1994-05-26 06:18:55 +00:00
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Kenneth Almquist.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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1997-04-28 03:20:09 +00:00
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.\" from: @(#)sh.1 8.6 (Berkeley) 5/4/95
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1999-03-31 21:02:01 +00:00
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.\" $Id: sh.1,v 1.23 1998/12/18 03:51:18 jkoshy Exp $
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1994-05-26 06:18:55 +00:00
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.\"
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1997-04-28 03:20:09 +00:00
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.Dd May 5, 1995
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.Dt SH 1
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.Os BSD 4
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.Sh NAME
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.Nm sh
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.Nd command interpreter (shell)
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.Sh SYNOPSIS
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.Nm
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.Op Fl /+abCEefIimnpsuVvx
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.Op Fl /+o Ar longname
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1997-09-13 17:40:00 +00:00
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.Op Fl c Ar string
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1997-04-28 03:20:09 +00:00
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.Op Ar arg ...
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.Sh DESCRIPTION
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1998-05-18 06:44:24 +00:00
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.Nm Sh
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1997-04-28 03:20:09 +00:00
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is the standard command interpreter for the system.
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The current version of
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.Nm
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|
is in the process of being changed to
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conform with the
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.St -p1003.2
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specification for the shell. This version has many features which make
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it appear
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1994-05-26 06:18:55 +00:00
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similar in some respects to the Korn shell, but it is not a Korn
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shell clone (run GNU's bash if you want that). Only features
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designated by POSIX, plus a few Berkeley extensions, are being
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1997-04-28 03:20:09 +00:00
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incorporated into this shell.
|
1994-05-26 06:18:55 +00:00
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This man page is not intended to be a tutorial or a complete
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|
specification of the shell.
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1997-04-28 03:20:09 +00:00
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.Ss Overview
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1994-05-26 06:18:55 +00:00
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|
The shell is a command that reads lines from
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either a file or the terminal, interprets them, and
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|
generally executes other commands. It is the program that is running
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|
when a user logs into the system (although a user can select
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|
a different shell with the chsh(1) command).
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|
The shell
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implements a language that has flow control constructs,
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a macro facility that provides a variety of features in
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addition to data storage, along with built in history and line
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editing capabilities. It incorporates many features to
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aid interactive use and has the advantage that the interpretative
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language is common to both interactive and non-interactive
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use (shell scripts). That is, commands can be typed directly
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to the running shell or can be put into a file and the file
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can be executed directly by the shell.
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1997-04-28 03:20:09 +00:00
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.Ss Invocation
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1994-05-26 06:18:55 +00:00
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If no args are present and if the standard input of the shell
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is connected to a terminal (or if the -i flag is set), the shell
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is considered an interactive shell. An interactive shell
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generally prompts before each command and handles programming
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and command errors differently (as described below).
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When first starting, the shell inspects argument 0, and
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if it begins with a dash '-', the shell is also considered
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a login shell. This is normally done automatically by the system
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1997-04-28 03:20:09 +00:00
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when the user first logs in. A login shell first reads commands
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from the files
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.Pa /etc/profile
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and
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.Pa .profile
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if they exist. If the environment variable
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.Ev ENV
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is set on entry to a shell, or is set in the
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.Pa .profile
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of a login shell, the shell next reads commands from the file named in
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.Ev ENV .
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Therefore, a user should place commands that are to be executed only
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at login time in the
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.Pa .profile
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file, and commands that are executed for every shell inside the
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.Ev ENV
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file. To set the
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.Ev ENV
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variable to some file, place the following line in your
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.Pa .profile
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of your home directory
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.sp
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.Dl ENV=$HOME/.shinit; export ENV
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.sp
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substituting for
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.Pa .shinit
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1997-05-07 11:42:00 +00:00
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any filename you wish.
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1997-04-28 03:20:09 +00:00
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If commandline arguments besides the options have been
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1994-05-26 06:18:55 +00:00
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specified, then the shell treats the first argument as the
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name of a file from which to read commands (a shell script), and
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the remaining arguments are set as the positional parameters
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of the shell ($1, $2, etc). Otherwise, the shell reads commands
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from its standard input.
|
1997-05-07 11:42:00 +00:00
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.Pp
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Unlike older versions of
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.Nm
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the
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.Ev ENV
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script is only sourced on invocation of interactive shells. This
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closes a well-known, and sometimes easily exploitable security
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|
hole related to poorly thought out
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.Ev ENV
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scripts.
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1997-04-28 03:20:09 +00:00
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.Ss Argument List Processing
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|
All of the single letter options to
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.Nm
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have a corresponding name that can be used as an argument to the
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.Xr set 1
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builtin (described later). These names are provided next to the
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single letter option in the descriptions below. Specifying a dash
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.Dq -
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enables the option, while using a plus
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.Dq +
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1998-07-30 04:47:56 +00:00
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disables the option. A
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.Dq --
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or plain
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.Dq -
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will stop option processing and will force the remaining
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words on the command line to be treated as arguments.
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1997-04-28 03:20:09 +00:00
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.Bl -tag -width Ds
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.It Fl a Li allexport
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1994-05-26 06:18:55 +00:00
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|
Export all variables assigned to.
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1997-04-28 03:20:09 +00:00
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.Pq UNIMPLEMENTED
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.It Fl b Li notify
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Enable asynchronous notification of background job
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completion.
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.Pq UNIMPLEMENTED
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.It Fl C Li noclobber
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Don't overwrite existing files with
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.Dq >.
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.Pq UNIMPLEMENTED
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.It Fl E Li emacs
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|
Enable the built-in
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.Xr emacs 1
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commandline editor (disables
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.Fl V
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if it has been set).
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.It Fl e Li errexit
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1994-05-26 06:18:55 +00:00
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If not interactive, exit immediately if any
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untested command fails.
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|
The exit status of a command is considered to be
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|
explicitly tested if the command is used to control
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|
an if, elif, while, or until; or if the command is the left
|
1997-04-28 03:20:09 +00:00
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hand operand of an
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.Dq &&
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or
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.Dq ||
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operator.
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.It Fl f Li noglob
|
1994-05-26 06:18:55 +00:00
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|
Disable pathname expansion.
|
1997-04-28 03:20:09 +00:00
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.It Fl I Li ignoreeof
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|
Ignore EOF's from input when interactive.
|
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.It Fl i Li interactive
|
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|
Force the shell to behave interactively.
|
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.It Fl m Li monitor
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|
Turn on job control (set automatically when interactive).
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.It Fl n Li noexec
|
1994-05-26 06:18:55 +00:00
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|
If not interactive, read commands but do not
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|
execute them. This is useful for checking the
|
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|
syntax of shell scripts.
|
1997-04-28 03:20:09 +00:00
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.It Fl p Li privileged
|
1996-10-29 03:12:51 +00:00
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|
Turn on privileged mode. This mode is enabled on startup
|
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|
if either the effective user or group id is not equal to the
|
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|
real user or group id. Turning this mode off sets the
|
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|
effective user and group ids to the real user and group ids.
|
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|
Also on interactive shells and when enabled, this mode sources
|
1997-04-28 03:20:09 +00:00
|
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|
.Pa /etc/suid_profile
|
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|
(instead of
|
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.Pa ~/.profile Ns )
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after
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.Pa /etc/profile
|
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|
and ignores the contents of the
|
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.Ev ENV
|
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variable.
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.It Fl s Li stdin
|
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|
Read commands from standard input (set automatically
|
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|
if no file arguments are present). This option has
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|
no effect when set after the shell has already started
|
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running (i.e. with
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.Xr set 1 Ns ).
