CSH(1HAS) User Commands CSH(1HAS)

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 convenient features for
interactive use that are not available with the Bourne shell, including
filename completion, command 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 invocations:
First, commands in /etc/.login are executed. Next, commands from the
.cshrc file your home directory are executed. 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 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
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 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 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.

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
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 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.

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 occurs 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.


!?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 command 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 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.

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 can 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 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.

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 128 letters and
digits, and starts with a letter. An underscore (_) is considered a
letter). A variable's value is a space-separated list of zero or more
words. If the shell supports a variable name up to 128 characters the
variable SUNW_VARLEN is defined. If a variable name of up to 128
characters is not supported, then an older version of the shell is being
used, and the shell variable name length has a maximum length of 20.

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
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 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 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 can not be modified with : modifiers.

$?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 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 dash (-), and includes all the characters in
between in the ASCII collating sequence (see
ascii(7)).


{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.


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 is
a string, 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.
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:

-rfilename
Return true, or 1 if the user has read access. Otherwise
it returns false, or 0.


-wfilename
True if the user has write access.


-xfilename
True if the user has execute permission (or search
permission on a directory).


-efilename
True if filename exists.


-ofilename
True if the user owns filename.


-z filename
True if filename is of zero length (empty).


-ffilename
True if filename is a plain file.


-dfilename
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, backward goto commands succeeds on nonseekable inputs.)

Command Execution

If the command is a C shell built-in command, 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 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 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() system call (see exec(2)). The kernel then
attempts to overlay the new process with the desired program. If the file
is an executable binary (in a.out(5) 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 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 (typically Control-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


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-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 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 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
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
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
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 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 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 is used. csh, by default, invokes
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 execute 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
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
terminate the execution of the current
iteration of the loop and the built-in command
break can be used to terminate execution of the
foreach command. When this command is read from
the terminal, the loop is read 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.


gotolabel

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
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
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. 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. The
string unlimited requests that the current limit, if any, be removed.
If max-use is omitted, print the current limit. If resource is
omitted, display all limits. Run the sysdef(8) command to display
maximum limits for certain resources in your system (although it does
not report stack size). 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 can 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(8)).


datasize (heapsize)
Maximum data size (including stack) for the
process. This is the size of your virtual
memory See swap(8).


stacksize
Maximum stack size for the process. The
default stack size is 2^64 bytes. You can use
limit(1) to change this default within a
shell.


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 statements apply. All processes detached with & are effectively
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 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.
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 setvar[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
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.

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(7)) 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 determines 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 messages 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 can be nested, but if they
are nested too deeply the shell can run out of file descriptors. An
error in a sourced file at any level terminates all nested source
commands.

-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 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. As of this writing, the time built-in
command does NOT compute 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


(See 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, restricting all permissions from everyone else; 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 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 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. As with unset, pattern matching
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 nonzero), 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, 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 assignment 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
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.


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.


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 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 can 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 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
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 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 is
typically (/usr/bin .). One can 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 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# 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
Kilobytes.


%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
Kilobytes.


%M
Maximum real memory used during execution of the
process.


%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.


verbose
Display each command after history substitution takes place.

Large File Behavior

See largefile(7) 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(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|CSI | Enabled |
+---------------+-----------------+

SEE ALSO

bc(1), echo(1), limit(1), login(1), ls(1), more(1), pfcsh(1), pfexec(1),
ps(1), sh(1), shell_builtins(1), which(1), tset(1B), access(2), exec(2),
fork(2), pipe(2), termio(4I), a.out(5), ascii(7), attributes(7),
environ(7), largefile(7), df(8), swap(8), sysdef(8)

DIAGNOSTICS

You have stopped jobs.
You attempted to exit the C shell with stopped
jobs under job control. An immediate second
attempt to exit succeeds, 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 expansion applies is 1706. Command substitutions can
expand to no more characters than are allowed in the argument list. 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 might 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.

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 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 pathnames 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 can 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 execute 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 compute 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


April 9, 2016 CSH(1HAS)