csh(1)
NAME
csh - shell command interpreter with a C-like syntax
SYNOPSIS
csh [-bcefinstvVxX] [argument...]
DESCRIPTION
csh, the C shell, is a command interpreter with a syntax
reminiscent of the C language. It provides a number of con-
venient features for interactive use that are not available
with the Bourne shell, including filename completion, com-
mand aliasing, history substitution, job control, and a
number of built-in commands. As with the Bourne shell, the C
shell provides variable, command and filename substitution.
Initialization and Termination
When first started, the C shell normally performs commands
from the .cshrc file in your home directory, provided that
it is readable and you either own it or your real group ID
matches its group ID. If the shell is invoked with a name
that starts with `-', as when started by login(1), the shell
runs as a login shell.
If the shell is a login shell, this is the sequence of invo-
cations: First, commands in /etc/.login are executed. Next,
commands from the .cshrc file your home directory are exe-
cuted. Then the shell executes commands from the .login file
in your home directory; the same permission checks as those
for .cshrc are applied to this file. Typically, the .login
file contains commands to specify the terminal type and
environment. (For an explanation of file interpreters, see
below "Command Execution" and exec(2).)
As a login shell terminates, it performs commands from the
.logout file in your home directory; the same permission
checks as those for .cshrc are applied to this file.
Interactive Operation
After startup processing is complete, an interactive C shell
begins reading commands from the terminal, prompting with
hostname% (or hostname# for the privileged user). The shell
then repeatedly performs the following actions: a line of
command input is read and broken into words. This sequence
of words is placed on the history list and then parsed, as
described under USAGE. Finally, the shell executes each com-
mand in the current line.
Noninteractive Operation
When running noninteractively, the shell does not prompt for
input from the terminal. A noninteractive C shell can exe-
cute a command supplied as an argument on its command line,
or interpret commands from a file, also known as a script.
OPTIONS
The following options are supported:
-b Forced a "break" from option processing. Subsequent
command line arguments are not interpreted as C shell
options. This allows the passing of options to a
script without confusion. The shell does not run set-
user-ID or set-group-ID scripts unless this option is
present.
-c Executes the first argument, which must be present.
Remaining arguments are placed in argv, the argument-
list variable, and passed directly to csh.
-e Exits if a command terminates abnormally or yields a
nonzero exit status.
-f Fast start. Reads neither the .cshrc file, nor the
.login file (if a login shell) upon startup.
-i Forced interactive. Prompts for command line input,
even if the standard input does not appear to be a
terminal (character-special device).
-n Parses (interprets), but does not execute commands.
This option can be used to check C shell scripts for
syntax errors.
-s Takes commands from the standard input.
-t Reads and executes a single command line. A `\'
(backslash) can be used to escape each newline for
continuation of the command line onto subsequent input
lines.
-v Verbose. Sets the verbose predefined variable. Command
input is echoed after history substitution, but before
other substitutions and before execution.
-V Sets verbose before reading .cshrc.
-x Echo. Sets the echo variable. Echoes commands after
all substitutions and just before execution.
-X Sets echo before reading .cshrc.
Except with the options -c, -i, -s, or -t, the first nonop-
tion argument is taken to be the name of a command or
script. It is passed as argument zero, and subsequent argu-
ments are added to the argument list for that command or
script.
USAGE
Filename Completion
When enabled by setting the variable filec, an interactive C
shell can complete a partially typed filename or user name.
When an unambiguous partial filename is followed by an ESC
character on the terminal input line, the shell fills in the
remaining characters of a matching filename from the working
directory.
If a partial filename is followed by the EOF character (usu-
ally typed as Control-d), the shell lists all filenames that
match. It then prompts once again, supplying the incomplete
command line typed in so far.
When the last (partial) word begins with a tilde (~), the
shell attempts completion with a user name, rather than a
file in the working directory.
The terminal bell signals errors or multiple matches. This
bell signal can be inhibited by setting the variable nobeep.
You can exclude files with certain suffixes by listing those
suffixes in the variable fignore. If, however, the only pos-
sible completion includes a suffix in the list, it is not
ignored. fignore does not affect the listing of filenames by
the EOF character.
Lexical Structure
The shell splits input lines into words at space and tab
characters, except as noted below. The characters &, |, ;,
<, >, (, and ) form separate words; if paired, the pairs
form single words. These shell metacharacters can be made
part of other words, and their special meaning can be
suppressed by preceding them with a `\' (backslash). A new-
line preceded by a \ is equivalent to a space character.
In addition, a string enclosed in matched pairs of single-
quotes ('), double-quotes ("), or backquotes (`), forms a
partial word. Metacharacters in such a string, including any
space or tab characters, do not form separate words. Within
pairs of backquote (`) or double-quote (") characters, a
newline preceded by a `\' (backslash) gives a true newline
character. Additional functions of each type of quote are
described, below, under Variable Substitution, Command Sub-
stitution, and Filename Substitution.
When the shell's input is not a terminal, the character #
introduces a comment that continues to the end of the input
line. Its special meaning is suppressed when preceded by a \
or enclosed in matching quotes.
Command Line Parsing
A simple command is composed of a sequence of words. The
first word (that is not part of an I/O redirection) speci-
fies the command to be executed. A simple command, or a set
of simple commands separated by | or |& characters, forms a
pipeline. With |, the standard output of the preceding com-
mand is redirected to the standard input of the command that
follows. With |&, both the standard error and the standard
output are redirected through the pipeline.
Pipelines can be separated by semicolons (;), in which case
they are executed sequentially. Pipelines that are separated
by && or || form conditional sequences in which the execu-
tion of pipelines on the right depends upon the success or
failure, respectively, of the pipeline on the left.
A pipeline or sequence can be enclosed within parentheses
`()' to form a simple command that can be a component in a
pipeline or sequence.
