Computer Science
TCSH(1) TCSH(1)
NAME
tcsh - C shell with file name completion and command line
editing
SYNOPSIS
tcsh [-bcdefFimnqstvVxX] [-Dname[=value]] [arg ...]
tcsh -l
DESCRIPTION
tcsh is an enhanced but completely compatible version of
the Berkeley UNIX C shell, csh(1). It is a command lan-
guage 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 correction (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 spec-
ified by invoking the shell with the -l flag as the only
argument.
The rest of the flag arguments are interpreted as follows:
-b Forces a ``break'' from option processing, causing any
further shell arguments to be treated as non-option
arguments. The remaining arguments will not be inter-
preted as shell options. This may be used to pass
options to a shell script without confusion or possi-
ble subterfuge. The shell will not run a set-user ID
script without this option.
-c Commands are read from the following argument (which
must be present, and must be a single argument),
stored in the command shell variable for reference,
and executed. Any remaining arguments are placed in
the argv shell variable.
-d The shell loads the directory stack from ~/.cshdirs as
described under Startup and shutdown, whether or not
it is a login shell. (+)
-Dname[=value]
Sets the environment variable name to value.
(Domain/OS only) (+)
-e The shell exits if any invoked command terminates
abnormally or yields a non-zero exit status.
-f The shell 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. Only applicable if -l is
the only flag specified.
-m The shell loads ~/.tcshrc even if it does not belong
to the effective user. Newer versions of su(1) can
pass -m to the shell. (+)
-n The shell parses commands but does not execute them.
This aids in debugging shell scripts.
-q The shell accepts SIGQUIT (see Signal handling) and
behaves when it is used under a debugger. Job control
is disabled. (u)
-s Command input is taken from the standard input.
-t The shell reads and executes a single line of input.
A `\' may be used to escape the newline at the end of
this line and continue onto another line.
-v Sets the verbose shell variable, so that command input
is echoed after history substitution.
-x Sets the echo shell variable, so that commands are
echoed immediately before execution.
-V Sets the verbose shell variable even before executing
~/.tcshrc.
-X Is to -x as -V is to -v.
After processing of flag arguments, if arguments remain
but none of the -c, -i, -s, or -t options were given, the
first argument is taken as the name of a file of commands,
or ``script'', to be executed. The shell opens this file
and saves its name for possible resubstitution by `$0'.
Since many systems use either the standard version 6 or
version 7 shells whose shell scripts are not compatible
with this shell, the shell uses such a `standard' shell to
execute a script whose first character is not a `#', i.e.
which does not start with a comment.
Remaining arguments are placed in the argv shell variable.
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 vari-
able), 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 vari-
able. (+)
Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or
~/.cshrc on startup.
Commands like stty(1) and tset(1), which need be run only
once per login, usually go in one's ~/.login file. Users
who need to use the same set of files with both csh(1) and
tcsh can have only a ~/.cshrc which checks for the exis-
tence of the tcsh shell variable (q.v.) before using tcsh-
specific commands, or can have both a ~/.cshrc and a
~/.tcshrc which sources (see the builtin command)
~/.cshrc. The rest of this manual uses `~/.tcshrc' to
mean `~/.tcshrc or, if ~/.tcshrc is not found, ~/.cshrc'.
In the normal case, the shell begins reading commands from
the terminal, prompting with `> '. (Processing of argu-
ments and the use of the shell to process files containing
command scripts are described later.) The shell repeat-
edly reads a line of command input, breaks it into words,
places it on the command history list, parses it and exe-
cutes each command in the line.
One can log out by typing `^D' on an empty line, `logout'
or `login' or via the shell's autologout mechanism (see
the autologout shell variable). When a login shell termi-
nates it sets the logout shell variable to `normal' or
`automatic' as appropriate, then executes commands from
the files /etc/csh.logout and ~/.logout. The shell may
drop DTR on logout if so compiled; see the version shell
variable.
The names of the system login and logout files vary from
system to system for compatibility with different csh(1)
variants; see FILES.
Editing
We first describe The command-line editor. The Completion
and listing and Spelling correction sections describe two
sets of functionality which are implemented as editor com-
mands 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 com-
piled otherwise; see the version shell variable), but
bindkey can change the key bindings to vi-style bindings
en masse.
The shell always binds the arrow keys (as defined in the
TERMCAP environment variable) to
down down-history
up up-history
left backward-char
right forward-char
unless doing so would alter another single-character bind-
ing. 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 descrip-
tion of each.
Note that editor commands do not have the same notion of a
``word'' as does the shell. The editor delimits words with
any non-alphanumeric characters not in the shell variable
wordchars, while the shell recognizes only whitespace and
some of the characters with special meanings to it, listed
under Lexical structure.
Completion and listing (+)
The shell is often able to complete words when given a
unique abbreviation. Type part of a word (for example `ls
/usr/lost') and hit the tab key to run the complete-word
editor command. The shell completes the filename
`/usr/lost' to `/usr/lost+found/', replacing the incom-
plete 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
variable can be unset to prevent this.) If no match is
found (perhaps `/usr/lost+found' doesn't exist), the ter-
minal bell rings. If the word is already complete (per-
haps 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 just at the
end; completed text pushes the rest of the line to the
right. Completion in the middle of a word often results in
leftover characters to the right of the cursor which need
to be deleted.
Commands and variables can be completed in much the same
way. For example, typing `em[tab]' would complete `em' to
`emacs' if emacs were the only command on your system
beginning with `em'. Completion can find a command in any
directory in path or if given a full pathname. Typing
`echo $ar[tab]' would complete `$ar' to `$argv' if no
other variable began with `ar'.
The shell parses the input buffer to determine whether the
word you want to complete should be completed as a file-
name, command or variable. The first word in the buffer
and the first word following `;', `|', `|&', `&&' or `||'
is considered to be a command. A word beginning with `$'
is considered to be a variable. Anything else is a 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 reprints the prompt and
unfinished command line, for example:
> ls /usr/l[^D]
lbin/ lib/ local/ lost+found/
> ls /usr/l
If the autolist shell variable is set, the shell lists the
remaining choices (if any) whenever completion fails:
> set autolist
> nm /usr/lib/libt[tab]
libtermcap.a@ libtermlib.a@
> nm /usr/lib/libterm
If autolist is set to `ambiguous', choices are listed only
when completion fails and adds no new characters to the
word being completed.
A filename to be completed can contain variables, your own
or others' home directories abbreviated with `~' (see
Filename substitution) and directory stack entries abbre-
viated with `=' (see Directory stack substitution). For
example,
> ls ~k[^D]
kahn kas kellogg
> ls ~ke[tab]
> ls ~kellogg/
or
> set local = /usr/local
> ls $lo[tab]
> ls $local/[^D]
bin/ etc/ lib/ man/ src/
> ls $local/
Note that variables can also be expanded explicitly with
the expand-variables editor command.
delete-char-or-list-or-eof only lists at the end of the
line; in the middle of a line it deletes the character
under the cursor and on an empty line it logs one out or,
if ignoreeof is set, does nothing. `M-^D', bound to the
editor command list-choices, lists completion possibili-
ties anywhere on a line, and list-choices (or any one of
the related editor commands which do or don't delete, list
and/or log out, listed under delete-char-or-list-or-eof)
can be bound to `^D' with the bindkey builtin command if
so desired.
The complete-word-fwd and complete-word-back editor com-
mands (not bound to any keys by default) can be used to
cycle up and down through the list of possible comple-
tions, replacing the current word with the next or previ-
ous word in the list.
The shell variable fignore can be set to a list of suf-
fixes 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 substi-
tution. fignore is ignored if only one completion is pos-
sible.
If the complete shell variable is set to `enhance', com-
pletion 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-correct the
word to be completed (see Spelling correction) before each
completion attempt and correct can be set to complete com-
mands automatically after one hits `return'. matchbeep
can be set to make completion beep or not beep in a vari-
ety of situations, and nobeep can be set to never beep at
all. nostat can be set to a list of directories and/or
patterns which match directories to prevent the completion
mechanism from stat(2)ing those directories. listmax and
listmaxrows can be set to limit the number of items and
rows (respectively) that are listed without asking first.
recognize_only_executables can be set to make the shell
list only executables when listing commands, but it is
quite slow.
Finally, the complete builtin command can be used to tell
the shell how to complete words other than filenames, com-
mands and variables. Completion and listing do not work
on glob-patterns (see Filename substitution), but the
list-glob and expand-glob editor commands perform equiva-
lent 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 any-
thing else to execute the original line unchanged.
Spelling correction recognizes user-defined completions
(see the complete builtin command). If an input word in a
position for which a completion is defined resembles a
word in the completion list, spelling correction registers
a misspelling and suggests the latter word as a correc-
tion. However, if the input word does not match any of the
possible completions for that position, spelling correc-
tion does not register a misspelling.
Like completion, spelling correction works anywhere in the
line, pushing the rest of the line to the right and possi-
bly leaving extra characters to the right of the cursor.
Beware: spelling correction is not guaranteed to work the
way one intends, and is provided mostly as an experimental
feature. Suggestions and improvements are welcome.
Editor commands (+)
`bindkey' lists key bindings and `bindkey -l' lists and
briefly describes editor commands. Only new or especially
interesting editor commands are described here. See
emacs(1) and vi(1) for 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 which are bound to letters by
default are bound to both lower- and uppercase letters for
convenience.
complete-word (tab)
Completes a word as described under Completion and
listing.
complete-word-back (not bound)
Like complete-word-fwd, but steps up from the end
of the list.
complete-word-fwd (not bound)
Replaces the current word with the first word in
the list of possible completions. May be repeated
to step down through the list. At the end of the
list, beeps and reverts to the incomplete word.
complete-word-raw (^X-tab)
Like complete-word, but ignores user-defined com-
pletions.
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 pre-
ceding one for which the current is a leading sub-
string, 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 only does a single
action, and delete-char-or-eof, delete-char-or-
list and list-or-eof, each of which does a differ-
ent 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 cur-
sor. See Filename substitution.
expand-line (not bound)
Like expand-history, but expands history substitu-
tions 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) contain-
ing `*', `?', `[]' or `{}'. up-history and down-
history will proceed from the appropriate point in
the history list. Emacs mode only. See also his-
tory-search-forward and i-search-back.
history-search-forward (M-n, M-N)
Like history-search-backward, but searches for-
ward.
i-search-back (not bound)
Searches backward like history-search-backward,
copies the first match into the input buffer with
the cursor positioned at the end of the pattern,
and prompts with `bck: ' and the first match.
Additional characters may be typed to extend the
search, i-search-back may be typed to continue
searching with the same pattern, wrapping around
the history list if necessary, (i-search-back must
be bound to a single character for this to work)
or one of the following special characters may be
typed:
^W Appends the rest of the word under the
cursor to the search pattern.
delete (or any character bound to backward-
delete-char)
Undoes the effect of the last charac-
ter typed and deletes a character from
the search pattern if appropriate.
^G If the previous search was successful,
aborts the entire search. If not,
goes back to the last successful
search.
escape Ends the search, leaving the current
line in the input buffer.
Any other character not bound to self-insert-com-
mand 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 com-
pletions.
