CSH(1)CSH(1)NAMEcsh - a shell (command interpreter) with C-like syntax
SYNOPSIScsh [ -cefinstvVxX ] [ arg ... ]
DESCRIPTION
Csh is a first implementation of a command language interpreter
incorporating a history mechanism (see History Substitutions), job
control facilities (see Jobs), interactive file name and user name
completion (see File Name Completion), and a C-like syntax. So as to
be able to use its job control facilities, users of csh must (and
automatically) use the new tty driver fully described in tty(4). This
new tty driver allows generation of interrupt characters from the
keyboard to tell jobs to stop. See stty(1) for details on setting
options in the new tty driver.
An instance of csh begins by executing commands from the file `.cshrc'
in the home directory of the invoker. If this is a login shell then it
also executes commands from the file `.login' there. It is typical for
users on crt's to put the command ``stty crt'' in their .login file,
and to also invoke tset(1) there.
In the normal case, the shell will then begin reading commands from the
terminal, prompting with `% '. Processing of arguments and the use of
the shell to process files containing command scripts will be described
later.
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 command history list and then parsed. Finally each
command in the current line is executed.
When a login shell terminates it executes commands from the file
`.logout' in the users home directory.
Lexical structure
The shell splits input lines into words at blanks and tabs with the
following exceptions. The characters `&' `|' `;' `<' `>' `(' `)' form
separate words. If doubled in `&&', `||', `<<' or `>>' these pairs
form single words. These parser metacharacters may be made part of
other words, or prevented their special meaning, by preceding them with
`\'. A newline preceded by a `\' is equivalent to a blank.
In addition strings enclosed in matched pairs of quotations, `'', ``'
or `"', form parts of a word; metacharacters in these strings,
including blanks and tabs, do not form separate words. These
quotations have semantics to be described subsequently. Within pairs
of `´' or `"' characters a newline preceded by a `\' gives a true
newline character.
When the shell's input is not a terminal, the character `#' introduces
a comment which continues to the end of the input line. It is
prevented this special meaning when preceded by `\' and in quotations
using ``', `´', and `"'.
Commands
A simple command is a sequence of words, the first of which specifies
the command to be executed. A simple command or a sequence of simple
commands separated by `|' characters forms a pipeline. The output of
each command in a pipeline is connected to the input of the next.
Sequences of pipelines may be separated by `;', and are then executed
sequentially. A sequence of pipelines may be executed without
immediately waiting for it to terminate by following it with an `&'.
Any of the above may be placed in `(' `)' to form a simple command
(which may be a component of a pipeline, etc.) It is also possible to
separate pipelines with `||' or `&&' indicating, as in the C language,
that the second is to be executed only if the first fails or succeeds
respectively. (See Expressions.)
Jobs
The shell associates a job with each pipeline. It keeps a table of
current jobs, printed by the jobs command, and assigns them small
integer numbers. When a job is started asynchronously with `&', the
shell prints a line which looks like:
[1] 1234
indicating that the job which was started asynchronously was job number
1 and had one (top-level) process, whose process id was 1234.
If you are running a job and wish to do something else you may hit the
key ^Z (control-Z) which sends a STOP signal to the current job. The
shell will then normally indicate that the job has been `Stopped', and
print another prompt. You can then manipulate the state of this job,
putting it in the background with the bg command, or run some other
commands and then eventually bring the job back into the foreground
with the foreground command fg. A ^Z takes effect immediately and is
like an interrupt in that pending output and unread input are discarded
when it is typed. There is another special key ^Y which does not
generate a STOP signal until a program attempts to read(2) it. This
can usefully be typed ahead when you have prepared some commands for a
job which you wish to stop after it has read them.
A job being run in the background will stop if it tries to read from
the terminal. Background jobs are normally allowed to produce output,
but this can be disabled by giving the command ``stty tostop''. If you
set this tty option, then background jobs will stop when they try to
produce output like they do when they try to read input.
There are several ways to refer to jobs in the shell. The character
`%' introduces a job name. If you wish to refer to job number 1, you
can name it as `%1'. Just naming a job brings it to the foreground;
thus `%1' is a synonym for `fg %1', bringing job 1 back into the
foreground. Similarly saying `%1 &' resumes job 1 in the background.
Jobs can also be named by prefixes of the string typed in to start
them, if these prefixes are unambiguous, thus `%ex' would normally
restart a suspended ex(1) job, if there were only one suspended job
whose name began with the string `ex'. It is also possible to say
`%?string' which specifies a job whose text contains string, if there
is only one such job.
The shell maintains a notion of the current and previous jobs. In
output pertaining to jobs, the current job is marked with a `+' and the
previous job with a `-'. The abbreviation `%+' refers to the current
job and `%-' refers to the previous job. For close analogy with the
syntax of the history mechanism (described below), `%%' is also a
synonym for the current job.
Status reporting
This shell learns immediately whenever a process changes state. It
normally informs you whenever a job becomes blocked so that no further
progress is possible, but only just before it prints a prompt. This is
done so that it does not otherwise disturb your work. If, however, you
set the shell variable notify, the shell will notify you immediately of
changes of status in background jobs. There is also a shell command
notify which marks a single process so that its status changes will be
immediately reported. By default notify marks the current process;
simply say `notify' after starting a background job to mark it.
When you try to leave the shell while jobs are stopped, you will be
warned that `You have stopped jobs.' You may use the jobs command to
see what they are. If you do this or immediately try to exit again,
the shell will not warn you a second time, and the suspended jobs will
be terminated.
File Name Completion
When the file name completion feature is enabled by setting the shell
variable filec (see set), csh will interactively complete file names
and user names from unique prefixes, when they are input from the
terminal followed by the escape character (the escape key, or
control-[). For example, if the current directory looks like
DSC.OLD bin cmd lib xmpl.c
DSC.NEW chaosnet cmtest mail xmpl.o
bench class dev mbox xmpl.out
and the input is
% vi ch<escape>
csh will complete the prefix ``ch'' to the only matching file name
``chaosnet'', changing the input line to
% vi chaosnet
However, given
% vi D<escape>
csh will only expand the input to
% vi DSC.
and will sound the terminal bell to indicate that the expansion is
incomplete, since there are two file names matching the prefix ``D''.
If a partial file name is followed by the end-of-file character
(usually control-D), then, instead of completing the name, csh will
list all file names matching the prefix. For example, the input
% vi D<control-D>
causes all files beginning with ``D'' to be listed:
DSC.NEW DSC.OLD
while the input line remains unchanged.
The same system of escape and end-of-file can also be used to expand
partial user names, if the word to be completed (or listed) begins with
the character ``~''. For example, typing
cd ~ro<control-D>
may produce the expansion
cd ~root
The use of the terminal bell to signal errors or multiple matches can
be inhibited by setting the variable nobeep.