A sequence of pipelines can be executed asynchronously or
"in the background" by appending an `&'; rather than waiting
for the sequence to finish before issuing a prompt, the
shell displays the job number (see Job Control, below) and
associated process IDs and prompts immediately.
History Substitution
History substitution allows you to use words from previous
command lines in the command line you are typing. This sim-
plifies spelling corrections and the repetition of compli-
cated commands or arguments. Command lines are saved in the
history list, the size of which is controlled by the history
variable. The most recent command is retained in any case. A
history substitution begins with a ! (although you can
change this with the histchars variable) and may occur any-
where on the command line; history substitutions do not
nest. The ! can be escaped with \ to suppress its special
meaning.
Input lines containing history substitutions are echoed on
the terminal after being expanded, but before any other sub-
stitutions take place or the command gets executed.
Event Designators
An event designator is a reference to a command line entry
in the history list.
! Start a history substitution, except when followed by
a space character, tab, newline, = or (.
!! Refer to the previous command. By itself, this substi-
tution repeats the previous command.
!n Refer to command line n.
!-n Refer to the current command line minus n.
!str Refer to the most recent command starting with str.
!?str?
Refer to the most recent command containing str.
!?str? additional
Refer to the most recent command containing str and
append additional to that referenced command.
!{command} additional
Refer to the most recent command beginning with com-
mand and append additional to that referenced command.
^previous_word^replacement^
Repeat the previous command line replacing the string
previous_word with the string replacement. This is
equivalent to the history substitution:
!:s/previous_word/replacement/.
To re-execute a specific previous command AND make
such a substitution, say, re-executing command #6,
!:6s/previous_word/replacement/.
Word Designators
A `:' (colon) separates the event specification from the
word designator. It can be omitted if the word designator
begins with a ^, $, *, - or %. If the word is to be selected
from the previous command, the second ! character can be
omitted from the event specification. For instance, !!:1 and
!:1 both refer to the first word of the previous command,
while !!$ and !$ both refer to the last word in the previous
command. Word designators include:
# The entire command line typed so far.
0 The first input word (command).
n The n'th argument.
^ The first argument, that is, 1.
$ The last argument.
% The word matched by the ?s search.
x-y A range of words; -y abbreviates 0-y.
* All the arguments, or a null value if there is just
one word in the event.
x* Abbreviates x-$.
x- Like x* but omitting word $.
Modifiers
After the optional word designator, you can add one of the
following modifiers, preceded by a :.
h Remove a trailing pathname component, leaving the
head.
r Remove a trailing suffix of the form `.xxx', leaving
the basename.
e Remove all but the suffix, leaving the Extension.
s/l/r/
Substitute r for l.
t Remove all leading pathname components, leaving the
tail.
& Repeat the previous substitution.
g Apply the change to the first occurrence of a match in
each word, by prefixing the above (for example, g&).
p Print the new command but do not execute it.
q Quote the substituted words, escaping further substi-
tutions.
x Like q, but break into words at each space character,
tab or newline.
Unless preceded by a g, the modification is applied only to
the first string that matches l; an error results if no
string matches.
The left-hand side of substitutions are not regular expres-
sions, but character strings. Any character can be used as
the delimiter in place of /. A backslash quotes the delim-
iter character. The character &, in the right hand side, is
replaced by the text from the left-hand-side. The & can be
quoted with a backslash. A null l uses the previous string
either from a l or from a contextual scan string s from !?s.
You can omit the rightmost delimiter if a newline
immediately follows r; the rightmost ? in a context scan can
similarly be omitted.
Without an event specification, a history reference refers
either to the previous command, or to a previous history
reference on the command line (if any).
Quick Substitution
^l^r^ This is equivalent to the history substitution:
!:s/l/r/.
Aliases
The C shell maintains a list of aliases that you can create,
display, and modify using the alias and unalias commands.
The shell checks the first word in each command to see if it
matches the name of an existing alias. If it does, the com-
mand is reprocessed with the alias definition replacing its
name; the history substitution mechanism is made available
as though that command were the previous input line. This
allows history substitutions, escaped with a backslash in
the definition, to be replaced with actual command line
arguments when the alias is used. If no history substitution
is called for, the arguments remain unchanged.
Aliases can be nested. That is, an alias definition can con-
tain the name of another alias. Nested aliases are expanded
before any history substitutions is applied. This is useful
in pipelines such as
alias lm 'ls -l \!* | more'
which when called, pipes the output of ls(1) through
more(1).
Except for the first word, the name of the alias may not
appear in its definition, nor in any alias referred to by
its definition. Such loops are detected, and cause an error
message.
I/O Redirection
The following metacharacters indicate that the subsequent
word is the name of a file to which the command's standard
input, standard output, or standard error is redirected;
this word is variable, command, and filename expanded
separately from the rest of the command.
< Redirect the standard input.
<<word
Read the standard input, up to a line that is
identical with word, and place the resulting lines in
a temporary file. Unless word is escaped or quoted,
variable and command substitutions are performed on
these lines. Then, the pipeline is invoked with the
temporary file as its standard input. word is not sub-
jected to variable, filename, or command substitution,
and each line is compared to it before any substitu-
tions are performed by the shell.
> >! >& >&!
Redirect the standard output to a file. If the file
does not exist, it is created. If it does exist, it is
overwritten; its previous contents are lost.
When set, the variable noclobber prevents destruction
of existing files. It also prevents redirection to
terminals and /dev/null, unless one of the ! forms is
used. The & forms redirect both standard output and
the standard error (diagnostic output) to the file.
>> >>& >>! >>&!
Append the standard output. Like >, but places output
at the end of the file rather than overwriting it. If
noclobber is set, it is an error for the file not to
exist, unless one of the ! forms is used. The & forms
append both the standard error and standard output to
the file.
Variable Substitution
The C shell maintains a set of variables, each of which is
composed of a name and a value. A variable name consists of
up to 20 letters and digits, and starts with a letter (the
underscore is considered a letter). A variable's value is a
space-separated list of zero or more words.
