
8632
than waiting for a complete line of input, unless EOF is encountered or
8633
\fBread\fP times out.
8634
Delimiter characters encountered in the input are
8635
not treated specially and do not cause \fBread\fP to return until
8636
\fInchars\fP characters are read.
8639
Display \fIprompt\fP on standard error, without a
8640
trailing newline, before attempting to read any input. The prompt
8641
is displayed only if input is coming from a terminal.
8644
Backslash does not act as an escape character.
8645
The backslash is considered to be part of the line.
8646
In particular, a backslash-newline pair may not be used as a line
8650
Silent mode. If input is coming from a terminal, characters are
8653
.B \-t \fItimeout\fP
8654
Cause \fBread\fP to time out and return failure if a complete line of
8655
input (or a specified number of characters)
8656
is not read within \fItimeout\fP seconds.
8657
\fItimeout\fP may be a decimal number with a fractional portion following
8659
This option is only effective if \fBread\fP is reading input from a
8660
terminal, pipe, or other special file; it has no effect when reading
8662
If \fBread\fP times out, \fBread\fP saves any partial input read into
8663
the specified variable \fIname\fP.
8664
If \fItimeout\fP is 0, \fBread\fP returns immediately, without trying to
8665
read any data. The exit status is 0 if input is available on
8666
the specified file descriptor, non-zero otherwise.
8667
The exit status is greater than 128 if the timeout is exceeded.
8670
Read input from file descriptor \fIfd\fP.
8675
are supplied, the line read is assigned to the variable
8678
The return code is zero, unless end-of-file is encountered, \fBread\fP
8679
times out (in which case the return code is greater than 128),
8680
a variable assignment error (such as assigning to a readonly variable) occurs,
8681
or an invalid file descriptor is supplied as the argument to \fB\-u\fP.
8684
\fBreadonly\fP [\fB\-aAf\fP] [\fB\-p\fP] [\fIname\fP[=\fIword\fP] ...]
8687
\fInames\fP are marked readonly; the values of these
8689
may not be changed by subsequent assignment.
8692
option is supplied, the functions corresponding to the
8697
option restricts the variables to indexed arrays; the
8699
option restricts the variables to associative arrays.
8700
If both options are supplied,
8705
arguments are given, or if the
8707
option is supplied, a list of all readonly names is printed.
8708
The other options may be used to restrict the output to a subset of
8709
the set of readonly names.
8712
option causes output to be displayed in a format that
8713
may be reused as input.
8714
If a variable name is followed by =\fIword\fP, the value of
8715
the variable is set to \fIword\fP.
8716
The return status is 0 unless an invalid option is encountered,
8719
is not a valid shell variable name, or
8723
that is not a function.
8725
\fBreturn\fP [\fIn\fP]
8726
Causes a function to stop executing and return the value specified by
8731
is omitted, the return status is that of the last command
8732
executed in the function body. If
8734
is used outside a function,
8735
but during execution of a script by the
8737
(\fBsource\fP) command, it causes the shell to stop executing
8738
that script and return either
8740
or the exit status of the last command executed within the
8741
script as the exit status of the script.
8742
If \fIn\fP is supplied, the return value is its least significant
8744
The return status is non-zero if
8746
is supplied a non-numeric argument, or
8748
function and not during execution of a script by \fB.\fP\^ or \fBsource\fP.
8749
Any command associated with the \fBRETURN\fP trap is executed
8750
before execution resumes after the function or script.
8752
\fBset\fP [\fB\-\-abefhkmnptuvxBCEHPT\fP] [\fB\-o\fP \fIoption\-name\fP] [\fIarg\fP ...]
8755
\fBset\fP [\fB+abefhkmnptuvxBCEHPT\fP] [\fB+o\fP \fIoption\-name\fP] [\fIarg\fP ...]
8757
Without options, the name and value of each shell variable are displayed
8758
in a format that can be reused as input
8759
for setting or resetting the currently-set variables.
8760
Read-only variables cannot be reset.
8761
In \fIposix\fP mode, only shell variables are listed.
8762
The output is sorted according to the current locale.
8763
When options are specified, they set or unset shell attributes.