Normally, all files in the particular directory are candidates for name
completion. Files with certain suffixes can be excluded from
consideration by setting the variable fignore to the list of suffixes
to be ignored. Thus, if fignore is set by the command
% set fignore = (.o .out)
then typing
% vi x<escape>
would result in the completion to
% vi xmpl.c
ignoring the files "xmpl.o" and "xmpl.out". However, if the only
completion possible requires not ignoring these suffixes, then they are
not ignored. In addition, fignore does not affect the listing of file
names by control-D. All files are listed regardless of their suffixes.
Substitutions
We now describe the various transformations the shell performs on the
input in the order in which they occur.
History substitutions
History substitutions place words from previous command input as
portions of new commands, making it easy to repeat commands, repeat
arguments of a previous command in the current command, or fix spelling
mistakes in the previous command with little typing and a high degree
of confidence. History substitutions begin with the character `!' and
may begin anywhere in the input stream (with the proviso that they do
not nest.) This `!' may be preceded by an `\' to prevent its special
meaning; for convenience, a `!' is passed unchanged when it is followed
by a blank, tab, newline, `=' or `('. (History substitutions also
occur when an input line begins with `^'. This special abbreviation
will be described later.) Any input line which contains history
substitution is echoed on the terminal before it is executed as it
could have been typed without history substitution.
Commands input from the terminal which consist of one or more words are
saved on the history list. The history substitutions reintroduce
sequences of words from these saved commands into the input stream.
The size of which is controlled by the history variable; the previous
command is always retained, regardless of its value. Commands are
numbered sequentially from 1.
For definiteness, consider the following output from the history
command:
9 write michael
10 ex write.c
11 cat oldwrite.c
12 diff *write.c
The commands are shown with their event numbers. It is not usually
necessary to use event numbers, but the current event number can be
made part of the prompt by placing an `!' in the prompt string.
With the current event 13 we can refer to previous events by event
number `!11', relatively as in `!-2' (referring to the same event), by
a prefix of a command word as in `!d' for event 12 or `!wri' for event
9, or by a string contained in a word in the command as in `!?mic?'
also referring to event 9. These forms, without further modification,
simply reintroduce the words of the specified events, each separated by
a single blank. As a special case `!!' refers to the previous command;
thus `!!' alone is essentially a redo.
To select words from an event we can follow the event specification by
a `:' and a designator for the desired words. The words of an input
line are numbered from 0, the first (usually command) word being 0, the
second word (first argument) being 1, etc. The basic word designators
are:
0 first (command) word
n n'th argument
^ first argument, i.e. `1'
$ last argument
% word matched by (immediately preceding) ?s? search
x-y range of words
-y abbreviates `0-y'
* abbreviates `^-$', or nothing if only 1 word in event
x* abbreviates `x-$'
x- like `x*' but omitting word `$'
The `:' separating the event specification from the word designator can
be omitted if the argument selector begins with a `^', `$', `*' `-' or
`%'. After the optional word designator can be placed a sequence of
modifiers, each preceded by a `:'. The following modifiers are
defined:
h Remove a trailing pathname component, leaving the head.
r Remove a trailing `.xxx' component, leaving the root name.
e Remove all but the extension `.xxx' part.
s/l/r/ Substitute l for r
t Remove all leading pathname components, leaving the tail.
& Repeat the previous substitution.
g Apply the change globally, prefixing the above, e.g. `g&'.
p Print the new command but do not execute it.
q Quote the substituted words, preventing further substitutions.
x Like q, but break into words at blanks, tabs and newlines.
Unless preceded by a `g' the modification is applied only to the first
modifiable word. With substitutions, it is an error for no word to be
applicable.
The left hand side of substitutions are not regular expressions in the
sense of the editors, but rather strings. Any character may be used as
the delimiter in place of `/'; a `\' quotes the delimiter into the l
and r strings. The character `&' in the right hand side is replaced by
the text from the left. A `\' quotes `&' also. A null l uses the
previous string either from a l or from a contextual scan string s in
`!?s?'. The trailing delimiter in the substitution may be omitted if a
newline follows immediately as may the trailing `?' in a contextual
scan.
A history reference may be given without an event specification, e.g.
`!$'. In this case the reference is to the previous command unless a
previous history reference occurred on the same line in which case this
form repeats the previous reference. Thus `!?foo?^ !$' gives the first
and last arguments from the command matching `?foo?'.
A special abbreviation of a history reference occurs when the first
non-blank character of an input line is a `^'. This is equivalent to
`!:s^' providing a convenient shorthand for substitutions on the text
of the previous line. Thus `^lb^lib' fixes the spelling of `lib' in
the previous command. Finally, a history substitution may be
surrounded with `{' and `}' if necessary to insulate it from the
characters which follow. Thus, after `ls -ld ~paul' we might do
`!{l}a' to do `ls -ld ~paula', while `!la' would look for a command
starting `la'.
Quotations with ´ and "
The quotation of strings by `´' and `"' can be used to prevent all or
some of the remaining substitutions. Strings enclosed in `´' are
prevented any further interpretation. Strings enclosed in `"' may be
expanded as described below.
In both cases the resulting text becomes (all or part of) a single
word; only in one special case (see Command Substitition below) does a
`"' quoted string yield parts of more than one word; `´' quoted strings
never do.
Alias substitution
The shell maintains a list of aliases which can be established,
displayed and modified by the alias and unalias commands. After a
command line is scanned, it is parsed into distinct commands and the
first word of each command, left-to-right, is checked to see if it has
an alias. If it does, then the text which is the alias for that
command is reread with the history mechanism available as though that
command were the previous input line. The resulting words replace the
command and argument list. If no reference is made to the history
list, then the argument list is left unchanged.
Thus if the alias for `ls' is `ls -l' the command `ls /usr' would map
to `ls -l /usr', the argument list here being undisturbed. Similarly
if the alias for `lookup' was `grep !^ /etc/passwd' then `lookup bill'
would map to `grep bill /etc/passwd'.
If an alias is found, the word transformation of the input text is
performed and the aliasing process begins again on the reformed input
line. Looping is prevented if the first word of the new text is the
same as the old by flagging it to prevent further aliasing. Other
loops are detected and cause an error.
Note that the mechanism allows aliases to introduce parser metasyntax.
Thus we can `alias print ´pr \!* | lpr´' to make a command which pr's
its arguments to the line printer.
Variable substitution
The shell maintains a set of variables, each of which has as value a
list of zero or more words. Some of these variables are set by the
shell or referred to by it. For instance, the argv variable is an
image of the shell's argument list, and words of this variable's value
are referred to in special ways.
The values of variables may be displayed and changed by using the set
and unset commands. Of the variables referred to by the shell a number
are toggles; the shell does not care what their value is, only whether
they are set or not. For instance, the verbose variable is a toggle
which causes command input to be echoed. The setting of this variable
results from the -v command line option.
Other operations treat variables numerically. The `@' command permits
numeric calculations to be performed and the result assigned to a
variable. Variable values are, however, always represented as (zero or
more) strings. For the purposes of numeric operations, the null string
is considered to be zero, and the second and subsequent words of
multiword values are ignored.