To refer to a variable's value, precede its name with a `$'.
Certain references (described below) can be used to select
specific words from the value, or to display other informa-
tion about the variable. Braces can be used to insulate the
reference from other characters in an input-line word.
Variable substitution takes place after the input line is
analyzed, aliases are resolved, and I/O redirections are
applied. Exceptions to this are variable references in I/O
redirections (substituted at the time the redirection is
made), and backquoted strings (see Command Substitution).
Variable substitution can be suppressed by preceding the $
with a \, except within double-quotes where it always
occurs. Variable substitution is suppressed inside of
single-quotes. A $ is escaped if followed by a space charac-
ter, tab or newline.
Variables can be created, displayed, or destroyed using the
set and unset commands. Some variables are maintained or
used by the shell. For instance, the argv variable contains
an image of the shell's argument list. Of the variables used
by the shell, a number are toggles; the shell does not care
what their value is, only whether they are set or not.
Numerical values can be operated on as numbers (as with the
@ built-in command). With numeric operations, an empty value
is considered to be zero. The second and subsequent words of
multiword values are ignored. For instance, when the verbose
variable is set to any value (including an empty value),
command input is echoed on the terminal.
Command and filename substitution is subsequently applied to
the words that result from the variable substitution, except
when suppressed by double-quotes, when noglob is set
(suppressing filename substitution), or when the reference
is quoted with the :q modifier. Within double-quotes, a
reference is expanded to form (a portion of) a quoted
string; multiword values are expanded to a string with
embedded space characters. When the :q modifier is applied
to the reference, it is expanded to a list of space-
separated words, each of which is quoted to prevent subse-
quent command or filename substitutions.
Except as noted below, it is an error to refer to a variable
that is not set.
$var
${var}
These are replaced by words from the value of var,
each separated by a space character. If var is an
environment variable, its value is returned (but `:'
modifiers and the other forms given below are not
available).
$var[index]
${var[index]}
These select only the indicated words from the value
of var. Variable substitution is applied to index,
which may consist of (or result in) a either single
number, two numbers separated by a `-', or an aster-
isk. Words are indexed starting from 1; a `*' selects
all words. If the first number of a range is omitted
(as with $argv[-2]), it defaults to 1. If the last
number of a range is omitted (as with $argv[1-]), it
defaults to $#var (the word count). It is not an error
for a range to be empty if the second argument is
omitted (or within range).
$#name
${#name}
These give the number of words in the variable.
$0 This substitutes the name of the file from which com-
mand input is being read except for setuid shell
scripts. An error occurs if the name is not known.
$n
${n} Equivalent to $argv[n].
$* Equivalent to $argv[*].
The modifiers :e, :h, :q, :r, :t, and :x can be applied (see
History Substitution), as can :gh, :gt, and :gr. If {}
(braces) are used, then the modifiers must appear within the
braces. The current implementation allows only one such
modifier per expansion.
The following references may not be modified with : modif-
iers.
$?var
${?var}
Substitutes the string 1 if var is set or 0 if it is
not set.
$?0 Substitutes 1 if the current input filename is known
or 0 if it is not.
$$ Substitutes the process number of the (parent) shell.
$< Substitutes a line from the standard input, with no
further interpretation thereafter. It can be used to
read from the keyboard in a C shell script.
Command and Filename Substitutions
Command and filename substitutions are applied selectively
to the arguments of built-in commands. Portions of expres-
sions that are not evaluated are not expanded. For non-
built-in commands, filename expansion of the command name is
done separately from that of the argument list; expansion
occurs in a subshell, after I/O redirection is performed.
Command Substitution
A command enclosed by backquotes (`...`) is performed by a
subshell. Its standard output is broken into separate words
at each space character, tab and newline; null words are
discarded. This text replaces the backquoted string on the
current command line. Within double-quotes, only newline
characters force new words; space and tab characters are
preserved. However, a final newline is ignored. It is there-
fore possible for a command substitution to yield a partial
word.
Filename Substitution
Unquoted words containing any of the characters *, ?, [ or
{, or that begin with ~, are expanded (also known as glob-
bing) to an alphabetically sorted list of filenames, as fol-
lows:
* Match any (zero or more) characters.
? Match any single character.
[...] Match any single character in the enclosed list(s) or
range(s). A list is a string of characters. A range
is two characters separated by a dash (-), and
includes all the characters in between in the ASCII
collating sequence (see ascii(5)).
{ str, str, ... }
Expand to each string (or filename-matching pattern)
in the comma-separated list. Unlike the pattern-
matching expressions above, the expansion of this con-
struct is not sorted. For instance, {b,a} expands to
`b' `a', (not `a' `b'). As special cases, the charac-
ters { and }, along with the string {}, are passed
undisturbed.
~[user]
Your home directory, as indicated by the value of the
variable home, or that of user, as indicated by the
password entry for user.
Only the patterns *, ? and [...] imply pattern matching; an
error results if no filename matches a pattern that contains
them. The `.' (dot character), when it is the first charac-
ter in a filename or pathname component, must be matched
explicitly. The / (slash) must also be matched explicitly.
Expressions and Operators
A number of C shell built-in commands accept expressions, in
which the operators are similar to those of C and have the
same precedence. These expressions typically appear in the
@, exit, if, set and while commands, and are often used to
regulate the flow of control for executing commands. Com-
ponents of an expression are separated by white space.
Null or missing values are considered 0. The result of all
expressions is a string, which may represent decimal
numbers.
The following C shell operators are grouped in order of pre-
cedence:
(...) grouping
>~ one's complement
! logical negation
* / %
multiplication, division, remainder. These are right
associative, which can lead to unexpected results.
Combinations should be grouped explicitly with
parentheses.