8764
Any arguments remaining after option processing are treated
8765
as values for the positional parameters and are assigned, in order, to
8770
Options, if specified, have the following meanings:
8775
Automatically mark variables and functions which are modified or
8776
created for export to the environment of subsequent commands.
8779
Report the status of terminated background jobs
8780
immediately, rather than before the next primary prompt. This is
8781
effective only when job control is enabled.
8784
Exit immediately if a
8785
\fIpipeline\fP (which may consist of a single \fIsimple command\fP),
8787
or a \fIcompound command\fP
8791
above), exits with a non-zero status.
8792
The shell does not exit if the
8793
command that fails is part of the command list immediately following a
8798
part of the test following the
8802
reserved words, part of any command executed in a
8806
list except the command following the final \fB&&\fP or \fB||\fP,
8807
any command in a pipeline but the last,
8808
or if the command's return value is
8811
If a compound command other than a subshell
8812
returns a non-zero status because a command failed
8813
while \fB\-e\fP was being ignored, the shell does not exit.
8814
A trap on \fBERR\fP, if set, is executed before the shell exits.
8815
This option applies to the shell environment and each subshell environment
8818
.B "COMMAND EXECUTION ENVIRONMENT"
8819
above), and may cause
8820
subshells to exit before executing all the commands in the subshell.
8823
If a compound command or shell function executes in a context
8824
where \fB\-e\fP is being ignored,
8825
none of the commands executed within the compound command or function body
8826
will be affected by the \fB\-e\fP setting, even if \fB\-e\fP is set
8827
and a command returns a failure status.
8828
If a compound command or shell function sets \fB\-e\fP while executing in
8829
a context where \fB\-e\fP is ignored, that setting will not have any
8830
effect until the compound command or the command containing the function
8834
Disable pathname expansion.
8837
Remember the location of commands as they are looked up for execution.
8838
This is enabled by default.
8841
All arguments in the form of assignment statements
8842
are placed in the environment for a command, not just
8843
those that precede the command name.
8846
Monitor mode. Job control is enabled. This option is on
8847
by default for interactive shells on systems that support
8852
All processes run in a separate process group.
8853
When a background job completes, the shell prints a line
8854
containing its exit status.
8857
Read commands but do not execute them. This may be used to
8858
check a shell script for syntax errors. This is ignored by
8861
.B \-o \fIoption\-name\fP
8862
The \fIoption\-name\fP can be one of the following:
8874
Use an emacs-style command line editing interface. This is enabled
8875
by default when the shell is interactive, unless the shell is started
8879
This also affects the editing interface used for \fBread \-e\fP.
8902
Enable command history, as described above under
8905
This option is on by default in interactive shells.
8908
The effect is as if the shell command
8909
.if t \f(CWIGNOREEOF=10\fP
8910
.if n ``IGNOREEOF=10''
8956
If set, the return value of a pipeline is the value of the last
8957
(rightmost) command to exit with a non-zero status, or zero if all
8958
commands in the pipeline exit successfully.
8959
This option is disabled by default.
8962
Change the behavior of
8964
where the default operation differs
8965
from the POSIX standard to match the standard (\fIposix mode\fP).
8969
below for a reference to a document that details how posix mode affects
8981
Use a vi-style command line editing interface.
8982
This also affects the editing interface used for \fBread \-e\fP.
8991
is supplied with no \fIoption\-name\fP, the values of the current options are
8995
is supplied with no \fIoption\-name\fP, a series of
8997
commands to recreate the current option settings is displayed on
8998
the standard output.
9004
mode. In this mode, the
9010
files are not processed, shell functions are not inherited from the
9011
environment, and the
9021
variables, if they appear in the environment, are ignored.
9022
If the shell is started with the effective user (group) id not equal to the
9023
real user (group) id, and the \fB\-p\fP option is not supplied, these actions
9024
are taken and the effective user id is set to the real user id.
9025
If the \fB\-p\fP option is supplied at startup, the effective user id is
9027
Turning this option off causes the effective user
9028
and group ids to be set to the real user and group ids.
9031
Exit after reading and executing one command.
9034
Treat unset variables and parameters other than the special
9035
parameters "@" and "*" as an error when performing
9036
parameter expansion. If expansion is attempted on an
9037
unset variable or parameter, the shell prints an error message, and,
9038
if not interactive, exits with a non-zero status.