After the input line is aliased and parsed, and before each command is
executed, variable substitution is performed keyed by `$' characters.
This expansion can be prevented by preceding the `$' with a `\' except
within `"'s where it always occurs, and within `´'s where it never
occurs. Strings quoted by ``' are interpreted later (see Command
substitution below) so `$' substitution does not occur there until
later, if at all. A `$' is passed unchanged if followed by a blank,
tab, or end-of-line.
Input/output redirections are recognized before variable expansion, and
are variable expanded separately. Otherwise, the command name and
entire argument list are expanded together. It is thus possible for
the first (command) word to this point to generate more than one word,
the first of which becomes the command name, and the rest of which
become arguments.
Unless enclosed in `"' or given the `:q' modifier the results of
variable substitution may eventually be command and filename
substituted. Within `"', a variable whose value consists of multiple
words expands to a (portion of) a single word, with the words of the
variables value separated by blanks. When the `:q' modifier is applied
to a substitution the variable will expand to multiple words with each
word separated by a blank and quoted to prevent later command or
filename substitution.
The following metasequences are provided for introducing variable
values into the shell input. Except as noted, it is an error to
reference a variable which is not set.
$name
${name}
Are replaced by the words of the value of variable name, each
separated by a blank. Braces insulate name from following
characters which would otherwise be part of it. Shell variables
have names consisting of up to 20 letters and digits starting with
a letter. The underscore character is considered a letter.
If name is not a shell variable, but is set in the environment,
then that value is returned (but : modifiers and the other forms
given below are not available in this case).
$name[selector]
${name[selector]}
May be used to select only some of the words from the value of
name. The selector is subjected to `$' substitution and may
consist of a single number or two numbers separated by a `-'. The
first word of a variables value is numbered `1'. If the first
number of a range is omitted it defaults to `1'. If the last
member of a range is omitted it defaults to `$#name'. The
selector `*' selects all words. It is not an error for a range to
be empty if the second argument is omitted or in range.
$#name
${#name}
Gives the number of words in the variable. This is useful for
later use in a `[selector]'.
$0
Substitutes the name of the file from which command input is being
read. An error occurs if the name is not known.
$number
${number}
Equivalent to `$argv[number]'.
$*
Equivalent to `$argv[*]'.
The modifiers `:h', `:t', `:r', `:q' and `:x' may be applied to the
substitutions above as may `:gh', `:gt' and `:gr'. If braces `{' '}'
appear in the command form then the modifiers must appear within the
braces. The current implementation allows only one `:' modifier on
each `$' expansion.
The following substitutions may not be modified with `:' modifiers.
$?name
${?name}
Substitutes the string `1' if name is set, `0' if it is not.
$?0
Substitutes `1' if the current input filename is known, `0' if it
is not.
$$
Substitute the (decimal) 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 shell script.
Command and filename substitution
The remaining substitutions, command and filename substitution, are
applied selectively to the arguments of builtin commands. This means
that portions of expressions which are not evaluated are not subjected
to these expansions. For commands which are not internal to the shell,
the command name is substituted separately from the argument list.
This occurs very late, after input-output redirection is performed, and
in a child of the main shell.
Command substitution
Command substitution is indicated by a command enclosed in ``'. The
output from such a command is normally broken into separate words at
blanks, tabs and newlines, with null words being discarded, this text
then replacing the original string. Within `"'s, only newlines force
new words; blanks and tabs are preserved.
In any case, the single final newline does not force a new word. Note
that it is thus possible for a command substitution to yield only part
of a word, even if the command outputs a complete line.
Filename substitution
If a word contains any of the characters `*', `?', `[' or `{' or begins
with the character `~', then that word is a candidate for filename
substitution, also known as `globbing'. This word is then regarded as
a pattern, and replaced with an alphabetically sorted list of file
names which match the pattern. In a list of words specifying filename
substitution it is an error for no pattern to match an existing file
name, but it is not required for each pattern to match. Only the
metacharacters `*', `?' and `[' imply pattern matching, the characters
`~' and `{' being more akin to abbreviations.
In matching filenames, the character `.' at the beginning of a filename
or immediately following a `/', as well as the character `/' must be
matched explicitly. The character `*' matches any string of
characters, including the null string. The character `?' matches any
single character. The sequence `[...]' matches any one of the
characters enclosed. Within `[...]', a pair of characters separated by
`-' matches any character lexically between the two.
The character `~' at the beginning of a filename is used to refer to
home directories. Standing alone, i.e. `~' it expands to the invokers
home directory as reflected in the value of the variable home. When
followed by a name consisting of letters, digits and `-' characters the
shell searches for a user with that name and substitutes their home
directory; thus `~ken' might expand to `/usr/ken' and `~ken/chmach' to
`/usr/ken/chmach'. If the character `~' is followed by a character
other than a letter or `/' or appears not at the beginning of a word,
it is left undisturbed.
The metanotation `a{b,c,d}e' is a shorthand for `abe ace ade'. Left to
right order is preserved, with results of matches being sorted
separately at a low level to preserve this order. This construct may
be nested. Thus `~source/s1/{oldls,ls}.c' expands to
`/usr/source/s1/oldls.c /usr/source/s1/ls.c' whether or not these files
exist without any chance of error if the home directory for `source' is
`/usr/source'. Similarly `../{memo,*box}' might expand to `../memo
../box ../mbox'. (Note that `memo' was not sorted with the results of
matching `*box'.) As a special case `{', `}' and `{}' are passed
undisturbed.
Input/output
The standard input and standard output of a command may be redirected
with the following syntax:
< name
Open file name (which is first variable, command and filename
expanded) as the standard input.
<< word
Read the shell input up to a line which is identical to word.
Word is not subjected to variable, filename or command
substitution, and each input line is compared to word before any
substitutions are done on this input line. Unless a quoting `\',
`"', `'' or ``' appears in word variable and command substitution
is performed on the intervening lines, allowing `\' to quote `$',
`\' and ``'. Commands which are substituted have all blanks,
tabs, and newlines preserved, except for the final newline which
is dropped. The resultant text is placed in an anonymous
temporary file which is given to the command as standard input.
> name
>! name
>& name
>&! name
The file name is used as standard output. If the file does not
exist then it is created; if the file exists, its is truncated,
its previous contents being lost.
If the variable noclobber is set, then the file must not exist or
be a character special file (e.g. a terminal or `/dev/null') or an
error results. This helps prevent accidental destruction of
files. In this case the `!' forms can be used and suppress this
check.
The forms involving `&' route the diagnostic output into the
specified file as well as the standard output. Name is expanded
in the same way as `<' input filenames are.
>> name
>>& name
>>! name
>>&! name
Uses file name as standard output like `>' but places output at
the end of the file. If the variable noclobber is set, then it is
an error for the file not to exist unless one of the `!' forms is
given. Otherwise similar to `>'.
A command receives the environment in which the shell was invoked as
modified by the input-output parameters and the presence of the command
in a pipeline. Thus, unlike some previous shells, commands run from a
file of shell commands have no access to the text of the commands by
default; rather they receive the original standard input of the shell.
