1723 lines
42 KiB
Plaintext
1723 lines
42 KiB
Plaintext
.\" Copyright (c) 1980, 1993
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.\" The Regents of the University of California. All rights reserved.
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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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.\" @(#)csh.g 8.1 (Berkeley) 6/8/93
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.\" $Id$
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.\"
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.SH
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Glossary
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.PP
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This glossary lists the most important terms introduced in the
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introduction to the
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shell and gives references to sections of the shell
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document for further information about them.
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References of the form
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`pr (1)'
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indicate that the command
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.I pr
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is in the \s-2UNIX\s0 User Reference manual in section 1.
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You can look at an online copy of its manual page by doing
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.DS
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man 1 pr
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.DE
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References of the form (2.5)
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indicate that more information can be found in section 2.5 of this
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manual.
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.IP \&\fB.\fR 15n
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Your current directory has the name `.' as well as the name printed
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by the command
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.I pwd;
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see also
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.I dirs.
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The current directory `.' is usually the first
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.I component
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of the search path contained in the variable
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.I path ,
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thus commands which are in `.' are found first (2.2).
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The character `.' is also used in separating
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.I components
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of filenames
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(1.6).
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The character `.' at the beginning of a
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.I component
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of a
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.I pathname
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is treated specially and not matched by the
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.I "filename expansion"
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metacharacters `?', `*', and `[' `]' pairs (1.6).
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.IP \&\fB..\fR
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Each directory has a file `..' in it which is a reference to its
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parent directory.
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After changing into the directory with
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.I chdir ,
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i.e.
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.DS
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chdir paper
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.DE
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you can return to the parent directory by doing
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.DS
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chdir ..
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.DE
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The current directory is printed by
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.I pwd
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(2.7).
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.IP a.out
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Compilers which create executable images create them, by default, in the
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file
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.I a.out.
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for historical reasons (2.3).
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.IP "absolute pathname"
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.br
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A
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.I pathname
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which begins with a `/' is
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.I absolute
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since it specifies the
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.I path
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of directories from the beginning
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of the entire directory system \- called the
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.I root
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directory.
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.I Pathname s
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which are not
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.I absolute
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are called
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|
.I relative
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(see definition of
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.I "relative pathname" )
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(1.6).
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.IP alias
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An
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.I alias
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specifies a shorter or different name for a \s-2UNIX\s0
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command, or a transformation on a command to be performed in
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the shell.
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The shell has a command
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.I alias
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which establishes
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.I aliases
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and can print their current values.
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The command
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.I unalias
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is used to remove
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.I aliases
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(2.4).
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.IP argument
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Commands in \s-2UNIX\s0 receive a list of
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.I argument
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words.
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Thus the command
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.DS
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echo a b c
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.DE
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consists of the
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.I "command name"
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`echo' and three
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.I argument
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words `a', `b' and `c'.
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The set of
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.I arguments
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after the
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.I "command name"
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is said to be the
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|
.I "argument list"
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of the command (1.1).
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.IP argv
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The list of arguments to a command written in the shell language
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(a shell script or shell procedure) is stored in a variable called
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.I argv
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within the shell.
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This name is taken from the conventional name in the
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C programming language (3.4).
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.IP background
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Commands started without waiting for them to complete are called
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|
.I background
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commands (2.6).
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.IP base
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A filename is sometimes thought of as consisting of a
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.I base
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part, before any `.' character, and an
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.I extension
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\- the part after
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the `.'. See
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.I filename
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and
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.I extension
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(1.6) and basename (1).
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.IP bg
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The
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.I bg
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command causes a
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.I suspended
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job to continue execution in the
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.I background
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(2.6).
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.IP bin
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A directory containing binaries of programs and shell scripts to be
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executed is typically called a
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.I bin
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directory.
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The standard system
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.I bin
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directories are `/bin' containing the most
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heavily used commands and `/usr/bin' which contains most other user
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programs.
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Programs developed at UC Berkeley live in `/usr/ucb', while locally
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written programs live in `/usr/local'. Games are kept in the directory
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`/usr/games'.
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You can place binaries in any directory.
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If you wish to execute them often, the name of the directories
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should be a
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.I component
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of the variable
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.I path .
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.IP break
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.I Break
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|
is a builtin command used to exit from loops within the control
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structure of the shell (3.7).
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.IP breaksw
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|
The
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.I breaksw
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builtin command is used to exit from a
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.I switch
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control structure, like a
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.I break
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exits from loops (3.7).
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.IP builtin
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A command executed directly by the shell is called a
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.I builtin
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command.
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Most commands in \s-2UNIX\s0 are not built into the shell,
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but rather exist as files in
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.I bin
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directories.
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These commands are accessible because the directories in which
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they reside are named in the
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.I path
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variable.
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.IP case
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A
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.I case
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command is used as a label in a
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.I switch
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statement in the shell's control structure, similar to that of the
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language C.
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Details are given in the shell documentation `csh (1)' (3.7).
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.IP cat
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The
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.I cat
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program catenates a list of specified files on the
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.I "standard output" .
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It is usually used to look at the contents of a single file on the terminal,
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to `cat a file' (1.8, 2.3).
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.IP cd
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The
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.I cd
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command is used to change the
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.I "working directory" .
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With no arguments,
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.I cd
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changes your
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.I "working directory"
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to be your
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.I home
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directory (2.4, 2.7).
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.IP chdir
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|
The
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.I chdir
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command is a synonym for
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.I cd .
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.I Cd
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is usually used because it is easier to type.
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.IP chsh
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|
The
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.I chsh
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command is used to change the shell which you use on \s-2UNIX\s0.
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By default, you use an different version of the shell
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which resides in `/bin/sh'.
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|
You can change your shell to `/bin/csh' by doing
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.DS
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chsh your-login-name /bin/csh
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.DE
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|
Thus I would do
|
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.DS
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chsh bill /bin/csh
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.DE
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It is only necessary to do this once.
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The next time you log in to \s-2UNIX\s0 after doing this command,
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you will be using
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.I csh
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|
rather than the shell in `/bin/sh' (1.9).
|
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.IP cmp
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.I Cmp
|
|
is a program which compares files.
|
|
It is usually used on binary files, or to see if two files are identical (3.6).
|
|
For comparing text files the program
|
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.I diff ,
|
|
described in `diff (1)' is used.
|
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.IP command
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A function performed by the system, either by the shell
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(a builtin
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.I command )
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|
or by a program residing in a file in
|
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a directory within the \s-2UNIX\s0 system, is called a
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.I command
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(1.1).
