TCSH(1)
HOME ||
NAME
SYNOPSIS
DESCRIPTION
Argument list processing
Startup and shutdown
Editing
Lexical structure
Substitutions
History substitution
Alias substitution
Variable substitution
Command substitution
Filename substitution
Commands
Builtin and non-builtin command execution
Features
Control flow
Expressions
Command exit status
File inquiry operators
Jobs
Status reporting
Signal handling
REFERENCE
Builtin commands
Special shell variables
ENVIRONMENT
LC_CTYPE
LS_COLORS
FILES
BUGS
THE T IN TCSH
LIMITATIONS
SEE ALSO
VERSION
AUTHORS
THANKS TO
tcsh - C shell with file name completion and command line editing
tcsh [-bcdefFimnqstvVxX] [-Dname[=value]] [arg ...]
tcsh -l
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), pro-
grammable word completion (see Completion and listing), spelling cor-
rection (see Spelling correction), a history mechanism (see History
substitution), job control (see Jobs) and a C-like syntax. The NEW
FEATURES section 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 features 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 remain-
ing arguments will not be interpreted as shell options. This may
be used to pass options to a shell script without confusion or pos-
sible subterfuge. The shell will not run a set-user ID script
without this option.
-c Commands are read from the following argument (which must be
present, and must be a single argument), stored in the command
shell variable for reference, and executed. Any remaining argu-
ments 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 terminal. Shells are interactive without
this option if their inputs and outputs are terminals.
-l The shell is a login shell. Applicable only if -l is the only flag
specified.
-m The shell loads ~/.tcshrc even if it does not belong to the effec-
tive 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 immedi-
ately before execution.
-V Sets the verbose shell variable even before executing ~/.tcshrc.
-X Is to -x as -V is to -v.
After processing of flag arguments, if arguments remain but none of the
-c, -i, -s, or -t options were given, the first argument is taken as
the name of a file of commands, or ``script'', to be executed. The
shell opens this file and saves its name for possible resubstitution by
`$0'. Because many systems use either the standard version 6 or ver-
sion 7 shells whose shell scripts are not compatible with this shell,
the shell uses such a `standard' shell to execute a script whose first
character is not a `#', i.e., that does not start with a comment.
Remaining arguments are placed in the argv shell variable.
Startup and shutdown
A login shell begins by executing commands from the system files
/etc/csh.cshrc and /etc/csh.login. It then executes commands from
files in the user's home directory: first ~/.tcshrc (+) or, if
~/.tcshrc is not found, ~/.cshrc, then ~/.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.source-
forge.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 termi-
nal, prompting with `> '. (Processing of arguments and the use of the
shell to process files containing command scripts are described later.)
The shell repeatedly reads a line of command input, breaks it into
words, places it on the command history list, parses it and executes
each command in the line.
One can log out by typing `^D' on an empty line, `logout' or `login' or
via the shell's autologout mechanism (see the autologout shell vari-
able). 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 sys-
tem for compatibility with different csh(1) variants; see FILES.
Editing
We first describe The command-line editor. The Completion and listing
and Spelling correction sections describe two sets of functionality
that are implemented as editor commands but which deserve their own
treatment. Finally, Editor commands lists and describes the editor
commands specific to the shell and their default bindings.
The command-line editor (+)
Command-line input can be edited using key sequences much like those
used in 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 other-
wise; 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 envi-
ronment 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 recog-
nizes 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 abbrevia-
tion. Type part of a word (for example `ls /usr/lost') and hit the tab
key to run the complete-word editor command. The shell completes the
filename `/usr/lost' to `/usr/lost+found/', replacing the incomplete
word with the complete word in the input buffer. (Note the terminal
`/'; completion adds a `/' to the end of completed 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 vari-
able 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 mid-
dle 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'. Completion can
find a command in any directory in path or if given a full pathname.
Typing `echo $ar[tab]' would complete `$ar' to `$argv' if no other
variable began with `ar'.
The shell parses the input buffer to determine whether the word you
want to complete should be completed as a filename, command or vari-
able. The first word in the buffer and the first word following `;',
`|', `|&', `&&' or `||' is considered to be a command. A word begin-
ning with `$' is considered to be a variable. Anything else is a file-
name. 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 re-
prints the prompt and unfinished command line, for example:
> ls /usr/l[^D]
lbin/ lib/ local/ lost+found/
> ls /usr/l
If the autolist shell variable is set, the shell lists the remaining
choices (if any) whenever completion fails:
> set autolist
> nm /usr/lib/libt[tab]
libtermcap.a@ libtermlib.a@
> nm /usr/lib/libterm
If autolist is set to `ambiguous', choices are listed only when comple-
tion 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 sub-
stitution). 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 nothing.
`M-^D', bound to the editor command list-choices, lists completion pos-
sibilities anywhere on a line, and list-choices (or any one of the
related editor commands that do or don't delete, list and/or log out,
listed under delete-char-or-list-or-eof) can be bound to `^D' with the
bindkey builtin command if so desired.
