Argument list processing¶

If the first argument (argument 0) to the shell is ‘-’ then it is a login shell. A login shell can be also specified by invoking the shell with the -l flag as the only argument.

The rest of the flag arguments are interpreted as follows:

-b

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 following argument (which must be present, and must be a single argument), stored in the command shell variable for reference, and executed. Any remaining arguments are placed in the argv shell variable.

-d

The shell loads the directory stack from ~/.cshdirs as described under Startup and shutdown, whether or not it is a login shell. (+)

-Dname[=value]

Sets the environment variable name to value. (Domain/OS only) (+)

-e

The shell exits if any invoked command terminates abnormally or yields a non-zero exit status.

-f

The shell does not load any resource or startup files, or perform any command hashing, and thus starts faster.

-F

The shell uses fork(2) instead of vfork(2) to spawn processes. (+)

-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.

-l

The shell is a login shell. Applicable only if -l is the only flag specified.

-m

The shell loads ~/.tcshrc even if it does not belong to the effective user. Newer versions of su(1) can pass -m to the shell. (+)

-n

The shell parses commands but does not execute them. This aids in debugging shell scripts.

-q

The shell accepts SIGQUIT (see Signal handling) and behaves when it is used under a debugger. Job control is disabled. (u)

-s

Command input is taken from the standard input.

-t

The shell reads and executes a single line of input. A ‘\’ may be used to escape the newline at the end of this line and continue onto another line.

-v

Sets the verbose shell variable, so that command input is echoed after history substitution.

-x

Sets the echo shell variable, so that commands are echoed immediately before execution.

-V

Sets the verbose shell variable even before executing ~/.tcshrc.

-X

Is to -x as -V is to -v.

--help

Print a help message on the standard output and exit. (+)

--version

Print the version/platform/compilation options on the standard output and exit. This information is also contained in the version shell variable. (+)

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’. Because 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., that does not start with a comment.

Remaining arguments are placed in the argv shell variable.

Startup and shutdown¶

A login shell begins by executing commands from the system files /etc/csh.cshrc and /etc/csh.login. It then executes commands from files in the user's home directory: first ~/.tcshrc (+) or, if ~/.tcshrc is not found, ~/.cshrc, then the contents of ~/.history (or the value of the histfile shell variable) are loaded into memory, then ~/.login, and finally ~/.cshdirs (or the value of the dirsfile shell variable) (+). The shell may read /etc/csh.login before instead of after /etc/csh.cshrc, and ~/.login before instead of after ~/.tcshrc or ~/.cshrc and ~/.history, if so compiled; see the version shell variable. (+)

Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or ~/.cshrc on startup.

For examples of startup files, please consult: http://tcshrc.sourceforge.net

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 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.

Editing¶

We first describe The command-line editor (+). The Completion and listing (+) and Spelling correction (+) sections describe two sets of functionality that are implemented as editor commands but which deserve their own treatment. Finally, Editor commands (+) lists and describes the editor commands specific to the shell and their default bindings.

The command-line editor (+)¶

Command-line input can be edited using key sequences much like those used in emacs(1) or vi(1). The editor is active only when the edit shell variable is set, which it is by default in interactive shells. The bindkey builtin can display and change key bindings to editor commands (see Editor commands (+)). emacs(1)-style key bindings are used by default (unless the shell was compiled otherwise; see the version shell variable), but bindkey can change the key bindings to vi(1)-style bindings en masse.

The shell always binds the arrow keys (as defined in the TERMCAP environment variable) to editor commands:

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(1) 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. Certain key bindings have different behavior depending if emacs(1) or vi(1)-style bindings are being used; see vimode for more information.

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 and listing (+)¶

The shell is often able to complete words when given a unique abbreviation. For example, typing part of a word

Completion works anywhere in the line, not at just 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 that need to be deleted.

Commands and variables can be completed in much the same way. For example, typing

Typing

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 and reprints the prompt and unfinished command line, for example:

> ls /usr/l[^D]
lbin/       lib/        local/      lost+found/
> ls /usr/l

If the autolist shell variable is set, the shell lists the remaining choices (if any) whenever completion fails:

> set autolist
> nm /usr/lib/libt[tab]
libtermcap.a@ libtermlib.a@
> nm /usr/lib/libterm

If the autolist shell variable 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,

> ls ~k[^D]
kahn    kas     kellogg
> ls ~ke[tab]
> ls ~kellogg/

or

> set local = /usr/local
> ls $lo[tab]
> ls $local/[^D]
bin/ etc/ lib/ man/ src/
> ls $local/

Note that variables can also be expanded explicitly with the expand-variables editor command.

delete-char-or-list-or-eof lists at only 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 the ignoreeof variable 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 that 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:

> ls
Makefile        condiments.h~   main.o          side.c
README          main.c          meal            side.o
condiments.h    main.c~
> set fignore = (.o \~)
> emacs ma[^D]
main.c   main.c~  main.o
> emacs ma[tab]
> emacs main.c

‘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

comp.lang.c      comp.lang.perl   comp.std.c++
comp.lang.c++    comp.std.c

and typed

Typing

Typing

A_silly_file    a-hyphenated-file    another_silly_file

would list all three files, because case is ignored and hyphens and underscores are equivalent. Periods, however, are not equivalent to hyphens or underscores.

If the complete shell variable is set to ‘Enhance’, completion ignores case and differences between a hyphen and an underscore word separator only when the user types a lowercase character or a hyphen. Entering an uppercase character or an underscore will not match the corresponding lowercase character or hyphen word separator.

Typing

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:

> ls
fodder   foo      food     foonly
> set recexact
> rm fo[tab]

just beeps, because ‘fo’ could expand to ‘fod’ or ‘foo’, but if we type another ‘o’,

> rm foo[tab]
> rm foo

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 that 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.

Spelling correction (+)¶

The shell can sometimes correct the spelling of filenames, commands and variable names as well as completing and listing them.

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:

> set correct = cmd
> lz /usr/bin
CORRECT>ls /usr/bin (y|n|e|a)?

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.

Editor commands (+)¶

bindkey lists key bindings and bindkey -l lists and briefly describes editor commands. Only new or especially interesting editor commands are described here. See emacs(1) and vi(1) for descriptions of each editor's key bindings.

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 (or ^[character) on terminals without a meta key. Case counts, but commands that are bound to letters by default are bound to both lower- and uppercase letters for convenience.

Supported editor commands are:

backward-char (^B, left)

Move back a character. Cursor behavior modified by vimode.

backward-delete-word (M-^H, M-^?)

Cut from beginning of current word to cursor - saved in cut buffer. Word boundary behavior modified by vimode.

backward-word (M-b, M-B)

Move to beginning of current word. Word boundary and cursor behavior modified by vimode.

beginning-of-line (^A, home)

Move to beginning of line. Cursor behavior modified by vimode.

capitalize-word (M-c, M-C)

Capitalize the characters from cursor to end of current word. Word boundary behavior modified by vimode.

complete-word (tab)

Completes a word as described under Completion and listing (+).

complete-word-back (not bound)

Like complete-word-fwd, but steps up from the end of the list.

complete-word-fwd (not bound)

Replaces the current word with the first word in the list of possible completions. May be repeated to step down through the list. At the end of the list, beeps and reverts to the incomplete word.

complete-word-raw (^X-tab)

Like complete-word, but ignores user-defined completions.

copy-prev-word (M-^_)

Copies the previous word in the current line into the input buffer. See also insert-last-word. Word boundary behavior modified by vimode.

dabbrev-expand (M-/)

Expands the current word to the most recent preceding one for which the current is a leading substring, wrapping around the history list (once) if necessary. Repeating dabbrev-expand without any intervening typing changes to the next previous word etc., skipping identical matches much like history-search-backward does.

delete-char (not bound)

Deletes the character under the cursor. See also delete-char-or-list-or-eof. Cursor behavior modified by vimode.

delete-char-or-eof (not bound)

Does delete-char if there is a character under the cursor or end-of-file on an empty line. See also delete-char-or-list-or-eof. Cursor behavior modified by vimode.

delete-char-or-list (not bound)

Does delete-char if there is a character under the cursor or list-choices at the end of the line. See also delete-char-or-list-or-eof.

delete-char-or-list-or-eof (^D)

Does delete-char if there is a character under the cursor, list-choices at the end of the line or end-of-file on an empty line. See also those three commands, each of which does only a single action, and delete-char-or-eof, delete-char-or-list, and list-or-eof, each of which does a different two out of the three.

delete-word (M-d, M-D)

Cut from cursor to end of current word - save in cut buffer. Word boundary behavior modified by vimode.

down-history (down, ^N)

Like up-history, but steps down, stopping at the original input line.

downcase-word (M-l, M-L)

Lowercase the characters from cursor to end of current word. Word boundary behavior modified by vimode.

end-of-file (not bound)

Signals an end of file, causing the shell to exit unless the ignoreeof shell variable is set to prevent this. See also delete-char-or-list-or-eof.

end-of-line (^E, end)

Move cursor to end of line. Cursor behavior modified by vimode.

expand-history (M-space)

Expands history substitutions in the current word. See History substitution. See also magic-space, toggle-literal-history, and the autoexpand shell variable.

expand-glob (^X-*)

Expands the glob-pattern to the left of the cursor. See Filename substitution.

expand-line (not bound)

Like expand-history, but expands history substitutions in each word in the input buffer.

expand-variables (^X-$)

Expands the variable to the left of the cursor. See Variable substitution.

forward-char (^F, right)

Move forward one character. Cursor behavior modified by vimode.

forward-word (M-f, M-F)

Move forward to end of current word. Word boundary and cursor behavior modified by vimode.

history-search-backward (M-p, M-P)

Searches backwards through the history list for a command beginning with the current contents of the input buffer up to the cursor and copies it into the input buffer. The search string may be a glob-pattern (see Filename substitution) containing ‘*’, ‘?’, ‘[]’, or ‘{}’. up-history and down-history will proceed from the appropriate point in the history list. Emacs mode only. See also history-search-forward and i-search-back.

history-search-forward (M-n, M-N)

Like history-search-backward, but searches forward.

i-search-back (not bound)

Searches backward like history-search-backward, copies the first match into the input buffer with the cursor positioned at the end of the pattern, and prompts with

bck: 

and the first match. Additional characters may be typed to extend the search, i-search-back may be typed to continue searching with the same pattern, wrapping around the history list if necessary, (i-search-back must be bound to a single character for this to work) or one of the following special characters may be typed:

Key

Behavior

^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. See also i-search-fwd and history-search-backward. Word boundary behavior modified by vimode.

i-search-fwd (not bound)

Like i-search-back, but searches forward. Word boundary behavior modified by vimode.

insert-last-word (M-_)

Inserts the last word of the previous input line (‘!$’) into the input buffer. See also copy-prev-word.

list-choices (M-^D)

Lists completion possibilities as described under Completion and listing (+). See also delete-char-or-list-or-eof and list-choices-raw.

list-choices-raw (^X-^D)

Like list-choices, but ignores user-defined completions.

list-glob (^X-g, ^X-G)

Lists (via the ls-F builtin) matches to the glob-pattern (see Filename substitution) to the left of the cursor.

list-or-eof (not bound)

Does list-choices or end-of-file on an empty line. See also delete-char-or-list-or-eof.

magic-space (not bound)

Expands history substitutions in the current line, like expand-history, and inserts a space. magic-space is designed to be bound to the space bar, but is not bound by default.

normalize-command (^X-?)