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.IP "command name"
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.br
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|
When a command is issued, it consists of a
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.I "command name" ,
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|
which is the first word of the command,
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|
followed by arguments.
|
|
The convention on \s-2UNIX\s0 is that the first word of a
|
|
command names the function to be performed (1.1).
|
|
.IP "command substitution"
|
|
.br
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|
The replacement of a command enclosed in `\`' characters
|
|
by the text output by that command
|
|
is called
|
|
.I "command substitution"
|
|
(4.3).
|
|
.IP component
|
|
A part of a
|
|
.I pathname
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|
between `/' characters is called a
|
|
.I component
|
|
of that
|
|
.I pathname .
|
|
A variable
|
|
which has multiple strings as value is said to have
|
|
several
|
|
.I component s;
|
|
each string is a
|
|
.I component
|
|
of the variable.
|
|
.IP continue
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|
A builtin command which causes execution of the enclosing
|
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.I foreach
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|
or
|
|
.I while
|
|
loop to cycle prematurely.
|
|
Similar to the
|
|
.I continue
|
|
command in the programming language C (3.6).
|
|
.IP control-
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|
Certain special characters, called
|
|
.I control
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|
characters, are produced by holding down the \s-2CONTROL\s0 key
|
|
on your terminal and simultaneously pressing another character, much like
|
|
the \s-2SHIFT\s0 key is used to produce upper case characters. Thus
|
|
.I control- c
|
|
is produced by holding down the \s-2CONTROL\s0 key while pressing the
|
|
`c' key. Usually \s-2UNIX\s0 prints an caret (^) followed by the
|
|
corresponding letter when you type a
|
|
.I control
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|
character (e.g. `^C' for
|
|
.I control- c
|
|
(1.8).
|
|
.IP "core\ dump"
|
|
When a program terminates abnormally, the system places an image
|
|
of its current state in a file named `core'.
|
|
This
|
|
.I "core dump"
|
|
can be examined with the system debugger `adb (1)'
|
|
or `sdb (1)' in order to determine what went wrong with the program (1.8).
|
|
If the shell produces a message of the form
|
|
.DS
|
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Illegal instruction (core dumped)
|
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.DE
|
|
(where `Illegal instruction' is only one of several possible
|
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messages), you should report this to the author of the program
|
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or a system administrator,
|
|
saving the `core' file.
|
|
.IP cp
|
|
The
|
|
.I cp
|
|
(copy) program is used to copy the contents of one file into another
|
|
file.
|
|
It is one of the most commonly used \s-2UNIX\s0 commands (1.6).
|
|
.IP csh
|
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The name of the shell
|
|
program that this document describes.
|
|
.IP \&.cshrc
|
|
The file
|
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.I \&.cshrc
|
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in your
|
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.I home
|
|
directory is read by each shell as it begins execution.
|
|
It is usually used to change the setting of the variable
|
|
.I path
|
|
and to set
|
|
.I alias
|
|
parameters which are to take effect globally (2.1).
|
|
.IP cwd
|
|
The
|
|
.I cwd
|
|
variable in the shell holds the
|
|
.I "absolute pathname"
|
|
of the current
|
|
.I "working directory" \&.
|
|
It is changed by the shell whenever your current
|
|
.I "working directory"
|
|
changes and should not be changed otherwise (2.2).
|
|
.IP date
|
|
The
|
|
.I date
|
|
command prints the current date and time (1.3).
|
|
.IP debugging
|
|
.I Debugging
|
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is the process of correcting mistakes in programs and shell scripts.
|
|
The shell has several options and variables which may be used
|
|
to aid in shell
|
|
.I debugging
|
|
(4.4).
|
|
.IP default:
|
|
The label
|
|
.I default:
|
|
is used within shell
|
|
.I switch
|
|
statements, as it is in the C language
|
|
to label the code to be executed if none of the
|
|
.I case
|
|
labels matches the value switched on (3.7).
|
|
.IP \s-2DELETE\s0
|
|
The
|
|
\s-2DELETE\s0
|
|
or
|
|
\s-2RUBOUT\s0
|
|
key on the terminal normally causes an interrupt to be sent to the current job.
|
|
Many users change the interrupt character to be ^C.
|
|
.IP detached
|
|
A command that continues running in the
|
|
.I background
|
|
after you logout is said to be
|
|
.I detached .
|
|
.IP diagnostic
|
|
An error message produced by a program is often referred to as a
|
|
.I diagnostic .
|
|
Most error messages are not written to the
|
|
.I "standard output" ,
|
|
since that is often directed away from the terminal (1.3, 1.5).
|
|
Error messsages are instead written to the
|
|
.I "diagnostic output"
|
|
which may be directed away from the terminal, but usually is not.
|
|
Thus
|
|
.I diagnostics
|
|
will usually appear on the terminal (2.5).
|
|
.IP directory
|
|
A structure which contains files.
|
|
At any time you are in one particular
|
|
.I directory
|
|
whose names can be printed by the command
|
|
.I pwd .
|
|
The
|
|
.I chdir
|
|
command will change you to another
|
|
.I directory ,
|
|
and make the files
|
|
in that
|
|
.I directory
|
|
visible. The
|
|
.I directory
|
|
in which you are when you first login is your
|
|
.I home
|
|
directory (1.1, 2.7).
|
|
.IP "directory\ stack"
|
|
The shell saves the names of previous
|
|
.I "working directories"
|
|
in the
|
|
.I "directory stack"
|
|
when you change your current
|
|
.I "working directory"
|
|
via the
|
|
.I pushd
|
|
command. The
|
|
.I "directory stack"
|
|
can be printed by using the
|
|
.I dirs
|
|
command, which includes your current
|
|
.I "working directory"
|
|
as the first directory name on the left (2.7).
|
|
.IP dirs
|
|
The
|
|
.I dirs
|
|
command prints the shell's
|
|
.I "directory stack"
|
|
(2.7).
|
|
.IP du
|
|
The
|
|
.I du
|
|
command is a program (described in `du (1)') which
|
|
prints the number of disk blocks is all directories below
|
|
and including your current
|
|
.I "working directory"
|
|
(2.6).
|
|
.IP echo
|
|
The
|
|
.I echo
|
|
command prints its arguments (1.6, 3.6).
|
|
.IP else
|
|
The
|
|
.I else
|
|
command is part of the `if-then-else-endif' control
|
|
command construct (3.6).
|
|
.IP endif
|
|
If an
|
|
.I if
|
|
statement is ended with the word
|
|
.I then ,
|
|
all lines following the
|
|
.I if
|
|
up to a line starting with the word
|
|
.I endif
|
|
or
|
|
.I else
|
|
are executed if the condition between parentheses after the
|
|
.I if
|
|
is true (3.6).