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.It Fl u Li nounset
|
1994-05-26 06:18:55 +00:00
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|
Write a message to standard error when attempting
|
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|
to expand a variable that is not set, and if the
|
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|
shell is not interactive, exit immediately.
|
1997-04-28 03:20:09 +00:00
|
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|
.Pq UNIMPLEMENTED
|
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|
.It Fl V Li vi
|
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|
Enable the built-in
|
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|
.Xr vi 1
|
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|
commandline editor (disables
|
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|
.Fl E
|
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|
if it has been set).
|
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.It Fl v Li verbose
|
1994-05-26 06:18:55 +00:00
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|
The shell writes its input to standard error
|
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|
as it is read. Useful for debugging.
|
1997-04-28 03:20:09 +00:00
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|
.It Fl x Li xtrace
|
1994-05-26 06:18:55 +00:00
|
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|
Write each command to standard error (preceded
|
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|
by a '+ ') before it is executed. Useful for
|
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|
debugging.
|
1997-09-13 17:40:00 +00:00
|
|
|
.It Fl c Ar string
|
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|
Pass the string argument to the shell to be interpreted as input.
|
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|
Keep in mind that this option only accepts a single string as its
|
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|
argument, hence multi-word strings must be quoted.
|
1997-04-28 03:20:09 +00:00
|
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|
.El
|
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|
.Ss Lexical Structure
|
1994-05-26 06:18:55 +00:00
|
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|
The shell reads input in terms of lines from a file and breaks
|
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|
it up into words at whitespace (blanks and tabs), and at
|
|
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|
certain sequences of
|
|
|
|
characters that are special to the shell called ``operators''.
|
|
|
|
There are two types of operators: control operators and
|
|
|
|
redirection operators (their meaning is discussed later).
|
1997-04-28 03:20:09 +00:00
|
|
|
The following is a list of valid operators:
|
|
|
|
.Bl -tag -width Ds
|
|
|
|
.It No Control operators:
|
|
|
|
& && ( ) ; ;; | ||
|
|
|
|
.No \en
|
|
|
|
.It No Redirection operators:
|
1999-03-31 21:02:01 +00:00
|
|
|
< > >| << >> <& >& <<-
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
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|
.Ss Quoting
|
1994-05-26 06:18:55 +00:00
|
|
|
Quoting is used to remove the special meaning of certain characters
|
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|
or words to the shell, such as operators, whitespace, or
|
|
|
|
keywords. There are three types of quoting: matched single quotes,
|
|
|
|
matched double quotes, and backslash.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -tag -width Ds
|
|
|
|
.It Single Quotes
|
1994-05-26 06:18:55 +00:00
|
|
|
Enclosing characters in single quotes preserves the literal
|
1996-12-14 06:20:03 +00:00
|
|
|
meaning of all the characters (except single quotes, making
|
|
|
|
it impossible to put single-quotes in a single-quoted string).
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Double Quotes
|
1994-05-26 06:18:55 +00:00
|
|
|
Enclosing characters within double quotes preserves the literal
|
|
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|
meaning of all characters except dollarsign ($), backquote (`),
|
|
|
|
and backslash (\\). The backslash inside double quotes is
|
|
|
|
historically weird, and serves to quote only the following
|
1997-04-28 03:20:09 +00:00
|
|
|
characters: $ ` " \\
|
|
|
|
.No \en .
|
1994-05-26 06:18:55 +00:00
|
|
|
Otherwise it remains literal.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Backslash
|
|
|
|
A backslash preserves the literal meaning of the following
|
|
|
|
character, with the exception of
|
|
|
|
.No \en.
|
|
|
|
A backslash preceding a
|
|
|
|
.No \en
|
|
|
|
is treated as a line continuation.
|
|
|
|
.El
|
|
|
|
.Ss Reserved Words
|
1994-05-26 06:18:55 +00:00
|
|
|
Reserved words are words that have special meaning to the
|
|
|
|
shell and are recognized at the beginning of a line and
|
|
|
|
after a control operator. The following are reserved words:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
! { } case do
|
|
|
|
done elif else esac fi
|
|
|
|
for if then until while
|
|
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|
.Ed
|
|
|
|
.Ss Aliases
|
|
|
|
An alias is a name and corresponding value set using the
|
|
|
|
.Xr alias 1
|
1994-05-26 06:18:55 +00:00
|
|
|
builtin command. Whenever a reserved word may occur (see above),
|
|
|
|
and after checking for reserved words, the shell
|
|
|
|
checks the word to see if it matches an alias. If it does,
|
|
|
|
it replaces it in the input stream with its value. For example,
|
|
|
|
if there is an alias called ``lf'' with the value ``ls -F'',
|
|
|
|
then the input
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
lf foobar <return>
|
|
|
|
.Ed
|
|
|
|
.Pp
|
|
|
|
would become
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
ls -F foobar <return>
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Aliases provide a convenient way for naive users to
|
|
|
|
create shorthands for commands without having to learn how
|
|
|
|
to create functions with arguments. They can also be
|
|
|
|
used to create lexically obscure code. This use is discouraged.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Commands
|
1994-05-26 06:18:55 +00:00
|
|
|
The shell interprets the words it reads according to a
|
|
|
|
language, the specification of which is outside the scope
|
1997-04-28 03:20:09 +00:00
|
|
|
of this man page (refer to the BNF in the
|
|
|
|
.St -p1003.2
|
1994-05-26 06:18:55 +00:00
|
|
|
document). Essentially though, a line is read and if
|
|
|
|
the first word of the line (or after a control operator)
|
|
|
|
is not a reserved word, then the shell has recognized a
|
|
|
|
simple command. Otherwise, a complex command or some
|
|
|
|
other special construct may have been recognized.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Simple Commands
|
1994-05-26 06:18:55 +00:00
|
|
|
If a simple command has been recognized, the shell performs
|
|
|
|
the following actions:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -enum
|
|
|
|
.It
|
|
|
|
Leading words of the form ``name=value'' are
|
1994-05-26 06:18:55 +00:00
|
|
|
stripped off and assigned to the environment of
|
|
|
|
the simple command. Redirection operators and
|
|
|
|
their arguments (as described below) are stripped
|
|
|
|
off and saved for processing.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It
|
|
|
|
The remaining words are expanded as described in
|
1994-05-26 06:18:55 +00:00
|
|
|
the section called ``Expansions'', and the
|
|
|
|
first remaining word is considered the command
|
|
|
|
name and the command is located. The remaining
|
|
|
|
words are considered the arguments of the command.
|
|
|
|
If no command name resulted, then the ``name=value''
|
|
|
|
variable assignments recognized in 1) affect the
|
|
|
|
current shell.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It
|
|
|
|
Redirections are performed as described in
|
1994-05-26 06:18:55 +00:00
|
|
|
the next section.
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
|
|
.Ss Redirections
|
1994-05-26 06:18:55 +00:00
|
|
|
Redirections are used to change where a command reads its input
|
|
|
|
or sends its output. In general, redirections open, close, or
|
|
|
|
duplicate an existing reference to a file. The overall format
|
|
|
|
used for redirection is:
|
1997-04-28 03:20:09 +00:00
|
|
|
.sp
|
|
|
|
.Dl [n] redir-op file
|
|
|
|
.sp
|
1994-05-26 06:18:55 +00:00
|
|
|
where redir-op is one of the redirection operators mentioned
|
1997-04-28 03:20:09 +00:00
|
|
|
previously. The following gives some examples of how these
|
|
|
|
operators can be used. NOTE: stdin and stdout are commonly
|
|
|
|
used abbreviations for standard input and standard output,
|
|
|
|
respectively.
|
|
|
|
.Bl -tag -width "1234567890" -offset indent
|
|
|
|
.It [n]> file
|
|
|
|
redirect stdout (or n) to file
|
|
|
|
.It [n]>| file
|
|
|
|
same as above, but override the -C option
|
|
|
|
.It [n]>> file
|
|
|
|
append stdout (or n) to file
|
|
|
|
.It [n]< file
|
|
|
|
redirect stdin (or n) from file
|
|
|
|
.It [n1]<&n2
|
|
|
|
duplicate stdin (or n1) from file descriptor n2
|
|
|
|
.It [n]<&-
|
|
|
|
close stdin (or n)
|
|
|
|
.It [n1]>&n2
|
|
|
|
duplicate stdout (or n1) to n2.
|
|
|
|
.It [n]>&-
|
|
|
|
close stdout (or n)
|
|
|
|
.El
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The following redirection is often called a ``here-document''.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
[n]<< delimiter
|
|
|
|
here-doc-text...