The complete-word-fwd and complete-word-back editor commands (not bound
to any keys by default) can be used to cycle up and down through the
list of possible completions, replacing the current word with the next
or previous word in the list.
The shell variable fignore can be set to a list of suffixes to be
ignored by completion. Consider the following:
> ls
Makefile condiments.h~ main.o side.c
README main.c meal side.o
condiments.h main.c~
> set fignore = (.o \~)
> emacs ma[^D]
main.c main.c~ main.o
> emacs ma[tab]
> emacs main.c
`main.c~' and `main.o' are ignored by completion (but not listing),
because they end in suffixes in fignore. Note that a `\' was needed in
front of `~' to prevent it from being expanded to home as described
under Filename substitution. fignore is ignored if only one completion
is possible.
If the complete shell variable is set to `enhance', completion 1)
ignores case and 2) considers periods, hyphens and underscores (`.',
`-' and `_') to be word separators and hyphens and underscores to be
equivalent. If you had the following files
comp.lang.c comp.lang.perl comp.std.c++
comp.lang.c++ comp.std.c
and typed `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-cor-
rect the word to be completed (see Spelling correction) before each
completion attempt and correct can be set to complete commands automat-
ically after one hits `return'. matchbeep can be set to make comple-
tion 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 mecha-
nism from stat(2)ing those directories. listmax and listmaxrows can be
set to limit the number of items and rows (respectively) that are
listed without asking first. recognize_only_executables can be set to
make the shell list only executables when listing commands, but it is
quite slow.
Finally, the complete builtin command can be used to tell the shell how
to complete words other than filenames, commands and variables. Com-
pletion and listing do not work on glob-patterns (see Filename substi-
tution), but the list-glob and expand-glob editor commands perform
equivalent functions for glob-patterns.
Spelling correction (+)
The shell can sometimes correct the spelling of filenames, commands and
variable names as well as completing and listing them.
Individual words can be spelling-corrected with the spell-word editor
command (usually bound to M-s and M-S) and the entire input buffer with
spell-line (usually bound to M-$). The correct shell variable can be
set to `cmd' to correct the command name or `all' to correct the entire
line each time return is typed, and autocorrect can be set to correct
the word to be completed before each completion attempt.
When spelling correction is invoked in any of these ways and the shell
thinks that any part of the command line is misspelled, it prompts with
the corrected line:
> set correct = cmd
> lz /usr/bin
CORRECT>ls /usr/bin (y|n|e|a)?
One can answer `y' or space to execute the corrected line, `e' to leave
the uncorrected command in the input buffer, `a' to abort the command
as if `^C' had been hit, and anything else to execute the original line
unchanged.
Spelling correction recognizes user-defined completions (see the com-
plete 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 pos-
sible completions for that position, spelling correction does not reg-
ister a misspelling.
Like completion, spelling correction works anywhere in the line, push-
ing the rest of the line to the right and possibly leaving extra char-
acters 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. Sugges-
tions 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 descriptions
of each editor's key bindings.
The character or characters to which each command is bound by default
is given in parentheses. `^character' means a control character and
`M-character' a meta character, typed as escape-character on terminals
without a meta key. Case counts, but commands that are bound to let-
ters by default are bound to both lower- and uppercase letters for con-
venience.
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 incom-
plete 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 File-
name 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) con-
taining `*', `?', `[]' or `{}'. up-history and down-history
will proceed from the appropriate point in the history list.
Emacs mode only. See also history-search-forward and i-search-
back.
history-search-forward (M-n, M-N)
Like history-search-backward, but searches forward.
i-search-back (not bound)
Searches backward like history-search-backward, copies the
first match into the input buffer with the cursor positioned at
the end of the pattern, and prompts with `bck: ' and the first
match. Additional characters may be typed to extend the
search, i-search-back may be typed to continue searching with
the same pattern, wrapping around the history list if neces-
sary, (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 suc-
cessful search.
escape Ends the search, leaving the current line in the
input buffer.
Any other character not bound to self-insert-command terminates
the search, leaving the current line in the input buffer, and
is then interpreted as normal input. In particular, a carriage
return causes the current line to be executed. Emacs mode
only. See also i-search-fwd and history-search-backward.
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 arguments, e.g., `dbx' and `sh
-x'.
normalize-path (^X-n, ^X-N)
Expands the current word as described under the `expand' set-
ting of the symlinks shell variable.
overwrite-mode (unbound)
Toggles between input and overwrite modes.
run-fg-editor (M-^Z)
Saves the current input line and looks for a stopped job with a
name equal to the last component 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 helpcom-
mand 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 directories listed in the HPATH envi-
ronment variable. If there is more than one help file only the
first is printed.
self-insert-command (text characters)
In insert mode (the default), inserts the typed character into
the input line after the character under the cursor. In over-
write mode, replaces the character under the cursor with the
typed character. The input mode is normally preserved between
lines, but the inputmode shell variable can be set to `insert'
or `overwrite' to put the editor in that mode at the beginning
of each line. See also overwrite-mode.
