xref: /freebsd/bin/sh/sh.1 (revision 7b14d37fb1f7ec306198197c051f44e5d44173f2)
19ddb49cbSWarner Losh.\"-
24b88c807SRodney W. Grimes.\" Copyright (c) 1991, 1993
34b88c807SRodney W. Grimes.\"	The Regents of the University of California.  All rights reserved.
44b88c807SRodney W. Grimes.\"
54b88c807SRodney W. Grimes.\" This code is derived from software contributed to Berkeley by
64b88c807SRodney W. Grimes.\" Kenneth Almquist.
74b88c807SRodney W. Grimes.\"
84b88c807SRodney W. Grimes.\" Redistribution and use in source and binary forms, with or without
94b88c807SRodney W. Grimes.\" modification, are permitted provided that the following conditions
104b88c807SRodney W. Grimes.\" are met:
114b88c807SRodney W. Grimes.\" 1. Redistributions of source code must retain the above copyright
124b88c807SRodney W. Grimes.\"    notice, this list of conditions and the following disclaimer.
134b88c807SRodney W. Grimes.\" 2. Redistributions in binary form must reproduce the above copyright
144b88c807SRodney W. Grimes.\"    notice, this list of conditions and the following disclaimer in the
154b88c807SRodney W. Grimes.\"    documentation and/or other materials provided with the distribution.
164b88c807SRodney W. Grimes.\" 4. Neither the name of the University nor the names of its contributors
174b88c807SRodney W. Grimes.\"    may be used to endorse or promote products derived from this software
184b88c807SRodney W. Grimes.\"    without specific prior written permission.
194b88c807SRodney W. Grimes.\"
204b88c807SRodney W. Grimes.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
214b88c807SRodney W. Grimes.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
224b88c807SRodney W. Grimes.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
234b88c807SRodney W. Grimes.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
244b88c807SRodney W. Grimes.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
254b88c807SRodney W. Grimes.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
264b88c807SRodney W. Grimes.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
274b88c807SRodney W. Grimes.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
284b88c807SRodney W. Grimes.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
294b88c807SRodney W. Grimes.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
304b88c807SRodney W. Grimes.\" SUCH DAMAGE.
314b88c807SRodney W. Grimes.\"
32ab72124fSSteve Price.\"	from: @(#)sh.1	8.6 (Berkeley) 5/4/95
332a456239SPeter Wemm.\" $FreeBSD$
344b88c807SRodney W. Grimes.\"
35a01459dfSStefan Farfeleder.Dd September 3, 2005
36ab72124fSSteve Price.Dt SH 1
37caa2db3bSRuslan Ermilov.Os
38ab72124fSSteve Price.Sh NAME
39ab72124fSSteve Price.Nm sh
40ab72124fSSteve Price.Nd command interpreter (shell)
41ab72124fSSteve Price.Sh SYNOPSIS
42ab72124fSSteve Price.Nm
437e1975c2STim J. Robbins.Op Fl /+abCEefIimnPpsTuVvx
44ab72124fSSteve Price.Op Fl /+o Ar longname
45c7a197e1SWolfram Schneider.Op Fl c Ar string
4681e9cda2SRuslan Ermilov.Op Ar arg ...
47ab72124fSSteve Price.Sh DESCRIPTION
48e918fc8fSSheldon HearnThe
49e918fc8fSSheldon Hearn.Nm
50e918fc8fSSheldon Hearnutility is the standard command interpreter for the system.
51ab72124fSSteve PriceThe current version of
52ab72124fSSteve Price.Nm
53ab72124fSSteve Priceis in the process of being changed to
54ab72124fSSteve Priceconform with the
55ab72124fSSteve Price.St -p1003.2
56eccea571SRuslan Ermilovspecification for the shell.
57eccea571SRuslan ErmilovThis version has many features which make
58ab72124fSSteve Priceit appear
594b88c807SRodney W. Grimessimilar in some respects to the Korn shell, but it is not a Korn
60fbc8f8a2SJens Schweikhardtshell clone like pdksh.
6149e11e3aSSheldon HearnOnly features
624b88c807SRodney W. Grimesdesignated by POSIX, plus a few Berkeley extensions, are being
63ab72124fSSteve Priceincorporated into this shell.
6449e11e3aSSheldon HearnThis man page is not intended to be a tutorial nor a complete
654b88c807SRodney W. Grimesspecification of the shell.
66ab72124fSSteve Price.Ss Overview
674b88c807SRodney W. GrimesThe shell is a command that reads lines from
684b88c807SRodney W. Grimeseither a file or the terminal, interprets them, and
69e6d3cf26SSheldon Hearngenerally executes other commands.
7049e11e3aSSheldon HearnIt is the program that is started when a user logs into the system,
7149e11e3aSSheldon Hearnalthough a user can select a different shell with the
72c644db6aSSheldon Hearn.Xr chsh 1
7349e11e3aSSheldon Hearncommand.
744b88c807SRodney W. GrimesThe shell
754b88c807SRodney W. Grimesimplements a language that has flow control constructs,
764b88c807SRodney W. Grimesa macro facility that provides a variety of features in
778eed22b1SJens Schweikhardtaddition to data storage, along with built-in history and line
78eccea571SRuslan Ermilovediting capabilities.
79eccea571SRuslan ErmilovIt incorporates many features to
804b88c807SRodney W. Grimesaid interactive use and has the advantage that the interpretative
814b88c807SRodney W. Grimeslanguage is common to both interactive and non-interactive
82eccea571SRuslan Ermilovuse (shell scripts).
83eccea571SRuslan ErmilovThat is, commands can be typed directly
8449e11e3aSSheldon Hearnto the running shell or can be put into a file,
8549e11e3aSSheldon Hearnwhich can be executed directly by the shell.
86ab72124fSSteve Price.Ss Invocation
8749e11e3aSSheldon Hearn.\"
8849e11e3aSSheldon Hearn.\" XXX This next sentence is incredibly confusing.
8949e11e3aSSheldon Hearn.\"
9049e11e3aSSheldon HearnIf no arguments are present and if the standard input of the shell
9149e11e3aSSheldon Hearnis connected to a terminal
9249e11e3aSSheldon Hearn(or if the
9349e11e3aSSheldon Hearn.Fl i
9449e11e3aSSheldon Hearnoption is set),
95eccea571SRuslan Ermilovthe shell is considered an interactive shell.
96eccea571SRuslan ErmilovAn interactive shell
974b88c807SRodney W. Grimesgenerally prompts before each command and handles programming
984b88c807SRodney W. Grimesand command errors differently (as described below).
994b88c807SRodney W. GrimesWhen first starting, the shell inspects argument 0, and
10049e11e3aSSheldon Hearnif it begins with a dash
101a762afe5SGiorgos Keramidas.Pq Ql - ,
10249e11e3aSSheldon Hearnthe shell is also considered a login shell.
10349e11e3aSSheldon HearnThis is normally done automatically by the system
104eccea571SRuslan Ermilovwhen the user first logs in.
105eccea571SRuslan ErmilovA login shell first reads commands
106ab72124fSSteve Pricefrom the files
107ab72124fSSteve Price.Pa /etc/profile
10849e11e3aSSheldon Hearnand then
109ab72124fSSteve Price.Pa .profile
110eccea571SRuslan Ermilovif they exist.
111eccea571SRuslan ErmilovIf the environment variable
112ab72124fSSteve Price.Ev ENV
113ab72124fSSteve Priceis set on entry to a shell, or is set in the
114ab72124fSSteve Price.Pa .profile
11549e11e3aSSheldon Hearnof a login shell, the shell then reads commands from the file named in
116ab72124fSSteve Price.Ev ENV .
117ab72124fSSteve PriceTherefore, a user should place commands that are to be executed only
118ab72124fSSteve Priceat login time in the
119ab72124fSSteve Price.Pa .profile
120ab72124fSSteve Pricefile, and commands that are executed for every shell inside the
121ab72124fSSteve Price.Ev ENV
122e6d3cf26SSheldon Hearnfile.
12349e11e3aSSheldon HearnThe user can set the
124ab72124fSSteve Price.Ev ENV
12549e11e3aSSheldon Hearnvariable to some file by placing the following line in the file
126ab72124fSSteve Price.Pa .profile
12749e11e3aSSheldon Hearnin the home directory,
128ab72124fSSteve Pricesubstituting for
129ab72124fSSteve Price.Pa .shinit
13049e11e3aSSheldon Hearnthe filename desired:
13149e11e3aSSheldon Hearn.Pp
13249e11e3aSSheldon Hearn.Dl ENV=$HOME/.shinit; export ENV
13349e11e3aSSheldon Hearn.Pp
13449e11e3aSSheldon HearnThe first non-option argument specified on the command line
13549e11e3aSSheldon Hearnwill be treated as the
1364b88c807SRodney W. Grimesname of a file from which to read commands (a shell script), and
1374b88c807SRodney W. Grimesthe remaining arguments are set as the positional parameters
138eccea571SRuslan Ermilovof the shell ($1, $2, etc).
139eccea571SRuslan ErmilovOtherwise, the shell reads commands
1404b88c807SRodney W. Grimesfrom its standard input.
141ea76be72SSteve Price.Pp
142ea76be72SSteve PriceUnlike older versions of
143ea76be72SSteve Price.Nm
144ea76be72SSteve Pricethe
145ea76be72SSteve Price.Ev ENV
146eccea571SRuslan Ermilovscript is only sourced on invocation of interactive shells.
147eccea571SRuslan ErmilovThis
148ea76be72SSteve Pricecloses a well-known, and sometimes easily exploitable security
149ea76be72SSteve Pricehole related to poorly thought out
150ea76be72SSteve Price.Ev ENV
151ea76be72SSteve Pricescripts.
152ab72124fSSteve Price.Ss Argument List Processing
153ab72124fSSteve PriceAll of the single letter options to
154ab72124fSSteve Price.Nm
15549e11e3aSSheldon Hearnhave a corresponding long name,
15649e11e3aSSheldon Hearnwith the exception of
15749e11e3aSSheldon Hearn.Fl c
15849e11e3aSSheldon Hearnand
15949e11e3aSSheldon Hearn.Fl /+o .
16049e11e3aSSheldon HearnThese long names are provided next to the single letter options
16149e11e3aSSheldon Hearnin the descriptions below.
16249e11e3aSSheldon HearnThe long name for an option may be specified as an argument to the
16349e11e3aSSheldon Hearn.Fl /+o
16449e11e3aSSheldon Hearnoption of
165facc6767SRuslan Ermilov.Nm .
16649e11e3aSSheldon HearnOnce the shell is running,
16749e11e3aSSheldon Hearnthe long name for an option may be specified as an argument to the
16849e11e3aSSheldon Hearn.Fl /+o
16949e11e3aSSheldon Hearnoption of the
170c644db6aSSheldon Hearn.Ic set
1718eed22b1SJens Schweikhardtbuilt-in command
17249e11e3aSSheldon Hearn(described later in the section called
1738eed22b1SJens Schweikhardt.Sx Built-in Commands ) .
17449e11e3aSSheldon HearnIntroducing an option with a dash
175a762afe5SGiorgos Keramidas.Pq Ql -
17649e11e3aSSheldon Hearnenables the option,
17749e11e3aSSheldon Hearnwhile using a plus
178a762afe5SGiorgos Keramidas.Pq Ql +
17949e11e3aSSheldon Hearndisables the option.
18049e11e3aSSheldon HearnA
18149e11e3aSSheldon Hearn.Dq Li --
182fab26805SJoseph Koshyor plain
183a762afe5SGiorgos Keramidas.Dq Ql -
184fab26805SJoseph Koshywill stop option processing and will force the remaining
185fab26805SJoseph Koshywords on the command line to be treated as arguments.
18649e11e3aSSheldon HearnThe
18749e11e3aSSheldon Hearn.Fl /+o
18849e11e3aSSheldon Hearnand
18949e11e3aSSheldon Hearn.Fl c
19049e11e3aSSheldon Hearnoptions do not have long names.
19149e11e3aSSheldon HearnThey take arguments and are described after the single letter options.
19281e9cda2SRuslan Ermilov.Bl -tag -width indent
193ab72124fSSteve Price.It Fl a Li allexport
19449e11e3aSSheldon HearnFlag variables for export when assignments are made to them.
195ab72124fSSteve Price.It Fl b Li notify
196ab72124fSSteve PriceEnable asynchronous notification of background job
197ab72124fSSteve Pricecompletion.
198c4d9468eSRuslan Ermilov(UNIMPLEMENTED)
199ab72124fSSteve Price.It Fl C Li noclobber
200c644db6aSSheldon HearnDo not overwrite existing files with
20149e11e3aSSheldon Hearn.Dq Li > .
202ab72124fSSteve Price.It Fl E Li emacs
2038eed22b1SJens SchweikhardtEnable the built-in
204ab72124fSSteve Price.Xr emacs 1
20549e11e3aSSheldon Hearncommand line editor (disables the
206ab72124fSSteve Price.Fl V
20749e11e3aSSheldon Hearnoption if it has been set).
208ab72124fSSteve Price.It Fl e Li errexit
20949e11e3aSSheldon HearnExit immediately if any untested command fails in non-interactive mode.
2104b88c807SRodney W. GrimesThe exit status of a command is considered to be
2114b88c807SRodney W. Grimesexplicitly tested if the command is used to control
2124b88c807SRodney W. Grimesan if, elif, while, or until; or if the command is the left
213ab72124fSSteve Pricehand operand of an
21449e11e3aSSheldon Hearn.Dq Li &&
215ab72124fSSteve Priceor
21649e11e3aSSheldon Hearn.Dq Li ||
217ab72124fSSteve Priceoperator.
218ab72124fSSteve Price.It Fl f Li noglob
2194b88c807SRodney W. GrimesDisable pathname expansion.
220ab72124fSSteve Price.It Fl I Li ignoreeof
22149e11e3aSSheldon HearnIgnore
22249e11e3aSSheldon Hearn.Dv EOF Ns ' Ns s
22349e11e3aSSheldon Hearnfrom input when in interactive mode.
224ab72124fSSteve Price.It Fl i Li interactive
225ab72124fSSteve PriceForce the shell to behave interactively.
226ab72124fSSteve Price.It Fl m Li monitor
227ab72124fSSteve PriceTurn on job control (set automatically when interactive).
228ab72124fSSteve Price.It Fl n Li noexec
2294b88c807SRodney W. GrimesIf not interactive, read commands but do not
230eccea571SRuslan Ermilovexecute them.
231eccea571SRuslan ErmilovThis is useful for checking the
2324b88c807SRodney W. Grimessyntax of shell scripts.
2337e1975c2STim J. Robbins.It Fl P Li physical
2347e1975c2STim J. RobbinsChange the default for the
2357e1975c2STim J. Robbins.Ic cd
2367e1975c2STim J. Robbinsand
2377e1975c2STim J. Robbins.Ic pwd
2387e1975c2STim J. Robbinscommands from
2397e1975c2STim J. Robbins.Fl L
2407e1975c2STim J. Robbins(logical directory layout)
2417e1975c2STim J. Robbinsto
2427e1975c2STim J. Robbins.Fl P
2437e1975c2STim J. Robbins(physical directory layout).
244ab72124fSSteve Price.It Fl p Li privileged
245eccea571SRuslan ErmilovTurn on privileged mode.
246eccea571SRuslan ErmilovThis mode is enabled on startup
247621a31c6SSteve Priceif either the effective user or group id is not equal to the
248eccea571SRuslan Ermilovreal user or group id.
249eccea571SRuslan ErmilovTurning this mode off sets the
250621a31c6SSteve Priceeffective user and group ids to the real user and group ids.
25149e11e3aSSheldon HearnWhen this mode is enabled for interactive shells, the file
252ab72124fSSteve Price.Pa /etc/suid_profile
25349e11e3aSSheldon Hearnis sourced instead of
25449e11e3aSSheldon Hearn.Pa ~/.profile
255ab72124fSSteve Priceafter
256ab72124fSSteve Price.Pa /etc/profile
25749e11e3aSSheldon Hearnis sourced, and the contents of the
258ab72124fSSteve Price.Ev ENV
25949e11e3aSSheldon Hearnvariable are ignored.
260ab72124fSSteve Price.It Fl s Li stdin
2614b88c807SRodney W. GrimesRead commands from standard input (set automatically
262eccea571SRuslan Ermilovif no file arguments are present).
263eccea571SRuslan ErmilovThis option has
2644b88c807SRodney W. Grimesno effect when set after the shell has already started
265eccea571SRuslan Ermilovrunning (i.e., when set with the
266c644db6aSSheldon Hearn.Ic set
2676b15476eSSheldon Hearncommand).
268304199ceSTom Rhodes.It Fl T Li trapsasync
269e6d3cf26SSheldon HearnWhen waiting for a child, execute traps immediately.
270e6d3cf26SSheldon HearnIf this option is not set,
271e6d3cf26SSheldon Hearntraps are executed after the child exits,
272e6d3cf26SSheldon Hearnas specified in
273af5eb6fcSMaxim Konovalov.St -p1003.2 .
2746b15476eSSheldon HearnThis nonstandard option is useful for putting guarding shells around
275eccea571SRuslan Ermilovchildren that block signals.
