$NetBSD: csh.g,v 1.6 2021/12/05 04:35:38 msaitoh Exp $ Copyright (c) 1980, 1993 The Regents of the University of California. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. @(#)csh.g 8.1 (Berkeley) 6/8/93Glossary
This glossary lists the most important terms introduced in the
introduction to the
shell and gives references to sections of the shell
document for further information about them.
References of the form
`pr (1)'
indicate that the command
pr is in the \s-2UNIX\s0 User Reference manual in section 1.
You can look at an online copy of its manual page by doing
man 1 pr
References of the form (2.5)
indicate that more information can be found in section 2.5 of this
manual.
\fB. 15n
Your current directory has the name `.' as well as the name printed
by the command
pwd; see also
dirs. The current directory `.' is usually the first
component of the search path contained in the variable
path , thus commands which are in `.' are found first (2.2).
The character `.' is also used in separating
components of filenames
(1.6).
The character `.' at the beginning of a
component of a
pathname is treated specially and not matched by the
"filename expansion" metacharacters `?', `*', and `[' `]' pairs (1.6).
\fB..
Each directory has a file `..' in it which is a reference to its
parent directory.
After changing into the directory with
chdir , i.e.
chdir paper
you can return to the parent directory by doing
chdir ..
The current directory is printed by
pwd (2.7).
a.out
Compilers which create executable images create them, by default, in the
file
a.out. for historical reasons (2.3).
"absolute pathname"
A
pathname which begins with a `/' is
absolute since it specifies the
path of directories from the beginning
of the entire directory system - called the
root directory.
Pathname s which are not
absolute are called
relative (see definition of
"relative pathname" ) (1.6).
alias
An
alias specifies a shorter or different name for a \s-2UNIX\s0
command, or a transformation on a command to be performed in
the shell.
The shell has a command
alias which establishes
aliases and can print their current values.
The command
unalias is used to remove
aliases (2.4).
argument
Commands in \s-2UNIX\s0 receive a list of
argument words.
Thus the command
echo a b c
consists of the
"command name" `echo' and three
argument words `a', `b' and `c'.
The set of
arguments after the
"command name" is said to be the
"argument list" of the command (1.1).
argv
The list of arguments to a command written in the shell language
(a shell script or shell procedure) is stored in a variable called
argv within the shell.
This name is taken from the conventional name in the
C programming language (3.4).
background
Commands started without waiting for them to complete are called
background commands (2.6).
base
A filename is sometimes thought of as consisting of a
base part, before any `.' character, and an
extension - the part after
the `.'. See
filename and
extension (1.6) and basename (1).
bg
The
bg command causes a
suspended job to continue execution in the
background (2.6).
bin
A directory containing binaries of programs and shell scripts to be
executed is typically called a
bin directory.
The standard system
bin directories are `/bin' containing the most
heavily used commands and `/
usr/
bin' which contains most other user
programs.
Programs developed at UC Berkeley live in `/
usr/
ucb', while locally
written programs live in `/
usr/
local'. Games are kept in the directory
`/
usr/
games'.
You can place binaries in any directory.
If you wish to execute them often, the name of the directories
should be a
component of the variable
path . break
Break is a builtin command used to exit from loops within the control
structure of the shell (3.7).
breaksw
The
breaksw builtin command is used to exit from a
switch control structure, like a
break exits from loops (3.7).
builtin
A command executed directly by the shell is called a
builtin command.
Most commands in \s-2UNIX\s0 are not built into the shell,
but rather exist as files in
bin directories.
These commands are accessible because the directories in which
they reside are named in the
path variable.
case
A
case command is used as a label in a
switch statement in the shell's control structure, similar to that of the
language C.
Details are given in the shell documentation `csh (1)' (3.7).
cat
The
cat program catenates a list of specified files on the
"standard output" . It is usually used to look at the contents of a single file on the terminal,
to `cat a file' (1.8, 2.3).
cd
The
cd command is used to change the
"working directory" . With no arguments,
cd changes your
"working directory" to be your
home directory (2.4, 2.7).
chdir
The
chdir command is a synonym for
cd . Cd is usually used because it is easier to type.
chsh
The
chsh command is used to change the shell which you use on \s-2UNIX\s0.