9041
Print shell input lines as they are read.
9044
After expanding each \fIsimple command\fP,
9045
\fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
9046
arithmetic \fBfor\fP command, display the expanded value of
9049
followed by the command and its expanded arguments
9050
or associated word list.
9053
The shell performs brace expansion (see
9055
above). This is on by default.
9060
does not overwrite an existing file with the
9065
redirection operators. This may be overridden when
9066
creating output files by using the redirection operator
9072
If set, any trap on \fBERR\fP is inherited by shell functions, command
9073
substitutions, and commands executed in a subshell environment.
9074
The \fBERR\fP trap is normally not inherited in such cases.
9079
style history substitution. This option is on by
9080
default when the shell is interactive.
9083
If set, the shell does not resolve symbolic links when executing
9086
that change the current working directory. It uses the
9087
physical directory structure instead. By default,
9089
follows the logical chain of directories when performing commands
9090
which change the current directory.
9093
If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
9094
functions, command substitutions, and commands executed in a
9095
subshell environment.
9096
The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
9100
If no arguments follow this option, then the positional parameters are
9101
unset. Otherwise, the positional parameters are set to the
9102
\fIarg\fPs, even if some of them begin with a
9106
Signal the end of options, cause all remaining \fIarg\fPs to be
9107
assigned to the positional parameters. The
9111
options are turned off.
9112
If there are no \fIarg\fPs,
9113
the positional parameters remain unchanged.
9116
The options are off by default unless otherwise noted.
9117
Using + rather than \- causes these options to be turned off.
9118
The options can also be specified as arguments to an invocation of
9120
The current set of options may be found in
9122
The return status is always true unless an invalid option is encountered.
9125
\fBshift\fP [\fIn\fP]
9126
The positional parameters from \fIn\fP+1 ... are renamed to
9129
Parameters represented by the numbers \fB$#\fP
9130
down to \fB$#\fP\-\fIn\fP+1 are unset.
9132
must be a non-negative number less than or equal to \fB$#\fP.
9135
is 0, no parameters are changed.
9138
is not given, it is assumed to be 1.
9141
is greater than \fB$#\fP, the positional parameters are not changed.
9142
The return status is greater than zero if
9146
or less than zero; otherwise 0.
9148
\fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
9149
Toggle the values of settings controlling optional shell behavior.
9150
The settings can be either those listed below, or, if the
9152
option is used, those available with the
9154
option to the \fBset\fP builtin command.
9155
With no options, or with the
9157
option, a list of all settable options is displayed, with
9158
an indication of whether or not each is set.
9159
The \fB\-p\fP option causes output to be displayed in a form that
9160
may be reused as input.
9161
Other options have the following meanings:
9166
Enable (set) each \fIoptname\fP.
9169
Disable (unset) each \fIoptname\fP.
9172
Suppresses normal output (quiet mode); the return status indicates
9173
whether the \fIoptname\fP is set or unset.
9174
If multiple \fIoptname\fP arguments are given with
9176
the return status is zero if all \fIoptnames\fP are enabled; non-zero
9180
Restricts the values of \fIoptname\fP to be those defined for the
9191
is used with no \fIoptname\fP arguments,
9193
shows only those options which are set or unset, respectively.
9194
Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
9197
The return status when listing options is zero if all \fIoptnames\fP
9198
are enabled, non-zero otherwise. When setting or unsetting options,
9199
the return status is zero unless an \fIoptname\fP is not a valid shell
9202
The list of \fBshopt\fP options is:
9208
If set, a command name that is the name of a directory is executed as if
9209
it were the argument to the \fBcd\fP command.
9210
This option is only used by interactive shells.
9213
If set, an argument to the
9215
builtin command that
9216
is not a directory is assumed to be the name of a variable whose
9217
value is the directory to change to.
9220
If set, minor errors in the spelling of a directory component in a
9222
command will be corrected.
9223
The errors checked for are transposed characters,
9224
a missing character, and one character too many.
9225
If a correction is found, the corrected filename is printed,
9226
and the command proceeds.
9227
This option is only used by interactive shells.
9230
If set, \fBbash\fP checks that a command found in the hash
9231
table exists before trying to execute it. If a hashed command no
9232
longer exists, a normal path search is performed.