Searches for the current word in PATH and, if it is found, replaces it with the full path to the executable. Special characters are quoted. Aliases are expanded and quoted but commands within aliases are not. This command is useful with commands that take commands as arguments, e.g., ‘dbx’ and ‘sh -x’.

normalize-path (^X-n, ^X-N)

Expands the current word as described under the ‘expand’ setting of the symlinks shell variable.

overwrite-mode (unbound)

Toggles between input and overwrite modes.

run-fg-editor (M-^Z)

Saves the current input line and looks for a stopped job where the file name portion of its first word is found in the editors shell variable. If editors is not set, then the file name portion of the EDITOR environment variable (‘ed’ if unset) and the VISUAL environment variable (‘vi’ if unset) will be used. If such a job is found, it is restarted as if ‘fg %job’ had been typed. This is used to toggle back and forth between an editor and the shell easily. Some people bind this command to ^Z so they can do this even more easily.

run-help (M-h, M-H)

Searches for documentation on the current command, using the same notion of “current command” as the completion routines, and prints it. There is no way to use a pager; run-help is designed for short help files. If the special alias helpcommand is defined, it is run with the command name as a sole argument. Else, documentation should be in a file named command.help, command.1, command.6, command.8, or command, which should be in one of the directories listed in the HPATH environment variable. If there is more than one help file only the first is printed.

self-insert-command (text characters)

In insert mode (the default), inserts the typed character into the input line after the character under the cursor. In overwrite mode, replaces the character under the cursor with the typed character. The input mode is normally preserved between lines, but the inputmode shell variable can be set to ‘insert’ or ‘overwrite’ to put the editor in that mode at the beginning of each line. See also overwrite-mode.

sequence-lead-in (arrow prefix, meta prefix, ^X)

Indicates that the following characters are part of a multi-key sequence. Binding a command to a multi-key sequence really creates two bindings: the first character to sequence-lead-in and the whole sequence to the command. All sequences beginning with a character bound to sequence-lead-in are effectively bound to undefined-key unless bound to another command.

spell-line (M-$)

Attempts to correct the spelling of each word in the input buffer, like spell-word, but ignores words whose first character is one of ‘-’, ‘!’, ‘^’, or ‘%’, or which contain ‘\’, ‘*’, or ‘?’, to avoid problems with switches, substitutions and the like. See Spelling correction (+).

spell-word (M-s, M-S)

Attempts to correct the spelling of the current word as described under Spelling correction (+). Checks each component of a word which appears to be a pathname.

toggle-literal-history (M-r, M-R)

Expands or unexpands history substitutions in the input buffer. See also expand-history and the autoexpand shell variable.

undefined-key (any unbound key)

Beeps.

up-history (up, ^P)

Copies the previous entry in the history list into the input buffer. If histlit is set, uses the literal form of the entry. May be repeated to step up through the history list, stopping at the top.

upcase-word (M-u, M-U)

Uppercase the characters from cursor to end of current word. Word boundary behavior modified by vimode.

vi-beginning-of-next-word (not bound)

Vi goto the beginning of next word. Word boundary and cursor behavior modified by vimode.

vi-eword (not bound)

Vi move to the end of the current word. Word boundary behavior modified by vimode.

vi-search-back (?)

Prompts with

?

for a search string (which may be a glob-pattern, as with history-search-backward), searches for it and copies it into the input buffer. The bell rings if no match is found. Hitting return ends the search and leaves the last match in the input buffer. Hitting escape ends the search and executes the match. vi mode only.

vi-search-fwd (/)

Like vi-search-back, but searches forward.

which-command (M-?)

Does a which (see the description of the builtin command) on the first word of the input buffer.

yank-pop (M-y)

When executed immediately after a yank or another yank-pop, replaces the yanked string with the next previous string from the killring. This also has the effect of rotating the killring, such that this string will be considered the most recently killed by a later yank command. Repeating yank-pop will cycle through the killring any number of times.

Lexical structure¶

The shell splits input lines into words at blanks and tabs. The special characters ‘&’, ‘|’, ‘;’, ‘<’, ‘>’, ‘(’, and ‘)’, and the doubled characters ‘&&’, ‘||’, ‘<<’, and ‘>>’ are always separate words, whether or not they are surrounded by whitespace.

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 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 ‘\’. (Alias substitution is no exception: quoting in any way any character of a word for which an alias has been defined prevents substitution of the alias. The usual way of quoting an alias is to precede it with a backslash.) History substitution is prevented 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) 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, which may result in more than one word.

C-style escape sequences can be used in single quoted strings by preceding the leading quote with ‘$’. (+) See Escape sequences (+) for a complete list of recognized escape sequences.

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 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.

Escape sequences (+)¶

The following escape sequences are always recognized inside a string constructed using ‘$''’, and optionally by the echo builtin command as controlled by the echo_style shell variable.

Supported escape sequences are:

The implementations of ‘\x’, ‘\u’, and ‘\U’ in other shells may take a varying number of digits. It is often safest to use leading zeros to provide the maximum expected number of digits.

Substitutions¶

We now describe the various transformations the shell performs on the input in the order in which they occur. We note in passing the data structures involved and the commands and variables which affect them. Remember that substitutions can be prevented by quoting as described under Lexical structure.

History substitution¶

Each command, or “event”, input from the terminal is saved in the history list. The previous command is always saved, and the history shell variable can be set to a number to save that many commands. The histdup shell variable can be set to not save duplicate events or consecutive duplicate events.

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.

By default history entries are displayed by printing each parsed token separated by space; thus the redirection operator ‘>&!’ will be displayed as ‘> & !’. 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 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 ‘^’; see History substitution abbreviation.

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” (see History event specification), which indicates the event from which words are to be taken, a “word designator” (see History word designators), which selects particular words from the chosen event, and/or a “word modifier” (see History word modifiers), which manipulates the selected words.

History event specification¶

A history event specification may be one of (with the history substitution character ‘!’ shown):

For example, consider this bit of someone's history list:

 9  8:30    nroff -man wumpus.man
10  8:31    cp wumpus.man wumpus.man.old
11  8:36    vi wumpus.man
12  8:37    diff wumpus.man.old wumpus.man

The commands are shown with their event numbers and time stamps. The current event, which we haven't typed in yet, is event 13.

Typing

Typing

Typing

Typing

Without word designators or modifiers history references simply expand to the entire event, so we might type

History references may be insulated from the surrounding text with braces (‘{’ and ‘}’) if necessary. For example,

(+) While csh(1) expands, for example,

History word designators¶

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, with columns for a leading ‘:’ and a leading ‘!’ (for the abbreviated word designators - see History substitution abbreviation):

Selected words are inserted into the command line separated by single blanks.

For example, the ‘diff’ command (event 12) in the history list example in History event specification,

The ‘cp’ command (event 10) might have been typed

Typing

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 (event 12) might have been typed

A history reference may have a word designator but no event specification. It then references the previous command.

Continuing our ‘diff’ command example (event 12), we could have typed simply

History word modifiers¶

The word or words in a history reference can be edited, or “modified”, by following it with one or more modifiers (with the leading ‘:’ shown), each preceded by a ‘:’:

Modifiers are applied to only the first modifiable word (unless ‘:g’ is used). It is an error for no word to be modifiable.

For example, the ‘diff’ command (event 12) in the history list example in History event specification,

We could type

We might follow

(+) In csh(1) as such, only one modifier may be applied to each history or variable expansion. In tcsh, more than one may be used, for example

% mv wumpus.man /usr/share/man/man1/wumpus.1
% man !$:t:r
man wumpus

In csh(1), the result would be

A substitution followed by a ‘:’ may need to be insulated from it with braces:

> mv a.out /usr/games/wumpus
> setenv PATH !$:h:$PATH
Bad ! modifier: $.
> setenv PATH !{-2$:h}:$PATH
setenv PATH /usr/games:/bin:/usr/bin:.

The first attempt would succeed in csh(1) but fails in tcsh, because tcsh expects another modifier after the second ‘:’ rather than ‘$’.

History substitution abbreviation¶

There is a special abbreviation for substitutions; ‘^’, when it is the first character on an input line, is equivalent to ‘!:s^’. Thus, we might follow the example from History word modifiers

History editor commands¶

Finally, history can be accessed through the editor as well as through the substitutions just described. The up-history and down-history, history-search-backward and history-search-forward, i-search-back and i-search-fwd, vi-search-back and vi-search-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.

Alias substitution¶

The shell maintains a list of aliases which can be set, unset and printed by the alias and unalias commands. After a command line is parsed into simple commands (see Commands) the first word of each command, left-to-right, is checked to see if it has an alias. If so, the first word is replaced by the alias. If the alias contains a history reference, it undergoes History substitution as though the original command were the previous input line. If the alias does not contain a history reference, the argument list is left untouched.

Thus if the alias for ‘ls’ were

If the alias for ‘lookup’ were

Aliases can be used to introduce parser metasyntax. For example,

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 (+).

Variable substitution¶

The shell maintains a list of variables, each of which has as value a list of zero or more words. The values of shell variables can be displayed and changed with the set and unset commands. The system maintains its own list of “environment” variables. These can be displayed and changed with printenv, setenv, and unsetenv.

(+) Variables may be made read-only with

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 multi-word 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 ‘"’ pairs where it always occurs, and within ‘'’ pairs where it never occurs. Strings quoted by ‘`’ are interpreted later (see Command substitution) 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 editor command expand-variables, normally bound to ^X-$, can be used to interactively expand individual variables.

Variable substitution metasequences¶

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.

The ‘:’ modifiers described under History word modifiers, 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 ‘:’ just as with History word modifiers; any modifiers must appear within the braces.

Variable substitution without modifiers¶

The following substitutions cannot be modified with ‘:’ modifiers:

Command, filename and directory stack substitution¶

The remaining substitutions 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 broken into separate words at blanks, tabs and newlines, and null words are discarded. The output is variable and command substituted and put in place of the original string.

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.

By default, the shell since version 6.12 replaces all newline and carriage return characters in the command by spaces. If this is switched off by unsetting csubstnonl, newlines separate commands as usual.

Filename substitution¶

If a word contains any of the characters ‘*’, ‘?’, ‘[’, or ‘{’ or begins with the character ‘~’ it is a candidate for filename substitution, also known as “globbing”. This word is then regarded as a pattern (“glob-pattern”), and replaced with an alphabetically sorted list of file names which match the pattern.