By default, you use an different version of the shell
which resides in `/
bin/
sh'.
You can change your shell to `/
bin/
csh' by doing
chsh your-login-name /bin/csh
Thus I would do
chsh bill /bin/csh
It is only necessary to do this once.
The next time you log in to \s-2UNIX\s0 after doing this command,
you will be using
csh rather than the shell in `/
bin/
sh' (1.9).
cmp
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
diff , described in `diff (1)' is used.
command
A function performed by the system, either by the shell
(a builtin
command ) or by a program residing in a file in
a directory within the \s-2UNIX\s0 system, is called a
command (1.1).
"command name"
When a command is issued, it consists of a
"command name" , which is the first word of the command,
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).
"command substitution"
The replacement of a command enclosed in `\`' characters
by the text output by that command
is called
"command substitution" (4.3).
component
A part of a
pathname between `/' characters is called a
component of that
pathname . A variable
which has multiple strings as value is said to have
several
component s; each string is a
component of the variable.
continue
A builtin command which causes execution of the enclosing
foreach or
while loop to cycle prematurely.
Similar to the
continue command in the programming language C (3.6).
control-
Certain special characters, called
control 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
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
control character (e.g. `^C' for
control- c (1.8).
"core dump"
When a program terminates abnormally, the system places an image
of its current state in a file named `core'.
This
"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
Illegal instruction (core dumped)
(where `Illegal instruction' is only one of several possible
messages), you should report this to the author of the program
or a system administrator,
saving the `core' file.
cp
The
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).
csh
The name of the shell
program that this document describes.
.cshrc
The file
.cshrc in your
home directory is read by each shell as it begins execution.
It is usually used to change the setting of the variable
path and to set
alias parameters which are to take effect globally (2.1).
cwd
The
cwd variable in the shell holds the
"absolute pathname" of the current
"working directory" . It is changed by the shell whenever your current
"working directory" changes and should not be changed otherwise (2.2).
date
The
date command prints the current date and time (1.3).
debugging
Debugging 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
debugging (4.4).
default:
The label
default: is used within shell
switch statements, as it is in the C language
to label the code to be executed if none of the
case labels matches the value switched on (3.7).
\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.
detached
A command that continues running in the
background after you logout is said to be
detached . diagnostic
An error message produced by a program is often referred to as a
diagnostic . Most error messages are not written to the
"standard output" , since that is often directed away from the terminal (1.3, 1.5).
Error messsages are instead written to the
"diagnostic output" which may be directed away from the terminal, but usually is not.
Thus
diagnostics will usually appear on the terminal (2.5).
directory
A structure which contains files.
At any time you are in one particular
directory whose names can be printed by the command
pwd . The
chdir command will change you to another
directory , and make the files
in that
directory visible. The
directory in which you are when you first login is your
home directory (1.1, 2.7).
"directory stack"
The shell saves the names of previous
"working directories" in the
"directory stack" when you change your current
"working directory" via the
pushd command. The
"directory stack" can be printed by using the
dirs command, which includes your current
"working directory" as the first directory name on the left (2.7).
dirs
The
dirs command prints the shell's
"directory stack" (2.7).
du
The
du command is a program (described in `du (1)') which
prints the number of disk blocks is all directories below
and including your current
"working directory" (2.6).
echo
The
echo command prints its arguments (1.6, 3.6).
else
The
else command is part of the `if-then-else-endif' control
command construct (3.6).
endif
If an
if statement is ended with the word
then , all lines following the
if up to a line starting with the word
endif or
else are executed if the condition between parentheses after the
if is true (3.6).
\s-2EOF\s0
An
"end\f1-of\f1-file" 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
pipe receive an
"end\f1-of\f1-file" when the command sending them input completes.
Most commands terminate when they receive an
"end\f1-of\f1-file" . The shell has an option to ignore
"end\f1-of\f1-file" 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).
escape
A character `\e' used to prevent the special meaning of a metacharacter
is said to
escape the character from its special meaning.
Thus
echo \e*
will echo the character `*' while just
echo *
will echo the names of the file in the current directory.
In this example, \e
escape s `*' (1.7).
There is also a non-printing character called
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
suspended . Most systems use control-s to stop the output and control-q to start it.