|
|
|
|
delimiter
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
All the text on successive lines up to the delimiter is
|
|
|
|
saved away and made available to the command on standard
|
|
|
|
input, or file descriptor n if it is specified. If the delimiter
|
|
|
|
as specified on the initial line is quoted, then the here-doc-text
|
|
|
|
is treated literally, otherwise the text is subjected to
|
|
|
|
parameter expansion, command substitution, and arithmetic
|
1997-04-28 03:20:09 +00:00
|
|
|
expansion (as described in the section on ``Expansions''). If
|
1994-05-26 06:18:55 +00:00
|
|
|
the operator is ``<<-'' instead of ``<<'', then leading tabs
|
|
|
|
in the here-doc-text are stripped.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Search and Execution
|
1996-12-14 06:20:03 +00:00
|
|
|
There are three types of commands: shell functions,
|
|
|
|
builtin commands, and normal programs -- and the
|
1994-05-26 06:18:55 +00:00
|
|
|
command is searched for (by name) in that order. They
|
|
|
|
each are executed in a different way.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1996-12-14 06:20:03 +00:00
|
|
|
When a shell function is executed, all of the shell positional
|
|
|
|
parameters (except $0, which remains unchanged) are
|
1994-05-26 06:18:55 +00:00
|
|
|
set to the arguments of the shell function.
|
|
|
|
The variables which are explicitly placed in the environment of
|
|
|
|
the command (by placing assignments to them before the
|
|
|
|
function name) are made local to the function and are set
|
|
|
|
to the values given. Then the command given in the function
|
|
|
|
definition is executed. The positional parameters are
|
|
|
|
restored to their original values when the command completes.
|
1996-12-14 06:20:03 +00:00
|
|
|
This all occurs within the current shell.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1996-12-14 06:20:03 +00:00
|
|
|
Shell builtins are executed internally to the shell, without
|
|
|
|
spawning a new process.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Otherwise, if the command name doesn't match a function
|
|
|
|
or builtin, the command is searched for as a normal
|
|
|
|
program in the filesystem (as described in the next section).
|
|
|
|
When a normal program is executed, the shell runs the program,
|
|
|
|
passing the arguments and the environment to the
|
1996-12-14 06:20:03 +00:00
|
|
|
program. If the program is not a normal executable file
|
1997-04-28 03:20:09 +00:00
|
|
|
(i.e., if it does not begin with the "magic number" whose
|
|
|
|
.Tn ASCII
|
|
|
|
representation is "#!", so
|
|
|
|
.Fn execve
|
|
|
|
returns
|
|
|
|
.Er ENOEXEC
|
|
|
|
then) the shell
|
|
|
|
will interpret the program in a subshell. The child shell
|
|
|
|
will reinitialize itself in this case, so that the effect will
|
1996-12-14 06:20:03 +00:00
|
|
|
be as if a new shell had been invoked to handle the ad-hoc shell
|
|
|
|
script, except that the location of hashed commands located in
|
1994-05-26 06:18:55 +00:00
|
|
|
the parent shell will be remembered by the child.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1996-12-14 06:20:03 +00:00
|
|
|
Note that previous versions of this document
|
|
|
|
and the source code itself misleadingly and sporadically
|
|
|
|
refer to a shell script without a magic number
|
|
|
|
as a "shell procedure".
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Path Search
|
1994-05-26 06:18:55 +00:00
|
|
|
When locating a command, the shell first looks to see if
|
|
|
|
it has a shell function by that name. Then it looks for a
|
1996-12-14 06:20:03 +00:00
|
|
|
builtin command by that name. If a builtin command is not found,
|
|
|
|
one of two things happen:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -enum
|
|
|
|
.It
|
|
|
|
Command names containing a slash are simply executed without
|
1996-12-14 06:20:03 +00:00
|
|
|
performing any searches.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It
|
|
|
|
The shell searches each entry in
|
|
|
|
.Ev PATH
|
|
|
|
in turn for the command. The value of the
|
|
|
|
.Ev PATH
|
|
|
|
variable should be a series of
|
1994-05-26 06:18:55 +00:00
|
|
|
entries separated by colons. Each entry consists of a
|
|
|
|
directory name.
|
|
|
|
The current directory
|
1996-12-14 06:20:03 +00:00
|
|
|
may be indicated implicitly by an empty directory name,
|
|
|
|
or explicitly by a single period.
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
|
|
.Ss Command Exit Status
|
1994-05-26 06:18:55 +00:00
|
|
|
Each command has an exit status that can influence the behavior
|
|
|
|
of other shell commands. The paradigm is that a command exits
|
|
|
|
with zero for normal or success, and non-zero for failure,
|
|
|
|
error, or a false indication. The man page for each command
|
|
|
|
should indicate the various exit codes and what they mean.
|
|
|
|
Additionally, the builtin commands return exit codes, as does
|
1996-12-14 06:20:03 +00:00
|
|
|
an executed shell function.
|
1997-11-12 04:32:50 +00:00
|
|
|
.Pp
|
|
|
|
If a command is terminated by a signal, its exit status is 128 plus
|
|
|
|
the signal number. Signal numbers are defined in the header file
|
|
|
|
.Aq Pa sys/signal.h .
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Complex Commands
|
1994-05-26 06:18:55 +00:00
|
|
|
Complex commands are combinations of simple commands
|
|
|
|
with control operators or reserved words, together creating a larger complex
|
|
|
|
command. More generally, a command is one of the following:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -item -offset indent
|
|
|
|
.It
|
|
|
|
simple command
|
|
|
|
.It
|
|
|
|
pipeline
|
|
|
|
.It
|
|
|
|
list or compound-list
|
|
|
|
.It
|
|
|
|
compound command
|
|
|
|
.It
|
|
|
|
function definition
|
|
|
|
.El
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Unless otherwise stated, the exit status of a command is
|
|
|
|
that of the last simple command executed by the command.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Pipelines
|
1994-05-26 06:18:55 +00:00
|
|
|
A pipeline is a sequence of one or more commands separated
|
|
|
|
by the control operator |. The standard output of all but
|
|
|
|
the last command is connected to the standard input
|
1996-12-14 06:20:03 +00:00
|
|
|
of the next command. The standard output of the last
|
|
|
|
command is inherited from the shell, as usual.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The format for a pipeline is:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
1994-05-26 06:18:55 +00:00
|
|
|
[!] command1 [ | command2 ...]
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The standard output of command1 is connected to the standard
|
1997-04-28 03:20:09 +00:00
|
|
|
input of command2. The standard input, standard output, or
|
1994-05-26 06:18:55 +00:00
|
|
|
both of a command is considered to be assigned by the
|
|
|
|
pipeline before any redirection specified by redirection
|
|
|
|
operators that are part of the command.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
If the pipeline is not in the background (discussed later),
|
|
|
|
the shell waits for all commands to complete.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
If the reserved word ! does not precede the pipeline, the
|
|
|
|
exit status is the exit status of the last command specified
|
|
|
|
in the pipeline. Otherwise, the exit status is the logical
|
|
|
|
NOT of the exit status of the last command. That is, if
|
|
|
|
the last command returns zero, the exit status is 1; if
|
|
|
|
the last command returns greater than zero, the exit status
|
|
|
|
is zero.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Because pipeline assignment of standard input or standard
|
|
|
|
output or both takes place before redirection, it can be
|
|
|
|
modified by redirection. For example:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
1994-05-26 06:18:55 +00:00
|
|
|
$ command1 2>&1 | command2
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
sends both the standard output and standard error of command1
|
|
|
|
to the standard input of command2.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
A ; or <newline> terminator causes the preceding
|
|
|
|
AND-OR-list (described next) to be executed sequentially; a & causes
|
|
|
|
asynchronous execution of the preceding AND-OR-list.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1996-12-14 06:20:03 +00:00
|
|
|
Note that unlike some other shells, each process in the
|
|
|
|
pipeline is a child of the invoking shell (unless it
|
|
|
|
is a shell builtin, in which case it executes in the
|
|
|
|
current shell -- but any effect it has on the
|
|
|
|
environment is wiped).
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Background Commands -- &
|
1994-05-26 06:18:55 +00:00
|
|
|
If a command is terminated by the control operator ampersand
|
|
|
|
(&), the shell executes the command asynchronously -- that is,
|
|
|
|
the shell does not wait for
|
|
|
|
the command to finish before executing the next command.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The format for running a command in background is:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
1994-05-26 06:18:55 +00:00
|
|
|
command1 & [command2 & ...]