9235
If set, \fBbash\fP lists the status of any stopped and running jobs before
9236
exiting an interactive shell. If any jobs are running, this causes
9237
the exit to be deferred until a second exit is attempted without an
9238
intervening command (see
9241
above). The shell always
9242
postpones exiting if any jobs are stopped.
9245
If set, \fBbash\fP checks the window size after each command
9246
and, if necessary, updates the values of
9256
attempts to save all lines of a multiple-line
9257
command in the same history entry. This allows
9258
easy re-editing of multi-line commands.
9263
changes its behavior to that of version 3.1 with respect to quoted
9264
arguments to the \fB[[\fP conditional command's \fB=~\fP operator
9265
and locale-specific string comparison when using the \fB[[\fP
9266
conditional command's \fB<\fP and \fB>\fP operators.
9267
Bash versions prior to bash-4.1 use ASCII collation and
9269
bash-4.1 and later use the current locale's collation sequence and
9275
changes its behavior to that of version 3.2 with respect to
9276
locale-specific string comparison when using the \fB[[\fP
9277
conditional command's \fB<\fP and \fB>\fP operators (see previous item).
9282
changes its behavior to that of version 4.0 with respect to locale-specific
9283
string comparison when using the \fB[[\fP
9284
conditional command's \fB<\fP and \fB>\fP operators (see description of
9286
and the effect of interrupting a command list.
9287
Bash versions 4.0 and later interrupt the list as if the shell received the
9288
interrupt; previous versions continue with the next command in the list.
9293
when in \fIposix\fP mode, treats a single quote in a double-quoted
9294
parameter expansion as a special character. The single quotes must match
9295
(an even number) and the characters between the single quotes are considered
9296
quoted. This is the behavior of posix mode through version 4.1.
9297
The default bash behavior remains as in previous versions.
9302
does not process the replacement string in the pattern substitution word
9303
expansion using quote removal.
9305
.B complete_fullquote
9308
quotes all shell metacharacters in filenames and directory names when
9309
performing completion.
9312
removes metacharacters such as the dollar sign from the set of
9313
characters that will be quoted in completed filenames
9314
when these metacharacters appear in shell variable references in words to be
9316
This means that dollar signs in variable names that expand to directories
9318
however, any dollar signs appearing in filenames will not be quoted, either.
9319
This is active only when bash is using backslashes to quote completed
9321
This variable is set by default, which is the default bash behavior in
9322
versions through 4.2.
9327
replaces directory names with the results of word expansion when performing
9328
filename completion. This changes the contents of the readline editing
9332
attempts to preserve what the user typed.
9337
attempts spelling correction on directory names during word completion
9338
if the directory name initially supplied does not exist.
9343
includes filenames beginning with a `.' in the results of pathname
9347
If set, a non-interactive shell will not exit if
9348
it cannot execute the file specified as an argument to the
9350
builtin command. An interactive shell does not exit if
9355
If set, aliases are expanded as described above under
9358
This option is enabled by default for interactive shells.
9361
If set, behavior intended for use by debuggers is enabled:
9365
The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
9366
file name and line number corresponding to each function name supplied
9370
If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
9371
next command is skipped and not executed.
9374
If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
9375
shell is executing in a subroutine (a shell function or a shell script
9376
executed by the \fB.\fP or \fBsource\fP builtins), a call to
9377
\fBreturn\fP is simulated.
9385
are updated as described in their descriptions above.
9388
Function tracing is enabled: command substitution, shell functions, and
9389
subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
9390
\fBDEBUG\fP and \fBRETURN\fP traps.
9393
Error tracing is enabled: command substitution, shell functions, and
9394
subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
9399
If set, the extended pattern matching features described above under
9400
\fBPathname Expansion\fP are enabled.
9403
If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
9404
performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
9405
enclosed in double quotes. This option is enabled by default.
9408
If set, patterns which fail to match filenames during pathname expansion
9409
result in an expansion error.
9412
If set, the suffixes specified by the
9416
cause words to be ignored when performing word completion even if
9417
the ignored words are the only possible completions.
9420
\fBSHELL VARIABLES\fP
9421
above for a description of
9424
This option is enabled by default.