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
cat /etc/passwd
The commands
finger and
grep are often used to search for information in this file.
See `finger (1)', `passwd(5)', and `grep (1)' for more details.
exit
The
exit command is used to force termination of a shell script,
and is built into the shell (3.9).
"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
"exit status" , a status of zero being considered
`normal termination'.
The
exit command can be used to force a shell command script to give a non-zero
"exit status" (3.6).
expansion
The replacement of strings in the shell input which contain metacharacters
by other strings is referred to as the process of
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'.
Expansions are also referred to as
substitutions (1.6, 3.4, 4.2).
expressions
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
expressions are those of the language
C (3.5).
extension
Filenames often consist of a
base name and an
extension separated by the character `.'.
By convention, groups of related files often share the same
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).
fg
The
"job control" command
fg is used to run a
background or
suspended job in the
foreground (1.8, 2.6).
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
pathname building. Most
filenames do not begin with the character `.', and contain
only letters and digits with perhaps a `.' separating the
base portion of the
filename from an
extension (1.6).
"filename expansion"
"Filename expansion" uses the metacharacters `*', `?' and `[' and `]'
to provide a convenient mechanism for naming files.
Using
"filename expansion" it is easy to name all the files in
the current directory, or all files which have a common
root name. Other
"filename expansion" mechanisms use the metacharacter `~' and allow
files in other users' directories to be named easily (1.6, 4.2).
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
flag options, and by convention consist of one or more letters preceded by
the character `-' (1.2).
Thus the
ls (list files) command has an option
`-s' to list the sizes of files.
This is specified
ls -s
foreach
The
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).
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
"foreground jobs" or
"running in the foreground" . This is as opposed to
background . Foreground jobs can be stopped by signals
from the terminal caused by typing different
control characters at the keyboard (1.8, 2.6).
goto
The shell has a command
goto used in shell scripts to transfer control to a given label (3.7).
grep
The
grep command searches through a list of argument files for a specified string.
Thus
grep bill /etc/passwd
will print each line in the file
"/etc/passwd" which contains the string `bill'.
Actually,
grep scans for
"regular expressions" in the sense of the editors
`ed (1)' and `ex (1)'.
Grep stands for
`globally find
"regular expression" and print' (2.4).
head
The
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
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).
Head is also used to describe the part of a
pathname before and including the last `/' character. The
tail of a
pathname is the part after the last `/'. The `:h' and `:t' modifiers allow the
head or
tail of a
pathname stored in a shell variable to be used (3.6).
history
The
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
"history list" where these commands are kept, and a
history variable which controls how large this list is (2.3).
"home directory"
Each user has a
"home directory" , which is given in your entry
in the password file,
/etc/passwd . This is the directory which you are placed in when you first login.
The
cd or
chdir command with no arguments takes you back to this directory, whose
name is recorded in the shell variable
home . You can also access the
"home directories" of other users in forming
filenames using a
"filename expansion" notation and the character `~' (1.6).
if
A conditional command within the shell, the
if command is used in shell command scripts to make decisions
about what course of action to take next (3.6).
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
set the
ignoreeof variable if you wish in your
.login file and then use the command
logout to logout.
This is useful if you sometimes accidentally type too many control-d
characters, logging yourself off
(2.2).
input
Many commands on \s-2UNIX\s0 take information from the terminal or from
files which they then act on.
This information is called
input . Commands normally read for
input from their
"standard input" which is, by default, the terminal.
This
"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
pipelines will read from the output of the previous
command in the
pipeline . The leftmost command in a
pipeline reads from the terminal if
you neither redirect its
input nor give it a filename to use as
"standard input" . Special mechanisms exist for supplying input to commands in shell
scripts (1.5, 3.8).
interrupt
An
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
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
interrupts. The shell often wakes up when you hit
interrupt because many commands
die when they receive an
interrupt (1.8, 3.9).
job
One or more commands
typed on the same input line separated by `|' or `;' characters
are run together and are called a
job . Simple commands run by themselves without any `|' or `;' characters
are the simplest
jobs. Jobs are classified as
foreground , background , or
suspended (2.6).
"job control"
The builtin functions that control the execution of
jobs are called
"job control" commands. These are
"bg, fg, stop, kill" (2.6).