276eccea571SRuslan ErmilovThe surrounding shell may kill the child
2776b15476eSSheldon Hearnor it may just return control to the tty and leave the child alone,
2786b15476eSSheldon Hearnlike this:
279c1c72a3cSMartin Cracauer.Bd -literal -offset indent
280c1c72a3cSMartin Cracauersh -T -c "trap 'exit 1' 2 ; some-blocking-program"
281c1c72a3cSMartin Cracauer.Ed
282c1c72a3cSMartin Cracauer.Pp
283ab72124fSSteve Price.It Fl u Li nounset
284ab72124fSSteve PriceWrite a message to standard error when attempting
285ab72124fSSteve Priceto expand a variable that is not set, and if the
286ab72124fSSteve Priceshell is not interactive, exit immediately.
287ab72124fSSteve Price.It Fl V Li vi
2888eed22b1SJens SchweikhardtEnable the built-in
289ab72124fSSteve Price.Xr vi 1
290ab72124fSSteve Pricecommand line editor (disables
291ab72124fSSteve Price.Fl E
292ab72124fSSteve Priceif it has been set).
293ab72124fSSteve Price.It Fl v Li verbose
294ab72124fSSteve PriceThe shell writes its input to standard error
295eccea571SRuslan Ermilovas it is read.
296eccea571SRuslan ErmilovUseful for debugging.
297ab72124fSSteve Price.It Fl x Li xtrace
29849e11e3aSSheldon HearnWrite each command
29949e11e3aSSheldon Hearn(preceded by
3006fa13ec0SRuslan Ermilov.Dq Li "+ " )
30149e11e3aSSheldon Hearnto standard error before it is executed.
30249e11e3aSSheldon HearnUseful for debugging.
30349e11e3aSSheldon Hearn.El
30449e11e3aSSheldon Hearn.Pp
30549e11e3aSSheldon HearnThe
306fd50df30SRuslan Ermilov.Fl c
307fd50df30SRuslan Ermilovoption causes the commands to be read from the
308fd50df30SRuslan Ermilov.Ar string
309fd50df30SRuslan Ermilovoperand instead of from the standard input.
310fd50df30SRuslan ErmilovKeep in mind that this option only accepts a single string as its
311fd50df30SRuslan Ermilovargument, hence multi-word strings must be quoted.
312fd50df30SRuslan Ermilov.Pp
313fd50df30SRuslan ErmilovThe
31449e11e3aSSheldon Hearn.Fl /+o
31549e11e3aSSheldon Hearnoption takes as its only argument the long name of an option
31649e11e3aSSheldon Hearnto be enabled or disabled.
31749e11e3aSSheldon HearnFor example, the following two invocations of
31849e11e3aSSheldon Hearn.Nm
3198eed22b1SJens Schweikhardtboth enable the built-in
32049e11e3aSSheldon Hearn.Xr emacs 1
32149e11e3aSSheldon Hearncommand line editor:
32249e11e3aSSheldon Hearn.Bd -literal -offset indent
32349e11e3aSSheldon Hearnset -E
32449e11e3aSSheldon Hearnset -o emacs
32549e11e3aSSheldon Hearn.Ed
326d513af6aSTim J. Robbins.Pp
327d513af6aSTim J. RobbinsIf used without an argument, the
328d513af6aSTim J. Robbins.Fl o
329d513af6aSTim J. Robbinsoption displays the current option settings in a human-readable format.
330d513af6aSTim J. RobbinsIf
331d513af6aSTim J. Robbins.Cm +o
332d513af6aSTim J. Robbinsis used without an argument, the current option settings are output
333d513af6aSTim J. Robbinsin a format suitable for re-input into the shell.
334ab72124fSSteve Price.Ss Lexical Structure
3354b88c807SRodney W. GrimesThe shell reads input in terms of lines from a file and breaks
3364b88c807SRodney W. Grimesit up into words at whitespace (blanks and tabs), and at
3374b88c807SRodney W. Grimescertain sequences of
3386b15476eSSheldon Hearncharacters called
3396b15476eSSheldon Hearn.Dq operators ,
3406b15476eSSheldon Hearnwhich are special to the shell.
3414b88c807SRodney W. GrimesThere are two types of operators: control operators and
3424b88c807SRodney W. Grimesredirection operators (their meaning is discussed later).
343ab72124fSSteve PriceThe following is a list of valid operators:
34481e9cda2SRuslan Ermilov.Bl -tag -width indent
34549e11e3aSSheldon Hearn.It Control operators:
34649e11e3aSSheldon Hearn.Bl -column "XXX" "XXX" "XXX" "XXX" "XXX" -offset center -compact
34781e9cda2SRuslan Ermilov.It Li & Ta Li && Ta Li ( Ta Li ) Ta Li \en
34881e9cda2SRuslan Ermilov.It Li ;; Ta Li ; Ta Li | Ta Li ||
34949e11e3aSSheldon Hearn.El
35049e11e3aSSheldon Hearn.It Redirection operators:
3514682f420SBrian Somers.Bl -column "XXX" "XXX" "XXX" "XXX" "XXX" -offset center -compact
35281e9cda2SRuslan Ermilov.It Li < Ta Li > Ta Li << Ta Li >> Ta Li <>
35381e9cda2SRuslan Ermilov.It Li <& Ta Li >& Ta Li <<- Ta Li >|
35449e11e3aSSheldon Hearn.El
355ab72124fSSteve Price.El
356ab72124fSSteve Price.Ss Quoting
3574b88c807SRodney W. GrimesQuoting is used to remove the special meaning of certain characters
358a886288eSJesus R. Camouor words to the shell, such as operators, whitespace, keywords,
359a886288eSJesus R. Camouor alias names.
360a886288eSJesus R. Camou.Pp
361eccea571SRuslan ErmilovThere are three types of quoting: matched single quotes,
3624b88c807SRodney W. Grimesmatched double quotes, and backslash.
36381e9cda2SRuslan Ermilov.Bl -tag -width indent
364ab72124fSSteve Price.It Single Quotes
3654b88c807SRodney W. GrimesEnclosing characters in single quotes preserves the literal
366ab0a2172SSteve Pricemeaning of all the characters (except single quotes, making
367ab0a2172SSteve Priceit impossible to put single-quotes in a single-quoted string).
368ab72124fSSteve Price.It Double Quotes
3694b88c807SRodney W. GrimesEnclosing characters within double quotes preserves the literal
37049e11e3aSSheldon Hearnmeaning of all characters except dollarsign
371a762afe5SGiorgos Keramidas.Pq Ql $ ,
37249e11e3aSSheldon Hearnbackquote
373a762afe5SGiorgos Keramidas.Pq Ql ` ,
37449e11e3aSSheldon Hearnand backslash
375a762afe5SGiorgos Keramidas.Pq Ql \e .
37649e11e3aSSheldon HearnThe backslash inside double quotes is historically weird.
37749e11e3aSSheldon HearnIt remains literal unless it precedes the following characters,
37849e11e3aSSheldon Hearnwhich it serves to quote:
37949e11e3aSSheldon Hearn.Bl -column "XXX" "XXX" "XXX" "XXX" "XXX" -offset center -compact
38081e9cda2SRuslan Ermilov.It Li $ Ta Li ` Ta Li \&" Ta Li \e\  Ta Li \en
38149e11e3aSSheldon Hearn.El
382ab72124fSSteve Price.It Backslash
383ab72124fSSteve PriceA backslash preserves the literal meaning of the following
38449e11e3aSSheldon Hearncharacter, with the exception of the newline character
385a762afe5SGiorgos Keramidas.Pq Ql \en .
38649e11e3aSSheldon HearnA backslash preceding a newline is treated as a line continuation.
387ab72124fSSteve Price.El
388ab72124fSSteve Price.Ss Reserved Words
3894b88c807SRodney W. GrimesReserved words are words that have special meaning to the
3904b88c807SRodney W. Grimesshell and are recognized at the beginning of a line and
391eccea571SRuslan Ermilovafter a control operator.
392eccea571SRuslan ErmilovThe following are reserved words:
39349e11e3aSSheldon Hearn.Bl -column "doneXX" "elifXX" "elseXX" "untilXX" "whileX" -offset center
39481e9cda2SRuslan Ermilov.It Li \&! Ta { Ta } Ta Ic case Ta Ic do
39581e9cda2SRuslan Ermilov.It Ic done Ta Ic elif Ta Ic else Ta Ic esac Ta Ic fi
39681e9cda2SRuslan Ermilov.It Ic for Ta Ic if Ta Ic then Ta Ic until Ta Ic while
39749e11e3aSSheldon Hearn.El
398ab72124fSSteve Price.Ss Aliases
399ab72124fSSteve PriceAn alias is a name and corresponding value set using the
400c644db6aSSheldon Hearn.Ic alias
401eccea571SRuslan Ermilovbuilt-in command.
402eccea571SRuslan ErmilovWhenever a reserved word may occur (see above),
4034b88c807SRodney W. Grimesand after checking for reserved words, the shell
404e6d3cf26SSheldon Hearnchecks the word to see if it matches an alias.
405e6d3cf26SSheldon HearnIf it does, it replaces it in the input stream with its value.
406e6d3cf26SSheldon HearnFor example, if there is an alias called
40749e11e3aSSheldon Hearn.Dq Li lf
4086b15476eSSheldon Hearnwith the value
40949e11e3aSSheldon Hearn.Dq Li ls -F ,
4104b88c807SRodney W. Grimesthen the input
411ab72124fSSteve Price.Bd -literal -offset indent
41249e11e3aSSheldon Hearnlf foobar
413ab72124fSSteve Price.Ed
414ab72124fSSteve Price.Pp
4154b88c807SRodney W. Grimeswould become
416ab72124fSSteve Price.Bd -literal -offset indent
41749e11e3aSSheldon Hearnls -F foobar
418ab72124fSSteve Price.Ed
419ab72124fSSteve Price.Pp
4204b88c807SRodney W. GrimesAliases provide a convenient way for naive users to
4214b88c807SRodney W. Grimescreate shorthands for commands without having to learn how
422eccea571SRuslan Ermilovto create functions with arguments.
423eccea571SRuslan ErmilovThey can also be
424eccea571SRuslan Ermilovused to create lexically obscure code.
425eccea571SRuslan ErmilovThis use is discouraged.
426a886288eSJesus R. Camou.Pp
427a886288eSJesus R. CamouAn alias name may be escaped in a command line, so that it is not
428a886288eSJesus R. Camoureplaced by its alias value, by using quoting characters within or
42919162ab9SJesus R. Camouadjacent to the alias name.
43019162ab9SJesus R. CamouThis is most often done by prefixing
431a886288eSJesus R. Camouan alias name with a backslash to execute a function, built-in, or
432a886288eSJesus R. Camounormal program with the same name.
433a886288eSJesus R. CamouSee the
434a886288eSJesus R. Camou.Sx Quoting
435a886288eSJesus R. Camousubsection.
436ab72124fSSteve Price.Ss Commands
4374b88c807SRodney W. GrimesThe shell interprets the words it reads according to a
4384b88c807SRodney W. Grimeslanguage, the specification of which is outside the scope
439ab72124fSSteve Priceof this man page (refer to the BNF in the
440ab72124fSSteve Price.St -p1003.2
441eccea571SRuslan Ermilovdocument).
442eccea571SRuslan ErmilovEssentially though, a line is read and if
4434b88c807SRodney W. Grimesthe first word of the line (or after a control operator)
4444b88c807SRodney W. Grimesis not a reserved word, then the shell has recognized a
445eccea571SRuslan Ermilovsimple command.
446eccea571SRuslan ErmilovOtherwise, a complex command or some
4474b88c807SRodney W. Grimesother special construct may have been recognized.
448ab72124fSSteve Price.Ss Simple Commands
4494b88c807SRodney W. GrimesIf a simple command has been recognized, the shell performs
4504b88c807SRodney W. Grimesthe following actions:
451ab72124fSSteve Price.Bl -enum
452ab72124fSSteve Price.It
4536b15476eSSheldon HearnLeading words of the form
45449e11e3aSSheldon Hearn.Dq Li name=value
4556b15476eSSheldon Hearnare stripped off and assigned to the environment of
456eccea571SRuslan Ermilovthe simple command.
457eccea571SRuslan ErmilovRedirection operators and
4584b88c807SRodney W. Grimestheir arguments (as described below) are stripped
4594b88c807SRodney W. Grimesoff and saved for processing.
460ab72124fSSteve Price.It
461ab72124fSSteve PriceThe remaining words are expanded as described in
4626b15476eSSheldon Hearnthe section called
4636b15476eSSheldon Hearn.Sx Word Expansions ,
4646b15476eSSheldon Hearnand the first remaining word is considered the command
465eccea571SRuslan Ermilovname and the command is located.
466eccea571SRuslan ErmilovThe remaining
4674b88c807SRodney W. Grimeswords are considered the arguments of the command.
4686b15476eSSheldon HearnIf no command name resulted, then the
46949e11e3aSSheldon Hearn.Dq Li name=value
4704b88c807SRodney W. Grimesvariable assignments recognized in 1) affect the
4714b88c807SRodney W. Grimescurrent shell.
472ab72124fSSteve Price.It
473ab72124fSSteve PriceRedirections are performed as described in
4744b88c807SRodney W. Grimesthe next section.
475ab72124fSSteve Price.El
476ab72124fSSteve Price.Ss Redirections
4774b88c807SRodney W. GrimesRedirections are used to change where a command reads its input
478eccea571SRuslan Ermilovor sends its output.
479eccea571SRuslan ErmilovIn general, redirections open, close, or
480eccea571SRuslan Ermilovduplicate an existing reference to a file.
481eccea571SRuslan ErmilovThe overall format
4824b88c807SRodney W. Grimesused for redirection is:
48349e11e3aSSheldon Hearn.Pp
484ab72124fSSteve Price.Dl [n] redir-op file
48549e11e3aSSheldon Hearn.Pp
48649e11e3aSSheldon HearnThe
48749e11e3aSSheldon Hearn.Ql redir-op
48849e11e3aSSheldon Hearnis one of the redirection operators mentioned
489eccea571SRuslan Ermilovpreviously.
490eccea571SRuslan ErmilovThe following gives some examples of how these
49149e11e3aSSheldon Hearnoperators can be used.
49249e11e3aSSheldon HearnNote that stdin and stdout are commonly used abbreviations
49349e11e3aSSheldon Hearnfor standard input and standard output respectively.
49449e11e3aSSheldon Hearn.Bl -tag -width "1234567890XX" -offset indent
49549e11e3aSSheldon Hearn.It Li [n]> file
49649e11e3aSSheldon Hearnredirect stdout (or file descriptor n) to file
49749e11e3aSSheldon Hearn.It Li [n]>| file
49849e11e3aSSheldon Hearnsame as above, but override the
49949e11e3aSSheldon Hearn.Fl C
50049e11e3aSSheldon Hearnoption
50149e11e3aSSheldon Hearn.It Li [n]>> file
50249e11e3aSSheldon Hearnappend stdout (or file descriptor n) to file
50349e11e3aSSheldon Hearn.It Li [n]< file
50449e11e3aSSheldon Hearnredirect stdin (or file descriptor n) from file
5054682f420SBrian Somers.It Li [n]<> file
5064682f420SBrian Somersredirect stdin (or file descriptor n) to and from file
50749e11e3aSSheldon Hearn.It Li [n1]<&n2
50849e11e3aSSheldon Hearnduplicate stdin (or file descriptor n1) from file descriptor n2
50949e11e3aSSheldon Hearn.It Li [n]<&-
51049e11e3aSSheldon Hearnclose stdin (or file descriptor n)
51149e11e3aSSheldon Hearn.It Li [n1]>&n2
51249e11e3aSSheldon Hearnduplicate stdout (or file descriptor n1) to file descriptor n2
51349e11e3aSSheldon Hearn.It Li [n]>&-
51449e11e3aSSheldon Hearnclose stdout (or file descriptor n)
515ab72124fSSteve Price.El
516ab72124fSSteve Price.Pp
5176b15476eSSheldon HearnThe following redirection is often called a
5186b15476eSSheldon Hearn.Dq here-document .
519ab72124fSSteve Price.Bd -literal -offset indent
5204b88c807SRodney W. Grimes[n]<< delimiter
52149e11e3aSSheldon Hearn	here-doc-text
52249e11e3aSSheldon Hearn	...
5234b88c807SRodney W. Grimesdelimiter
524ab72124fSSteve Price.Ed
525ab72124fSSteve Price.Pp
5264b88c807SRodney W. GrimesAll the text on successive lines up to the delimiter is
5274b88c807SRodney W. Grimessaved away and made available to the command on standard
528eccea571SRuslan Ermilovinput, or file descriptor n if it is specified.
529eccea571SRuslan ErmilovIf the delimiter
5304b88c807SRodney W. Grimesas specified on the initial line is quoted, then the here-doc-text
5314b88c807SRodney W. Grimesis treated literally, otherwise the text is subjected to
5324b88c807SRodney W. Grimesparameter expansion, command substitution, and arithmetic
5336b15476eSSheldon Hearnexpansion (as described in the section on
5346b15476eSSheldon Hearn.Sx Word Expansions ) .