sequence-lead-in (arrow prefix, meta prefix, ^X)
Indicates that the following characters are part of a multi-key
sequence. Binding a command to a multi-key sequence really
creates two bindings: the first character to sequence-lead-in
and the whole sequence to the command. All sequences beginning
with a character bound to sequence-lead-in are effectively
bound to undefined-key unless bound to another command.
spell-line (M-$)
Attempts to correct the spelling of each word in the input
buffer, like spell-word, but ignores words whose first charac-
ter is one of `-', `!', `^' or `%', or which contain `\', `*'
or `?', to avoid problems with switches, substitutions and the
like. See Spelling correction.
spell-word (M-s, M-S)
Attempts to correct the spelling of the current word as
described under Spelling correction. Checks each component of
a word which appears to be a pathname.
toggle-literal-history (M-r, M-R)
Expands or `unexpands' history substitutions in the input
buffer. See also expand-history and the autoexpand shell vari-
able.
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-pat-
tern, 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 command. Repeating yank-pop
will cycle through the killring any number of times.
Lexical structure
The shell splits input lines into words at blanks and tabs. The spe-
cial 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 charac-
ter(s) (e.g., `$' or ``' for Variable substitution or Command substitu-
tion respectively) with `\'. (Alias substitution is no exception:
quoting in any way any character of a word for which an alias has been
defined prevents substitution of the alias. The usual way of quoting
an alias is to precede it with a backslash.) History substitution is
prevented by backslashes but not by single quotes. Strings quoted with
double or backward quotes undergo Variable substitution and Command
substitution, but other substitutions are prevented.
Text inside single or double quotes becomes a single word (or part of
one). Metacharacters in these strings, including blanks and tabs, do
not form separate words. Only in one special case (see Command substi-
tution 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 back-
slashes 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 command is always saved, and the history
shell variable can be set to a number to save that many commands. The
histdup shell variable can be set to not save duplicate events or con-
secutive duplicate events.
Saved commands are numbered sequentially from 1 and stamped with the
time. It is not usually necessary to use event numbers, but the cur-
rent event number can be made part of the prompt by placing an `!' in
the prompt shell variable.
The shell actually saves history in expanded and literal (unexpanded)
forms. If the histlit shell variable is set, commands that display and
store history use the literal form.
The history builtin command can print, store in a file, restore and
clear the history list at any time, and the savehist and histfile shell
variables can be can be set to store the history list automatically on
logout and restore it on login.
History substitutions introduce words from the history list into the
input stream, making it easy to repeat commands, repeat arguments of a
previous command in the current command, or fix spelling mistakes in
the previous command with little typing and a high degree of confi-
dence.
History substitutions begin with the character `!'. They may begin
anywhere in the input stream, but they do not nest. The `!' may be
preceded by a `\' to prevent its special meaning; for convenience, a
`!' is passed unchanged when it is followed by a blank, tab, newline,
`=' or `('. History substitutions also occur when an input line begins
with `^'. This special abbreviation will be described later. The
characters used to signal history substitution (`!' and `^') can be
changed by setting the histchars shell variable. Any input line which
contains a history substitution is printed before it is executed.
A history substitution may have an ``event specification'', which indi-
cates the event from which words are to be taken, a ``word designa-
tor'', 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 `^-$', but returns nothing if the event con-
tains only 1 word
x* Equivalent to `x-$'
x- Equivalent to `x*', but omitting the last word (`$')
Selected words are inserted into the command line separated by single
blanks. For example, the `diff' command in the previous example might
have been typed as `diff !!:1.old !!:1' (using `:1' to select the first
argument from the previous event) or `diff !-2:2 !-2:1' to select and
swap the arguments from the `cp' command. If we didn't care about the
order of the `diff' we might have said `diff !-2:1-2' or simply `diff
!-2:*'. The `cp' command might have been written `cp wumpus.man
!#:1.old', using `#' to refer to the current event. `!n:- hurkle.man'
would reuse the first two words from the `nroff' command to say `nroff
-man hurkle.man'.
The `:' separating the event specification from the word designator can
be omitted if the argument selector begins with a `^', `$', `*', `%' or
`-'. For example, our `diff' command might have been `diff !!^.old
!!^' or, equivalently, `diff !!$.old !!$'. However, if `!!' is abbre-
viated `!', an argument selector beginning with `-' will be interpreted
as an event specification.
A history reference may have a word designator but no event specifica-
tion. 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 ``modi-
fied'', 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 substitu-
tion or the s from a previous `?s?' event specification is
used. The trailing delimiter may be omitted if it is imme-
diately 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 substitu-
tions.
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 wum-
pus.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 pre-
vious 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 !$:t:r
man wumpus
In csh, the result would be `wumpus.1:r'. A substitution followed by a
colon may need to be insulated from it with braces:
> mv a.out /usr/games/wumpus
> setenv PATH !$:h:$PATH
Bad ! modifier: $.
