The rest of the flag arguments are interpreted as follows:
After processing of flag arguments, if arguments remain but none of the -c, -i, -s, or -t options were given, the first argument is taken as the name of a file of commands, or ``script'', 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 uses such a `standard' shell to execute a script whose first character is not a `#', i.e. which does not start with a comment.
Remaining arguments are placed in the argv shell variable.
Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or ~/.cshrc on startup.
Commands like stty(1) and tset(1), which need be run only once per login, usually go in one's ~/.login file. Users who need to use the same set of files with both csh(1) and tcsh can have only a ~/.cshrc which checks for the existence of the tcsh shell variable (q.v.) before using tcsh-specific commands, or can have both a ~/.cshrc and a ~/.tcshrc which sources (see the builtin command) ~/.cshrc. The rest of this manual uses `~/.tcshrc' to mean `~/.tcshrc or, if ~/.tcshrc is not found, ~/.cshrc'.
In the normal case, the shell begins reading commands from the terminal, prompting with `> '. (Processing of arguments and the use of the shell to process files containing command scripts are described later.) The shell repeatedly reads a line of command input, breaks it into words, places it on the command history list, parses it and executes each command in the line.
One can log out by typing `^D' on an empty line, `logout' or `login' or via the shell's autologout mechanism (see the autologout shell variable). When a login shell terminates it sets the logout shell variable to `normal' or `automatic' as appropriate, then executes commands from the files /etc/csh.logout and ~/.logout. The shell may drop DTR on logout if so compiled; see the version shell variable.
The names of the system login and logout files vary from system to system for compatibility with different csh(1) variants; see FILES.
The shell always binds the arrow keys (as defined in the TERMCAP environment variable) to
- down
- down-history
- up
- up-history
- left
- backward-char
- right
- forward-char
unless doing so would alter another single-character binding. One can set the arrow key escape sequences to the empty string with settc to prevent these bindings. The ANSI/VT100 sequences for arrow keys are always bound.
Other key bindings are, for the most part, what Emacs and vi(1) users would expect and can easily be displayed by bindkey, so there is no need to list them here. Likewise, bindkey can list the editor commands with a short description of each.
Note that editor commands do not have the same notion of a ``word'' as does the shell. The editor delimits words with any non-alphanumeric characters not in the shell variable wordchars, while the shell recognizes only whitespace and some of the characters with special meanings to it, listed under Lexical structure.
Completion works anywhere in the line, not just at the end; completed text pushes the rest of the line to the right. Completion in the middle of a word often results in leftover characters to the right of the cursor which need to be deleted.
Commands and variables can be completed in much the same way. For example, typing `em[tab]' would complete `em' to `emacs' if emacs were the only command on your system beginning with `em'. Completion can find a command in any directory in path or if given a full pathname. Typing `echo $ar[tab]' would complete `$ar' to `$argv' if no other variable began with `ar'.
The shell parses the input buffer to determine whether the word you want to complete should be completed as a filename, command or variable. The first word in the buffer and the first word following `;', `|', `|&', `&&' or `||' is considered to be a command. A word beginning with `$' is considered to be a variable. Anything else is a filename. An empty line is `completed' as a filename.
You can list the possible completions of a word at any time by typing `^D' to run the delete-char-or-list-or-eof editor command. The shell lists the possible completions using the ls-F builtin (q.v.) and reprints the prompt and unfinished command line, for example:
If the autolist shell variable is set, the shell lists the remaining choices (if any) whenever completion fails:
If autolist is set to `ambiguous', choices are listed only when completion fails and adds no new characters to the word being completed.
A filename to be completed can contain variables, your own or others' home directories abbreviated with `~' (see Filename substitution) and directory stack entries abbreviated with `=' (see Directory stack substitution). For example,
or
Note that variables can also be expanded explicitly with the expand-variables editor command.
delete-char-or-list-or-eof only lists at the end of the line; in the middle of a line it deletes the character under the cursor and on an empty line it logs one out or, if ignoreeof is set, does nothing. `M-^D', bound to the editor command list-choices, lists completion possibilities anywhere on a line, and list-choices (or any one of the related editor commands which do or don't delete, list and/or log out, listed under delete-char-or-list-or-eof) can be bound to `^D' with the bindkey builtin command if so desired.
The complete-word-fwd and complete-word-back editor commands (not bound to any keys by default) can be used to cycle up and down through the list of possible completions, replacing the current word with the next or previous word in the list.
The shell variable fignore can be set to a list of suffixes to be ignored by completion. Consider the following:
`main.c~' and `main.o' are ignored by completion (but not listing), because they end in suffixes in fignore. Note that a `\' was needed in front of `~' to prevent it from being expanded to home as described under Filename substitution. fignore is ignored if only one completion is possible.
If the complete shell variable is set to `enhance', completion 1) ignores case and 2) considers periods, hyphens and underscores (`.', `-' and `_') to be word separators and hyphens and underscores to be equivalent. If you had the following files
and typed `mail -f c.l.c[tab]', it would be completed to `mail -f comp.lang.c', and ^D would list `comp.lang.c' and `comp.lang.c++'. `mail -f c..c++[^D]' would list `comp.lang.c++' and `comp.std.c++'. Typing `rm a--file[^D]' in the following directory
would list all three files, because case is ignored and hyphens and underscores are equivalent. Periods, however, are not equivalent to hyphens or underscores.