5356b15476eSSheldon HearnIf the operator is
53649e11e3aSSheldon Hearn.Dq Li <<-
5376b15476eSSheldon Hearninstead of
53849e11e3aSSheldon Hearn.Dq Li << ,
5396b15476eSSheldon Hearnthen leading tabs
5404b88c807SRodney W. Grimesin the here-doc-text are stripped.
541ab72124fSSteve Price.Ss Search and Execution
542ab0a2172SSteve PriceThere are three types of commands: shell functions,
5438eed22b1SJens Schweikhardtbuilt-in commands, and normal programs.
54449e11e3aSSheldon HearnThe command is searched for (by name) in that order.
54549e11e3aSSheldon HearnThe three types of commands are all executed in a different way.
546ab72124fSSteve Price.Pp
547ab0a2172SSteve PriceWhen a shell function is executed, all of the shell positional
548ab0a2172SSteve Priceparameters (except $0, which remains unchanged) are
5494b88c807SRodney W. Grimesset to the arguments of the shell function.
5504b88c807SRodney W. GrimesThe variables which are explicitly placed in the environment of
5514b88c807SRodney W. Grimesthe command (by placing assignments to them before the
5524b88c807SRodney W. Grimesfunction name) are made local to the function and are set
553e6d3cf26SSheldon Hearnto the values given.
554e6d3cf26SSheldon HearnThen the command given in the function definition is executed.
555e6d3cf26SSheldon HearnThe positional parameters are restored to their original values
556e6d3cf26SSheldon Hearnwhen the command completes.
557ab0a2172SSteve PriceThis all occurs within the current shell.
558ab72124fSSteve Price.Pp
5598eed22b1SJens SchweikhardtShell built-in commands are executed internally to the shell, without
560ab0a2172SSteve Pricespawning a new process.
561ab72124fSSteve Price.Pp
562c644db6aSSheldon HearnOtherwise, if the command name does not match a function
5638eed22b1SJens Schweikhardtor built-in command, the command is searched for as a normal
5644b88c807SRodney W. Grimesprogram in the file system (as described in the next section).
5654b88c807SRodney W. GrimesWhen a normal program is executed, the shell runs the program,
566e6d3cf26SSheldon Hearnpassing the arguments and the environment to the program.
567e6d3cf26SSheldon HearnIf the program is not a normal executable file
568eccea571SRuslan Ermilov(i.e., if it does not begin with the
5696b15476eSSheldon Hearn.Qq magic number
5706b15476eSSheldon Hearnwhose
571ab72124fSSteve Price.Tn ASCII
5726b15476eSSheldon Hearnrepresentation is
5736b15476eSSheldon Hearn.Qq #! ,
57449e11e3aSSheldon Hearnresulting in an
575b4f0f4aaSRuslan Ermilov.Er ENOEXEC
57649e11e3aSSheldon Hearnreturn value from
57749e11e3aSSheldon Hearn.Xr execve 2 )
578e6d3cf26SSheldon Hearnthe shell will interpret the program in a subshell.
579e6d3cf26SSheldon HearnThe child shell will reinitialize itself in this case,
580e6d3cf26SSheldon Hearnso that the effect will be
581e6d3cf26SSheldon Hearnas if a new shell had been invoked to handle the ad-hoc shell script,
582e6d3cf26SSheldon Hearnexcept that the location of hashed commands located in
5834b88c807SRodney W. Grimesthe parent shell will be remembered by the child.
584ab72124fSSteve Price.Pp
585ab0a2172SSteve PriceNote that previous versions of this document
586ab0a2172SSteve Priceand the source code itself misleadingly and sporadically
587ab0a2172SSteve Pricerefer to a shell script without a magic number
5886b15476eSSheldon Hearnas a
5896b15476eSSheldon Hearn.Qq shell procedure .
590ab72124fSSteve Price.Ss Path Search
5914b88c807SRodney W. GrimesWhen locating a command, the shell first looks to see if
592eccea571SRuslan Ermilovit has a shell function by that name.
593eccea571SRuslan ErmilovThen it looks for a
594eccea571SRuslan Ermilovbuilt-in command by that name.
595eccea571SRuslan ErmilovIf a built-in command is not found,
596ab0a2172SSteve Priceone of two things happen:
597ab72124fSSteve Price.Bl -enum
598ab72124fSSteve Price.It
599ab72124fSSteve PriceCommand names containing a slash are simply executed without
600ab0a2172SSteve Priceperforming any searches.
601ab72124fSSteve Price.It
602ab72124fSSteve PriceThe shell searches each entry in
603ab72124fSSteve Price.Ev PATH
604eccea571SRuslan Ermilovin turn for the command.
605eccea571SRuslan ErmilovThe value of the
606ab72124fSSteve Price.Ev PATH
607ab72124fSSteve Pricevariable should be a series of
608eccea571SRuslan Ermiloventries separated by colons.
609eccea571SRuslan ErmilovEach entry consists of a
6104b88c807SRodney W. Grimesdirectory name.
6114b88c807SRodney W. GrimesThe current directory
612ab0a2172SSteve Pricemay be indicated implicitly by an empty directory name,
613ab0a2172SSteve Priceor explicitly by a single period.
614ab72124fSSteve Price.El
615ab72124fSSteve Price.Ss Command Exit Status
6164b88c807SRodney W. GrimesEach command has an exit status that can influence the behavior
617eccea571SRuslan Ermilovof other shell commands.
618eccea571SRuslan ErmilovThe paradigm is that a command exits
6194b88c807SRodney W. Grimeswith zero for normal or success, and non-zero for failure,
620eccea571SRuslan Ermiloverror, or a false indication.
621eccea571SRuslan ErmilovThe man page for each command
6224b88c807SRodney W. Grimesshould indicate the various exit codes and what they mean.
6238eed22b1SJens SchweikhardtAdditionally, the built-in commands return exit codes, as does
624ab0a2172SSteve Pricean executed shell function.
625c351e089SJohn Polstra.Pp
626c351e089SJohn PolstraIf a command is terminated by a signal, its exit status is 128 plus
627eccea571SRuslan Ermilovthe signal number.
628eccea571SRuslan ErmilovSignal numbers are defined in the header file
629fe08efe6SRuslan Ermilov.In sys/signal.h .
630ab72124fSSteve Price.Ss Complex Commands
6314b88c807SRodney W. GrimesComplex commands are combinations of simple commands
6324b88c807SRodney W. Grimeswith control operators or reserved words, together creating a larger complex
633eccea571SRuslan Ermilovcommand.
634eccea571SRuslan ErmilovMore generally, a command is one of the following:
635ab72124fSSteve Price.Bl -item -offset indent
636ab72124fSSteve Price.It
637ab72124fSSteve Pricesimple command
638ab72124fSSteve Price.It
639ab72124fSSteve Pricepipeline
640ab72124fSSteve Price.It
641ab72124fSSteve Pricelist or compound-list
642ab72124fSSteve Price.It
643ab72124fSSteve Pricecompound command
644ab72124fSSteve Price.It
645ab72124fSSteve Pricefunction definition
646ab72124fSSteve Price.El
647ab72124fSSteve Price.Pp
6484b88c807SRodney W. GrimesUnless otherwise stated, the exit status of a command is
6494b88c807SRodney W. Grimesthat of the last simple command executed by the command.
650ab72124fSSteve Price.Ss Pipelines
6514b88c807SRodney W. GrimesA pipeline is a sequence of one or more commands separated
652eccea571SRuslan Ermilovby the control operator |.
653eccea571SRuslan ErmilovThe standard output of all but
6544b88c807SRodney W. Grimesthe last command is connected to the standard input
655eccea571SRuslan Ermilovof the next command.
656eccea571SRuslan ErmilovThe standard output of the last
657ab0a2172SSteve Pricecommand is inherited from the shell, as usual.
658ab72124fSSteve Price.Pp
6594b88c807SRodney W. GrimesThe format for a pipeline is:
66049e11e3aSSheldon Hearn.Pp
66149e11e3aSSheldon Hearn.Dl [!] command1 [ | command2 ...]
662ab72124fSSteve Price.Pp
6634b88c807SRodney W. GrimesThe standard output of command1 is connected to the standard
664eccea571SRuslan Ermilovinput of command2.
665eccea571SRuslan ErmilovThe standard input, standard output, or
6664b88c807SRodney W. Grimesboth of a command is considered to be assigned by the
6674b88c807SRodney W. Grimespipeline before any redirection specified by redirection
6684b88c807SRodney W. Grimesoperators that are part of the command.
669ab72124fSSteve Price.Pp
6704b88c807SRodney W. GrimesIf the pipeline is not in the background (discussed later),
6714b88c807SRodney W. Grimesthe shell waits for all commands to complete.
672ab72124fSSteve Price.Pp
673eccea571SRuslan ErmilovIf the reserved word
674eccea571SRuslan Ermilov.Ic !\&
675eccea571SRuslan Ermilovdoes not precede the pipeline, the
6764b88c807SRodney W. Grimesexit status is the exit status of the last command specified
677eccea571SRuslan Ermilovin the pipeline.
678eccea571SRuslan ErmilovOtherwise, the exit status is the logical
679eccea571SRuslan ErmilovNOT of the exit status of the last command.
680eccea571SRuslan ErmilovThat is, if
6814b88c807SRodney W. Grimesthe last command returns zero, the exit status is 1; if
6824b88c807SRodney W. Grimesthe last command returns greater than zero, the exit status
6834b88c807SRodney W. Grimesis zero.
684ab72124fSSteve Price.Pp
6854b88c807SRodney W. GrimesBecause pipeline assignment of standard input or standard
6864b88c807SRodney W. Grimesoutput or both takes place before redirection, it can be
687eccea571SRuslan Ermilovmodified by redirection.
688eccea571SRuslan ErmilovFor example:
689ab72124fSSteve Price.Pp
69049e11e3aSSheldon Hearn.Dl $ command1 2>&1 | command2
691ab72124fSSteve Price.Pp
69249e11e3aSSheldon Hearnsends both the standard output and standard error of
69349e11e3aSSheldon Hearn.Ql command1
69449e11e3aSSheldon Hearnto the standard input of
69549e11e3aSSheldon Hearn.Ql command2 .
69649e11e3aSSheldon Hearn.Pp
69749e11e3aSSheldon HearnA
69812e720d7SRuslan Ermilov.Dq Li \&;
69949e11e3aSSheldon Hearnor newline terminator causes the preceding
700e918fc8fSSheldon HearnAND-OR-list
701e918fc8fSSheldon Hearn(described below in the section called
702e918fc8fSSheldon Hearn.Sx Short-Circuit List Operators )
703e918fc8fSSheldon Hearnto be executed sequentially;
704e918fc8fSSheldon Hearnan
705e918fc8fSSheldon Hearn.Dq Li &
706e918fc8fSSheldon Hearncauses asynchronous execution of the preceding AND-OR-list.
707ab72124fSSteve Price.Pp
70849e11e3aSSheldon HearnNote that unlike some other shells,
70949e11e3aSSheldon Hearn.Nm
71049e11e3aSSheldon Hearnexecutes each process in the pipeline as a child of the
71149e11e3aSSheldon Hearn.Nm
71249e11e3aSSheldon Hearnprocess.
7138eed22b1SJens SchweikhardtShell built-in commands are the exception to this rule.
71449e11e3aSSheldon HearnThey are executed in the current shell, although they do not affect its
71549e11e3aSSheldon Hearnenvironment when used in pipelines.
71649e11e3aSSheldon Hearn.Ss Background Commands (&)
7174b88c807SRodney W. GrimesIf a command is terminated by the control operator ampersand
718a762afe5SGiorgos Keramidas.Pq Ql & ,
71949e11e3aSSheldon Hearnthe shell executes the command asynchronously;
72049e11e3aSSheldon Hearnthe shell does not wait for the command to finish
72149e11e3aSSheldon Hearnbefore executing the next command.
722ab72124fSSteve Price.Pp
7234b88c807SRodney W. GrimesThe format for running a command in background is:
724ab72124fSSteve Price.Bd -literal -offset indent
7254b88c807SRodney W. Grimescommand1 & [command2 & ...]
726ab72124fSSteve Price.Ed
727ab72124fSSteve Price.Pp
7284b88c807SRodney W. GrimesIf the shell is not interactive, the standard input of an
7294b88c807SRodney W. Grimesasynchronous command is set to /dev/null.
73049e11e3aSSheldon Hearn.Ss Lists (Generally Speaking)
7314b88c807SRodney W. GrimesA list is a sequence of zero or more commands separated by
7324b88c807SRodney W. Grimesnewlines, semicolons, or ampersands,
7334b88c807SRodney W. Grimesand optionally terminated by one of these three characters.
7344b88c807SRodney W. GrimesThe commands in a
7354b88c807SRodney W. Grimeslist are executed in the order they are written.
7364b88c807SRodney W. GrimesIf command is followed by an ampersand, the shell starts the
7378eed22b1SJens Schweikhardtcommand and immediately proceeds onto the next command;
7384b88c807SRodney W. Grimesotherwise it waits for the command to terminate before
7394b88c807SRodney W. Grimesproceeding to the next one.
740ab72124fSSteve Price.Ss Short-Circuit List Operators
74149e11e3aSSheldon Hearn.Dq Li &&
7426b15476eSSheldon Hearnand
74349e11e3aSSheldon Hearn.Dq Li ||
7446b15476eSSheldon Hearnare AND-OR list operators.
74549e11e3aSSheldon Hearn.Dq Li &&
7466b15476eSSheldon Hearnexecutes the first command, and then executes the second command
7476b15476eSSheldon Hearnif the exit status of the first command is zero.
74849e11e3aSSheldon Hearn.Dq Li ||
749120ac26dSMasafumi Max NAKANEis similar, but executes the second command if the exit
7506b15476eSSheldon Hearnstatus of the first command is nonzero.
75149e11e3aSSheldon Hearn.Dq Li &&
7526b15476eSSheldon Hearnand
75349e11e3aSSheldon Hearn.Dq Li ||
7544b88c807SRodney W. Grimesboth have the same priority.
75549e11e3aSSheldon Hearn.Ss Flow-Control Constructs (if, while, for, case)
75649e11e3aSSheldon HearnThe syntax of the
75749e11e3aSSheldon Hearn.Ic if
75849e11e3aSSheldon Hearncommand is:
75949e11e3aSSheldon Hearn.\"
76049e11e3aSSheldon Hearn.\" XXX Use .Dl to work around broken handling of .Ic inside .Bd and .Ed .
76149e11e3aSSheldon Hearn.\"
76249e11e3aSSheldon Hearn.Dl Ic if Ar list
76349e11e3aSSheldon Hearn.Dl Ic then Ar list
76449e11e3aSSheldon Hearn.Dl [ Ic elif Ar list
76549e11e3aSSheldon Hearn.Dl Ic then Ar list ] ...
76649e11e3aSSheldon Hearn.Dl [ Ic else Ar list ]
76749e11e3aSSheldon Hearn.Dl Ic fi
768ab72124fSSteve Price.Pp
76949e11e3aSSheldon HearnThe syntax of the
77049e11e3aSSheldon Hearn.Ic while
77149e11e3aSSheldon Hearncommand is:
77249e11e3aSSheldon Hearn.Dl Ic while Ar list
77349e11e3aSSheldon Hearn.Dl Ic do Ar list
77449e11e3aSSheldon Hearn.Dl Ic done
775ab72124fSSteve Price.Pp
776ab0a2172SSteve PriceThe two lists are executed repeatedly while the exit status of the
77749e11e3aSSheldon Hearnfirst list is zero.
77849e11e3aSSheldon HearnThe
77949e11e3aSSheldon Hearn.Ic until
78049e11e3aSSheldon Hearncommand is similar, but has the word
78149e11e3aSSheldon Hearn.Ic until
78249e11e3aSSheldon Hearnin place of
78349e11e3aSSheldon Hearn.Ic while ,
78449e11e3aSSheldon Hearnwhich causes it to
7854b88c807SRodney W. Grimesrepeat until the exit status of the first list is zero.
786ab72124fSSteve Price.Pp
78749e11e3aSSheldon HearnThe syntax of the
78849e11e3aSSheldon Hearn.Ic for
78949e11e3aSSheldon Hearncommand is:
790a01459dfSStefan Farfeleder.Dl Ic for Ar variable Op Ic in Ar word ...
79149e11e3aSSheldon Hearn.Dl Ic do Ar list
79249e11e3aSSheldon Hearn.Dl Ic done
793ab72124fSSteve Price.Pp
794a01459dfSStefan FarfelederIf
795a01459dfSStefan Farfeleder.Ic in
7967b14d37fSRalf S. Engelschalland the following words are omitted,
797a01459dfSStefan Farfeleder.Ic in Li $@
798a01459dfSStefan Farfelederis used instead.
7994b88c807SRodney W. GrimesThe words are expanded, and then the list is executed
80049e11e3aSSheldon Hearnrepeatedly with the variable set to each word in turn.
80149e11e3aSSheldon HearnThe
80249e11e3aSSheldon Hearn.Ic do
8036b15476eSSheldon Hearnand
80449e11e3aSSheldon Hearn.Ic done
80549e11e3aSSheldon Hearncommands may be replaced with
80649e11e3aSSheldon Hearn.Dq Li {
80749e11e3aSSheldon Hearnand
80849e11e3aSSheldon Hearn.Dq Li } .