The `<<' mechanism should be used to present inline data. This permits
shell command scripts to function as components of pipelines and allows
the shell to block read its input. Note that the default standard
input for a command run detached is not modified to be the empty file
`/dev/null'; rather the standard input remains as the original standard
input of the shell. If this is a terminal and if the process attempts
to read from the terminal, then the process will block and the user
will be notified (see Jobs above).
Diagnostic output may be directed through a pipe with the standard
output. Simply use the form `|&' rather than just `|'.
Expressions
A number of the builtin commands (to be described subsequently) take
expressions, in which the operators are similar to those of C, with the
same precedence. These expressions appear in the @, exit, if, and
while commands. The following operators are available:
|| && | ^ & == != =~ !~ <= >= < > << >> + - * /
% ! ~ ( )
Here the precedence increases to the right, `==' `!=' `=~' and `!~',
`<=' `>=' `<' and `>', `<<' and `>>', `+' and `-', `*' `/' and `%'
being, in groups, at the same level. The `==' `!=' `=~' and `!~'
operators compare their arguments as strings; all others operate on
numbers. The operators `=~' and `!~' are like `!=' and `==' except
that the right hand side is a pattern (containing, e.g. `*'s, `?'s and
instances of `[...]') against which the left hand operand is matched.
This reduces the need for use of the switch statement in shell scripts
when all that is really needed is pattern matching.
Strings which begin with `0' are considered octal numbers. Null or
missing arguments are considered `0'. The result of all expressions
are strings, which represent decimal numbers. It is important to note
that no two components of an expression can appear in the same word;
except when adjacent to components of expressions which are
syntactically significant to the parser (`&' `|' `<' `>' `(' `)') they
should be surrounded by spaces.
Also available in expressions as primitive operands are command
executions enclosed in `{' and `}' and file enquiries of the form `-l
name' where l is one of:
r read access
w write access
x execute access
e existence
o ownership
z zero size
f plain file
d directory
The specified name is command and filename expanded and then tested to
see if it has the specified relationship to the real user. If the file
does not exist or is inaccessible then all enquiries return false, i.e.
`0'. Command executions succeed, returning true, i.e. `1', if the
command exits with status 0, otherwise they fail, returning false, i.e.
`0'. If more detailed status information is required then the command
should be executed outside of an expression and the variable status
examined.
Control flow
The shell contains a number of commands which can be used to regulate
the flow of control in command files (shell scripts) and (in limited
but useful ways) from terminal input. These commands all operate by
forcing the shell to reread or skip in its input and, due to the
implementation, restrict the placement of some of the commands.
The foreach, switch, and while statements, as well as the if-then-else
form of the if statement require that the major keywords appear in a
single simple command on an input line as shown below.
If the shell's input is not seekable, the shell buffers up input
whenever a loop is being read and performs seeks in this internal
buffer to accomplish the rereading implied by the loop. (To the extent
that this allows, backward goto's will succeed on non-seekable inputs.)
Builtin commands
Builtin commands are executed within the shell. If a builtin command
occurs as any component of a pipeline except the last then it is
executed in a subshell.
alias
alias name
alias name wordlist
The first form prints all aliases. The second form prints the
alias for name. The final form assigns the specified wordlist as
the alias of name; wordlist is command and filename substituted.
Name is not allowed to be alias or unalias.
alloc
Shows the amount of dynamic memory acquired, broken down into used
and free memory. With an argument shows the number of free and
used blocks in each size category. The categories start at size 8
and double at each step. This command's output may vary across
system types, since different systems may use a different memory
allocator.
bg
bg %job ...
Puts the current or specified jobs into the background, continuing
them if they were stopped.
break
Causes execution to resume after the end of the nearest enclosing
foreach or while. The remaining commands on the current line are
executed. Multi-level breaks are thus possible by writing them
all on one line.
breaksw
Causes a break from a switch, resuming after the endsw.
case label:
A label in a switch statement as discussed below.
cd
cd name
chdir
chdir name
Change the shell's working directory to directory name. If no
argument is given then change to the home directory of the user.
If name is not found as a subdirectory of the current directory
(and does not begin with `/', `./' or `../'), then each component
of the variable cdpath is checked to see if it has a subdirectory
name. Finally, if all else fails but name is a shell variable
whose value begins with `/', then this is tried to see if it is a
directory.
continue
Continue execution of the nearest enclosing while or foreach. The
rest of the commands on the current line are executed.
default:
Labels the default case in a switch statement. The default should
come after all case labels.
dirs
Prints the directory stack; the top of the stack is at the left,
the first directory in the stack being the current directory.
echo wordlist
echo -n wordlist
The specified words are written to the shells standard output,
separated by spaces, and terminated with a newline unless the -n
option is specified.
else
end
endif
endsw
See the description of the foreach, if, switch, and while
statements below.
eval arg ...
(As in sh(1).) The arguments are read as input to the shell and
the resulting command(s) executed in the context of the current
shell. 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 using
eval.
exec command
The specified command is executed in place of the current shell.
exit
exit(expr)
The shell exits either with the value of the status variable
(first form) or with the value of the specified expr (second
form).
fg
fg %job ...
Brings the current or specified jobs into the foreground,
continuing them if they were stopped.
foreach name (wordlist)
...
end
The variable name is successively set to each member of wordlist
and the sequence of commands between this command and the matching
end are executed. (Both foreach and end must appear alone on
separate lines.)
The builtin command continue may be used to continue the loop
prematurely and the builtin 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. If you make a mistake typing in a loop at
the terminal you can rub it out.
glob wordlist
Like echo but no `\' escapes are recognized and words are
delimited by null characters in the output. Useful for programs
which wish to use the shell to filename expand a list of words.
goto word
The specified word is filename and command expanded to yield a
string of the form `label'. The shell rewinds its input as much
as possible and searches for a line of the form `label:' possibly
preceded by blanks or tabs. Execution continues after the
specified line.
hashstat
Print a statistics line indicating how effective the internal hash
table has been at locating commands (and avoiding exec's). An
exec is attempted for each component of the path where the hash
function indicates a possible hit, and in each component which
does not begin with a `/'.
history
history n
history -r n
history -h n
Displays the history event list; if n is given only the n most
recent events are printed. The -r option reverses the order of
printout to be most recent first rather than oldest first. The -h
option causes the history list to be printed without leading
numbers. This is used to produce files suitable for sourceing
using the -h option to source.
if (expr) command
If the specified expression evaluates true, then 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. Input/output
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 the specified expr is true then the commands to the first else
are executed; otherwise if expr2 is true then the commands to the
second else are executed, etc. Any number of else-if pairs are
possible; only one endif is needed. The else part is likewise
optional. (The words else and endif must appear at the beginning
of input lines; the if must appear alone on its input line or
after an else.)
jobs
jobs -l
Lists the active jobs; given the -l options lists process id's in
addition to the normal information.
kill %job
kill -sig %job ...
kill pid
kill -sig pid ...
kill -l
Sends either the TERM (terminate) signal or the specified signal
to the specified jobs or processes. Signals are either given by
number or by names (as given in <signal.h>, stripped of the prefix
``SIG''). The signal names are listed by ``kill -l''. There is
no default, saying just `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 will be sent a CONT (continue)
signal as well.
limit
limit resource
limit resource maximum-use
limit -h
limit -h resource
limit -h resource maximum-use
Limits the consumption by the current process and each process it
creates to not individually exceed maximum-use on the specified
resource. If no maximum-use is given, then the current limit is
printed; if no resource is given, then all limitations are given.