9427
If set, range expressions used in pattern matching bracket expressions (see
9430
above) behave as if in the traditional C locale when performing
9431
comparisons. That is, the current locale's collating sequence
9432
is not taken into account, so
9434
will not collate between
9438
and upper-case and lower-case ASCII characters will collate together.
9441
If set, the pattern \fB**\fP used in a pathname expansion context will
9442
match all files and zero or more directories and subdirectories.
9443
If the pattern is followed by a \fB/\fP, only directories and
9444
subdirectories match.
9447
If set, shell error messages are written in the standard GNU error
9451
If set, the history list is appended to the file named by the value
9455
variable when the shell exits, rather than overwriting the file.
9460
is being used, a user is given the opportunity to re-edit a
9461
failed history substitution.
9466
is being used, the results of history substitution are not immediately
9467
passed to the shell parser. Instead, the resulting line is loaded into
9468
the \fBreadline\fP editing buffer, allowing further modification.
9473
is being used, \fBbash\fP will attempt to perform hostname completion when a
9474
word containing a \fB@\fP is being completed (see
9480
This is enabled by default.
9483
If set, \fBbash\fP will send
9486
to all jobs when an interactive login shell exits.
9488
.B interactive_comments
9489
If set, allow a word beginning with
9491
to cause that word and all remaining characters on that
9492
line to be ignored in an interactive shell (see
9495
above). This option is enabled by default.
9498
If set, and job control is not active, the shell runs the last command of
9499
a pipeline not executed in the background in the current shell environment.
9504
option is enabled, multi-line commands are saved to the history with
9505
embedded newlines rather than using semicolon separators where possible.
9508
The shell sets this option if it is started as a login shell (see
9512
The value may not be changed.
9515
If set, and a file that \fBbash\fP is checking for mail has been
9516
accessed since the last time it was checked, the message ``The mail in
9517
\fImailfile\fP has been read'' is displayed.
9519
.B no_empty_cmd_completion
9524
will not attempt to search the
9527
for possible completions when
9528
completion is attempted on an empty line.
9533
matches filenames in a case\-insensitive fashion when performing pathname
9535
.B Pathname Expansion
9541
matches patterns in a case\-insensitive fashion when performing matching
9542
while executing \fBcase\fP or \fB[[\fP conditional commands.
9547
allows patterns which match no
9549
.B Pathname Expansion
9551
to expand to a null string, rather than themselves.
9554
If set, the programmable completion facilities (see
9555
\fBProgrammable Completion\fP above) are enabled.
9556
This option is enabled by default.
9559
If set, prompt strings undergo
9560
parameter expansion, command substitution, arithmetic
9561
expansion, and quote removal after being expanded as described in
9564
above. This option is enabled by default.
9567
The shell sets this option if it is started in restricted mode (see
9569
.B "RESTRICTED SHELL"
9571
The value may not be changed.
9572
This is not reset when the startup files are executed, allowing
9573
the startup files to discover whether or not a shell is restricted.
9578
builtin prints an error message when the shift count exceeds the
9579
number of positional parameters.
9583
\fBsource\fP (\fB.\fP) builtin uses the value of
9586
to find the directory containing the file supplied as an argument.
9587
This option is enabled by default.
9590
If set, the \fBecho\fP builtin expands backslash-escape sequences
9595
\fBsuspend\fP [\fB\-f\fP]
9596
Suspend the execution of this shell until it receives a
9599
signal. A login shell cannot be suspended; the
9601
option can be used to override this and force the suspension.
9602
The return status is 0 unless the shell is a login shell and
9604
is not supplied, or if job control is not enabled.
9606
\fBtest\fP \fIexpr\fP
9609
\fB[\fP \fIexpr\fP \fB]\fP
9610
Return a status of 0 (true) or 1 (false) depending on
9611
the evaluation of the conditional expression
9613
Each operator and operand must be a separate argument.
9614
Expressions are composed of the primaries described above under
9616
.BR "CONDITIONAL EXPRESSIONS" .
9617
\fBtest\fP does not accept any options, nor does it accept and ignore
9618
an argument of \fB\-\-\fP as signifying the end of options.
9621
Expressions may be combined using the following operators, listed
9622
in decreasing order of precedence.