Completion and listing are affected by several other shell variables: recexact can be set to complete on the shortest possible unique match, even if more typing might result in a longer match:
just beeps, because `fo' could expand to `fod' or `foo', but if we type another `o',
the completion completes on `foo', even though `food' and `foonly' also match. autoexpand can be set to run the expand-history editor command before each completion attempt, autocorrect can be set to spelling-correct the word to be completed (see Spelling correction) before each completion attempt and correct can be set to complete commands automatically after one hits `return'. matchbeep can be set to make completion beep or not beep in a variety of situations, and nobeep can be set to never beep at all. nostat can be set to a list of directories and/or patterns which match directories to prevent the completion mechanism from stat(2)ing those directories. listmax and listmaxrows can be set to limit the number of items and rows (respectively) that are listed without asking first. recognize_only_executables can be set to make the shell list only executables when listing commands, but it is quite slow.
Finally, the complete builtin command can be used to tell the shell how to complete words other than filenames, commands and variables. Completion and listing do not work on glob-patterns (see Filename substitution), but the list-glob and expand-glob editor commands perform equivalent functions for glob-patterns.
Individual words can be spelling-corrected with the spell-word editor command (usually bound to M-s and M-S) and the entire input buffer with spell-line (usually bound to M-$). The correct shell variable can be set to `cmd' to correct the command name or `all' to correct the entire line each time return is typed, and autocorrect can be set to correct the word to be completed before each completion attempt.
When spelling correction is invoked in any of these ways and the shell thinks that any part of the command line is misspelled, it prompts with the corrected line:
One can answer `y' or space to execute the corrected line, `e' to leave the uncorrected command in the input buffer, `a' to abort the command as if `^C' had been hit, and anything else to execute the original line unchanged.
Spelling correction recognizes user-defined completions (see the complete builtin command). If an input word in a position for which a completion is defined resembles a word in the completion list, spelling correction registers a misspelling and suggests the latter word as a correction. However, if the input word does not match any of the possible completions for that position, spelling correction does not register a misspelling.
Like completion, spelling correction works anywhere in the line, pushing the rest of the line to the right and possibly leaving extra characters to the right of the cursor.
Beware: spelling correction is not guaranteed to work the way one intends, and is provided mostly as an experimental feature. Suggestions and improvements are welcome.
The character or characters to which each command is bound by default is given in parentheses. `^character' means a control character and `M-character' a meta character, typed as escape-character on terminals without a meta key. Case counts, but commands which are bound to letters by default are bound to both lower- and uppercase letters for convenience.
- ^W
- Appends the rest of the word under the cursor to the search pattern.
- delete (or any character bound to backward-delete-char)
- Undoes the effect of the last character typed and deletes a character from the search pattern if appropriate.
- ^G
- If the previous search was successful, aborts the entire search. If not, goes back to the last successful search.
- escape
- Ends the search, leaving the current line in the input buffer.
Any other character not bound to self-insert-command terminates the search, leaving the current line in the input buffer, and is then interpreted as normal input. In particular, a carriage return causes the current line to be executed. Emacs mode only. See also i-search-fwd and history-search-backward.
When the shell's input is not a terminal, the character `#' is taken to begin a comment. Each `#' and the rest of the input line on which it appears is discarded before further parsing.
A special character (including a blank or tab) may be prevented from having its special meaning, and possibly made part of another word, by preceding it with a backslash (`\') or enclosing it in single (`''), double (`"') or backward (``') quotes. When not otherwise quoted a newline preceded by a `\' is equivalent to a blank, but inside quotes this sequence results in a newline.
Furthermore, all Substitutions (see below) except History substitution can be prevented by enclosing the strings (or parts of strings) in which they appear with single quotes or by quoting the crucial character(s) (e.g. `$' or ``' for Variable substitution or Command substitution respectively) with `\'. History substitutions are quoted in the same way by backslashes but not by single quotes. Strings quoted with double or backward quotes undergo Variable substitution and Command substitution, but other substitutions are prevented.
Text inside single or double quotes becomes a single word (or part of one). Metacharacters in these strings, including blanks and tabs, do not form separate words. Only in one special case (see Command substitution below) can a double-quoted string yield parts of more than one word; single-quoted strings never do. Backward quotes are special: they signal Command substitution (q.v.), which may result in more than one word.
Quoting complex strings, particularly strings which themselves contain quoting characters, can be confusing. Remember that quotes need not be used as they are in human writing! It may be easier to quote not an entire string, but only those parts of the string which need quoting, using different types of quoting to do so if appropriate.
The backslash_quote shell variable (q.v.) can be set to make backslashes always quote `\', `'', and `"'. (+) This may make complex quoting tasks easier, but it can cause syntax errors in csh(1) scripts.
Saved commands are numbered sequentially from 1 and stamped with the time. 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 shell variable.
The shell actually saves history in expanded and literal (unexpanded) forms. If the histlit shell variable is set, commands that display and store history use the literal form.
The history builtin command can print, store in a file, restore and clear the history list at any time, and the savehist and histfile shell variables can be can be set to store the history list automatically on logout and restore it on login.
History substitutions introduce words from the history list into the input stream, 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 `!'. They may begin anywhere in the input stream, but they do not nest. The `!' may be preceded by a `\' 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. The characters used to signal history substitution (`!' and `^') can be changed by setting the histchars shell variable. Any input line which contains a history substitution is printed before it is executed.
A history substitution may have an ``event specification'', which indicates the event from which words are to be taken, a ``word designator'', which selects particular words from the chosen event, and/or a ``modifier'', which manipulates the selected words.