In matching filenames, the character ‘.’ at the beginning of a filename or immediately following a ‘/’, as well as the character ‘/’ must be matched explicitly (unless either globdot or globstar or both are set (+)). 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 ‘^’:

> echo *
bang crash crunch ouch
> echo ^cr*
bang ouch

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:

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

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.,

The globstar shell variable can be set to allow ‘**’ or ‘***’ as a file glob pattern that matches any string of characters including ‘/’, recursively traversing any existing sub-directories. For example,

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.

Directory stack substitution (+)¶

The directory stack is a list of directories, numbered from zero, used by the pushd, popd, and dirs builtin commands. dirs can print, store in a file, restore and clear the directory stack at any time, and the savedirs and dirsfile shell variables can be set to store the directory stack automatically on logout and restore it on login. The dirstack shell variable can be examined to see the directory stack and set to put arbitrary directories into the directory stack.

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,

> dirs -v
0       /usr/bin
1       /usr/spool/uucp
2       /usr/accts/sys
> echo =1
/usr/spool/uucp
> echo =0/calendar
/usr/bin/calendar
> echo =-
/usr/accts/sys

The noglob and nonomatch shell variables and the expand-glob editor command apply to directory stack as well as filename substitutions.

Other substitutions (+)¶

There are several more transformations involving filenames, not strictly related to the above but mentioned here for completeness. Any filename may be expanded to a full path when the symlinks variable is set to ‘expand’. Quoting prevents this expansion, and the normalize-path editor command does it on demand. The normalize-command editor command expands commands in PATH into full paths on demand. Finally, cd and pushd interpret ‘-’ as the old working directory (equivalent to the shell variable owd). This is not a substitution at all, but an abbreviation recognized by only those commands. Nonetheless, it too can be prevented by quoting.

Commands¶

The next three sections describe how the shell executes commands and deals with their input and output.

Simple commands, pipelines and sequences¶

A simple command is a sequence of words, the first of which specifies the command to be executed. A series of simple commands joined by ‘|’ characters forms a pipeline. The output of each command in a pipeline is connected to the input of the next.

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 (‘(’ and ‘)’) 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 ‘&’.

Builtin and non-builtin command execution¶

Builtin commands are executed within the shell. If any component of a pipeline except the last is a builtin command, the pipeline is executed in a subshell.

Parenthesized commands are always executed in a subshell.

(cd; pwd); pwd

thus 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 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 the shell is not given a -f option, the shell hashes the names in these directories into an internal table so that it will try an execve(2) in only a directory where 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. This hashing mechanism is not used:

1. If hashing is turned explicitly off via unhash.
2. If the shell was given a -f argument.
3. For each directory component of path which does not begin with a ‘/’.
4. If the command contains a ‘/’.

In the above four cases the shell concatenates each component of the path vector with the given command name to form a path name of a file which it then attempts to execute it. If execution is successful, the search stops.

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 that 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

Input/output¶

The standard input and standard output of a command may be redirected with the following syntax:

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

Features¶

Having described how the shell accepts, parses and executes command lines, we now turn to a variety of its useful features.

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 gotos will succeed on non-seekable inputs.)

Expressions¶

The if, while, and exit builtin commands use expressions with a common syntax. The expressions can include any of the operators described in the next three sections. Note that the @ builtin command has its own separate syntax.

Logical, arithmetical and comparison operators¶

These operators are similar to those of C and have the same precedence.

The operators, in descending precedence, with equivalent precedence per line, are:

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.

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.

Command exit status¶

Commands can be executed in expressions and their exit status returned by enclosing them in braces (‘{’ and ‘}’). Remember that the braces should be separated from the words of the command by spaces. 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 status shell variable examined.

File inquiry operators¶

Some of these operators perform true/false tests on files and related objects. They are of the form -op file, where -op is one of:

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 inquiries return false, i.e., ‘0’.

These operators may be combined for conciseness:

-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:

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 (+).

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 suspend key (usually ^Z), which sends a STOP signal to the current job. The shell will then normally indicate that the job has been

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

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

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.

Status reporting¶

The 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 right 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 builtin command notify which marks a single process so that its status changes will be immediately reported. By default notify marks the current process; simply enter

When you try to leave the shell while jobs are stopped, you will be warned that

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.

Automatic, periodic and timed events (+)¶

There are various ways to run commands and take other actions automatically at various times in the “life cycle” of the shell. They are summarized here, and described in detail under the appropriate Builtin commands, Special shell variables, and Special aliases (+).

The sched builtin command puts commands in a scheduled-event list, to be executed by the shell at a given time.

The beepcmd, cwdcmd, jobcmd, periodic, precmd, and postcmd Special aliases (+) can be set, respectively, to execute commands: when the shell wants to ring the bell, when the working directory changes, when a job is started or is brought into the foreground, every tperiod minutes, before each prompt, and before each command gets executed.

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

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.

Native Language System support (+)¶

The shell is eight bit clean (if so compiled; see the version shell variable) and thus supports character sets needing this capability. NLS support differs depending on whether or not the shell was compiled to use the system's NLS (again, see version). In either case, 7-bit ASCII is the default character code (e.g., the classification of which characters are printable) and sorting, and changing the LANG or LC_CTYPE environment variables causes a check for possible changes in these respects.

When using the system's NLS, the setlocale(3) function is called to determine appropriate character code/classification and sorting (e.g., ‘en_CA.UTF-8’ would yield ‘UTF-8’ as the character code). 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.

OS variant support (+)¶

A number of new builtin commands are provided to support features in particular operating systems. All are described in detail in the Builtin commands section.

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 BS2000, bs2cmd executes commands of the underlying BS2000/OSD operating system.

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 and Harris CX/UX, universe sets the universe.

Under Harris CX/UX, ucb or att runs a command under the specified 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,

set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .)

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).

Signal handling¶

Login shells ignore interrupts when reading the file ~/.logout. The shell ignores quit signals unless started with -q. Login shells catch the terminate signal, but non-login shells inherit the terminate behavior from their parents. Other signals have the values which the shell inherited from its parent.

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.

Terminal management (+)¶

The shell uses three different sets of terminal (“tty”) modes: ‘edit’, used when editing; ‘quote’, used when quoting literal characters; and ‘execute’, used when executing commands. The shell holds some settings in each mode constant, so commands which leave the tty in a confused state do not interfere with the shell. The shell also matches changes in the speed and padding of the tty. The list of tty modes that are kept constant can be examined and modified with the setty builtin. Note that although the editor uses CBREAK mode (or its equivalent), it takes typed-ahead characters anyway.

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.

Builtin commands¶

%job

A synonym for the fg builtin command.

%job &

A synonym for the bg builtin command.

:

Does nothing, successfully.

@

 

@ name = expr

 

@ name[index] = expr

 

@ name++|--

 

@ name[index]++|--

The first form prints the values of all shell variables.

The second form assigns the value of expr to name.

The third form assigns the value of expr to the index'th component of name; both name and its index'th component must already exist.

expr may contain the operators ‘*’, ‘+’, etc., as in C. If expr contains ‘<’, ‘>’, ‘&’, or ‘|’ then at least that part of expr must be placed within (‘’ and ‘’). Note that the syntax of expr has nothing to do with that described under Expressions.

The fourth and fifth forms increment (‘++’) or decrement (‘--’) name or its index'th component.

The space between ‘@’ and name is required. The spaces between name and ‘=’ and between ‘=’ and expr are optional. Components of expr must be separated by spaces.

alias [name [wordlist]]

Without arguments, prints all aliases.

With name, prints the alias for name.

With name and wordlist, assigns wordlist as the alias of name. wordlist is command and filename substituted.

name may not be ‘alias’ or ‘unalias’. See also the unalias builtin command.

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, because systems other than the VAX may use a different memory allocator.

bg [%job ...]

Puts the specified jobs (or, without arguments, the current job) into the background, continuing each if it is stopped. job may be a number, a string, ‘’, ‘%’, ‘+’, or ‘-’ as described under Jobs.

bindkey [-l|-d|-e|-v|-u] (+)

 

bindkey [-a] [-b] [-k] [-r] [--] key (+)

 

bindkey [-a] [-b] [-k] [-c|-s] [--] key command (+)

The first form either lists all bound keys and the editor command to which each is bound, lists a description of the commands, or binds all keys to a specific mode.

The second form lists the editor command to which key is bound.

The third form binds the editor command command to key.

Supported bindkey options:

Option

bindkey description

-a

Lists or changes key-bindings in the alternative key map. This is the key map used in vimode 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).

-c

command is interpreted as a builtin or external command instead of an editor command.

-d

Binds all keys to the standard bindings for the default editor, as per -e and -v.

-e

Binds all keys to emacs(1)-style bindings. Unsets vimode.

-k

key is interpreted as a symbolic arrow key name, which may be one of ‘down’, ‘up’, ‘left’, or ‘right’.

-l

Lists all editor commands and a short description of each.

-r

Removes key's binding. Be careful: ‘bindkey -r’ does not bind key to self-insert-command, it unbinds key completely.

-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.

-u (or any invalid option)

Prints a usage message.

-v

Binds all keys to vi(1)-style bindings. Sets vimode.

--

Forces a break from option processing, so the next word is taken as key even if it begins with ‘-’.

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:

Escape

Description

\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 ‘^’.

bs2cmd bs2000-command (+)

Passes bs2000-command to the BS2000 command interpreter for execution. Only non-interactive commands can be executed, and it is not possible to execute any command that would overlay the image of the current process, like /EXECUTE or /CALL-PROCEDURE. (BS2000 only)

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.

builtins (+)

Prints the names of all builtin commands.

bye (+)

A synonym for the logout builtin command. Available only if the shell was so compiled; see the version shell variable.

case label:

A label in a switch statement as discussed below.

cd [-p] [-l] [-n|-v] [--] [name]

If a directory name is given, changes the shell's working directory to name. If not, changes to home, unless the cdtohome variable is not set, in which case a name is required. If name is ‘-’ it is interpreted as the previous working directory (see Other substitutions (+)). (+) If name is not a subdirectory of the current directory (and does not begin with ‘/’, ‘./’ or ‘../’), 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 ‘/’ or ‘.’, then this is tried to see if it is a directory, and the -p option is implied.

With -p, prints the final directory stack, just like dirs. The -l, -n, and -v flags have the same effect on cd as on dirs, and they imply -p (+). Using -- forces a break from option processing so the next word is taken as the directory name even if it begins with ‘-’ (+).

See also the implicitcd and cdtohome shell variables.

chdir

A synonym for the cd builtin command.

complete [command [word/pattern/list[:select]/[[suffix]/] ...]] (+)

Without arguments, lists all completions.

With command, lists completions for command.

With command and word ..., defines completions.

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:

word

Completion word

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:

list

Completion item

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, words from only list that match select are considered and the fignore shell variable is ignored. The list types ‘$var’, ‘(...)’, and ‘`...`’ 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.

command invoked from list ‘`...`’ has the additional environment variable COMMAND_LINE set, which contains (as its name indicates) contents of the current (already typed in) command line. One can examine and use contents of the COMMAND_LINE environment variable in a custom script to build more sophisticated completions (see completion for svn(1) included in this package).