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
If the shell is not interactive, the standard input of an
|
|
|
|
asynchronous command is set to /dev/null.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Lists -- Generally Speaking
|
1994-05-26 06:18:55 +00:00
|
|
|
A list is a sequence of zero or more commands separated by
|
|
|
|
newlines, semicolons, or ampersands,
|
|
|
|
and optionally terminated by one of these three characters.
|
|
|
|
The commands in a
|
|
|
|
list are executed in the order they are written.
|
|
|
|
If command is followed by an ampersand, the shell starts the
|
|
|
|
command and immediately proceed onto the next command;
|
|
|
|
otherwise it waits for the command to terminate before
|
|
|
|
proceeding to the next one.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Short-Circuit List Operators
|
1994-05-26 06:18:55 +00:00
|
|
|
``&&'' and ``||'' are AND-OR list operators. ``&&'' executes
|
|
|
|
the first command, and then executes the second command
|
|
|
|
iff the exit status of the first command is zero. ``||''
|
|
|
|
is similar, but executes the second command iff the exit
|
|
|
|
status of the first command is nonzero. ``&&'' and ``||''
|
|
|
|
both have the same priority.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Flow-Control Constructs -- if, while, for, case
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of the if command is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
if list
|
|
|
|
then list
|
|
|
|
[ elif list
|
|
|
|
then list ] ...
|
|
|
|
[ else list ]
|
|
|
|
fi
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of the while command is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
while list
|
|
|
|
do list
|
|
|
|
done
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1996-12-14 06:20:03 +00:00
|
|
|
The two lists are executed repeatedly while the exit status of the
|
|
|
|
first list is zero. The until command is similar, but has the word
|
|
|
|
until in place of while, which causes it to
|
1994-05-26 06:18:55 +00:00
|
|
|
repeat until the exit status of the first list is zero.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of the for command is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
for variable in word...
|
|
|
|
do list
|
|
|
|
done
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The words are expanded, and then the list is executed
|
|
|
|
repeatedly with the variable set to each word in turn. do
|
|
|
|
and done may be replaced with ``{'' and ``}''.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of the break and continue command is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
break [ num ]
|
|
|
|
continue [ num ]
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Break terminates the num innermost for or while loops.
|
1996-12-14 06:20:03 +00:00
|
|
|
Continue continues with the next iteration of the innermost loop.
|
|
|
|
These are implemented as builtin commands.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of the case command is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
case word in
|
|
|
|
pattern) list ;;
|
|
|
|
...
|
|
|
|
esac
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The pattern can actually be one or more patterns (see Shell
|
|
|
|
Patterns described later), separated by ``|'' characters.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Grouping Commands Together
|
1994-05-26 06:18:55 +00:00
|
|
|
Commands may be grouped by writing either
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
(list)
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
or
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
{ list; }
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The first of these executes the commands in a subshell.
|
1996-12-14 06:20:03 +00:00
|
|
|
Builtin commands grouped into a (list) will not affect
|
|
|
|
the current shell.
|
|
|
|
The second form does not fork another shell so is
|
|
|
|
slightly more efficient.
|
|
|
|
Grouping commands together this way allows you to
|
|
|
|
redirect their output as though they were one program:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
1998-01-02 19:23:05 +00:00
|
|
|
{ echo -n "hello"; echo " world"; } > greeting
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ed
|
|
|
|
.Ss Functions
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of a function definition is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
name ( ) command
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
A function definition is an executable statement; when
|
|
|
|
executed it installs a function named name and returns an
|
1997-04-28 03:20:09 +00:00
|
|
|
exit status of zero. The command is normally a list
|
1994-05-26 06:18:55 +00:00
|
|
|
enclosed between ``{'' and ``}''.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Variables may be declared to be local to a function by
|
|
|
|
using a local command. This should appear as the first
|
|
|
|
statement of a function, and the syntax is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
local [ variable | - ] ...
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Local is implemented as a builtin command.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
When a variable is made local, it inherits the initial
|
|
|
|
value and exported and readonly flags from the variable
|
|
|
|
with the same name in the surrounding scope, if there is
|
1997-04-28 03:20:09 +00:00
|
|
|
one. Otherwise, the variable is initially unset. The shell
|
1994-05-26 06:18:55 +00:00
|
|
|
uses dynamic scoping, so that if you make the variable x
|
1995-05-05 16:49:15 +00:00
|
|
|
local to function f, which then calls function g, references
|
|
|
|
to the variable x made inside g will refer to the
|
1994-05-26 06:18:55 +00:00
|
|
|
variable x declared inside f, not to the global variable
|
|
|
|
named x.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The only special parameter than can be made local is
|
|
|
|
``-''. Making ``-'' local any shell options that are
|
|
|
|
changed via the set command inside the function to be
|
|
|
|
restored to their original values when the function
|
|
|
|
returns.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The syntax of the return command is
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
return [ exitstatus ]
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
It terminates the currently executing function. Return is
|
|
|
|
implemented as a builtin command.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Variables and Parameters
|
1994-05-26 06:18:55 +00:00
|
|
|
The shell maintains a set of parameters. A parameter
|
1997-04-28 03:20:09 +00:00
|
|
|
denoted by a name is called a variable. When starting up,
|
1994-05-26 06:18:55 +00:00
|
|
|
the shell turns all the environment variables into shell
|
|
|
|
variables. New variables can be set using the form
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
name=value
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Variables set by the user must have a name consisting solely
|
|
|
|
of alphabetics, numerics, and underscores - the first of which
|
|
|
|
must not be numeric. A parameter can also be denoted by a number
|
|
|
|
or a special character as explained below.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Positional Parameters
|
1994-05-26 06:18:55 +00:00
|
|
|
A positional parameter is a parameter denoted by a number (n > 0).
|
1997-04-28 03:20:09 +00:00
|
|
|
The shell sets these initially to the values of its commandline
|
|
|
|
arguments that follow the name of the shell script. The
|
|
|
|
.Xr set 1
|
|
|
|
builtin can also be used to set or reset them.
|
|
|
|
.Ss Special Parameters
|
1994-05-26 06:18:55 +00:00
|
|
|
A special parameter is a parameter denoted by one of the following
|
|
|
|
special characters. The value of the parameter is listed
|
|
|
|
next to its character.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -hang
|
|
|
|
.It *
|
1994-05-26 06:18:55 +00:00
|
|
|
Expands to the positional parameters, starting from one. When
|
|
|
|
the expansion occurs within a double-quoted string
|
|
|
|
it expands to a single field with the value of each parameter
|
|
|
|
separated by the first character of the IFS variable, or by a
|
|
|
|
<space> if IFS is unset.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It @
|
1994-05-26 06:18:55 +00:00
|
|
|
Expands to the positional parameters, starting from one. When
|
|
|
|
the expansion occurs within double-quotes, each positional
|
|
|
|
parameter expands as a separate argument.
|
|
|
|
If there are no positional parameters, the
|
|
|
|
expansion of @ generates zero arguments, even when @ is
|
|
|
|
double-quoted. What this basically means, for example, is
|
|
|
|
if $1 is ``abc'' and $2 is ``def ghi'', then "$@" expands to
|
|
|
|
the two arguments:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
1994-05-26 06:18:55 +00:00
|
|
|
"abc" "def ghi"
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ed
|
|
|
|
.It #
|
1994-05-26 06:18:55 +00:00
|
|
|
Expands to the number of positional parameters.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It ?
|
1994-05-26 06:18:55 +00:00
|
|
|
Expands to the exit status of the most recent pipeline.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It -
|
|
|
|
(hyphen) Expands to the current option flags (the single-letter
|
1994-05-26 06:18:55 +00:00
|
|
|
option names concatenated into a string) as specified on
|
|
|
|
invocation, by the set builtin command, or implicitly
|
|
|
|
by the shell.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It $
|
1994-05-26 06:18:55 +00:00
|
|
|
Expands to the process ID of the invoked shell. A subshell
|
|
|
|
retains the same value of $ as its parent.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It !
|
1994-05-26 06:18:55 +00:00
|
|
|
Expands to the process ID of the most recent background
|
|
|
|
command executed from the current shell. For a
|
|
|
|
pipeline, the process ID is that of the last command in the
|
|
|
|
pipeline.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It 0
|
|
|
|
(zero) Expands to the name of the shell or shell script.