An event specification can be
- n
- A number, referring to a particular event
- -n
- An offset, referring to the event n before the current event
- #
- The current event. This should be used carefully in csh(1), where there is no check for recursion. tcsh allows 10 levels of recursion. (+)
- !
- The previous event (equivalent to `-1')
- s
- The most recent event whose first word begins with the string s
- ?s?
- The most recent event which contains the string s. The second `?' can be omitted if it is immediately followed by a newline.
For example, consider this bit of someone's history list:
The commands are shown with their event numbers and time stamps. The current event, which we haven't typed in yet, is event 13. `!11' and `!-2' refer to event 11. `!!' refers to the previous event, 12. `!!' can be abbreviated `!' if it is followed by `:' (`:' is described below). `!n' refers to event 9, which begins with `n'. `!?old?' also refers to event 12, which contains `old'. Without word designators or modifiers history references simply expand to the entire event, so we might type `!cp' to redo the copy command or `!!|more' if the `diff' output scrolled off the top of the screen.
History references may be insulated from the surrounding text with braces if necessary. For example, `!vdoc' would look for a command beginning with `vdoc', and, in this example, not find one, but `!{v}doc' would expand unambiguously to `vi wumpus.mandoc'. Even in braces, history substitutions do not nest.
(+) While csh(1) expands, for example, `!3d' to event 3 with the letter `d' appended to it, tcsh expands it to the last event beginning with `3d'; only completely numeric arguments are treated as event numbers. This makes it possible to recall events beginning with numbers. To expand `!3d' as in csh(1) say `!\3d'.
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:
- The first (command) word
- n
- The nth argument
- ^
- The first argument, equivalent to `1'
- $
- The last argument
- %
- The word matched by an ?s? search
- x-y
- A range of words
- -y
- Equivalent to `0-y'
- *
- Equivalent to `^-$', but returns nothing if the event contains only 1 word
- x*
- Equivalent to `x-$'
- x-
- Equivalent to `x*', but omitting the last word (`$')
Selected words are inserted into the command line separated by single blanks. For example, the `diff' command in the previous example might have been typed as `diff !!:1.old !!:1' (using `:1' to select the first argument from the previous event) or `diff !-2:2 !-2:1' to select and swap the arguments from the `cp' command. If we didn't care about the order of the `diff' we might have said `diff !-2:1-2' or simply `diff !-2:*'. The `cp' command might have been written `cp wumpus.man !#:1.old', using `#' to refer to the current event. `!n:- hurkle.man' would reuse the first two words from the `nroff' command to say `nroff -man hurkle.man'.
The `:' separating the event specification from the word designator can be omitted if the argument selector begins with a `^', `$', `*', `%' or `-'. For example, our `diff' command might have been `diff !!^.old !!^' or, equivalently, `diff !!$.old !!$'. However, if `!!' is abbreviated `!', an argument selector beginning with `-' will be interpreted as an event specification.
A history reference may have a word designator but no event specification. It then references the previous command. Continuing our `diff' example, we could have said simply `diff !^.old !^' or, to get the arguments in the opposite order, just `diff !*'.
The word or words in a history reference can be edited, or ``modified'', by following it with one or more modifiers, each preceded by a `:':
- h
- Remove a trailing pathname component, leaving the head.
- t
- Remove all leading pathname components, leaving the tail.
- r
- Remove a filename extension `.xxx', leaving the root name.
- e
- Remove all but the extension.
- u
- Uppercase the first lowercase letter.
- l
- Lowercase the first uppercase letter.
- s/l/r/
- Substitute l for r. l is simply a string like r, not a regular expression as in the eponymous ed(1) command. Any character may be used as the delimiter in place of `/'; a `\' can be used to quote the delimiter inside l and r. The character `&' in the r is replaced by l; `\' also quotes `&'. If l is empty (``''), the l from a previous substitution or the s from a previous `?s?' event specification is used. The trailing delimiter may be omitted if it is immediately followed by a newline.
- &
- Repeat the previous substitution.
- g
- Apply the following modifier once to each word.
- a (+)
- Apply the following modifier as many times as possible to a single word. `a' and `g' can be used together to apply a modifier globally. In the current implementation, using the `a' and `s' modifiers together can lead to an infinite loop. For example, `:as/f/ff/' will never terminate. This behavior might change in the future.
- p
- Print the new command line 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.
Modifiers are applied only to the first modifiable word (unless `g' is used). It is an error for no word to be modifiable.
For example, the `diff' command might have been written as `diff wumpus.man.old !#^:r', using `:r' to remove `.old' from the first argument on the same line (`!#^'). We could say `echo hello out there', then `echo !*:u' to capitalize `hello', `echo !*:au' to say it out loud, or `echo !*:agu' to really shout. We might follow `mail -s "I forgot my password" rot' with `!:s/rot/root' to correct the spelling of `root' (but see Spelling correction for a different approach).
There is a special abbreviation for substitutions. `^', when it is the first character on an input line, is equivalent to `!:s^'. Thus we might have said `^rot^root' to make the spelling correction in the previous example. This is the only history substitution which does not explicitly begin with `!'.
(+) In csh as such, only one modifier may be applied to each history or variable expansion. In tcsh, more than one may be used, for example
In csh, the result would be `wumpus.1:r'. A substitution followed by a colon may need to be insulated from it with braces:
The first attempt would succeed in csh but fails in tcsh, because tcsh expects another modifier after the second colon rather than `$'.
