TCSH(1) TCSH(1)
NAME
tcsh - C shell with file name completion and command line editing
SYNOPSIS
tcsh [-bcdefFimnqstvVxX] [-Dname[=value]] [arg ...]
tcsh -l
DESCRIPTION
tcsh is an enhanced but completely compatible version of the Berkeley UNIX C shell, csh(1). It is a
command language interpreter usable both as an interactive login shell and a shell script command
processor. It includes a command-line editor (see The command-line editor), programmable word com-pletion completion
pletion (see Completion and listing), spelling correction (see Spelling correction), a history mecha-nism mechanism
nism (see History substitution), job control (see Jobs) and a C-like syntax. The NEW FEATURES sec-tion section
tion describes major enhancements of tcsh over csh(1). Throughout this manual, features of tcsh not
found in most csh(1) implementations (specifically, the 4.4BSD csh) are labeled with `(+)', and fea-tures features
tures which are present in csh(1) but not usually documented are labeled with `(u)'.
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 argu-ment), argument),
ment), 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 ignores ~/.tcshrc, and thus starts faster.
-F The shell uses fork(2) instead of vfork(2) to spawn processes. (Convex/OS only) (+)
-i The shell is interactive and prompts for its top-level input, even if it appears to not be a ter-minal. terminal.
minal. 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 exe-cuted. executed.
cuted. 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 com-patible compatible
patible with this shell, the shell uses such a `standard' shell to execute a script whose first char-acter character
acter 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 ~/.history (or the value of the histfile shell variable), 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 (q.v.) before using tcsh-specific
commands, or can have both a ~/.cshrc and a ~/.tcshrc which sources (see the builtin command)
~/.cshrc. The rest of this manual uses `~/.tcshrc' to mean `~/.tcshrc or, if ~/.tcshrc is not found,
~/.cshrc'.
In the normal case, the shell begins reading commands from the terminal, prompting with `> '. (Pro-
cessing 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 dif-
ferent csh(1) variants; see FILES.
Editing
We first describe The command-line editor. The Completion and listing and Spelling correction sec-
tions 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 GNU Emacs 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. Emacs-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-style bindings en masse.
The shell always binds the arrow keys (as defined in the TERMCAP environment variable) to
down down-history
up up-history
left backward-char
right forward-char
unless doing so would alter another single-character binding. One can set the arrow key escape
sequences to the empty string with settc to prevent these bindings. The ANSI/VT100 sequences for
arrow keys are always bound.
Other key bindings are, for the most part, what Emacs and vi(1) users would expect and can easily be
displayed by bindkey, so there is no need to list them here. Likewise, bindkey can list the editor
commands with a short description of each.
Note that editor commands do not have the same notion of a ``word'' as does the shell. The editor
delimits words with any non-alphanumeric characters not in the shell variable wordchars, while the
shell recognizes only whitespace and some of the characters with special meanings to it, listed under
Lexical structure.
Completion and listing (+)
The shell is often able to complete words when given a unique abbreviation. Type part of a word (for
example `ls /usr/lost') and hit the tab key to run the complete-word editor command. The shell com-
pletes the filename `/usr/lost' to `/usr/lost+found/', replacing the incomplete word with the com-
plete word in the input buffer. (Note the terminal `/'; completion adds a `/' to the end of com-
pleted directories and a space to the end of other completed words, to speed typing and provide a
visual indicator of successful completion. The addsuffix shell variable can be unset to prevent
this.) If no match is found (perhaps `/usr/lost+found' doesn't exist), the terminal bell rings. If
the word is already complete (perhaps there is a `/usr/lost' on your system, or perhaps you were
thinking too far ahead and typed the whole thing) a `/' or space is added to the end if it isn't
already there.
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 `em[tab]' would
complete `em' to `emacs' if emacs were the only command on your system beginning with `em'. Comple-
tion can find a command in any directory in path or if given a full pathname. Typing `echo $ar[tab]'
would complete `$ar' to `$argv' if no other variable began with `ar'.
The shell parses the input buffer to determine whether the word you want to complete should be com-
pleted as a filename, command or variable. The first word in the buffer and the first word following
`;', `|', `|&', `&&' or `||' is considered to be a command. A word beginning with `$' is considered
to be a variable. Anything else is a filename. An empty line is `completed' as a filename.
You can list the possible completions of a word at any time by typing `^D' to run the delete-char-or-
list-or-eof editor command. The shell lists the possible completions using the ls-F builtin (q.v.)
and reprints the prompt and unfinished command line, for example:
> 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 com-
pletion fails:
> set autolist
> nm /usr/lib/libt[tab]
libtermcap.a@ libtermlib.a@
> nm /usr/lib/libterm
If autolist is set to `ambiguous', choices are listed only when completion fails and adds no new
characters to the word being completed.