|
|
.IP \s-2EOF\s0
|
|
An
|
|
.I "end\f1-\fPof\f1-\fPfile"
|
|
is generated by the terminal by a control-d,
|
|
and whenever a command reads to the end of a file which
|
|
it has been given as input.
|
|
Commands receiving input from a
|
|
.I pipe
|
|
receive an
|
|
.I "end\f1-\fPof\f1-\fPfile"
|
|
when the command sending them input completes.
|
|
Most commands terminate when they receive an
|
|
.I "end\f1-\fPof\f1-\fPfile" .
|
|
The shell has an option to ignore
|
|
.I "end\f1-\fPof\f1-\fPfile"
|
|
from a terminal
|
|
input which may help you keep from logging out accidentally
|
|
by typing too many control-d's (1.1, 1.8, 3.8).
|
|
.IP escape
|
|
A character `\e' used to prevent the special meaning of a metacharacter
|
|
is said to
|
|
.I escape
|
|
the character from its special meaning.
|
|
Thus
|
|
.DS
|
|
echo \e*
|
|
.DE
|
|
will echo the character `*' while just
|
|
.DS
|
|
echo *
|
|
.DE
|
|
will echo the names of the file in the current directory.
|
|
In this example, \e
|
|
.I escape s
|
|
`*' (1.7).
|
|
There is also a non-printing character called
|
|
.I escape ,
|
|
usually labelled
|
|
\s-2ESC\s0
|
|
or
|
|
\s-2ALTMODE\s0
|
|
on terminal keyboards.
|
|
Some older \s-2UNIX\s0 systems use this character to indicate that
|
|
output is to be
|
|
.I suspended .
|
|
Most systems use control-s to stop the output and control-q to start it.
|
|
.IP /etc/passwd
|
|
This file contains information about the accounts currently on the
|
|
system.
|
|
It consists of a line for each account with fields separated by
|
|
`:' characters (1.8).
|
|
You can look at this file by saying
|
|
.DS
|
|
cat /etc/passwd
|
|
.DE
|
|
The commands
|
|
.I finger
|
|
and
|
|
.I grep
|
|
are often used to search for information in this file.
|
|
See `finger (1)', `passwd(5)', and `grep (1)' for more details.
|
|
.IP exit
|
|
The
|
|
.I exit
|
|
command is used to force termination of a shell script,
|
|
and is built into the shell (3.9).
|
|
.IP "exit\ status"
|
|
A command which discovers a problem may reflect this back to the command
|
|
(such as a shell) which invoked (executed) it.
|
|
It does this by returning a non-zero number as its
|
|
.I "exit status" ,
|
|
a status of zero being considered
|
|
`normal termination'.
|
|
The
|
|
.I exit
|
|
command can be used to force a shell command script to give a non-zero
|
|
.I "exit status"
|
|
(3.6).
|
|
.IP expansion
|
|
The replacement of strings in the shell input which contain metacharacters
|
|
by other strings is referred to as the process of
|
|
.I expansion .
|
|
Thus the replacement of the word `*' by a sorted list of files
|
|
in the current directory is a `filename expansion'.
|
|
Similarly the replacement of the characters `!!' by the text of
|
|
the last command is a `history expansion'.
|
|
.I Expansions
|
|
are also referred to as
|
|
.I substitutions
|
|
(1.6, 3.4, 4.2).
|
|
.IP expressions
|
|
.I Expressions
|
|
are used in the shell
|
|
to control the conditional structures used in the writing of shell
|
|
scripts and in calculating values for these scripts.
|
|
The operators available in shell
|
|
.I expressions
|
|
are those of the language
|
|
C (3.5).
|
|
.IP extension
|
|
Filenames often consist of a
|
|
.I base
|
|
name and an
|
|
.I extension
|
|
separated by the character `.'.
|
|
By convention, groups of related files often share the same
|
|
.I root
|
|
name.
|
|
Thus if `prog.c' were a C program, then the object file for this
|
|
program would be stored in `prog.o'.
|
|
Similarly a paper written with the
|
|
`\-me'
|
|
nroff macro package might be stored in
|
|
`paper.me'
|
|
while a formatted version of this paper might be kept in
|
|
`paper.out' and a list of spelling errors in
|
|
`paper.errs' (1.6).
|
|
.IP fg
|
|
The
|
|
.I "job control"
|
|
command
|
|
.I fg
|
|
is used to run a
|
|
.I background
|
|
or
|
|
.I suspended
|
|
job in the
|
|
.I foreground
|
|
(1.8, 2.6).
|
|
.IP filename
|
|
Each file in \s-2UNIX\s0 has a name consisting of up to 14 characters
|
|
and not including the character `/' which is used in
|
|
.I pathname
|
|
building. Most
|
|
.I filenames
|
|
do not begin with the character `.', and contain
|
|
only letters and digits with perhaps a `.' separating the
|
|
.I base
|
|
portion of the
|
|
.I filename
|
|
from an
|
|
.I extension
|
|
(1.6).
|
|
.IP "filename expansion"
|
|
.br
|
|
.I "Filename expansion"
|
|
uses the metacharacters `*', `?' and `[' and `]'
|
|
to provide a convenient mechanism for naming files.
|
|
Using
|
|
.I "filename expansion"
|
|
it is easy to name all the files in
|
|
the current directory, or all files which have a common
|
|
.I root
|
|
name. Other
|
|
.I "filename expansion"
|
|
mechanisms use the metacharacter `~' and allow
|
|
files in other users' directories to be named easily (1.6, 4.2).
|
|
.IP flag
|
|
Many \s-2UNIX\s0 commands accept arguments which are not the names
|
|
of files or other users but are used to modify the action of the commands.
|
|
These are referred to as
|
|
.I flag
|
|
options, and by convention consist of one or more letters preceded by
|
|
the character `\-' (1.2).
|
|
Thus the
|
|
.I ls
|
|
(list files) command has an option
|
|
`\-s' to list the sizes of files.
|
|
This is specified
|
|
.DS
|
|
ls \-s
|
|
.DE
|
|
.IP foreach
|
|
The
|
|
.I foreach
|
|
command is used in shell scripts and at the terminal to specify
|
|
repetition of a sequence of commands while the value of a certain
|
|
shell variable ranges through a specified list (3.6, 4.1).
|
|
.IP foreground
|
|
When commands are executing in the normal way such that the
|
|
shell is waiting for them to finish before prompting for another
|
|
command they are said to be
|
|
.I "foreground jobs"
|
|
or
|
|
.I "running in the foreground" \&.
|
|
This is as opposed to
|
|
.I background .
