csh(1)csh(1)NAMEcsh - shell command interpreter with a C-like syntax
SYNOPSIScsh [ -bcefinstvVxX ] [ argument ... ]
DESCRIPTION
csh, the C shell, is a command interpreter with a syntax reminiscent of
the C language. It provides a number of convenient features for
interactive use that are not available with the standard (Bourne) shell,
including filename completion, command aliasing, history substitution,
job control, and a number of built-in commands. As with the standard
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. In this case, before executing the
commands from the .cshrc file, the shell executes the commands from the
following files in the order specified: /etc/cshrc, /etc/.login and
/etc/csh.cshrc. These files can be used to provide system-wide settings
for all csh users. After executing commands from the .cshrc file, a
login 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. Please note that csh can run as a login
shell if it is invoked upon startup of a window shell such as xwsh(1G).
This is so any terminal type information that might be contained in the
.login file(s) can be made known to the window shell.
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, below. Finally, the shell executes
each command in the current line.
Noninteractive Operation
When running noninteractively, the shell does not prompt for input from
the terminal. A noninteractive C shell can execute a command supplied as
an argument on its command line, or interpret commands from a script.
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The following options are available:
-b Force 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 a set-user-ID script unless this option is present.
-c Read commands from the first filename argument (which must be
present). Remaining arguments are placed in argv, the argument-list
variable.
-e Exit if a command terminates abnormally or yields a nonzero exit
status.
-f Fast start. Read neither the .cshrc file, nor the .login file (if a
login shell) upon startup.
-i Forced interactive. Prompt for command line input, even if the
standard input does not appear to be a terminal (character-special
device).
-n Parse (interpret), but do not execute commands. This option can be
used to check C shell scripts for syntax errors.
-s Take commands from the standard input.
-t Read and execute 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. Set the verbose predefined variable; command input is
echoed after history substitution (but before other substitutions)
and before execution.
-V Set verbose before reading .cshrc.
-x Echo. Set the echo variable; echo commands after all substitutions
and just before execution.
-X Set echo before reading .cshrc.
Except with the options -c, -i, -s, or -t, the first nonoption argument
is taken to be the name of a command or script. It is passed as argument
zero, and subsequent arguments are added to the argument list for that
command or script. csh scripts should always start with the line
#! /bin/csh -f
which causes the script to be executed by /bin/csh even if invoked by a
user running a shell other than csh and inhibits processing of the .cshrc
file to prevent interference from aliases defined by the invoking user.
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csh(1)csh(1)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 (usually typed as
<Ctrl-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 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 possible 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 newline
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 Substitution, 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) specifies 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 command 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.
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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 execution 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 simplifies spelling corrections
and the repetition of complicated 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 can occur anywhere 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 substitutions 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 substitution
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.
!{...} Insulate a history reference from adjacent characters (if
necessary).
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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 most recent) ?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 a sequence of one or more
of the following modifiers, each 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.
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 substitutions.
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 expressions, but
character strings. Any character can be used as the delimiter in place
of /. A backslash quotes the delimiter 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.
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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 command 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 contain 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 cannot 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, invoke the
pipeline with the temporary file as its standard input. word
is not subjected to variable, filename, or command
substitution, and each line is compared to it before any
substitutions 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.
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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 information 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 character, 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).
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
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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 subsequent
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 can
consist of (or result in) a either single number, two
numbers separated by a `-', or an asterisk. 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 command
input is being read. 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 cannot be modified with : modifiers.
$?var
${?var} Substitutes the string 1 if var is set or 0 if it is not set.
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$?0 Substitutes 1 if the current input filename is known, or 0 if
it is not.
$$ Substitute 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 expressions 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 therefore
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 globbing) to an alphabetically
sorted list of filenames, as follows:
* 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 minus-sign (-), 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 construct is not
sorted. For instance, {b,a} expands to `b' `a', (not `a'
`b'). As special cases, the characters { 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.
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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 character 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. Components of an expression are separated by white space.