Now for some examples. Some commands take only directories as arguments, so there's no point completing plain files.

> complete cd 'p/1/d/'

completes only the first word following ‘cd’ (‘p/1’) with a directory. ‘p’-type completion can also be used to narrow down command completion:

> co[^D]
complete compress
> complete -co* 'p/0/(compress)/'
> co[^D]
> compress

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 with only ambiguous commands.

> complete find 'n/-user/u/'

is an example of ‘n’-type completion. Any word following ‘find’ and immediately following ‘-user’ is completed from the list of users.

> complete cc 'c/-I/d/'

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.

> complete alias 'p/1/a/'
> complete man 'p/*/c/'
> complete set 'p/1/s/'
> complete true 'p/1/x:Truth has no options./'

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,

> complete ftp 'p/1/$hostnames/'
> set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu
> ftp [^C]
> set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net

or from a command run at completion time:

> complete kill 'p/*/`ps | awk \{print\ \$1\}`/'
> kill -9 [^D]
23113 23377 23380 23406 23429 23529 23530 PID

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:

> complete dbx 'p/2/(core)/' 'p/*/c/'

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. Because 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 files with only particular forms as arguments. For example,

> complete cc 'p/*/f:*.[cao]/'

completes ‘cc’ arguments to files ending in only ‘.c’, ‘.a’, or ‘.o’. select can also exclude files, using negation of a glob-pattern as described under Filename substitution. One might use

> complete rm 'p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/'

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.

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

> complete elm c@=@F:$HOME/Mail/@

to complete

elm -f =

as if it were

elm -f ~/Mail/

Note that we used the separator ‘@’ instead of ‘/’ to avoid confusion with the select argument, and we used ‘$HOME’ instead of ‘~’ because home directory substitution works at only the beginning of a word.

suffix is used to add a nonstandard suffix (not space or ‘/’ for directories) to completed words.

> complete finger 'c/*@/$hostnames/' 'p/1/u/@'

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:

> complete find \
'n/-name/f/' 'n/-newer/f/' 'n/-{,n}cpio/f/' \
'n/-exec/c/' 'n/-ok/c/' 'n/-user/u/' \
'n/-group/g/' 'n/-fstype/(nfs 4.2)/' \
'n/-type/(b c d f l p s)/' \
'c/-/(name newer cpio ncpio exec ok user \
group fstype type atime ctime depth inum \
ls mtime nogroup nouser perm print prune \
size xdev)/' \
'p/*/d/'

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 ‘$’). See also the uncomplete builtin command.

continue

Continues 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. It should come after all case labels.

dirs [-l] [-n|-v]

 

dirs -S|-L [filename] (+)

 

dirs -c (+)

The first form prints the directory stack. The top of the stack is at the left and the first directory in the stack is the current directory. With -l, ‘~’ or ‘~name’ in the output is expanded explicitly to home or the pathname of the home directory for user name. (+) With -n, entries are wrapped before they reach the edge of the screen. (+) With -v, entries are printed one per line, preceded by their stack positions. (+) If more than one of -n or -v is given, -v takes precedence. -p is accepted but does nothing.

The second form with -S saves the directory stack to filename as a series of cd and pushd commands. The second form with -L 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 third form clears the directory stack.

echo [-n] word ...

Writes each word to the shell's standard output, separated by spaces and terminated with a newline. The echo_style shell variable may be set to emulate (or not) the flags and escape sequences of the BSD and/or System V versions of echo(1); see Escape sequences (+) and echo(1).

echotc [-sv] arg ... (+)

Exercises the terminal capabilities (see termcap(5)) in arg. For example,

echotc home

sends the cursor to the home position,

echotc cm 3 10

sends it to column 3 and row 10, and

echotc ts 0; echo "This is a test."; echotc fs

prints

This is a test.

in the status line.

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:

> set history=`echotc lines`
> @ history--

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:

> set tosl="`echotc ts 0`"
> set frsl="`echotc fs`"
> echo -n "$tosl";date; echo -n "$frsl"

With -s, nonexistent capabilities return the empty string rather than causing an error. With -v, messages are verbose.

else

 

end

 

endif

 

endsw

See the description of the foreach, if, switch, and while statements below.

eval arg ...

Treats the arguments as input to the shell and executes the resulting command(s) in the context of the current shell. This is usually used to execute commands generated as the result of command or variable substitution, because parsing occurs before these substitutions. See tset(1) for a sample use of eval.

exec command ...

Executes the specified command in place of the current shell.

exit [expr]

The shell exits either with the value of the specified expr (an expression, as described under Expressions) or, without expr, with the value 0.

fg [%job ...]

Brings the specified jobs (or, without arguments, the current job) into the foreground, continuing each if it is stopped. job may be a number, a string, ‘’, ‘%’, ‘+’, or ‘-’ as described under Jobs. See also the run-fg-editor editor command.

filetest -op file ... (+)

Applies op (which is a file inquiry operator as described under File inquiry operators) to each file and returns the results as a space-separated list.

foreach name (wordlist)

 

...

 

end

Successively sets the variable name to each member of wordlist and executes the sequence of commands between this command and the matching end. (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 once prompting with

foreach? 

(or prompt2) 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.

getspath (+)

Prints the system execution path. (TCF only)

getxvers (+)

Prints the experimental version prefix. (TCF only)

glob word ...

Like echo, but the -n parameter is not 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

word is filename and command-substituted to yield a string of the form ‘label’. The shell rewinds its input as much as possible, searches for a line of the form

label:

possibly preceded by blanks or tabs, and continues execution after that line.

hashstat

Prints 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 ‘/’.

On machines without vfork(2), prints only the number and size of hash buckets.

history [-hTr] [n]

 

history -S|-L|-M [filename] (+)

 

history -c (+)

The first form prints the history event list. If n is given only the n most recent events are printed or saved. With -h, the history list is printed without leading numbers. If -T is specified, timestamps are printed also in comment form. This can be used to produce files suitable for loading with

history -L

or

source -h

With -r, the order of printing is most recent first rather than oldest first.

The second form with -S 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. If the second word of savehist is ‘merge’ and the third word is set to ‘lock’, the history file update will be serialized with other shell sessions that would possibly like to merge history at exactly the same time.

The second form with -L 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.

Note that

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 third form clears the history list.

hup [command] (+)

With command, runs command such that it will exit on a hangup signal and arranges for the shell to send it a hangup signal when the shell exits. Note that commands may set their own response to hangups, overriding hup. Without an argument, causes the non-interactive shell only to exit on a hangup for the remainder of the script. See also Signal handling and the nohup builtin command.

if (expr) command

If expr (an expression, as described under Expressions) evaluates true, then command 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 an alias, a pipeline, a command list or a parenthesized command list, but it may have arguments. Input/output redirection occurs even if expr is false and command is thus 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.)

inlib shared-library ... (+)

Adds each shared-library to the current environment. There is no way to remove a shared library. (Domain/OS only)

jobs [-l]

 

jobs -Z [title] (+)

The first form lists the active jobs. With -l, lists process IDs in addition to the normal information. On TCF systems, prints the site on which each job is executing.

The second form with the -Z option sets the process title to title using setproctitle(3) where available. If no title is provided, the process title will be cleared.

kill -l

 

kill [-s signal] %job|pid ...

The first form lists the signal names.

The second form sends the specified signal (or, if none is given, the TERM (terminate) signal) to the specified jobs or processes. job may be a number, a string, ‘’, ‘%’, ‘+’, or ‘-’ as described under Jobs. Signals are either given by number or by name (as given in /usr/include/signal.h, stripped of the prefix ‘SIG’).

There is no default job; entering 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 is sent a CONT (continue) signal as well.

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 for resource 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.

Controllable resource types currently include (if supported by the OS):

resource

Resource description

concurrency

Maximum number of threads for this process.

coredumpsize

Size of the largest core dump that will be created.

cputime

Maximum number of cpu-seconds to be used by each process.

datasize

Maximum growth of the data+stack region via sbrk(2) beyond the end of the program text.

descriptors or openfiles

Maximum number of open files for this process.

filesize

Largest single file which can be created.

heapsize

Maximum amount of memory a process may allocate per brk(2) system call.

kqueues

Maximum number of kqueues allocated for this process.

maxlocks

Maximum number of locks for this user.

maxmessage

Maximum number of bytes in POSIX mqueues for this user.

maxnice

Maximum nice priority the user is allowed to raise mapped from [19...-20] to [0...39] for this user.

maxproc

Maximum number of simultaneous processes for this user id.

maxrtprio

Maximum realtime priority for this user.

maxrttime

Timeout for RT tasks in microseconds for this user.

maxsignal

Maximum number of pending signals for this user.

maxthread

Maximum number of simultaneous threads (lightweight processes) for this user id.

memorylocked

Maximum size which a process may lock into memory using mlock(2).

memoryuse

Maximum amount of physical memory a process may have allocated to it at a given time.

posixlocks

Maximum number of POSIX advisory locks for this user.

pseudoterminals

Maximum number of pseudo-terminals for this user.

sbsize

Maximum size of socket buffer usage for this user.

stacksize

Maximum size of the automatically-extended stack region.

swapsize

Maximum amount of swap space reserved or used for this user.

threads

Maximum number of threads for this process.

vmemoryuse

Maximum amount of virtual memory a process may have allocated to it at a given time (address space).

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’ (1048576 bytes) or ‘g’ or ‘gigabytes’ (1073741824 bytes) 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.

If maximum-use is ‘unlimited’, then the limitation on the specified resource is removed (this is equivalent to the unlimit builtin command).

For both resource names and scale factors, unambiguous prefixes of the names suffice.

log (+)

Prints the watch shell variable and reports on each user indicated in watch who is logged in, regardless of when they last logged in. See also watchlog.

login

Terminates 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

Terminates a login shell. Especially useful if ignoreeof is set.

ls-F [-switch ...] [file ...] (+)

Lists files like

ls -F

but much faster.

ls-F identifies each type of special file in the listing with a special character suffix:

Suffix

Special file type

/

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 (on only systems that have them, of course):

Suffix

Symbolic link type

@

Symbolic link to a non-directory.

>

Symbolic link to a directory.

&

Orphaned (broken) symbolic link.

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, for example

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.

The ls-F builtin can list files using different colors depending on the file type or extension. See the color shell variable and the CLICOLOR_FORCE, LSCOLORS, and LS_COLORS environment variables.

migrate [-site] pid|%jobid ... (+)

 

migrate -site (+)

The first form migrates the process or job to the site specified or the default site determined by the system path. (TCF only)

The second form is equivalent to

migrate -site $$

in that it migrates the current process to the specified site. Migrating the shell itself can cause unexpected behavior, because the shell does not like to lose its tty. (TCF only)

newgrp [-] [group] (+)

Equivalent to

exec newgrp

as per newgrp(1). Available only if the shell was so compiled; see the version shell variable.

nice [+number] [command]

Increments the scheduling priority for the shell by number, or, without number, by 4. With command, runs command at the appropriate priority. The greater the number, the less cpu the process gets. The super-user may decrement the 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 [command]

With command, runs command such that it will ignore hangup signals. Note that commands may set their own response to hangups, overriding nohup.