A filename to be completed can contain variables, your own or others' home directories abbreviated
with `~' (see Filename substitution) and directory stack entries abbreviated with `=' (see Directory
stack substitution). For example,
> 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 ignoreeof is set, does noth-
ing. `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 peri-
ods, 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 `mail -f c.l.c[tab]', it would be completed to `mail -f comp.lang.c', and ^D would list
`comp.lang.c' and `comp.lang.c++'. `mail -f c..c++[^D]' would list `comp.lang.c++' and
`comp.std.c++'. Typing `rm a--file[^D]' in the following directory
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.
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. rec-
ognize_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 vari-
able 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 comple-
tion 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 correc-
tion does not register a misspelling.
Like completion, spelling correction works anywhere in the line, pushing the rest of the line to the
right and possibly leaving extra characters to the right of the cursor.
Beware: spelling correction is not guaranteed to work the way one intends, and is provided mostly as
an experimental feature. Suggestions and improvements are welcome.
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 descrip-
tions 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
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.
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.
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.
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.
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.
down-history (down-arrow, ^N)
Like up-history, but steps down, stopping at the original input line.
end-of-file (not bound)
Signals an end of file, causing the shell to exit unless the ignoreeof shell variable (q.v.)
is set to prevent this. See also delete-char-or-list-or-eof.
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.
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-his-
tory 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:
^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 cur-
rent line in the input buffer, and is then interpreted as normal input. In particular, a
carriage return causes the current line to be executed. Emacs mode only. See also i-search-
fwd and history-search-backward.
i-search-fwd (not bound)
Like i-search-back, but searches forward.
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 argu-
ments, 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 vari-
able.
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 with a name equal to the last compo-
nent of the file name part of the EDITOR or VISUAL environment variables, or, if neither is
set, `ed' or `vi'. 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 com-
mand.help, command.1, command.6, command.8 or command, which should be in one of the directo-
ries 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 char-
acter 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 begin-
ning 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 correc-
tion.
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-arrow, ^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.
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 kill-
ring, such that this string will be considered the most recently killed by a later yank com-
mand. 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 (see below) except History substitution can be prevented by enclosing
the strings (or parts of strings) in which they appear with single quotes or by quoting the crucial
character(s) (e.g., `$' or ``' for Variable substitution or Command substitution respectively) with
`\'. (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 sub-
stitution, 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 Com-
mand substitution below) can a double-quoted string yield parts of more than one word; single-quoted
strings never do. Backward quotes are special: they signal Command substitution (q.v.), which may
result in more than one word.
Quoting complex strings, particularly strings which themselves contain quoting characters, can be
confusing. Remember that quotes need not be used as they are in human writing! It may be easier to
quote not an entire string, but only those parts of the string which need quoting, using different
types of quoting to do so if appropriate.
The backslash_quote shell variable (q.v.) can be set to make backslashes always quote `\', `'', and
`"'. (+) This may make complex quoting tasks easier, but it can cause syntax errors in csh(1)
scripts.
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 com-
mand is always saved, and the history shell variable can be set to a number to save that many com-
mands. 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 neces-
sary to use event numbers, but the current event number can be made part of the prompt by placing an
`!' in the prompt shell variable.
The shell actually saves history in expanded and literal (unexpanded) forms. If the histlit shell
variable is set, commands that display and store history use the literal form.
The history builtin command can print, store in a file, restore and clear the history list at any
time, and the savehist and histfile shell variables can be can be set to store the history list auto-
matically 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 mis-
takes 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 substi-
tutions also occur when an input line begins with `^'. This special abbreviation will be described
later. The characters used to signal history substitution (`!' and `^') can be changed by setting
the histchars shell variable. Any input line which contains a history substitution is printed before
it is executed.
A history substitution may have an ``event specification'', which indicates the event from which
words are to be taken, a ``word designator'', which selects particular words from the chosen event,
and/or a ``modifier'', which manipulates the selected words.
An event specification can be
n A number, referring to a particular event
-n An offset, referring to the event n before the current event
# The current event. This should be used carefully in csh(1), where there is no check for
recursion. tcsh allows 10 levels of recursion. (+)
! The previous event (equivalent to `-1')
s The most recent event whose first word begins with the string s
?s? The most recent event which contains the string s. The second `?' can be omitted if it
is immediately followed by a newline.
For example, consider this bit of someone's history list:
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. `!11' and `!-2' refer to event 11. `!!' refers to the previous event,
12. `!!' can be abbreviated `!' if it is followed by `:' (`:' is described below). `!n' refers to
event 9, which begins with `n'. `!?old?' also refers to event 12, which contains `old'. Without
word designators or modifiers history references simply expand to the entire event, so we might type
`!cp' to redo the copy command or `!!|more' if the `diff' output scrolled off the top of the screen.
History references may be insulated from the surrounding text with braces if necessary. For example,
`!vdoc' would look for a command beginning with `vdoc', and, in this example, not find one, but
`!{v}doc' would expand unambiguously to `vi wumpus.mandoc'. Even in braces, history substitutions do
not nest.
(+) While csh(1) expands, for example, `!3d' to event 3 with the letter `d' appended to it, tcsh
expands it to the last event beginning with `3d'; only completely numeric arguments are treated as
event numbers. This makes it possible to recall events beginning with numbers. To expand `!3d' as
in csh(1) say `!\3d'.