> setenv PATH !{-2$:h}:$PATH
setenv PATH /usr/games:/bin:/usr/bin:.
The first attempt would succeed in csh but fails in tcsh, because tcsh
expects another modifier after the second colon rather than `$'.
Finally, history can be accessed through the editor as well as through
the substitutions just described. The up- and down-history, history-
search-backward and -forward, i-search-back and -fwd, vi-search-back
and -fwd, copy-prev-word and insert-last-word editor commands search
for events in the history list and copy them into the input buffer.
The toggle-literal-history editor command switches between the expanded
and literal forms of history lines in the input buffer. expand-history
and expand-line expand history substitutions in the current word and in
the entire input buffer respectively.
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 com-
mand, 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 orig-
inal command were the previous input line. If the alias does not con-
tain 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 example, `alias print 'pr \!* | lpr'' defines a
``command'' (`print') which pr(1)s its arguments to the line printer.
Alias substitution is repeated until the first word of the command has
no alias. If an alias substitution does not change the first word (as
in the previous example) it is flagged to prevent a loop. Other loops
are detected and cause an error.
Some aliases are referred to by the shell; see Special aliases.
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 dis-
played and changed with the set and unset commands. The system main-
tains its own list of ``environment'' variables. These can be dis-
played 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 vari-
able. Variable values are, however, always represented as (zero or
more) strings. For the purposes of numeric operations, the null string
is considered to be zero, and the second and subsequent words of multi-
word values are ignored.
After the input line is aliased and parsed, and before each command is
executed, variable substitution is performed keyed by `$' characters.
This expansion can be prevented by preceding the `$' with a `\' except
within `"'s where it always occurs, and within `''s where it never
occurs. Strings quoted by ``' are interpreted later (see Command sub-
stitution below) so `$' substitution does not occur there until later,
if at all. A `$' is passed unchanged if followed by a blank, tab, or
end-of-line.
Input/output redirections are recognized before variable expansion, and
are variable expanded separately. Otherwise, the command name and
entire argument list are expanded together. It is thus possible for
the first (command) word (to this point) to generate more than one
word, the first of which becomes the command name, and the rest of
which become arguments.
Unless enclosed in `"' or given the `:q' modifier the results of vari-
able 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 substitu-
tion the variable will expand to multiple words with each word sepa-
rated by a blank and quoted to prevent later command or filename sub-
stitution.
The following metasequences are provided for introducing variable val-
ues 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 sepa-
rated by a blank. Braces insulate name from following charac-
ters which would otherwise be part of it. Shell variables have
names consisting of up to 20 letters and digits starting with a
letter. The underscore character is considered a letter. If
name is not a shell variable, but is set in the environment,
then that value is returned (but `:' modifiers and the other
forms given below are not available in this case).
$name[selector]
${name[selector]}
Substitutes only the selected words from the value of name.
The selector is subjected to `$' 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 substitutions above. More than one may be
used. (+) Braces may be needed to insulate a variable substitution
from a literal colon just as with History substitution (q.v.); any mod-
ifiers 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 commands
which are not internal to the shell, the command name is substituted
separately from the argument list. This occurs very late, after input-
output redirection is performed, and in a child of the main shell.
Command substitution
Command substitution is indicated by a command enclosed in ``'. The
output from such a command is broken into separate words at blanks,
tabs and newlines, and null words are discarded. The output is vari-
able 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 sub-
stitution to yield only part of a word, even if the command outputs a
complete line.
Filename substitution
If a word contains any of the characters `*', `?', `[' or `{' or begins
with the character `~' 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 charac-
ters, including the null string. The character `?' matches any single
character. The sequence `[...]' matches any one of the characters
enclosed. Within `[...]', a pair of characters separated by `-'
matches any character lexically between the two.
(+) Some glob-patterns can be negated: The sequence `[^...]' matches
any single character not specified by the characters and/or ranges of
characters in the braces.
An entire glob-pattern can also be negated with `^':
> echo *
bang crash crunch ouch
> echo ^cr*
bang ouch
Glob-patterns which do not use `?', `*', or `[]' or which use `{}' or
`~' (below) are not negated correctly.
The metanotation `a{b,c,d}e' is a shorthand for `abe ace ade'. Left-
to-right order is preserved: `/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 direc-
tories. Standing alone, i.e., `~', it expands to the invoker's home
directory as reflected in the value of the home shell variable. When
followed by a name consisting of letters, digits and `-' characters the
shell searches for a user with that name and substitutes their home
directory; thus `~ken' might expand to `/usr/ken' and `~ken/chmach' to
`/usr/ken/chmach'. If the character `~' is followed by a character
other than a letter or `/' or appears elsewhere than at the beginning
of a word, it is left undisturbed. A command like `setenv MANPATH
/usr/man:/usr/local/man:~/lib/man' does not, therefore, do home direc-
tory substitution as one might hope.