Without an argument, causes the non-interactive shell only to ignore hangups for the remainder of the script. See also Signal handling and the hup builtin command.

notify [%job ...]

Causes the shell to notify the user asynchronously when the status of any of the specified jobs (or, without %job, the current job) changes, instead of waiting until the next prompt as is usual. job may be a number, a string, ‘’, ‘%’, ‘+’, or ‘-’ as described under Jobs. See also the notify shell variable.

onintr [-|label]

Controls the action of the shell on interrupts. Without arguments, restores the default action of the shell on interrupts, which is to terminate shell scripts or to return to the terminal command input level.

With ‘-’, causes all interrupts to be ignored.

With label, causes the shell to execute a

goto label

when an interrupt is received or a child process terminates because it was interrupted.

onintr is ignored if the shell is running detached and in system startup files (see FILES), where interrupts are disabled anyway.

popd [-p] [-l] [-n|-v] [+n]

Without arguments, pops the directory stack and returns to the new top directory.

With a number ‘+n’, discards the nth entry in the stack.

Finally, all forms of popd print the final directory stack, just like dirs. The pushdsilent shell variable can be set to prevent this and the -p flag can be given to override pushdsilent. The -l, -n, and -v flags have the same effect on popd as on dirs. (+)

printenv [name] (+)

Prints the names and values of all environment variables or, with name, the value of the environment variable name.

pushd [-p] [-l] [-n|-v] [name|+n]

Without arguments, exchanges the top two elements of the directory stack. If pushdtohome is set, pushd without arguments acts as

pushd ~

like cd. (+)

With name, pushes the current working directory onto the directory stack and changes to name. If name is ‘-’ it is interpreted as the previous working directory (see Filename substitution). (+) If dunique is set, pushd removes any instances of name from the stack before pushing it onto the stack. (+)

With a number ‘+n’, rotates the nth element of the directory stack around to be the top element and changes to it. If dextract is set, however,

pushd +n

extracts the nth directory, pushes it onto the top of the stack and changes to it. (+)

Finally, all forms of pushd print the final directory stack, just like dirs. The pushdsilent shell variable can be set to prevent this and the -p flag can be given to override pushdsilent. The -l, -n, and -v flags have the same effect on pushd as on dirs. (+)

rehash

Causes the internal hash table of the contents of the directories in the path variable to be recomputed. This is needed if the autorehash shell variable is not set and new commands are added to directories in path while you are logged in. With autorehash, a new command will be found automatically, except in the special case where another command of the same name which is located in a different directory already exists in the hash table. Also flushes the cache of home directories built by tilde expansion.

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.

rootnode //nodename (+)

Changes the rootnode to //nodename, so that ‘/’ will be interpreted as ‘//nodename’. (Domain/OS only)

sched (+)

 

sched [+]hh:mm command (+)

 

sched -n (+)

The first form prints the scheduled-event list. The sched shell variable may be set to define the format in which the scheduled-event list is printed.

The second form adds command to the scheduled-event list. For example,

> sched 11:00 echo It\'s eleven o\'clock.

causes the shell to echo

It's eleven o'clock.

at 11 AM.

The time may be in 12-hour AM/PM format

> sched 5pm set prompt='[%h] It\'s after 5; go home: >'

or may be relative to the current time:

> sched +2:15 /usr/lib/uucp/uucico -r1 -sother

A relative time specification may not use AM/PM format.

The third form removes item n from the event list:

> sched
1  Wed Apr  4 15:42  /usr/lib/uucp/uucico -r1 -sother
2  Wed Apr  4 17:00  set prompt=[%h] It's after 5; go home: >
> sched -2
> sched
1  Wed Apr  4 15:42  /usr/lib/uucp/uucico -r1 -sother

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 [-r] [-f|-l] name=(wordlist) ... (+)

 

set name[index]=word ...

 

set -r (+)

 

set -r name ... (+)

 

set -r name=word ... (+)

The first form of the command prints the value of all shell variables. Variables which contain more than a single word 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 name to the list of words in wordlist.

In all cases the value is command and filename expanded. If -r is specified, the value is set read-only. If -f or -l are specified, set only unique words keeping their order. -f prefers the first occurrence of a word, and -l the last.

The fifth form sets the index'th component of name to word; this component must already exist.

The sixth form lists only the names of all shell variables that are read-only.

The seventh form makes name read-only, whether or not it has a value.

The eighth form is the same as the third form, but make name read-only at the same time.

These arguments can be repeated to set and/or make read-only multiple variables in a single set command. Note, however, that variable expansion happens for all arguments before any setting occurs. Note also that ‘=’ can be adjacent to both name and word or separated from both by whitespace, but cannot be adjacent to only one or the other. See also the unset builtin command.

setenv [name [value]]

Without arguments, prints the names and values of all environment variables.

With name, sets the environment variable name to value or, without value, to the null string.

setpath path (+)

Equivalent to setpath(1). (Mach only)

setspath LOCAL|site|cpu ... (+)

Sets the system execution path. (TCF only)

settc cap value (+)

Tells the shell to believe that the terminal capability cap (as defined in termcap(5)) has the value value. No sanity checking is done. Concept terminal users may have to

settc xn no

to get proper wrapping at the rightmost column.

setty [-d|-q|-x] [-a] [[+|-]mode] (+)

Controls which tty modes (see Terminal management (+)) the shell does not allow to change. -d, -q, or -x tells setty to act on the ‘edit’, ‘quote’, or ‘execute’ set of tty modes respectively; without -d, -q, or -x, ‘execute’ is used.

Without other arguments, setty lists the modes in the chosen set which are fixed on (‘+mode’) or off (‘-mode’). The available modes, and thus the display, vary from system to system. With -a, lists all tty modes in the chosen set whether or not they are fixed. With +mode, -mode, or mode, fixes mode on or off or removes control from mode in the chosen set. For example,

setty +echok echoe

fixes ‘echok’ mode on and allows commands to turn ‘echoe’ mode on or off, both when the shell is executing commands.

setxvers [string] (+)

Set the experimental version prefix to string, or removes it if string is omitted. (TCF only)

shift [variable]

Without arguments, discards argv[1] and shifts the members of argv to the left. It is an error for argv not to be set or to have fewer than one word as value.

With variable, performs the same function on variable.

source [-h] name [args ...]

The shell reads and executes commands from name. The commands are not placed on the history list. If any args are given, they are placed in argv. (+) 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.

With -h, commands are placed on the history list instead of being executed, much like

history -L

stop %job|pid ...

Stops the specified jobs or processes which are executing in the background. job may be a number, a string, ‘’, ‘%’, ‘+’, or ‘-’ as described under Jobs.

There is no default job; entering just

stop

does not stop the current job.

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.

telltc (+)

Lists the values of all terminal capabilities (see termcap(5)).

termname [termtype] (+)

Tests if termtype (or the current value of TERM if no termtype is given) has an entry in the hosts termcap(5) or terminfo(5) database. Prints the terminal type to stdout and returns 0 if an entry is present otherwise returns 1.

time [command]

Executes command (which must be a simple command, not an alias, a pipeline, a command list or a parenthesized command list) and prints a time summary as described under the time variable. If necessary, an extra shell is created to print the time statistic when the command completes.

Without command, prints a time summary for the current shell and its children.

umask [value]

Sets the file creation mask to value, which is given in octal. Common values for the mask are 002, giving all access to the group and read and execute access to others, and 022, giving read and execute access to the group and others.

Without value, prints the current file creation mask.

unalias pattern

Removes all aliases whose names match pattern. Thus

unalias *

removes all aliases. It is not an error for nothing to be unaliased.

uncomplete pattern (+)

Removes all completions whose names match pattern. Thus

uncomplete *

removes all completions. It is not an error for nothing to be uncompleted.

unhash

Disables use of the internal hash table to speed location of executed programs.

universe universe (+)

Sets the universe to universe. (Masscomp/RTU only)

unlimit [-hf] [resource]

Removes the limitation on resource or, if no resource is specified, all resource limitations.

With -h, the corresponding hard limits are removed. Only the super-user may do this.

Note that unlimit may not exit successful, since most systems do not allow descriptors to be unlimited.

With -f errors are ignored.

unset pattern

Removes all variables whose names match pattern, unless they are read-only. Thus

unset *

removes all variables unless they are read-only; this is a bad idea.

It is not an error for nothing to be unset.

unsetenv pattern

Removes all environment variables whose names match pattern. Thus

unsetenv *

removes all environment variables; this is a bad idea.

It is not an error for nothing to be unsetenved.

ver [systype [command]] (+)

Without arguments, prints SYSTYPE.

With systype, sets SYSTYPE to systype.

With systype and command, executes command under systype. systype may be ‘bsd4.3’ or ‘sys5.3’.

(Domain/OS only)

wait

The shell waits for all background jobs. If the shell is interactive, an interrupt will disrupt the wait and cause the shell to print the names and job numbers of all outstanding jobs.

warp universe (+)

Sets the universe to universe. (Convex/OS only)

watchlog (+)

An alternate name for the log builtin command. Available only if the shell was so compiled; see the version shell variable.

where command (+)

Reports all known instances of command, including aliases, builtins and executables in path.

which command (+)

Displays the command that will be executed by the shell after substitutions, path searching, etc. The builtin command is just like which(1), but it correctly reports tcsh aliases and builtins and is 10 to 100 times faster. See also the which-command editor command.

while (expr)

 

...

 

end

Executes the commands between the while and the matching end while expr (an expression, as described under Expressions) evaluates non-zero. while and end must appear alone on their input lines. break and continue may be used to terminate or continue the loop prematurely. If the input is a terminal, the user is prompted the first time through the loop as with foreach.

Special aliases (+)¶

If set, each of these aliases executes automatically at the indicated time. They are all initially undefined.

Supported special aliases are:

beepcmd

Runs when the shell wants to ring the terminal bell.

cwdcmd

Runs after every change of working directory. For example, if the user is working on an X window system using xterm(1) and a re-parenting window manager that supports title bars such as twm(1) and does

> alias cwdcmd  'echo -n "^[]2;${HOST}:$cwd ^G"'

then the shell will change the title of the running xterm(1) to be the name of the host, a ‘:’, and the full current working directory. A fancier way to do that is

> alias cwdcmd 'echo -n "^[]2;${HOST}:$cwd^G^[]1;${HOST}^G"'

This will put the hostname and working directory on the title bar but only the hostname in the icon manager menu.

Note that putting a cd, pushd, or popd in cwdcmd may cause an infinite loop. It is the author's opinion that anyone doing so will get what they deserve.

jobcmd

Runs before each command gets executed, or when the command changes state. This is similar to postcmd, but it does not print builtins.