To select words from an event we can follow the event specification by a `:' and a designator for the
desired words. The words of an input line are numbered from 0, the first (usually command) word
being 0, the second word (first argument) being 1, etc. The basic word designators are:
0 The first (command) word
n The nth argument
^ The first argument, equivalent to `1'
$ The last argument
% The word matched by an ?s? search
x-y A range of words
-y Equivalent to `0-y'
* Equivalent to `^-$', but returns nothing if the event contains only 1 word
x* Equivalent to `x-$'
x- Equivalent to `x*', but omitting the last word (`$')
Selected words are inserted into the command line separated by single blanks. For example, the
`diff' command in the previous example might have been typed as `diff !!:1.old !!:1' (using `:1' to
select the first argument from the previous event) or `diff !-2:2 !-2:1' to select and swap the argu-
ments from the `cp' command. If we didn't care about the order of the `diff' we might have said
`diff !-2:1-2' or simply `diff !-2:*'. The `cp' command might have been written `cp wumpus.man
!#:1.old', using `#' to refer to the current event. `!n:- hurkle.man' would reuse the first two
words from the `nroff' command to say `nroff -man hurkle.man'.
The `:' separating the event specification from the word designator can be omitted if the argument
selector begins with a `^', `$', `*', `%' or `-'. For example, our `diff' command might have been
`diff !!^.old !!^' or, equivalently, `diff !!$.old !!$'. However, if `!!' is abbreviated `!', an
argument selector beginning with `-' will be interpreted as an event specification.
A history reference may have a word designator but no event specification. It then references the
previous command. Continuing our `diff' example, we could have said simply `diff !^.old !^' or, to
get the arguments in the opposite order, just `diff !*'.
The word or words in a history reference can be edited, or ``modified'', by following it with one or
more modifiers, each preceded by a `:':
h Remove a trailing pathname component, leaving the head.
t Remove all leading pathname components, leaving the tail.
r Remove a filename extension `.xxx', leaving the root name.
e Remove all but the extension.
u Uppercase the first lowercase letter.
l Lowercase the first uppercase letter.
s/l/r/ Substitute l for r. l is simply a string like r, not a regular expression as in the
eponymous ed(1) command. Any character may be used as the delimiter in place of `/'; a
`\' can be used to quote the delimiter inside l and r. The character `&' in the r is
replaced by l; `\' also quotes `&'. If l is empty (``''), the l from a previous substi-
tution or the s from a previous `?s?' event specification is used. The trailing delim-
iter may be omitted if it is immediately followed by a newline.
& Repeat the previous substitution.
g Apply the following modifier once to each word.
a (+) Apply the following modifier as many times as possible to a single word. `a' and `g' can
be used together to apply a modifier globally. In the current implementation, using the
`a' and `s' modifiers together can lead to an infinite loop. For example, `:as/f/ff/'
will never terminate. This behavior might change in the future.
p Print the new command line but do not execute it.
q Quote the substituted words, preventing further substitutions.
x Like q, but break into words at blanks, tabs and newlines.
Modifiers are applied 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 might have been written as `diff wumpus.man.old !#^:r', using `:r' to
remove `.old' from the first argument on the same line (`!#^'). We could say `echo hello out there',
then `echo !*:u' to capitalize `hello', `echo !*:au' to say it out loud, or `echo !*:agu' to really
shout. We might follow `mail -s "I forgot my password" rot' with `!:s/rot/root' to correct the
spelling of `root' (but see Spelling correction for a different approach).
There is a special abbreviation for substitutions. `^', when it is the first character on an input
line, is equivalent to `!:s^'. Thus we might have said `^rot^root' to make the spelling correction
in the previous example. This is the only history substitution which does not explicitly begin with
`!'.
(+) In csh as such, only one modifier may be applied to each history or variable expansion. In tcsh,
more than one may be used, for example
% mv wumpus.man /usr/man/man1/wumpus.1
% man !$:t:r
man wumpus
In csh, the result would be `wumpus.1:r'. A substitution followed by a colon may need to be insu-
lated from it with braces:
> mv a.out /usr/games/wumpus
> setenv PATH !$:h:$PATH
Bad ! modifier: $.
> setenv PATH !{-2$:h}:$PATH
setenv PATH /usr/games:/bin:/usr/bin:.
The first attempt would succeed in csh but fails in tcsh, because tcsh expects another modifier after
the second colon rather than `$'.
Finally, history can be accessed through the editor as well as through the substitutions just
described. The up- and down-history, history-search-backward and -forward, i-search-back and -fwd,
vi-search-back and -fwd, copy-prev-word and insert-last-word editor commands search for events in the
history list and copy them into the input buffer. The toggle-literal-history editor command switches
between the expanded and literal forms of history lines in the input buffer. expand-history and
expand-line expand history substitutions in the current word and in the entire input buffer respec-
tively.