+ - addition, subtraction (also right associative)
<< >>
bitwise shift left, bitwise shift right
< > <= >=
less than, greater than, less than or equal to,
greater than or equal to
== != =~ !~
equal to, not equal to, filename-substitution pattern
match (described below), filename-substitution pattern
mismatch
& bitwise AND
^ bitwise XOR (exclusive or)
| bitwise inclusive OR
&& logical AND
|| logical OR
The operators: ==, !=, =~, and !~ compare their arguments as
strings; other operators use numbers. The operators =~ and
!~ each check whether or not a string to the left matches a
filename substitution pattern on the right. This reduces the
need for switch statements when pattern-matching between
strings is all that is required.
Also available are file inquiries:
-r filename
Return true, or 1 if the user has read access.
Otherwise it returns false, or 0.
-w filename
True if the user has write access.
-x filename
True if the user has execute permission (or search
permission on a directory).
-e filename
True if filename exists.
-o filename
True if the user owns filename.
-z filename
True if filename is of zero length (empty).
-f filename
True if filename is a plain file.
-d filename
True if filename is a directory.
If filename does not exist or is inaccessible, then all
inquiries return false.
An inquiry as to the success of a command is also available:
{ command }
If command runs successfully, the expression evaluates
to true, 1. Otherwise, it evaluates to false, 0. Note:
Conversely, command itself typically returns 0 when it
runs successfully, or some other value if it
encounters a problem. If you want to get at the status
directly, use the value of the status variable rather
than this expression.
Control Flow
The shell contains a number of commands to regulate the flow
of control in scripts and within limits, from the terminal.
These commands operate by forcing the shell either to reread
input (to loop), or to skip input under certain conditions
(to branch).
Each occurrence of a foreach, switch, while, if...then and
else built-in command must appear as the first word on its
own input line.
If the shell's input is not seekable and a loop is being
read, that input is buffered. The shell performs seeks
within the internal buffer to accomplish the rereading
implied by the loop. (To the extent that this allows, back-
ward goto commands will succeed on nonseekable inputs.)
Command Execution
If the command is a C shell built-in command, the shell exe-
cutes it directly. Otherwise, the shell searches for a file
by that name with execute access. If the command name con-
tains a /, the shell takes it as a pathname, and searches
for it. If the command name does not contain a /, the shell
attempts to resolve it to a pathname, searching each direc-
tory in the path variable for the command. To speed the
search, the shell uses its hash table (see the rehash
built-in command) to eliminate directories that have no
applicable files. This hashing can be disabled with the -c
or -t, options, or the unhash built-in command.
As a special case, if there is no / in the name of the
script and there is an alias for the word shell, the expan-
sion of the shell alias is prepended (without modification)
to the command line. The system attempts to execute the
first word of this special (late-occurring) alias, which
should be a full pathname. Remaining words of the alias's
definition, along with the text of the input line, are
treated as arguments.
When a pathname is found that has proper execute permis-
sions, the shell forks a new process and passes it, along
with its arguments, to the kernel using the execve() system
call (see exec(2)). The kernel then attempts to overlay the
new process with the desired program. If the file is an exe-
cutable binary (in a.out(4) format) the kernel succeeds and
begins executing the new process. If the file is a text file
and the first line begins with #!, the next word is taken to
be the pathname of a shell (or command) to interpret that
script. Subsequent words on the first line are taken as
options for that shell. The kernel invokes (overlays) the
indicated shell, using the name of the script as an argu-
ment.
If neither of the above conditions holds, the kernel cannot
overlay the file and the execve() call fails (see exec(2)).
The C shell then attempts to execute the file by spawning a
new shell, as follows:
o If the first character of the file is a #, a C shell
is invoked.
o Otherwise, a Bourne shell is invoked.
Signal Handling
The shell normally ignores QUIT signals. Background jobs are
immune to signals generated from the keyboard, including
hangups (HUP). Other signals have the values that the C
shell inherited from its environment. The shell's handling
of interrupt and terminate signals within scripts can be
controlled by the onintr built-in command. Login shells
catch the TERM signal. Otherwise, this signal is passed on
to child processes. In no case are interrupts allowed when a
login shell is reading the .logout file.
Job Control
The shell associates a numbered job with each command
sequence to keep track of those commands that are running in
the background or have been stopped with TSTP signals (typi-
cally Control-z). When a command or command sequence (semi-
colon separated list) is started in the background using the
& metacharacter, the shell displays a line with the job
number in brackets and a list of associated process numbers:
[1] 1234
To see the current list of jobs, use the jobs built-in com-
mand. The job most recently stopped (or put into the back-
ground if none are stopped) is referred to as the current
job and is indicated with a `+'. The previous job is indi-
cated with a `-'. When the current job is terminated or
moved to the foreground, this job takes its place (becomes
the new current job).
To manipulate jobs, refer to the bg, fg, kill, stop, and %
built-in commands.
A reference to a job begins with a `%'. By itself, the
percent-sign refers to the current job.
% %+ %%
The current job.
%- The previous job.
%j Refer to job j as in: `kill -9 %j'. j can be a job
number, or a string that uniquely specifies the com-
mand line by which it was started; `fg %vi' might
bring a stopped vi job to the foreground, for
instance.
%?string
Specify the job for which the command line uniquely
contains string.
A job running in the background stops when it attempts to
read from the terminal. Background jobs can normally produce
output, but this can be suppressed using the `stty tostop'
command.
Status Reporting
While running interactively, the shell tracks the status of
each job and reports whenever the job finishes or becomes
blocked. It normally displays a message to this effect as it
issues a prompt, in order to avoid disturbing the appearance
of your input. When set, the notify variable indicates that
the shell is to report status changes immediately. By
default, the notify command marks the current process; after
starting a background job, type notify to mark it.
Commands
Built-in commands are executed within the C shell. If a
built-in command occurs as any component of a pipeline
except the last, it is executed in a subshell.