9623
The evaluation depends on the number of arguments; see below.
9624
Operator precedence is used when there are five or more arguments.
9634
Returns the value of \fIexpr\fP.
9635
This may be used to override the normal precedence of operators.
9637
\fIexpr1\fP \-\fBa\fP \fIexpr2\fP
9644
\fIexpr1\fP \-\fBo\fP \fIexpr2\fP
9652
\fBtest\fP and \fB[\fP evaluate conditional
9653
expressions using a set of rules based on the number of arguments.
9659
The expression is false.
9662
The expression is true if and only if the argument is not null.
9665
If the first argument is \fB!\fP, the expression is true if and
9666
only if the second argument is null.
9667
If the first argument is one of the unary conditional operators listed above
9670
.BR "CONDITIONAL EXPRESSIONS" ,
9671
the expression is true if the unary test is true.
9672
If the first argument is not a valid unary conditional operator, the expression
9676
The following conditions are applied in the order listed.
9677
If the second argument is one of the binary conditional operators listed above
9680
.BR "CONDITIONAL EXPRESSIONS" ,
9681
the result of the expression is the result of the binary test using
9682
the first and third arguments as operands.
9683
The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
9684
when there are three arguments.
9685
If the first argument is \fB!\fP, the value is the negation of
9686
the two-argument test using the second and third arguments.
9687
If the first argument is exactly \fB(\fP and the third argument is
9688
exactly \fB)\fP, the result is the one-argument test of the second
9690
Otherwise, the expression is false.
9693
If the first argument is \fB!\fP, the result is the negation of
9694
the three-argument expression composed of the remaining arguments.
9695
Otherwise, the expression is parsed and evaluated according to
9696
precedence using the rules listed above.
9699
The expression is parsed and evaluated according to precedence
9700
using the rules listed above.
9704
When used with \fBtest\fP or \fB[\fP, the \fB<\fP and \fB>\fP operators
9705
sort lexicographically using ASCII ordering.
9710
Print the accumulated user and system times for the shell and
9711
for processes run from the shell. The return status is 0.
9713
\fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
9716
is to be read and executed when the shell receives
9721
is absent (and there is a single \fIsigspec\fP) or
9723
each specified signal is
9724
reset to its original disposition (the value it had
9725
upon entrance to the shell).
9728
is the null string the signal specified by each
9730
is ignored by the shell and by the commands it invokes.
9735
has been supplied, then the trap commands associated with each
9738
If no arguments are supplied or if only
9742
prints the list of commands associated with each signal.
9745
option causes the shell to print a list of signal names and
9746
their corresponding numbers.
9750
a signal name defined in <\fIsignal.h\fP>, or a signal number.
9751
Signal names are case insensitive and the
9764
is executed on exit from the shell.
9772
is executed before every \fIsimple command\fP, \fIfor\fP command,
9773
\fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
9774
command, and before the first command executes in a shell function (see
9778
Refer to the description of the \fBextdebug\fP option to the
9779
\fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
9787
is executed each time a shell function or a script executed with
9788
the \fB.\fP or \fBsource\fP builtins finishes executing.
9798
is executed whenever a
9799
a pipeline (which may consist of a single simple
9800
command), a list, or a compound command returns a
9801
non\-zero exit status,
9802
subject to the following conditions.
9806
trap is not executed if the failed
9807
command is part of the command list immediately following a
9812
part of the test in an
9814
statement, part of a command executed in a
9818
list except the command following the final \fB&&\fP or \fB||\fP,
9819
any command in a pipeline but the last,
9820
or if the command's return value is
9821
being inverted using
9823
These are the same conditions obeyed by the \fBerrexit\fP (\fB\-e\fP) option.
9826
Signals ignored upon entry to the shell cannot be trapped or reset.
9827
Trapped signals that are not being ignored are reset to their original
9828
values in a subshell or subshell environment when one is created.
9829
The return status is false if any
9831
is invalid; otherwise
9835
\fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
9839
would be interpreted if used as a command name.