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 (q.v.) 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 `ls -l' the command `ls /usr' would become `ls -l /usr', the argument
list here being undisturbed. If the alias for `lookup' were `grep !^ /etc/passwd' then `lookup bill'
would become `grep bill /etc/passwd'. Aliases can be used to introduce parser metasyntax. For exam-
ple, `alias print 'pr \!* | lpr'' defines a ``command'' (`print') which pr(1)s its arguments to the
line printer.
Alias substitution is repeated until the first word of the command has no alias. If an alias substi-
tution 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 sys-
tem 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 `set -r' (q.v.) Read-only variables may not be modified or
unset; attempting to do so will cause an error. Once made read-only, a variable cannot be made
writable, so `set -r' should be used with caution. Environment variables cannot be made read-only.
Some variables are set by the shell or referred to by it. For instance, the argv variable is an
image of the shell's argument list, and words of this variable's value are referred to in special
ways. Some of the variables referred to by the shell are toggles; the shell does not care what their
value is, only whether they are set or not. For instance, the verbose variable is a toggle which
causes command input to be echoed. The -v command line option sets this variable. Special shell
variables lists all variables which are referred to by the shell.
Other operations treat variables numerically. The `@' command permits numeric calculations to be
performed and the result assigned to a variable. Variable values are, however, always represented as
(zero or more) strings. For the purposes of numeric operations, the null string is considered to be
zero, and the second and subsequent words of multi-word values are ignored.
After the input line is aliased and parsed, and before each command is executed, variable substitu-
tion is performed keyed by `$' characters. This expansion can be prevented by preceding the `$' with
a `\' except within `"'s where it always occurs, and within `''s where it never occurs. Strings
quoted by ``' are interpreted later (see Command substitution below) so `$' substitution does not
occur there until later, if at all. A `$' is passed unchanged if followed by a blank, tab, or end-
of-line.
Input/output redirections are recognized before variable expansion, and are variable expanded sepa-
rately. Otherwise, the command name and entire argument list are expanded together. It is thus pos-
sible for the first (command) word (to this point) to generate more than one word, the first of which
becomes the command name, and the rest of which become arguments.
Unless enclosed in `"' or given the `:q' modifier the results of variable substitution may eventually
be command and filename substituted. Within `"', a variable whose value consists of multiple words
expands to a (portion of a) single word, with the words of the variable's value separated by blanks.
When the `:q' modifier is applied to a substitution the variable will expand to multiple words with
each word separated by a blank and quoted to prevent later command or filename substitution.
The following metasequences are provided for introducing variable values into the shell input.
Except as noted, it is an error to reference a variable which is not set.
$name
${name} Substitutes the words of the value of variable name, each separated by a blank. Braces insu-
late name from following characters which would otherwise be part of it. Shell variables
have names consisting of up to 20 letters and digits starting with a letter. The underscore
character is considered a letter. If name is not a shell variable, but is set in the envi-
ronment, then that value is returned (but `:' modifiers and the other forms given below are
not available in this case).
$name[selector]
${name[selector]}
Substitutes only the selected words from the value of name. The selector is subjected to `$'
substitution and may consist of a single number or two numbers separated by a `-'. The first
word of a variable's value is numbered `1'. If the first number of a range is omitted it
defaults to `1'. If the last member of a range is omitted it defaults to `$#name'. The
selector `*' selects all words. It is not an error for a range to be empty if the second
argument is omitted or in range.
$0 Substitutes the name of the file from which command input is being read. An error occurs if
the name is not known.
$number
${number}
Equivalent to `$argv[number]'.
$* Equivalent to `$argv', which is equivalent to `$argv[*]'.
The `:' modifiers described under History substitution, except for `:p', can be applied to the sub-
stitutions above. More than one may be used. (+) Braces may be needed to insulate a variable sub-
stitution from a literal colon just as with History substitution (q.v.); any modifiers must appear
within the braces.
The following substitutions can not be modified with `:' modifiers.
$?name
${?name}
Substitutes the string `1' if name is set, `0' if it is not.
$?0 Substitutes `1' if the current input filename is known, `0' if it is not. Always `0' in
interactive shells.
$#name
${#name}
Substitutes the number of words in name.
$# Equivalent to `$#argv'. (+)
$%name
${%name}
Substitutes the number of characters in name. (+)
$%number
${%number}
Substitutes the number of characters in $argv[number]. (+)
$? Equivalent to `$status'. (+)
$$ Substitutes the (decimal) process number of the (parent) shell.
$! Substitutes the (decimal) process number of the last background process started by this
shell. (+)
$_ Substitutes the command line of the last command executed. (+)
$< Substitutes a line from the standard input, with no further interpretation thereafter. It
can be used to read from the keyboard in a shell script. (+) While csh always quotes $<, as
if it were equivalent to `$<:q', tcsh does not. Furthermore, when tcsh is waiting for a line
to be typed the user may type an interrupt to interrupt the sequence into which the line is
to be substituted, but csh does not allow this.
The editor command expand-variables, normally bound to `^X-$', can be used to interactively expand
individual variables.