|
|
.I Foreground
|
|
jobs can be stopped by signals
|
|
from the terminal caused by typing different
|
|
control characters at the keyboard (1.8, 2.6).
|
|
.IP goto
|
|
The shell has a command
|
|
.I goto
|
|
used in shell scripts to transfer control to a given label (3.7).
|
|
.IP grep
|
|
The
|
|
.I grep
|
|
command searches through a list of argument files for a specified string.
|
|
Thus
|
|
.DS
|
|
grep bill /etc/passwd
|
|
.DE
|
|
will print each line in the file
|
|
.I "/etc/passwd"
|
|
which contains the string `bill'.
|
|
Actually,
|
|
.I grep
|
|
scans for
|
|
.I "regular expressions"
|
|
in the sense of the editors
|
|
`ed (1)' and `ex (1)'.
|
|
.I Grep
|
|
stands for
|
|
`globally find
|
|
.I "regular expression"
|
|
and print' (2.4).
|
|
.IP head
|
|
The
|
|
.I head
|
|
command prints the first few lines of one or more files.
|
|
If you have a bunch of files containing text which you are wondering
|
|
about it is sometimes useful to run
|
|
.I head
|
|
with these files as arguments.
|
|
This will usually show enough of what is in these files to let you decide
|
|
which you are interested in (1.5).
|
|
.br
|
|
.I Head
|
|
is also used to describe the part of a
|
|
.I pathname
|
|
before and including the last `/' character. The
|
|
.I tail
|
|
of a
|
|
.I pathname
|
|
is the part after the last `/'. The `:h' and `:t' modifiers allow the
|
|
.I head
|
|
or
|
|
.I tail
|
|
of a
|
|
.I pathname
|
|
stored in a shell variable to be used (3.6).
|
|
.IP history
|
|
The
|
|
.I history
|
|
mechanism of the shell allows previous commands to be repeated,
|
|
possibly after modification to correct typing mistakes or to change
|
|
the meaning of the command.
|
|
The shell has a
|
|
.I "history list"
|
|
where these commands are kept, and a
|
|
.I history
|
|
variable which controls how large this list is (2.3).
|
|
.IP "home\ directory"
|
|
.br
|
|
Each user has a
|
|
.I "home directory" ,
|
|
which is given in your entry
|
|
in the password file,
|
|
.I /etc/passwd .
|
|
This is the directory which you are placed in when you first login.
|
|
The
|
|
.I cd
|
|
or
|
|
.I chdir
|
|
command with no arguments takes you back to this directory, whose
|
|
name is recorded in the shell variable
|
|
.I home .
|
|
You can also access the
|
|
.I "home directories"
|
|
of other users in forming
|
|
filenames using a
|
|
.I "filename expansion"
|
|
notation and the character `~' (1.6).
|
|
.IP if
|
|
A conditional command within the shell, the
|
|
.I if
|
|
command is used in shell command scripts to make decisions
|
|
about what course of action to take next (3.6).
|
|
.IP ignoreeof
|
|
Normally, your shell will exit, printing
|
|
`logout'
|
|
if you type a control-d at a prompt of `% '.
|
|
This is the way you usually log off the system.
|
|
You can
|
|
.I set
|
|
the
|
|
.I ignoreeof
|
|
variable if you wish in your
|
|
.I \&.login
|
|
file and then use the command
|
|
.I logout
|
|
to logout.
|
|
This is useful if you sometimes accidentally type too many control-d
|
|
characters, logging yourself off
|
|
(2.2).
|
|
.IP input
|
|
Many commands on \s-2UNIX\s0 take information from the terminal or from
|
|
files which they then act on.
|
|
This information is called
|
|
.I input .
|
|
Commands normally read for
|
|
.I input
|
|
from their
|
|
.I "standard input"
|
|
which is, by default, the terminal.
|
|
This
|
|
.I "standard input"
|
|
can be redirected from a file using a shell metanotation
|
|
with the character `<'.
|
|
Many commands will also read from a file specified as argument.
|
|
Commands placed in
|
|
.I pipelines
|
|
will read from the output of the previous
|
|
command in the
|
|
.I pipeline .
|
|
The leftmost command in a
|
|
.I pipeline
|
|
reads from the terminal if
|
|
you neither redirect its
|
|
.I input
|
|
nor give it a filename to use as
|
|
.I "standard input" .
|
|
Special mechanisms exist for supplying input to commands in shell
|
|
scripts (1.5, 3.8).
|
|
.IP interrupt
|
|
An
|
|
.I interrupt
|
|
is a signal to a program that is generated by typing ^C. (On older versions
|
|
of UNIX the \s-2RUBOUT\s0 or \s-2DELETE\s0 key were used for this purpose.)
|
|
It causes most programs to stop execution.
|
|
Certain programs, such as the shell and the editors,
|
|
handle an
|
|
.I interrupt
|
|
in special ways, usually by stopping what they
|
|
are doing and prompting for another command.
|
|
While the shell is executing another command and waiting for it
|
|
to finish, the shell does not listen to
|
|
.I interrupts.
|
|
The shell often wakes up when you hit
|
|
.I interrupt
|
|
because many commands
|
|
die when they receive an
|
|
.I interrupt
|
|
(1.8, 3.9).
|
|
.IP job
|
|
One or more commands
|
|
typed on the same input line separated by `|' or `;' characters
|
|
are run together and are called a
|
|
.I job \&.
|
|
Simple commands run by themselves without any `|' or `;' characters
|
|
are the simplest
|
|
.I jobs.
|
|
.I Jobs
|
|
are classified as
|
|
.I foreground ,
|
|
.I background ,
|
|
or
|
|
.I suspended
|
|
(2.6).
|
|
.IP "job\ control"
|
|
The builtin functions that control the execution of
|
|
jobs are called
|
|
.I "job control"
|
|
commands. These are
|
|
.I "bg, fg, stop, kill"
|
|
(2.6).
|
|
.IP "job\ number"
|
|
When each job
|
|
is started it is assigned a small number called a
|
|
.I "job number"
|
|
which is printed next to the job in the output of the
|
|
.I jobs
|
|
command. This number, preceded by a `%' character, can be used as an argument
|
|
to
|
|
.I "job control"
|
|
commands to indicate
|
|
a specific job (2.6).
|
|
.IP jobs
|
|
The
|
|
.I jobs
|
|
command prints a table showing
|
|
jobs that are either running in the
|
|
.I background
|
|
or are
|
|
.I suspended
|
|
(2.6).
|
|
.IP kill
|
|
A command which sends a
|
|
signal
|
|
to a job causing it to terminate (2.6).