: Null command. This command is interpreted, but per-
forms no action.
alias [ name [ def ] ]
Assign def to the alias name. def is a list of words
that may contain escaped history-substitution metasyn-
tax. name is not allowed to be alias or unalias. If
def is omitted, the current definition for the alias
name is displayed. If both name and def are omitted,
all aliases are displayed with their definitions.
bg [ %job ... ]
Run the current or specified jobs in the background.
break Resume execution after the end of the nearest enclos-
ing foreach or while loop. The remaining commands on
the current line are executed. This allows multilevel
breaks to be written as a list of break commands, all
on one line.
breaksw
Break from a switch, resuming after the endsw.
case label:
A label in a switch statement.
cd [dir ]
chdir [dir ]
Change the shell's working directory to directory dir.
If no argument is given, change to the home directory
of the user. If dir is a relative pathname not found
in the current directory, check for it in those direc-
tories listed in the cdpath variable. If dir is the
name of a shell variable whose value starts with a /,
change to the directory named by that value.
continue
Continue execution of the next iteration of the
nearest enclosing while or foreach loop.
default:
Labels the default case in a switch statement. The
default should come after all case labels. Any remain-
ing commands on the command line are first executed.
dirs [-l]
Print the directory stack, most recent to the left.
The first directory shown is the current directory.
With the -l argument, produce an unabbreviated prin-
tout; use of the ~ notation is suppressed.
echo [-n] list
The words in list are written to the shell's standard
output, separated by space characters. The output is
terminated with a newline unless the -n option is
used. csh will, by default, invoke its built-in echo,
if echo is called without the full pathname of a Unix
command, regardless of the configuration of your PATH
(see echo(1)).
eval argument...
Reads the arguments as input to the shell and executes
the resulting command(s). This is usually used to exe-
cute commands generated as the result of command or
variable substitution. See tset(1B) for an example of
how to use eval.
exec command
Execute command in place of the current shell, which
terminates.
exit [(expr)]
The calling shell or shell script exits, either with
the value of the status variable or with the value
specified by the expression expr.
fg [%job ]
Bring the current or specified job into the fore-
ground.
foreach var (wordlist)
...
end The variable var is successively set to each member of
wordlist. The sequence of commands between this com-
mand and the matching end is executed for each new
value of var. Both foreach and end must appear alone
on separate lines.
The built-in command continue may be used to terminate
the execution of the current iteration of the loop and
the built-in command break may be used to terminate
execution of the foreach command. When this command is
read from the terminal, the loop is read once prompt-
ing with ? before any statements in the loop are exe-
cuted.
glob wordlist
Perform filename expansion on wordlist. Like echo, but
no \ escapes are recognized. Words are delimited by
NULL characters in the output.
goto label
The specified label is a filename and a command
expanded to yield a label. The shell rewinds its input
as much as possible and searches for a line of the
form label: possibly preceded by space or tab charac-
ters. Execution continues after the indicated line. It
is an error to jump to a label that occurs between a
while or for built-in command and its corresponding
end.
hashstat
Print a statistics line indicating how effective the
internal hash table for the path variable has been at
locating commands (and avoiding execs). An exec is
attempted for each component of the path where the
hash function indicates a possible hit and in each
component that does not begin with a `/'. These
statistics only reflect the effectiveness of the path
variable, not the cdpath variable.
history [-hr] [ n ]
Display the history list; if n is given, display only
the n most recent events.
-r Reverse the order of printout to be most recent
first rather than oldest first.
-h Display the history list without leading
numbers. This is used to produce files suitable
for sourcing using the -h option to source.
if (expr )command
If the specified expression evaluates to true, the
single command with arguments is executed. Variable
substitution on command happens early, at the same
time it does for the rest of the if command. command
must be a simple command, not a pipeline, a command
list, or a parenthesized command list. Note: I/O
redirection occurs even if expr is false, when command
is not executed (this is a bug).
if (expr) then
...
else if (expr2) then
...
else
...
endif If expr is true, commands up to the first else are
executed. Otherwise, if expr2 is true, the commands
between the else if and the second else are executed.
Otherwise, commands between the else and the endif are
executed. Any number of else if pairs are allowed, but
only one else. Only one endif is needed, but it is
required. The words else and endif must be the first
nonwhite characters on a line. The if must appear
alone on its input line or after an else.
jobs [-l]
List the active jobs under job control.
-l List process IDs, in addition to the normal
information.
kill [ -sig ] [ pid ] [ %job ] ...
kill -l
Send the TERM (terminate) signal, by default, or the
signal specified, to the specified process ID, the job
indicated, or the current job. Signals are either
given by number or by name. There is no default. Typ-
ing kill does not send a signal to the current job. If
the signal being sent is TERM (terminate) or HUP
(hangup), then the job or process is sent a CONT (con-
tinue) signal as well.
-l List the signal names that can be sent.
limit [-h] [resource [max-use ] ]
Limit the consumption by the current process or any
process it spawns, each not to exceed max-use on the
specified resource. If max-use is omitted, print the
current limit. If resource is omitted, display all
limits. Run the sysdef(1M) command to obtain the max-
imum possible limits for your system. The values
reported are in hexadecimal, but can be translated
into decimal numbers using the bc(1) command.
-h Use hard limits instead of the current limits. Hard
limits impose a ceiling on the values of the current
limits. Only the privileged user may raise the hard
limits.
resource is one of:
cputime
Maximum CPU seconds per process.
filesize
Largest single file allowed. Limited to the size of
the filesystem. (See df(1M)).
datasize (heapsize)
Maximum data size (including stack) for the process.
This is the size of your virtual memory See swap(1M).
stacksize
Maximum stack size for the process. See swap(1M).
coredumpsize
Maximum size of a core dump (file). This limited to
the size of the filesystem.
descriptors
Maximum number of file descriptors. Run sysdef().
memorysize
Maximum size of virtual memory.
max-use is a number, with an optional scaling factor, as
follows:
nh Hours (for cputime).
nk n kilobytes. This is the default for all but cputime.
nm n megabytes or minutes (for cputime).
mm:ss Minutes and seconds (for cputime).