809ab72124fSSteve Price.Pp
81049e11e3aSSheldon HearnThe syntax of the
81149e11e3aSSheldon Hearn.Ic break
81249e11e3aSSheldon Hearnand
81349e11e3aSSheldon Hearn.Ic continue
81449e11e3aSSheldon Hearncommands is:
81549e11e3aSSheldon Hearn.Dl Ic break Op Ar num
81649e11e3aSSheldon Hearn.Dl Ic continue Op Ar num
817ab72124fSSteve Price.Pp
81849e11e3aSSheldon HearnThe
81949e11e3aSSheldon Hearn.Ic break
82049e11e3aSSheldon Hearncommand terminates the
82149e11e3aSSheldon Hearn.Ar num
82249e11e3aSSheldon Hearninnermost
82349e11e3aSSheldon Hearn.Ic for
82449e11e3aSSheldon Hearnor
82549e11e3aSSheldon Hearn.Ic while
82649e11e3aSSheldon Hearnloops.
82749e11e3aSSheldon HearnThe
82849e11e3aSSheldon Hearn.Ic continue
82949e11e3aSSheldon Hearncommand continues with the next iteration of the innermost loop.
8308eed22b1SJens SchweikhardtThese are implemented as built-in commands.
831ab72124fSSteve Price.Pp
83249e11e3aSSheldon HearnThe syntax of the
83349e11e3aSSheldon Hearn.Ic case
83449e11e3aSSheldon Hearncommand is
83549e11e3aSSheldon Hearn.Dl Ic case Ar word Ic in
83649e11e3aSSheldon Hearn.Dl pattern) list ;;
83749e11e3aSSheldon Hearn.Dl ...
83849e11e3aSSheldon Hearn.Dl Ic esac
839ab72124fSSteve Price.Pp
84049e11e3aSSheldon HearnThe pattern can actually be one or more patterns
84149e11e3aSSheldon Hearn(see
84249e11e3aSSheldon Hearn.Sx Shell Patterns
84349e11e3aSSheldon Hearndescribed later),
84449e11e3aSSheldon Hearnseparated by
84567135607SMartin Cracauer.Dq Li \&|
8466b15476eSSheldon Hearncharacters.
847ab72124fSSteve Price.Ss Grouping Commands Together
8484b88c807SRodney W. GrimesCommands may be grouped by writing either
849ab72124fSSteve Price.Bd -literal -offset indent
8504b88c807SRodney W. Grimes(list)
851ab72124fSSteve Price.Ed
852ab72124fSSteve Price.Pp
8534b88c807SRodney W. Grimesor
854ab72124fSSteve Price.Bd -literal -offset indent
8554b88c807SRodney W. Grimes{ list; }
856ab72124fSSteve Price.Ed
857ab72124fSSteve Price.Pp
85849e11e3aSSheldon HearnThe first form executes the commands in a subshell.
8598eed22b1SJens SchweikhardtNote that built-in commands thus executed do not affect the current shell.
86049e11e3aSSheldon HearnThe second form does not fork another shell,
86149e11e3aSSheldon Hearnso it is slightly more efficient.
86249e11e3aSSheldon HearnGrouping commands together this way allows the user to
863ab0a2172SSteve Priceredirect their output as though they were one program:
864ab72124fSSteve Price.Bd -literal -offset indent
865ee7dc416SSteve Price{ echo -n "hello"; echo " world"; } > greeting
866ab72124fSSteve Price.Ed
867ab72124fSSteve Price.Ss Functions
8684b88c807SRodney W. GrimesThe syntax of a function definition is
869ab72124fSSteve Price.Bd -literal -offset indent
8704b88c807SRodney W. Grimesname ( ) command
871ab72124fSSteve Price.Ed
872ab72124fSSteve Price.Pp
8734b88c807SRodney W. GrimesA function definition is an executable statement; when
8744b88c807SRodney W. Grimesexecuted it installs a function named name and returns an
875eccea571SRuslan Ermilovexit status of zero.
876eccea571SRuslan ErmilovThe command is normally a list
8776b15476eSSheldon Hearnenclosed between
87849e11e3aSSheldon Hearn.Dq Li {
8796b15476eSSheldon Hearnand
88049e11e3aSSheldon Hearn.Dq Li } .
881ab72124fSSteve Price.Pp
8824b88c807SRodney W. GrimesVariables may be declared to be local to a function by
88349e11e3aSSheldon Hearnusing the
88449e11e3aSSheldon Hearn.Ic local
88549e11e3aSSheldon Hearncommand.
88649e11e3aSSheldon HearnThis should appear as the first statement of a function,
88749e11e3aSSheldon Hearnand the syntax is:
88849e11e3aSSheldon Hearn.Bd -ragged -offset indent
88949e11e3aSSheldon Hearn.Ic local
89081e9cda2SRuslan Ermilov.Op Ar variable ...
89149e11e3aSSheldon Hearn.Op Ar -
892ab72124fSSteve Price.Ed
893ab72124fSSteve Price.Pp
89449e11e3aSSheldon HearnThe
89549e11e3aSSheldon Hearn.Ic local
8968eed22b1SJens Schweikhardtcommand is implemented as a built-in command.
897ab72124fSSteve Price.Pp
8984b88c807SRodney W. GrimesWhen a variable is made local, it inherits the initial
8994b88c807SRodney W. Grimesvalue and exported and readonly flags from the variable
9004b88c807SRodney W. Grimeswith the same name in the surrounding scope, if there is
901eccea571SRuslan Ermilovone.
902eccea571SRuslan ErmilovOtherwise, the variable is initially unset.
903eccea571SRuslan ErmilovThe shell
904e918fc8fSSheldon Hearnuses dynamic scoping, so that if the variable
905e918fc8fSSheldon Hearn.Em x
906e918fc8fSSheldon Hearnis made local to function
907e918fc8fSSheldon Hearn.Em f ,
908e918fc8fSSheldon Hearnwhich then calls function
909e918fc8fSSheldon Hearn.Em g ,
910e918fc8fSSheldon Hearnreferences to the variable
911e918fc8fSSheldon Hearn.Em x
912e918fc8fSSheldon Hearnmade inside
913e918fc8fSSheldon Hearn.Em g
914e918fc8fSSheldon Hearnwill refer to the variable
915e918fc8fSSheldon Hearn.Em x
916e918fc8fSSheldon Hearndeclared inside
917e918fc8fSSheldon Hearn.Em f ,
918e918fc8fSSheldon Hearnnot to the global variable named
919e918fc8fSSheldon Hearn.Em x .
920ab72124fSSteve Price.Pp
9216b4bbd8aSCeri DaviesThe only special parameter that can be made local is
92249e11e3aSSheldon Hearn.Dq Li - .
9236b15476eSSheldon HearnMaking
92449e11e3aSSheldon Hearn.Dq Li -
9256b15476eSSheldon Hearnlocal causes any shell options that are
9264b88c807SRodney W. Grimeschanged via the set command inside the function to be
9274b88c807SRodney W. Grimesrestored to their original values when the function
9284b88c807SRodney W. Grimesreturns.
929ab72124fSSteve Price.Pp
93049e11e3aSSheldon HearnThe syntax of the
93149e11e3aSSheldon Hearn.Ic return
93249e11e3aSSheldon Hearncommand is
93349e11e3aSSheldon Hearn.Bd -ragged -offset indent
93449e11e3aSSheldon Hearn.Ic return
93549e11e3aSSheldon Hearn.Op Ar exitstatus
936ab72124fSSteve Price.Ed
937ab72124fSSteve Price.Pp
9384ad8968aSBrian FeldmanIt terminates the current executional scope, returning from the previous
9394ad8968aSBrian Feldmannested function, sourced script, or shell instance, in that order.
94049e11e3aSSheldon HearnThe
94149e11e3aSSheldon Hearn.Ic return
9428eed22b1SJens Schweikhardtcommand is implemented as a built-in command.
943ab72124fSSteve Price.Ss Variables and Parameters
944eccea571SRuslan ErmilovThe shell maintains a set of parameters.
945eccea571SRuslan ErmilovA parameter
946eccea571SRuslan Ermilovdenoted by a name is called a variable.
947eccea571SRuslan ErmilovWhen starting up,
9484b88c807SRodney W. Grimesthe shell turns all the environment variables into shell
949eccea571SRuslan Ermilovvariables.
950eccea571SRuslan ErmilovNew variables can be set using the form
951ab72124fSSteve Price.Bd -literal -offset indent
9524b88c807SRodney W. Grimesname=value
953ab72124fSSteve Price.Ed
954ab72124fSSteve Price.Pp
9554b88c807SRodney W. GrimesVariables set by the user must have a name consisting solely
95649e11e3aSSheldon Hearnof alphabetics, numerics, and underscores.
95749e11e3aSSheldon HearnThe first letter of a variable name must not be numeric.
95849e11e3aSSheldon HearnA parameter can also be denoted by a number
9594b88c807SRodney W. Grimesor a special character as explained below.
960ab72124fSSteve Price.Ss Positional Parameters
96149e11e3aSSheldon HearnA positional parameter is a parameter denoted by a number greater than zero.
962ab72124fSSteve PriceThe shell sets these initially to the values of its command line
963eccea571SRuslan Ermilovarguments that follow the name of the shell script.
964eccea571SRuslan ErmilovThe
965c644db6aSSheldon Hearn.Ic set
9668eed22b1SJens Schweikhardtbuilt-in command can also be used to set or reset them.
967ab72124fSSteve Price.Ss Special Parameters
96843d6677bSAlfred PerlsteinA special parameter is a parameter denoted by a special one-character
96943d6677bSAlfred Perlsteinname.
97043d6677bSAlfred PerlsteinThe special parameters recognized by the
97143d6677bSAlfred Perlstein.Nm
97243d6677bSAlfred Perlsteinshell of
97343d6677bSAlfred Perlstein.Fx
97443d6677bSAlfred Perlsteinare shown in the following list, exactly as they would appear in input
97543d6677bSAlfred Perlsteintyped by the user or in the source of a shell script.
976ab72124fSSteve Price.Bl -hang
97743d6677bSAlfred Perlstein.It Li $*
978eccea571SRuslan ErmilovExpands to the positional parameters, starting from one.
979eccea571SRuslan ErmilovWhen
9804b88c807SRodney W. Grimesthe expansion occurs within a double-quoted string
9814b88c807SRodney W. Grimesit expands to a single field with the value of each parameter
98249e11e3aSSheldon Hearnseparated by the first character of the
98349e11e3aSSheldon Hearn.Ev IFS
98449e11e3aSSheldon Hearnvariable,
98549e11e3aSSheldon Hearnor by a
98649e11e3aSSheldon Hearn.Aq space
98749e11e3aSSheldon Hearnif
98849e11e3aSSheldon Hearn.Ev IFS
98949e11e3aSSheldon Hearnis unset.
99043d6677bSAlfred Perlstein.It Li $@
991eccea571SRuslan ErmilovExpands to the positional parameters, starting from one.
992eccea571SRuslan ErmilovWhen
9934b88c807SRodney W. Grimesthe expansion occurs within double-quotes, each positional
9944b88c807SRodney W. Grimesparameter expands as a separate argument.
9954b88c807SRodney W. GrimesIf there are no positional parameters, the
996e918fc8fSSheldon Hearnexpansion of
997e918fc8fSSheldon Hearn.Li @
998e918fc8fSSheldon Hearngenerates zero arguments, even when
999e918fc8fSSheldon Hearn.Li @
1000eccea571SRuslan Ermilovis double-quoted.
1001eccea571SRuslan ErmilovWhat this basically means, for example, is
10026b15476eSSheldon Hearnif $1 is
10036b15476eSSheldon Hearn.Dq abc
10046b15476eSSheldon Hearnand $2 is
10056b15476eSSheldon Hearn.Dq def ghi ,
10066b15476eSSheldon Hearnthen
1007e918fc8fSSheldon Hearn.Qq Li $@
10086b15476eSSheldon Hearnexpands to
10094b88c807SRodney W. Grimesthe two arguments:
1010ab72124fSSteve Price.Bd -literal -offset indent
10114b88c807SRodney W. Grimes"abc"   "def ghi"
1012ab72124fSSteve Price.Ed
101343d6677bSAlfred Perlstein.It Li $#
10144b88c807SRodney W. GrimesExpands to the number of positional parameters.
101543d6677bSAlfred Perlstein.It Li $\&?
10164b88c807SRodney W. GrimesExpands to the exit status of the most recent pipeline.
101743d6677bSAlfred Perlstein.It Li $-
1018ab72124fSSteve Price(hyphen) Expands to the current option flags (the single-letter
10194b88c807SRodney W. Grimesoption names concatenated into a string) as specified on
10208eed22b1SJens Schweikhardtinvocation, by the set built-in command, or implicitly
10214b88c807SRodney W. Grimesby the shell.
102243d6677bSAlfred Perlstein.It Li $$
1023eccea571SRuslan ErmilovExpands to the process ID of the invoked shell.
1024eccea571SRuslan ErmilovA subshell
10254b88c807SRodney W. Grimesretains the same value of $ as its parent.
102643d6677bSAlfred Perlstein.It Li $\&!
10274b88c807SRodney W. GrimesExpands to the process ID of the most recent background
1028eccea571SRuslan Ermilovcommand executed from the current shell.
1029eccea571SRuslan ErmilovFor a
10304b88c807SRodney W. Grimespipeline, the process ID is that of the last command in the
10314b88c807SRodney W. Grimespipeline.
103243d6677bSAlfred Perlstein.It Li $0
1033ab72124fSSteve Price(zero) Expands to the name of the shell or shell script.
1034ab72124fSSteve Price.El
1035ab72124fSSteve Price.Ss Word Expansions
10364b88c807SRodney W. GrimesThis clause describes the various expansions that are
1037eccea571SRuslan Ermilovperformed on words.
1038eccea571SRuslan ErmilovNot all expansions are performed on
10394b88c807SRodney W. Grimesevery word, as explained later.
1040ab72124fSSteve Price.Pp
10414b88c807SRodney W. GrimesTilde expansions, parameter expansions, command substitutions,
10424b88c807SRodney W. Grimesarithmetic expansions, and quote removals that occur within
1043eccea571SRuslan Ermilova single word expand to a single field.
1044eccea571SRuslan ErmilovIt is only field
10454b88c807SRodney W. Grimessplitting or pathname expansion that can create multiple
1046e6d3cf26SSheldon Hearnfields from a single word.
1047e6d3cf26SSheldon HearnThe single exception to this rule is
1048e918fc8fSSheldon Hearnthe expansion of the special parameter
1049e918fc8fSSheldon Hearn.Li @
1050e918fc8fSSheldon Hearnwithin double-quotes,
1051e6d3cf26SSheldon Hearnas was described above.
1052ab72124fSSteve Price.Pp
10534b88c807SRodney W. GrimesThe order of word expansion is:
1054ab72124fSSteve Price.Bl -enum
1055ab72124fSSteve Price.It
1056ab72124fSSteve PriceTilde Expansion, Parameter Expansion, Command Substitution,
10574b88c807SRodney W. GrimesArithmetic Expansion (these all occur at the same time).
1058ab72124fSSteve Price.It
105949e11e3aSSheldon HearnField Splitting is performed on fields generated by step (1)
106049e11e3aSSheldon Hearnunless the
106149e11e3aSSheldon Hearn.Ev IFS
106249e11e3aSSheldon Hearnvariable is null.
1063ab72124fSSteve Price.It
106449e11e3aSSheldon HearnPathname Expansion (unless the
106549e11e3aSSheldon Hearn.Fl f
106649e11e3aSSheldon Hearnoption is in effect).
1067ab72124fSSteve Price.It
1068ab72124fSSteve PriceQuote Removal.
1069ab72124fSSteve Price.El
1070ab72124fSSteve Price.Pp
107149e11e3aSSheldon HearnThe
107249e11e3aSSheldon Hearn.Dq Li $
107349e11e3aSSheldon Hearncharacter is used to introduce parameter expansion, command
10744b88c807SRodney W. Grimessubstitution, or arithmetic evaluation.
1075ab72124fSSteve Price.Ss Tilde Expansion (substituting a user's home directory)
107649e11e3aSSheldon HearnA word beginning with an unquoted tilde character
1077a762afe5SGiorgos Keramidas.Pq Ql ~
107849e11e3aSSheldon Hearnis
107949e11e3aSSheldon Hearnsubjected to tilde expansion.
108049e11e3aSSheldon HearnAll the characters up to a slash
1081a762afe5SGiorgos Keramidas.Pq Ql /
108249e11e3aSSheldon Hearnor the end of the word are treated as a username
1083eccea571SRuslan Ermilovand are replaced with the user's home directory.
1084eccea571SRuslan ErmilovIf the
10854b88c807SRodney W. Grimesusername is missing (as in ~/foobar), the tilde is replaced
10864b88c807SRodney W. Grimeswith the value of the HOME variable (the current user's
10874b88c807SRodney W. Grimeshome directory).
1088ab72124fSSteve Price.Ss Parameter Expansion
10894b88c807SRodney W. GrimesThe format for parameter expansion is as follows:
1090ab72124fSSteve Price.Bd -literal -offset indent
10914b88c807SRodney W. Grimes${expression}
1092ab72124fSSteve Price.Ed
1093ab72124fSSteve Price.Pp
109449e11e3aSSheldon Hearnwhere expression consists of all characters until the matching
109549e11e3aSSheldon Hearn.Dq Li } .