If the -h flag is given, the hard limits are used instead of the
current limits. The hard limits impose a ceiling on the values of
the current limits. Only the super-user may raise the hard
limits, but a user may lower or raise the current limits within
the legal range.
Resources controllable currently include cputime (the maximum
number of cpu-seconds to be used by each process), filesize (the
largest single file which can be created), datasize (the maximum
growth of the data+stack region via sbrk(2) beyond the end of the
program text), stacksize (the maximum size of the automatically-
extended stack region), and coredumpsize (the size of the largest
core dump that will be created).
The maximum-use may be given as a (floating point or integer)
number followed by a scale factor. For all limits other than
cputime the default scale is `k' or `kilobytes' (1024 bytes); a
scale factor of `m' or `megabytes' may also be used. For cputime
the default scaling is `seconds', while `m' for minutes or `h' for
hours, or a time of the form `mm:ss' giving minutes and seconds
may be used.
For both resource names and scale factors, unambiguous prefixes of
the names suffice.
login
Terminate a login shell, replacing it with an instance of
/bin/login. This is one way to log off, included for
compatibility with sh(1).
logout
Terminate a login shell. Especially useful if ignoreeof is set.
nice
nice +number
nice command
nice +number command
The first form sets the scheduling priority for this shell to 4.
The second form sets the priority to the given number. The final
two forms run command at priority 4 and number respectively. The
greater the number, the less cpu the process will get. The super-
user may specify negative priority by using `nice -number ...'.
Command is always executed in a sub-shell, and the restrictions
placed on commands in simple if statements apply.
nohup
nohup command
The first form can be used in shell scripts to cause hangups to be
ignored for the remainder of the script. The second form causes
the specified command to be run with hangups ignored. All
processes detached with `&' are effectively nohup'ed.
notify
notify %job ...
Causes the shell to notify the user asynchronously when the status
of the current or specified jobs changes; normally notification is
presented before a prompt. This is automatic if the shell
variable notify is set.
onintr
onintr -
onintr label
Control the action of the shell on interrupts. The first form
restores the default action of the shell on interrupts which is to
terminate shell scripts or to return to the terminal command input
level. The second form `onintr -' causes all interrupts to be
ignored. The final form causes the shell to execute a `goto
label' when an interrupt is received or a child process terminates
because it was interrupted.
In any case, if the shell is running detached and interrupts are
being ignored, all forms of onintr have no meaning and interrupts
continue to be ignored by the shell and all invoked commands.
popd
popd +n
Pops the directory stack, returning to the new top directory.
With an argument `+n' discards the nth entry in the stack. The
elements of the directory stack are numbered from 0 starting at
the top.
pushd
pushd name
pushd +n
With no arguments, pushd exchanges the top two elements of the
directory stack. Given a name argument, pushd changes to the new
directory (ala cd) and pushes the old current working directory
(as in csw) onto the directory stack. With a numeric argument,
rotates the nth argument of the directory stack around to be the
top element and changes to it. The members of the directory stack
are numbered from the top starting at 0.
rehash
Causes the internal hash table of the contents of the directories
in the path variable to be recomputed. This is needed if new
commands are added to directories in the path while you are logged
in. This should only be necessary if you add commands to one of
your own directories, or if a systems programmer changes the
contents of one of the system directories.
repeat count command
The specified command which is subject to the same restrictions as
the command in the one line if statement above, is executed count
times. I/O redirections occur exactly once, even if count is 0.
set
set name
set name=word
set name[index]=word
set name=(wordlist)
The first form of the command shows the value of all shell
variables. Variables which have other than a single word as value
print as a parenthesized word list. The second form sets name to
the null string. The third form sets name to the single word.
The fourth form sets the index'th component of name to word; this
component must already exist. The final form sets name to the
list of words in wordlist. In all cases the value is command and
filename expanded.
These arguments may be repeated to set multiple values in a single
set command. Note however, that variable expansion happens for
all arguments before any setting occurs.
setenv
setenv name value
setenv name
The first form lists all current environment variables. The last
form sets the value of environment variable name to be value, a
single string. The second form sets name to an empty string. The
most commonly used environment variable 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.
shift
shift variable
The members of argv are shifted to the left, discarding argv[1].
It is an error for argv not to be set or to have less than one
word as value. The second form performs the same function on the
specified variable.
source name
source -h name
The shell reads commands from name. Source commands may be
nested; if they are nested too deeply the shell may run out of
file descriptors. An error in a source at any level terminates
all nested source commands. Normally input during source commands
is not placed on the history list; the -h option causes the
commands to be placed in the history list without being executed.
stop
stop %job ...
Stops the current or specified job which is executing in the
background.
suspend
Causes the shell to stop 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(1).
switch (string)
case str1:
...
breaksw
...
default:
...
breaksw
endsw
Each case label is successively matched, against the specified
string which is first command and filename expanded. The file
metacharacters `*', `?' and `[...]' may be used in the case
labels, which are variable expanded. If none of the labels match
before a `default' label is found, then the execution begins after
the default label. Each case label and the default label must
appear at the beginning of a line. The command breaksw causes
execution to continue after the endsw. Otherwise control may fall
through case labels and default labels as in C. If no label
matches and there is no default, execution continues after the
endsw.
time
time command
With no argument, a summary of time used by this shell and its
children is printed. If arguments are given the specified simple
command is timed and a time summary as described under the time
variable is printed. If necessary, an extra shell is created to
print the time statistic when the command completes.
umask
umask value
The file creation mask is displayed (first form) or set to the
specified value (second form). The mask is given in octal.
Common values for the mask are 002 giving all access to the group
and read and execute access to others or 022 giving all access
except no write access for users in the group or others.
unalias pattern
All aliases whose names match the specified pattern are discarded.
Thus all aliases are removed by `unalias *'. It is not an error
for nothing to be unaliased.
unhash
Use of the internal hash table to speed location of executed
programs is disabled.
unlimit
unlimit resource
unlimit -h
unlimit -h resource
Removes the limitation on resource. If no resource is specified,
then all resource limitations are removed. If -h is given, the
corresponding hard limits are removed. Only the super-user may do
this.
unset pattern
All variables whose names match the specified pattern are removed.