|
|
.IP \&.login
|
|
The file
|
|
.I \&.login
|
|
in your
|
|
.I home
|
|
directory is read by the shell each time you login to \s-2UNIX\s0
|
|
and the commands there are executed.
|
|
There are a number of commands which are usefully placed here,
|
|
especially
|
|
.I set
|
|
commands to the shell itself (2.1).
|
|
.IP "login\ shell"
|
|
The shell that is started on your terminal when you login is called
|
|
your
|
|
.I "login shell" .
|
|
It is different from other shells which you may run (e.g. on
|
|
shell scripts)
|
|
in that it reads the
|
|
.I \&.login
|
|
file before reading commands from the terminal and it reads the
|
|
.I \&.logout
|
|
file after you logout
|
|
(2.1).
|
|
.IP logout
|
|
The
|
|
.I logout
|
|
command causes a login shell to exit.
|
|
Normally, a login shell will exit when you hit control-d
|
|
generating an
|
|
.I end\f1-\fPof\f1-\fPfile,
|
|
but if you have set
|
|
.I ignoreeof
|
|
in you
|
|
.I \&.login
|
|
file then this will not work and you must use
|
|
.I logout
|
|
to log off the \s-2UNIX\s0 system (2.8).
|
|
.IP \&.logout
|
|
When you log off of \s-2UNIX\s0 the shell will execute commands from
|
|
the file
|
|
.I \&.logout
|
|
in your
|
|
.I home
|
|
directory after it prints `logout'.
|
|
.IP lpr
|
|
The command
|
|
.I lpr
|
|
is the line printer daemon.
|
|
The standard input of
|
|
.I lpr
|
|
spooled and printed on the \s-2UNIX\s0 line printer.
|
|
You can also give
|
|
.I lpr
|
|
a list of filenames as arguments to be printed.
|
|
It is most common to use
|
|
.I lpr
|
|
as the last component of a
|
|
.I pipeline
|
|
(2.3).
|
|
.IP ls
|
|
The
|
|
.I ls
|
|
(list files) command is one of the most commonly used \s-2UNIX\s0
|
|
commands.
|
|
With no argument filenames it prints the names of the files in the
|
|
current directory.
|
|
It has a number of useful
|
|
.I flag
|
|
arguments, and can also be given the names of directories
|
|
as arguments, in which case it lists the names of the files in these
|
|
directories (1.2).
|
|
.IP mail
|
|
The
|
|
.I mail
|
|
program is used to send and receive messages from other \s-2UNIX\s0
|
|
users (1.1, 2.1), whether they are logged on or not.
|
|
.IP make
|
|
The
|
|
.I make
|
|
command is used to maintain one or more related files and to
|
|
organize functions to be performed on these files.
|
|
In many ways
|
|
.I make
|
|
is easier to use, and more helpful than
|
|
shell command scripts (3.2).
|
|
.IP makefile
|
|
The file containing commands for
|
|
.I make
|
|
is called
|
|
.I makefile
|
|
or
|
|
.I Makefile
|
|
(3.2).
|
|
.IP manual
|
|
The
|
|
.I manual
|
|
often referred to is the
|
|
`\s-2UNIX\s0 manual'.
|
|
It contains 8 numbered sections with a description of each \s-2UNIX\s0
|
|
program (section 1), system call (section 2), subroutine (section 3),
|
|
device (section 4), special data structure (section 5), game (section 6),
|
|
miscellaneous item (section 7) and system administration program (section 8).
|
|
There are also supplementary documents (tutorials and reference guides)
|
|
for individual programs which require explanation in more detail.
|
|
An online version of the
|
|
.I manual
|
|
is accessible through the
|
|
.I man
|
|
command.
|
|
Its documentation can be obtained online via
|
|
.DS
|
|
man man
|
|
.DE
|
|
If you can't decide what manual page to look in, try the
|
|
.I apropos (1)
|
|
command.
|
|
The supplementary documents are in subdirectories of /usr/doc.
|
|
.IP metacharacter
|
|
.br
|
|
Many characters which are neither letters nor digits have special meaning
|
|
either to the shell or to \s-2UNIX\s0.
|
|
These characters are called
|
|
.I metacharacters .
|
|
If it is necessary to place these characters in arguments to commands
|
|
without them having their special meaning then they must be
|
|
.I quoted .
|
|
An example of a
|
|
.I metacharacter
|
|
is the character `>' which is used
|
|
to indicate placement of output into a file.
|
|
For the purposes of the
|
|
.I history
|
|
mechanism,
|
|
most unquoted
|
|
.I metacharacters
|
|
form separate words (1.4).
|
|
The appendix to this user's manual lists the
|
|
.I metacharacters
|
|
in groups by their function.
|
|
.IP mkdir
|
|
The
|
|
.I mkdir
|
|
command is used to create a new directory.
|
|
.IP modifier
|
|
Substitutions with the
|
|
.I history
|
|
mechanism, keyed by the character `!'
|
|
or of variables using the metacharacter `$', are often subjected
|
|
to modifications, indicated by placing the character `:' after the
|
|
substitution and following this with the
|
|
.I modifier
|
|
itself.
|
|
The
|
|
.I "command substitution"
|
|
mechanism can also be used to perform modification in a similar way,
|
|
but this notation is less clear (3.6).
|
|
.IP more
|
|
The program
|
|
.I more
|
|
writes a file on your terminal allowing you to control how much text
|
|
is displayed at a time.
|
|
.I More
|
|
can move through the file screenful by screenful, line by line,
|
|
search forward for a string, or start again at the beginning of the file.
|
|
It is generally the easiest way of viewing a file (1.8).
|
|
.IP noclobber
|
|
The shell has a variable
|
|
.I noclobber
|
|
which may be set in the file
|
|
.I \&.login
|
|
to prevent accidental destruction of files by the `>' output redirection
|
|
metasyntax of the shell (2.2, 2.5).
|
|
.IP noglob
|
|
The shell variable
|
|
.I noglob
|
|
is set to suppress the
|
|
.I "filename expansion"
|
|
of arguments containing the metacharacters `~', `*', `?', `[' and `]' (3.6).
|
|
.IP notify
|
|
The
|
|
.I notify
|
|
command tells the shell to report on the termination of a specific
|
|
.I "background job"
|
|
at the exact time it occurs as opposed to waiting
|
|
until just before the next prompt to report the termination.
|
|
The
|
|
.I notify
|
|
variable, if set, causes the shell to always report the termination
|
|
of
|
|
.I background
|
|
jobs exactly when they occur (2.6).
|
|
.IP onintr
|
|
The
|
|
.I onintr
|
|
command is built into the shell and is used to control the action
|
|
of a shell command script when an
|
|
.I interrupt
|
|
signal is received (3.9).