109649e11e3aSSheldon HearnAny
109749e11e3aSSheldon Hearn.Dq Li }
10984b88c807SRodney W. Grimesescaped by a backslash or within a quoted string, and characters in
10994b88c807SRodney W. Grimesembedded arithmetic expansions, command substitutions, and variable
110049e11e3aSSheldon Hearnexpansions, are not examined in determining the matching
110149e11e3aSSheldon Hearn.Dq Li } .
1102ab72124fSSteve Price.Pp
11034b88c807SRodney W. GrimesThe simplest form for parameter expansion is:
1104ab72124fSSteve Price.Bd -literal -offset indent
11054b88c807SRodney W. Grimes${parameter}
1106ab72124fSSteve Price.Ed
1107ab72124fSSteve Price.Pp
11084b88c807SRodney W. GrimesThe value, if any, of parameter is substituted.
1109ab72124fSSteve Price.Pp
11104b88c807SRodney W. GrimesThe parameter name or symbol can be enclosed in braces, which are
11114b88c807SRodney W. Grimesoptional except for positional parameters with more than one digit or
11124b88c807SRodney W. Grimeswhen parameter is followed by a character that could be interpreted as
11134b88c807SRodney W. Grimespart of the name.
1114ab72124fSSteve PriceIf a parameter expansion occurs inside double-quotes:
1115ab72124fSSteve Price.Bl -enum
1116ab72124fSSteve Price.It
1117ab72124fSSteve PricePathname expansion is not performed on the results of the
11184b88c807SRodney W. Grimesexpansion.
1119ab72124fSSteve Price.It
1120ab72124fSSteve PriceField splitting is not performed on the results of the
1121e918fc8fSSheldon Hearnexpansion, with the exception of the special parameter
1122e918fc8fSSheldon Hearn.Li @ .
1123ab72124fSSteve Price.El
1124ab72124fSSteve Price.Pp
11254b88c807SRodney W. GrimesIn addition, a parameter expansion can be modified by using one of the
11264b88c807SRodney W. Grimesfollowing formats.
112781e9cda2SRuslan Ermilov.Bl -tag -width indent
1128ab72124fSSteve Price.It Li ${parameter:-word}
1129eccea571SRuslan ErmilovUse Default Values.
1130eccea571SRuslan ErmilovIf parameter is unset or
11314b88c807SRodney W. Grimesnull, the expansion of word is
11324b88c807SRodney W. Grimessubstituted; otherwise, the value of
11334b88c807SRodney W. Grimesparameter is substituted.
1134ab72124fSSteve Price.It Li ${parameter:=word}
1135eccea571SRuslan ErmilovAssign Default Values.
1136eccea571SRuslan ErmilovIf parameter is unset
11374b88c807SRodney W. Grimesor null, the expansion of word is
1138eccea571SRuslan Ermilovassigned to parameter.
1139eccea571SRuslan ErmilovIn all cases, the
11404b88c807SRodney W. Grimesfinal value of parameter is
1141eccea571SRuslan Ermilovsubstituted.
1142eccea571SRuslan ErmilovOnly variables, not positional
11434b88c807SRodney W. Grimesparameters or special parameters, can be
11444b88c807SRodney W. Grimesassigned in this way.
1145ab72124fSSteve Price.It Li ${parameter:?[word]}
1146eccea571SRuslan ErmilovIndicate Error if Null or Unset.
1147eccea571SRuslan ErmilovIf
11484b88c807SRodney W. Grimesparameter is unset or null, the expansion of
11494b88c807SRodney W. Grimesword (or a message indicating it is unset if
11504b88c807SRodney W. Grimesword is omitted) is written to standard
11514b88c807SRodney W. Grimeserror and the shell exits with a nonzero
1152e6d3cf26SSheldon Hearnexit status.
1153e6d3cf26SSheldon HearnOtherwise, the value of
1154eccea571SRuslan Ermilovparameter is substituted.
1155eccea571SRuslan ErmilovAn
11564b88c807SRodney W. Grimesinteractive shell need not exit.
1157ab72124fSSteve Price.It Li ${parameter:+word}
1158eccea571SRuslan ErmilovUse Alternate Value.
1159eccea571SRuslan ErmilovIf parameter is unset
11604b88c807SRodney W. Grimesor null, null is substituted;
11614b88c807SRodney W. Grimesotherwise, the expansion of word is
11624b88c807SRodney W. Grimessubstituted.
11631413f7deSTony Finch.El
1164ab72124fSSteve Price.Pp
11654b88c807SRodney W. GrimesIn the parameter expansions shown previously, use of the colon in the
11664b88c807SRodney W. Grimesformat results in a test for a parameter that is unset or null; omission
11674b88c807SRodney W. Grimesof the colon results in a test for a parameter that is only unset.
11681413f7deSTony Finch.Bl -tag -width indent
1169ab72124fSSteve Price.It Li ${#parameter}
1170eccea571SRuslan ErmilovString Length.
1171eccea571SRuslan ErmilovThe length in characters of
11724b88c807SRodney W. Grimesthe value of parameter.
117371337c33SSheldon Hearn.El
1174ab72124fSSteve Price.Pp
11754b88c807SRodney W. GrimesThe following four varieties of parameter expansion provide for substring
117649e11e3aSSheldon Hearnprocessing.
117749e11e3aSSheldon HearnIn each case, pattern matching notation
117849e11e3aSSheldon Hearn(see
117949e11e3aSSheldon Hearn.Sx Shell Patterns ) ,
118049e11e3aSSheldon Hearnrather than regular expression notation,
118149e11e3aSSheldon Hearnis used to evaluate the patterns.
1182e918fc8fSSheldon HearnIf parameter is one of the special parameters
1183e918fc8fSSheldon Hearn.Li *
118449e11e3aSSheldon Hearnor
1185e918fc8fSSheldon Hearn.Li @ ,
118649e11e3aSSheldon Hearnthe result of the expansion is unspecified.
11874b88c807SRodney W. GrimesEnclosing the full parameter expansion string in double-quotes does not
11884b88c807SRodney W. Grimescause the following four varieties of pattern characters to be quoted,
11894b88c807SRodney W. Grimeswhereas quoting characters within the braces has this effect.
119081e9cda2SRuslan Ermilov.Bl -tag -width indent
1191ab72124fSSteve Price.It Li ${parameter%word}
1192eccea571SRuslan ErmilovRemove Smallest Suffix Pattern.
1193eccea571SRuslan ErmilovThe word
1194eccea571SRuslan Ermilovis expanded to produce a pattern.
1195eccea571SRuslan ErmilovThe
11964b88c807SRodney W. Grimesparameter expansion then results in
11974b88c807SRodney W. Grimesparameter, with the smallest portion of the
11984b88c807SRodney W. Grimessuffix matched by the pattern deleted.
1199ab72124fSSteve Price.It Li ${parameter%%word}
1200eccea571SRuslan ErmilovRemove Largest Suffix Pattern.
1201eccea571SRuslan ErmilovThe word
1202eccea571SRuslan Ermilovis expanded to produce a pattern.
1203eccea571SRuslan ErmilovThe
12044b88c807SRodney W. Grimesparameter expansion then results in
12054b88c807SRodney W. Grimesparameter, with the largest portion of the
12064b88c807SRodney W. Grimessuffix matched by the pattern deleted.
1207ab72124fSSteve Price.It Li ${parameter#word}
1208eccea571SRuslan ErmilovRemove Smallest Prefix Pattern.
1209eccea571SRuslan ErmilovThe word
1210eccea571SRuslan Ermilovis expanded to produce a pattern.
1211eccea571SRuslan ErmilovThe
12124b88c807SRodney W. Grimesparameter expansion then results in
12134b88c807SRodney W. Grimesparameter, with the smallest portion of the
12144b88c807SRodney W. Grimesprefix matched by the pattern deleted.
1215ab72124fSSteve Price.It Li ${parameter##word}
1216eccea571SRuslan ErmilovRemove Largest Prefix Pattern.
1217eccea571SRuslan ErmilovThe word
1218eccea571SRuslan Ermilovis expanded to produce a pattern.
1219eccea571SRuslan ErmilovThe
12204b88c807SRodney W. Grimesparameter expansion then results in
12214b88c807SRodney W. Grimesparameter, with the largest portion of the
12224b88c807SRodney W. Grimesprefix matched by the pattern deleted.
1223ab72124fSSteve Price.El
1224ab72124fSSteve Price.Ss Command Substitution
12254b88c807SRodney W. GrimesCommand substitution allows the output of a command to be substituted in
1226eccea571SRuslan Ermilovplace of the command name itself.
1227eccea571SRuslan ErmilovCommand substitution occurs when
12284b88c807SRodney W. Grimesthe command is enclosed as follows:
1229ab72124fSSteve Price.Bd -literal -offset indent
12304b88c807SRodney W. Grimes$(command)
1231ab72124fSSteve Price.Ed
1232ab72124fSSteve Price.Pp
123349e11e3aSSheldon Hearnor the backquoted version:
1234ab72124fSSteve Price.Bd -literal -offset indent
12354b88c807SRodney W. Grimes`command`
1236ab72124fSSteve Price.Ed
1237ab72124fSSteve Price.Pp
12384b88c807SRodney W. GrimesThe shell expands the command substitution by executing command in a
12394b88c807SRodney W. Grimessubshell environment and replacing the command substitution
124049e11e3aSSheldon Hearnwith the standard output of the command,
124149e11e3aSSheldon Hearnremoving sequences of one or more newlines at the end of the substitution.
124249e11e3aSSheldon HearnEmbedded newlines before the end of the output are not removed;
124349e11e3aSSheldon Hearnhowever, during field splitting, they may be translated into spaces
124449e11e3aSSheldon Hearndepending on the value of
124549e11e3aSSheldon Hearn.Ev IFS
124649e11e3aSSheldon Hearnand the quoting that is in effect.
1247ab72124fSSteve Price.Ss Arithmetic Expansion
12484b88c807SRodney W. GrimesArithmetic expansion provides a mechanism for evaluating an arithmetic
1249e6d3cf26SSheldon Hearnexpression and substituting its value.
1250e6d3cf26SSheldon HearnThe format for arithmetic expansion is as follows:
1251ab72124fSSteve Price.Bd -literal -offset indent
12524b88c807SRodney W. Grimes$((expression))
1253ab72124fSSteve Price.Ed
1254ab72124fSSteve Price.Pp
12554b88c807SRodney W. GrimesThe expression is treated as if it were in double-quotes, except
1256eccea571SRuslan Ermilovthat a double-quote inside the expression is not treated specially.
1257eccea571SRuslan ErmilovThe
12584b88c807SRodney W. Grimesshell expands all tokens in the expression for parameter expansion,
12594b88c807SRodney W. Grimescommand substitution, and quote removal.
1260ab72124fSSteve Price.Pp
12614b88c807SRodney W. GrimesNext, the shell treats this as an arithmetic expression and
12624b88c807SRodney W. Grimessubstitutes the value of the expression.
1263ab72124fSSteve Price.Ss White Space Splitting (Field Splitting)
12644b88c807SRodney W. GrimesAfter parameter expansion, command substitution, and
12654b88c807SRodney W. Grimesarithmetic expansion the shell scans the results of
12664b88c807SRodney W. Grimesexpansions and substitutions that did not occur in double-quotes for
12674b88c807SRodney W. Grimesfield splitting and multiple fields can result.
1268ab72124fSSteve Price.Pp
126949e11e3aSSheldon HearnThe shell treats each character of the
127049e11e3aSSheldon Hearn.Ev IFS
127149e11e3aSSheldon Hearnas a delimiter and uses
12724b88c807SRodney W. Grimesthe delimiters to split the results of parameter expansion and command
12734b88c807SRodney W. Grimessubstitution into fields.
1274ab72124fSSteve Price.Ss Pathname Expansion (File Name Generation)
127549e11e3aSSheldon HearnUnless the
127649e11e3aSSheldon Hearn.Fl f
127749e11e3aSSheldon Hearnoption is set,
127849e11e3aSSheldon Hearnfile name generation is performed
1279eccea571SRuslan Ermilovafter word splitting is complete.
1280eccea571SRuslan ErmilovEach word is
1281eccea571SRuslan Ermilovviewed as a series of patterns, separated by slashes.
1282eccea571SRuslan ErmilovThe
12834b88c807SRodney W. Grimesprocess of expansion replaces the word with the names of
12844b88c807SRodney W. Grimesall existing files whose names can be formed by replacing
12854b88c807SRodney W. Grimeseach pattern with a string that matches the specified pattern.
1286ab0a2172SSteve PriceThere are two restrictions on this: first, a pattern cannot match
1287ab0a2172SSteve Pricea string containing a slash, and second,
12884b88c807SRodney W. Grimesa pattern cannot match a string starting with a period
12894b88c807SRodney W. Grimesunless the first character of the pattern is a period.
12904b88c807SRodney W. GrimesThe next section describes the patterns used for both
1291ab72124fSSteve PricePathname Expansion and the
1292c644db6aSSheldon Hearn.Ic case
1293ab72124fSSteve Pricecommand.
1294ab72124fSSteve Price.Ss Shell Patterns
1295f434d1dfSAdam DavidA pattern consists of normal characters, which match themselves,
129649e11e3aSSheldon Hearnand meta-characters.
129749e11e3aSSheldon HearnThe meta-characters are
12981586940eSRuslan Ermilov.Dq Li \&! ,
129949e11e3aSSheldon Hearn.Dq Li * ,
13001586940eSRuslan Ermilov.Dq Li \&? ,
13016b15476eSSheldon Hearnand
130249e11e3aSSheldon Hearn.Dq Li [ .
13036b15476eSSheldon HearnThese characters lose their special meanings if they are quoted.
13046b15476eSSheldon HearnWhen command or variable substitution is performed and the dollar sign
13056b15476eSSheldon Hearnor back quotes are not double-quoted, the value of the
13064b88c807SRodney W. Grimesvariable or the output of the command is scanned for these
13074b88c807SRodney W. Grimescharacters and they are turned into meta-characters.
1308ab72124fSSteve Price.Pp
13096b15476eSSheldon HearnAn asterisk
1310a762afe5SGiorgos Keramidas.Pq Ql *
1311e918fc8fSSheldon Hearnmatches any string of characters.
1312e918fc8fSSheldon HearnA question mark
1313a762afe5SGiorgos Keramidas.Pq Ql \&?
1314e918fc8fSSheldon Hearnmatches any single character.
1315e6d3cf26SSheldon HearnA left bracket
1316a762afe5SGiorgos Keramidas.Pq Ql [
1317e6d3cf26SSheldon Hearnintroduces a character class.
1318e6d3cf26SSheldon HearnThe end of the character class is indicated by a
131949e11e3aSSheldon Hearn.Dq Li \&] ;
13206b15476eSSheldon Hearnif the
132149e11e3aSSheldon Hearn.Dq Li \&]
13226b15476eSSheldon Hearnis missing then the
132349e11e3aSSheldon Hearn.Dq Li [
13246b15476eSSheldon Hearnmatches a
132549e11e3aSSheldon Hearn.Dq Li [
1326e6d3cf26SSheldon Hearnrather than introducing a character class.
1327e6d3cf26SSheldon HearnA character class matches any of the characters between the square brackets.
1328e6d3cf26SSheldon HearnA range of characters may be specified using a minus sign.
1329e918fc8fSSheldon HearnThe character class may be complemented by making an exclamation point
1330a762afe5SGiorgos Keramidas.Pq Ql !\&
1331e918fc8fSSheldon Hearnthe first character of the character class.
1332ab72124fSSteve Price.Pp
13336b15476eSSheldon HearnTo include a
133412e720d7SRuslan Ermilov.Dq Li \&]
1335e6d3cf26SSheldon Hearnin a character class, make it the first character listed
1336e6d3cf26SSheldon Hearn(after the
13371586940eSRuslan Ermilov.Dq Li \&! ,
1338e6d3cf26SSheldon Hearnif any).
1339e918fc8fSSheldon HearnTo include a
1340e918fc8fSSheldon Hearn.Dq Li - ,
1341e918fc8fSSheldon Hearnmake it the first or last character listed.
13428eed22b1SJens Schweikhardt.Ss Built-in Commands
1343c644db6aSSheldon HearnThis section lists the commands which
13448eed22b1SJens Schweikhardtare built-in because they need to perform some operation
1345eccea571SRuslan Ermilovthat cannot be performed by a separate process.
1346eccea571SRuslan ErmilovIn addition to
13478eed22b1SJens Schweikhardtthese, a built-in version of the
1348d90c5c4aSAkinori MUSHA.Xr test 1
1349018d9f62SAkinori MUSHAcommand is provided for efficiency.
135081e9cda2SRuslan Ermilov.Bl -tag -width indent
1351d0353b83SRuslan Ermilov.It Ic \&:
1352aa9caaf6SPeter WemmA null command that returns a 0 (true) exit value.
1353d0353b83SRuslan Ermilov.It Ic \&. Ar file
1354aa9caaf6SPeter WemmThe commands in the specified file are read and executed by the shell.
13554ad8968aSBrian FeldmanThe
13564ad8968aSBrian Feldman.Ic return
13574ad8968aSBrian Feldmancommand may be used to return to the
13584ad8968aSBrian Feldman.Ic \&.