Null or missing values are considered 0. The result of all expressions
are strings, which can represent decimal numbers.
The following C shell operators are grouped in order of precedence:
(...) grouping
~ one's complement
! logical negation
* / % multiplication, division, remainder (These are right
associative, which can lead to unexpected results.
Group combinations 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 file Return true, or 1 if the user has read access. Otherwise it
returns false, or 0.
-w file True if the user has write access.
-x file True if the user has execute permission (or search permission
on a directory).
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csh(1)csh(1)-e file True if file exists.
-o file True if the user owns file.
-z file True if file is of zero length (empty).
-f file True if file is a plain file.
-d file True if file is a directory.
-l file True if file is a symbolic link.
-c file True if file is a character special file.
-b file True if file is a block special file.
-p file True if file is a named pipe (fifo).
-u file True if file has the set-user-ID permission bit set (see
chmod(1)).
-g file True if file has the set-group-ID permission bit set (see
chmod(1)).
-k file True if file has the sticky bit set (see chmod(1)).
-s file True if file has size strictly greater than zero.
-t file True if file is an open file descriptor for a terminal device.
If file 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 that,
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
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, backward goto commands succeed on nonseekable inputs.)
Command Execution
If the command is a C shell built-in, the shell executes it directly.
Otherwise, the shell searches for a file by that name with execute
access. If the command-name contains 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 directory
in the path variable for the command. To speed the search, the shell
uses its hash table (see the rehash built-in) to eliminate directories
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that have no applicable files. This hashing can be disabled with the -c
or -t, options, or the unhash built-in.
As a special case, if there is no / in the name of the script and there
is an alias for the word shell, the expansion 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 permissions, the shell
forks a new process and passes it, along with its arguments to the kernel
(using the execve(2) system call). The kernel then attempts to overlay
the new process with the desired program. If the file is an executable
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 argument.
If neither of the above conditions holds, the kernel cannot overlay the
file (the execve(2) call fails); 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 standard (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. 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 (typically <Ctrl-z>). When a command, or
command sequence (semicolon 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
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To see the current list of jobs, use the jobs built-in command. The job
most recently stopped (or put into the background if none are stopped) is
referred to as the current job, and is indicated with a `+'. The
previous job is indicated 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-ins.
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 command
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 a finishes or becomes blocked. It normally displays a
message to this effect as it issues a prompt, so as 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.
Built-In 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 performs
no action.
alias [ name [ def ] ]
Assign def to the alias name. def is a list of words that
can contain escaped history-substitution metasyntax. name
is not allowed to be alias or unalias. If def is omitted,
the alias name is displayed along with its current
definition. If both name and def are omitted, all aliases
are displayed.
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bg [% Run the current or specified jobs in the background.
break Resume execution after the end of the nearest enclosing
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 directories
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 nearest enclosing while or
foreach.
default: Labels the default case in a switch statement. The
default should come after all case labels. Any remaining
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 printout; 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 or the \c
escape is specified. The following C-like escape
sequences are available:
\b backspace
\c print line without newline
\f formfeed
\n newline
\r carriage return
\t tab
\\ backslash
\0n the 8-bit character whose code is the 1-, 2- or 3-
digit octal number n. Note that \n (no leading zero)
is accepted for backwards compatibility with older
IRIX cshs. This can cause unexpected results in
older scripts if the character immediately trailing
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csh(1)csh(1)
three digits is also numeric.
eval argument ...
Reads the arguments as input to the shell, and executes
the resulting command(s). This is usually used to execute
commands generated as the result of command or variable
substitution, since parsing occurs before these
substitutions. See tset(1) for an example of how to use
eval.
exec command Execute command in place of the current shell, which
terminates.
exit [ (expr) ]
The shell 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 foreground.
foreach var (wordlist)
...
end The variable var is successively set to each member of
wordlist. The sequence of commands between this command
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 can be used to continue the
loop prematurely and the built-in command break to
terminate it prematurely. When this command is read from
the terminal, the loop is read up once prompting with ?
before any statements in the loop are executed.