9844
prints a string which is one of
9853
is an alias, shell reserved word, function, builtin, or disk file,
9857
is not found, then nothing is printed, and an exit status of false
9863
either returns the name of the disk file
9864
that would be executed if
9866
were specified as a command name,
9868
.if t \f(CWtype -t name\fP
9869
.if n ``type -t name''
9877
search for each \fIname\fP, even if
9878
.if t \f(CWtype -t name\fP
9879
.if n ``type -t name''
9882
If a command is hashed,
9886
print the hashed value, which is not necessarily the file that appears
9894
prints all of the places that contain
9897
This includes aliases and functions,
9900
option is not also used.
9901
The table of hashed commands is not consulted
9906
option suppresses shell function lookup, as with the \fBcommand\fP builtin.
9908
returns true if all of the arguments are found, false if
9911
\fBulimit\fP [\fB\-HSTabcdefilmnpqrstuvx\fP [\fIlimit\fP]]
9912
Provides control over the resources available to the shell and to
9913
processes started by it, on systems that allow such control.
9914
The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
9915
set for the given resource.
9916
A hard limit cannot be increased by a non-root user once it is set;
9917
a soft limit may be increased up to the value of the hard limit.
9918
If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
9922
can be a number in the unit specified for the resource
9923
or one of the special values
9928
which stand for the current hard limit, the current soft limit, and
9929
no limit, respectively.
9932
is omitted, the current value of the soft limit of the resource is
9933
printed, unless the \fB\-H\fP option is given. When more than one
9934
resource is specified, the limit name and unit are printed before the value.
9935
Other options are interpreted as follows:
9940
All current limits are reported
9943
The maximum socket buffer size
9946
The maximum size of core files created
9949
The maximum size of a process's data segment
9952
The maximum scheduling priority ("nice")
9955
The maximum size of files written by the shell and its children
9958
The maximum number of pending signals
9961
The maximum size that may be locked into memory
9964
The maximum resident set size (many systems do not honor this limit)
9967
The maximum number of open file descriptors (most systems do not
9968
allow this value to be set)
9971
The pipe size in 512-byte blocks (this may not be set)
9974
The maximum number of bytes in POSIX message queues
9977
The maximum real-time scheduling priority
9980
The maximum stack size
9983
The maximum amount of cpu time in seconds
9986
The maximum number of processes available to a single user
9989
The maximum amount of virtual memory available to the shell and, on
9990
some systems, to its children
9993
The maximum number of file locks
9996
The maximum number of threads
10003
option is not used,
10004
\fIlimit\fP is the new value of the specified resource.
10005
If no option is given, then
10007
is assumed. Values are in 1024-byte increments, except for
10009
which is in seconds;
10011
which is in units of 512-byte blocks;
10018
which are unscaled values.
10019
The return status is 0 unless an invalid option or argument is supplied,
10020
or an error occurs while setting a new limit.
10023
\fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
10024
The user file-creation mask is set to
10028
begins with a digit, it
10029
is interpreted as an octal number; otherwise
10030
it is interpreted as a symbolic mode mask similar
10031
to that accepted by
10035
is omitted, the current value of the mask is printed.
10038
option causes the mask to be printed in symbolic form; the
10039
default output is an octal number.
10042
option is supplied, and
10044
is omitted, the output is in a form that may be reused as input.
10045
The return status is 0 if the mode was successfully changed or if
10046
no \fImode\fP argument was supplied, and false otherwise.
10048
\fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
10049
Remove each \fIname\fP from the list of defined aliases. If
10051
is supplied, all alias definitions are removed. The return
10052
value is true unless a supplied
10054
is not a defined alias.
10056
\fBunset\fP [\-\fBfv\fP] [\-\fBn\fP] [\fIname\fP ...]
10059
remove the corresponding variable or function.
10062
option is given, each
10064
refers to a shell variable, and that variable is removed.
10065
Read-only variables may not be unset.
10070
refers to a shell function, and the function definition
10074
option is supplied, and \fIname\fP is a variable with the \fInameref\fP
10075
attribute, \fIname\fP will be unset rather than the variable it
10077
\fB\-n\fP has no effect if the \fB\-f\fP option is supplied.
10078
If no options are supplied, each \fIname\fP refers to a variable; if
10079
there is no variable by that name, any function with that name is
10081
Each unset variable or function is removed from the environment
10082
passed to subsequent commands.