13594ad8968aSBrian Feldmancommand's caller.
13606466945aSJohn PolstraIf
13616466945aSJohn Polstra.Ar file
13626466945aSJohn Polstracontains any
136349e11e3aSSheldon Hearn.Dq /
1364eccea571SRuslan Ermilovcharacters, it is used as is.
1365eccea571SRuslan ErmilovOtherwise, the shell searches the
13666466945aSJohn Polstra.Ev PATH
1367eccea571SRuslan Ermilovfor the file.
1368eccea571SRuslan ErmilovIf it is not found in the
13696466945aSJohn Polstra.Ev PATH ,
13706466945aSJohn Polstrait is sought in the current working directory.
1371a886288eSJesus R. Camou.It Ic alias Oo Ar name Ns Oo = Ns Ar string Oc ... Oc
137249e11e3aSSheldon HearnIf
1373d0353b83SRuslan Ermilov.Ar name Ns = Ns Ar string
137449e11e3aSSheldon Hearnis specified, the shell defines the alias
137549e11e3aSSheldon Hearn.Ar name
13766b15476eSSheldon Hearnwith value
137749e11e3aSSheldon Hearn.Ar string .
13786b15476eSSheldon HearnIf just
137949e11e3aSSheldon Hearn.Ar name
13806b15476eSSheldon Hearnis specified, the value of the alias
138149e11e3aSSheldon Hearn.Ar name
13826b15476eSSheldon Hearnis printed.
138349e11e3aSSheldon HearnWith no arguments, the
138449e11e3aSSheldon Hearn.Ic alias
13858eed22b1SJens Schweikhardtbuilt-in command prints the names and values of all defined aliases
138649e11e3aSSheldon Hearn(see
138749e11e3aSSheldon Hearn.Ic unalias ) .
1388e5341cbbSTim J. RobbinsAlias values are written with appropriate quoting so that they are
13899ba31ca0SRuslan Ermilovsuitable for re-input to the shell.
1390a886288eSJesus R. CamouAlso see the
1391a886288eSJesus R. Camou.Sx Aliases
1392a886288eSJesus R. Camousubsection.
139349e11e3aSSheldon Hearn.It Ic bg Op Ar job ...
139449e11e3aSSheldon HearnContinue the specified jobs
139549e11e3aSSheldon Hearn(or the current job if no jobs are given)
139649e11e3aSSheldon Hearnin the background.
1397df9e587bSTim J. Robbins.It Ic builtin Ar cmd Op Ar arg ...
13988eed22b1SJens SchweikhardtExecute the specified built-in command,
139949e11e3aSSheldon Hearn.Ar cmd .
140049e11e3aSSheldon HearnThis is useful when the user wishes to override a shell function
14018eed22b1SJens Schweikhardtwith the same name as a built-in command.
1402088acf90STim J. Robbins.It Ic bind Oo Fl aeklrsv Oc Oo Ar key Oo Ar command Oc Oc
1403088acf90STim J. RobbinsList or alter key bindings for the line editor.
1404088acf90STim J. RobbinsThis command is documented in
1405088acf90STim J. Robbins.Xr editrc 5 .
1406d74e011fSRuslan Ermilov.It Ic cd Oo Fl L | P Oc Op Ar directory
140749e11e3aSSheldon HearnSwitch to the specified
140849e11e3aSSheldon Hearn.Ar directory ,
140949e11e3aSSheldon Hearnor to the directory specified in the
141049e11e3aSSheldon Hearn.Ev HOME
141149e11e3aSSheldon Hearnenvironment variable if no
141249e11e3aSSheldon Hearn.Ar directory
141349e11e3aSSheldon Hearnis specified.
141449e11e3aSSheldon HearnIf
141549e11e3aSSheldon Hearn.Ar directory
1416029c8ee4STim J. Robbinsdoes not begin with
14179ba31ca0SRuslan Ermilov.Pa / , \&. ,
141849e11e3aSSheldon Hearnor
1419029c8ee4STim J. Robbins.Pa .. ,
142049e11e3aSSheldon Hearnthen the directories listed in the
142149e11e3aSSheldon Hearn.Ev CDPATH
142249e11e3aSSheldon Hearnvariable will be
142349e11e3aSSheldon Hearnsearched for the specified
142449e11e3aSSheldon Hearn.Ar directory .
1425029c8ee4STim J. RobbinsIf
1426029c8ee4STim J. Robbins.Ev CDPATH
1427029c8ee4STim J. Robbinsis unset, the current directory is searched.
142849e11e3aSSheldon HearnThe format of
142949e11e3aSSheldon Hearn.Ar CDPATH
143049e11e3aSSheldon Hearnis the same as that of
143149e11e3aSSheldon Hearn.Ev PATH .
1432e6d3cf26SSheldon HearnIn an interactive shell,
143349e11e3aSSheldon Hearnthe
143449e11e3aSSheldon Hearn.Ic cd
143549e11e3aSSheldon Hearncommand will print out the name of the directory
1436e6d3cf26SSheldon Hearnthat it actually switched to
1437e6d3cf26SSheldon Hearnif this is different from the name that the user gave.
143849e11e3aSSheldon HearnThese may be different either because the
143949e11e3aSSheldon Hearn.Ev CDPATH
144049e11e3aSSheldon Hearnmechanism was used or because a symbolic link was crossed.
1441178897f1STim J. Robbins.Pp
1442178897f1STim J. RobbinsIf the
1443178897f1STim J. Robbins.Fl P
1444178897f1STim J. Robbinsoption is specified,
144581e9cda2SRuslan Ermilov.Pa ..
1446178897f1STim J. Robbinsis handled physically and symbolic links are resolved before
144781e9cda2SRuslan Ermilov.Pa ..
1448178897f1STim J. Robbinscomponents are processed.
1449178897f1STim J. RobbinsIf the
1450178897f1STim J. Robbins.Fl L
1451178897f1STim J. Robbinsoption is specified,
145281e9cda2SRuslan Ermilov.Pa ..
1453178897f1STim J. Robbinsis handled logically.
1454178897f1STim J. RobbinsThis is the default.
14559434a1c7SDima Dorfman.It Ic chdir
14569434a1c7SDima DorfmanA synonym for the
14579434a1c7SDima Dorfman.Ic cd
14588eed22b1SJens Schweikhardtbuilt-in command.
14599ba31ca0SRuslan Ermilov.It Ic command Oo Fl p Oc Op Ar utility Op Ar argument ...
14602babaf74STim J. RobbinsExecute the specified
14612babaf74STim J. Robbins.Ar utility
14622babaf74STim J. Robbinsas a simple command (see the
14632babaf74STim J. Robbins.Sx Simple Commands
14642babaf74STim J. Robbinssection).
14652babaf74STim J. Robbins.Pp
14662babaf74STim J. RobbinsIf the
14672babaf74STim J. Robbins.Fl p
14682babaf74STim J. Robbinsoption is specified, the command search is performed using a
14692babaf74STim J. Robbinsdefault value of
14702babaf74STim J. Robbins.Ev PATH
14712babaf74STim J. Robbinsthat is guaranteed to find all of the standard utilities.
14729ba31ca0SRuslan Ermilov.It Ic echo Oo Fl e | n Oc Op Ar string
1473501e74b7SMark OvensPrint
1474501e74b7SMark Ovens.Ar string
1475501e74b7SMark Ovensto the standard output with a newline appended.
147681e9cda2SRuslan Ermilov.Bl -tag -width indent
1477501e74b7SMark Ovens.It Fl n
1478501e74b7SMark OvensSuppress the output of the trailing newline.
1479501e74b7SMark Ovens.It Fl e
1480501e74b7SMark OvensProcess C-style backslash escape sequences.
1481501e74b7SMark Ovens.Ic echo
1482501e74b7SMark Ovensunderstands the following character escapes:
148381e9cda2SRuslan Ermilov.Bl -tag -width indent
1484501e74b7SMark Ovens.It \ea
1485501e74b7SMark OvensAlert (ring the terminal bell)
1486501e74b7SMark Ovens.It \eb
1487501e74b7SMark OvensBackspace
1488501e74b7SMark Ovens.It \ec
1489501e74b7SMark OvensSuppress the trailing newline (this has the side-effect of truncating the
1490501e74b7SMark Ovensline if it is not the last character)
1491501e74b7SMark Ovens.It \ee
1492501e74b7SMark OvensThe ESC character (ASCII 0x1b)
1493501e74b7SMark Ovens.It \ef
1494501e74b7SMark OvensFormfeed
1495501e74b7SMark Ovens.It \en
1496501e74b7SMark OvensNewline
1497501e74b7SMark Ovens.It \er
1498501e74b7SMark OvensCarriage return
1499501e74b7SMark Ovens.It \et
1500501e74b7SMark OvensHorizontal tab
1501501e74b7SMark Ovens.It \ev
1502501e74b7SMark OvensVertical tab
1503501e74b7SMark Ovens.It \e\e
1504501e74b7SMark OvensLiteral backslash
1505501e74b7SMark Ovens.It \e0nnn
1506501e74b7SMark Ovens(Zero) The character whose octal value is nnn
1507501e74b7SMark Ovens.El
1508501e74b7SMark Ovens.Pp
1509501e74b7SMark OvensIf
1510501e74b7SMark Ovens.Ar string
1511501e74b7SMark Ovensis not enclosed in quotes then the backslash itself must be escaped
1512eccea571SRuslan Ermilovwith a backslash to protect it from the shell.
1513eccea571SRuslan ErmilovFor example
1514501e74b7SMark Ovens.Bd -literal -offset indent
1515501e74b7SMark Ovens$ echo -e "a\evb"
1516501e74b7SMark Ovensa
1517501e74b7SMark Ovens b
1518501e74b7SMark Ovens$ echo -e a\e\evb
1519501e74b7SMark Ovensa
1520501e74b7SMark Ovens b
1521501e74b7SMark Ovens$ echo -e "a\e\eb"
1522501e74b7SMark Ovensa\eb
1523501e74b7SMark Ovens$ echo -e a\e\e\e\eb
1524501e74b7SMark Ovensa\eb
1525501e74b7SMark Ovens.Ed
1526501e74b7SMark Ovens.El
1527558175caSTim J. Robbins.Pp
1528558175caSTim J. RobbinsOnly one of the
1529558175caSTim J. Robbins.Fl e
1530558175caSTim J. Robbinsand
1531558175caSTim J. Robbins.Fl n
1532558175caSTim J. Robbinsoptions may be specified.
153349e11e3aSSheldon Hearn.It Ic eval Ar string ...
1534e6d3cf26SSheldon HearnConcatenate all the arguments with spaces.
1535e6d3cf26SSheldon HearnThen re-parse and execute the command.
153649e11e3aSSheldon Hearn.It Ic exec Op Ar command Op arg ...
153749e11e3aSSheldon HearnUnless
153849e11e3aSSheldon Hearn.Ar command
153949e11e3aSSheldon Hearnis omitted,
154049e11e3aSSheldon Hearnthe shell process is replaced with the specified program
15418eed22b1SJens Schweikhardt(which must be a real program, not a shell built-in command or function).
154249e11e3aSSheldon HearnAny redirections on the
154349e11e3aSSheldon Hearn.Ic exec
154449e11e3aSSheldon Hearncommand are marked as permanent,
154549e11e3aSSheldon Hearnso that they are not undone when the
154649e11e3aSSheldon Hearn.Ic exec
154749e11e3aSSheldon Hearncommand finishes.
154849e11e3aSSheldon Hearn.It Ic exit Op Ar exitstatus
154949e11e3aSSheldon HearnTerminate the shell process.
155049e11e3aSSheldon HearnIf
155149e11e3aSSheldon Hearn.Ar exitstatus
155249e11e3aSSheldon Hearnis given
155349e11e3aSSheldon Hearnit is used as the exit status of the shell;
155449e11e3aSSheldon Hearnotherwise the exit status of the preceding command is used.
15559ba31ca0SRuslan Ermilov.It Ic export Oo Fl p Oc Op Ar name ...
15564b88c807SRodney W. GrimesThe specified names are exported so that they will
15574b88c807SRodney W. Grimesappear in the environment of subsequent commands.
155849e11e3aSSheldon HearnThe only way to un-export a variable is to
155949e11e3aSSheldon Hearn.Ic unset
156049e11e3aSSheldon Hearnit.
156149e11e3aSSheldon HearnThe shell allows the value of a variable to be set
156249e11e3aSSheldon Hearnat the same time as it is exported by writing
1563ab72124fSSteve Price.Bd -literal -offset indent
15644b88c807SRodney W. Grimesexport name=value
1565ab72124fSSteve Price.Ed
1566ab72124fSSteve Price.Pp
15674b88c807SRodney W. GrimesWith no arguments the export command lists the names
15684b88c807SRodney W. Grimesof all exported variables.
156945086f8cSTim J. RobbinsIf the
157045086f8cSTim J. Robbins.Fl p
157145086f8cSTim J. Robbinsoption is specified, the exported variables are printed as
157245086f8cSTim J. Robbins.Dq Ic export Ar name Ns = Ns Ar value
157345086f8cSTim J. Robbinslines, suitable for re-input to the shell.
157481e9cda2SRuslan Ermilov.It Ic fc Oo Fl e Ar editor Oc Op Ar first Op Ar last
157581e9cda2SRuslan Ermilov.It Ic fc Fl l Oo Fl nr Oc Op Ar first Op Ar last
157681e9cda2SRuslan Ermilov.It Ic fc Fl s Oo Ar old Ns = Ns Ar new Oc Op Ar first
157749e11e3aSSheldon HearnThe
157849e11e3aSSheldon Hearn.Ic fc
15798eed22b1SJens Schweikhardtbuilt-in command lists, or edits and re-executes,
158049e11e3aSSheldon Hearncommands previously entered to an interactive shell.
158181e9cda2SRuslan Ermilov.Bl -tag -width indent
158249e11e3aSSheldon Hearn.It Fl e Ar editor
158349e11e3aSSheldon HearnUse the editor named by
158449e11e3aSSheldon Hearn.Ar editor
158549e11e3aSSheldon Hearnto edit the commands.
158649e11e3aSSheldon HearnThe editor string is a command name,
158749e11e3aSSheldon Hearnsubject to search via the
158849e11e3aSSheldon Hearn.Ev PATH
158949e11e3aSSheldon Hearnvariable.
159049e11e3aSSheldon HearnThe value in the
159149e11e3aSSheldon Hearn.Ev FCEDIT
159249e11e3aSSheldon Hearnvariable is used as a default when
159349e11e3aSSheldon Hearn.Fl e
159449e11e3aSSheldon Hearnis not specified.
159549e11e3aSSheldon HearnIf
159649e11e3aSSheldon Hearn.Ev FCEDIT
159749e11e3aSSheldon Hearnis null or unset, the value of the
159849e11e3aSSheldon Hearn.Ev EDITOR
159949e11e3aSSheldon Hearnvariable is used.
160049e11e3aSSheldon HearnIf
160149e11e3aSSheldon Hearn.Ev EDITOR
160249e11e3aSSheldon Hearnis null or unset,
1603ab72124fSSteve Price.Xr ed 1
1604ab72124fSSteve Priceis used as the editor.
160549e11e3aSSheldon Hearn.It Fl l No (ell)
16064b88c807SRodney W. GrimesList the commands rather than invoking
1607eccea571SRuslan Ermilovan editor on them.
1608eccea571SRuslan ErmilovThe commands are written in the
16094b88c807SRodney W. Grimessequence indicated by the first and last operands, as
161049e11e3aSSheldon Hearnaffected by
161149e11e3aSSheldon Hearn.Fl r ,
161249e11e3aSSheldon Hearnwith each command preceded by the command number.
161349e11e3aSSheldon Hearn.It Fl n
161449e11e3aSSheldon HearnSuppress command numbers when listing with
161549e11e3aSSheldon Hearn.Fl l .
161649e11e3aSSheldon Hearn.It Fl r
161749e11e3aSSheldon HearnReverse the order of the commands listed
161849e11e3aSSheldon Hearn(with
161949e11e3aSSheldon Hearn.Fl l )
162049e11e3aSSheldon Hearnor edited
162149e11e3aSSheldon Hearn(with neither
162249e11e3aSSheldon Hearn.Fl l
162349e11e3aSSheldon Hearnnor
162449e11e3aSSheldon Hearn.Fl s ) .
162549e11e3aSSheldon Hearn.It Fl s
16264b88c807SRodney W. GrimesRe-execute the command without invoking an editor.
162749e11e3aSSheldon Hearn.It Ar first
162849e11e3aSSheldon Hearn.It Ar last
162949e11e3aSSheldon HearnSelect the commands to list or edit.
163049e11e3aSSheldon HearnThe number of previous commands that can be accessed
163149e11e3aSSheldon Hearnare determined by the value of the
1632d0353b83SRuslan Ermilov.Ev HISTSIZE
1633d0353b83SRuslan Ermilovvariable.