|
|
|
|
.El
|
|
|
|
.Ss Word Expansions
|
1994-05-26 06:18:55 +00:00
|
|
|
This clause describes the various expansions that are
|
|
|
|
performed on words. Not all expansions are performed on
|
|
|
|
every word, as explained later.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Tilde expansions, parameter expansions, command substitutions,
|
|
|
|
arithmetic expansions, and quote removals that occur within
|
|
|
|
a single word expand to a single field. It is only field
|
|
|
|
splitting or pathname expansion that can create multiple
|
|
|
|
fields from a single word. The single exception to this
|
|
|
|
rule is the expansion of the special parameter @ within
|
|
|
|
double-quotes, as was described above.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The order of word expansion is:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -enum
|
|
|
|
.It
|
|
|
|
Tilde Expansion, Parameter Expansion, Command Substitution,
|
1994-05-26 06:18:55 +00:00
|
|
|
Arithmetic Expansion (these all occur at the same time).
|
1997-04-28 03:20:09 +00:00
|
|
|
.It
|
|
|
|
Field Splitting is performed on fields
|
1994-05-26 06:18:55 +00:00
|
|
|
generated by step (1) unless the IFS variable is null.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It
|
|
|
|
Pathname Expansion (unless set -f is in effect).
|
|
|
|
.It
|
|
|
|
Quote Removal.
|
|
|
|
.El
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The $ character is used to introduce parameter expansion, command
|
|
|
|
substitution, or arithmetic evaluation.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Tilde Expansion (substituting a user's home directory)
|
1994-05-26 06:18:55 +00:00
|
|
|
A word beginning with an unquoted tilde character (~) is
|
|
|
|
subjected to tilde expansion. All the characters up to
|
|
|
|
a slash (/) or the end of the word are treated as a username
|
|
|
|
and are replaced with the user's home directory. If the
|
|
|
|
username is missing (as in ~/foobar), the tilde is replaced
|
|
|
|
with the value of the HOME variable (the current user's
|
|
|
|
home directory).
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Parameter Expansion
|
1994-05-26 06:18:55 +00:00
|
|
|
The format for parameter expansion is as follows:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
${expression}
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
where expression consists of all characters until the matching }. Any }
|
|
|
|
escaped by a backslash or within a quoted string, and characters in
|
|
|
|
embedded arithmetic expansions, command substitutions, and variable
|
|
|
|
expansions, are not examined in determining the matching }.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The simplest form for parameter expansion is:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
${parameter}
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The value, if any, of parameter is substituted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The parameter name or symbol can be enclosed in braces, which are
|
|
|
|
optional except for positional parameters with more than one digit or
|
|
|
|
when parameter is followed by a character that could be interpreted as
|
|
|
|
part of the name.
|
1997-04-28 03:20:09 +00:00
|
|
|
If a parameter expansion occurs inside double-quotes:
|
|
|
|
.Bl -enum
|
|
|
|
.It
|
|
|
|
Pathname expansion is not performed on the results of the
|
1994-05-26 06:18:55 +00:00
|
|
|
expansion.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It
|
|
|
|
Field splitting is not performed on the results of the
|
1994-05-26 06:18:55 +00:00
|
|
|
expansion, with the exception of @.
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
In addition, a parameter expansion can be modified by using one of the
|
|
|
|
following formats.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -tag -width Ds
|
|
|
|
.It Li ${parameter:-word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Use Default Values. If parameter is unset or
|
|
|
|
null, the expansion of word is
|
|
|
|
substituted; otherwise, the value of
|
|
|
|
parameter is substituted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter:=word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Assign Default Values. If parameter is unset
|
|
|
|
or null, the expansion of word is
|
|
|
|
assigned to parameter. In all cases, the
|
|
|
|
final value of parameter is
|
|
|
|
substituted. Only variables, not positional
|
|
|
|
parameters or special parameters, can be
|
|
|
|
assigned in this way.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter:?[word]}
|
1994-05-26 06:18:55 +00:00
|
|
|
Indicate Error if Null or Unset. If
|
|
|
|
parameter is unset or null, the expansion of
|
|
|
|
word (or a message indicating it is unset if
|
|
|
|
word is omitted) is written to standard
|
|
|
|
error and the shell exits with a nonzero
|
1997-04-28 03:20:09 +00:00
|
|
|
exit status. Otherwise, the value of
|
1994-05-26 06:18:55 +00:00
|
|
|
parameter is substituted. An
|
|
|
|
interactive shell need not exit.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter:+word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Use Alternate Value. If parameter is unset
|
|
|
|
or null, null is substituted;
|
|
|
|
otherwise, the expansion of word is
|
|
|
|
substituted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
In the parameter expansions shown previously, use of the colon in the
|
|
|
|
format results in a test for a parameter that is unset or null; omission
|
|
|
|
of the colon results in a test for a parameter that is only unset.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${#parameter}
|
1994-05-26 06:18:55 +00:00
|
|
|
String Length. The length in characters of
|
|
|
|
the value of parameter.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The following four varieties of parameter expansion provide for substring
|
1996-12-14 06:20:03 +00:00
|
|
|
processing. In each case, pattern matching notation (see Shell Patterns),
|
|
|
|
rather
|
1994-05-26 06:18:55 +00:00
|
|
|
than regular expression notation, is used to evaluate the patterns.
|
|
|
|
If parameter is * or @, the result of the expansion is unspecified.
|
|
|
|
Enclosing the full parameter expansion string in double-quotes does not
|
|
|
|
cause the following four varieties of pattern characters to be quoted,
|
|
|
|
whereas quoting characters within the braces has this effect.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter%word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Remove Smallest Suffix Pattern. The word
|
|
|
|
is expanded to produce a pattern. The
|
|
|
|
parameter expansion then results in
|
|
|
|
parameter, with the smallest portion of the
|
|
|
|
suffix matched by the pattern deleted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter%%word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Remove Largest Suffix Pattern. The word
|
|
|
|
is expanded to produce a pattern. The
|
|
|
|
parameter expansion then results in
|
|
|
|
parameter, with the largest portion of the
|
|
|
|
suffix matched by the pattern deleted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter#word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Remove Smallest Prefix Pattern. The word
|
|
|
|
is expanded to produce a pattern. The
|
|
|
|
parameter expansion then results in
|
|
|
|
parameter, with the smallest portion of the
|
|
|
|
prefix matched by the pattern deleted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Li ${parameter##word}
|
1994-05-26 06:18:55 +00:00
|
|
|
Remove Largest Prefix Pattern. The word
|
|
|
|
is expanded to produce a pattern. The
|
|
|
|
parameter expansion then results in
|
|
|
|
parameter, with the largest portion of the
|
|
|
|
prefix matched by the pattern deleted.
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
|
|
.Ss Command Substitution
|
1994-05-26 06:18:55 +00:00
|
|
|
Command substitution allows the output of a command to be substituted in
|
|
|
|
place of the command name itself. Command substitution occurs when
|
|
|
|
the command is enclosed as follows:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
$(command)
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
or (``backquoted'' version):
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
`command`
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The shell expands the command substitution by executing command in a
|
|
|
|
subshell environment and replacing the command substitution
|
|
|
|
with the
|
|
|
|
standard output of the command, removing sequences of one or more
|
|
|
|
<newline>s at the end of the substitution. (Embedded <newline>s before
|
|
|
|
the end of the output are not removed; however, during field
|
|
|
|
splitting, they may be translated into <space>s, depending on the value
|
|
|
|
of IFS and quoting that is in effect.)