Finally, history can be accessed through the editor as well as through the substitutions just described. The up- and down-history, history-search-backward and -forward, i-search-back and -fwd, vi-search-back and -fwd, copy-prev-word and insert-last-word editor commands search for events in the history list and copy them into the input buffer. The toggle-literal-history editor command switches between the expanded and literal forms of history lines in the input buffer. expand-history and expand-line expand history substitutions in the current word and in the entire input buffer respectively.
Thus if the alias for `ls' were `ls -l' the command `ls /usr' would become `ls -l /usr', the argument list here being undisturbed. If the alias for `lookup' were `grep !^ /etc/passwd' then `lookup bill' would become `grep bill /etc/passwd'. Aliases can be used to introduce parser metasyntax. For example, `alias print 'pr \!* | lpr'' defines a ``command'' (`print') which pr(1)s its arguments to the line printer.
Alias substitution is repeated until the first word of the command has no alias. If an alias substitution does not change the first word (as in the previous example) it is flagged to prevent a loop. Other loops are detected and cause an error.
Some aliases are referred to by the shell; see Special aliases.
(+) Variables may be made read-only with `set -r' (q.v.) Read-only variables may not be modified or unset; attempting to do so will cause an error. Once made read-only, a variable cannot be made writable, so `set -r' should be used with caution. Environment variables cannot be made read-only.
Some 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. Some of the variables referred to by the shell 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 -v command line option sets this variable. Special shell variables lists all variables which are referred to by the shell.
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 variable's 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[selector]
$number
The `:' modifiers described under History substitution, except for `:p', can be applied to the substitutions above. More than one may be used. (+) Braces may be needed to insulate a variable substitution from a literal colon just as with History substitution (q.v.); any modifiers must appear within the braces.
The following substitutions can not be modified with `:' modifiers.
$?name
$#name
$%name
$%number
The editor command expand-variables, normally bound to `^X-$', can be used to interactively expand individual variables.
Command substitutions inside double quotes (`"') retain blanks and tabs; only newlines force new words. The single final newline does not force a new word in any case. It is thus possible for a command substitution to yield only part of a word, even if the command outputs a complete line.
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.
(+) Some glob-patterns can be negated: The sequence `[^...]' matches any single character not specified by the characters and/or ranges of characters in the braces.
An entire glob-pattern can also be negated with `^':
Glob-patterns which do not use `?', `*', or `[]' or which use `{}' or `~' (below) are not negated correctly.
The metanotation `a{b,c,d}e' is a shorthand for `abe ace ade'. Left-to-right order is preserved: `/usr/source/s1/{oldls,ls}.c' expands to `/usr/source/s1/oldls.c /usr/source/s1/ls.c'. The results of matches are sorted separately at a low level to preserve this order: `../{memo,*box}' might expand to `../memo ../box ../mbox'. (Note that `memo' was not sorted with the results of matching `*box'.) It is not an error when this construct expands to files which do not exist, but it is possible to get an error from a command to which the expanded list is passed. This construct may be nested. As a special case the words `{', `}' and `{}' are passed undisturbed.
The character `~' at the beginning of a filename refers to home directories. Standing alone, i.e. `~', it expands to the invoker's home directory as reflected in the value of the home shell variable. 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 elsewhere than at the beginning of a word, it is left undisturbed. A command like `setenv MANPATH /usr/man:/usr/local/man:~/lib/man' does not, therefore, do home directory substitution as one might hope.
It is an error for a glob-pattern containing `*', `?', `[' or `~', with or without `^', not to match any files. However, only one pattern in a list of glob-patterns must match a file (so that, e.g., `rm *.a *.c *.o' would fail only if there were no files in the current directory ending in `.a', `.c', or `.o'), and if the nonomatch shell variable is set a pattern (or list of patterns) which matches nothing is left unchanged rather than causing an error.
The noglob shell variable can be set to prevent filename substitution, and the expand-glob editor command, normally bound to `^X-*', can be used to interactively expand individual filename substitutions.
The character `=' followed by one or more digits expands to an entry in the directory stack. The special case `=-' expands to the last directory in the stack. For example,
The noglob and nonomatch shell variables and the expand-glob editor command apply to directory stack as well as filename substitutions.
Simple commands and pipelines may be joined into sequences with `;', and will be executed sequentially. Commands and pipelines can also be joined into sequences with `||' or `&&', indicating, as in the C language, that the second is to be executed only if the first fails or succeeds respectively.
A simple command, pipeline or sequence may be placed in parentheses, `()', to form a simple command, which may in turn be a component of a pipeline or sequence. A command, pipeline or sequence can be executed without waiting for it to terminate by following it with an `&'.
Parenthesized commands are always executed in a subshell.
thus prints the home directory, leaving you where you were (printing this after the home directory), while
leaves you in the home directory. Parenthesized commands are most often used to prevent cd from affecting the current shell.
When a command to be executed is found not to be a builtin command the shell attempts to execute the command via execve(2). Each word in the variable path names a directory in which the shell will look for the command. If it is given neither a -c nor a -t option, the shell hashes the names in these directories into an internal table so that it will only try an execve(2) 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), if the shell was given a -c or -t argument or in any case for each directory component of path which does not begin with a `/', the shell concatenates the current working directory with the given command name to form a path name of a file which it then attempts to execute.
If the file has execute permissions but is not an executable to the system (i.e. it is neither an executable binary nor a script which specifies its interpreter), then it is assumed to be a file containing shell commands and a new shell is spawned to read it. The shell special alias may be set to specify an interpreter other than the shell itself.