> alias jobcmd  'echo -n "^[]2\;\!#:q^G"'

then executing

vi foo.c

will put the command string in the xterm title bar.

helpcommand

Invoked by the run-help editor command. The command name for which help is sought is passed as sole argument. For example, if one does

> alias helpcommand '\!:1 --help'

then the help display of the command itself will be invoked, using the GNU help calling convention.

Currently there is no easy way to account for various calling conventions (e.g., the customary Unix ‘-h’), except by using a table of many commands.

periodic

Runs every tperiod minutes. This provides a convenient means for checking on common but infrequent changes such as new mail. For example, if one does

> set tperiod = 30
> alias periodic checknews

then the checknews(1) program runs every 30 minutes.

If periodic is set but tperiod is unset or set to 0, periodic behaves like precmd.

precmd

Runs just before each prompt is printed. For example, if one does

> alias precmd date

then date(1) runs just before the shell prompts for each command.

There are no limits on what precmd can be set to do, but discretion should be used.

postcmd

Runs before each command gets executed.

> alias postcmd  'echo -n "^[]2\;\!#:q^G"'

then executing

vi foo.c

will put the command string in the xterm title bar.

shell

Specifies the interpreter for executable scripts which do not themselves specify an interpreter. The first word should be a full path name to the desired interpreter (e.g., ‘/bin/csh’ or ‘/usr/local/bin/tcsh’).

Special shell variables¶

The variables described in this section have special meaning to the shell.

The shell sets addsuffix, argv, autologout, csubstnonl, command, echo_style, edit, gid, group, home, loginsh, oid, path, prompt, prompt2, prompt3, shell, shlvl, tcsh, term, tty, uid, user, and version at startup; they do not change thereafter unless changed by the user. The shell updates cwd, dirstack, owd, and status when necessary, and sets logout on logout.

The shell synchronizes group, home, path, shlvl, term, and user with the environment variables of the same names: whenever the environment variable changes the shell changes the corresponding shell variable to match (unless the shell variable is read-only) and vice versa. Note that although cwd and PWD have identical meanings, they are not synchronized in this manner, and that the shell automatically converts between the different formats of path and PATH.

Supported special shell variables are:

addsuffix (+)

If set, filename completion adds ‘/’ to the end of directories and a space to the end of normal files when they are matched exactly. Set by default.

afsuser (+)

If set, autologout's autolock feature uses its value instead of the local username for kerberos authentication.

ampm (+)

If set, all times are shown in 12-hour AM/PM format.

anyerror (+)

This variable selects what is propagated to the value of the status variable. For more information see the description of the status variable below.

argv

The arguments to the shell. Positional parameters are taken from argv, i.e., ‘$1’ is replaced by ‘$argv[1]’, etc. Set by default, but usually empty in interactive shells.

autocorrect (+)

If set, the spell-word editor command is invoked automatically before each completion attempt.

autoexpand (+)

If set, the expand-history editor command is invoked automatically before each completion attempt.

If this is set to ‘onlyhistory’, then only history will be expanded and a second completion will expand filenames.

autolist (+)

If set, possibilities are listed after an ambiguous completion.

If set to ‘ambiguous’, possibilities are listed only when no new characters are added by completion.

autologout (+)

The first word is the number of minutes of inactivity before automatic logout. The optional second word is the number of minutes of inactivity before automatic locking. When the shell automatically logs out, it prints

auto-logout

sets the variable logout to ‘automatic’ and exits. When the shell automatically locks, the user is required to enter their password to continue working. Five incorrect attempts result in automatic logout.

Set to ‘60’ (automatic logout after 60 minutes, and no locking) by default in login and superuser shells, but not if the shell thinks it is running under a window system (i.e., the DISPLAY environment variable is set), the tty is a pseudo-tty (pty) or the shell was not so compiled (see the version shell variable).

Unset autologout or set it to ‘0’ to disable automatic logout. See also the afsuser and logout shell variables.

autorehash (+)

If set, the internal hash table of the contents of the directories in the path variable will be recomputed if a command is not found in the hash table. In addition, the list of available commands will be rebuilt for each command completion or spelling correction attempt if set to ‘complete’ or ‘correct’ respectively; if set to ‘always’, this will be done for both cases.

backslash_quote (+)

If set, backslashes (`\') always quote ‘\’, ‘'’, and ‘"’. This may make complex quoting tasks easier, but it can cause syntax errors in csh(1) scripts.

catalog

The file name of the message catalog. If set, tcsh uses tcsh.${catalog} as a message catalog instead of default tcsh.

cdpath

A list of directories in which cd should search for subdirectories if they aren't found in the current directory.

cdtohome (+)

If not set, cd requires a directory name, and will not go to the home directory if it's omitted. This is set by default.

color

If set, it enables color display for the builtin ls-F and it passes --color=auto to ls(1) (or --color=always if CLICOLOR_FORCE is set). Alternatively, it can be set to only ‘ls-F’ or only ‘ls’ to enable color for a specific command. Setting it to nothing is equivalent to setting it to ‘(ls-F ls)’. Color is disabled if the output is not directed to a terminal, unless CLICOLOR_FORCE is set.

colorcat

If set, it enables color escape sequence for NLS message files, and display colorful NLS messages.

command (+)

If set, the command which was passed to the shell with the -c flag.

compat_expr (+)

If set, the shell will evaluate expressions right to left, like the original csh(1).

complete (+)

If set to ‘igncase’, the completion becomes case insensitive.

If set to ‘enhance’, completion ignores case and considers hyphens and underscores to be equivalent; it will also treat periods, hyphens and underscores (‘.’, ‘-’, and ‘_’) as word separators.

If set to ‘Enhance’, completion matches uppercase and underscore characters explicitly and matches lowercase and hyphens in a case-insensitive manner; it will treat periods, hyphens and underscores as word separators.

continue (+)

If set to a list of commands, the shell will continue the listed commands, instead of starting a new one.

continue_args (+)

Same as continue, but the shell will execute:

echo `pwd` $argv > ~/.<cmd>_pause; %<cmd>

correct (+)

If set to ‘cmd’, commands are automatically spelling-corrected.

If set to ‘complete’, commands are automatically completed.

If set to ‘all’, the entire command line is corrected.

csubstnonl (+)

If set, newlines and carriage returns in command substitution are replaced by spaces. Set by default.

cwd

The full pathname of the current directory. See also the dirstack and owd shell variables.

dextract (+)

If set,

pushd +n

extracts the nth directory from the directory stack rather than rotating it to the top.

dirsfile (+)

The default location in which

dirs -S

and

dirs -L

look for a history file. If unset, ~/.cshdirs is used. Because only ~/.tcshrc is normally sourced before ~/.cshdirs, dirsfile should be set in ~/.tcshrc rather than ~/.login.

dirstack (+)

An array of all the directories on the directory stack. ‘$dirstack[1]’ is the current working directory, ‘$dirstack[2]’ the first directory on the stack, etc. Note that the current working directory is ‘$dirstack[1]’ but ‘=0’ in directory stack substitutions, etc. One can change the stack arbitrarily by setting dirstack, but the first element (the current working directory) is always correct. See also the cwd and owd shell variables.

dspmbyte (+)

Has an effect only if ‘dspm’ is listed as part of the version shell variable.

If set to ‘euc’, it enables display and editing EUC-kanji(Japanese) code.

If set to ‘sjis’, it enables display and editing Shift-JIS(Japanese) code.

If set to ‘big5’, it enables display and editing Big5(Chinese) code.

If set to ‘utf8’, it enables display and editing Utf8(Unicode) code.

If set to exactly 256 characters in the following format, it enables display and editing of original multi-byte code format:

> set dspmbyte = NNN...[250 characters]...NNN

Each character N in the 256 character value corresponds (from left to right) to the ASCII codes 0x00, 0x01, 0x02, ..., 0xfd, 0xfe, 0xff at the same index. Each character is set to number 0, 1, 2 or 3, with the meaning:

Number

Multi-byte purpose

0

Not used for multi-byte characters.

1

Used for the first byte of a multi-byte character.

2

Used for the second byte of a multi-byte character.

3

Used for both the first byte and second byte of a multi-byte character.

For example, if set to 256 characters starting with ‘001322’, the value is interpreted as:

Character	ASCII	Multi-byte character use
0	0x00	Not used.
0	0x01	Not used.
1	0x02	First byte.
3	0x03	First byte and second byte.
2	0x04	Second byte.
2	0x05	Second byte.

The GNU coreutils version of ls(1) cannot display multi-byte filenames without the -N (--literal) option. If you are using this version, set the second word of dspmbyte to ‘ls’. If not, for example,

ls-F -l

cannot display multi-byte filenames.

Note that this variable can only be used if KANJI and DSPMBYTE has been defined at compile time.

dunique (+)

If set, pushd removes any instances of name from the stack before pushing it onto the stack.

echo

If set, each command with its arguments is echoed just before it is executed. For non-builtin commands all expansions occur before echoing. Builtin commands are echoed before command and filename substitution, because these substitutions are then done selectively. Set by the -x command line option.

echo_style (+)

The style of the echo builtin. May be set to:

Value

echo style

bsd

Don't echo a newline if the first argument is -n; the default for csh(1).

sysv

Recognize backslashed escape sequences in echo strings.

both

Recognize both the -n flag and backslashed escape sequences; the default for tcsh.

none

Recognize neither.

Set by default to the local system default. The BSD and System V options are described in the echo(1) man pages on the appropriate systems.

edit (+)

If set, the command-line editor is used. Set by default in interactive shells.

editors (+)

A list of command names for the run-fg-editor editor command to match. If not set, the EDITOR (‘ed’ if unset) and VISUAL (‘vi’ if unset) environment variables will be used instead.

ellipsis (+)

If set, the ‘%c’, ‘%.’, and ‘%C’ prompt sequences (see the prompt shell variable) indicate skipped directories with an ellipsis (‘...’) instead of ‘/<skipped>’.

euid (+)

The user's effective user ID.

euser (+)

The first matching passwd entry name corresponding to the effective user ID.

fignore (+)

Lists file name suffixes to be ignored by completion.

filec

In tcsh, completion is always used and this variable is ignored by default.

If edit is unset, then the traditional csh(1) completion is used.

If set in csh(1), filename completion is used.

gid (+)

The user's real group ID.

globdot (+)

If set, wild-card glob patterns will match files and directories beginning with ‘.’ except for ‘.’ and ‘..’.

globstar (+)

If set, the ‘**’ and ‘***’ file glob patterns will match any string of characters including ‘/’ traversing any existing sub-directories. For example,

ls **.c

will list all the .c files in the current directory tree.

If used by itself, it will match zero or more sub-directories. For example,

ls /usr/include/**/time.h

will list any file named ‘time.h’ in the /usr/include directory tree; whereas

ls /usr/include/**time.h

will match any file in the /usr/include directory tree ending in ‘time.h’.