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 appends a space. magic-
space is designed to be bound to the spacebar, 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 com-
mands which take commands as arguments, e.g. `dbx'
and `sh -x'.
normalize-path (^X-n, ^X-N)
Expands the current word as described under the
`expand' setting of the symlinks shell variable.
overwrite-mode (unbound)
Toggles between input and overwrite modes.
run-fg-editor (M-^Z)
Saves the current input line and looks for a
stopped job with a name equal to the last compo-
nent of the file name part of the EDITOR or VISUAL
environment variables, or, if neither is set, `ed'
or `vi'. If such a job is found, it is restarted
as if `fg %job' had been typed. This is used to
toggle back and forth between an editor and the
shell easily. Some people bind this command to
`^Z' so they can do this even more easily.
run-help (M-h, M-H)
Searches for documentation on the current command,
using the same notion of `current command' as the
completion routines, and prints it. There is no
way to use a pager; run-help is designed for short
help files. Documentation should be in a file
named command.help, command.1, command.6, com-
mand.8 or command, which should be in one of the
directories listed in the HPATH enviroment vari-
able. If there is more than one help file only
the first is printed.
self-insert-command (text characters)
In insert mode (the default), inserts the typed
character into the input line after the character
under the cursor. In overwrite mode, replaces the
character under the cursor with the typed charac-
ter. The input mode is normally preserved between
lines, but the inputmode shell variable can be set
to `insert' or `overwrite' to put the editor in
that mode at the beginning of each line. See also
overwrite-mode.
sequence-lead-in (arrow prefix, meta prefix, ^X)
Indicates that the following characters are part
of a multi-key sequence. Binding a command to a
multi-key sequence really creates two bindings:
the first character to sequence-lead-in and the
whole sequence to the command. All sequences
beginning with a character bound to sequence-lead-
in are effectively bound to undefined-key unless
bound to another command.
spell-line (M-$)
Attempts to correct the spelling of each word in
the input buffer, like spell-word, but ignores
words whose first character is one of `-', `!',
`^' or `%', or which contain `\', `*' or `?', to
avoid problems with switches, substitutions and
the like. See Spelling correction.
spell-word (M-s, M-S)
Attempts to correct the spelling of the current
word as described under Spelling correction.
Checks each component of a word which appears to
be a pathname.
toggle-literal-history (M-r, M-R)
Expands or `unexpands' history substitutions in
the input buffer. See also expand-history and the
autoexpand shell variable.
undefined-key (any unbound key)
Beeps.
up-history (up-arrow, ^P)
Copies the previous entry in the history list into
the input buffer. If histlit is set, uses the
literal form of the entry. May be repeated to
step up through the history list, stopping at the
top.
vi-search-back (?)
Prompts with `?' for a search string (which may be
a glob-pattern, as with history-search-backward),
searches for it and copies it into the input
buffer. The bell rings if no match is found. Hit-
ting 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.
Lexical structure
The shell splits input lines into words at blanks and
tabs. The special characters `&', `|', `;', `<', `>',
`(', and `)' and the doubled characters `&&', `||', `<<'
and `>>' are always separate words, whether or not they
are surrounded by whitespace.
When the shell's input is not a terminal, the character
`#' is taken to begin a comment. Each `#' and the rest of
the input line on which it appears is discarded before
further parsing.
A special character (including a blank or tab) may be pre-
vented from having its special meaning, and possibly made
part of another word, by preceding it with a backslash
(`\') or enclosing it in single (`''), double (`"') or
backward (``') quotes. When not otherwise quoted a newline
preceded by a `\' is equivalent to a blank, but inside
quotes this sequence results in a newline.
Furthermore, all Substitutions (see below) except History
substitution can be prevented by enclosing the strings (or
parts of strings) in which they appear with single quotes
or by quoting the crucial character(s) (e.g. `$' or ``'
for Variable substitution or Command substitution respec-
tively) 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 back-
slashes but not by single quotes. Strings quoted with
double or backward quotes undergo Variable substitution
and Command substitution, but other substitutions are pre-
vented.
Text inside single or double quotes becomes a single word
(or part of one). Metacharacters in these strings,
including blanks and tabs, do not form separate words.
Only in one special case (see Command substitution below)
can a double-quoted string yield parts of more than one
word; single-quoted strings never do. Backward quotes are
special: they signal Command substitution (q.v.), which
may result in more than one word.
Quoting complex strings, particularly strings which them-
selves contain quoting characters, can be confusing.
Remember that quotes need not be used as they are in human
writing! It may be easier to quote not an entire string,
but only those parts of the string which need quoting,
using different types of quoting to do so if appropriate.
The backslash_quote shell variable (q.v.) can be set to
make backslashes always quote `\', `'', and `"'. (+) This
may make complex quoting tasks easier, but it can cause
syntax errors in csh(1) scripts.
Substitutions
We now describe the various transformations the shell per-
forms on the input in the order in which they occur. We
note in passing the data structures involved and the com-
mands and variables which affect them. Remember that sub-
stitutions 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 num-
ber to save that many commands. The histdup shell variable
can be set to not save duplicate events or consecutive
duplicate events.
Saved commands are numbered sequentially from 1 and
stamped with the time. It is not usually necessary to use
event numbers, but the current event number can be made
part of the prompt by placing an `!' in the prompt shell
variable.
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 com-
mands, repeat arguments of a previous command in the cur-
rent 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 set-
ting 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 specifica-
tion'', which indicates the event from which words are to
be taken, a ``word designator'', which selects particular
words from the chosen event, and/or a ``modifier'', which
manipulates the selected words.
An event specification can be
n A number, referring to a particular event
-n An offset, referring to the event n before the
current event
# The current event. This should be used care-
fully 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 unam-
biguously to `vi wumpus.mandoc'. Even in braces, history
substitutions do not nest.
(+) While csh(1) expands, for example, `!3d' to event 3
with the letter `d' appended to it, tcsh expands it to the
last event beginning with `3d'; only completely numeric
arguments are treated as event numbers. This makes it
possible to recall events beginning with numbers. To
expand `!3d' as in csh(1) say `!\3d'.
To select words from an event we can follow the event
specification by a `:' and a designator for the desired
words. The words of an input line are numbered from 0,
the first (usually command) word being 0, the second word
(first argument) being 1, etc. The basic word designators
are:
0 The first (command) word
n The nth argument
^ The first argument, equivalent to `1'
$ The last argument
% The word matched by an ?s? search
x-y A range of words
-y Equivalent to `0-y'
* Equivalent to `^-$', but returns nothing if
the event contains only 1 word
x* Equivalent to `x-$'
x- Equivalent to `x*', but omitting the last word
(`$')
Selected words are inserted into the command line sepa-
rated by single blanks. For example, the `diff' command
in the previous example might have been typed as `diff
!!:1.old !!:1' (using `:1' to select the first argument
from the previous event) or `diff !-2:2 !-2:1' to select
and swap the arguments from the `cp' command. If we didn't
care about the order of the `diff' we might have said
`diff !-2:1-2' or simply `diff !-2:*'. The `cp' command
might have been written `cp wumpus.man !#:1.old', using
`#' to refer to the current event. `!n:- hurkle.man'
would reuse the first two words from the `nroff' command
to say `nroff -man hurkle.man'.
The `:' separating the event specification from the word
designator can be omitted if the argument selector begins
with a `^', `$', `*', `%' or `-'. For example, our `diff'
command might have been `diff !!^.old !!^' or, equiva-
lently, `diff !!$.old !!$'. However, if `!!' is abbrevi-
ated `!', an argument selector beginning with `-' will be
interpreted as an event specification.
A history reference may have a word designator but no
event specification. It then references the previous com-
mand. Continuing our `diff' example, we could have said
simply `diff !^.old !^' or, to get the arguments in the
opposite order, just `diff !*'.
The word or words in a history reference can be edited, or
``modified'', by following it with one or more modifiers,
each preceded by a `:':
h Remove a trailing pathname component, leaving
the head.
t Remove all leading pathname components, leav-
ing 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 epony-
mous ed(1) command. Any character may be used
as the delimiter in place of `/'; a `\' can be
used to quote the delimiter inside l and r.
The character `&' in the r is replaced by l;
`\' also quotes `&'. If l is empty (``''),
the l from a previous substitution or the s
from a previous `?s?' event specification is
used. The trailing delimiter may be omitted
if it is immediately followed by a newline.
& Repeat the previous substitution.
g Apply the following modifier once to each
word.
a (+) Apply the following modifier as many times as
possible to a single word. `a' and `g' can be
used together to apply a modifier globally.
In the current implementation, using the `a'
and `s' modifiers together can lead to an
infinite loop. For example, `:as/f/ff/' will
never terminate. This behavior might change
in the future.
p Print the new command line but do not execute
it.
q Quote the substituted words, preventing fur-
ther substitutions.
x Like q, but break into words at blanks, tabs
and newlines.
Modifiers are applied only to the first modifiable word
(unless `g' is used). It is an error for no word to be
modifiable.
For example, the `diff' command might have been written as
`diff wumpus.man.old !#^:r', using `:r' to remove `.old'
from the first argument on the same line (`!#^'). We could
say `echo hello out there', then `echo !*:u' to capitalize
`hello', `echo !*:au' to say it out loud, or `echo !*:agu'
to really shout. We might follow `mail -s "I forgot my
password" rot' with `!:s/rot/root' to correct the spelling
of `root' (but see Spelling correction for a different
approach).
There is a special abbreviation for substitutions. `^',
when it is the first character on an input line, is equiv-
alent to `!:s^'. Thus we might have said `^rot^root' to
make the spelling correction in the previous example.
This is the only history substitution which does not
explicitly begin with `!'.
(+) In csh as such, only one modifier may be applied to
each history or variable expansion. In tcsh, more than one
may be used, for example
% mv wumpus.man /usr/man/man1/wumpus.1
% man !$:t:r
man wumpus
In csh, the result would be `wumpus.1:r'. A substitution
followed by a colon may need to be insulated from it with
braces:
> mv a.out /usr/games/wumpus
> setenv PATH !$: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 command, left-to-right,
is checked to see if it has an alias. If so, the first
word is replaced by the alias. If the alias contains a
history reference, it undergoes History substitution
(q.v.) as though the original command were the previous
input line. If the alias does not contain a history refer-
ence, 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 displayed and changed with the set
and unset commands. The system maintains its own list of
``environment'' variables. These can be displayed and
changed with printenv, setenv and unsetenv.
(+) Variables may be made read-only with `set -r' (q.v.)
Read-only variables may not be modified or unset; attempt-
ing to do so will cause an error. Once made read-only, a
variable cannot be made writable, so `set -r' should be
used with caution. Environment variables cannot be made
read-only.
Some variables are set by the shell or referred to by it.
For instance, the argv variable is an image of the shell's
argument list, and words of this variable's value are
referred to in special ways. Some of the variables
referred to by the shell are toggles; the shell does not
care what their value is, only whether they are set or
not. For instance, the verbose variable is a toggle which
causes command input to be echoed. The -v command line
option sets this variable. Special shell variables lists
all variables which are referred to by the shell.
Other operations treat variables numerically. The `@'
command permits numeric calculations to be performed and
the result assigned to a variable. Variable values are,
however, always represented as (zero or more) strings.
For the purposes of numeric operations, the null string is
considered to be zero, and the second and subsequent words
of multiword values are ignored.
After the input line is aliased and parsed, and before
each command is executed, variable substitution is per-
formed keyed by `$' characters. This expansion can be
prevented by preceding the `$' with a `\' except within
`"'s where it always occurs, and within `''s where it
never occurs. Strings quoted by ``' are interpreted later
(see Command substitution below) so `$' substitution does
not occur there until later, if at all. A `$' is passed
unchanged if followed by a blank, tab, or end-of-line.
Input/output redirections are recognized before variable
expansion, and are variable expanded separately. Other-
wise, the command name and entire argument list are
expanded together. It is thus possible for the first
(command) word (to this point) to generate more than one
word, the first of which becomes the command name, and the
rest of which become arguments.
Unless enclosed in `"' or given the `:q' modifier the
results of variable substitution may eventually be command
and filename substituted. Within `"', a variable whose
value consists of multiple words expands to a (portion of
a) single word, with the words of the variable's value
separated by blanks. When the `:q' modifier is applied to
a substitution the variable will expand to multiple words
with each word separated by a blank and quoted to prevent
later command or filename substitution.