163449e11e3aSSheldon HearnThe value of
163549e11e3aSSheldon Hearn.Ar first
163649e11e3aSSheldon Hearnor
163749e11e3aSSheldon Hearn.Ar last
163849e11e3aSSheldon Hearnor both are one of the following:
163981e9cda2SRuslan Ermilov.Bl -tag -width indent
164049e11e3aSSheldon Hearn.It Ar [+]num
164149e11e3aSSheldon HearnA positive number representing a command number;
164249e11e3aSSheldon Hearncommand numbers can be displayed with the
164349e11e3aSSheldon Hearn.Fl l
164449e11e3aSSheldon Hearnoption.
164549e11e3aSSheldon Hearn.It Ar -num
164649e11e3aSSheldon HearnA negative decimal number representing the
164749e11e3aSSheldon Hearncommand that was executed
164849e11e3aSSheldon Hearn.Ar num
164949e11e3aSSheldon Hearnof
165049e11e3aSSheldon Hearncommands previously.
165149e11e3aSSheldon HearnFor example, -1 is the immediately previous command.
165249e11e3aSSheldon Hearn.It Ar string
165349e11e3aSSheldon HearnA string indicating the most recently entered command
165449e11e3aSSheldon Hearnthat begins with that string.
165549e11e3aSSheldon HearnIf the
165649e11e3aSSheldon Hearn.Ar old=new
165749e11e3aSSheldon Hearnoperand is not also specified with
165849e11e3aSSheldon Hearn.Fl s ,
165949e11e3aSSheldon Hearnthe string form of the first operand cannot contain an embedded equal sign.
166049e11e3aSSheldon Hearn.El
166149e11e3aSSheldon Hearn.El
166249e11e3aSSheldon Hearn.Pp
166349e11e3aSSheldon HearnThe following environment variables affect the execution of
166449e11e3aSSheldon Hearn.Ic fc :
166538afdcbcSGiorgos Keramidas.Bl -tag -width ".Ev HISTSIZE"
166649e11e3aSSheldon Hearn.It Ev FCEDIT
166738afdcbcSGiorgos KeramidasName of the editor to use for history editing.
166849e11e3aSSheldon Hearn.It Ev HISTSIZE
16693d7b5b93SPhilippe CharnierThe number of previous commands that are accessible.
1670ab72124fSSteve Price.El
167149e11e3aSSheldon Hearn.It Ic fg Op Ar job
167249e11e3aSSheldon HearnMove the specified
167349e11e3aSSheldon Hearn.Ar job
167449e11e3aSSheldon Hearnor the current job to the foreground.
167549e11e3aSSheldon Hearn.It Ic getopts Ar optstring Ar var
167649e11e3aSSheldon HearnThe POSIX
167749e11e3aSSheldon Hearn.Ic getopts
167849e11e3aSSheldon Hearncommand.
167949e11e3aSSheldon HearnThe
168049e11e3aSSheldon Hearn.Ic getopts
168149e11e3aSSheldon Hearncommand deprecates the older
168249e11e3aSSheldon Hearn.Xr getopt 1
168349e11e3aSSheldon Hearncommand.
1684ab0a2172SSteve PriceThe first argument should be a series of letters, each possibly
1685ab0a2172SSteve Pricefollowed by a colon which indicates that the option takes an argument.
1686eccea571SRuslan ErmilovThe specified variable is set to the parsed option.
1687eccea571SRuslan ErmilovThe index of
168849e11e3aSSheldon Hearnthe next argument is placed into the shell variable
168949e11e3aSSheldon Hearn.Ev OPTIND .
1690ab0a2172SSteve PriceIf an option takes an argument, it is placed into the shell variable
169149e11e3aSSheldon Hearn.Ev OPTARG .
169249e11e3aSSheldon HearnIf an invalid option is encountered,
169349e11e3aSSheldon Hearn.Ev var
169449e11e3aSSheldon Hearnis set to
16951586940eSRuslan Ermilov.Dq Li \&? .
1696ab0a2172SSteve PriceIt returns a false value (1) when it encounters the end of the options.
169781e9cda2SRuslan Ermilov.It Ic hash Oo Fl rv Oc Op Ar command ...
169849e11e3aSSheldon HearnThe shell maintains a hash table which remembers the locations of commands.
169949e11e3aSSheldon HearnWith no arguments whatsoever, the
170049e11e3aSSheldon Hearn.Ic hash
170149e11e3aSSheldon Hearncommand prints out the contents of this table.
170249e11e3aSSheldon HearnEntries which have not been looked at since the last
170349e11e3aSSheldon Hearn.Ic cd
170449e11e3aSSheldon Hearncommand are marked with an asterisk;
170549e11e3aSSheldon Hearnit is possible for these entries to be invalid.
1706ab72124fSSteve Price.Pp
170749e11e3aSSheldon HearnWith arguments, the
170849e11e3aSSheldon Hearn.Ic hash
170949e11e3aSSheldon Hearncommand removes each specified
171049e11e3aSSheldon Hearn.Ar command
171149e11e3aSSheldon Hearnfrom the hash table (unless they are functions) and then locates it.
171249e11e3aSSheldon HearnWith the
171349e11e3aSSheldon Hearn.Fl v
171449e11e3aSSheldon Hearnoption,
171549e11e3aSSheldon Hearn.Ic hash
171649e11e3aSSheldon Hearnprints the locations of the commands as it finds them.
171749e11e3aSSheldon HearnThe
171849e11e3aSSheldon Hearn.Fl r
171949e11e3aSSheldon Hearnoption causes the
172049e11e3aSSheldon Hearn.Ic hash
172149e11e3aSSheldon Hearncommand to delete all the entries in the hash table except for functions.
172249e11e3aSSheldon Hearn.It Ic jobid Op Ar job
172349e11e3aSSheldon HearnPrint the process id's of the processes in the specified
172449e11e3aSSheldon Hearn.Ar job .
172549e11e3aSSheldon HearnIf the
172649e11e3aSSheldon Hearn.Ar job
172749e11e3aSSheldon Hearnargument is omitted, use the current job.
17289ba31ca0SRuslan Ermilov.It Ic jobs Oo Fl ls Oc Op Ar job ...
1729ad8a0759STim J. RobbinsPrint information about the specified jobs, or all jobs if no
1730ad8a0759STim J. Robbins.Ar job
1731ad8a0759STim J. Robbinsargument is given.
1732ad8a0759STim J. RobbinsThe information printed includes job ID, status and command name.
1733ad8a0759STim J. Robbins.Pp
1734ad8a0759STim J. RobbinsIf the
1735ad8a0759STim J. Robbins.Fl l
1736ad8a0759STim J. Robbinsoption is specified, the PID of each job is also printed.
1737ad8a0759STim J. RobbinsIf the
1738ad8a0759STim J. Robbins.Fl s
17399ba31ca0SRuslan Ermilovoption is specified, only the PIDs of the jobs are printed, one per line.
1740d74e011fSRuslan Ermilov.It Ic pwd Op Fl L | P
1741eccea571SRuslan ErmilovPrint the path of the current directory.
1742eccea571SRuslan ErmilovThe built-in command may
17434b88c807SRodney W. Grimesdiffer from the program of the same name because the
17448eed22b1SJens Schweikhardtbuilt-in command remembers what the current directory
1745eccea571SRuslan Ermilovis rather than recomputing it each time.
1746eccea571SRuslan ErmilovThis makes
1747eccea571SRuslan Ermilovit faster.
1748eccea571SRuslan ErmilovHowever, if the current directory is
174949e11e3aSSheldon Hearnrenamed,
17508eed22b1SJens Schweikhardtthe built-in version of
175149e11e3aSSheldon Hearn.Xr pwd 1
175249e11e3aSSheldon Hearnwill continue to print the old name for the directory.
1753178897f1STim J. Robbins.Pp
1754178897f1STim J. RobbinsIf the
1755178897f1STim J. Robbins.Fl P
1756178897f1STim J. Robbinsoption is specified, symbolic links are resolved.
1757178897f1STim J. RobbinsIf the
1758178897f1STim J. Robbins.Fl L
1759178897f1STim J. Robbinsoption is specified, the shell's notion of the current directory
1760178897f1STim J. Robbinsis printed (symbolic links are not resolved).
1761178897f1STim J. RobbinsThis is the default.
176281e9cda2SRuslan Ermilov.It Ic read Oo Fl p Ar prompt Oc Oo Fl t Ar timeout Oc Oo Fl er Oc Ar variable ...
176349e11e3aSSheldon HearnThe
176449e11e3aSSheldon Hearn.Ar prompt
176549e11e3aSSheldon Hearnis printed if the
176649e11e3aSSheldon Hearn.Fl p
176749e11e3aSSheldon Hearnoption is specified
1768eccea571SRuslan Ermilovand the standard input is a terminal.
1769eccea571SRuslan ErmilovThen a line is
1770eccea571SRuslan Ermilovread from the standard input.
1771eccea571SRuslan ErmilovThe trailing newline
17724b88c807SRodney W. Grimesis deleted from the line and the line is split as
177349e11e3aSSheldon Hearndescribed in the section on
177449e11e3aSSheldon Hearn.Sx White Space Splitting (Field Splitting)
177549e11e3aSSheldon Hearnabove, and
17764b88c807SRodney W. Grimesthe pieces are assigned to the variables in order.
1777f434d1dfSAdam DavidIf there are more pieces than variables, the remaining
177849e11e3aSSheldon Hearnpieces (along with the characters in
177949e11e3aSSheldon Hearn.Ev IFS
178049e11e3aSSheldon Hearnthat separated them)
178149e11e3aSSheldon Hearnare assigned to the last variable.
1782f434d1dfSAdam DavidIf there are more variables than pieces, the remaining
1783f434d1dfSAdam Davidvariables are assigned the null string.
1784ab72124fSSteve Price.Pp
178549e11e3aSSheldon HearnBackslashes are treated specially, unless the
178649e11e3aSSheldon Hearn.Fl r
178749e11e3aSSheldon Hearnoption is
1788eccea571SRuslan Ermilovspecified.
1789eccea571SRuslan ErmilovIf a backslash is followed by
17908f0561ccSThomas Gellekuma newline, the backslash and the newline will be
1791eccea571SRuslan Ermilovdeleted.
1792eccea571SRuslan ErmilovIf a backslash is followed by any other
17938f0561ccSThomas Gellekumcharacter, the backslash will be deleted and the following
179449e11e3aSSheldon Hearncharacter will be treated as though it were not in
179549e11e3aSSheldon Hearn.Ev IFS ,
179649e11e3aSSheldon Hearneven if it is.
17978f0561ccSThomas Gellekum.Pp
179849e11e3aSSheldon HearnIf the
179949e11e3aSSheldon Hearn.Fl t
180049e11e3aSSheldon Hearnoption is specified and the
180149e11e3aSSheldon Hearn.Ar timeout
180249e11e3aSSheldon Hearnelapses before any input is supplied,
180349e11e3aSSheldon Hearnthe
180449e11e3aSSheldon Hearn.Ic read
180549e11e3aSSheldon Hearncommand will return without assigning any values.
180649e11e3aSSheldon HearnThe
180749e11e3aSSheldon Hearn.Ar timeout
180849e11e3aSSheldon Hearnvalue may optionally be followed by one of
180949e11e3aSSheldon Hearn.Dq s ,
181049e11e3aSSheldon Hearn.Dq m
181149e11e3aSSheldon Hearnor
181249e11e3aSSheldon Hearn.Dq h
1813a910f192SDima Dorfmanto explicitly specify seconds, minutes or hours.
181449e11e3aSSheldon HearnIf none is supplied,
181549e11e3aSSheldon Hearn.Dq s
181649e11e3aSSheldon Hearnis assumed.
1817afa53c8dSMike Smith.Pp
181849e11e3aSSheldon HearnThe
181949e11e3aSSheldon Hearn.Fl e
182049e11e3aSSheldon Hearnoption exists only for backward compatibility with older scripts.
18219ba31ca0SRuslan Ermilov.It Ic readonly Oo Fl p Oc Op Ar name ...
182249e11e3aSSheldon HearnEach specified
182349e11e3aSSheldon Hearn.Ar name
182449e11e3aSSheldon Hearnis marked as read only,
182549e11e3aSSheldon Hearnso that it cannot be subsequently modified or unset.
182649e11e3aSSheldon HearnThe shell allows the value of a variable to be set
182749e11e3aSSheldon Hearnat the same time as it is marked read only
182849e11e3aSSheldon Hearnby using the following form:
1829ab72124fSSteve Price.Bd -literal -offset indent
18304b88c807SRodney W. Grimesreadonly name=value
1831ab72124fSSteve Price.Ed
1832ab72124fSSteve Price.Pp
183349e11e3aSSheldon HearnWith no arguments the
183449e11e3aSSheldon Hearn.Ic readonly
183549e11e3aSSheldon Hearncommand lists the names of all read only variables.
183645086f8cSTim J. RobbinsIf the
183745086f8cSTim J. Robbins.Fl p
183845086f8cSTim J. Robbinsoption is specified, the read-only variables are printed as
183945086f8cSTim J. Robbins.Dq Ic readonly Ar name Ns = Ns Ar value
184045086f8cSTim J. Robbinslines, suitable for re-input to the shell.
184181e9cda2SRuslan Ermilov.It Ic set Oo Fl /+abCEefIimnpTuVvx Oc Oo Fl /+o Ar longname Oc Oo
184281e9cda2SRuslan Ermilov.Fl c Ar string Oc Op Fl - Ar arg ...
1843e918fc8fSSheldon HearnThe
1844e918fc8fSSheldon Hearn.Ic set
1845e918fc8fSSheldon Hearncommand performs three different functions:
1846ab72124fSSteve Price.Bl -item
1847ab72124fSSteve Price.It
184849e11e3aSSheldon HearnWith no arguments, it lists the values of all shell variables.
1849ab72124fSSteve Price.It
185049e11e3aSSheldon HearnIf options are given,
185149e11e3aSSheldon Hearneither in short form or using the long
185249e11e3aSSheldon Hearn.Dq Fl /+o Ar longname
185349e11e3aSSheldon Hearnform,
185449e11e3aSSheldon Hearnit sets or clears the specified options as described in the section called
18556b15476eSSheldon Hearn.Sx Argument List Processing .
1856ab72124fSSteve Price.It
185749e11e3aSSheldon HearnIf the
185849e11e3aSSheldon Hearn.Dq Fl -
185949e11e3aSSheldon Hearnoption is specified,
186049e11e3aSSheldon Hearn.Ic set
186149e11e3aSSheldon Hearnwill replace the shell's positional parameters with the subsequent
186249e11e3aSSheldon Hearnarguments.
186349e11e3aSSheldon HearnIf no arguments follow the
186449e11e3aSSheldon Hearn.Dq Fl -
186549e11e3aSSheldon Hearnoption,
186649e11e3aSSheldon Hearnall the positional parameters will be cleared,
186749e11e3aSSheldon Hearnwhich is equivalent to executing the command
186849e11e3aSSheldon Hearn.Dq Li shift $# .
186949e11e3aSSheldon HearnThe
187049e11e3aSSheldon Hearn.Dq Fl -
18718eed22b1SJens Schweikhardtflag may be omitted when specifying arguments to be used
187249e11e3aSSheldon Hearnas positional replacement parameters.
187349e11e3aSSheldon HearnThis is not recommended,
187449e11e3aSSheldon Hearnbecause the first argument may begin with a dash
1875a762afe5SGiorgos Keramidas.Pq Ql -
187649e11e3aSSheldon Hearnor a plus
1877a762afe5SGiorgos Keramidas.Pq Ql + ,
187849e11e3aSSheldon Hearnwhich the
187949e11e3aSSheldon Hearn.Ic set
188049e11e3aSSheldon Hearncommand will interpret as a request to enable or disable options.
1881ab72124fSSteve Price.El
188249e11e3aSSheldon Hearn.It Ic setvar Ar variable Ar value
188349e11e3aSSheldon HearnAssigns the specified
188449e11e3aSSheldon Hearn.Ar value
188549e11e3aSSheldon Hearnto the specified
188649e11e3aSSheldon Hearn.Ar variable .
188749e11e3aSSheldon Hearn.Ic Setvar
188849e11e3aSSheldon Hearnis intended to be used in functions that
1889e6d3cf26SSheldon Hearnassign values to variables whose names are passed as parameters.
189049e11e3aSSheldon HearnIn general it is better to write
189149e11e3aSSheldon Hearn.Bd -literal -offset indent
189249e11e3aSSheldon Hearnvariable=value
189349e11e3aSSheldon Hearn.Ed
189449e11e3aSSheldon Hearnrather than using
189549e11e3aSSheldon Hearn.Ic setvar .
189649e11e3aSSheldon Hearn.It Ic shift Op Ar n
189749e11e3aSSheldon HearnShift the positional parameters
189849e11e3aSSheldon Hearn.Ar n
1899e918fc8fSSheldon Hearntimes, or once if
190049e11e3aSSheldon Hearn.Ar n
190149e11e3aSSheldon Hearnis not specified.
190249e11e3aSSheldon HearnA shift sets the value of $1 to the value of $2,
190349e11e3aSSheldon Hearnthe value of $2 to the value of $3, and so on,
190449e11e3aSSheldon Hearndecreasing the value of $# by one.
190549e11e3aSSheldon HearnIf there are zero positional parameters, shifting does not do anything.
190681e9cda2SRuslan Ermilov.It Ic trap Oo Ar action Oc Ar signal ...