"job number"
When each job
is started it is assigned a small number called a
"job number" which is printed next to the job in the output of the
jobs command. This number, preceded by a `%' character, can be used as an argument
to
"job control" commands to indicate
a specific job (2.6).
jobs
The
jobs command prints a table showing
jobs that are either running in the
background or are
suspended (2.6).
kill
A command which sends a
signal
to a job causing it to terminate (2.6).
.login
The file
.login in your
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
set commands to the shell itself (2.1).
"login shell"
The shell that is started on your terminal when you login is called
your
"login shell" . It is different from other shells which you may run (e.g. on
shell scripts)
in that it reads the
.login file before reading commands from the terminal and it reads the
.logout file after you logout
(2.1).
logout
The
logout command causes a login shell to exit.
Normally, a login shell will exit when you hit control-d
generating an
end\f1-of\f1-file, but if you have set
ignoreeof in you
.login file then this will not work and you must use
logout to log off the \s-2UNIX\s0 system (2.8).
.logout
When you log off of \s-2UNIX\s0 the shell will execute commands from
the file
.logout in your
home directory after it prints `logout'.
lpr
The command
lpr is the line printer daemon.
The standard input of
lpr spooled and printed on the \s-2UNIX\s0 line printer.
You can also give
lpr a list of filenames as arguments to be printed.
It is most common to use
lpr as the last component of a
pipeline (2.3).
ls
The
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
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).
mail
The
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.
make
The
make command is used to maintain one or more related files and to
organize functions to be performed on these files.
In many ways
make is easier to use, and more helpful than
shell command scripts (3.2).
makefile
The file containing commands for
make is called
makefile or
Makefile (3.2).
manual
The
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
manual is accessible through the
man command.
Its documentation can be obtained online via
man man
If you can't decide what manual page to look in, try the
apropos (1) command.
The supplementary documents are in subdirectories of /
usr/
doc.
metacharacter
Many characters which are neither letters nor digits have special meaning
either to the shell or to \s-2UNIX\s0.
These characters are called
metacharacters . If it is necessary to place these characters in arguments to commands
without them having their special meaning then they must be
quoted . An example of a
metacharacter is the character `>' which is used
to indicate placement of output into a file.
For the purposes of the
history mechanism,
most unquoted
metacharacters form separate words (1.4).
The appendix to this user's manual lists the
metacharacters in groups by their function.
mkdir
The
mkdir command is used to create a new directory.
modifier
Substitutions with the
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
modifier itself.
The
"command substitution" mechanism can also be used to perform modification in a similar way,
but this notation is less clear (3.6).
more
The program
more writes a file on your terminal allowing you to control how much text
is displayed at a time.
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).
noclobber
The shell has a variable
noclobber which may be set in the file
.login to prevent accidental destruction of files by the `>' output redirection
metasyntax of the shell (2.2, 2.5).
noglob
The shell variable
noglob is set to suppress the
"filename expansion" of arguments containing the metacharacters `~', `*', `?', `[' and `]' (3.6).
notify
The
notify command tells the shell to report on the termination of a specific
"background job" at the exact time it occurs as opposed to waiting
until just before the next prompt to report the termination.
The
notify variable, if set, causes the shell to always report the termination
of
background jobs exactly when they occur (2.6).
onintr
The
onintr command is built into the shell and is used to control the action
of a shell command script when an
interrupt signal is received (3.9).
output
Many commands in \s-2UNIX\s0 result in some lines of text which are
called their
output. This
output is usually placed on what is known as the
"standard output" which is normally connected to the user's terminal.
The shell has a syntax using the metacharacter `>' for redirecting
the
"standard output" of a command to a file (1.3).
Using the
pipe mechanism and the metacharacter `|' it is also possible for
the
"standard output" of one command to become the
"standard input" of another command (1.5).
Certain commands such as the line printer daemon
p do not place their results on the
"standard output" but rather in more
useful places such as on the line printer (2.3).
Similarly the
write command places its output on another user's terminal rather than its
"standard output" (2.3).
Commands also have a
"diagnostic output" where they write their error messages.