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Arithmetic Expansion
|
1994-05-26 06:18:55 +00:00
|
|
|
Arithmetic expansion provides a mechanism for evaluating an arithmetic
|
|
|
|
expression and substituting its value. The format for arithmetic
|
|
|
|
expansion is as follows:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
$((expression))
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The expression is treated as if it were in double-quotes, except
|
|
|
|
that a double-quote inside the expression is not treated specially. The
|
|
|
|
shell expands all tokens in the expression for parameter expansion,
|
|
|
|
command substitution, and quote removal.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
Next, the shell treats this as an arithmetic expression and
|
|
|
|
substitutes the value of the expression.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss White Space Splitting (Field Splitting)
|
1994-05-26 06:18:55 +00:00
|
|
|
After parameter expansion, command substitution, and
|
|
|
|
arithmetic expansion the shell scans the results of
|
|
|
|
expansions and substitutions that did not occur in double-quotes for
|
|
|
|
field splitting and multiple fields can result.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The shell treats each character of the IFS as a delimiter and use
|
|
|
|
the delimiters to split the results of parameter expansion and command
|
|
|
|
substitution into fields.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Ss Pathname Expansion (File Name Generation)
|
1996-12-14 06:20:03 +00:00
|
|
|
Unless the -f flag is set, file name generation is performed
|
|
|
|
after word splitting is complete. Each word is
|
1994-05-26 06:18:55 +00:00
|
|
|
viewed as a series of patterns, separated by slashes. The
|
|
|
|
process of expansion replaces the word with the names of
|
|
|
|
all existing files whose names can be formed by replacing
|
|
|
|
each pattern with a string that matches the specified pattern.
|
1996-12-14 06:20:03 +00:00
|
|
|
There are two restrictions on this: first, a pattern cannot match
|
|
|
|
a string containing a slash, and second,
|
1994-05-26 06:18:55 +00:00
|
|
|
a pattern cannot match a string starting with a period
|
|
|
|
unless the first character of the pattern is a period.
|
|
|
|
The next section describes the patterns used for both
|
1997-04-28 03:20:09 +00:00
|
|
|
Pathname Expansion and the
|
|
|
|
.Xr case 1
|
|
|
|
command.
|
|
|
|
.Ss Shell Patterns
|
1995-05-05 16:49:15 +00:00
|
|
|
A pattern consists of normal characters, which match themselves,
|
|
|
|
and meta-characters. The meta-characters are
|
1997-04-28 03:20:09 +00:00
|
|
|
``!'', ``*'', ``?'', and ``[''. These characters lose
|
1995-05-05 16:49:15 +00:00
|
|
|
their special meanings if they are quoted. When command
|
1994-05-26 06:18:55 +00:00
|
|
|
or variable substitution is performed and the dollar sign
|
|
|
|
or back quotes are not double quoted, the value of the
|
|
|
|
variable or the output of the command is scanned for these
|
|
|
|
characters and they are turned into meta-characters.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
|
|
|
An asterisk (``*'') matches any string of characters. A
|
1994-05-26 06:18:55 +00:00
|
|
|
question mark matches any single character. A left
|
|
|
|
bracket (``['') introduces a character class. The end of
|
|
|
|
the character class is indicated by a ``]''; if the ``]''
|
|
|
|
is missing then the ``['' matches a ``['' rather than
|
|
|
|
introducing a character class. A character class matches
|
1997-04-28 03:20:09 +00:00
|
|
|
any of the characters between the square brackets. A
|
1994-05-26 06:18:55 +00:00
|
|
|
range of characters may be specified using a minus sign.
|
|
|
|
The character class may be complemented by making an
|
|
|
|
exclamation point the first character of the character
|
|
|
|
class.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
To include a ``]'' in a character class, make it the first
|
|
|
|
character listed (after the ``!'', if any). To include a
|
1997-04-28 03:20:09 +00:00
|
|
|
minus sign, make it the first or last character listed.
|
|
|
|
.Ss Builtins
|
1994-05-26 06:18:55 +00:00
|
|
|
This section lists the builtin commands which
|
1997-04-28 03:20:09 +00:00
|
|
|
are builtin because they need to perform some operation
|
|
|
|
that can't be performed by a separate process. In addition to
|
|
|
|
these, there are several other commands that may be
|
|
|
|
builtin for efficiency (e.g.
|
|
|
|
.Xr printf 1 ,
|
|
|
|
.Xr echo 1 ,
|
|
|
|
.Xr test 1 ,
|
1994-05-26 06:18:55 +00:00
|
|
|
etc).
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -tag -width Ds
|
|
|
|
.It :
|
1996-09-01 10:22:36 +00:00
|
|
|
A null command that returns a 0 (true) exit value.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It \&. file
|
1996-09-01 10:22:36 +00:00
|
|
|
The commands in the specified file are read and executed by the shell.
|
1998-02-12 01:23:11 +00:00
|
|
|
If
|
|
|
|
.Ar file
|
|
|
|
contains any
|
|
|
|
.Ql /
|
|
|
|
characters, it is used as is. Otherwise, the shell searches the
|
|
|
|
.Ev PATH
|
|
|
|
for the file. If it is not found in the
|
|
|
|
.Ev PATH ,
|
|
|
|
it is sought in the current working directory.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It alias [ name[=string] ... ]
|
1994-05-26 06:18:55 +00:00
|
|
|
If name=string is specified, the shell defines the
|
|
|
|
alias ``name'' with value ``string''. If just ``name''
|
|
|
|
is specified, the value of the alias ``name'' is printed.
|
|
|
|
With no arguments, the alias builtin prints the
|
|
|
|
names and values of all defined aliases (see unalias).
|
1997-04-28 03:20:09 +00:00
|
|
|
.It bg [ job ] ...
|
1994-05-26 06:18:55 +00:00
|
|
|
Continue the specified jobs (or the current job if no
|
|
|
|
jobs are given) in the background.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It command command arg ...
|
1996-12-14 06:20:03 +00:00
|
|
|
Execute the specified builtin command. (This is useful when you
|
|
|
|
have a shell function with the same name
|
1994-05-26 06:18:55 +00:00
|
|
|
as a builtin command.)
|
1997-04-28 03:20:09 +00:00
|
|
|
.It cd [ directory ]
|
1994-05-26 06:18:55 +00:00
|
|
|
Switch to the specified directory (default $HOME).
|
1998-12-02 23:20:11 +00:00
|
|
|
If an entry for CDPATH appears in the environment
|
1994-05-26 06:18:55 +00:00
|
|
|
of the cd command or the shell variable CDPATH is set
|
|
|
|
and the directory name does not begin with a slash,
|
|
|
|
then the directories listed in CDPATH will be
|
|
|
|
searched for the specified directory. The format of
|
1996-12-14 06:20:03 +00:00
|
|
|
CDPATH is the same as that of PATH. In an interactive shell,
|
|
|
|
the cd command will print out the name of
|
1994-05-26 06:18:55 +00:00
|
|
|
the directory that it actually switched to if this is
|
|
|
|
different from the name that the user gave. These
|
|
|
|
may be different either because the CDPATH mechanism
|
|
|
|
was used or because a symbolic link was crossed.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It eval string ...
|
1994-05-26 06:18:55 +00:00
|
|
|
Concatenate all the arguments with spaces. Then
|
1997-04-28 03:20:09 +00:00
|
|
|
re-parse and execute the
|
|
|
|
command.
|
|
|
|
.It exec [ command arg ... ]
|
1994-05-26 06:18:55 +00:00
|
|
|
Unless command is omitted, the shell process is
|
|
|
|
replaced with the specified program (which must be a
|
1997-04-28 03:20:09 +00:00
|
|
|
real program, not a shell builtin or function). Any
|
1996-12-14 06:20:03 +00:00
|
|
|
redirections on the exec command are marked as permanent,
|
|
|
|
so that they are not undone when the exec command finishes.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It exit [ exitstatus ]
|
1994-05-26 06:18:55 +00:00
|
|
|
Terminate the shell process. If exitstatus is given
|
|
|
|
it is used as the exit status of the shell; otherwise
|
|
|
|
the exit status of the preceding command is used.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It export name ...
|
1994-05-26 06:18:55 +00:00
|
|
|
The specified names are exported so that they will
|
|
|
|
appear in the environment of subsequent commands.
|
|
|
|
The only way to un-export a variable is to unset it.