The following metasequences are provided for introducing
variable values into the shell input. Except as noted, it
is an error to reference a variable which is not set.
$name
${name} Substitutes the words of the value of variable
name, each separated by a blank. Braces insulate
name from following characters which would other-
wise be part of it. Shell variables have names
consisting of up to 20 letters and digits starting
with a letter. The underscore character is con-
sidered a letter. If name is not a shell vari-
able, 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]
${name[selector]}
Substitutes only the selected words from the value
of name. The selector is subjected to `$' substi-
tution 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 com-
mand 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 modifiers
must appear within the braces.
The following substitutions can not be modified with `:'
modifiers.
$?name
${?name}
Substitutes the string `1' if name is set, `0' if
it is not.
$?0 Substitutes `1' if the current input filename is
known, `0' if it is not. Always `0' in interac-
tive 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[num-
ber]. (+)
$? Equivalent to `$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 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 sepa-
rate words at blanks, tabs and newlines, and null words
are discarded. The output is variable and command substi-
tuted and put in place of the original string.
Command substitutions inside double quotes (`"') retain
blanks and tabs; only newlines force new words. The sin-
gle final newline does not force a new word in any case.
It is thus possible for a command substitution to yield
only part of a word, even if the command outputs a com-
plete 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 charac-
ter `*' matches any string of characters, including the
null string. The character `?' matches any single charac-
ter. The sequence `[...]' matches any one of the charac-
ters enclosed. Within `[...]', a pair of characters sepa-
rated 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 pre-
serve this order: `../{memo,*box}' might expand to
`../memo ../box ../mbox'. (Note that `memo' was not
sorted with the results of matching `*box'.) It is not an
error when this construct expands to files which do not
exist, but it is possible to get an error from a command
to which the expanded list is passed. This construct may
be nested. As a special case the words `{', `}' and `{}'
are passed undisturbed.
The character `~' at the beginning of a filename refers to
home directories. Standing alone, i.e. `~', it expands to
the invoker's home directory as reflected in the value of
the home shell variable. When followed by a name consist-
ing of letters, digits and `-' characters the shell
searches for a user with that name and substitutes their
home directory; thus `~ken' might expand to `/usr/ken' and
`~ken/chmach' to `/usr/ken/chmach'. If the character `~'
is followed by a character other than a letter or `/' or
appears elsewhere than at the beginning of a word, it is
left undisturbed. A command like `setenv MANPATH
/usr/man:/usr/local/man:~/lib/man' does not, therefore, do
home directory substitution as one might hope.
It is an error for a glob-pattern containing `*', `?', `['
or `~', with or without `^', not to match any files. How-
ever, 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 end-
ing 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 indi-
vidual filename substitutions.
Directory stack substitution (+)
The directory stack is a list of directories, numbered
from zero, used by the pushd, popd and dirs builtin com-
mands (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 directo-
ries into the directory stack.
The character `=' followed by one or more digits expands
to an entry in the directory stack. The special case `=-'
expands to the last directory in the stack. For example,
> dirs -v
0 /usr/bin
1 /usr/spool/uucp
2 /usr/accts/sys
> echo =1
/usr/spool/uucp
> echo =0/calendar
/usr/bin/calendar
> echo =-
/usr/accts/sys
The noglob and nonomatch shell variables and the expand-
glob editor command apply to directory stack as well as
filename substitutions.
Other substitutions (+)
There are several more transformations involving file-
names, 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 nor-
malize-path editor command does it on demand. The normal-
ize-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 only by 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 language, that the second is
to be executed only if the first fails or succeeds respec-
tively.
A simple command, pipeline or sequence may be placed in
parentheses, `()', to form a simple command, which may in
turn be a component of a pipeline or sequence. A command,
pipeline or sequence can be executed without waiting for
it to terminate by following it with an `&'.
Builtin and non-builtin command execution
Builtin commands are executed within the shell. If any
component of a pipeline except the last is a builtin com-
mand, 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 cur-
rent 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 direc-
tory in which the shell will look for the command. If it
is given neither a -c nor a -t option, the shell hashes
the names in these directories into an internal table so
that it will only try an execve(2) in a directory if there
is a possibility that the command resides there. This
greatly speeds command location when a large number of
directories are present in the search path. If this mech-
anism has been turned off (via unhash), if the shell was
given a -c or -t argument or in any case for each direc-
tory 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 exe-
cutable to the system (i.e. it is neither an executable
binary nor a script which specifies its interpreter), then
it is assumed to be a file containing shell commands and a
new shell is spawned to read it. The shell special alias
may be set to specify an interpreter other than the shell
itself.
On systems which do not understand the `#!' script inter-
preter convention the shell may be compiled to emulate it;
see the version shell variable. If so, the shell checks
the first line of the file to see if it is of the form
`#!interpreter arg ...'. If it is, the shell starts inter-
preter 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 identi-
cal to word. word is not subjected to variable,
filename or command substitution, and each input
line is compared to word before any substitutions
are done on this input line. Unless a quoting
`\', `"', `' or ``' appears in word variable and
command substitution is performed on the interven-
ing lines, allowing `\' to quote `$', `\' and ``'.
Commands which are substituted have all blanks,
tabs, and newlines preserved, except for the final
newline which is dropped. The resultant text is
placed in an anonymous temporary file which is
given to the command as standard input.
> name
>! name
>& name
>&! name
The file name is used as standard output. If the
file does not exist then it is created; if the
file exists, its is truncated, its previous con-
tents 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 accidental destruc-
tion of files. In this case the `!' forms can be
used to suppress this check.
The forms involving `&' route the diagnostic out-
put into the specified file as well as the stan-
dard 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 com-
mands 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 pre-
sent inline data. This permits shell command scripts to
function as components of pipelines and allows the shell
to block read its input. Note that the default standard
input for a command run detached is not the empty file
/dev/null, but the original standard input of the shell.
If this is a terminal and if the process attempts to read
from the terminal, then the process will block and the
user will be notified (see Jobs).
Diagnostic output may be directed through a pipe with the
standard output. Simply use the form `|&' rather than
just `|'.
The shell cannot presently redirect diagnostic output
without also redirecting standard output, but `(command >
output-file) >& error-file' is often an acceptable
workaround. Either output-file or error-file may be
`/dev/tty' to send output to the terminal.
Features
Having described how the shell accepts, parses and exe-
cutes command lines, we now turn to a variety of its use-
ful 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 implementa-
tion, restrict the placement of some of the commands.
The foreach, switch, and while statements, as well as the
if-then-else form of the if statement, require that the
major keywords appear in a single simple command on an
input line as shown below.
If the shell's input is not seekable, the shell buffers up
input whenever a loop is being read and performs seeks in
this internal buffer to accomplish the rereading implied
by the loop. (To the extent that this allows, backward
gotos will succeed on non-seekable inputs.)
Expressions
The if, while and exit builtin commands use expressions
with a common syntax. The expressions can include any of
the operators described in the next three sections. Note
that the @ builtin command (q.v.) has its own separate
syntax.
Logical, arithmetical and comparison operators
These operators are similar to those of C and have the
same precedence. They include
|| && | ^ & == != =~ !~ <= >=
< > << >> + - * / % ! ~ ( )
Here the precedence increases to the right, `==' `!=' `=~'
and `!~', `<=' `>=' `<' and `>', `<<' and `>>', `+' and
`-', `*' `/' and `%' being, in groups, at the same level.
The `==' `!=' `=~' and `!~' operators compare their argu-
ments as strings; all others operate on numbers. The
operators `=~' and `!~' are like `!=' and `==' except that
the right hand side is a glob-pattern (see Filename sub-
stitution) against which the left hand operand is matched.
This reduces the need for use of the switch builtin com-
mand 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 (`{}'). Remem-
ber that the braces should be separated from the words of
the command by spaces. Command executions succeed, return-
ing true, i.e. `1', if the command exits with status 0,
otherwise they fail, returning false, i.e. `0'. If more
detailed status information is required then the command
should be executed outside of an expression and the status
shell variable examined.
File inquiry operators
Some of these operators perform true/false tests on files
and related objects. They are of the form -op file, where
op is one of
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-opera-
tor test to a symbolic link rather than to the
file to which the link points (+) *
file is command and filename expanded and then tested to
see if it has the specified relationship to the real user.
If file does not exist or is inaccessible or, for the
operators indicated by `*', if the specified file type
does not exist on the current system, then all enquiries
return false, i.e. `0'.
These operators may be combined for conciseness: `-xy
file' is equivalent to `-x file && -y file'. (+) For exam-
ple, `-fx' is true (returns `1') for plain executable
files, but not for directories.
L may be used in a multiple-operator test to apply subse-
quent 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 multi-
ple-operator test; see below.
It is possible but not useful, and sometimes misleading,
to combine operators which expect file to be a file with
operators which do not, (e.g. X and t). Following L with a
non-file operator can lead to particularly strange
results.
Other operators return other information, i.e. not just
`0' or `1'. (+) They have the same format as before; op
may be one of
A Last file access time, as the number of sec-
onds 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 user-
name 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-oper-
ator test, and it must be the last. Note that L has a dif-
ferent 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 ver-
sion shell variable), the result of a file inquiry is
based on the permission bits of the file and not on the
result of the access(2) system call. For example, if one
tests a file with -w whose permissions would ordinarily
allow writing but which is on a file system mounted read-
only, the test will succeed in a POSIX shell but fail in a
non-POSIX shell.
File inquiry operators can also be evaluated with the
filetest builtin command (q.v.) (+).
Jobs
The shell associates a job with each pipeline. It keeps a
table of current jobs, printed by the jobs command, and
assigns them small integer numbers. When a job is started
asynchronously with `&', the shell prints a line which
looks like
[1] 1234
indicating that the job which was started asynchronously
was job number 1 and had one (top-level) process, whose
process id was 1234.
If you are running a job and wish to do something else you
may hit the suspend key (usually `^Z'), which sends a STOP
signal to the current job. The shell will then normally
indicate that the job has been `Suspended' and print
another prompt. If the listjobs shell variable is set,
all jobs will be listed like the jobs builtin command; if
it is set to `long' the listing will be in long format,
like `jobs -l'. You can then manipulate the state of the
suspended job. You can put it in the ``background'' with
the bg command or run some other commands and eventually
bring the job back into the ``foreground'' with fg. (See
also the run-fg-editor editor command.) A `^Z' takes
effect immediately and is like an interrupt in that pend-
ing output and unread input are discarded when it is
typed. The wait builtin command causes the shell to wait
for all background jobs to complete.
The `^]' key sends a delayed suspend signal, which does
not generate a STOP signal until a program attempts to
read(2) it, to the current job. This can usefully be
typed ahead when you have prepared some commands for a job
which you wish to stop after it has read them. The `^Y'
key performs this function in csh(1); in tcsh, `^Y' is an
editing command. (+)
A job being run in the background stops if it tries to
read from the terminal. Background jobs are normally
allowed to produce output, but this can be disabled by
giving the command `stty tostop'. If you set this tty
option, then background jobs will stop when they try to
produce output like they do when they try to read input.
There are several ways to refer to jobs in the shell. The
character `%' introduces a job name. If you wish to refer
to job number 1, you can name it as `%1'. Just naming a
job brings it to the foreground; thus `%1' is a synonym
for `fg %1', bringing job 1 back into the foreground.
Similarly, saying `%1 &' resumes job 1 in the background,
just like `bg %1'. A job can also be named by an unam-
bigous prefix of the string typed in to start it: `%ex'
would normally restart a suspended ex(1) job, if there
were only one suspended job whose name began with the
string `ex'. It is also possible to say `%?string' to
specify a job whose text contains string, if there is only
one such job.
The shell maintains a notion of the current and previous
jobs. In output pertaining to jobs, the current job is
marked with a `+' and the previous job with a `-'. The
abbreviations `%+', `%', and (by analogy with the syntax
of the history mechanism) `%%' all refer to the current
job, and `%-' refers to the previous job.