It is an error for a glob-pattern containing `*', `?', `[' or `~', with
or without `^', not to match any files. However, only one pattern in a
list of glob-patterns must match a file (so that, e.g., `rm *.a *.c
*.o' would fail only if there were no files in the current directory
ending in `.a', `.c', or `.o'), and if the nonomatch shell variable is
set a pattern (or list of patterns) which matches nothing is left
unchanged rather than causing an error.
The noglob shell variable can be set to prevent filename substitution,
and the expand-glob editor command, normally bound to `^X-*', can be
used to interactively expand individual filename substitutions.
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 automatically on logout and restore it on login. The
dirstack shell variable can be examined to see the directory stack and
set to put arbitrary directories into the directory stack.
The character `=' followed by one or more digits expands to an entry in
the directory stack. The special case `=-' expands to the last direc-
tory in the stack. For example,
> dirs -v
0 /usr/bin
1 /usr/spool/uucp
2 /usr/accts/sys
> echo =1
/usr/spool/uucp
> echo =0/calendar
/usr/bin/calendar
> echo =-
/usr/accts/sys
The noglob and nonomatch shell variables and the expand-glob editor
command apply to directory stack as well as filename substitutions.
Other substitutions (+)
There are several more transformations involving filenames, not
strictly related to the above but mentioned here for completeness. Any
filename may be expanded to a full path when the symlinks variable
(q.v.) is set to `expand'. Quoting prevents this expansion, and the
normalize-path editor command does it on demand. The normalize-command
editor command expands commands in PATH into full paths on demand.
Finally, cd and pushd interpret `-' as the old working directory
(equivalent to the shell variable owd). This is not a substitution at
all, but an abbreviation recognized by only those commands. Nonethe-
less, it too can be prevented by quoting.
Commands
The next three sections describe how the shell executes commands and
deals with their input and output.
Simple commands, pipelines and sequences
A simple command is a sequence of words, the first of which specifies
the command to be executed. A series of simple commands joined by `|'
characters forms a pipeline. The output of each command in a pipeline
is connected to the input of the next.
Simple commands and pipelines may be joined into sequences with `;',
and will be executed sequentially. Commands and pipelines can also be
joined into sequences with `||' or `&&', indicating, as in the C lan-
guage, that the second is to be executed only if the first fails or
succeeds respectively.
A simple command, pipeline or sequence may be placed in parentheses,
`()', to form a simple command, which may in turn be a component of a
pipeline or sequence. A command, pipeline or sequence can be executed
without waiting for it to terminate by following it with an `&'.
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 containing
shell commands and a new shell is spawned to read it. The shell spe-
cial alias may be set to specify an interpreter other than the shell
itself.
On systems which do not understand the `#!' script interpreter conven-
tion 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 variable, filename or command substi-
tution, and each input line is compared to word before any sub-
stitutions are done on this input line. Unless a quoting `\',
`"', `' or ``' appears in word variable and command substitu-
tion 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 stan-
dard 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 special 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, commands run from a
file of shell commands have no access to the text of the commands by
default; rather they receive the original standard input of the shell.
The `<<' mechanism should be used to present inline data. This permits
shell command scripts to function as components of pipelines and allows
the shell to block read its input. Note that the default standard
input for a command run detached is not the empty file /dev/null, but
the original standard input of the shell. If this is a terminal and if
the process attempts to read from the terminal, then the process will
block and the user will be notified (see Jobs).
Diagnostic output may be directed through a pipe with the standard out-
put. 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 operate by
forcing the shell to reread or skip in its input and, due to the imple-
mentation, 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 when-
ever 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 `!~' oper-
ators compare their arguments as strings; all others operate on num-
bers. The operators `=~' and `!~' are like `!=' and `==' except that
the right hand side is a glob-pattern (see Filename substitution)
against which the left hand operand is matched. This reduces the need
for use of the switch builtin command in shell scripts when all that is
really needed is pattern matching.
Strings which begin with `0' are considered octal numbers. Null or
missing arguments are considered `0'. The results of all expressions
are strings, which represent decimal numbers. It is important to note
that no two components of an expression can appear in the same word;
except when adjacent to components of expressions which are syntacti-
cally 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. Command executions
succeed, returning true, i.e., `1', if the command exits with status 0,
otherwise they fail, returning false, i.e., `0'. If more detailed sta-
tus information is required then the command should be executed outside
of an expression and the status shell variable examined.
File inquiry operators
Some of these operators perform true/false tests on files and related
objects. They are of the form -op file, where op is one of
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 speci-
fied 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 equiva-
lent to `-x file && -y file'. (+) For example, `-fx' is true (returns
`1') for plain executable files, but not for directories.
L may be used in a multiple-operator test to apply subsequent operators
to a symbolic link rather than to the file to which the link points.
For example, `-lLo' is true for links owned by the invoking user. Lr,
Lw and Lx are always true for links and false for non-links. L has a
different meaning when it is the last operator in a multiple-operator
test; see below.