On systems which do not understand the `#!' script interpreter convention the shell may be compiled to emulate it; see the version shell variable. If so, the shell checks the first line of the file to see if it is of the form `#!interpreter arg ...'. If it is, the shell starts interpreter with the given args and feeds the file to it on standard input.
> name
>! name
>& name
If the shell 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 to 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
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 the empty file /dev/null, but 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).
Diagnostic output may be directed through a pipe with the standard output. Simply use the form `|&' rather than just `|'.
The shell cannot presently redirect diagnostic output without also redirecting standard output, but `(command > output-file) >& error-file' is often an acceptable workaround. Either output-file or error-file may be `/dev/tty' to send output to the terminal.
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 gotos will succeed on non-seekable inputs.)
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 glob-pattern (see Filename substitution) against which the left hand operand is matched. This reduces the need for use of the switch builtin command 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 results 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.
- r
- Read access
- w
- Write access
- x
- Execute access
- X
- Executable in the path or shell builtin, e.g. `-X ls' and `-X ls-F' are generally true, but `-X /bin/ls' is not (+)
- e
- Existence
- o
- Ownership
- z
- Zero size
- s
- Non-zero size (+)
- f
- Plain file
- d
- Directory
- l
- Symbolic link (+) *
- b
- Block special file (+)
- c
- Character special file (+)
- p
- Named pipe (fifo) (+) *
- S
- Socket special file (+) *
- u
- Set-user-ID bit is set (+)
- g
- Set-group-ID bit is set (+)
- k
- Sticky bit is set (+)
- t
- file (which must be a digit) is an open file descriptor for a terminal device (+)
- L
- Applies subsequent operators in a multiple-operator test to a symbolic link rather than to the file to which the link points (+) *
file is command and filename expanded and then tested to see if it has the specified relationship to the real user. If file does not exist or is inaccessible or, for the operators indicated by `*', if the specified file type does not exist on the current system, then all enquiries return false, i.e. `0'.
These operators may be combined for conciseness: `-xy file' is equivalent to `-x file && -y file'. (+) For example, `-fx' is true (returns `1') for plain executable files, but not for directories.
L may be used in a multiple-operator test to apply subsequent operators to a symbolic link rather than to the file to which the link points. For example, `-lLo' is true for links owned by the invoking user. Lr, Lw and Lx are always true for links and false for non-links. L has a different meaning when it is the last operator in a multiple-operator test; see below.
It is possible but not useful, and sometimes misleading, to combine operators which expect file to be a file with operators which do not, (e.g. X and t). Following L with a non-file operator can lead to particularly strange results.
Other operators return other information, i.e. not just `0' or `1'. (+) They have the same format as before; op may be one of
in bytes
- A
- Last file access time, as the number of seconds since the epoch
- A:
- Like A, but in timestamp format, e.g. `Fri May 14 16:36:10 1993'
- M
- Last file modification time
- M:
- Like M, but in timestamp format
- C
- Last inode modification time
- C:
- Like C, but in timestamp format
- D
- Device number
- I
- Inode number
- F
- Composite file identifier, in the form device:inode
- L
- The name of the file pointed to by a symbolic link
- N
- Number of (hard) links
- P
- Permissions, in octal, without leading zero
- P:
- Like P, with leading zero
- Pmode
- Equivalent to `-P file & mode', e.g. `-P22 file' returns `22' if file is writable by group and other, `20' if by group only, and `0' if by neither
- Pmode:
- Like Pmode:, with leading zero
- U
- Numeric userid
- U:
- Username, or the numeric userid if the username is unknown
- G
- Numeric groupid
- G:
- Groupname, or the numeric groupid if the groupname is unknown
- Z
- Size,
Only one of these operators may appear in a multiple-operator test, and it must be the last. Note that L has a different meaning at the end of and elsewhere in a multiple-operator test. Because `0' is a valid return value for many of these operators, they do not return `0' when they fail: most return `-1', and F returns `:'.
If the shell is compiled with POSIX defined (see the version shell variable), the result of a file inquiry is based on the permission bits of the file and not on the result of the access(2) system call. For example, if one tests a file with -w whose permissions would ordinarily allow writing but which is on a file system mounted read-only, the test will succeed in a POSIX shell but fail in a non-POSIX shell.
File inquiry operators can also be evaluated with the filetest builtin command (q.v.) (+).
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 suspend key (usually `^Z'), which sends a STOP signal to the current job. The shell will then normally indicate that the job has been `Suspended' and print another prompt. If the listjobs shell variable is set, all jobs will be listed like the jobs builtin command; if it is set to `long' the listing will be in long format, like `jobs -l'. You can then manipulate the state of the suspended job. You can put it in the ``background'' with the bg command or run some other commands and eventually bring the job back into the ``foreground'' with fg. (See also the run-fg-editor editor command.) A `^Z' takes effect immediately and is like an interrupt in that pending output and unread input are discarded when it is typed. The wait builtin command causes the shell to wait for all background jobs to complete.
The `^]' key sends a delayed suspend signal, which does not generate a STOP signal until a program attempts to read(2) it, to the current job. 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. The `^Y' key performs this function in csh(1); in tcsh, `^Y' is an editing command. (+)
A job being run in the background stops 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, just like `bg %1'. A job can also be named by an unambigous prefix of the string typed in to start it: `%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' to specify 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 abbreviations `%+', `%', and (by analogy with the syntax of the history mechanism) `%%' all refer to the current job, and `%-' refers to the previous job.