The job control mechanism requires that the stty(1) option
`new' be set on some systems. It is an artifact from a
`new' implementation of the tty driver which allows gener-
ation of interrupt characters from the keyboard to tell
jobs to stop. See stty(1) and the setty builtin command
for details on setting options in the new tty driver.
Status reporting
The shell learns immediately whenever a process changes
state. It normally informs you whenever a job becomes
blocked so that no further progress is possible, but only
just before it prints a prompt. This is done so that it
does not otherwise disturb your work. If, however, you
set the shell variable notify, the shell will notify you
immediately of changes of status in background jobs.
There is also a shell command notify which marks a single
process so that its status changes will be immediately
reported. By default notify marks the current process;
simply say `notify' after starting a background job to
mark it.
When you try to leave the shell while jobs are stopped,
you will be warned that `You have stopped jobs.' You may
use the jobs command to see what they are. If you do this
or immediately try to exit again, the shell will not warn
you a second time, and the suspended jobs will be termi-
nated.
Automatic, periodic and timed events (+)
There are various ways to run commands and take other
actions automatically at various times in the ``life
cycle'' of the shell. They are summarized here, and
described in detail under the appropriate Builtin com-
mands, 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 and precmd Special aliases
can be set, respectively, to execute commands when the
shell wants to ring the bell, when the working directory
changes, every tperiod minutes and before each prompt.
The autologout shell variable can be set to log out or
lock the shell after a given number of minutes of inactiv-
ity.
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 ver-
sion 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 char-
acters are printable) and sorting, and changing the LANG
or LC_CTYPE environment variables causes a check for pos-
sible changes in these respects.
When using the system's NLS, the setlocale(3) function is
called to determine appropriate character classification
and sorting. This function typically examines the LANG
and LC_CTYPE environment variables; refer to the system
documentation for further details. When not using the
system's NLS, the shell simulates it by assuming that the
ISO 8859-1 character set is used whenever either of the
LANG and LC_CTYPE variables are set, regardless of their
values. Sorting is not affected for the simulated NLS.
In addition, with both real and simulated NLS, all print-
able characters in the range \200-\377, i.e. those that
have M-char bindings, are automatically rebound to self-
insert-command. The corresponding binding for the escape-
char sequence, if any, is left alone. These characters
are not rebound if the NOREBIND environment variable is
set. This may be useful for the simulated NLS or a primi-
tive 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 bind-
key is of course still possible.
Unknown characters (i.e. those that are neither printable
nor control characters) are printed in the format \nnn.
If the tty is not in 8 bit mode, other 8 bit characters
are printed by converting them to ASCII and using standout
mode. The shell never changes the 7/8 bit mode of the tty
and tracks user-initiated changes of 7/8 bit mode. NLS
users (or, for that matter, those who want to use a meta
key) may need to explicitly set the tty in 8 bit mode
through the appropriate stty(1) command in, e.g., the
~/.login file.
OS variant support (+)
A number of new builtin commands are provided to support
features in particular operating systems. All are
described in detail in the Builtin commands section.
On systems that support TCF (aix-ibm370, aix-ps2),
getspath and setspath get and set the system execution
path, getxvers and setxvers get and set the experimental
version prefix and migrate migrates processes between
sites. The jobs builtin prints the site on which each job
is executing.
Under Domain/OS, inlib adds shared libraries to the cur-
rent environment, rootnode changes the rootnode and ver
changes the systype.
Under Mach, setpath is equivalent to Mach's setpath(1).
Under Masscomp/RTU and Harris CX/UX, universe sets the
universe.
Under Harris CX/UX, ucb or att runs a command under the
specified universe.
Under Convex/OS, warp prints or sets the universe.
The VENDOR, OSTYPE and MACHTYPE environment variables
indicate respectively the vendor, operating system and
machine type (microprocessor class or machine model) of
the system on which the shell thinks it is running. These
are particularly useful when sharing one's home directory
between several types of machines; one can, for example,
set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .)
in one's ~/.login and put executables compiled for each
machine in the appropriate directory.
The version shell variable indicates what options were
chosen when the shell was compiled.
Note also the newgrp builtin, the afsuser and echo_style
shell variables and the system-dependent locations of the
shell's input files (see FILES).
Signal handling
Login shells ignore interrupts when reading the file
~/.logout. The shell ignores quit signals unless started
with -q. Login shells catch the terminate signal, but
non-login shells inherit the terminate behavior from their
parents. Other signals have the values which the shell
inherited from its parent.
In shell scripts, the shell's handling of interrupt and
terminate signals can be controlled with onintr, and its
handling of hangups can be controlled with hup and nohup.
The shell exits on a hangup (see also the logout shell
variable). By default, the shell's children do too, but
the shell does not send them a hangup when it exits. hup
arranges for the shell to send a hangup to a child when it
exits, and nohup sets a child to ignore hangups.
Terminal management (+)
The shell uses three different sets of terminal (``tty'')
modes: `edit', used when editing, `quote', used when quot-
ing literal characters, and `execute', used when executing
commands. The shell holds some settings in each mode con-
stant, 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 modi-
fied with the setty builtin. Note that although the edi-
tor 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 com-
mand line.
On systems that support SIGWINCH or SIGWINDOW, the shell
adapts to window resizing automatically and adjusts the
environment variables LINES and COLUMNS if set. If the
environment variable TERMCAP contains li# and co# fields,
the shell adjusts them to reflect the new window size.
REFERENCE
The next sections of this manual describe all of the
available Builtin commands, Special aliases and Special
shell variables.
Builtin commands
%job A synonym for the fg builtin command.
%job & A synonym for the bg builtin command.
: Does nothing, successfully.
@
@ name = expr
@ name[index] = expr
@ name++|--
@ name[index]++|--
The first form prints the values of all shell
variables.
The second form assigns the value of expr to name.
The third form assigns the value of expr to the
index'th component of name; both name and its
index'th component must already exist.
expr may contain the operators `*', `+', etc. as
in C. If expr contains `<', `>', `&' or `' then
at least that part of expr must be placed within
`()'. Note that the syntax of expr has nothing to
do with that described under Expressions.
The fourth and fifth forms increment (`++') or
decrement (`--') name or its index'th component.
The space between `@' and name is required. The
spaces between name and `=' and between `=' and
expr are optional. Components of expr must be
separated by spaces.
alias [name [wordlist]]
Without arguments, prints all aliases. With name,
prints the alias for name. With name and
wordlist, assigns wordlist as the alias of name.
wordlist is command and filename substituted.
name may not be `alias' or `unalias'. See also
the unalias builtin command.
alloc Shows the amount of dynamic memory acquired, bro-
ken down into used and free memory. With an argu-
ment shows the number of free and used blocks in
each size category. The categories start at size
8 and double at each step. This command's output
may vary across system types, since 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 descrip-
tion 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 alterna-
tive key map. This is the key map used in vi
command mode.
-b key is interpreted as a control character
written ^character (e.g. `^A') or C-character
(e.g. `C-A'), a meta character written M-char-
acter (e.g. `M-A'), a function key written F-
string (e.g. `F-string'), or an extended pre-
fix key written X-character (e.g. `X-A').
-k key is interpreted as a symbolic arrow key
name, which may be one of `down', `up', `left'
or `right'.
-r Removes key's binding. Be careful: `bindkey
-r' does not bind key to self-insert-command
(q.v.), it unbinds key completely.
-c command is interpreted as a builtin or exter-
nal command instead of an editor command.
-s command is taken as a literal string and
treated as terminal input when key is typed.
Bound keys in command are themselves reinter-
preted, and this continues for ten levels of
interpretation.
-- Forces a break from option processing, so the
next word is taken as key even if it begins
with '-'.
-u (or any invalid option)
Prints a usage message.
key may be a single character or a string. If a
command is bound to a string, the first character
of the string is bound to sequence-lead-in and the
entire string is bound to the command.
Control characters in key can be literal (they can
be typed by preceding them with the editor command
quoted-insert, normally bound to `^V') or written
caret-character style, e.g. `^A'. Delete is writ-
ten `^?' (caret-question mark). key and command
can contain backslashed escape sequences (in the
style of System V echo(1)) as follows:
\a Bell
\b Backspace
\e Escape
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
\v Vertical tab
\nnn The ASCII character corresponding to
the octal number nnn
`\' nullifies the special meaning of the following
character, if it has any, notably `\' and `^'.
break Causes execution to resume after the end of the
nearest enclosing foreach or while. The remaining
commands on the current line are executed. Multi-
level breaks are thus possible by writing them all
on one line.
breaksw Causes a break from a switch, resuming after the
endsw.
builtins (+)
Prints the names of all builtin commands.
bye (+) A synonym for the logout builtin command. Avail-
able 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 substitu-
tions). (+) If name is not a subdirectory of the
current directory (and does not begin with `/',
`./' or `../'), each component of the variable
cdpath is checked to see if it has a subdirectory
name. Finally, if all else fails but name is a
shell variable whose value begins with `/', then
this is tried to see if it is a directory.
With -p, prints the final directory stack, just
like dirs. The -l, -n and -v flags have the same
effect on cd as on dirs, and they imply -p. (+)
See also the implicitcd shell variable.
chdir A synonym for the cd builtin command.
complete [command
[word/pattern/list[:select]/[[suffix]/] ...]] (+)
Without arguments, lists all completions. With
command, lists completions for command. With com-
mand and word etc., defines completions.
command may be a full command name or a glob-pat-
tern (see Filename substitution). It can begin
with `-' to indicate that completion should be
used only when command is ambiguous.
word specifies which word relative to the current
word is to be completed, and may be one of the
following:
c Current-word completion. pattern is a
glob-pattern which must match the begin-
ning of the current word on the command
line. pattern is ignored when completing
the current word.
C Like c, but includes pattern when complet-
ing the current word.
n Next-word completion. pattern is a glob-
pattern which must match the beginning of
the previous word on the command line.
N Like n, but must match the beginning of
the word two before the current word.
p Position-dependent completion. pattern is
a numeric range, with the same syntax used
to index shell variables, which must
include the current word.
list, the list of possible completions, may be one
of the following:
a Aliases
b Bindings (editor commands)
c Commands (builtin or external com-
mands)
C External commands which begin with the
supplied path prefix
d Directories
D Directories which begin with the sup-
plied path prefix
e Environment variables
f Filenames
F Filenames which begin with the sup-
plied path prefix
g Groupnames
j Jobs
l Limits
n Nothing
s Shell variables
S Signals
t Plain (``text'') files
T Plain (``text'') files which begin
with the supplied path prefix
v Any variables
u Usernames
x Like n, but prints select when list-
choices is used.
X Completions
$var Words from the variable var
(...) Words from the given list
`...` Words from the output of command
select is an optional glob-pattern. If given,
only words from list which match select are con-
sidered 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 explana-
tory 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 com-
pleting 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 posi-
tion 0, `p/0') which begin with `co' (thus match-
ing `co*') to `compress' (the only word in the
list). The leading `-' indicates that this com-
pletion is to be used only with ambiguous com-
mands.
> complete find 'n/-user/u/'
is an example of n-type completion. Any word fol-
lowing `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 direc-
tory because we used lowercase c.
Different lists are useful with different com-
mands.
> 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 exam-
ples 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.cor-
nell.edu)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu
> ftp [^C]
> set hostnames = (rtfm.mit.edu tesla.ee.cor-
nell.edu uunet.uu.net)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net
or from a command run at completion time:
> complete kill 'p/*/`ps | awk \{print\
\$1\}`/'
> kill -9 [^D]
23113 23377 23380 23406 23429 23529 23530 PID
Note that the complete command does not itself
quote its arguments, so the braces, space and `$'
in `{print $1}' must be quoted explicitly.