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 com-
mands which are not internal to the shell, the command name is substituted separately from the argu-
ment 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. 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 speci-
fied 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:
`/usr/source/s1/{oldls,ls}.c' expands to `/usr/source/s1/oldls.c /usr/source/s1/ls.c'. The results
of matches are sorted separately at a low level to preserve this order: `../{memo,*box}' might expand
to `../memo ../box ../mbox'. (Note that `memo' was not sorted with the results of matching `*box'.)
It is not an error when this construct expands to files which do not exist, but it is possible to get
an error from a command to which the expanded list is passed. This construct may be nested. As a
special case the words `{', `}' and `{}' are passed undisturbed.
The character `~' at the beginning of a filename refers to home directories. Standing alone, i.e.,
`~', it expands to the invoker's home directory as reflected in the value of the home shell variable.
When followed by a name consisting of letters, digits and `-' characters the shell searches for a
user with that name and substitutes their home directory; thus `~ken' might expand to `/usr/ken' and
`~ken/chmach' to `/usr/ken/chmach'. If the character `~' is followed by a character other than a
letter or `/' or appears elsewhere than at the beginning of a word, it is left undisturbed. A com-
mand like `setenv MANPATH /usr/man:/usr/local/man:~/lib/man' does not, therefore, do home directory
substitution as one might hope.
It is an error for a glob-pattern containing `*', `?', `[' or `~', with or without `^', not to match
any files. However, only one pattern in a list of glob-patterns must match a file (so that, e.g.,
`rm *.a *.c *.o' would fail only if there were no files in the current directory ending in `.a',
`.c', or `.o'), and if the nonomatch shell variable is set a pattern (or list of patterns) which
matches nothing is left unchanged rather than causing an error.
The noglob shell variable can be set to prevent filename substitution, and the expand-glob editor
command, normally bound to `^X-*', can be used to interactively expand individual filename substitu-
tions.
Directory stack substitution (+)
The directory stack is a list of directories, numbered from zero, used by the pushd, popd and dirs
builtin commands (q.v.). 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 auto-
matically 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 vari-
able (q.v.) is set to `expand'. Quoting prevents this expansion, and the normalize-path editor com-
mand 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 out-
put.
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 sequen-
tially. 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 respec-
tively.
A simple command, pipeline or sequence may be placed in parentheses, `()', to form a simple command,
which may in turn be a component of a pipeline or sequence. A command, pipeline or sequence can be
executed without waiting for it to terminate by following it with an `&'.
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 it is given neither a -c nor a -t option, the shell hashes the names in these
directories into an internal table so that it will 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. If this mechanism has been turned off (via
unhash), if the shell was given a -c or -t argument or in any case for each directory component of
path which does not begin with a `/', the shell concatenates the current working directory with the
given command name to form a path name of a file which it then attempts to execute.
If the file has execute permissions but is not an executable to the system (i.e., it is neither an
executable binary nor a script that specifies its interpreter), then it is assumed to be a file con-
taining shell commands and a new shell is spawned to read it. The shell special alias may be set to
specify an interpreter other than the shell itself.
On systems which do not understand the `#!' script interpreter convention the shell may be compiled
to emulate it; see the version shell variable. If so, the shell checks the first line of the file to
see if it is of the form `#!interpreter arg ...'. If it is, the shell starts interpreter with the
given args and feeds the file to it on standard input.
Input/output
The standard input and standard output of a command may be redirected with the following syntax:
< name Open file name (which is first variable, command and filename expanded) as the standard
input.
<< word Read the shell input up to a line which is identical to word. word is not subjected to vari-
able, filename or command substitution, and each input line is compared to word before any
substitutions are done on this input line. Unless a quoting `\', `"', `' or ``' appears in
word variable and command substitution is performed on the intervening lines, allowing `\' to
quote `$', `\' and ``'. Commands which are substituted have all blanks, tabs, and newlines
preserved, except for the final newline which is dropped. The resultant text is placed in an
anonymous temporary file which is given to the command as standard input.
> name
>! name
>& name
>&! name
The file name is used as standard output. If the file does not exist then it is created; if
the file exists, it is truncated, its previous contents being lost.
If the shell variable noclobber is set, then the file must not exist or be a character spe-
cial file (e.g., a terminal or `/dev/null') or an error results. This helps prevent acciden-
tal destruction of files. In this case the `!' forms can be used to suppress this check.
The forms involving `&' route the diagnostic output into the specified file as well as the
standard output. name is expanded in the same way as `<' input filenames are.
>> name
>>& name
>>! name
>>&! name
Like `>', but appends output to the end of name. If the shell variable noclobber is set,
then it is an error for the file not to exist, unless one of the `!' forms is given.
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, com-
mands run from a file of shell commands have no access to the text of the commands by default; rather
they receive the original standard input of the shell. The `<<' mechanism should be used to present
inline data. This permits shell command scripts to function as components of pipelines and allows
the shell to block read its input. Note that the default standard input for a command run detached
is not the empty file /dev/null, but the original standard input of the shell. If this is a terminal
and if the process attempts to read from the terminal, then the process will block and the user will
be notified (see Jobs).