Thus all variables are removed by `unset *'; this has noticeably
distasteful side-effects. It is not an error for nothing to be
unset.
unsetenv pattern
Removes all variables whose name match the specified pattern from
the environment. See also the setenv command above and
printenv(1).
wait
All background jobs are waited for. It the shell is interactive,
then an interrupt can disrupt the wait, at which time the shell
prints names and job numbers of all jobs known to be outstanding.
while (expr)
...
end
While the specified expression evaluates non-zero, the commands
between the while and the matching end are evaluated. Break and
continue may be used to terminate or continue the loop
prematurely. (The while and end must appear alone on their input
lines.) Prompting occurs here the first time through the loop as
for the foreach statement if the input is a terminal.
%job
Brings the specified job into the foreground.
%job &
Continues the specified job in the background.
@
@ name = expr
@ name[index] = expr
The first form prints the values of all the shell variables. The
second form sets the specified name to the value of expr. If the
expression contains `<', `>', `&' or `|' then at least this part
of the expression must be placed within `(' `)'. The third form
assigns the value of expr to the index'th argument of name. Both
name and its index'th component must already exist.
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
which would otherwise be single words.
Special postfix `++' and `--' operators increment and decrement
name respectively, i.e. `@ i++'.
Pre-defined and environment variables
The following variables have special meaning to the shell. Of these,
argv, cwd, home, path, prompt, shell and status are always set by the
shell. Except for cwd and status this setting occurs only at
initialization; these variables will not then be modified unless this
is done explicitly by the user.
This shell copies the environment variable USER into the variable user,
TERM into term, and HOME into home, and copies these back into the
environment whenever the normal shell variables are reset. The
environment variable PATH is likewise handled; it is not necessary to
worry about its setting other than in the file .cshrc as inferior csh
processes will import the definition of path from the environment, and
re-export it if you then change it.
argv Set to the arguments to the shell, it is from this
variable that positional parameters are substituted,
i.e. `$1' is replaced by `$argv[1]', etc.
cdpath Gives a list of alternate directories searched to find
subdirectories in chdir commands.
cwd The full pathname of the current directory.
echo Set when the -x command line option is given. Causes
each command and its arguments to be echoed just before
it is executed. For non-builtin commands all expansions
occur before echoing. Builtin commands are echoed
before command and filename substitution, since these
substitutions are then done selectively.
filec Enable file name completion.
histchars Can be given a string value to change the characters
used in history substitution. The first character of
its value is used as the history substitution character,
replacing the default character !. The second character
of its value replaces the character ↑ in quick
substitutions.
history Can be given a numeric value to control the size of the
history list. Any command which has been referenced in
this many events will not be discarded. Too large
values of history may run the shell out of memory. The
last executed command is always saved on the history
list.
home The home directory of the invoker, initialized from the
environment. The filename expansion of `~' refers to
this variable.
ignoreeof If set the shell ignores end-of-file from input devices
which are terminals. This prevents shells from
accidentally being killed by control-D's.
mail The files where the shell checks for mail. This is done
after each command completion which will result in a
prompt, if a specified interval has elapsed. The shell
says `You have new mail.' if the file exists with an
access time not greater than its modify time.
If the first word of the value of mail is numeric it
specifies a different mail checking interval, in
seconds, than the default, which is 10 minutes.
If multiple mail files are specified, then the shell
says `New mail in name' when there is mail in the file
name.
noclobber As described in the section on Input/output,
restrictions are placed on output redirection to insure
that files are not accidentally destroyed, and that `>>'
redirections refer to existing files.
noglob If set, filename expansion is inhibited. This is most
useful in shell scripts which are not dealing with
filenames, or after a list of filenames has been
obtained and further expansions are not desirable.
nonomatch If set, it is not an error for a filename expansion to
not match any existing files; rather the primitive
pattern is returned. It is still an error for the
primitive pattern to be malformed, i.e. `echo [' still
gives an error.
notify If set, the shell notifies asynchronously of job
completions. The default is to rather present job
completions just before printing a prompt.
path Each word of the path variable specifies a directory in
which commands are to be sought for execution. A null
word specifies the current directory. If there is no
path variable then only full path names will execute.
The usual search path is `.', `/bin' and `/usr/bin', but
this may vary from system to system. For the super-user
the default search path is `/etc', `/bin' and
`/usr/bin'. A shell which is given neither the -c nor
the -t option will normally hash the contents of the
directories in the path variable after reading .cshrc,
and each time the path variable is reset. If new
commands are added to these directories while the shell
is active, it may be necessary to give the rehash or the
commands may not be found.
prompt The string which is printed before each command is read
from an interactive terminal input. If a `!' appears in
the string it will be replaced by the current event
number unless a preceding `\' is given. Default is `%
', or `# ' for the super-user.
savehist is given a numeric value to control the number of
entries of the history list that are saved in ~/.history
when the user logs out. Any command which has been
referenced in this many events will be saved. During
start up the shell sources ~/.history into the history
list enabling history to be saved across logins. Too
large values of savehist will slow down the shell during
start up.
shell The file in which the shell resides. This is used in
forking shells to interpret files which have execute
bits set, but which are not executable by the system.
(See the description of Non-builtin Command Execution
below.) Initialized to the (system-dependent) home of
the shell.
status The status returned by the last command. If it
terminated abnormally, then 0200 is added to the status.
Builtin commands which fail return exit status `1', all
other builtin commands set status `0'.
time Controls automatic timing of commands. If set, then any
command which takes more than this many cpu seconds will
cause a line giving user, system, and real times and a
utilization percentage which is the ratio of user plus
system times to real time to be printed when it
terminates.
verbose Set by the -v command line option, causes the words of
each command to be printed after history substitution.
Non-builtin command execution
When a command to be executed is found to not be a builtin command the
shell attempts to execute the command via execve(2). Each word in the
variable path names a directory from which the shell will attempt to
execute the command. If it is given neither a -c nor a -t option, the
shell will hash the names in these directories into an internal table
so that it will only try an exec in a directory if there is a
possibility that the command resides there. This greatly speeds
command location when a large number of directories are present in the
search path. If this mechanism has been turned off (via unhash), or if
the shell was given a -c or -t argument, and in any case for each
directory component of path which does not begin with a `/', the shell
concatenates with the given command name to form a path name of a file
which it then attempts to execute.
Parenthesized commands are always executed in a subshell. Thus `(cd ;
pwd) ; pwd' prints the home directory; leaving you where you were
(printing this after the home directory), while `cd ; pwd' leaves you
in the home directory. Parenthesized commands are most often used to
prevent chdir from affecting the current shell.
If the file has execute permissions but is not an executable binary to
the system, then it is assumed to be a file containing shell commands
and a new shell is spawned to read it.
If there is an alias for shell then the words of the alias will be
prepended to the argument list to form the shell command. The first
word of the alias should be the full path name of the shell (e.g.
`$shell'). Note that this is a special, late occurring, case of alias
substitution, and only allows words to be prepended to the argument
list without modification.
Argument list processing
If argument 0 to the shell is `-' then this is a login shell. The flag
arguments are interpreted as follows:
-b This flag forces a ``break'' from option processing, causing any
further shell arguments to be treated as non-option arguments.