|
|
.IP output
|
|
Many commands in \s-2UNIX\s0 result in some lines of text which are
|
|
called their
|
|
.I output.
|
|
This
|
|
.I output
|
|
is usually placed on what is known as the
|
|
.I "standard output"
|
|
which is normally connected to the user's terminal.
|
|
The shell has a syntax using the metacharacter `>' for redirecting
|
|
the
|
|
.I "standard output"
|
|
of a command to a file (1.3).
|
|
Using the
|
|
.I pipe
|
|
mechanism and the metacharacter `|' it is also possible for
|
|
the
|
|
.I "standard output"
|
|
of one command to become the
|
|
.I "standard input"
|
|
of another command (1.5).
|
|
Certain commands such as the line printer daemon
|
|
.I p
|
|
do not place their results on the
|
|
.I "standard output"
|
|
but rather in more
|
|
useful places such as on the line printer (2.3).
|
|
Similarly the
|
|
.I write
|
|
command places its output on another user's terminal rather than its
|
|
.I "standard output"
|
|
(2.3).
|
|
Commands also have a
|
|
.I "diagnostic output"
|
|
where they write their error messages.
|
|
Normally these go to the terminal even if the
|
|
.I "standard output"
|
|
has been sent to a file or another command, but it is possible
|
|
to direct error diagnostics along with
|
|
.I "standard output"
|
|
using a special metanotation (2.5).
|
|
.IP path
|
|
The shell has a variable
|
|
.I path
|
|
which gives the names of the directories in which it searches for
|
|
the commands which it is given.
|
|
It always checks first to see if the command it is given is
|
|
built into the shell.
|
|
If it is, then it need not search for the command as it can do it internally.
|
|
If the command is not builtin, then the shell searches for a file
|
|
with the name given in each of the directories in the
|
|
.I path
|
|
variable, left to right.
|
|
Since the normal definition of the
|
|
.I path
|
|
variable is
|
|
.DS
|
|
path (. /usr/ucb /bin /usr/bin)
|
|
.DE
|
|
the shell normally looks in the current directory, and then in
|
|
the standard system directories `/usr/ucb', `/bin' and `/usr/bin' for the named
|
|
command (2.2).
|
|
If the command cannot be found the shell will print an error diagnostic.
|
|
Scripts of shell commands will be executed using another shell to interpret
|
|
them if they have `execute' permission set.
|
|
This is normally true because a command of the form
|
|
.DS
|
|
chmod 755 script
|
|
.DE
|
|
was executed to turn this execute permission on (3.3).
|
|
If you add new commands to a directory in the
|
|
.I path ,
|
|
you should issue
|
|
the command
|
|
.I rehash
|
|
(2.2).
|
|
.IP pathname
|
|
A list of names, separated by `/' characters, forms a
|
|
.I pathname.
|
|
Each
|
|
.I component,
|
|
between successive `/' characters, names a directory
|
|
in which the next
|
|
.I component
|
|
file resides.
|
|
.I Pathnames
|
|
which begin with the character `/' are interpreted relative
|
|
to the
|
|
.I root
|
|
directory in the filesystem.
|
|
Other
|
|
.I pathnames
|
|
are interpreted relative to the current directory
|
|
as reported by
|
|
.I pwd.
|
|
The last component of a
|
|
.I pathname
|
|
may name a directory, but
|
|
usually names a file.
|
|
.IP pipeline
|
|
A group of commands which are connected together, the
|
|
.I "standard output"
|
|
of each connected to the
|
|
.I "standard input"
|
|
of the next,
|
|
is called a
|
|
.I pipeline.
|
|
The
|
|
.I pipe
|
|
mechanism used to connect these commands is indicated by
|
|
the shell metacharacter `|' (1.5, 2.3).
|
|
.IP popd
|
|
The
|
|
.I popd
|
|
command changes the shell's
|
|
.I "working directory"
|
|
to the directory you most recently left using the
|
|
.I pushd
|
|
command. It returns to the directory without having to type its name,
|
|
forgetting the name of the current
|
|
.I "working directory"
|
|
before doing so (2.7).
|
|
.IP port
|
|
The part of a computer system to which each terminal is
|
|
connected is called a
|
|
.I port .
|
|
Usually the system has a fixed number of
|
|
.I ports ,
|
|
some of which are connected to telephone lines
|
|
for dial-up access, and some of which are permanently
|
|
wired directly to specific terminals.
|
|
.IP pr
|
|
The
|
|
.I pr
|
|
command is used to prepare listings of the contents of files
|
|
with headers giving the name of the file and the date and
|
|
time at which the file was last modified (2.3).
|
|
.IP printenv
|
|
The
|
|
.I printenv
|
|
command is used
|
|
to print the current setting of variables in the environment
|
|
(2.8).
|
|
.IP process
|
|
An instance of a running program is called a
|
|
.I process
|
|
(2.6).
|
|
\s-2UNIX\s0 assigns each
|
|
.I process
|
|
a unique number when it is
|
|
started \- called the
|
|
.I "process number" .
|
|
.I "Process numbers"
|
|
can be used to stop individual
|
|
.I processes
|
|
using the
|
|
.I kill
|
|
or
|
|
.I stop
|
|
commands when the
|
|
.I processes
|
|
are part of a detached
|
|
.I background
|
|
job.
|
|
.IP program
|
|
Usually synonymous with
|
|
.I command ;
|
|
a binary file or shell command script
|
|
which performs a useful function is often
|
|
called a
|
|
.I program .
|
|
.IP prompt
|
|
Many programs will print a
|
|
.I prompt
|
|
on the terminal when they expect input.
|
|
Thus the editor
|
|
`ex (1)' will print a `:' when it expects input.
|
|
The shell
|
|
.I prompts
|
|
for input with `% ' and occasionally with `? ' when
|
|
reading commands from the terminal (1.1).
|
|
The shell has a variable
|
|
.I prompt
|
|
which may be set to a different value to change the shell's main
|
|
.I prompt .
|
|
This is mostly used when debugging the shell (2.8).
|
|
.IP pushd
|
|
The
|
|
.I pushd
|
|
command, which means `push directory', changes the shell's
|
|
.I "working directory"
|
|
and also remembers the current
|
|
.I "working directory"
|
|
before the change is made, allowing you to return to the same
|
|
directory via the
|
|
.I popd
|
|
command later without retyping its name (2.7).
|
|
.IP ps
|
|
The
|
|
.I ps
|
|
command is used to show the processes you are currently running.
|
|
Each process is shown with its unique process number,
|
|
an indication of the terminal name it is attached to,
|
|
an indication of the state of the process (whether it is running,
|
|
stopped, awaiting some event (sleeping), and whether it is swapped out),
|
|
and the amount of \s-2CPU\s0 time it has used so far.