|
|
|
|
The shell allows the value of a variable to be set at the
|
|
|
|
same time it is exported by writing
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bd -literal -offset indent
|
|
|
|
export name=value
|
|
|
|
.Ed
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
With no arguments the export command lists the names
|
|
|
|
of all exported variables.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It fc [-e editor] [first [last]]
|
|
|
|
.It fc -l [-nr] [first [last]]
|
|
|
|
.It fc -s [old=new] [first]
|
1994-05-26 06:18:55 +00:00
|
|
|
The fc builtin lists, or edits and re-executes, commands
|
|
|
|
previously entered to an interactive shell.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -tag -width Ds
|
|
|
|
.It -e editor
|
1994-05-26 06:18:55 +00:00
|
|
|
Use the editor named by editor to edit the commands. The
|
|
|
|
editor string is a command name, subject to search via the
|
|
|
|
PATH variable. The value in the FCEDIT variable
|
|
|
|
is used as a default when -e is not specified. If
|
|
|
|
FCEDIT is null or unset, the value of the EDITOR
|
|
|
|
variable is used. If EDITOR is null or unset,
|
1997-04-28 03:20:09 +00:00
|
|
|
.Xr ed 1
|
|
|
|
is used as the editor.
|
|
|
|
.It -l (ell)
|
1994-05-26 06:18:55 +00:00
|
|
|
List the commands rather than invoking
|
|
|
|
an editor on them. The commands are written in the
|
|
|
|
sequence indicated by the first and last operands, as
|
|
|
|
affected by -r, with each command preceded by the command
|
|
|
|
number.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It -n
|
1994-05-26 06:18:55 +00:00
|
|
|
Suppress command numbers when listing with -l.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It -r
|
1994-05-26 06:18:55 +00:00
|
|
|
Reverse the order of the commands listed (with -l) or
|
|
|
|
edited (with neither -l nor -s).
|
1997-04-28 03:20:09 +00:00
|
|
|
.It -s
|
1994-05-26 06:18:55 +00:00
|
|
|
Re-execute the command without invoking an editor.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It first
|
|
|
|
.It last
|
1994-05-26 06:18:55 +00:00
|
|
|
Select the commands to list or edit. The number of
|
|
|
|
previous commands that can be accessed are determined
|
|
|
|
by the value of the HISTSIZE variable. The value of first
|
|
|
|
or last or both are one of the following:
|
1997-04-28 03:20:09 +00:00
|
|
|
.It [+]number
|
1994-05-26 06:18:55 +00:00
|
|
|
A positive number representing a command
|
|
|
|
number; command numbers can be displayed
|
|
|
|
with the -l option.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It -number
|
1994-05-26 06:18:55 +00:00
|
|
|
A negative decimal number representing the
|
|
|
|
command that was executed number of
|
|
|
|
commands previously. For example, -1 is
|
|
|
|
the immediately previous command.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It string
|
1994-05-26 06:18:55 +00:00
|
|
|
A string indicating the most recently
|
|
|
|
entered command that begins with that
|
|
|
|
string. If the old=new operand is not also
|
|
|
|
specified with -s, the string form of the
|
|
|
|
first operand cannot contain an embedded
|
|
|
|
equal sign.
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
|
|
.\".Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The following environment variables affect the execution of fc:
|
1997-04-28 03:20:09 +00:00
|
|
|
.Bl -tag -width Ds
|
|
|
|
.It Va FCEDIT
|
1994-05-26 06:18:55 +00:00
|
|
|
Name of the editor to use.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It Va HISTSIZE
|
1998-05-18 06:44:24 +00:00
|
|
|
The number of previous commands that are accessible.
|
1997-04-28 03:20:09 +00:00
|
|
|
.El
|
|
|
|
.It fg [ job ]
|
1994-05-26 06:18:55 +00:00
|
|
|
Move the specified job or the current job to the
|
|
|
|
foreground.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It getopts optstring var
|
1994-05-26 06:18:55 +00:00
|
|
|
The POSIX getopts command.
|
1996-12-14 06:20:03 +00:00
|
|
|
The getopts command deprecates the older getopt command.
|
|
|
|
The first argument should be a series of letters, each possibly
|
|
|
|
followed by a colon which indicates that the option takes an argument.
|
|
|
|
The specified variable is set to the parsed option. The index of
|
|
|
|
the next argument is placed into the shell variable OPTIND.
|
|
|
|
If an option takes an argument, it is placed into the shell variable
|
|
|
|
OPTARG. If an invalid option is encountered, var is set to '?'.
|
|
|
|
It returns a false value (1) when it encounters the end of the options.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It hash -rv command ...
|
1994-05-26 06:18:55 +00:00
|
|
|
The shell maintains a hash table which remembers the
|
|
|
|
locations of commands. With no arguments whatsoever,
|
1997-04-28 03:20:09 +00:00
|
|
|
the hash command prints out the contents of this
|
1994-05-26 06:18:55 +00:00
|
|
|
table. Entries which have not been looked at since
|
|
|
|
the last cd command are marked with an asterisk; it
|
|
|
|
is possible for these entries to be invalid.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1996-12-14 06:20:03 +00:00
|
|
|
With arguments, the hash command removes the specified commands
|
|
|
|
from the hash table (unless they are
|
1994-05-26 06:18:55 +00:00
|
|
|
functions) and then locates them. With the -v
|
|
|
|
option, hash prints the locations of the commands as
|
|
|
|
it finds them. The -r option causes the hash command
|
|
|
|
to delete all the entries in the hash table except
|
|
|
|
for functions.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It jobid [ job ]
|
|
|
|
Print the process id's of the processes in the job.
|
1994-05-26 06:18:55 +00:00
|
|
|
If the job argument is omitted, use the current job.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It jobs
|
1994-05-26 06:18:55 +00:00
|
|
|
This command lists out all the background processes
|
|
|
|
which are children of the current shell process.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It pwd
|
1994-05-26 06:18:55 +00:00
|
|
|
Print the current directory. The builtin command may
|
|
|
|
differ from the program of the same name because the
|
|
|
|
builtin command remembers what the current directory
|
|
|
|
is rather than recomputing it each time. This makes
|
|
|
|
it faster. However, if the current directory is
|
|
|
|
renamed, the builtin version of pwd will continue to
|
|
|
|
print the old name for the directory.
|
1997-09-29 15:15:16 +00:00
|
|
|
.It Li "read [ -p prompt ] [ -t timeout ] [ -e ] variable ...
|
1994-05-26 06:18:55 +00:00
|
|
|
The prompt is printed if the -p option is specified
|
|
|
|
and the standard input is a terminal. Then a line is
|
|
|
|
read from the standard input. The trailing newline
|
|
|
|
is deleted from the line and the line is split as
|
|
|
|
described in the section on word splitting above, and
|
|
|
|
the pieces are assigned to the variables in order.
|
1995-05-05 16:49:15 +00:00
|
|
|
If there are more pieces than variables, the remaining
|
|
|
|
pieces (along with the characters in IFS that
|
1994-05-26 06:18:55 +00:00
|
|
|
separated them) are assigned to the last variable.
|
1995-05-05 16:49:15 +00:00
|
|
|
If there are more variables than pieces, the remaining
|
|
|
|
variables are assigned the null string.
|
1997-04-28 03:20:09 +00:00
|
|
|
.Pp
|
1997-09-29 15:15:16 +00:00
|
|
|
If the -t option is specified the timeout elapses
|
|
|
|
before any input is supplied, the read command will
|
|
|
|
return without assigning any values. The timeout value
|
|
|
|
may optionally be followed by one of 's', 'm' or 'h' to
|
|
|
|
explicitly specify seconds, minutes or or hours. If none
|
|
|
|
is supplied, 's' is assumed.
|
|
|
|
.Pp
|
1994-05-26 06:18:55 +00:00
|
|
|
The -e option causes any backslashes in the input to
|
|
|
|
be treated specially. If a backslash is followed by
|
|
|
|
a newline, the backslash and the newline will be
|
|
|
|
deleted. If a backslash is followed by any other
|
1995-05-05 16:49:15 +00:00
|
|
|
character, the backslash will be deleted and the following
|
|
|
|
character will be treated as though it were
|
1994-05-26 06:18:55 +00:00
|
|
|
not in IFS, even if it is.
|
1997-04-28 03:20:09 +00:00
|
|
|
.It readonly name ...
|
1994-05-26 06:18:55 +00:00
|
|
|
The specified names are marked as read only, so that
|
|
|
|
they cannot be subsequently modified or unset. The shell
|
|
|
|
allows the value of a variable to be set at the same
|
|
|
|
time it is marked read only by writing
|
1997-04-28 03:20:09 +00:00
|
|
|
using the following form
|
|
|
|
.Bd -literal -offset indent
|
1994-05-26 06:18:55 +00:00
|
|
|
readonly name=value
|
1997-04-28 03:20:09 +00:00
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.Ed
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.Pp
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1994-05-26 06:18:55 +00:00
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With no arguments the readonly command lists the
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names of all read only variables.