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 filename and 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 characters. Execution
continues after the indicated line. It is an error to
jump to a label that occurs between a while or for built-
in, and its corresponding end.
history [ -hr ] [ n ]
Display the history list; if n is given, display only the
n most recent events.
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csh(1)csh(1)-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. Typing 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 (continue) 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.
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csh(1)csh(1)-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 can raise the hard
limits.
resource is one of:
cputime Maximum CPU seconds per process.
filesize Largest single file allowed.
datasize Maximum data size (including stack) for the
process.
stacksize Maximum stack size for the process. Note:
If this is set too high, sproc(2) may fail.
coredumpsize Maximum size of a core dump (file).
memoryuse Maximum amount of physical memory per
process (resident set size).
vmemoryuse Maximum amount of virtual memory per
process, including text, data, heap, shared
memory, mapped files, stack, etc..
descriptors Maximum number of open file descriptors per
process.
threads Maximum number of pthreads(5) which may be
created.
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 file
or memory size limits.
nm n megabytes or minutes (for cputime).
mm:ss Minutes and seconds (for cputime).
The resource argument can be abbreviated by using only
enough characters to make the name unambiguous. Refer to
the setrlimit(2) manual entry for more information about
process resource limits.
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
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csh(1)csh(1)
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 commands apply. All
processes detached with & are effectively nohup'd.
notify [ %job ] ...
Notify the user asynchronously when the status of the
current, or of 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 directory.
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.
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csh(1)csh(1)
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.
Multiple assignments can be performed with a single set
command:
set notify mail=(30 /usr/mail/nemo)
setenv [ VAR [ word ] ]
With no arguments, setenv displays all environment
variables. With the VAR argument sets the environment
variable VAR to have an empty (null) value. (By
convention, environment variables are normally 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.
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 can 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 commands.
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csh(1)csh(1)-h Place commands from the file name on the history list
without executing them.
stop [ %job ] ...
Stop the current or specified background job.
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 specified
string, which is first command and filename expanded. The
file metacharacters *, ? and [...] can 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.
umask [ value ]
Display the file creation mask. With value set the file
creation mask. value is given in octal, and is XORed with
the permissions of 666 for files and 777 for directories
to arrive at the permissions for new files. Common values
include 002, giving complete access to the group, and read
(and directory 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 table.
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csh(1)csh(1)
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 can do this.
unset pattern Remove variables whose names match (filename substitution)
pattern. All variables are removed by `unset *'; this has
noticeably distasteful side-effects.
unsetenv variable
Remove variable from the environment. Pattern matching,
as with unset is not performed.
wait Wait for background jobs to finish (or for an interrupt)
before prompting.
while (expr)
...
end While expr is true (evaluates to non-zero), repeat
commands between the while and the matching end statement.
break and continue can 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
background.
@ [ var =expr ]
@ [ var [n] =expr ]
With no arguments, display the values for all shell
variables. With arguments, 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 *=, +=, etc., are available as in C. The
space separating the name from the assignment operator is
optional. Spaces are, however, mandatory in separating
components of expr that would otherwise be single words.
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csh(1)csh(1)
Special postfix operators, ++ and -- increment or
decrement name, respectively.
Environment Variables and Predefined Shell Variables
Unlike the standard 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
initialization. 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 variable 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 arguments
supplied to the current invocation of the shell. This variable
determines the value of the positional parameters $1, $2, and
so on. Note: argv[0] does not contain the command name.
cdpath Contains a list of directories to be searched by the cd, chdir,
and popd commands, if the directory argument each accepts is
not a subdirectory of the current directory.
child The process id of the most recently started background job.
cwd The full pathname of the current directory.
echo Echo commands (after substitutions), just before execution.
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 <Ctrl-d>
character <Ctrl-d>) 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.