Diagnostic output may be directed through a pipe with the standard output. Simply use the form `|&'
rather than just `|'.
The shell cannot presently redirect diagnostic output without also redirecting standard output, but
`(command > output-file) >& error-file' is often an acceptable workaround. Either output-file or
error-file may be `/dev/tty' to send output to the terminal.
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 oper-
ate 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
(q.v.) has its own separate syntax.
Logical, arithmetical and comparison operators
These operators are similar to those of C and have the same precedence. They include
|| && | ^ & == != =~ !~ <= >=
< > << >> + - * / % ! ~ ( )
Here the precedence increases to the right, `==' `!=' `=~' and `!~', `<=' `>=' `<' and `>', `<<' and
`>>', `+' and `-', `*' `/' and `%' being, in groups, at the same level. The `==' `!=' `=~' and `!~'
operators compare their arguments as strings; all others operate on numbers. The operators `=~' and
`!~' are like `!=' and `==' except that the right hand side is a glob-pattern (see Filename substitu-
tion) against which the left hand operand is matched. This reduces the need for use of the switch
builtin command in shell scripts when all that is really needed is pattern matching.
Strings which begin with `0' are considered octal numbers. Null or missing arguments are considered
`0'. The results of all expressions are strings, which represent decimal numbers. It is important
to note that no two components of an expression can appear in the same word; except when adjacent to
components of expressions which are syntactically significant to the parser (`&' `|' `<' `>' `(' `)')
they should be surrounded by spaces.
Command exit status
Commands can be executed in expressions and their exit status returned by enclosing them in braces
(`{}'). Remember that the braces should be separated from the words of the command by spaces. Com-
mand 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 com-
mand 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
r Read access
w Write access
x Execute access
X Executable in the path or shell builtin, e.g., `-X ls' and `-X ls-F' are generally true, but
`-X /bin/ls' is not (+)
e Existence
o Ownership
z Zero size
s Non-zero size (+)
f Plain file
d Directory
l Symbolic link (+) *
b Block special file (+)
c Character special file (+)
p Named pipe (fifo) (+) *
S Socket special file (+) *
u Set-user-ID bit is set (+)
g Set-group-ID bit is set (+)
k Sticky bit is set (+)
t file (which must be a digit) is an open file descriptor for a terminal device (+)
R Has been migrated (convex only) (+)
L Applies subsequent operators in a multiple-operator test to a symbolic link rather than to
the file to which the link points (+) *
file is command and filename expanded and then tested to see if it has the specified relationship to
the real user. If file does not exist or is inaccessible or, for the operators indicated by `*', if
the specified file type does not exist on the current system, then all enquiries return false, i.e.,
`0'.
These operators may be combined for conciseness: `-xy file' is equivalent to `-x file && -y file'.
(+) For example, `-fx' is true (returns `1') for plain executable files, but not for directories.
L may be used in a multiple-operator test to apply subsequent operators to a symbolic link rather
than to the file to which the link points. For example, `-lLo' is true for links owned by the invok-
ing user. Lr, Lw and Lx are always true for links and false for non-links. L has a different mean-
ing 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
A Last file access time, as the number of seconds since the epoch
A: Like A, but in timestamp format, e.g., `Fri May 14 16:36:10 1993'
M Last file modification time
M: Like M, but in timestamp format
C Last inode modification time
C: Like C, but in timestamp format
D Device number
I Inode number
F Composite file identifier, in the form device:inode
L The name of the file pointed to by a symbolic link
N Number of (hard) links
P Permissions, in octal, without leading zero
P: Like P, with leading zero
Pmode Equivalent to `-P file & mode', e.g., `-P22 file' returns `22' if file is writable by
group and other, `20' if by group only, and `0' if by neither
Pmode: Like Pmode:, with leading zero
U Numeric userid
U: Username, or the numeric userid if the username is unknown
G Numeric groupid
G: Groupname, or the numeric groupid if the groupname is unknown
Z Size, in bytes
Only one of these operators may appear in a multiple-operator test, and it must be the last. Note
that L has a different meaning at the end of and elsewhere in a multiple-operator test. Because `0'
is a valid return value for many of these operators, they do not return `0' when they fail: most
return `-1', and F returns `:'.
If the shell is compiled with POSIX defined (see the version shell variable), the result of a file
inquiry is based on the permission bits of the file and not on the result of the access(2) system
call. For example, if one tests a file with -w whose permissions would ordinarily allow writing but
which is on a file system mounted read-only, the test will succeed in a POSIX shell but fail in a
non-POSIX shell.
File inquiry operators can also be evaluated with the filetest builtin command (q.v.) (+).