It is possible but not useful, and sometimes misleading, to combine
operators which expect file to be a file with operators which do not,
(e.g., X and t). Following L with a non-file operator can lead to par-
ticularly 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 inte-
ger 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 `Sus-
pended' and print another prompt. If the listjobs shell variable is
set, all jobs will be listed like the jobs builtin command; if it is
set to `long' the listing will be in long format, like `jobs -l'. You
can then manipulate the state of the suspended job. You can put it in
the ``background'' with the bg command or run some other commands and
eventually bring the job back into the ``foreground'' with fg. (See
also the run-fg-editor editor command.) A `^Z' takes effect 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 pro-
duce output like they do when they try to read input.
There are several ways to refer to jobs in the shell. The character
`%' introduces a job name. If you wish to refer to job number 1, you
can name it as `%1'. Just naming a job brings it to the foreground;
thus `%1' is a synonym for `fg %1', bringing job 1 back into the fore-
ground. Similarly, saying `%1 &' resumes job 1 in the background, just
like `bg %1'. A job can also be named by an unambiguous 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 out-
put pertaining to jobs, the current job is marked with a `+' and the
previous job with a `-'. The abbreviations `%+', `%', and (by analogy
with the syntax of the history mechanism) `%%' all refer to the current
job, and `%-' refers to the previous job.
The job control mechanism requires that the stty(1) option `new' be set
on some systems. It is an artifact from a `new' implementation of the
tty driver which allows generation of interrupt characters from the
keyboard to tell jobs to stop. See stty(1) and the setty builtin com-
mand for details on setting options in the new tty driver.
Status reporting
The shell learns immediately whenever a process changes state. It nor-
mally 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 immedi-
ately of changes of status in background jobs. There is also a shell
command notify which marks a single process so that its status changes
will be immediately reported. By default notify marks the current
process; simply say `notify' after starting a background job to mark
it.
When you try to leave the shell while jobs are stopped, you will be
warned that `You have stopped jobs.' You may use the jobs command to
see what they are. If you do this or immediately try to exit again,
the shell will not warn you a second time, and the suspended jobs will
be terminated.
Automatic, periodic and timed events (+)
There are various ways to run commands and take other actions automati-
cally 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 tpe-
riod minutes, before each prompt, before each command gets executed,
after each command gets executed, 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 character sets needing this capability.
NLS support differs depending on whether or not the shell was compiled
to use the system's NLS (again, see version). In either case, 7-bit
ASCII is the default for character classification (e.g., which charac-
ters 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 classification and sorting. This func-
tion typically examines the LANG and LC_CTYPE environment variables;
refer to the system documentation for further details. When not using
the system's NLS, the shell simulates it by assuming that the ISO
8859-1 character set is used whenever either of the LANG and LC_CTYPE
variables are set, regardless of their values. Sorting is not affected
for the simulated NLS.
In addition, with both real and simulated NLS, all printable characters
in the range \200-\377, i.e., those that have M-char bindings, are
automatically rebound to self-insert-command. The corresponding bind-
ing for the escape-char sequence, if any, is left alone. These charac-
ters are not rebound if the NOREBIND environment variable is set. This
may be useful for the simulated NLS or a primitive real NLS which
assumes full ISO 8859-1. Otherwise, all M-char bindings in the range
\240-\377 are effectively undone. Explicitly rebinding the relevant
keys with bindkey is of course still possible.
Unknown characters (i.e., those that are neither printable nor control
characters) are printed in the format \nnn. If the tty is not in 8 bit
mode, other 8 bit characters are printed by converting them to ASCII
and using standout mode. The shell never changes the 7/8 bit mode of
the tty and tracks user-initiated changes of 7/8 bit mode. NLS users
(or, for that matter, those who want to use a meta key) may need to
explicitly set the tty in 8 bit mode through the appropriate stty(1)
command in, e.g., the ~/.login file.
OS variant support (+)
A number of new builtin commands are provided to support features in
particular operating systems. All are described in detail in the
Builtin commands section.
On systems that support TCF (aix-ibm370, aix-ps2), getspath and
setspath get and set the system execution path, getxvers and setxvers
get and set the experimental version prefix and migrate migrates pro-
cesses 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 environ-
ment, rootnode changes the rootnode and ver changes the systype.
Under Mach, setpath is equivalent to Mach's setpath(1).
Under Masscomp/RTU and Harris CX/UX, universe sets the universe.
Under Harris CX/UX, ucb or att runs a command under the specified uni-
verse.
Under Convex/OS, warp prints or sets the universe.
The VENDOR, OSTYPE and MACHTYPE environment variables indicate respec-
tively 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 direc-
tory between several types of machines; one can, for example,
set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .)
in one's ~/.login and put executables compiled for each machine in the
appropriate directory.
The version shell variable indicates what options were chosen when the
shell was compiled.
Note also the newgrp builtin, the afsuser and echo_style shell vari-
ables 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 behav-
ior 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 sig-
nals 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 charac-
ters, and `execute', used when executing commands. The shell holds
some settings in each mode constant, so commands which leave the tty in
a confused state do not interfere with the shell. The shell also
matches changes in the speed and padding of the tty. The list of tty
modes that are kept constant can be examined and modified with the
setty builtin. Note that although the editor uses CBREAK mode (or its
equivalent), it takes typed-ahead characters anyway.