190749e11e3aSSheldon HearnCause the shell to parse and execute
190849e11e3aSSheldon Hearn.Ar action
190949e11e3aSSheldon Hearnwhen any specified
191049e11e3aSSheldon Hearn.Ar signal
191149e11e3aSSheldon Hearnis received.
1912162ae3aeSTony FinchThe signals are specified by name or number.
1913162ae3aeSTony FinchIn addition, the pseudo-signal
1914f5d1157fSRuslan Ermilov.Cm EXIT
1915162ae3aeSTony Finchmay be used to specify an action that is performed when the shell terminates.
191649e11e3aSSheldon HearnThe
191749e11e3aSSheldon Hearn.Ar action
191849e11e3aSSheldon Hearnmay be null or omitted;
191949e11e3aSSheldon Hearnthe former causes the specified signal to be ignored
192049e11e3aSSheldon Hearnand the latter causes the default action to be taken.
192149e11e3aSSheldon HearnWhen the shell forks off a subshell,
192249e11e3aSSheldon Hearnit resets trapped (but not ignored) signals to the default action.
192349e11e3aSSheldon HearnThe
192449e11e3aSSheldon Hearn.Ic trap
192549e11e3aSSheldon Hearncommand has no effect on signals that were ignored on entry to the shell.
192649e11e3aSSheldon Hearn.It Ic type Op Ar name ...
192749e11e3aSSheldon HearnInterpret each
192849e11e3aSSheldon Hearn.Ar name
192949e11e3aSSheldon Hearnas a command and print the resolution of the command search.
1930e6d3cf26SSheldon HearnPossible resolutions are:
19318eed22b1SJens Schweikhardtshell keyword, alias, shell built-in command, command, tracked alias
193249e11e3aSSheldon Hearnand not found.
193349e11e3aSSheldon HearnFor aliases the alias expansion is printed;
193449e11e3aSSheldon Hearnfor commands and tracked aliases
193549e11e3aSSheldon Hearnthe complete pathname of the command is printed.
193662df9b62SSheldon Hearn.It Ic ulimit Oo Fl HSabcdflmnstuv Oc Op Ar limit
1937ab72124fSSteve PriceSet or display resource limits (see
1938ab72124fSSteve Price.Xr getrlimit 2 ) .
19396b15476eSSheldon HearnIf
194049e11e3aSSheldon Hearn.Ar limit
19416b15476eSSheldon Hearnis specified, the named resource will be set;
19427a2afe64SJoerg Wunschotherwise the current resource value will be displayed.
1943ab72124fSSteve Price.Pp
19446b15476eSSheldon HearnIf
194549e11e3aSSheldon Hearn.Fl H
194649e11e3aSSheldon Hearnis specified, the hard limits will be set or displayed.
194749e11e3aSSheldon HearnWhile everybody is allowed to reduce a hard limit,
194849e11e3aSSheldon Hearnonly the superuser can increase it.
194949e11e3aSSheldon HearnThe
195049e11e3aSSheldon Hearn.Fl S
195149e11e3aSSheldon Hearnoption
1952eccea571SRuslan Ermilovspecifies the soft limits instead.
1953eccea571SRuslan ErmilovWhen displaying limits,
19546b15476eSSheldon Hearnonly one of
195549e11e3aSSheldon Hearn.Fl S
19566b15476eSSheldon Hearnor
195749e11e3aSSheldon Hearn.Fl H
195849e11e3aSSheldon Hearncan be given.
195949e11e3aSSheldon HearnThe default is to display the soft limits,
196049e11e3aSSheldon Hearnand to set both the hard and the soft limits.
1961ab72124fSSteve Price.Pp
19626b15476eSSheldon HearnOption
196349e11e3aSSheldon Hearn.Fl a
196449e11e3aSSheldon Hearncauses the
196549e11e3aSSheldon Hearn.Ic ulimit
196649e11e3aSSheldon Hearncommand to display all resources.
196749e11e3aSSheldon HearnThe parameter
196849e11e3aSSheldon Hearn.Ar limit
19696b15476eSSheldon Hearnis not acceptable in this mode.
1970ab72124fSSteve Price.Pp
19717a2afe64SJoerg WunschThe remaining options specify which resource value is to be
197249e11e3aSSheldon Hearndisplayed or modified.
197349e11e3aSSheldon HearnThey are mutually exclusive.
197481e9cda2SRuslan Ermilov.Bl -tag -width indent
19753652a236SMartin Cracauer.It Fl b Ar sbsize
19763652a236SMartin CracauerThe maximum size of socket buffer usage, in bytes.
197749e11e3aSSheldon Hearn.It Fl c Ar coredumpsize
19787a2afe64SJoerg WunschThe maximal size of core dump files, in 512-byte blocks.
197949e11e3aSSheldon Hearn.It Fl d Ar datasize
19807a2afe64SJoerg WunschThe maximal size of the data segment of a process, in kilobytes.
198149e11e3aSSheldon Hearn.It Fl f Ar filesize
198249e11e3aSSheldon HearnThe maximal size of a file, in 512-byte blocks.
198349e11e3aSSheldon Hearn.It Fl l Ar lockedmem
19847a2afe64SJoerg WunschThe maximal size of memory that can be locked by a process, in
19857a2afe64SJoerg Wunschkilobytes.
198649e11e3aSSheldon Hearn.It Fl m Ar memoryuse
19877a2afe64SJoerg WunschThe maximal resident set size of a process, in kilobytes.
198849e11e3aSSheldon Hearn.It Fl n Ar nofiles
19897a2afe64SJoerg WunschThe maximal number of descriptors that could be opened by a process.
199049e11e3aSSheldon Hearn.It Fl s Ar stacksize
19917a2afe64SJoerg WunschThe maximal size of the stack segment, in kilobytes.
199249e11e3aSSheldon Hearn.It Fl t Ar time
19937a2afe64SJoerg WunschThe maximal amount of CPU time to be used by each process, in seconds.
199449e11e3aSSheldon Hearn.It Fl u Ar userproc
1995ab72124fSSteve PriceThe maximal number of simultaneous processes for this user ID.
199662df9b62SSheldon Hearn.It Fl v Ar virtualmem
19972d41ef4bSMatthew DillonThe maximal virtual size of a process, in kilobytes.
1998ab72124fSSteve Price.El
1999faa1ed35SStefan Farfeleder.It Ic umask Oo Fl S Oc Op Ar mask
200049e11e3aSSheldon HearnSet the file creation mask (see
2001ab72124fSSteve Price.Xr umask 2 )
2002faa1ed35SStefan Farfelederto the octal or symbolic (see
2003faa1ed35SStefan Farfeleder.Xr chmod 1 )
2004faa1ed35SStefan Farfeledervalue specified by
20055d3b843bSSheldon Hearn.Ar mask .
200649e11e3aSSheldon HearnIf the argument is omitted, the current mask value is printed.
2007faa1ed35SStefan FarfelederIf the
2008faa1ed35SStefan Farfeleder.Fl S
2009faa1ed35SStefan Farfelederoption is specified, the output is symbolic, otherwise the output is octal.
2010de4ad382SStefan Farfeleder.It Ic unalias Oo Fl a Oc Op Ar name ...
2011de4ad382SStefan FarfelederThe specified alias names are removed.
20126b15476eSSheldon HearnIf
20131b9735e6SSheldon Hearn.Fl a
20146b15476eSSheldon Hearnis specified, all aliases are removed.
20159ba31ca0SRuslan Ermilov.It Ic unset Oo Fl fv Oc Ar name ...
20168b34ad92STim J. RobbinsThe specified variables or functions are unset and unexported.
20178b34ad92STim J. RobbinsIf the
20188b34ad92STim J. Robbins.Fl v
20198b34ad92STim J. Robbinsoption is specified or no options are given, the
202049e11e3aSSheldon Hearn.Ar name
20218b34ad92STim J. Robbinsarguments are treated as variable names.
20228b34ad92STim J. RobbinsIf the
20238b34ad92STim J. Robbins.Fl f
20248b34ad92STim J. Robbinsoption is specified, the
20258b34ad92STim J. Robbins.Ar name
20268b34ad92STim J. Robbinsarguments are treated as function names.
202749e11e3aSSheldon Hearn.It Ic wait Op Ar job
202849e11e3aSSheldon HearnWait for the specified
202949e11e3aSSheldon Hearn.Ar job
203049e11e3aSSheldon Hearnto complete and return the exit status of the last process in the
203149e11e3aSSheldon Hearn.Ar job .
2032e6d3cf26SSheldon HearnIf the argument is omitted, wait for all jobs to complete
2033e6d3cf26SSheldon Hearnand return an exit status of zero.
2034ab72124fSSteve Price.El
2035ab72124fSSteve Price.Ss Commandline Editing
2036ab72124fSSteve PriceWhen
2037ab72124fSSteve Price.Nm
2038ab72124fSSteve Priceis being used interactively from a terminal, the current command
203949e11e3aSSheldon Hearnand the command history
204049e11e3aSSheldon Hearn(see
204149e11e3aSSheldon Hearn.Ic fc
204249e11e3aSSheldon Hearnin
20438eed22b1SJens Schweikhardt.Sx Built-in Commands )
204449e11e3aSSheldon Hearncan be edited using vi-mode command line editing.
204549e11e3aSSheldon HearnThis mode uses commands similar
20464b88c807SRodney W. Grimesto a subset of those described in the vi man page.
204749e11e3aSSheldon HearnThe command
204849e11e3aSSheldon Hearn.Dq Li set -o vi
204949e11e3aSSheldon Hearn(or
2050e918fc8fSSheldon Hearn.Dq Li set -V )
205149e11e3aSSheldon Hearnenables vi-mode editing and places
2052ab72124fSSteve Price.Nm
2053eccea571SRuslan Ermilovinto vi insert mode.
2054eccea571SRuslan ErmilovWith vi-mode enabled,
2055ab72124fSSteve Price.Nm
205649e11e3aSSheldon Hearncan be switched between insert mode and command mode by typing
205749e11e3aSSheldon Hearn.Aq ESC .
205849e11e3aSSheldon HearnHitting
205949e11e3aSSheldon Hearn.Aq return
206049e11e3aSSheldon Hearnwhile in command mode will pass the line to the shell.
2061ab72124fSSteve Price.Pp
206249e11e3aSSheldon HearnSimilarly, the
206349e11e3aSSheldon Hearn.Dq Li set -o emacs
206449e11e3aSSheldon Hearn(or
2065e918fc8fSSheldon Hearn.Dq Li set -E )
206649e11e3aSSheldon Hearncommand can be used to enable a subset of
2067ab72124fSSteve Priceemacs-style command line editing features.
206838afdcbcSGiorgos Keramidas.Sh ENVIRONMENT
206938afdcbcSGiorgos KeramidasThe following environment variables affect the execution of
207038afdcbcSGiorgos Keramidas.Nm :
207138afdcbcSGiorgos Keramidas.Bl -tag -width ".Ev HISTSIZE"
207238afdcbcSGiorgos Keramidas.It Ev CDPATH
207338afdcbcSGiorgos KeramidasThe search path used with the
207438afdcbcSGiorgos Keramidas.Ic cd
207538afdcbcSGiorgos Keramidasbuilt-in.
207638afdcbcSGiorgos Keramidas.It Ev EDITOR
207738afdcbcSGiorgos KeramidasThe fallback editor used with the
207838afdcbcSGiorgos Keramidas.Ic fc
207938afdcbcSGiorgos Keramidasbuilt-in.
208038afdcbcSGiorgos KeramidasIf not set, the default editor is
208138afdcbcSGiorgos Keramidas.Xr ed 1 .
208238afdcbcSGiorgos Keramidas.It Ev FCEDIT
208338afdcbcSGiorgos KeramidasThe default editor used with the
208438afdcbcSGiorgos Keramidas.Ic fc
208538afdcbcSGiorgos Keramidasbuilt-in.
208638afdcbcSGiorgos Keramidas.It Ev HISTSIZE
208738afdcbcSGiorgos KeramidasThe number of previous commands that are accessible.
208838afdcbcSGiorgos Keramidas.It Ev HOME
208938afdcbcSGiorgos KeramidasThe starting directory of
209038afdcbcSGiorgos Keramidas.Nm .
209138afdcbcSGiorgos Keramidas.It Ev IFS
209238afdcbcSGiorgos KeramidasInput Field Separators.
209338afdcbcSGiorgos KeramidasThis is normally set to
209438afdcbcSGiorgos Keramidas.Aq space ,
209538afdcbcSGiorgos Keramidas.Aq tab ,
209638afdcbcSGiorgos Keramidasand
209738afdcbcSGiorgos Keramidas.Aq newline .
209838afdcbcSGiorgos KeramidasSee the
209938afdcbcSGiorgos Keramidas.Sx White Space Splitting
210038afdcbcSGiorgos Keramidassection for more details.
210138afdcbcSGiorgos Keramidas.It Ev MAIL
210238afdcbcSGiorgos KeramidasThe name of a mail file, that will be checked for the arrival of new
210338afdcbcSGiorgos Keramidasmail.
210438afdcbcSGiorgos KeramidasOverridden by
210538afdcbcSGiorgos Keramidas.Ev MAILPATH .
210638afdcbcSGiorgos Keramidas.It Ev MAILPATH
210738afdcbcSGiorgos KeramidasA colon
210838afdcbcSGiorgos Keramidas.Pq Ql \&:
210938afdcbcSGiorgos Keramidasseparated list of file names, for the shell to check for incoming
211038afdcbcSGiorgos Keramidasmail.
211138afdcbcSGiorgos KeramidasThis environment setting overrides the
211238afdcbcSGiorgos Keramidas.Ev MAIL
211338afdcbcSGiorgos Keramidassetting.
211438afdcbcSGiorgos KeramidasThere is a maximum of 10 mailboxes that can be monitored at once.
211538afdcbcSGiorgos Keramidas.It Ev PATH
211638afdcbcSGiorgos KeramidasThe default search path for executables.
211738afdcbcSGiorgos KeramidasSee the
211838afdcbcSGiorgos Keramidas.Sx Path Search
211938afdcbcSGiorgos Keramidassection for details.
212038afdcbcSGiorgos Keramidas.It Ev PS1
212138afdcbcSGiorgos KeramidasThe primary prompt string, which defaults to
2122fb039b55SRuslan Ermilov.Dq Li "$ " ,
212338afdcbcSGiorgos Keramidasunless you are the superuser, in which case it defaults to
2124fb039b55SRuslan Ermilov.Dq Li "# " .
212538afdcbcSGiorgos Keramidas.It Ev PS2
212638afdcbcSGiorgos KeramidasThe secondary prompt string, which defaults to
2127fb039b55SRuslan Ermilov.Dq Li "> " .
212838afdcbcSGiorgos Keramidas.It Ev TERM
212938afdcbcSGiorgos KeramidasThe default terminal setting for the shell.
213038afdcbcSGiorgos KeramidasThis is inherited by children of the shell, and is used in the history
213138afdcbcSGiorgos Keramidasediting modes.
213238afdcbcSGiorgos Keramidas.El
2133fb039b55SRuslan Ermilov.Sh EXIT STATUS
2134fb039b55SRuslan ErmilovErrors that are detected by the shell, such as a syntax error, will
2135fb039b55SRuslan Ermilovcause the shell to exit with a non-zero exit status.
2136fb039b55SRuslan ErmilovIf the shell is not an interactive shell, the execution of the shell
2137fb039b55SRuslan Ermilovfile will be aborted.
2138fb039b55SRuslan ErmilovOtherwise the shell will return the exit status of the last command
2139fb039b55SRuslan Ermilovexecuted, or if the exit builtin is used with a numeric argument, it
2140fb039b55SRuslan Ermilovwill return the argument.
2141c83e7c50SJoseph Koshy.Sh SEE ALSO
2142c644db6aSSheldon Hearn.Xr builtin 1 ,
214338afdcbcSGiorgos Keramidas.Xr chsh 1 ,
2144c644db6aSSheldon Hearn.Xr echo 1 ,
214538afdcbcSGiorgos Keramidas.Xr ed 1 ,
214638afdcbcSGiorgos Keramidas.Xr emacs 1 ,
2147c83e7c50SJoseph Koshy.Xr expr 1 ,
214838afdcbcSGiorgos Keramidas.Xr getopt 1 ,
21495521ff5aSRuslan Ermilov.Xr pwd 1 ,
215038afdcbcSGiorgos Keramidas.Xr test 1 ,
215138afdcbcSGiorgos Keramidas.Xr vi 1 ,
215238afdcbcSGiorgos Keramidas.Xr execve 2 ,
215338afdcbcSGiorgos Keramidas.Xr getrlimit 2 ,
2154fd50df30SRuslan Ermilov.Xr umask 2 ,
215538afdcbcSGiorgos Keramidas.Xr editrc 5
2156ab72124fSSteve Price.Sh HISTORY
2157b8923d4cSWolfram SchneiderA
2158ab72124fSSteve Price.Nm
2159b8923d4cSWolfram Schneidercommand appeared in
2160fc482908STim J. Robbins.At v1 .
2161128dc4a2STim J. Robbins.Sh BUGS
2162128dc4a2STim J. RobbinsThe
2163128dc4a2STim J. Robbins.Nm
2164128dc4a2STim J. Robbinsutility does not recognize multibyte characters.
2165