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 `Suspended' and print another prompt. If the listjobs shell variable is set, all jobs will be
listed like the jobs builtin command; if it is set to `long' the listing will be in long format, like
`jobs -l'. You can then manipulate the state of the suspended job. You can put it in the ``back-
ground'' with the bg command or run some other commands and eventually bring the job back into the
``foreground'' with fg. (See also the run-fg-editor editor command.) A `^Z' takes effect immedi-
ately and is like an interrupt in that pending output and unread input are discarded when it is
typed. The wait builtin command causes the shell to wait for all background jobs to complete.
The `^]' key sends a delayed suspend signal, which does not generate a STOP signal until a program
attempts to read(2) it, to the current job. This can usefully be typed ahead when you have prepared
some commands for a job which you wish to stop after it has read them. The `^Y' key performs this
function in csh(1); in tcsh, `^Y' is an editing command. (+)
A job being run in the background stops if it tries to read from the terminal. Background jobs are
normally allowed to produce output, but this can be disabled by giving the command `stty tostop'. If
you set this tty option, then background jobs will stop when they try to produce output like they do
when they try to read input.
There are several ways to refer to jobs in the shell. The character `%' introduces a job name. If
you wish to refer to job number 1, you can name it as `%1'. Just naming a job brings it to the fore-
ground; thus `%1' is a synonym for `fg %1', bringing job 1 back into the foreground. Similarly, say-
ing `%1 &' resumes job 1 in the background, just like `bg %1'. A job can also be named by an unam-
biguous prefix of the string typed in to start it: `%ex' would normally restart a suspended ex(1)
job, if there were only one suspended job whose name began with the string `ex'. It is also possible
to say `%?string' to specify a job whose text contains string, if there is only one such job.
The shell maintains a notion of the current and previous jobs. In output pertaining to jobs, the
current job is marked with a `+' and the previous job with a `-'. The abbreviations `%+', `%', and
(by analogy with the syntax of the history mechanism) `%%' all refer to the current job, and `%-'
refers to the previous job.
The job control mechanism requires that the stty(1) option `new' be set on some systems. It is an
artifact from a `new' implementation of the tty driver which allows generation of interrupt charac-
ters 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 shell command notify which marks a single process so that its status changes will be
immediately reported. By default notify marks the current process; simply say `notify' after start-
ing a background job to mark it.
When you try to leave the shell while jobs are stopped, you will be warned that `You have stopped
jobs.' You may use the jobs command to see what they are. If you do this or immediately try to exit
again, the shell will not warn you a second time, and the suspended jobs will be terminated.
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, periodic, precmd, postcmd, and jobcmd Special aliases can be set, respectively,
to execute commands when the shell wants to ring the bell, when the working directory changes, every
tperiod minutes, before each prompt, before each command gets executed, after each command gets exe-
cuted, and when a job is started or is brought into the foreground.
The autologout shell variable can be set to log out or lock the shell after a given number of minutes
of inactivity.
The mail shell variable can be set to check for new mail periodically.
The printexitvalue shell variable can be set to print the exit status of commands which exit with a
status other than zero.
The rmstar shell variable can be set to ask the user, when `rm *' is typed, if that is really what
was meant.
The time shell variable can be set to execute the time builtin command after the completion of any
process that takes more than a given number of CPU seconds.
The watch and who shell variables can be set to report when selected users log in or out, and the log
builtin command reports on those users at any time.
Native Language System support (+)
The shell is eight bit clean (if so compiled; see the version shell variable) and thus supports char-
acter 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., a 'en_CA.UTF-8' would yield "UTF-8" as a 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 assum-
ing 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 effec-
tively 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 exe-
cution 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 rootn-
ode 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 sev-
eral 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 any-
way.
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 con-
tains li# and co# fields, the shell adjusts them to reflect the new window size.
REFERENCE
The next sections of this manual describe all of the available Builtin commands, Special aliases and
Special shell variables.
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 `()'. 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 compo-
nent.
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 substi-
tuted. 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, contin-
uing 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 (+)
Without options, the first form lists all bound keys and the editor command to which each is
bound, the second form lists the editor command to which key is bound and the third form
binds the editor command command to key. Options include:
-l Lists all editor commands and a short description of each.
-d Binds all keys to the standard bindings for the default editor.
-e Binds all keys to the standard GNU Emacs-like bindings.
-v Binds all keys to the standard vi(1)-like bindings.
-a Lists or changes key-bindings in the alternative key map. This is the key map used in vi
command mode.
-b key is interpreted as a control character written ^character (e.g., `^A') or C-character
(e.g., `C-A'), a meta character written M-character (e.g., `M-A'), a function key written
F-string (e.g., `F-string'), or an extended prefix key written X-character (e.g., `X-A').
-k key is interpreted as a symbolic arrow key name, which may be one of `down', `up', `left'
or `right'.
-r Removes key's binding. Be careful: `bindkey -r' does not bind key to self-insert-command
(q.v.), it unbinds key completely.
-c command is interpreted as a builtin or external command instead of an editor command.
-s command is taken as a literal string and treated as terminal input when key is typed.
Bound keys in command are themselves reinterpreted, and this continues for ten levels of
interpretation.
-- Forces a break from option processing, so the next word is taken as key even if it begins
with '-'.