One command can have multiple completions:
> complete dbx 'p/2/(core)/' 'p/*/c/'
completes the second argument to `dbx' with the
word `core' and all other arguments with commands.
Note that the positional completion is specified
before the next-word completion. Since comple-
tions are evaluated from left to right, if the
next-word completion were specified first it would
always match and the positional completion would
never be executed. This is a common mistake when
defining a completion.
The select pattern is useful when a command takes
only files with particular forms as arguments. For
example,
> complete cc 'p/*/f:*.[cao]/'
completes `cc' arguments only to files ending in
`.c', `.a', or `.o'. select can also exclude
files, using negation of a glob-pattern as
described under Filename substitution. One might
use
> complete rm
'p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/'
to exclude precious source code from `rm' comple-
tion. Of course, one could still type excluded
names manually or override the completion mecha-
nism 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 comple-
tion to files beginning with a particular path
prefix. For example, the Elm mail program uses `='
as an abbreviation for one's mail directory. One
might use
> complete elm c@=@F:$HOME/Mail/@
to complete `elm -f =' as if it were `elm -f
~/Mail/'. Note that we used `@' instead of `/' to
avoid confusion with the select argument, and we
used `$HOME' instead of `~' because home directory
substitution only works at the beginning of a
word.
suffix is used to add a nonstandard suffix (not
space or `/' for directories) to completed words.
> complete finger 'c/*@/$hostnames/' 'p/1/u/@'
completes arguments to `finger' from the list of
users, appends an `@', and then completes after
the `@' from the `hostnames' variable. Note again
the order in which the completions are specified.
Finally, here's a complex example for inspiration:
> complete find \
'n/-name/f/' 'n/-newer/f/' 'n/-{,n}cpio/f/' \
'n/-exec/c/' 'n/-ok/c/' 'n/-user/u/' \
'n/-group/g/' 'n/-fstype/(nfs 4.2)/' \
'n/-type/(b c d f l p s)/' \
'c/-/(name newer cpio ncpio exec ok user \
group fstype type atime ctime depth inum \
ls mtime nogroup nouser perm print prune \
size xdev)/' \
'p/*/d/'
This completes words following `-name', `-newer',
`-cpio' or `ncpio' (note the pattern which matches
both) to files, words following `-exec' or `-ok'
to commands, words following `user' and `group' to
users and groups respectively and words following
`-fstype' or `-type' to members of the given
lists. It also completes the switches themselves
from the given list (note the use of c-type com-
pletion) and completes anything not otherwise com-
pleted to a directory. Whew.
Remember that programmed completions are ignored
if the word being completed is a tilde substitu-
tion (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 com-
mand.
continue
Continues execution of the nearest enclosing while
or foreach. The rest of the commands on the cur-
rent 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 direc-
tory 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 postions. (+) 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 pre-
sumably 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 nor-
mally 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 emu-
late (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 term-
cap(5)) in args. For example, 'echotc home' sends
the cursor to the home position, 'echotc cm 3 10'
sends it to column 3 and row 10, and 'echotc ts 0;
echo "This is a test."; echotc fs' prints "This is
a test." in the status line.
If arg is 'baud', 'cols', 'lines', 'meta' or
'tabs', prints the value of that capability ("yes"
or "no" indicating that the terminal does or does
not have that capability). One might use this to
make the output from a shell script less verbose
on slow terminals, or limit command output to the
number of lines on the screen:
> set history=`echotc lines`
> @ history--
Termcap strings may contain wildcards which will
not echo correctly. One should use double quotes
when setting a shell variable to a terminal capa-
bility 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 exe-
cute commands generated as the result of command
or variable substitution, since 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 spec-
ified 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 out-
put. Useful for programs which wish to use the
shell to filename expand a list of words.
goto word
word is filename and command-substituted to yield
a string of the form `label'. The shell rewinds
its input as much as possible, searches for a line
of the form `label:', possibly preceded by blanks
or tabs, and continues execution after that line.
hashstat
Prints a statistics line indicating how effective
the internal hash table has been at locating com-
mands (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 num-
ber 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 speci-
fied, 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 only succeeds when the shells
quit nicely one after another.
With -L, the shell appends filename, which is pre-
sumably a history list saved by the -S option or
the savehist mechanism, to the history list. -M
is like -L, but the contents of filename are
merged into the history list and sorted by times-
tamp. In either case, histfile is used if file-
name is not given and ~/.history is used if hist-
file 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 `his-
tory -L' on startup and, if savehist is set, `his-
tory -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 only in a shell script), causes the shell
to exit on a hangup for the remainder of the
script. See also Signal handling and the nohup
builtin command.
if (expr) command
If expr (an expression, as described under Expres-
sions) evaluates true, then command is executed.
Variable substitution on command happens early, at
the same time it does for the rest of the if com-
mand. command must be a simple command, not an
alias, a pipeline, a command list or a parenthe-
sized 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 exe-
cuted, etc. Any number of else-if pairs are pos-
sible; 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 environ-
ment. 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 sys-
tems, prints the site on which each job is execut-
ing.
kill [-signal] %job|pid ...
kill -l The first form sends the specified signal (or, if
none is given, the TERM (terminate) signal) to the
specified jobs or processes. job may be a number,
a string, `', `%', `+' or `-' as described under
Jobs. Signals are either given by number or by
name (as given in /usr/include/signal.h, stripped
of the prefix `SIG'). There is no default job;
saying just `kill' does not send a signal to the
current job. If the signal being sent is TERM
(terminate) or HUP (hangup), then the job or pro-
cess is sent a CONT (continue) signal as well.
The second form lists the signal names.
limit [-h] [resource [maximum-use]]
Limits the consumption by the current process and
each process it creates to not individually exceed
maximum-use on the specified resource. If no maxi-
mum-use is given, then the current limit is
printed; if no resource is given, then all limita-
tions are given. If the -h flag is given, the
hard limits are used instead of the current lim-
its. The hard limits impose a ceiling on the val-
ues of the current limits. Only the super-user
may raise the hard limits, but a user may lower or
raise the current limits within the legal range.
Controllable resources currently include cputime
(the maximum number of cpu-seconds to be used by
each process), filesize (the largest single file
which can be created), datasize (the maximum
growth of the data+stack region via sbrk(2) beyond
the end of the program text), stacksize (the maxi-
mum size of the automatically-extended stack
region), coredumpsize (the size of the largest
core dump that will be created), and memoryuse,
the maximum amount of physical memory a process
may have allocated to it at a given time.
maximum-use may be given as a (floating point or
integer) number followed by a scale factor. For
all limits other than cputime the default scale is
`k' or `kilobytes' (1024 bytes); a scale factor of
`m' or `megabytes' may also be used. For cputime
the default scaling is `seconds', while `m' for
minutes or `h' for hours, or a time of the form
`mm:ss' giving minutes and seconds may be used.
For both resource names and scale factors, unam-
biguous prefixes of the names suffice.
log (+) Prints the watch shell variable and reports on
each user indicated in watch who is logged in,
regardless of when they last logged in. See also
watchlog.
login Terminates a login shell, replacing it with an
instance of /bin/login. This is one way to log
off, included for compatibility with sh(1).
logout Terminates a login shell. Especially useful if
ignoreeof is set.
ls-F [-switch ...] [file ...] (+)
Lists files like `ls -F', but much faster. It
identifies each type of special file in the list-
ing with a special character:
/ Directory
* Executable
# Block device
% Character device
| Named pipe (systems with named pipes only)
= Socket (systems with sockets only)
@ Symbolic link (systems with symbolic links
only)
+ Hidden directory (AIX only) or context depen-
dent (HP/UX only)
: Network special (HP/UX only)
If the listlinks shell variable is set, symbolic
links are identified in more detail (only, of
course, on systems which have them):
@ Symbolic link to a non-directory
> Symbolic link to a directory
& Symbolic link to nowhere
listlinks also slows down ls-F and causes parti-
tions holding files pointed to by symbolic links
to be mounted.
If the listflags shell variable is set to `x', `a'
or `A', or any combination thereof (e.g. `xA'),
they are used as flags to ls-F, making it act like
`ls -xF', `ls -Fa', `ls -FA' or a combination
(e.g. `ls -FxA'). On machines where `ls -C' is
not the default, ls-F acts like `ls -CF', unless
listflags contains an `x', in which case it acts
like `ls -xF'. ls-F passes its arguments to ls(1)
if it is given any switches, so `alias ls ls-F'
generally does the right thing.
The ls-F builtin can list files using different
colors depending on the filetype or extension. See
the color tcsh variable and the LS_COLORS environ-
ment variable.
migrate [-site] pid|%jobid ... (+)
migrate -site (+)
The first form migrates the process or job to the
site specified or the default site determined by
the system path. The second form is equivalent to
`migrate -site $$': it migrates the current pro-
cess to the specified site. Migrating the shell
itself can cause unexpected behavior, since the
shell does not like to lose its tty. (TCF only)
newgrp [-] group (+)
Equivalent to `exec newgrp'; see newgrp(1).
Available only if the shell was so compiled; see
the version shell variable.
nice [+number] [command]
Sets the scheduling priority for the shell to num-
ber, or, without number, to 4. With command, runs
command at the appropriate priority. The greater
the number, the less cpu the process gets. The
super-user may specify negative priority by using
`nice -number ...'. Command is always executed in
a sub-shell, and the restrictions placed on com-
mands in simple if statements apply.
nohup [command]
With command, runs command such that it will
ignore hangup signals. Note that commands may set
their own response to hangups, overriding nohup.
Without an argument (allowed only in a shell
script), causes the shell to ignore hangups for
the remainder of the script. See also Signal han-
dling and the hup builtin command.
notify [%job ...]
Causes the shell to notify the user asynchronously
when the status of any of the specified jobs (or,
without %job, the current job) changes, instead of
waiting until the next prompt as is usual. job
may be a number, a string, `', `%', `+' or `-' as
described under Jobs. See also the notify shell
variable.
onintr [-|label]
Controls the action of the shell on interrupts.
Without arguments, restores the default action of
the shell on interrupts, which is to terminate
shell scripts or to return to the terminal command
input level. With `-', causes all interrupts to
be ignored. With label, causes the shell to exe-
cute a `goto label' when an interrupt is received
or a child process terminates because it was
interrupted.
onintr is ignored if the shell is running detached
and in system startup files (see FILES), where
interrupts are disabled anyway.
popd [-p] [-l] [-n|-v] [+n]
Without arguments, pops the directory stack and
returns to the new top directory. With a number
`+n', discards the n'th entry in the stack.
Finally, all forms of popd print the final direc-
tory stack, just like dirs. The pushdsilent shell
variable can be set to prevent this and the -p
flag can be given to override pushdsilent. The
-l, -n and -v flags have the same effect on popd
as on dirs. (+)
printenv [name] (+)
Prints the names and values of all environment
variables or, with name, the value of the environ-
ment variable name.
pushd [-p] [-l] [-n|-v] [name|+n]
Without arguments, exchanges the top two elements
of the directory stack. If pushdtohome is set,
pushd without arguments does `pushd ~', like cd.
(+) With name, pushes the current working direc-
tory onto the directory stack and changes to name.
If name is `-' it is interpreted as the previous
working directory (see Filename substitution). (+)
If dunique is set, pushd removes any instances of
name from the stack before pushing it onto the
stack. (+) With a number `+n', rotates the nth
element of the directory stack around to be the
top element and changes to it. If dextract is
set, however, `pushd +n' extracts the nth direc-
tory, pushes it onto the top of the stack and
changes to it. (+)
Finally, all forms of pushd print the final direc-
tory stack, just like dirs. The pushdsilent shell
variable can be set to prevent this and the -p
flag can be given to override pushdsilent. The
-l, -n and -v flags have the same effect on pushd
as on dirs. (+)
rehash Causes the internal hash table of the contents of
the directories in the path variable to be recom-
puted. This is needed if new commands are added
to directories in path while you are logged in.