The remaining arguments will not be interpreted as shell options.
This may be used to pass options to a shell script without
confusion or possible subterfuge. The shell will not run a set-
user ID script without this option.
-c Commands are read from the (single) following argument which must
be present. Any remaining arguments are placed in argv.
-e The shell exits if any invoked command terminates abnormally or
yields a non-zero exit status.
-f The shell will start faster, because it will neither search for
nor execute commands from the file `.cshrc' in the invoker's home
directory.
-i The shell is interactive and prompts for its top-level input, even
if it appears to not be a terminal. Shells are interactive
without this option if their inputs and outputs are terminals.
-n Commands are parsed, but not executed. This aids in syntactic
checking of shell scripts.
-s Command input is taken from the standard input.
-t A single line of input is read and executed. A `\' may be used to
escape the newline at the end of this line and continue onto
another line.
-v Causes the verbose variable to be set, with the effect that
command input is echoed after history substitution.
-x Causes the echo variable to be set, so that commands are echoed
immediately before execution.
-V Causes the verbose variable to be set even before `.cshrc' is
executed.
-X Is to -x as -V is to -v.
After processing of flag arguments, if arguments remain but none of the
-c, -i, -s, or -t options was given, the first argument is taken as the
name of a file of commands to be executed. The shell opens this file,
and saves its name for possible resubstitution by `$0'. Since many
systems use either the standard version 6 or version 7 shells whose
shell scripts are not compatible with this shell, the shell will
execute such a `standard' shell if the first character of a script is
not a `#', i.e. if the script does not start with a comment. Remaining
arguments initialize the variable argv.
Signal handling
The shell normally ignores quit signals. Jobs running detached (either
by `&' or the bg or %... & commands) are immune to signals generated
from the keyboard, including hangups. Other signals have the values
which the shell inherited from its parent. The shells handling of
interrupts and terminate signals in shell scripts can be controlled by
onintr. Login shells catch the terminate signal; otherwise this signal
is passed on to children from the state in the shell's parent. In no
case are interrupts allowed when a login shell is reading the file
`.logout'.
EXTENDED C-SHELL FEATURES
The version of the C-shell supplied on the NeXT computer includes
several entensions, such as intra-command line editing, a kill buffer,
multi-line named keyboard macros which can be automatically saved and
restored, convenient access to the history list, and user settable key
bindings. A summary of the currently available functions and their
default key bindings is given in the BINDINGS section below. In most
cases the functionality will be apparent from the names of the routines
in the list.
The shell's editing mode is determined by the value of the shell
editmode variable which users should set to emacs in their .cshrc files
If editmode is not set, then the shell will run in "dumb" mode. It is
possible to set the mode after the shell starts up; so if you find
yourself in "dumb" mode, you can alter the situation without having to
log out and log in again. Setting the editmode variable has two
important side effects: (1) it causes the key bindings to be
reevaluated, and (2) it sets the EDITMODE environment variable. The
latter has no effect within the shell; so users should not set the
environment variable directly in hopes of altering the editing mode.
Terminal control capabilities are extracted from the user's termcap
file (usually /etc/termcap), using the value of the shell variable term
-- not the environment variable TERM -- as the terminal type. If term
is undefined, unknown, or if the associated termcap definition is
inadequate, a warning will be displayed and most, or all, of the
editing features of the shell will be disabled. It is the user's
responsibility to make sure that term is set to an appropriate value
before the editmode variable is set to emacs. Usually this should be
done in the .cshrc file. If editing is disabled because term is not
properly set when the shell starts up, simply setting term to the
proper value will normally cause the shell editor to be re-enabled.
NB: Setting the shell variable term causes the environment variable
TERM to be set to the same value. For information on controlling the
bell, see the DIAGNOSTICS section.
There is a new command in this shell, bind-to-key, which allows the
functions listed in the BINDINGS section below, and also user defined
keyboard macros, to be bound to keys. The form of the command is
bind-to-key function key ...
where function is one of the function names from the list or else the
single character name of a keyboard macro and where key is a quoted
string designating a key sequence. Control characters in the key
designation should not be entered literally, but should be indicated by
the prefix "\^", e.g. "\^X". Similarly, escape is indicated by "\e".
A literal slash is "\\". Escape and control-X are the only legitimate
"prefix" characters. The following mnemonics should be used: "\t" for
tab, "\^?" for rubout, "\n" for newline, and "\r" for return. Since
the shell converts returns to newlines it is probably unwise to alter
the binding of newline.
During editor initialization the shell will read a file named .bindings
in the user's home directory. If you regularly want certain non-
default key bindings to be effective, put the appropriate bind-to-key
commands in your ~/.bindings file. NB: The bind-to-key commands would
work if placed in your ~/.cshrc file, but they will be more useful (in
the future) if they are in the ~/.bindings file.
Invocation of the history mechanism with "!" either causes the matched
command to be inserted on the command line for editing before execution
or immediatedly executes the command. This is controlled by the shell
variable edithist, which is automatically set, when the shell variable
editmode is set, thereby allowing editing of previous commands invoked
by the history mechanism. This feature may be turned off with the
command "unset edithist", which may be placed in the user's .cshrc
file.
HOW TO ENABLE THE EXTENDED C-SHELL FEATURES
To enable the extended C-Shell features, put the line:
set editmode = emacs
in the .cshrc file in your home directory. If you don't have such a
file, create one and add the line to the end. Log out and log in again
and you will be using the new shell.
BINDINGS
The following functions and default key bindings are currently
implemented.
Emacs Function Name Remark
^B Backspace
ESC-b BackwardWord
^A BeginningOfLine
^L ClearScreen
DefaultBinding
ESC-n DefineNamedMacro name macro
^D DeleteCurrentChar
^H DeletePreviousChar
ESC-d DeleteWord after cursor
EndOfFile exit shell
^E EndOfLine
EraseLine kills whole line
ESC-h EraseWord before cursor
ESC-e ExecuteNamedMacro
ESC-x ExecuteNamedMacro
^X-e ExecuteUnNamedMacro
ESC-ESC FilenameExpansion
ESC-l FilenameList
^F ForwardChar
ESC-f ForwardWord
^W KillRegion to kill buffer
^K KillToEOL to kill buffer
IncrementalSearchForward
IncrementalSearchReverse
InsertChar self insert
^V InsertLiteralChar
^X^R LoadMacroFile
^N NextHistEntry wraps around
^P PreviousHistEntry wraps around
^R Redisplay redraws line
^U Repetition greater than 0
^M,^J Return
^X^S SaveMacroFile
^@ SetMark default mark at BOL
SearchReverse look for next char
SearchForward look for next char
^Q StartFlow (see FLOW CONTROL)
^X-( StartRemembering begin a macro
^S StopFlow (see FLOW CONTROL)
^X-) StopRemembering end a macro
^I Tab inserts 8 spaces
^T TransposeChars before cursor
^Y YankKillBuffer no kill ring
Users may change the bindings of functions to keys by means of the
shell bind-to-key command. These commands may be stored in a file
named .bindings in the users home directory and will then be read by
the shell when the editor is initialized.