10085
.BR COMP_WORDBREAKS ,
10101
are unset, they lose their special properties, even if they are
10102
subsequently reset. The exit status is true unless a
10106
\fBwait\fP [\fB\-n\fP] [\fIn ...\fP]
10107
Wait for each specified child process and return its termination status.
10111
ID or a job specification; if a job spec is given, all processes
10112
in that job's pipeline are waited for. If
10114
is not given, all currently active child processes
10115
are waited for, and the return status is zero.
10116
If the \fB\-n\fP option is supplied, \fBwait\fP waits for any job to
10117
terminate and returns its exit status.
10120
specifies a non-existent process or job, the return status is
10121
127. Otherwise, the return status is the exit status of the last
10122
process or job waited for.
10125
.SH "RESTRICTED SHELL"
10131
is started with the name
10135
option is supplied at invocation,
10136
the shell becomes restricted.
10137
A restricted shell is used to
10138
set up an environment more controlled than the standard shell.
10139
It behaves identically to
10141
with the exception that the following are disallowed or not performed:
10143
changing directories with \fBcd\fP
10145
setting or unsetting the values of
10156
specifying command names containing
10159
specifying a filename containing a
10161
as an argument to the
10165
specifying a filename containing a slash as an argument to the
10171
importing function definitions from the shell environment at startup
10173
parsing the value of
10176
from the shell environment at startup
10178
redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
10182
builtin command to replace the shell with another command
10184
adding or deleting builtin commands with the
10192
using the \fBenable\fP builtin command to enable disabled shell builtins
10200
turning off restricted mode with
10201
\fBset +r\fP or \fBset +o restricted\fP.
10203
These restrictions are enforced after any startup files are read.
10205
.ie \n(zY=1 When a command that is found to be a shell script is executed,
10206
.el \{ When a command that is found to be a shell script is executed
10209
.B "COMMAND EXECUTION"
10213
turns off any restrictions in the shell spawned to execute the
10220
\fIBash Reference Manual\fP, Brian Fox and Chet Ramey
10222
\fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
10224
\fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
10226
\fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE --
10227
http://pubs.opengroup.org/onlinepubs/9699919799/
10229
http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
10231
\fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
10233
\fIemacs\fP(1), \fIvi\fP(1)
10241
The \fBbash\fP executable
10244
The systemwide initialization file, executed for login shells
10246
.FN ~/.bash_profile
10247
The personal initialization file, executed for login shells
10250
The individual per-interactive-shell startup file
10253
The individual login shell cleanup file, executed when a login shell exits
10256
Individual \fIreadline\fP initialization file
10259
Brian Fox, Free Software Foundation
10263
Chet Ramey, Case Western Reserve University
10265
chet.ramey@case.edu
10267
If you find a bug in
10269
you should report it. But first, you should
10270
make sure that it really is a bug, and that it appears in the latest
10273
The latest version is always available from
10274
\fIftp://ftp.gnu.org/pub/gnu/bash/\fP.
10276
Once you have determined that a bug actually exists, use the
10278
command to submit a bug report.
10279
If you have a fix, you are encouraged to mail that as well!
10280
Suggestions and `philosophical' bug reports may be mailed
10281
to \fIbug-bash@gnu.org\fP or posted to the Usenet
10285
ALL bug reports should include:
10289
The version number of \fBbash\fR
10291
The hardware and operating system
10293
The compiler used to compile
10295
A description of the bug behaviour
10297
A short script or `recipe' which exercises the bug
10301
inserts the first three items automatically into the template
10302
it provides for filing a bug report.
10304
Comments and bug reports concerning
10305
this manual page should be directed to
10306
.IR chet.ramey@case.edu .
10309
It's too big and too slow.
10311
There are some subtle differences between
10313
and traditional versions of
10315
mostly because of the
10320
Aliases are confusing in some uses.
10322
Shell builtin commands and functions are not stoppable/restartable.
10324
Compound commands and command sequences of the form `a ; b ; c'
10325
are not handled gracefully when process suspension is attempted.
10326
When a process is stopped, the shell immediately executes the next
10327
command in the sequence.
10328
It suffices to place the sequence of commands between
10329
parentheses to force it into a subshell, which may be stopped as
10332
Array variables may not (yet) be exported.
10334
There may be only one active coprocess at a time.