This should only be necessary if you add commands
to one of your own directories, or if a systems
programmer changes the contents of one of the sys-
tem directories. Also flushes the cache of home
directories built by tilde expansion.
repeat count command
The specified command, which is subject to the
same restrictions as the command in the one line
if statement above, is executed count times. I/O
redirections occur exactly once, even if count is
0.
rootnode //nodename (+)
Changes the rootnode to //nodename, so that `/'
will be interpreted as `//nodename'. (Domain/OS
only)
sched (+)
sched [+]hh:mm command (+)
sched -n (+)
The first form prints the scheduled-event list.
The sched shell variable may be set to define the
format in which the scheduled-event list is
printed. The second form adds command to the
scheduled-event list. For example,
> sched 11:00 echo It\'s eleven o\'clock.
causes the shell to echo `It's eleven o'clock.' at
11 AM. The time may be in 12-hour AM/PM format
> sched 5pm set prompt='[%h] It\'s after 5; go
home: >'
or may be relative to the current time:
> sched +2:15 /usr/lib/uucp/uucico -r1 -sother
A relative time specification may not use AM/PM
format. The third form removes item n from the
event list:
> sched
1 Wed Apr 4 15:42 /usr/lib/uucp/uucico
-r1 -sother
2 Wed Apr 4 17:00 set prompt=[%h] It's
after 5; go home: >
> sched -2
> sched
1 Wed Apr 4 15:42 /usr/lib/uucp/uucico
-r1 -sother
A command in the scheduled-event list is executed
just before the first prompt is printed after the
time when the command is scheduled. It is possi-
ble to miss the exact time when the command is to
be run, but an overdue command will execute at the
next prompt. A command which comes due while the
shell is waiting for user input is executed imme-
diately. However, normal operation of an already-
running command will not be interrupted so that a
scheduled-event list element may be run.
This mechanism is similar to, but not the same as,
the at(1) command on some Unix systems. Its major
disadvantage is that it may not run a command at
exactly the specified time. Its major advantage
is that because sched runs directly from the
shell, it has access to shell variables and other
structures. This provides a mechanism for chang-
ing one's working environment based on the time of
day.
set
set name ...
set name=word ...
set [-r] [-f|-l] name=(wordlist) ... (+)
set name[index]=word ...
set -r (+)
set -r name ... (+)
set -r name=word ... (+)
The first form of the command prints the value of
all shell variables. Variables which contain more
than a single word print as a parenthesized word
list. The second form sets name to the null
string. The third form sets name to the single
word. The fourth form sets name to the list of
words in wordlist. In all cases the value is com-
mand and filename expanded. If -r is specified,
the value is set read-only. If -f or -l are speci-
fied, set only unique words keeping their order.
-f prefers the first occurrence of a word, and -l
the last. first occurance of the word The fifth
form sets the index'th component of name to word;
this component must already exist. The sixth form
lists the names (only) of all shell variables
which are read-only. The seventh form makes name
read-only, whether or not it has a value. The
second form sets name to the null string. The
eighth form is the same as the third form, but
make name read-only at the same time.
These arguments can be repeated to set and/or make
read-only multiple variables in a single set com-
mand. Note, however, that variable expansion hap-
pens for all arguments before any setting occurs.
Note also that `=' can be adjacent to both name
and word or separated from both by whitespace, but
cannot be adjacent to only one or the other. See
also the unset builtin command.
setenv [name [value]]
Without arguments, prints the names and values of
all environment variables. Given name, sets the
environment variable name to value or, without
value, to the null string.
setpath path (+)
Equivalent to setpath(1). (Mach only)
setspath LOCAL|site|cpu ... (+)
Sets the system execution path. (TCF only)
settc cap value (+)
Tells the shell to believe that the terminal capa-
bility cap (as defined in termcap(5)) has the
value value. No sanity checking is done. Concept
terminal users may have to `settc xn no' to get
proper wrapping at the rightmost column.
setty [-d|-q|-x] [-a] [[+|-]mode] (+)
Controls which tty modes (see Terminal management)
the shell does not allow to change. -d, -q or -x
tells setty to act on the `edit', `quote' or `exe-
cute' set of tty modes respectively; without -d,
-q or -x, `execute' is used.
Without other arguments, setty lists the modes in
the chosen set which are fixed on (`+mode') or off
(`-mode'). The available modes, and thus the dis-
play, vary from system to system. With -a, lists
all tty modes in the chosen set whether or not
they are fixed. With +mode, -mode or mode, fixes
mode on or off or removes control from mode in the
chosen set. For example, `setty +echok echoe'
fixes `echok' mode on and allows commands to turn
`echoe' mode on or off, both when the shell is
executing commands.
setxvers [string] (+)
Set the experimental version prefix to string, or
removes it if string is omitted. (TCF only)
shift [variable]
Without arguments, discards argv[1] and shifts the
members of argv to the left. It is an error for
argv not to be set or to have less than one word
as value. With variable, performs the same func-
tion on variable.
source [-h] name [args ...]
The shell reads and executes commands from name.
The commands are not placed on the history list.
If any args are given, they are placed in argv.
(+) source commands may be nested; if they are
nested too deeply the shell may run out of file
descriptors. An error in a source at any level
terminates all nested source commands. With -h,
commands are placed on the history list instead of
being executed, much like `history -L'.
stop %job|pid ...
Stops the specified jobs or processes which are
executing in the background. job may be a number,
a string, `', `%', `+' or `-' as described under
Jobs. There is no default job; saying just `stop'
does not stop the current job.
suspend Causes the shell to stop in its tracks, much as if
it had been sent a stop signal with ^Z. This is
most often used to stop shells started by su(1).
switch (string)
case str1:
...
breaksw
...
default:
...
breaksw
endsw Each case label is successively matched, against
the specified string which is first command and
filename expanded. The file metacharacters `*',
`?' and `[...]' may be used in the case labels,
which are variable expanded. If none of the
labels match before a `default' label is found,
then the execution begins after the default label.
Each case label and the default label must appear
at the beginning of a line. The command breaksw
causes execution to continue after the endsw. Oth-
erwise control may fall through case labels and
default labels as in C. If no label matches and
there is no default, execution continues after the
endsw.
telltc (+)
Lists the values of all terminal capabilities (see
termcap(5)).
time [command]
Executes command (which must be a simple command,
not an alias, a pipeline, a command list or a
parenthesized command list) and prints a time sum-
mary as described under the time variable. If
necessary, an extra shell is created to print the
time statistic when the command completes. With-
out command, prints a time summary for the current
shell and its children.
umask [value]
Sets the file creation mask to value, which is
given in octal. Common values for the mask are
002, giving all access to the group and read and
execute access to others, and 022, giving read and
execute access to the group and others. Without
value, prints the current file creation mask.
unalias pattern
Removes all aliases whose names match pattern.
`unalias *' thus removes all aliases. It is not
an error for nothing to be unaliased.
uncomplete pattern (+)
Removes all completions whose names match pattern.
`uncomplete *' thus removes all completions. It
is not an error for nothing to be uncompleted.
unhash Disables use of the internal hash table to speed
location of executed programs.
universe universe (+)
Sets the universe to universe. (Masscomp/RTU only)
unlimit [-h] [resource]
Removes the limitation on resource or, if no
resource is specified, all resource limitations.
With -h, the corresponding hard limits are
removed. Only the super-user may do this.
unset pattern
Removes all variables whose names match pattern,
unless they are read-only. `unset *' thus removes
all variables unless they are read-only; this is a
bad idea. It is not an error for nothing to be
unset.
unsetenv pattern
Removes all environment variables whose names
match pattern. `unsetenv *' thus removes all
environment variables; this is a bad idea. It is
not an error for nothing to be unsetenved.
ver [systype [command]] (+)
Without arguments, prints SYSTYPE. With systype,
sets SYSTYPE to systype. With systype and command,
executes command under systype. systype may be
`bsd4.3' or `sys5.3'. (Domain/OS only)
wait The shell waits for all background jobs. If the
shell is interactive, an interrupt will disrupt
the wait and cause the shell to print the names
and job numbers of all outstanding jobs.
warp universe (+)
Sets the universe to universe. (Convex/OS only)
watchlog (+)
An alternate name for the log builtin command
(q.v.). Available only if the shell was so com-
piled; see the version shell variable.
where command (+)
Reports all known instances of command, including
aliases, builtins and executables in path.
which command (+)
Displays the command that will be executed by the
shell after substitutions, path searching, etc.
The builtin command is just like which(1), but it
correctly reports tcsh aliases and builtins and is
10 to 100 times faster. See also the which-com-
mand editor command.
while (expr)
...
end Executes the commands between the while and the
matching end while expr (an expression, as
described under Expressions) evaluates non-zero.
while and end must appear alone on their input
lines. break and continue may be used to termi-
nate or continue the loop prematurely. If the
input is a terminal, the user is prompted the
first time through the loop as with foreach.
Special aliases (+)
If set, each of these aliases executes automatically at
the indicated time. They are all initially undefined.
beepcmd Runs when the shell wants to ring the terminal
bell.
cwdcmd Runs after every change of working directory. For
example, if the user is working on an X window
system using xterm(1) and a re-parenting window
manager that supports title bars such as twm(1)
and does
> alias cwdcmd 'echo -n "^[]2;${HOST}:$cwd
^G"'
then the shell will change the title of the run-
ning xterm(1) to be the name of the host, a colon,
and the full current working directory. A fancier
way to do that is
> alias cwdcmd 'echo -n
"^[]2;${HOST}:$cwd^G^[]1;${HOST}^G"'
This will put the hostname and working directory
on the title bar but only the hostname in the icon
manager menu.
Note that putting a cd, pushd or popd in cwdcmd
may cause an infinite loop. It is the author's
opinion that anyone doing so will get what they
deserve.
periodic
Runs every tperiod minutes. This provides a conve-
nient means for checking on common but infrequent
changes such as new mail. For example, if one does
> set tperiod = 30
> alias periodic checknews
then the checknews(1) program runs every 30 min-
utes. If periodic is set but tperiod is unset or
set to 0, periodic behaves like precmd.
precmd Runs just before each prompt is printed. For exam-
ple, if one does
> alias precmd date
then date(1) runs just before the shell prompts
for each command. There are no limits on what
precmd can be set to do, but discretion should be
used.
shell Specifies the interpreter for executable scripts
which do not themselves specify an interpreter.
The first word should be a full path name to the
desired interpreter (e.g. `/bin/csh' or
`/usr/local/bin/tcsh').
Special shell variables
The variables described in this section have special mean-
ing to the shell.
The shell sets addsuffix, argv, autologout, command,
echo_style, edit, gid, group, home, loginsh, oid, path,
prompt, prompt2, prompt3, shell, shlvl, tcsh, term, tty,
uid, user and version at startup; they do not change
thereafter unless changed by the user. The shell updates
cwd, dirstack, owd and status when necessary, and sets
logout on logout.