Example of limit: to limit the size of a core file dump to
0 Megabytes, type the following:
limit coredumpsize 0M
login [username| -p ]
Terminate a login shell and invoke login(1). The
.logout file is not processed. If username is omitted,
login prompts for the name of a user.
-p Preserve the current environment (variables).
logout
Terminate a login shell.
nice [+n |-n ] [command ]
Increment the process priority value for the shell or
for command by n. The higher the priority value, the
lower the priority of a process, and the slower it
runs. When given, command is always run in a subshell,
and the restrictions placed on commands in simple if
commands apply. If command is omitted, nice increments
the value for the current shell. If no increment is
specified, nice sets the process priority value to 4.
The range of process priority values is from -20 to
20. Values of n outside this range set the value to
the lower, or to the higher boundary, respectively.
+n Increment the process priority value by n.
-n Decrement by n. This argument can be used only
by the privileged user.
nohup [command ]
Run command with HUPs ignored. With no arguments,
ignore HUPs throughout the remainder of a script. When
given, command is always run in a subshell, and the
restrictions placed on commands in simple if state-
ments apply. All processes detached with & are effec-
tively nohup'd.
notify [%job] ...
Notify the user asynchronously when the status of the
current job or specified jobs changes.
onintr [-| label]
Control the action of the shell on interrupts. With no
arguments, onintr restores the default action of the
shell on interrupts. (The shell terminates shell
scripts and returns to the terminal command input
level). With the - argument, the shell ignores all
interrupts. With a label argument, the shell executes
a goto label when an interrupt is received or a child
process terminates because it was interrupted.
popd [+n ]
Pop the directory stack and cd to the new top direc-
tory. The elements of the directory stack are numbered
from 0 starting at the top.
+n Discard the n'th entry in the stack.
pushd [+n |dir]
Push a directory onto the directory stack. With no
arguments, exchange the top two elements.
+n Rotate the n'th entry to the top of the stack
and cd to it.
dir Push the current working directory onto the
stack and change to dir.
rehash
Recompute the internal hash table of the contents of
directories listed in the path variable to account for
new commands added. Recompute the internal hash table
of the contents of directories listed in the cdpath
variable to account for new directories added.
repeat count command
Repeat command count times. command is subject to the
same restrictions as with the one-line if statement.
set [var [= value ] ]
set var[n] = word
With no arguments, set displays the values of all
shell variables. Multiword values are displayed as a
parenthesized list. With the var argument alone, set
assigns an empty (null) value to the variable var.
With arguments of the form var = value set assigns
value to var, where value is one of:
word A single word (or quoted string).
(wordlist)
A space-separated list of words enclosed in
parentheses.
Values are command and filename expanded before being
assigned. The form set var[n] = word replaces the n'th
word in a multiword value with word.
setenv [VAR [word ] ]
With no arguments, setenv displays all environment
variables. With the VAR argument, setenv sets the
environment variable VAR to have an empty (null)
value. (By convention, environment variables are nor-
mally given upper-case names.) With both VAR and word
arguments, setenv sets the environment variable NAME
to the value word, which must be either a single word
or a quoted string. The most commonly used environment
variables, USER, TERM, and PATH, are automatically
imported to and exported from the csh variables user,
term, and path. There is no need to use setenv for
these. In addition, the shell sets the PWD environment
variable from the csh variable cwd whenever the latter
changes.
The environment variables LC_CTYPE, LC_MESSAGES,
LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY take
immediate effect when changed within the C shell.
If any of the LC_* variables (LC_CTYPE, LC_MESSAGES,
LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY)
(see environ(5)) are not set in the environment, the
operational behavior of csh for each corresponding
locale category is determined by the value of the LANG
environment variable. If LC_ALL is set, its contents
are used to override both the LANG and the other LC_*
variables. If none of the above variables is set in
the environment, the "C" (U.S. style) locale deter-
mines how csh behaves.
LC_CTYPE
Determines how csh handles characters. When
LC_CTYPE is set to a valid value, csh can
display and handle text and filenames containing
valid characters for that locale.
LC_MESSAGES
Determines how diagnostic and informative mes-
sages are presented. This includes the language
and style of the messages and the correct form
of affirmative and negative responses. In the
"C" locale, the messages are presented in the
default form found in the program itself (in
most cases, U.S./English).
LC_NUMERIC
Determines the value of the radix character
(decimal point (".") in the "C" locale) and
thousand separator (empty string ("") in the "C"
locale).
shift [variable ]
The components of argv, or variable, if supplied, are
shifted to the left, discarding the first component.
It is an error for the variable not to be set or to
have a null value.
source [-h] name
Reads commands from name. source commands may be
nested, but if they are nested too deeply the shell
may run out of file descriptors. An error in a sourced
file at any level terminates all nested source com-
mands.
-h Place commands from the file name on the history
list without executing them.
stop %jobid ...
Stop the current or specified background job.
stop pid ...
Stop the specified process, pid. (see ps(1)).
suspend
Stop the shell in its tracks, much as if it had been
sent a stop signal with ^Z. This is most often used to
stop shells started by su.
switch (string)
case label:
...
breaksw
...
default:
...
breaksw
endsw Each label is successively matched, against the speci-
fied string, which is first command and filename
expanded. The file metacharacters *, ? and [...] may
be used in the case labels, which are variable
expanded. If none of the labels match before a
"default" label is found, execution begins after the
default label. Each case statement and the default
statement must appear at the beginning of a line. The
command breaksw continues execution after the endsw.