Normally these go to the terminal even if the
"standard output" has been sent to a file or another command, but it is possible
to direct error diagnostics along with
"standard output" using a special metanotation (2.5).
path
The shell has a variable
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
path variable, left to right.
Since the normal definition of the
path variable is
path (. /usr/ucb /bin /usr/bin)
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
chmod 755 script
was executed to turn this execute permission on (3.3).
If you add new commands to a directory in the
path , you should issue
the command
rehash (2.2).
pathname
A list of names, separated by `/' characters, forms a
pathname. Each
component, between successive `/' characters, names a directory
in which the next
component file resides.
Pathnames which begin with the character `/' are interpreted relative
to the
root directory in the filesystem.
Other
pathnames are interpreted relative to the current directory
as reported by
pwd. The last component of a
pathname may name a directory, but
usually names a file.
pipeline
A group of commands which are connected together, the
"standard output" of each connected to the
"standard input" of the next,
is called a
pipeline. The
pipe mechanism used to connect these commands is indicated by
the shell metacharacter `|' (1.5, 2.3).
popd
The
popd command changes the shell's
"working directory" to the directory you most recently left using the
pushd command. It returns to the directory without having to type its name,
forgetting the name of the current
"working directory" before doing so (2.7).
port
The part of a computer system to which each terminal is
connected is called a
port . Usually the system has a fixed number of
ports , some of which are connected to telephone lines
for dial-up access, and some of which are permanently
wired directly to specific terminals.
pr
The
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).
printenv
The
printenv command is used
to print the current setting of variables in the environment
(2.8).
process
An instance of a running program is called a
process (2.6).
\s-2UNIX\s0 assigns each
process a unique number when it is
started - called the
"process number" . "Process numbers" can be used to stop individual
processes using the
kill or
stop commands when the
processes are part of a detached
background job.
program
Usually synonymous with
command ; a binary file or shell command script
which performs a useful function is often
called a
program . prompt
Many programs will print a
prompt on the terminal when they expect input.
Thus the editor
`ex (1)' will print a `:' when it expects input.
The shell
prompts for input with `% ' and occasionally with `? ' when
reading commands from the terminal (1.1).
The shell has a variable
prompt which may be set to a different value to change the shell's main
prompt . This is mostly used when debugging the shell (2.8).
pushd
The
pushd command, which means `push directory', changes the shell's
"working directory" and also remembers the current
"working directory" before the change is made, allowing you to return to the same
directory via the
popd command later without retyping its name (2.7).
ps
The
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
csh you use to run the
ps command, are not normally shown in the output.
pwd
The
pwd command prints the full
pathname of the current
"working directory" . The
dirs builtin command is usually a better and faster choice.
quit
The
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).
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
quotation (1.7).
redirection
The routing of input or output from or to a file is known
as
redirection of input or output (1.3).
rehash
The
rehash command tells the shell to rebuild its internal table of which commands
are found in which directories in your
path . This is necessary when a new program is installed in one of these
directories (2.8).
"relative pathname"
A
pathname which does not begin with a `/' is called a
"relative pathname" since it is interpreted
relative to the current
"working directory" . The first
component of such a
pathname refers to some file or directory in the
"working directory" , and subsequent
components between `/' characters refer to directories below the
"working directory" . Pathnames that are not
relative are called
"absolute pathnames" (1.6).
repeat
The
repeat command iterates another command a specified number of times.
root
The directory
that is at the top of the entire directory structure is called the
root directory since it is the `root' of the entire tree structure of
directories. The name used in
pathnames to indicate the
root is `/'.
Pathnames starting with `/' are said to be
absolute since they start at the
root directory.
Root is also used as the part of a
pathname that is left after removing
the
extension . See
filename for a further explanation (1.6).
\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.
"scratch file"
Files whose names begin with a `#' are referred to as
"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).
script
Sequences of shell commands placed in a file are called shell command
scripts . It is often possible to perform simple tasks using these
scripts without writing a program in a language such as C, by
using the shell to selectively run other programs (3.3, 3.10).
set
The builtin
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
set command the behavior of the shell can be affected (2.1).
setenv
Variables in the environment `environ (5)'
can be changed by using the
setenv builtin command (2.8).
The
printenv command can be used to print the value of the variables in the environment.
shell
A
shell is a command language interpreter.