The shell synchronizes afsuser, group, home, path, shlvl,
term and user with the environment variables of the same
names: whenever the environment variable changes the shell
changes the corresponding shell variable to match (unless
the shell variable is read-only) and vice versa. Note that
although cwd and PWD have identical meanings, they are not
synchronized in this manner, and that the shell automati-
cally interconverts the different formats of path and
PATH.
addsuffix (+)
If set, filename completion adds `/' to the end of
directories and a space to the end of normal files
when they are matched exactly. Set by default.
afsuser (+)
If set, autologout's autolock feature uses its
value instead of the local username for kerberos
authentication.
ampm (+)
If set, all times are shown in 12-hour AM/PM for-
mat.
argv The arguments to the shell. Positional parameters
are taken from argv, i.e. `$1' is replaced by
`$argv[1]', etc. Set by default, but usually
empty in interactive shells.
autocorrect (+)
If set, the spell-word editor command is invoked
automatically before each completion attempt.
autoexpand (+)
If set, the expand-history editor command is
invoked automatically before each completion
attempt.
autolist (+)
If set, possibilities are listed after an ambigu-
ous completion. If set to `ambiguous', possibili-
ties are listed only when no new characters are
added by completion.
autologout (+)
The first word is the number of minutes of inac-
tivity before automatic logout. The optional sec-
ond word is the number of minutes of inactivity
before automatic locking. When the shell automat-
ically logs out, it prints `auto-logout', sets the
variable logout to `automatic' and exits. When
the shell automatically locks, the user is
required to enter his password to continue work-
ing. Five incorrect attempts result in automatic
logout. Set to `60' (automatic logout after 60
minutes, and no locking) by default in login and
superuser shells, but not if the shell thinks it
is running under a window system (i.e. the DISPLAY
environment variable is set), the tty is a pseudo-
tty (pty) or the shell was not so compiled (see
the version shell variable). See also the afsuser
and logout shell variables.
backslash_quote (+)
If set, backslashes (`\') always quote `\', `'',
and `"'. This may make complex quoting tasks eas-
ier, but it can cause syntax errors in csh(1)
scripts.
cdpath A list of directories in which cd should search
for subdirectories if they aren't found in the
current directory.
color If set, it enables color display for the builtin
ls-F and it passes --color=auto to ls. Alterna-
tively, it can be set to only ls-F or only ls to
enable color only to one command. Setting it to
nothing is equivalent to setting it to (ls-F ls).
command (+)
If set, the command which was passed to the shell
with the -c flag (q.v.).
complete (+)
If 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.
correct (+)
If set to `cmd', commands are automatically
spelling-corrected. If set to `complete', com-
mands are automatically completed. If set to
`all', the entire command line is corrected.
cwd The full pathname of the current directory. See
also the dirstack and owd shell variables.
dextract (+)
If set, `pushd +n' extracts the nth directory from
the directory stack rather than rotating it to the
top.
dirsfile (+)
The default location in which `dirs -S' and `dirs
-L' look for a history file. If unset, ~/.cshdirs
is used. Because only ~/.tcshrc is normally
sourced before ~/.cshdirs, dirsfile should be set
in ~/.tcshrc rather than ~/.login.
dirstack (+)
An array of all the directories on the directory
stack. `$dirstack[1]' is the current working
directory, `$dirstack[2]' the first directory on
the stack, etc. Note that the current working
directory is `$dirstack[1]' but `=0' in directory
stack substitutions, etc. One can change the
stack arbitrarily by setting dirstack, but the
first element (the current working directory) is
always correct. See also the cwd and owd shell
variables.
dspmbyte (+)
If set to `euc', it enables display and editing
EUC-kanji(japanese) code. If set to `sjis', it
enables display and editing Shift-JIS(japanese)
code. If set to following format, it enables dis-
play and editing original multi-byte code format:
> set dspkanji = 0000....(256 bytes)....0000
table length require just 256 byte. Each character
of 256 characters corresponds from the left from
0x01,0x02... to 0xff of ASCII code. Each character
is set to number 0,1,2 and 3. Each number has the
following meanings:
0 ... not use for multi-byte character.
1 ... use for first byte of multi-byte charcter.
2 ... use for second byte of multi-byte charac-
ter.
3 ... use for both of first byte and second byte
of multi-byte character.
Exapmle:
if set `001322', first character(means 0x00 of
ASCII code) and second character(means 0x01 of
ASCII code) is set to `0'. then, it is not use for
multi-byte character.3rd character(0x02) is set
'2'. it is use for first byte of multi-byte charc-
ter. 4th character(0x03) is set '3'. it is use for
both of first byte and second byte of multi-byte
character. 5th and 6th character(0x04,0x05) is set
'2'. it is use for second byte of multi-byte
charcter.
dunique (+)
If set, pushd removes any instances of name from
the stack before pushing it onto the stack.
echo If set, each command with its arguments is echoed
just before it is executed. For non-builtin com-
mands all expansions occur before echoing.
Builtin commands are echoed before command and
filename substitution, since these substitutions
are then done selectively. Set by the -x command
line option.
echo_style (+)
The style of the echo builtin. May be set to
bsd Don't echo a newline if the first argument
is `-n'.
sysv Recognize backslashed escape sequences in
echo strings.
both Recognize both the `-n' flag and back-
slashed escape sequences; the default.
none Recognize neither.
Set by default to the local system default. The
BSD and System V options are described in the
echo(1) manpages on the appropriate systems.
edit (+)
If set, the command-line editor is used. Set by
default in interactive shells.
ellipsis (+)
If set, the `%c'/`%.' and `%C' prompt sequences
(see the prompt shell variable) indicate skipped
directories with an ellipsis (`...') instead of
`/<skipped>'.
fignore (+)
Lists file name suffixes to be ignored by comple-
tion.
filec In tcsh, completion is always used and this vari-
able is ignored. If set in csh, filename comple-
tion is used.
gid (+) The user's real group ID.
group (+)
The user's group name.
histchars
A string value determining the characters used in
History substitution (q.v.). The first character
of its value is used as the history substitution
character, replacing the default character `!'.
The second character of its value replaces the
character `^' in quick substitutions.
histdup (+)
Controls handling of duplicate entries in the his-
tory list. If set to `all' only unique history
events are entered in the history list. If set to
`prev' and the last history event is the same as
the current command, then the current command is
not entered in the history. If set to `erase' and
the same event is found in the history list, that
old event gets erased and the current one gets
inserted. Note that the `prev' and `all' options
renumber history events so there are no gaps.
histfile (+)
The default location in which `history -S' and
`history -L' look for a history file. If unset,
~/.history is used. histfile is useful when shar-
ing the same home directory between different
machines, or when saving separate histories on
different terminals. Because only ~/.tcshrc is
normally sourced before ~/.history, histfile
should be set in ~/.tcshrc rather than ~/.login.
histlit (+)
If set, builtin and editor commands and the save-
hist mechanism use the literal (unexpanded) form
of lines in the history list. See also the tog-
gle-literal-history editor command.
history The first word indicates the number of history
events to save. The optional second word (+)
indicates the format in which history is printed;
if not given, `%h\t%T\t%R\n' is used. The format
sequences are described below under prompt; note
the variable meaning of `%R'. Set to `100' by
default.
home Initialized to the home directory of the invoker.
The filename expansion of `~' refers to this vari-
able.
ignoreeof
If set to the empty string or `0' and the input
device is a terminal, the end-of-file command
(usually generated by the user by typing `^D' on
an empty line) causes the shell to print `Use
"exit" to leave tcsh.' instead of exiting. This
prevents the shell from accidentally being killed.
If set to a number n, the shell ignores n - 1 con-
secutive end-of-files and exits on the nth. (+) If
unset, `1' is used, i.e. the shell exits on a sin-
gle `^D'.
implicitcd (+)
If set, the shell treats a directory name typed as
a command as though it were a request to change to
that directory. If set to verbose, the change of
directory is echoed to the standard output. This
behavior is inhibited in non-interactive shell
scripts, or for command strings with more than one
word. Changing directory takes precedence over
executing a like-named command, but it is done
after alias substitutions. Tilde and variable
expansions work as expected.
inputmode (+)
If set to `insert' or `overwrite', puts the editor
into that input mode at the beginning of each
line.
listflags (+)
If set to `x', `a' or `A', or any combination
thereof (e.g. `xA'), they are used as flags to
ls-F, making it act like `ls -xF', `ls -Fa', `ls
-FA' or a combination (e.g. `ls -FxA'): `a' shows
all files (even if they start with a `.'), `A'
shows all files but `.' and `..', and `x' sorts
across instead of down. If the second word of
listflags is set, it is used as the path to
`ls(1)'.
listjobs (+)
If set, all jobs are listed when a job is sus-
pended. If set to `long', the listing is in long
format.
listlinks (+)
If set, the ls-F builtin command shows the type of
file to which each symbolic link points.
listmax (+)
The maximum number of items which the list-choices
editor command will list without asking first.
listmaxrows (+)
The maximum number of rows of items which the
list-choices editor command will list without ask-
ing first.
loginsh (+)
Set by the shell if it is a login shell. Setting
or unsetting it within a shell has no effect. See
also shlvl.
logout (+)
Set by the shell to `normal' before a normal
logout, `automatic' before an automatic logout,
and `hangup' if the shell was killed by a hangup
signal (see Signal handling). See also the autol-
ogout shell variable.
mail The names of the files or directories to check for
incoming mail, separated by whitespace, and
optionally preceeded by a numeric word. Before
each prompt, if 10 minutes have passed since the
last check, the shell checks each file and says
`You have new mail.' (or, if mail contains multi-
ple files, `You have new mail in name.') if the
filesize is greater than zero in size and has a
modification time greater than its access time.
If you are in a login shell, then no mail file is
reported unless it has been modified after the
time the shell has started up, in order to prevent
redundant notifications. Most login programs will
tell you whether or not you have mail when you log
in.
If a file specified in mail is a directory, the
shell will count each file within that directory
as a separate message, and will report `You have n
mails.' or `You have n mails in name.' as appro-
priate. This functionality is provided primarily
for those systems which store mail in this manner,
such as the Andrew Mail System.
If the first word of mail is numeric it is taken
as a different mail checking interval, in seconds.
Under very rare circumstances, the shell may
report `You have mail.' instead of `You have new
mail.'
matchbeep (+)
If set to `never', completion never beeps. If set
to `nomatch', it beeps only when there is no
match. If set to `ambiguous, it beeps when there
are multiple matches. If set to `notunique', it
beeps when there is one exact and other longer
matches. If unset, `ambiguous' is used.
nobeep (+)
If set, beeping is completely disabled. See also
visiblebell.
noclobber
If set, restrictions are placed on output redirec-
tion to insure that files are not accidentally
destroyed and that `>>' redirections refer to
existing files, as described in the Input/output
section.
noglob If set, Filename substitution and Directory stack
substitution (q.v.) are inhibited. This is most
useful in shell scripts which do not deal with
filenames, or after a list of filenames has been
obtained and further expansions are not desirable.
nokanji (+)
If set and the shell supports Kanji (see the ver-
sion shell variable), it is disabled so that the
meta key can be used.
nonomatch
If set, a Filename substitution or Directory stack
substitution (q.v.) which does not match any
existing files is left untouched rather than caus-
ing an error. It is still an error for the sub-
stitution to be malformed, e.g. `echo [' still
gives an error.
nostat (+)
A list of directories (or glob-patterns which
match directories; see Filename substitution) that
should not be stat(2)ed during a completion opera-
tion. This is usually used to exclude directories
which take too much time to stat(2), for example
/afs.
notify If set, the shell announces job completions asyn-
chronously. The default is to present job comple-
tions just before printing a prompt.
oid (+) The user's real organization ID. (Domain/OS only)
owd (+) The old working directory, equivalent to the `-'
used by cd and pushd. See also the cwd and
dirstack shell variables.
path A list of directories in which to look for exe-
cutable commands. A null word specifies the cur-
rent directory. If there is no path variable then
only full path names will execute. path is set by
the shell at startup from the PATH environment
variable or, if PATH does not exist, to a system-
dependent default something like `(/usr/local/bin
/usr/bsd /bin /usr/bin .)'. The shell may put `.'
first or last in path or omit it entirely depend-
ing on how it was compiled; see the version shell
variable. A shell which is given neither the -c
nor the -t option hashes the contents of the
directories in path after reading ~/.tcshrc and
each time path is reset. If one adds a new com-
mand to a directory in path while the shell is
active, one may need to do a rehash for the shell
to find it.
printexitvalue (+)
If set and an interactive program exits with a
non-zero status, the shell prints `Exit status'.
prompt The string which is printed before reading each
command from the terminal. prompt may include any
of the following formatting sequences (+), which
are replaced by the given information:
%/ The current working directory.