Otherwise control falls through subsequent case and
default statements as with C. If no label matches and
there is no default, execution continues after the
endsw.
time [command ]
With no argument, print a summary of time used by this
C shell and its children. With an optional command,
execute command and print a summary of the time it
uses. As of this writing, the time built-in command
does NOT compute the last 6 fields of output, render-
ing the output to erroneously report the value "0" for
these fields.
example %time ls -R
9.0u 11.0s 3:32 10% 0+0k 0+0io 0pf+0w
(See below the "Environment Variables and Predefined
Shell Variables" sub-section on the time variable.)
umask [value ]
Display the file creation mask. With value, set the
file creation mask. With value given in octal, the
user can turn off any bits, but cannot turn on bits to
allow new permissions. Common values include 077, res-
tricting all permissions from everyone else; 002, giv-
ing complete access to the group, and read (and direc-
tory search) access to others; or 022, giving read
(and directory search) but not write permission to the
group and others.
unalias pattern
Discard aliases that match (filename substitution)
pattern. All aliases are removed by `unalias *'.
unhash
Disable the internal hash tables for the path and
cdpath variables.
unlimit [-h] [resource ]
Remove a limitation on resource. If no resource is
specified, then all resource limitations are removed.
See the description of the limit command for the list
of resource names.
-h Remove corresponding hard limits. Only the
privileged user may do this.
unset pattern
Remove variables whose names match (filename substitu-
tion) pattern. All variables are removed by `unset *';
this has noticeably distasteful side effects.
unsetenv variable
Remove variable from the environment. As with unset,
pattern matching is not performed.
wait Wait for background jobs to finish (or for an inter-
rupt) before prompting.
while (expr)
...
end While expr is true (evaluates to nonzero), repeat com-
mands between the while and the matching end state-
ment. break and continue may be used to terminate or
continue the loop prematurely. The while and end must
appear alone on their input lines. If the shell's
input is a terminal, it prompts for commands with a
question-mark until the end command is entered and
then performs the commands in the loop.
% [job ] [&]
Bring the current or indicated job to the foreground.
With the ampersand, continue running job in the back-
ground.
@ [var =expr]
@ [var[n]=expr]
With no arguments, display the values for all shell
variables. With arguments, set the variable var, or
the n'th word in the value of var, to the value that
expr evaluates to. (If [n] is supplied, both var and
its n'th component must already exist.)
If the expression contains the characters >, <, &, or
|, then at least this part of expr must be placed
within parentheses.
The operators *=, +=, and so forth, are available as
in C. The space separating the name from the assign-
ment operator is optional. Spaces are, however,
mandatory in separating components of expr that would
otherwise be single words.
Special postfix operators, ++ and --, increment or
decrement name, respectively.
Environment Variables and Predefined Shell Variables
Unlike the Bourne shell, the C shell maintains a distinction
between environment variables, which are automatically
exported to processes it invokes, and shell variables, which
are not. Both types of variables are treated similarly under
variable substitution. The shell sets the variables argv,
cwd, home, path, prompt, shell, and status upon initializa-
tion. The shell copies the environment variable USER into
the shell variable user, TERM into term, and HOME into home,
and copies each back into the respective environment vari-
able whenever the shell variables are reset. PATH and path
are similarly handled. You need only set path once in the
.cshrc or .login file. The environment variable PWD is set
from cwd whenever the latter changes. The following shell
variables have predefined meanings:
argv Argument list. Contains the list of command line argu-
ments supplied to the current invocation of the shell.
This variable determines the value of the positional
parameters $1, $2, and so on.
cdpath
Contains a list of directories to be searched by the
cd, chdir, and popd commands, if the directory argu-
ment each accepts is not a subdirectory of the current
directory.
cwd The full pathname of the current directory.
echo Echo commands (after substitutions) just before execu-
tion.
fignore
A list of filename suffixes to ignore when attempting
filename completion. Typically the single word `.o'.
filec Enable filename completion, in which case the
Control-d character EOT and the ESC character have
special significance when typed in at the end of a
terminal input line:
EOT Print a list of all filenames that start with
the preceding string.
ESC Replace the preceding string with the longest
unambiguous extension.
hardpaths
If set, pathnames in the directory stack are resolved
to contain no symbolic-link components.
histchars
A two-character string. The first character replaces !
as the history-substitution character. The second
replaces the carat (^) for quick substitutions.
history
The number of lines saved in the history list. A very
large number may use up all of the C shell's memory.
If not set, the C shell saves only the most recent
command.
home The user's home directory. The filename expansion of ~
refers to the value of this variable.
ignoreeof
If set, the shell ignores EOF from terminals. This
protects against accidentally killing a C shell by
typing a Control-d.
mail A list of files where the C shell checks for mail. If
the first word of the value is a number, it specifies
a mail checking interval in seconds (default 5
minutes).
nobeep
Suppress the bell during command completion when ask-
ing the C shell to extend an ambiguous filename.
noclobber
Restrict output redirection so that existing files are
not destroyed by accident. > redirections can only be
made to new files. >> redirections can only be made to
existing files.
noglob
Inhibit filename substitution. This is most useful in
shell scripts once filenames (if any) are obtained and
no further expansion is desired.
nonomatch
Return the filename substitution pattern, rather than
an error, if the pattern is not matched. Malformed
patterns still result in errors.
notify
If set, the shell notifies you immediately as jobs are
completed, rather than waiting until just before issu-
ing a prompt.
path The list of directories in which to search for com-
mands. path is initialized from the environment vari-
able PATH, which the C shell updates whenever path
changes. A null word ('') specifies the current direc-
tory. The default is typically (/usr/bin .). One may
override this initial search path upon csh start-up by
setting it in .cshrc or .login (for login shells
only). If path becomes unset, only full pathnames will
execute. An interactive C shell will normally hash the
contents of the directories listed after reading
.cshrc, and whenever path is reset. If new commands
are added, use the rehash command to update the table.
prompt
The string an interactive C shell prompts with. Nonin-
teractive shells leave the prompt variable unset.