It is possible to write and run your own
shell , as
shells are no different than any other programs as far as the
system is concerned.
This manual deals with the details of one particular
shell , called
csh. "shell script"
See
script (3.3, 3.10).
signal
A
signal in \s-2UNIX\s0 is a short message that is sent to a running program
which causes something to happen to that process.
Signals are sent either by typing special
control characters on the keyboard or by using the
kill or
stop commands (1.8, 2.6).
sort
The
sort program sorts a sequence of lines in ways that can be controlled
by argument
flags (1.5).
source
The
source command causes the shell to read commands from a specified file.
It is most useful for reading files such as
.cshrc after changing them (2.8).
"special character"
See
metacharacters and the
appendix to this manual.
standard
We refer often to the
"standard input" and
"standard output" of commands.
See
input and
output (1.3, 3.8).
status
A command normally returns a
status when it finishes.
By convention a
status of zero indicates that the command succeeded.
Commands may return non-zero
status to indicate that some abnormal event has occurred.
The shell variable
status is set to the
status returned by the last command.
It is most useful in shell command scripts (3.6).
stop
The
stop command causes a
background job to become
suspended (2.6).
string
A sequential group of characters taken together is called a
string . Strings can contain any printable characters (2.2).
stty
The
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).
substitution
The shell implements a number of
substitutions where sequences indicated by metacharacters are replaced by other sequences.
Notable examples of this are history
substitution keyed by the
metacharacter `!' and variable
substitution indicated by `$'.
We also refer to
substitutions as
expansions (3.4).
suspended
A job becomes
suspended after a \s-2STOP\s0 signal is sent to it, either by typing a
control -z at the terminal (for
foreground jobs) or by using the
stop command (for
background jobs). When
suspended , a job temporarily stops running until it is restarted by either the
fg or
bg command (2.6).
switch
The
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
switch statement in the language C (3.7).
termination
When a command which is being executed finishes we say it undergoes
termination or
terminates. Commands normally terminate when they read an
end\f1-of\f1-file from their
"standard input" . It is also possible to terminate commands by sending them
an
interrupt or
quit signal (1.8).
The
kill program terminates specified jobs (2.6).
then
The
then command is part of the shell's
`if-then-else-endif' control construct used in command scripts (3.6).
time
The
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 used, and number
of page faults and swaps taken by the command (2.1, 2.8).
tset
The
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
.login file (2.1).
tty
The word
tty is a historical abbreviation for `teletype' which is frequently used
in \s-2UNIX\s0 to indicate the
port to which a given terminal is connected. The
tty command will print the name of the
tty or
port to which your terminal is presently connected.
unalias
The
unalias command removes aliases (2.8).
\s-2UNIX\s0
\s-2UNIX\s0 is an operating system on which
csh runs.
\s-2UNIX\s0 provides facilities which allow
csh to invoke other programs such as editors and text formatters which
you may wish to use.
unset
The
unset command removes the definitions of shell variables (2.2, 2.8).
"variable expansion"
See
variables and
expansion (2.2, 3.4).
variables
Variables in
csh hold one or more strings as value.
The most common use of
variables is in controlling the behavior
of the shell.
See
path , noclobber , and
ignoreeof for examples.
Variables such as
argv are also used in writing shell programs (shell command scripts)
(2.2).
verbose
The
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
verbose variable is set by the shell's
-v command line option (3.10).
wc
The
wc program calculates the number of characters, words, and lines in the
files whose names are given as arguments (2.6).
while
The
while builtin control construct is used in shell command scripts (3.7).
word
A sequence of characters which forms an argument to a command is called
a
word . Many characters which are neither letters, digits, `-', `.' nor `/'
form
words all by themselves even if they are not surrounded
by blanks.
Any sequence of characters may be made into a
word by surrounding it
with `\'' characters
except for the characters `\'' and `!' which require special treatment
(1.1).
This process of placing special characters in
words without their special meaning is called
quoting . "working directory"
At any given time you are in one particular directory, called
your
"working directory" . This directory's name is printed by the
pwd command and the files listed by
ls are the ones in this directory.
You can change
"working directories" using
chdir .
write
The
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
talk(1), which is much more pleasant.