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1997-04-28 03:20:09 +00:00
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.It Li "set [ { -options | +options | -- } ] arg ...
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1994-05-26 06:18:55 +00:00
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The set command performs three different functions.
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1997-04-28 03:20:09 +00:00
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.Bl -item
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.It
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1994-05-26 06:18:55 +00:00
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With no arguments, it lists the values of all shell
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variables.
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1997-04-28 03:20:09 +00:00
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.It
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1994-05-26 06:18:55 +00:00
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If options are given, it sets the specified option
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flags, or clears them as described in the section
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called ``Argument List Processing''.
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1997-04-28 03:20:09 +00:00
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.It
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1994-05-26 06:18:55 +00:00
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The third use of the set command is to set the values
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of the shell's positional parameters to the specified
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1997-04-28 03:20:09 +00:00
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args. To change the positional parameters without
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1996-12-14 06:20:03 +00:00
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changing any options, use ``--'' as the first argument
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to set. If no args are present, the set command
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1994-05-26 06:18:55 +00:00
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will clear all the positional parameters (equivalent
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to executing ``shift $#''.
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1997-04-28 03:20:09 +00:00
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.El
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.Pp
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.It setvar variable value
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1994-05-26 06:18:55 +00:00
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Assigns value to variable. (In general it is better
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to write variable=value rather than using setvar.
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Setvar is intended to be used in functions that
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assign values to variables whose names are passed as
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parameters.)
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1997-04-28 03:20:09 +00:00
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.It shift [ n ]
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1994-05-26 06:18:55 +00:00
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Shift the positional parameters n times. A shift
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sets the value of $1 to the value of $2, the value of
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$2 to the value of $3, and so on, decreasing the
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1997-04-28 03:20:09 +00:00
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value of $# by one. If there are zero positional
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1994-05-26 06:18:55 +00:00
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parameters, shifting doesn't do anything.
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1997-04-28 03:20:09 +00:00
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.It trap [ action ] signal ...
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1994-05-26 06:18:55 +00:00
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Cause the shell to parse and execute action when any
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1997-04-28 03:20:09 +00:00
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of the specified signals are received. The signals
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are specified by signal number. Action may be null
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1994-05-26 06:18:55 +00:00
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or omitted; the former causes the specified signal to
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be ignored and the latter causes the default action
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1997-04-28 03:20:09 +00:00
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to be taken. When the shell forks off a subshell, it
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1994-05-26 06:18:55 +00:00
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resets trapped (but not ignored) signals to the
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1997-04-28 03:20:09 +00:00
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default action. The trap command has no effect on
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1994-05-26 06:18:55 +00:00
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signals that were ignored on entry to the shell.
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1997-04-28 03:20:09 +00:00
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.It type [name] ...
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Interpret each name as a command and print the
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resolution of the command search. Possible resolutions are:
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shell keyword, alias, shell builtin, command, tracked alias
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and not found. For aliases the alias expansion is printed;
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for commands and tracked aliases the complete pathname of
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the command is printed.
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.It ulimit [ -HSacdflmnust ] [ limit ]
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Set or display resource limits (see
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.Xr getrlimit 2 ).
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1995-10-19 18:42:12 +00:00
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If ``limit'' is specified, the named resource will be set;
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otherwise the current resource value will be displayed.
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1997-04-28 03:20:09 +00:00
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.Pp
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1995-10-19 18:42:12 +00:00
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If ``-H'' is specified, the hard limits will be
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set or displayed. While everybody is allowed to reduce a
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hard limit, only the superuser can increase it. Option ``-S''
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specifies the soft limits instead. When displaying limits,
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only one of ``-S'' or ``-H'' can be given. The default is
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to display the soft limits, and to set both, the hard and
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the soft limits.
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1997-04-28 03:20:09 +00:00
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.Pp
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1995-10-19 18:42:12 +00:00
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Option ``-a'' requests to display all resources. The parameter
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``limit'' is not acceptable in this mode.
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1997-04-28 03:20:09 +00:00
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.Pp
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1995-10-19 18:42:12 +00:00
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The remaining options specify which resource value is to be
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displayed or modified. They are mutually exclusive.
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1997-04-28 03:20:09 +00:00
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.Bl -tag -width Ds
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.It -c coredumpsize
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1995-10-19 18:42:12 +00:00
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The maximal size of core dump files, in 512-byte blocks.
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1997-04-28 03:20:09 +00:00
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.It -d datasize
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1995-10-19 18:42:12 +00:00
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The maximal size of the data segment of a process, in kilobytes.
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1997-04-28 03:20:09 +00:00
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.It -f filesize
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1995-10-19 18:42:12 +00:00
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The maximal size of a file, in 512-byte blocks. This is the
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default.
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1997-04-28 03:20:09 +00:00
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.It -l lockedmem
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1995-10-19 18:42:12 +00:00
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The maximal size of memory that can be locked by a process, in
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kilobytes.
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1997-04-28 03:20:09 +00:00
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.It -m memoryuse
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1995-10-19 18:42:12 +00:00
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The maximal resident set size of a process, in kilobytes.
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1997-04-28 03:20:09 +00:00
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.It -n nofiles
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1995-10-19 18:42:12 +00:00
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The maximal number of descriptors that could be opened by a process.
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1997-04-28 03:20:09 +00:00
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.It -s stacksize
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1995-10-19 18:42:12 +00:00
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The maximal size of the stack segment, in kilobytes.
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1997-04-28 03:20:09 +00:00
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.It -t time
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1995-10-19 18:42:12 +00:00
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The maximal amount of CPU time to be used by each process, in seconds.
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1997-04-28 03:20:09 +00:00
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.It -u userproc
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The maximal number of simultaneous processes for this user ID.
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.El
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.It umask [ mask ]
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Set the value of umask (see
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.Xr umask 2 )
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to the specified
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1996-12-14 06:20:03 +00:00
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octal value. If the argument is omitted, the
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1994-05-26 06:18:55 +00:00
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umask value is printed.
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1997-04-28 03:20:09 +00:00
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.It unalias [-a] [name]
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1994-05-26 06:18:55 +00:00
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If ``name'' is specified, the shell removes that alias.
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If ``-a'' is specified, all aliases are removed.
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1997-04-28 03:20:09 +00:00
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.It unset name ...
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1994-05-26 06:18:55 +00:00
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The specified variables and functions are unset and
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unexported. If a given name corresponds to both a
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variable and a function, both the variable and the
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function are unset.
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1997-04-28 03:20:09 +00:00
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.It wait [ job ]
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1994-05-26 06:18:55 +00:00
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Wait for the specified job to complete and return the
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exit status of the last process in the job. If the
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argument is omitted, wait for all jobs to complete
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and the return an exit status of zero.
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1997-04-28 03:20:09 +00:00
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.El
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.Ss Commandline Editing
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When
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.Nm
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is being used interactively from a terminal, the current command
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1994-05-26 06:18:55 +00:00
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and the command history (see fc in Builtins) can be edited using vi-mode
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1997-04-28 03:20:09 +00:00
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commandline editing. This mode uses commands similar
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1994-05-26 06:18:55 +00:00
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to a subset of those described in the vi man page.
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1997-04-28 03:20:09 +00:00
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The command 'set -o vi' enables vi-mode editing and places
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.Nm
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into vi insert mode. With vi-mode enabled,
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.Nm
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can be switched between insert mode and command mode by typing <ESC>.
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Hitting <return> while in command mode will pass the line to the shell.
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.Pp
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Similarly, the 'set -o emacs' command can be used to enable a subset of
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emacs-style commandline editing features.
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1998-12-18 03:51:18 +00:00
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.Sh SEE ALSO
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.Xr expr 1 ,
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.Xr test 1
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1997-04-28 03:20:09 +00:00
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.Sh HISTORY
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1996-08-29 18:06:19 +00:00
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A
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1997-04-28 03:20:09 +00:00
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.Nm
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1996-08-29 18:06:19 +00:00
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command appeared in
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1997-04-28 03:20:09 +00:00
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.At V.1 .
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