The job control mechanism requires that the stty(1) option `new' be set on some systems. It is an artifact from a `new' implementation of the tty driver which allows generation of interrupt characters from the keyboard to tell jobs to stop. See stty(1) and the setty builtin command for details on setting options in the new tty driver.
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.
The sched builtin command puts commands in a scheduled-event list, to be executed by the shell at a given time.
The beepcmd, cwdcmd, periodic and precmd Special aliases can be set, respectively, to execute commands when the shell wants to ring the bell, when the working directory changes, every tperiod minutes and before each prompt.
The autologout shell variable can be set to log out or lock the shell after a given number of minutes of inactivity.
The mail shell variable can be set to check for new mail periodically.
The printexitvalue shell variable can be set to print the exit status of commands which exit with a status other than zero.
The rmstar shell variable can be set to ask the user, when `rm *' is typed, if that is really what was meant.
The time shell variable can be set to execute the time builtin command after the completion of any process that takes more than a given number of CPU seconds.
The watch and who shell variables can be set to report when selected users log in or out, and the log builtin command reports on those users at any time.
When using the system's NLS, the setlocale(3) function is called to determine appropriate character classification and sorting. This function typically examines the LANG and LC_CTYPE environment variables; refer to the system documentation for further details. When not using the system's NLS, the shell simulates it by assuming that the ISO 8859-1 character set is used whenever either of the LANG and LC_CTYPE variables are set, regardless of their values. Sorting is not affected for the simulated NLS.
In addition, with both real and simulated NLS, all printable characters in the range \200-\377, i.e. those that have M-char bindings, are automatically rebound to self-insert-command. The corresponding binding for the escape-char sequence, if any, is left alone. These characters are not rebound if the NOREBIND environment variable is set. This may be useful for the simulated NLS or a primitive real NLS which assumes full ISO 8859-1. Otherwise, all M-char bindings in the range \240-\377 are effectively undone. Explicitly rebinding the relevant keys with bindkey is of course still possible.
Unknown characters (i.e. those that are neither printable nor control characters) are printed in the format \nnn. If the tty is not in 8 bit mode, other 8 bit characters are printed by converting them to ASCII and using standout mode. The shell never changes the 7/8 bit mode of the tty and tracks user-initiated changes of 7/8 bit mode. NLS users (or, for that matter, those who want to use a meta key) may need to explicitly set the tty in 8 bit mode through the appropriate stty(1) command in, e.g., the ~/.login file.
On systems that support TCF (aix-ibm370, aix-ps2), getspath and setspath get and set the system execution path, getxvers and setxvers get and set the experimental version prefix and migrate migrates processes between sites. The jobs builtin prints the site on which each job is executing.
Under Domain/OS, inlib adds shared libraries to the current environment, rootnode changes the rootnode and ver changes the systype.
Under Mach, setpath is equivalent to Mach's setpath(1).
Under Masscomp/RTU, universe sets the universe.
Under Convex/OS, warp prints or sets the universe.
The VENDOR, OSTYPE and MACHTYPE environment variables indicate respectively the vendor, operating system and machine type (microprocessor class or machine model) of the system on which the shell thinks it is running. These are particularly useful when sharing one's home directory between several types of machines; one can, for example,
in one's ~/.login and put executables compiled for each machine in the appropriate directory.
The version shell variable indicates what options were chosen when the shell was compiled.
Note also the newgrp builtin, the afsuser and echo_style shell variables and the system-dependent locations of the shell's input files (see FILES).
In shell scripts, the shell's handling of interrupt and terminate signals can be controlled with onintr, and its handling of hangups can be controlled with hup and nohup.
The shell exits on a hangup (see also the logout shell variable). By default, the shell's children do too, but the shell does not send them a hangup when it exits. hup arranges for the shell to send a hangup to a child when it exits, and nohup sets a child to ignore hangups.
The echotc, settc and telltc commands can be used to manipulate and debug terminal capabilities from the command line.
On systems that support SIGWINCH or SIGWINDOW, the shell adapts to window resizing automatically and adjusts the environment variables LINES and COLUMNS if set. If the environment variable TERMCAP contains li# and co# fields, the shell adjusts them to reflect the new window size.
@
@ name = expr
[index] = expr
expr may contain the operators `*', `+', etc. 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, e.g. `@ i++'.
Note that the syntax of expr has nothing to do with that described under Expressions.
bindkey [-l|-d|-e|-v|-u] (+)
bindkey [-a] [-b] [-k] [-r] [--] key (+)
- -l
- Lists all editor commands and a short description of each.
- -d
- Binds all keys to the standard bindings for the default editor.
- -e
- Binds all keys to the standard GNU Emacs-like bindings.
- -v
- Binds all keys to the standard vi(1)-like bindings.
- -a
- Lists or changes key-bindings in the alternative key map. This is the key map used in vi command mode.
- -b
- key is interpreted as a control character written ^character (e.g. `^A') or C-character (e.g. `C-A'), a meta character written M-character (e.g. `M-A'), a function key written F-string (e.g. `F-string'), or an extended prefix key written X-character (e.g. `X-A').
- -k
- key is interpreted as a symbolic arrow key name, which may be one of `down', `up', `left' or `right'.
- -r
- Removes key's binding. Be careful: `bindkey -r' does not bind key to self-insert-command (q.v.), it unbinds key completely.
- -c
- command is interpreted as a builtin or external command instead of an editor command.