-u (or any invalid option)
Prints a usage message.
key may be a single character or a string. If a command is bound to a string, the first
character of the string is bound to sequence-lead-in and the entire string is bound to the
command.
Control characters in key can be literal (they can be typed by preceding them with the editor
command quoted-insert, normally bound to `^V') or written caret-character style, e.g., `^A'.
Delete is written `^?' (caret-question mark). key and command can contain backslashed
escape sequences (in the style of System V echo(1)) as follows:
\a Bell
\b Backspace
\e Escape
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
\v Vertical tab
\nnn The ASCII character corresponding to the octal number nnn
`\' nullifies the special meaning of the following character, if it has any, notably `\' and
`^'.
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. If name is `-' it is interpreted as the previous working directory (see Other sub-
stitutions). (+) 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 `/', then this is tried to see if it is a directory.
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. (+)
See also the implicitcd shell variable.
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 etc., 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:
c Current-word completion. pattern is a glob-pattern which must match the beginning of
the current word on the command line. pattern is ignored when completing the current
word.
C Like c, but includes pattern when completing the current word.
n Next-word completion. pattern is a glob-pattern which must match the beginning of
the previous word on the command line.
N Like n, but must match the beginning of the word two before the current word.
p Position-dependent completion. pattern is a numeric range, with the same syntax used
to index shell variables, which must include the current word.
list, the list of possible completions, may be one of the following:
a Aliases
b Bindings (editor commands)
c Commands (builtin or external commands)
C External commands which begin with the supplied path prefix
d Directories
D Directories which begin with the supplied path prefix
e Environment variables
f Filenames
F Filenames which begin with the supplied path prefix
g Groupnames
j Jobs
l Limits
n Nothing
s Shell variables
S Signals
t Plain (``text'') files
T Plain (``text'') files which begin with the supplied path prefix
v Any variables
u Usernames
x Like n, but prints select when list-choices is used.
X Completions
$var Words from the variable var
(...) Words from the given list
`...` Words from the output of command
select is an optional glob-pattern. If given, words from only list that match select are
considered and the fignore shell variable is ignored. The last three types of completion may
not have a select pattern, and x uses select as an explanatory message when the list-choices
editor command is used.
suffix is a single character to be appended to a successful completion. If null, no charac-
ter is appended. If omitted (in which case the fourth delimiter can also be omitted), a
slash is appended to directories and a space to other words.
Now for some examples. Some commands take only directories as arguments, so there's no point
completing plain files.
> 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 $1}' must be quoted explicitly.
One command can have multiple completions:
> complete dbx 'p/2/(core)/' 'p/*/c/'
completes the second argument to `dbx' with the word `core' and all other arguments with com-
mands. Note that the positional completion is specified before the next-word completion.
Because completions are evaluated from left to right, if the next-word completion were speci-
fied first it would always match and the positional completion would never be executed. This
is a common mistake when defining a completion.
The select pattern is useful when a command takes files with only particular forms as argu-
ments. For example,
> complete cc 'p/*/f:*.[cao]/'
completes `cc' arguments to files ending in only `.c', `.a', or `.o'. select can also
exclude files, using negation of a glob-pattern as described under Filename substitution.
One might use
> complete rm 'p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/'
to exclude precious source code from `rm' completion. Of course, one could still type
excluded names manually or override the completion mechanism using the complete-word-raw or
list-choices-raw editor commands (q.v.).
The `C', `D', `F' and `T' lists are like `c', `d', `f' and `t' respectively, but they use the
select argument in a different way: to restrict completion to files beginning with a particu-
lar path prefix. For example, the Elm mail program uses `=' as an abbreviation for one's
mail directory. One might use
> complete elm c@=@F:$HOME/Mail/@
to complete `elm -f =' as if it were `elm -f ~/Mail/'. Note that we used `@' 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 mem-
bers 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 sub-
stitution (beginning with `~') or a variable (beginning with `$'). complete is an experimen-
tal feature, and the syntax may change in future versions of the shell. See also the uncom-
plete 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.
With -S, the second form saves the directory stack to filename as a series of cd and pushd
commands. With -L, the shell sources filename, which is presumably a directory stack file
saved by the -S option or the savedirs mechanism. In either case, dirsfile is used if file-
name is not given and ~/.cshdirs is used if dirsfile is unset.
Note that login shells do the equivalent of `dirs -L' on startup and, if savedirs is set,
`dirs -S' before exiting. Because only ~/.tcshrc is normally sourced before ~/.cshdirs,
dirsfile should be set in ~/.tcshrc rather than ~/.login.
The last form clears the directory stack.
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; see echo(1).
echotc [-sv] arg ... (+)
Exercises the terminal capabilities (see termcap(5)) in args. 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 con-
text 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 of the status variable.
fg [%job ...]
Brings the specified jobs (or, without arguments, the current job) into the foreground, con-
tinuing 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 prema-
turely 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 wordlist
Like echo, but no `\' escapes are recognized and words are delimited by null characters in
the output. Useful for programs which wish to use the shell to filename expand a |