Aliases and other commands in the .cshrc file that are
only useful interactively, can be placed after the
following test: `if ($?prompt == 0) exit', to reduce
startup time for noninteractive shells. A ! in the
prompt string is replaced by the current event number.
The default prompt is hostname% for mere mortals, or
hostname# for the privileged user.
The setting of $prompt has three meanings:
$prompt not set
non-interactive shell, test $?prompt.
$prompt set but == ""
.cshrc called by the which(1) command.
$prompt set and != ""
normal interactive shell.
savehist
The number of lines from the history list that are
saved in ~/.history when the user logs out. Large
values for savehist slow down the C shell during
startup.
shell The file in which the C shell resides. This is used in
forking shells to interpret files that have execute
bits set, but that are not executable by the system.
status
The status returned by the most recent command. If
that command terminated abnormally, 0200 is added to
the status. Built-in commands that fail return exit
status 1; all other built-in commands set status to 0.
time Control automatic timing of commands. Can be supplied
with one or two values. The first is the reporting
threshold in CPU seconds. The second is a string of
tags and text indicating which resources to report on.
A tag is a percent sign (%) followed by a single
upper-case letter (unrecognized tags print as text):
%D Average amount of unshared data space used in Kilo-
bytes.
%E Elapsed (wallclock) time for the command.
%F Page faults.
%I Number of block input operations.
%K Average amount of unshared stack space used in Kilo-
bytes.
%M Maximum real memory used during execution of the pro-
cess.
%O Number of block output operations.
%P Total CPU time - U (user) plus S (system) - as a per-
centage of E (elapsed) time.
%S Number of seconds of CPU time consumed by the kernel
on behalf of the user's process.
%U Number of seconds of CPU time devoted to the user's
process.
%W Number of swaps.
%X Average amount of shared memory used in Kilobytes.
The default summary display outputs from the %U, %S, %E, %P,
%X, %D, %I, %O, %F, and %W tags, in that order.
verbose
Display each command after history substitution takes
place.
Large File Behavior
See largefile(5) for the description of the behavior of csh
when encountering files greater than or equal to 2 Gbyte (2
**31 bytes).
FILES
~/.cshrc
Read at beginning of execution by each shell.
~/.login
Read by login shells after .cshrc at login.
~/.logout
Read by login shells at logout.
~/.history
Saved history for use at next login.
/usr/bin/sh
The Bourne shell, for shell scripts not starting with
a `#'.
/tmp/sh*
Temporary file for `<<'.
/etc/passwd
Source of home directories for `~name'.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|
SEE ALSO
bc(1), echo(1), login(1), ls(1), more(1), ps(1), sh(1),
shell_builtins(1), tset(1B), which(1), df(1M), swap(1M),
sysdef(1M), access(2), exec(2), fork(2), pipe(2), a.out(4),
environ(4), ascii(5), attributes(5), environ(5), large-
file(5), termio(7I)
DIAGNOSTICS
You have stopped jobs.
You attempted to exit the C shell with stopped jobs
under job control. An immediate second attempt to exit
will succeed, terminating the stopped jobs.
WARNINGS
The use of setuid shell scripts is strongly discouraged.
NOTES
Words can be no longer than 1024 bytes. The system limits
argument lists to 1,048,576 bytes. However, the maximum
number of arguments to a command for which filename expan-
sion applies is 1706. Command substitutions may expand to no
more characters than are allowed in the argument list. To
detect looping, the shell restricts the number of alias sub-
stitutions on a single line to 20.
When a command is restarted from a stop, the shell prints
the directory it started in if this is different from the
current directory; this can be misleading (that is, wrong)
as the job may have changed directories internally.
Shell built-in functions are not stoppable/restartable. Com-
mand sequences of the form a ; b ; c are also not handled
gracefully when stopping is attempted. If you suspend b, the
shell never executes c. This is especially noticeable if the
expansion results from an alias. It can be avoided by plac-
ing the sequence in parentheses to force it into a subshell.
Control over terminal output after processes are started is
primitive; use the Sun Window system if you need better out-
put control.
Commands within loops, prompted for by ?, are not placed in
the history list.
Control structures should be parsed rather than being recog-
nized as built-in commands. This would allow control com-
mands to be placed anywhere, to be combined with |, and to
be used with & and ; metasyntax.
It should be possible to use the : modifiers on the output
of command substitutions. There are two problems with :
modifier usage on variable substitutions: not all of the
modifiers are available, and only one modifier per substitu-
tion is allowed.
The g (global) flag in history substitutions applies only to
the first match in each word, rather than all matches in all
words. The common text editors consistently do the latter
when given the g flag in a substitution command.
Quoting conventions are confusing. Overriding the escape
character to force variable substitutions within double
quotes is counterintuitive and inconsistent with the Bourne
shell.
Symbolic links can fool the shell. Setting the hardpaths
variable alleviates this.
It is up to the user to manually remove all duplicate path-
names accrued from using built-in commands as
set path = pathnames
or
setenv PATH = pathnames
more than once. These often occur because a shell script or
a .cshrc file does something like
`set path=(/usr/local /usr/hosts $path)'
to ensure that the named directories are in the pathname
list.
The only way to direct the standard output and standard
error separately is by invoking a subshell, as follows:
command > outfile) >& errorfile
Although robust enough for general use, adventures into the
esoteric periphery of the C shell may reveal unexpected
quirks.
If you start csh as a login shell and you do not have a
.login in your home directory, then the csh reads in the
/etc/.login.
When the shell executes a shell script that attempts to exe-
cute a non-existent command interpreter, the shell returns
an erroneous diagnostic message that the shell script file
does not exist.
BUGS
As of this writing, the time built-in command does NOT com-
pute the last 6 fields of output, rendering the output to
erroneously report the value "0" for these fields:
example %time ls -R
9.0u 11.0s 3:32 10% 0+0k 0+0io 0pf+0w
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