- -s
- command is taken as a literal string and treated as terminal input when key is typed. Bound keys in command are themselves reinterpreted, and this continues for ten levels of interpretation.
- --
- Forces a break from option processing, so the next word is taken as key even if it begins with '-'.
- -u (or any invalid option)
- Prints a usage message.
key may be a single character or a string. If a command is bound to a string, the first character of the string is bound to sequence-lead-in and the entire string is bound to the command.
Control characters in key can be literal (they can be typed by preceding them with the editor command quoted-insert, normally bound to `^V') or written caret-character style, e.g. `^A'. Delete is written `^?' (caret-question mark). key and command can contain backslashed escape sequences (in the style of System V echo(1)) as follows:
- \a
- Bell
- \b
- Backspace
- \e
- Escape
- \f
- Form feed
- \n
- Newline
- \r
- Carriage return
- \t
- Horizontal tab
- \v
- Vertical tab
- \nnn
- The ASCII character corresponding to the octal number nnn
`\' nullifies the special meaning of the following character, if it has any, notably `\' and `^'.
command may be a full command name or a glob-pattern (see Filename substitution). It can begin with `-' to indicate that completion should be used only when command is ambiguous.
word specifies which word relative to the current word is to be completed, and may be one of the following:
- c
- Current-word completion. pattern is a glob-pattern which must match the beginning of the current word on the command line. pattern is ignored when completing the current word.
- C
- Like c, but includes pattern when completing the current word.
- n
- Next-word completion. pattern is a glob-pattern which must match the beginning of the previous word on the command line.
- N
- Like n, but must match the beginning of the word two before the current word.
- p
- Position-dependent completion. pattern is a numeric range, with the same syntax used to index shell variables, which must include the current word.
list, the list of possible completions, may be one of the following:
- a
- Aliases
- b
- Bindings (editor commands)
- c
- Commands (builtin or external commands)
- C
- External commands which begin with the supplied path prefix
- d
- Directories
- D
- Directories which begin with the supplied path prefix
- e
- Environment variables
- f
- Filenames
- F
- Filenames which begin with the supplied path prefix
- g
- Groupnames
- j
- Jobs
- l
- Limits
- n
- Nothing
- s
- Shell variables
- S
- Signals
- t
- Plain (``text'') files
- T
- Plain (``text'') files which begin with the supplied path prefix
- v
- Any variables
- u
- Usernames
- x
- Like n, but prints select when list-choices is used.
- X
- Completions
- $var
- Words from the variable var
- (...)
- Words from the given list
- `...`
- Words from the output of command
select is an optional glob-pattern. If given, only words from list which match select are considered and the fignore shell variable is ignored. The last three types of completion may not have a select pattern, and x uses select as an explanatory message when the list-choices editor command is used.
suffix is a single character to be appended to a successful completion. If null, no character is appended. If omitted (in which case the fourth delimiter can also be omitted), a slash is appended to directories and a space to other words.
Now for some examples. Some commands take only directories as arguments, so there's no point completing plain files.
completes only the first word following `cd' (`p/1') with a directory. p-type completion can also be used to narrow down command completion:
This completion completes commands (words in position 0, `p/0') which begin with `co' (thus matching `co*') to `compress' (the only word in the list). The leading `-' indicates that this completion is to be used only with ambiguous commands.
is an example of n-type completion. Any word following `find' and immediately following `-user' is completed from the list of users.
demonstrates c-type completion. Any word following `cc' and beginning with `-I' is completed as a directory. `-I' is not taken as part of the directory because we used lowercase c.
Different lists are useful with different commands.
These complete words following `alias' with aliases, `man' with commands, and `set' with shell variables. `true' doesn't have any options, so x does nothing when completion is attempted and prints `Truth has no options.' when completion choices are listed.
Note that the man example, and several other examples below, could just as well have used 'c/*' or 'n/*' as 'p/*'.
Words can be completed from a variable evaluated at completion time,
or from a command run at completion time:
Note that the complete command does not itself quote its arguments, so the braces, space and `$' in `{print $1}' must be quoted explicitly.
One command can have multiple completions:
completes the second argument to `dbx' with the word `core' and all other arguments with commands. Note that the positional completion is specified before the next-word completion. Since completions are evaluated from left to right, if the next-word completion were specified first it would always match and the positional completion would never be executed. This is a common mistake when defining a completion.
The select pattern is useful when a command takes only files with particular forms as arguments. For example,
completes `cc' arguments only to files ending in `.c', `.a', or `.o'. select can also exclude files, using negation of a glob-pattern as described under Filename substitution. One might use
to exclude precious source code from `rm' completion. Of course, one could still type excluded names manually or override the completion mechanism using the complete-word-raw or list-choices-raw editor commands (q.v.).
The `C', `D', `F' and `T' lists are like `c', `d', `f' and `t' respectively, but they use the select argument in a different way: to restrict completion to files beginning with a particular path prefix. For example, the Elm mail program uses `=' as an abbreviation for one's mail directory. One might use
to complete `elm -f =' as if it were `elm -f ~/Mail/'. Note that we used `@' instead of `/' to avoid confusion with the select argument, and we used `$HOME' instead of `~' because home directory substitution only works at the beginning of a word.
suffix is used to add a nonstandard suffix (not space or `/' for directories) to completed words.
completes arguments to `finger' from the list of users, appends an `@', and then completes after the `@' from the `hostnames' variable. Note again the order in which the completions are specified.