NB: The shell variable bindings is no longer being supported and will
become ineffective in a future release. Before that happens users
should convert to using the ~/.bindings file.
FLOW CONTROL
Flow control is handled by the terminal driver, not by the shell. The
terminal driver normally interprets ^S and ^Q as a signal to
respectively stop and restart output to the terminal. By default, the
shell does not override these "bindings", but the user may override
them by rebinding ^S or ^Q to functions other than StopFlow and
StartFlow.
The functions StopFlow and StartFlow can only be usefully bound to the
keys that the terminal driver interprets as performing the
corresponding flow control functions. In other words, you cannot
simply bind these functions to other keys in order to have them perform
the flow control operations normally provided by ^S and ^Q.
KEYBOARD MACROS
Keyboard macros can be used to simplify repetitive operations and
reduce typing lengthy commands. For example, the following lines
illustrate how to create a macro to startup Emacs and have it run the
shell inside a buffer:
% ^X(emacs -eshell
% ^X)
Notice that this is a multi-line macro, since it contains an embedded
newline. The user can give this macro a single character name, e.g.
"e", as follows:
% \ene (escape-n-e).
The macro may then be executed by typing "\exe". It can also be bound
to a key using the bind-to-key command. Macros can be saved in files
and can be reloaded automatically when the shell starts up.
Macro Creation
To create a new unnamed macro, use the StartRemembering function
which is bound by default to ^X(. Subsequent keystrokes, until
the StopRemembering,^X), function is executed, are remembered as
an "unnamed" keyboard macro. It can contain at most 1024
characters. You are not allowed to begin creating another macro
during macro creation, but it is okay to execute other macros,
provided loops aren't created. The unnamed macro can be
executed using the ExecuteUnNamedMacro function, bound to ^Xe.
There is only one unnamed macro.
Named Macros
Users can have up to 128 named macros. To define such a macro,
first create an unnamed macro as above and then give it a name
by executing the DefineNamedMacro function, bound to \en
(escape-n). The function takes a single character argument
which will be the name of the macro. Any previous macro with
that same name will be destroyed.
Macro Execution
To execute a named macro simply use the ExecuteNamedMacro
function, bound to \ex, and give it the name of the macro to be
executed. Named macros can also be bound to keys using the
builtin cshell command bind-to-key.
Macro Files
Named keyboard macros can be saved in files and loaded from
files. To save the named macros in a file simply type the
filename on the command line (by itself) and then execute the
SaveMacroFile function bound to ^X^S. To read a file of
previously saved macros type the filename on the command line
and execute the LoadMacroFile function bound to ^X^R. Success
in each case is indicated by the erasure of the filename. It is
okay to store macros in several different macro files.
NB: It is not advisable to try to edit saved macros!
Autoloading and AutoSaving Macros
If the shell variable macrofiles is assigned (in the user's
.cshrc file) the names of one or more files of saved keyboard
macros, then those macro files will be automatically loaded when
the shell starts up. Similarly, the variable savemacros can be
assigned the name of a (single) file in which all named macros
will be saved when the user logs out.
SEARCHING
NB: The names of the incremental search functions have changed since
earlier releases of this shell.
Four search functions are available to the user, but are not bound (by
default) to keys. If you want to use them, use the cshell bind-to-key
command to bind them to keys.
IncrementalSearchForward
When the user executes this function he is placed in a
read/search loop in which the string to be found is built up
character by character. As each new character is added to the
search string the cursor is placed at the end of the first match
on the command line following the position of the cursor when
the function was executed. You can reexecute the search
function while in the loop to cause the cursor to move to
subsequent matches. Type ESC to exit the loop.
IncrementalSearchReverse
This function is similar to IncrementalSearchForward except that
the cursor is placed at the beginning of the first match on the
command line preceding the position of the cursor when the
function was executed.
SearchForward
This function grabs the next character you type and searches for
that character from the position of the cursor to the end of the
command line, leaving the cursor following the first instance of
the character if one is found.
SearchReverse
This function is like SearchForward except that it searches from
where the cursor is to the beginning of the command line.
MISCELLANEOUS
If the shell variable breakchars is assigned a string, then the
characters in that string are used to determine word boundaries. The
default break characters are " ", ",", ^I, /, \, (, ), [, ], {, }, The
user defined break characters are used instead of, not in addition to,
the default list.
AUTHOR
William Joy. Job control and directory stack features first
implemented by J.E. Kulp of I.I.A.S.A, Laxenburg, Austria, with
different syntax than that used now. File name completion code written
by Ken Greer, HP Labs. Command line editor code written by Duane
Williams, Carnegie-Mellon University.
FILES
~/.cshrc Read at beginning of execution by each shell.
~/.login Read by login shell, after `.cshrc' at login.
~/.logout Read by login shell, at logout.
~/.bindings Definitions for non-default key bindings, read during shell editor initialization.
/bin/sh Standard shell, for shell scripts not starting with a `#'.
/tmp/sh* Temporary file for `<<'.
/etc/passwd Source of home directories for `~name'.
LIMITATIONS
Words can be no longer than 1024 characters. The system limits
argument lists to 10240 characters. The number of arguments to a
command which involves filename expansion is limited to 1/6'th the
number of characters allowed in an argument list. Command
substitutions may substitute no more characters than are allowed in an
argument list. To detect looping, the shell restricts the number of
alias substitutions on a single line to 20.
SEE ALSOsh(1), access(2), execve(2), fork(2), killpg(2), pipe(2), sigvec(2),
umask(2), setrlimit(2), wait(2), tty(4), a.out(5), environ(7), `An
introduction to the C shell'
DIAGNOSTICS
Error conditions within the editor functions are usually indicated by
an audible bell. If you prefer a visual signal and your terminal has a
visible bell capability, then you should set the variable visiblebell
in your .cshrc file. If you want an audible bell also, then set both
visiblebell and audiblebell. If you don't want to be told about your
mistakes, you can set the nobell variable.
BUGS
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 (i.e. wrong) as the job may have changed directories
internally.
Shell builtin 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 will then
immediately execute `c'. This is especially noticeable if this
expansion results from an alias. It suffices to place the sequence of
commands in ()'s to force it to a subshell, i.e. `( a ; b ; c )'.
Control over tty output after processes are started is primitive;
perhaps this will inspire someone to work on a good virtual terminal
interface. In a virtual terminal interface much more interesting
things could be done with output control.
Alias substitution is most often used to clumsily simulate shell
procedures; shell procedures should be provided rather than aliases.
Commands within loops, prompted for by `?', are not placed in the
history list. Control structure 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. All and more than one `:' modifier should be allowed on
`$' substitutions.
The shell variable filec is currently ignored; this means that file and
user name completion always takes place. Also, the way the filec
facility is implemented is ugly and expensive.
4th Berkeley Distribution November 11, 1988 CSH(1)