To prevent problems with recursion, the ‘**’ glob-pattern will not descend into a symbolic link containing a directory. To override this, use ‘***’.

group (+)

The user's group name.

highlight

If set, the incremental search match (in i-search-back and i-search-fwd) and the region between the mark and the cursor are highlighted in reverse video.

Highlighting requires more frequent terminal writes, which introduces extra overhead. If you care about terminal performance, you may want to leave this unset.

histchars

A string value determining 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.

histdup (+)

Controls handling of duplicate entries in the history list.

If set to ‘all’ only unique history events are entered in the history list.

If set to ‘prev’ and the last history event is the same as the current command, then the current command is not entered in the history.

If set to ‘erase’ and the same event is found in the history list, that old event gets erased and the current one gets inserted.

Note that the ‘prev’ and ‘all’ options renumber history events so there are no gaps.

histfile (+)

The default location in which

history -S

and

history -L

look for a history file.

If unset, ~/.history is used.

histfile is useful when sharing the same home directory between different machines, or when saving separate histories on different terminals. Because only ~/.tcshrc is normally sourced before ~/.history, histfile should be set in ~/.tcshrc rather than ~/.login.

histlit (+)

If set, builtin and editor commands and the savehist mechanism use the literal (unexpanded) form of lines in the history list. See also the toggle-literal-history editor command.

history

The first word indicates the number of history events to save.

The optional second word (+) indicates the format in which history is printed; if not given, ‘%h\t%T\t%R\n’ is used. The format sequences are described below under prompt; note the variable meaning of ‘%R’.

Set to ‘100’ by default.

home

Initialized to the home directory of the invoker. The filename expansion of ‘~’ refers to this variable.

ignoreeof

If set to the empty string or ‘0’ and the input device is a terminal, the end-of-file command (usually generated by the user by typing ^D on an empty line) causes the shell to print

Use "exit" to leave tcsh.

instead of exiting. This prevents the shell from accidentally being killed. Historically this setting exited after 26 successive EOF's to avoid infinite loops.

If set to a number ‘n’, the shell ignores n - 1 consecutive end-of-files and exits on the nth (+).

If unset, ‘1’ is used, i.e., the shell exits on a single ^D.

implicitcd (+)

If set, the shell treats a directory name typed as a command as though it were a request to change to that directory.

If set to verbose, the change of directory is echoed to the standard output.

This behavior is inhibited in non-interactive shell scripts, or for command strings with more than one word. Changing directory takes precedence over executing a like-named command, but it is done after alias substitutions. Tilde and variable expansions work as expected.

inputmode (+)

If set to ‘insert’ or ‘overwrite’, puts the editor into that input mode at the beginning of each line.

killdup (+)

Controls handling of duplicate entries in the kill ring.

If set to ‘all’ only unique strings are entered in the kill ring.

If set to ‘prev’ and the last killed string is the same as the current killed string, then the current string is not entered in the ring.

If set to ‘erase’ and the same string is found in the kill ring, the old string is erased and the current one is inserted.

killring (+)

Indicates the number of killed strings to keep in memory.

Set to ‘30’ by default.

If unset or set to less than ‘2’, the shell will only keep the most recently killed string.

Strings are put in the killring by the editor commands that delete (kill) strings of text, e.g. backward-delete-word, kill-line, etc, as well as the copy-region-as-kill command. The yank editor command will yank the most recently killed string into the command-line, while yank-pop (see Editor commands (+)) can be used to yank earlier killed strings.

listflags (+)

If 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, for example

ls -FxA

If the first word contains ‘a’, shows all files (even if they start with a ‘.’).

If the first word contains ‘A’, shows all files but ‘.’ and ‘..’.

If the first word contains ‘x’, sorts across instead of down.

If the second word of listflags is set, it is used as the path to ls(1).

listjobs (+)

If set, all jobs are listed when a job is suspended.

If set to ‘long’, the listing is in long format.

listlinks (+)

If set, the ls-F builtin command shows the type of file to which each symbolic link points.

listmax (+)

The maximum number of items which the list-choices editor command will list without asking first.

listmaxrows (+)

The maximum number of rows of items which the list-choices editor command will list without asking first.

loginsh (+)

Set by the shell if it is a login shell. Setting or unsetting it within a shell has no effect. See also shlvl.

logout (+)

Set by the shell to ‘normal’ before a normal logout, ‘automatic’ before an automatic logout, and ‘hangup’ if the shell was killed by a hangup signal (see Signal handling). See also the autologout shell variable.

mail

A list of files and directories to check for incoming mail, optionally preceded by a numeric word. Before each prompt, if 10 minutes have passed since the last check, the shell checks each file and displays

You have new mail.

(or, if mail contains multiple files,

You have new mail in name.

) if the filesize is greater than zero in size and has a modification time greater than its access time.

If you are in a login shell, then no mail file is reported unless it has been modified after the time the shell has started up, to prevent redundant notifications. Most login programs will tell you whether or not you have mail when you log in.

If a file specified in mail is a directory, the shell will count each file within that directory as a separate message, and will report

You have n mails.

or

You have n mails in name.

as appropriate. This functionality is provided primarily for those systems which store mail in this manner, such as the Andrew Mail System.

If the first word of mail is numeric it is taken as a different mail checking interval, in seconds.

Under very rare circumstances, the shell may report

You have mail.

instead of

You have new mail.

matchbeep (+)

If set to ‘never’, completion never beeps.

If set to ‘nomatch’, it beeps only when there is no match.

If set to ‘ambiguous’, it beeps when there are multiple matches.

If set to ‘notunique’, it beeps when there is one exact and other longer matches.

If unset, ‘ambiguous’ is used.

nobeep (+)

If set, beeping is completely disabled. See also visiblebell.

noclobber

If set, restrictions are placed on output redirection to insure that files are not accidentally destroyed and that ‘>>’ redirections refer to existing files, as described in the Input/output section.

If contains ‘ask’, an interacive confirmation is presented, rather than an error.

If contains ‘notempty’, ‘>’ is allowed on empty files.

noding

If set, disable the printing of

DING!

in the prompt time specifiers at the change of hour.

noglob

If set, Filename substitution and Directory stack substitution (+) are inhibited. This is most useful in shell scripts which do not deal with filenames, or after a list of filenames has been obtained and further expansions are not desirable.

nokanji (+)

If set and the shell supports Kanji (see the version shell variable), it is disabled so that the meta key can be used.

nonomatch

If set, a Filename substitution or Directory stack substitution (+) which does not match any existing files is left untouched rather than causing an error. It is still an error for the substitution to be malformed. For example,

echo [

still gives an error.

nostat (+)

A list of directories (or glob-patterns which match directories; see Filename substitution) that should not be stat(2)ed during a completion operation. This is usually used to exclude directories which take too much time to stat(2), for example /afs.

notify

If set, the shell announces job completions asynchronously. The default is to present job completions just before printing a prompt.

oid (+)

The user's real organization ID. (Domain/OS only)

owd (+)

The old working directory, equivalent to the ‘-’ used by cd and pushd. See also the cwd and dirstack shell variables.

padhour

If set, enable the printing of padding '0' for hours, in 24 and 12 hour formats. E.g., ‘07:45:42’ versus ‘7:45:42’.

parseoctal

To retain compatibily with older versions numeric variables starting with 0 are not interpreted as octal. Setting this variable enables proper octal parsing.

path

A list of directories in which to look for executable commands.

A null word specifies the current directory.

If there is no path variable then only full path names will execute.

path is set by the shell at startup from the PATH environment variable or, if PATH does not exist, to a system-dependent default, such as

(/usr/local/bin /usr/bsd /bin /usr/bin .)

The shell may put ‘.’ first or last in path or omit it entirely depending on how it was compiled; see the version shell variable.

A shell which is given neither the -c nor the -t option hashes the contents of the directories in path after reading ~/.tcshrc and each time path is reset.

If one adds a new command to a directory in path while the shell is active, one may need to do a rehash for the shell to find it.

printexitvalue (+)

If set and an interactive program exits with a non-zero status, the shell prints

Exit status

prompt

The string which is printed before reading each command from the terminal.

prompt may include any of the following formatting sequences (+), which are replaced by the given information:

Format

Prompt information

%/

The current working directory.

%~

The current working directory, but with one's home directory represented by ‘~’ and other users' home directories represented by ‘~user’ as per Filename substitution. ‘~user’ substitution happens only if the shell has already used ‘~user’ in a pathname in the current session.

%c[[0]n], %.[[0]n]

The trailing component of the current working directory, or n trailing components if a digit n is given. If n begins with ‘0’, the number of skipped components precede the trailing component(s) in the format ‘/<skipped>trailing’. If the ellipsis shell variable is set, skipped components are represented by an ellipsis so the whole becomes ‘...trailing’. ‘~’ substitution is done as in ‘%~’ above, but the ‘~’ component is ignored when counting trailing components.

%C

Like ‘%c’, but without ‘~’ substitution.

%h, %!, !

The current history event number.

%M

The full hostname.

%m

The hostname up to the first ‘.’.

%S (%s)

Start (stop) standout mode.

%B (%b)

Start (stop) boldfacing mode.

%U (%u)

Start (stop) underline mode.

%t, %@

The time of day in 12-hour AM/PM format.

%T

Like ‘%t’, but in 24-hour format (but see the ampm shell variable).

%p

The ‘precise’ time of day in 12-hour AM/PM format, with seconds.

%P

Like ‘%p’, but in 24-hour format (but see the ampm shell variable).

\c

c is parsed as in bindkey.

^c

c is parsed as in bindkey.

%%

A single ‘%’.

%n

The user name.

%N

The effective user name.

%j

The number of jobs.

%d

The weekday in ‘Day’ format.

%D

The day in ‘dd’ format.

%w

The month in ‘Mon’ format.

%W

The month in ‘mm’ format.

%y

The year in ‘yy’ format.

%Y

The year in ‘yyyy’ format.

%l

The shell's tty.

%L

Clears from the end of the prompt to end of the display or the end of the line.

%$

Expands the shell or environment variable name immediately after the ‘$’.

%#

‘>’ (or the first character of the promptchars shell variable) for normal users, ‘#’ (or the second character of promptchars) for the superuser.

%{string%}

Includes string as a literal escape sequence. It should be used only to change terminal attributes and should not move the cursor location. This cannot be the last sequence in prompt.

%?

The return code of the command executed just before the prompt.

%R

In prompt2, the status of the parser. In prompt3, the corrected string. In history, the history string.

‘%B’, ‘%S’, ‘%U’, and ‘%{string%}’ are available in only eight-bit-clean shells; see the version shell variable.

The bold, standout and underline sequences are often used to distinguish a superuser shell. For example,

> set prompt = "%m [%h] %B[%@]%b [%/] you rang? "

 

tut [37] [2:54pm] [/usr/accts/sys] you rang? _

 

If ‘%t’, ‘%@’, ‘%T’, ‘%p’, or ‘%P’ is used, and noding is not set, then print

DING!

on the change of hour (i.e, ‘:00’ minutes) instead of the actual time.