Finally, here's a complex example for inspiration:
This completes words following `-name', `-newer', `-cpio' or `ncpio' (note the pattern which matches both) to files, words following `-exec' or `-ok' to commands, words following `user' and `group' to users and groups respectively and words following `-fstype' or `-type' to members of the given lists. It also completes the switches themselves from the given list (note the use of c-type completion) and completes anything not otherwise completed to a directory. Whew.
Remember that programmed completions are ignored if the word being completed is a tilde substitution (beginning with `~') or a variable (beginning with `$'). complete is an experimental feature, and the syntax may change in future versions of the shell. See also the uncomplete builtin command.
dirs [-l] [-n|-v]
dirs -S|-L [filename] (+)
With -S, the second form saves the directory stack to filename as a series of cd and pushd commands. With -L, the shell sources filename, which is presumably a directory stack file saved by the -S option or the savedirs mechanism. In either case, dirsfile is used if filename is not given and ~/.cshdirs is used if dirsfile is unset.
Note that login shells do the equivalent of `dirs -L' on startup and, if savedirs is set, `dirs -S' before exiting. Because only ~/.tcshrc is normally sourced before ~/.cshdirs, dirsfile should be set in ~/.tcshrc rather than ~/.login.
The last form clears the directory stack.
If arg is 'baud', 'cols', 'lines', 'meta' or 'tabs', prints the value of that capability ("yes" or "no" indicating that the terminal does or does not have that capability). One might use this to make the output from a shell script less verbose on slow terminals, or limit command output to the number of lines on the screen:
Termcap strings may contain wildcards which will not echo correctly. One should use double quotes when setting a shell variable to a terminal capability string, as in the following example that places the date in the status line:
With -s, nonexistent capabilities return the empty string rather than causing an error. With -v, messages are verbose.
else
end
endif
foreach name (wordlist)
...
On machines without vfork(2), prints only the number and size of hash buckets. history [-hr] [n]
history -S|-L|-M [filename] (+)
With -S, the second form saves the history list to filename. If the first word of the savehist shell variable is set to a number, at most that many lines are saved. If the second word of savehist is set to `merge', the history list is merged with the existing history file instead of replacing it (if there is one) and sorted by time stamp. (+) Merging is intended for an environment like the X Window System with several shells in simultaneous use. Currently it only succeeds when the shells quit nicely one after another.
With -L, the shell appends filename, which is presumably a history list saved by the -S option or the savehist mechanism, to the history list. -M is like -L, but the contents of filename are merged into the history list and sorted by timestamp. In either case, histfile is used if filename is not given and ~/.history is used if histfile is unset. `history -L' is exactly like 'source -h' except that it does not require a filename.
Note that login shells do the equivalent of `history -L' on startup and, if savehist is set, `history -S' before exiting. Because only ~/.tcshrc is normally sourced before ~/.history, histfile should be set in ~/.tcshrc rather than ~/.login.
If histlit is set, the first and second forms print and save the literal (unexpanded) form of the history list.
The last form clears the history list.
if (expr) then
...
else if (expr2) then
...
else
...
kill [-signal] %job|pid ...
Controllable resources 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), coredumpsize (the size of the largest core dump that will be created), and memoryuse, the maximum amount of physical memory a process may have allocated to it at a given time.
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.
- /
- Directory
- *
- Executable
- #
- Block device
- %
- Character device
- |
- Named pipe (systems with named pipes only)
- =
- Socket (systems with sockets only)
- @
- Symbolic link (systems with symbolic links only)
- +
- Hidden directory (AIX only) or context dependent (HP/UX only)
- :
- Network special (HP/UX only)
If the listlinks shell variable is set, symbolic links are identified in more detail (only, of course, on systems which have them):
- @
- Symbolic link to a non-directory
- >
- Symbolic link to a directory
- &
- Symbolic link to nowhere
listlinks also slows down ls-F and causes partitions holding files pointed to by symbolic links to be mounted.
If the listflags shell variable is set to `x', `a' or `A', or any combination thereof (e.g. `xA'), they are used as flags to ls-F, making it act like `ls -xF', `ls -Fa', `ls -FA' or a combination (e.g. `ls -FxA'). On machines where `ls -C' is not the default, ls-F acts like `ls -CF', unless listflags contains an `x', in which case it acts like `ls -xF'. ls-F passes its arguments to ls(1) if it is given any switches, so `alias ls ls-F' generally does the right thing. ls-F includes file identification characters when sorting filenames; this is a bug.
migrate [-site] pid|%jobid ... (+)
sched (+)
sched [+]hh:mm command (+)
causes the shell to echo `It's eleven o'clock.' at 11 AM. The time may be in 12-hour AM/PM format
or may be relative to the current time:
A relative time specification may not use AM/PM format. The third form removes item n from the event list:
A command in the scheduled-event list is executed just before the first prompt is printed after the time when the command is scheduled. It is possible to miss the exact time when the command is to be run, but an overdue command will execute at the next prompt. A command which comes due while the shell is waiting for user input is executed immediately. However, normal operation of an already-running command will not be interrupted so that a scheduled-event list element may be run.
This mechanism is similar to, but not the same as, the at(1) command on some Unix systems. Its major disadvantage is that it may not run a command at exactly the specified time. Its major advantage is that because sched runs directly from the shell, it has access to shell variables and other structures. This provides a mechanism for changing one's working environment based on the time of day.
set
set name ...
set name=word ...
set name=(wordlist) ...
set name[index]=word ...
set -r (+)
set -r name ... (+)
set -r name=word ... (+)