|
|
The command is identified by printing some of the words used
|
|
when it was invoked (2.6).
|
|
Shells, such as the
|
|
.I csh
|
|
you use to run the
|
|
.I ps
|
|
command, are not normally shown in the output.
|
|
.IP pwd
|
|
The
|
|
.I pwd
|
|
command prints the full
|
|
.I pathname
|
|
of the current
|
|
.I "working directory" \&.
|
|
The
|
|
.I dirs
|
|
builtin command is usually a better and faster choice.
|
|
.IP quit
|
|
The
|
|
.I quit
|
|
signal, generated by a control-\e,
|
|
is used to terminate programs which are behaving unreasonably.
|
|
It normally produces a core image file (1.8).
|
|
.IP quotation
|
|
The process by which metacharacters are prevented their special
|
|
meaning, usually by using the character `\' in pairs, or by
|
|
using the character `\e', is referred to as
|
|
.I quotation
|
|
(1.7).
|
|
.IP redirection
|
|
The routing of input or output from or to a file is known
|
|
as
|
|
.I redirection
|
|
of input or output (1.3).
|
|
.IP rehash
|
|
The
|
|
.I rehash
|
|
command tells the shell to rebuild its internal table of which commands
|
|
are found in which directories in your
|
|
.I path .
|
|
This is necessary when a new program is installed in one of these
|
|
directories (2.8).
|
|
.IP "relative pathname"
|
|
.br
|
|
A
|
|
.I pathname
|
|
which does not begin with a `/' is called a
|
|
.I "relative pathname"
|
|
since it is interpreted
|
|
.I relative
|
|
to the current
|
|
.I "working directory" .
|
|
The first
|
|
.I component
|
|
of such a
|
|
.I pathname
|
|
refers to some file or directory in the
|
|
.I "working directory" ,
|
|
and subsequent
|
|
.I components
|
|
between `/' characters refer to directories below the
|
|
.I "working directory" .
|
|
.I Pathnames
|
|
that are not
|
|
.I relative
|
|
are called
|
|
.I "absolute pathnames"
|
|
(1.6).
|
|
.IP repeat
|
|
The
|
|
.I repeat
|
|
command iterates another command a specified number of times.
|
|
.IP root
|
|
The directory
|
|
that is at the top of the entire directory structure is called the
|
|
.I root
|
|
directory since it is the `root' of the entire tree structure of
|
|
directories. The name used in
|
|
.I pathnames
|
|
to indicate the
|
|
.I root
|
|
is `/'.
|
|
.I Pathnames
|
|
starting with `/' are said to be
|
|
.I absolute
|
|
since they start at the
|
|
.I root
|
|
directory.
|
|
.I Root
|
|
is also used as the part of a
|
|
.I pathname
|
|
that is left after removing
|
|
the
|
|
.I extension .
|
|
See
|
|
.I filename
|
|
for a further explanation (1.6).
|
|
.IP \s-2RUBOUT\s0
|
|
The \s-2RUBOUT\s0 or \s-2DELETE\s0
|
|
key is often used to erase the previously typed character; some users
|
|
prefer the \s-2BACKSPACE\s0 for this purpose. On older versions of \s-2UNIX\s0
|
|
this key served as the \s-2INTR\s0 character.
|
|
.IP "scratch file"
|
|
Files whose names begin with a `#' are referred to as
|
|
.I "scratch files" ,
|
|
since they are automatically removed by the system after a couple of
|
|
days of non-use, or more frequently if disk space becomes tight (1.3).
|
|
.IP script
|
|
Sequences of shell commands placed in a file are called shell command
|
|
.I scripts .
|
|
It is often possible to perform simple tasks using these
|
|
.I scripts
|
|
without writing a program in a language such as C, by
|
|
using the shell to selectively run other programs (3.3, 3.10).
|
|
.IP set
|
|
The builtin
|
|
.I set
|
|
command is used to assign new values to shell variables
|
|
and to show the values of the current variables.
|
|
Many shell variables have special meaning to the shell itself.
|
|
Thus by using the
|
|
.I set
|
|
command the behavior of the shell can be affected (2.1).
|
|
.IP setenv
|
|
Variables in the environment `environ (5)'
|
|
can be changed by using the
|
|
.I setenv
|
|
builtin command (2.8).
|
|
The
|
|
.I printenv
|
|
command can be used to print the value of the variables in the environment.
|
|
.IP shell
|
|
A
|
|
.I shell
|
|
is a command language interpreter.
|
|
It is possible to write and run your own
|
|
.I shell ,
|
|
as
|
|
.I shells
|
|
are no different than any other programs as far as the
|
|
system is concerned.
|
|
This manual deals with the details of one particular
|
|
.I shell ,
|
|
called
|
|
.I csh.
|
|
.IP "shell script"
|
|
See
|
|
.I script
|
|
(3.3, 3.10).
|
|
.IP signal
|
|
A
|
|
.I signal
|
|
in \s-2UNIX\s0 is a short message that is sent to a running program
|
|
which causes something to happen to that process.
|
|
.I Signals
|
|
are sent either by typing special
|
|
.I control
|
|
characters on the keyboard or by using the
|
|
.I kill
|
|
or
|
|
.I stop
|
|
commands (1.8, 2.6).
|
|
.IP sort
|
|
The
|
|
.I sort
|
|
program sorts a sequence of lines in ways that can be controlled
|
|
by argument
|
|
.I flags
|
|
(1.5).
|
|
.IP source
|
|
The
|
|
.I source
|
|
command causes the shell to read commands from a specified file.
|
|
It is most useful for reading files such as
|
|
.I \&.cshrc
|
|
after changing them (2.8).
|
|
.IP "special character"
|
|
.br
|
|
See
|
|
.I metacharacters
|
|
and the
|
|
appendix to this manual.
|
|
.IP standard
|
|
We refer often to the
|
|
.I "standard input"
|
|
and
|
|
.I "standard output"
|
|
of commands.
|
|
See
|
|
.I input
|
|
and
|
|
.I output
|
|
(1.3, 3.8).
|
|
.IP status
|
|
A command normally returns a
|
|
.I status
|
|
when it finishes.
|
|
By convention a
|
|
.I status
|
|
of zero indicates that the command succeeded.
|
|
Commands may return non-zero
|
|
.I status
|
|
to indicate that some abnormal event has occurred.
|
|
The shell variable
|
|
.I status
|
|
is set to the
|
|
.I status
|
|
returned by the last command.
|
|
It is most useful in shell commmand scripts (3.6).