The echotc, settc and telltc commands can be used to manipulate and
debug terminal capabilities from the command line.
On systems that support SIGWINCH or SIGWINDOW, the shell adapts to win-
dow resizing automatically and adjusts the environment variables LINES
and COLUMNS if set. If the environment variable TERMCAP contains li#
and co# fields, the shell adjusts them to reflect the new window size.
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 component.
The space between `@' and name is required. The spaces between
name and `=' and between `=' and expr are optional. Components
of expr must be separated by spaces.
alias [name [wordlist]]
Without arguments, prints all aliases. With name, prints the
alias for name. With name and wordlist, assigns wordlist as
the alias of name. wordlist is command and filename 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, continuing each if it is stopped.
job may be a number, a string, `', `%', `+' or `-' as described
under Jobs.
bindkey [-l|-d|-e|-v|-u] (+)
bindkey [-a] [-b] [-k] [-r] [--] key (+)
bindkey [-a] [-b] [-k] [-c|-s] [--] key command (+)
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 ^charac-
ter (e.g., `^A') or C-character (e.g., `C-A'), a meta char-
acter 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 com-
pletely.
-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 termi-
nal 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 com-
mand.
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 Sys-
tem 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 num-
ber 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-PROCE-
DURE. (BS2000 only)
break Causes execution to resume after the end of the nearest enclos-
ing 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
substitutions). (+) If name is not a subdirectory of the cur-
rent 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 File-
name 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 cur-
rent 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 vari-
ables, which must include the current word.
list, the list of possible completions, may be one of the fol-
lowing:
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 pre-
fix
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 sup-
plied 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 character is appended. If omitted (in
which case the fourth delimiter can also be omitted), a slash
is appended to directories and a space to other words.
Now for some examples. Some commands take only directories as
arguments, so there's no point completing plain files.
> 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 argu-
ments, so the braces, space and `$' in `{print $1}' must be
quoted explicitly.
One command can have multiple completions:
> complete dbx 'p/2/(core)/' 'p/*/c/'
completes the second argument to `dbx' with the word `core' and
all other arguments with commands. Note that the positional
completion is specified before the next-word completion.
Because completions are evaluated from left to right, if the
next-word completion were specified first it would always match
and the positional completion would never be executed. This is
a common mistake when defining a completion.
The select pattern is useful when a command takes files with
only particular forms as arguments. For example,
> complete cc 'p/*/f:*.[cao]/'
completes `cc' arguments to files ending in only `.c', `.a', or
`.o'. select can also exclude files, using negation of a glob-
pattern as described under Filename substitution. One might
use
> complete rm 'p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/'
to exclude precious source code from `rm' completion. Of
course, one could still type excluded names manually or over-
ride the completion mechanism using the complete-word-raw or
list-choices-raw editor commands (q.v.).
The `C', `D', `F' and `T' lists are like `c', `d', `f' and `t'
respectively, but they use the select argument in a different
way: to restrict completion to files beginning with a particu-
lar path prefix. For example, the Elm mail program uses `=' as
an abbreviation for one's mail directory. One might use
> complete elm c@=@F:$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 follow-
ing `-fstype' or `-type' to members of the given lists. It
also completes the switches themselves from the given list
(note the use of c-type completion) and completes anything not
otherwise completed to a directory. Whew.
Remember that programmed completions are ignored if the word
being completed is a tilde substitution (beginning with `~') or
a variable (beginning with `$'). complete is an experimental
feature, and the syntax may change in future versions of the
shell. See also the uncomplete builtin command.
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 filename is not given and ~/.cshdirs
is used if dirsfile is unset.
Note that login shells do the equivalent of `dirs -L' on
startup and, if savedirs is set, `dirs -S' before exiting.
Because only ~/.tcshrc is normally sourced before ~/.cshdirs,
dirsfile should be set in ~/.tcshrc rather than ~/.login.
The last form clears the directory stack.
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 posi-
tion, '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 cor-
rectly. One should use double quotes when setting a shell
variable to a terminal capability string, as in the following
example that places the date in the status line:
> set tosl="`echotc ts 0`"
> set frsl="`echotc fs`"
> echo -n "$tosl";date; echo -n "$frsl"
With -s, nonexistent capabilities return the empty string
rather than causing an error. With -v, messages are verbose.
else
end
endif
endsw See the description of the foreach, if, switch, and while
statements below.
eval arg ...
Treats the arguments as input to the shell and executes the
resulting command(s) in the context of the current shell. This
is usually used to execute commands generated as the result of
command or variable substitution, because parsing occurs before
these substitutions. See tset(1) for a sample use of eval.
exec command
Executes the specified command in place of the current shell.
exit [expr]
The shell exits either with the value of the specified expr (an
expression, as described under Expressions) or, without expr,
with the value of the status variable.
fg [%job ...]