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csh(1)csh(1)
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 <Ctrl-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 asking 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 Returns 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 issuing a
prompt.
path The list of directories in which to search for commands. path
is initialized from the environment variable PATH, which the C
shell updates whenever path changes. A null word specifies the
current directory. The default search path for normal users
is: (. /usr/sbin /usr/bsd /bin /usr/bin /usr/bin/X11). For
the privileged user, the default search path is: (/usr/sbin
/usr/bsd /bin /usr/bin /etc /usr/etc /usr/bin/X11). If path
becomes unset, only full pathnames execute. An interactive C
shell normally hashes 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. Noninteractive
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#
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csh(1)csh(1)
for the privileged user.
If the prompt string includes the sequence \@x, where x is one
of the characters listed below, it is replaced by the current
time and date in the indicated format.
R time as HH:MM AM/PM, for example, 8:40PM
r time as HH:MM:SS AM/PM, for example, 08:40:25 PM
m month of year - 01 to 12
d day of month - 01 to 31
y last 2 digits of year - 00 to 99
D date as mm/dd/yy
H hour - 00 to 23
M minute - 00 to 59
S second - 00 to 59
T time as HH:MM:SS
j day of year - 001 to 366
w day of week - Sunday = 0
a abbreviated weekday - Sun to Sat
h abbreviated month - Jan to Dec
n insert a newline character
t insert a tab character
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. To prevent su sessions
from overwriting the underlying user's history file, the shell
only writes in the ~/.history file if its current effective
user id is the same as the owner of the directory specified by
the home variable.
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 Kilobytes.
%E Elapsed (wallclock) time for the command.
%F Page faults.
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csh(1)csh(1)
%I Number of block input operations.
%K Average amount of unshared stack space used in Kilobytes.
%M Maximum real memory used during execution of the process
in Kilobytes.
%O Number of block output operations.
%P Total CPU time -- U (user) plus S (system) -- as a
percentage 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.
Note that the values for %D, %K, and %X always print as zero
since the IRIX kernel does not maintain the getrusage(3)
counters required to calculate them.
verbose Display each command after history substitution takes place.
FILES
~/.cshrc Read at beginning of execution by each shell.
/etc/cshrc Read by login shells before .cshrc at login.
/etc/.login Read by login shells before .cshrc and after /etc/cshrc.
/etc/csh.cshrc Read by login shells before .cshrc and after /etc/.login.
~/.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 Standard shell, for shell scripts not starting with a `#'.
/tmp/sh* Temporary file for `<<'.
/etc/passwd Source of home directories for `~name'.
SEE ALSOlogin(1), sh(1), xwsh(1G), access(2), exec(2), fork(2), pipe(2),
a.out(4), ascii(5), environ(5), termio(7).
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.
NOTES
Words can be no longer than 1024 characters. The system limits argument
lists (including all environment variables) to 20480 characters by
default. Command substitutions can expand to no more characters than are
allowed in the argument list. Sometimes, particularly when using
wildcards, the shell will fail to execute a command, and complain with
the message
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csh(1)csh(1)
Arguments too long
This can often be avoided by using multiple commands, the xargs(1)
command, or by increasing the ncargs kernel parameter with the
systune(1m) command. If the kernel parameter is increased, currently
running csh's will not notice the change. It is necessary to start a new
shell, or logout and back in, for the change to be effective.
To detect looping, the shell restricts the number of alias substitutions
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. Command
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 placing the sequence in parentheses to force it into a
subshell.
Control over terminal output after processes are started is primitive.
Multiline shell procedures should be provided, as they are with the
standard (Bourne) shell.
Commands within loops, prompted for by ?, are not placed in the history
list.
Control structures should be parsed rather than being recognized as
built-in commands. This would allow control commands 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 substitution 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 the
standard 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.
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csh(1)csh(1)
`set path' should remove duplicate pathnames from the pathname list.
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:
example% (command > outfile) >& errorfile
Although robust enough for general use, adventures into the esoteric
periphery of the C shell may reveal unexpected quirks.
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