Set by default to ‘%# ’ in interactive shells.

prompt2 (+)

The string with which to prompt in while and foreach loops and after lines ending in ‘\’. The same format sequences may be used as in prompt; note the variable meaning of ‘%R’.

Set by default to ‘%R? ’ in interactive shells.

prompt3 (+)

The string with which to prompt when confirming automatic spelling correction. The same format sequences may be used as in prompt; note the variable meaning of ‘%R’.

Set by default to ‘CORRECT>%R (y|n|e|a)? ’ in interactive shells.

promptchars (+)

If set (to a two-character string), the ‘%#’ formatting sequence in the prompt shell variable is replaced with the first character for normal users and the second character for the superuser.

pushdtohome (+)

If set, pushd without arguments does

pushd ~

like cd.

pushdsilent (+)

If set, pushd and popd do not print the directory stack.

recexact (+)

If set, completion completes on an exact match even if a longer match is possible.

recognize_only_executables (+)

If set, command listing displays only files in the path that are executable. Slow.

rmstar (+)

If set, the user is prompted before

rm *

is executed.

rprompt (+)

The string to print on the right-hand side of the screen (after the command input) when the prompt is being displayed on the left. It recognizes the same formatting characters as prompt. It will automatically disappear and reappear as necessary, to ensure that command input isn't obscured, and will appear only if the prompt, command input, and itself will fit together on the first line.

If edit isn't set, then rprompt will be printed after the prompt and before the command input.

savedirs (+)

If set, the shell does

dirs -S

before exiting.

If the first word is set to a number, at most that many directory stack entries are saved.

savehist

If set, the shell does

history -S

before exiting.

If the first word is set to a number, at most that many lines are saved. (The number should be less than or equal to the number history entries; if it is set to greater than the number of history settings, only history entries will be saved.)

If the second word 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 and the most recent events are retained.

If the second word is set to ‘merge’ and the third word is set to ‘lock’, the history file update will be serialized with other shell sessions that would possibly like to merge history at exactly the same time. (+)

sched (+)

The format in which the sched builtin command prints scheduled events; if not given, ‘%h\t%T\t%R\n’ is used. The format sequences are described above under prompt; note the variable meaning of ‘%R’.

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 Builtin and non-builtin command execution.) Initialized to the (system-dependent) home of the shell.

shlvl (+)

The number of nested shells. Reset to 1 in login shells. See also loginsh.

status

The exit status from the last command or backquote expansion, or any command in a pipeline is propagated to status. (This is also the default csh(1) behavior.) This default does not match what POSIX mandates (to return the status of the last command only). To match the POSIX behavior, you need to unset anyerror.

If the anyerror variable is unset, the exit status of a pipeline is determined only from the last command in the pipeline, and the exit status of a backquote expansion is not propagated to status.

If a command terminated abnormally, then 0200 is added to the status. Builtin commands which fail return exit status ‘1’, all other builtin commands return status ‘0’.

symlinks (+)

Can be set to several different values to control symbolic link (‘symlink’) resolution:

If set to ‘chase’, whenever the current directory changes to a directory containing a symbolic link, it is expanded to the real name of the directory to which the link points. This does not work for the user's home directory; this is a bug.

If set to ‘ignore’, the shell tries to construct a current directory relative to the current directory before the link was crossed. This means that

cd

through a symbolic link and then

cd ..

returns one to the original directory. This affects only builtin commands and filename completion.

If set to ‘expand’, the shell tries to fix symbolic links by actually expanding arguments which look like path names. This affects any command, not just builtins. Unfortunately, this does not work for hard-to-recognize filenames, such as those embedded in command options. Expansion may be prevented by quoting. While this setting is usually the most convenient, it is sometimes misleading and sometimes confusing when it fails to recognize an argument which should be expanded. A compromise is to use ‘ignore’ and use the editor command normalize-path (bound by default to ^X-n) when necessary.

Some examples are in order. First, let's set up some play directories:

> cd /tmp
> mkdir from from/src to
> ln -s from/src to/dst

Here's the behavior with symlinks unset,

> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/from

Here's the behavior with symlinks set to ‘chase’,

> cd /tmp/to/dst; echo $cwd
/tmp/from/src
> cd ..; echo $cwd
/tmp/from

Here's the behavior with symlinks set to ‘ignore’,

> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/to

Here's the behavior with symlinks set to ‘expand’.

> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/to
> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ".."; echo $cwd
/tmp/from
> /bin/echo ..
/tmp/to
> /bin/echo ".."
..

Note that ‘expand’ expansion:

1. Works just like ‘ignore’ for builtins like cd.
2. Is prevented by quoting.
3. Happens before filenames are passed to non-builtin commands.

tcsh (+)

The version number of the shell in the format ‘R.VV.PP’, where ‘R’ is the major release number, ‘VV’ the current version, and ‘PP’ the patchlevel.

term

The terminal type. Usually set in ~/.login as described under Startup and shutdown.

time

If set to a number, then the time builtin executes automatically after each command which takes more than that many CPU seconds.

If there is a second word, it is used as a format string for the output of the time builtin.

(u) The following sequences may be used in the time format string:

Format

Time information

%U

The time the process spent in user mode in cpu seconds.

%S

The time the process spent in kernel mode in cpu seconds.

%E

The elapsed (wall clock) time in seconds.

%P

The CPU percentage computed as (%U + %S) / %E.

%W

Number of times the process was swapped.

%X

The average amount in (shared) text space used in Kbytes.

%D

The average amount in (unshared) data/stack space used in Kbytes.

%K

The total space used (%X + %D) in Kbytes.

%M

The maximum memory the process had in use at any time in Kbytes.

%F

The number of major page faults (page needed to be brought from disk).

%R

The number of minor page faults.

%I

The number of input operations.

%O

The number of output operations.

%r

The number of socket messages received.

%s

The number of socket messages sent.

%k

The number of signals received.

%w

The number of voluntary context switches (waits).

%c

The number of involuntary context switches.

Only the first four sequences are supported on systems without BSD resource limit functions. The default time format is ‘%Uu %Ss %E %P %X+%Dk %I+%Oio %Fpf+%Ww’ for systems that support resource usage reporting and ‘%Uu %Ss %E %P’ for systems that do not.

Under Sequent's DYNIX/ptx, ‘%X’, ‘%D’, ‘%K’, ‘%r’, and ‘%s’ are not available, but the following additional sequences are:

Format

Description Sequent DYNIX/ptx time information

%Y

The number of system calls performed.

%Z

The number of pages which are zero-filled on demand.

%i

The number of times a process's resident set size was increased by the kernel.

%d

The number of times a process's resident set size was decreased by the kernel.

%l

The number of read system calls performed.

%m

The number of write system calls performed.

%p

The number of reads from raw disk devices.

%q

The number of writes to raw disk devices.

and the default time format is ‘%Uu %Ss %E %P %I+%Oio %Fpf+%Ww’.

Note that the CPU percentage can be higher than 100% on multi-processors.

tperiod (+)

The period, in minutes, between executions of the periodic special alias.

tty (+)

The name of the tty, or empty if not attached to one.

uid (+)

The user's real user ID.

user

The user's login name.

verbose

If set, causes the words of each command to be printed, after history substitution (if any). Set by the -v command line option.

version (+)

The version ID stamp. It contains the shell's version number (see tcsh), origin, release date, vendor, operating system and machine (see VENDOR, OSTYPE, and MACHTYPE) and a comma-separated list of options which were set at compile time. Options which are set by default in the distribution are noted.

Supported version options include:

Option

Description

8b

The shell is eight bit clean; default.

7b

The shell is not eight bit clean.

wide

The shell is multi-byte encoding clean (like UTF-8).

nls

The system's NLS is used; default for systems with NLS.

lf

Login shells execute /etc/csh.login before instead of after /etc/csh.cshrc and ~/.login before instead of after ~/.tcshrc and ~/.history.

dl

‘.’ is put last in path for security; default.

nd

‘.’ is omitted from path for security.

vi

vi(1)-style editing is the default rather than emacs(1)-style.

dtr

Login shells drop DTR when exiting.

bye

bye is a synonym for logout and log is an alternate name for watchlog.

al

autologout is enabled; default.

kan

Kanji is used if appropriate according to locale settings, unless the nokanji shell variable is set.

sm

The system's malloc(3) is used.

hb

The

#!interpreter arg ...

convention is emulated when executing shell scripts.

ng

The newgrp builtin is available.

rh

The shell attempts to set the REMOTEHOST environment variable.

afs

The shell verifies your password with the kerberos server if local authentication fails. The afsuser shell variable or the AFSUSER environment variable override your local username if set.

An administrator may enter additional strings to indicate differences in the local version.

vimode (+)

If unset, various key bindings change behavior to be more emacs(1)-style: word boundaries are determined by wordchars versus other characters.

If set, various key bindings change behavior to be more vi(1)-style: word boundaries are determined by wordchars versus whitespace versus other characters; cursor behavior depends upon current vi mode (command, delete, insert, replace).

This variable is unset by bindkey -e and set by bindkey -v. vimode may be explicitly set or unset by the user after those bindkey operations if required.

visiblebell (+)

If set, a screen flash is used rather than the audible bell. See also nobeep.

watch (+)

A list of user/terminal pairs to watch for logins and logouts. If either the user is ‘any’ all terminals are watched for the given user and vice versa. Setting watch to

(any any)

watches all users and terminals. For example,

set watch = (george ttyd1 any console $user any)

reports activity of the user ‘george’ on ‘ttyd1’, any user on the console, and oneself (or a trespasser) on any terminal.

Logins and logouts are checked every 10 minutes by default, but the first word of watch can be set to a number to check every so many minutes. For example,

set watch = (1 any any)

reports any login/logout once every minute. For the impatient, the log builtin command triggers a watch report at any time. All current logins are reported (as with the log builtin) when watch is first set.

The who shell variable controls the format of watch reports.

who (+)

The format string for watch messages. The following sequences are replaced by the given information:

Format

Who information

%n

The name of the user who logged in/out.

%a

The observed action, i.e., ‘logged on’, ‘logged off’, or ‘replaced olduser on’.

%l

The terminal (tty) on which the user logged in/out.

%M

The full hostname of the remote host, or ‘local’ if the login/logout was from the local host.

%m

The hostname of the remote host up to the first ‘.’. The full name is printed if it is an IP address or an X Window System display.

‘%M’ and ‘%m’ are available on only systems that store the remote hostname in /etc/utmp.

If unset,

%n has %a %l from %m.

is used, or

%n has %a %l.

on systems which don't store the remote hostname.

wordchars (+)

A list of non-alphanumeric characters to be considered part of a word by the forward-word, backward-word, etc., editor commands.

If unset, the default value is determined based on the state of vimode: if vimode is unset, ‘*?_-.[]~=’ is used as the default; if vimode is set, ‘_’ is used as the default.