Brings the specified jobs (or, without arguments, the current
job) into the foreground, continuing each if it is stopped.
job may be a number, a string, `', `%', `+' or `-' as described
under Jobs. See also the run-fg-editor editor command.
filetest -op file ... (+)
Applies op (which is a file inquiry operator as described under
File inquiry operators) to each file and returns the results as
a space-separated list.
foreach name (wordlist)
...
end Successively sets the variable name to each member of wordlist
and executes the sequence of commands between this command and
the matching end. (Both foreach and end must appear alone on
separate lines.) The builtin command continue may be used to
continue the loop prematurely and the builtin command break to
terminate it prematurely. When this command is read from the
terminal, the loop is read once prompting with `foreach? ' (or
prompt2) before any statements in the loop are executed. If
you make a mistake typing in a loop at the terminal you can rub
it out.
getspath (+)
Prints the system execution path. (TCF only)
getxvers (+)
Prints the experimental version prefix. (TCF only)
glob wordlist
Like echo, but no `\' escapes are recognized and words are
delimited by null characters in the output. Useful for pro-
grams which wish to use the shell to filename expand a list of
words.
goto word
word is filename and command-substituted to yield a string of
the form `label'. The shell rewinds its input as much as pos-
sible, searches for a line of the form `label:', possibly pre-
ceded by blanks or tabs, and continues execution after that
line.
hashstat
Prints a statistics line indicating how effective the internal
hash table has been at locating commands (and avoiding exec's).
An exec is attempted for each component of the path where the
hash function indicates a possible hit, and in each component
which does not begin with a `/'.
On machines without vfork(2), prints only the number and size
of hash buckets.
history [-hTr] [n]
history -S|-L|-M [filename] (+)
history -c (+)
The first form prints the history event list. If n is given
only the n most recent events are printed or saved. With -h,
the history list is printed without leading numbers. If -T is
specified, timestamps are printed also in comment form. (This
can be used to produce files suitable for loading with 'history
-L' or 'source -h'.) With -r, the order of printing is most
recent first rather than oldest first.
With -S, the second form saves the history list to filename.
If the first word of the savehist shell variable is set to a
number, at most that many lines are saved. If the second word
of savehist is set to `merge', the history list is merged with
the existing history file instead of replacing it (if there is
one) and sorted by time stamp. (+) Merging is intended for an
environment like the X Window System with several shells in
simultaneous use. Currently it succeeds only when the shells
quit nicely one after another.
With -L, the shell appends filename, which is presumably a his-
tory list saved by the -S option or the savehist mechanism, to
the history list. -M is like -L, but the contents of filename
are merged into the history list and sorted by timestamp. In
either case, histfile is used if filename is not given and
~/.history is used if histfile is unset. `history -L' is
exactly like 'source -h' except that it does not require a
filename.
Note that login shells do the equivalent of `history -L' on
startup and, if savehist is set, `history -S' before exiting.
Because only ~/.tcshrc is normally sourced before ~/.history,
histfile should be set in ~/.tcshrc rather than ~/.login.
If histlit is set, the first and second forms print and save
the literal (unexpanded) form of the history list.
The last form clears the history list.
hup [command] (+)
With command, runs command such that it will exit on a hangup
signal and arranges for the shell to send it a hangup signal
when the shell exits. Note that commands may set their own
response to hangups, overriding hup. Without an argument
(allowed in only a shell script), causes the shell to exit on a
hangup for the remainder of the script. See also Signal han-
dling and the nohup builtin command.
if (expr) command
If expr (an expression, as described under Expressions) evalu-
ates true, then command is executed. Variable substitution on
command happens early, at the same time it does for the rest of
the if command. command must be a simple command, not an
alias, a pipeline, a command list or a parenthesized command
list, but it may have arguments. Input/output redirection
occurs even if expr is false and command is thus not executed;
this is a bug.
if (expr) then
...
else if (expr2) then
...
else
...
endif If the specified expr is true then the commands to the first
else are executed; otherwise if expr2 is true then the commands
to the second else are executed, etc. Any number of else-if
pairs are possible; only one endif is needed. The else part is
likewise optional. (The words else and endif must appear at
the beginning of input lines; the if must appear alone on its
input line or after an else.)
inlib shared-library ... (+)
Adds each shared-library to the current environment. There is
no way to remove a shared library. (Domain/OS only)
jobs [-l]
Lists the active jobs. With -l, lists process IDs in addition
to the normal information. On TCF systems, prints the site on
which each job is executing.
kill [-s signal] %job|pid ...
kill -l The first and second forms sends the specified signal (or, if
none is given, the TERM (terminate) signal) to the specified
jobs or processes. job may be a number, a string, `', `%', `+'
or `-' as described under Jobs. Signals are either given by
number or by name (as given in /usr/include/signal.h, stripped
of the prefix `SIG'). There is no default job; saying just
`kill' does not send a signal to the current job. If the sig-
nal bein