|
|
.IP stop
|
|
The
|
|
.I stop
|
|
command causes a
|
|
.I background
|
|
job to become
|
|
.I suspended
|
|
(2.6).
|
|
.IP string
|
|
A sequential group of characters taken together is called a
|
|
.I string \&.
|
|
.I Strings
|
|
can contain any printable characters (2.2).
|
|
.IP stty
|
|
The
|
|
.I stty
|
|
program changes certain parameters inside \s-2UNIX\s0 which determine
|
|
how your terminal is handled. See `stty (1)' for a complete description (2.6).
|
|
.IP substitution
|
|
The shell implements a number of
|
|
.I substitutions
|
|
where sequences indicated by metacharacters are replaced by other sequences.
|
|
Notable examples of this are history
|
|
.I substitution
|
|
keyed by the
|
|
metacharacter `!' and variable
|
|
.I substitution
|
|
indicated by `$'.
|
|
We also refer to
|
|
.I substitutions
|
|
as
|
|
.I expansions
|
|
(3.4).
|
|
.IP suspended
|
|
A job becomes
|
|
.I suspended
|
|
after a \s-2STOP\s0 signal is sent to it, either by typing a
|
|
.I control -z
|
|
at the terminal (for
|
|
.I foreground
|
|
jobs) or by using the
|
|
.I stop
|
|
command (for
|
|
.I background
|
|
jobs). When
|
|
.I suspended ,
|
|
a job temporarily stops running until it is restarted by either the
|
|
.I fg
|
|
or
|
|
.I bg
|
|
command (2.6).
|
|
.IP switch
|
|
The
|
|
.I switch
|
|
command of the shell allows the shell
|
|
to select one of a number of sequences of commands based on an
|
|
argument string.
|
|
It is similar to the
|
|
.I switch
|
|
statement in the language C (3.7).
|
|
.IP termination
|
|
When a command which is being executed finishes we say it undergoes
|
|
.I termination
|
|
or
|
|
.I terminates.
|
|
Commands normally terminate when they read an
|
|
.I end\f1-\fPof\f1-\fPfile
|
|
from their
|
|
.I "standard input" .
|
|
It is also possible to terminate commands by sending them
|
|
an
|
|
.I interrupt
|
|
or
|
|
.I quit
|
|
signal (1.8).
|
|
The
|
|
.I kill
|
|
program terminates specified jobs (2.6).
|
|
.IP then
|
|
The
|
|
.I then
|
|
command is part of the shell's
|
|
`if-then-else-endif' control construct used in command scripts (3.6).
|
|
.IP time
|
|
The
|
|
.I time
|
|
command can be used to measure the amount of \s-2CPU\s0
|
|
and real time consumed by a specified command as well
|
|
as the amount of disk i/o, memory utilized, and number
|
|
of page faults and swaps taken by the command (2.1, 2.8).
|
|
.IP tset
|
|
The
|
|
.I tset
|
|
program is used to set standard erase and kill characters
|
|
and to tell the system what kind of terminal you are using.
|
|
It is often invoked in a
|
|
.I \&.login
|
|
file (2.1).
|
|
.IP tty
|
|
The word
|
|
.I tty
|
|
is a historical abbreviation for `teletype' which is frequently used
|
|
in \s-2UNIX\s0 to indicate the
|
|
.I port
|
|
to which a given terminal is connected. The
|
|
.I tty
|
|
command will print the name of the
|
|
.I tty
|
|
or
|
|
.I port
|
|
to which your terminal is presently connected.
|
|
.IP unalias
|
|
The
|
|
.I unalias
|
|
command removes aliases (2.8).
|
|
.IP \s-2UNIX\s0
|
|
\s-2UNIX\s0 is an operating system on which
|
|
.I csh
|
|
runs.
|
|
\s-2UNIX\s0 provides facilities which allow
|
|
.I csh
|
|
to invoke other programs such as editors and text formatters which
|
|
you may wish to use.
|
|
.IP unset
|
|
The
|
|
.I unset
|
|
command removes the definitions of shell variables (2.2, 2.8).
|
|
.IP "variable expansion"
|
|
.br
|
|
See
|
|
.I variables
|
|
and
|
|
.I expansion
|
|
(2.2, 3.4).
|
|
.IP variables
|
|
.I Variables
|
|
in
|
|
.I csh
|
|
hold one or more strings as value.
|
|
The most common use of
|
|
.I variables
|
|
is in controlling the behavior
|
|
of the shell.
|
|
See
|
|
.I path ,
|
|
.I noclobber ,
|
|
and
|
|
.I ignoreeof
|
|
for examples.
|
|
.I Variables
|
|
such as
|
|
.I argv
|
|
are also used in writing shell programs (shell command scripts)
|
|
(2.2).
|
|
.IP verbose
|
|
The
|
|
.I verbose
|
|
shell variable can be set to cause commands to be echoed
|
|
after they are history expanded.
|
|
This is often useful in debugging shell scripts.
|
|
The
|
|
.I verbose
|
|
variable is set by the shell's
|
|
.I \-v
|
|
command line option (3.10).
|
|
.IP wc
|
|
The
|
|
.I wc
|
|
program calculates the number of characters, words, and lines in the
|
|
files whose names are given as arguments (2.6).
|
|
.IP while
|
|
The
|
|
.I while
|
|
builtin control construct is used in shell command scripts (3.7).
|
|
.IP word
|
|
A sequence of characters which forms an argument to a command is called
|
|
a
|
|
.I word .
|
|
Many characters which are neither letters, digits, `\-', `.' nor `/'
|
|
form
|
|
.I words
|
|
all by themselves even if they are not surrounded
|
|
by blanks.
|
|
Any sequence of characters may be made into a
|
|
.I word
|
|
by surrounding it
|
|
with `\'' characters
|
|
except for the characters `\'' and `!' which require special treatment
|
|
(1.1).
|
|
This process of placing special characters in
|
|
.I words
|
|
without their special meaning is called
|
|
.I quoting .
|
|
.IP "working directory"
|
|
.br
|
|
At any given time you are in one particular directory, called
|
|
your
|
|
.I "working directory" .
|
|
This directory's name is printed by the
|
|
.I pwd
|
|
command and the files listed by
|
|
.I ls
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|
are the ones in this directory.
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|
You can change
|
|
.I "working directories"
|
|
using
|
|
.I chdir .
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|
.IP write
|
|
The
|
|
.I write
|
|
command is an obsolete way of communicating with other users who are logged in to
|
|
\s-2UNIX\s0 (you have to take turns typing). If you are both using display
|
|
terminals, use \fItalk\fP(1), which is much more pleasant.
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