%~ The current working directory, but with one's
home directory represented by `~' and other
users' home directories represented by `~user'
as per Filename substitution. `~user' substi-
tution happens only if the shell has already
used `~user' in a pathname in the current ses-
sion.
%c[[0]n], %.[[0]n]
The trailing component of the current working
directory, or n trailing components if a digit
n is given. If n begins with `0', the number
of skipped components precede the trailing
component(s) in the format `/<skipped>trail-
ing'. If the ellipsis shell variable is set,
skipped components are represented by an
ellipsis so the whole becomes `...trailing'.
`~' substitution is done as in `%~' above, but
the `~' component is ignored when counting
trailing components.
%C Like %c, but without `~' substitution.
%h, %!, !
The current history event number.
%M The full hostname.
%m The hostname up to the first `.'.
%S (%s)
Start (stop) standout mode.
%B (%b)
Start (stop) boldfacing mode.
%U (%u)
Start (stop) underline mode.
%t, %@
The time of day in 12-hour AM/PM format.
%T Like `%t', but in 24-hour format (but see the
ampm shell variable).
%p The `precise' time of day in 12-hour AM/PM
format, with seconds.
%P Like `%p', but in 24-hour format (but see the
ampm shell variable).
\c c is parsed as in bindkey.
^c c is parsed as in bindkey.
%% A single `%'.
%n The user name.
%d The weekday in `Day' format.
%D The day in `dd' format.
%w The month in `Mon' format.
%W The month in `mm' format.
%y The year in `yy' format.
%Y The year in `yyyy' format.
%l The shell's tty.
%L Clears from the end of the prompt to end of
the display or the end of the line.
%$ Expands the shell or environment variable name
immediately after the `$'.
%# `>' (or the first character of the promptchars
shell variable) for normal users, `#' (or the
second character of promptchars) for the supe-
ruser.
%{string%}
Includes string as a literal escape sequence.
It should be used only to change terminal
attributes and should not move the cursor
location. This cannot be the last sequence in
prompt.
%? The return code of the command executed just
before the prompt.
%R In prompt2, the status of the parser. In
prompt3, the corrected string. In history,
the history string.
`%B', `%S', `%U' and `%{string%}' are available
only in eight-bit-clean shells; see the version
shell variable.
The bold, standout and underline sequences are
often used to distinguish a superuser shell. For
example,
> set prompt = "%m [%h] %B[%@]%b [%/] you
rang? "
tut [37] [2:54pm] [/usr/accts/sys] you rang? _
Set by default to `%# ' in interactive shells.
prompt2 (+)
The string with which to prompt in while and fore-
ach loops and after lines ending in `\'. The same
format sequences may be used as in prompt (q.v.);
note the variable meaning of `%R'. Set by default
to `%R? ' in interactive shells.
prompt3 (+)
The string with which to prompt when confirming
automatic spelling correction. The same format
sequences may be used as in prompt (q.v.); note
the variable meaning of `%R'. Set by default to
`CORRECT>%R (y|n|e|a)? ' in interactive shells.
promptchars (+)
If set (to a two-character string), the `%#' for-
matting sequence in the prompt shell variable is
replaced with the first character for normal users
and the second character for the superuser.
pushdtohome (+)
If set, pushd without arguments does `pushd ~',
like cd.
pushdsilent (+)
If set, pushd and popd do not print the directory
stack.
recexact (+)
If set, completion completes on an exact match
even if a longer match is possible.
recognize_only_executables (+)
If set, command listing displays only files in the
path that are executable. Slow.
rmstar (+)
If set, the user is prompted before `rm *' is exe-
cuted.
rprompt (+)
The string to print on the right-hand side of the
screen (after the command input) when the prompt
is being displayed on the left. It recognises the
same formatting characters as prompt. It will
automatically disappear and reappear as necessary,
to ensure that command input isn't obscured, and
will only appear if the prompt, command input, and
itself will fit together on the first line. If
edit isn't set, then rprompt will be printed after
the prompt and before the command input.
savedirs (+)
If set, the shell does `dirs -S' before exiting.
savehist
If set, the shell does `history -S' before exit-
ing. If the first word is set to a number, at
most that many lines are saved. (The number must
be less than or equal to history.) If the second
word is set to `merge', the history list is merged
with the existing history file instead of replac-
ing it (if there is one) and sorted by time stamp
and the most recent events are retained. (+)
sched (+)
The format in which the sched builtin command
prints scheduled events; if not given,
`%h\t%T\t%R\n' is used. The format sequences are
described above under prompt; note the variable
meaning of `%R'.
shell The file in which the shell resides. This is used
in forking shells to interpret files which have
execute bits set, but which are not executable by
the system. (See the description of Builtin and
non-builtin command execution.) Initialized to
the (system-dependent) home of the shell.
shlvl (+)
The number of nested shells. Reset to 1 in login
shells. See also loginsh.
status The status returned by the last command. If it
terminated abnormally, then 0200 is added to the
status. Builtin commands which fail return exit
status `1', all other builtin commands return sta-
tus `0'.
symlinks (+)
Can be set to several different values to control
symbolic link (`symlink') resolution:
If set to `chase', whenever the current directory
changes to a directory containing a symbolic link,
it is expanded to the real name of the directory
to which the link points. This does not work for
the user's home directory; this is a bug.
If set to `ignore', the shell tries to construct a
current directory relative to the current direc-
tory before the link was crossed. This means that
cding through a symbolic link and then `cd ..'ing
returns one to the original directory. This only
affects builtin commands and filename completion.
If set to `expand', the shell tries to fix sym-
bolic links by actually expanding arguments which
look like path names. This affects any command,
not just builtins. Unfortunately, this does not
work for hard-to-recognize filenames, such as
those embedded in command options. Expansion may
be prevented by quoting. While this setting is
usually the most convenient, it is sometimes mis-
leading and sometimes confusing when it fails to
recognize an argument which should be expanded. A
compromise is to use `ignore' and use the editor
command normalize-path (bound by default to ^X-n)
when necessary.
Some examples are in order. First, let's set up
some play directories:
> cd /tmp
> mkdir from from/src to
> ln -s from/src to/dist
Here's the behavior with symlinks unset,
> cd /tmp/to/dist; echo $cwd
/tmp/to/dist
> cd ..; echo $cwd
/tmp/from
here's the behavior with symlinks set to `chase',
> cd /tmp/to/dst; echo $cwd
/tmp/from/src
> cd ..; echo $cwd
/tmp/from
here's the behavior with symlinks set to `ignore',
> cd /tmp/to/dist; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/to
and here's the behavior with symlinks set to
`expand'.
> cd /tmp/to/dist; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/to
> cd /tmp/to/dist; echo $cwd
/tmp/to/dst
> cd ".."; echo $cwd
/tmp/from
> /bin/echo ..
/tmp/to
> /bin/echo ".."
..
Note that `expand' expansion 1) works just like
`ignore' for builtins like cd, 2) is prevented by
quoting, and 3) happens before filenames are
passed to non-builtin commands.
tcsh (+)
The version number of the shell in the format
`R.VV.PP', where `R' is the major release number,
`VV' the current version and `PP' the patchlevel.
term The terminal type. Usually set in ~/.login as
described under Startup and shutdown.
time If set to a number, then the time builtin (q.v.)
executes automatically after each command which
takes more than that many CPU seconds. If there
is a second word, it is used as a format string
for the output of the time builtin. (u) The fol-
lowing sequences may be used in the format string:
%U The time the process spent in user mode in cpu
seconds.
%S The time the process spent in kernel mode in
cpu seconds.
%E The elapsed (wall clock) time in seconds.
%P The CPU percentage computed as (%U + %S) / %E.
%W Number of times the process was swapped.
%X The average amount in (shared) text space used
in Kbytes.
%D The average amount in (unshared) data/stack
space used in Kbytes.
%K The total space used (%X + %D) in Kbytes.
%M The maximum memory the process had in use at
any time in Kbytes.
%F The number of major page faults (page needed
to be brought from disk).
%R The number of minor page faults.
%I The number of input operations.
%O The number of output operations.
%r The number of socket messages received.
%s The number of socket messages sent.
%k The number of signals received.
%w The number of voluntary context switches
(waits).
%c The number of involuntary context switches.
Only the first four sequences are supported on
systems without BSD resource limit functions. The
default time format is `%Uu %Ss %E %P %X+%Dk
%I+%Oio %Fpf+%Ww' for systems that support
resource usage reporting and `%Uu %Ss %E %P' for
systems that do not.
Under Sequent's DYNIX/ptx, %X, %D, %K, %r and %s
are not available, but the following additional
sequences are:
%Y The number of system calls performed.
%Z The number of pages which are zero-filled on
demand.
%i The number of times a process's resident set
size was increased by the kernel.
%d The number of times a process's resident set
size was decreased by the kernel.
%l The number of read system calls performed.
%m The number of write system calls performed.
%p The number of reads from raw disk devices.
%q The number of writes to raw disk devices.
and the default time format is `%Uu %Ss $E %P
%I+%Oio %Fpf+%Ww'. Note that the CPU percentage
can be higher than 100% on multi-processors.
tperiod (+)
The period, in minutes, between executions of the
periodic special alias.
tty (+) The name of the tty, or empty if not attached to
one.
uid (+) The user's real user ID.
user The user's login name.
verbose If set, causes the words of each command to be
printed, after history substitution (if any). Set
by the -v command line option.
version (+)
The version ID stamp. It contains the shell's ver-
sion number (see tcsh), origin, release date, ven-
dor, operating system and machine (see VENDOR,
OSTYPE and MACHTYPE) and a comma-separated list of
options which were set at compile time. Options
which are set by default in the distribution are
noted.
8b The shell is eight bit clean; default
7b The shell is not eight bit clean
nls The system's NLS is used; default for systems
with NLS
lf Login shells execute /etc/csh.login before
instead of after /etc/csh.cshrc and ~/.login
before instead of after ~/.tcshrc and ~/.his-
tory.
dl `.' is put last in path for security; default
nd `.' is omitted from path for security
vi vi-style editing is the default rather than
emacs
dtr Login shells drop DTR when exiting
bye bye is a synonym for logout and log is an
alternate name for watchlog
al autologout is enabled; default
kan Kanji is used and the ISO character set is
ignored, unless the nokanji shell variable is
set
sm The system's malloc(3) is used
hb The `#!<program> <args>' convention is emu-
lated when executing shell scripts
ng The newgrp builtin is available
rh The shell attempts to set the REMOTEHOST envi-
ronment variable
afs The shell verifies your password with the ker-
beros server if local authentication fails.
The afsuser shell variable or the AFSUSER
environment variable override your local user-
name if set.
An administrator may enter additional strings to
indicate differences in the local version.
visiblebell (+)
If set, a screen flash is used rather than the
audible bell. See also nobeep.
watch (+)
A list of user/terminal pairs to watch for logins
and logouts. If either the user is `any' all ter-
minals are watched for the given user and vice
versa. Setting watch to `(any any)' watches all
users and terminals. For example,
set watch = (george ttyd1 any console $user
any)
reports activity of the user `george' on ttyd1,
any user on the console, and oneself (or a tres-
passer) on any terminal.
Logins and logouts are checked every 10 minutes by
default, but the first word of watch can be set to
a number to check every so many minutes. For
example,
set watch = (1 any any)
reports any login/logout once every minute. For
the impatient, the log builtin command triggers a
watch report at any time. All current logins are
reported (as with the log builtin) when watch is
first set.
The who shell variable controls the format of
watch reports.
who (+) The format string for watch messages. The follow-
ing sequences are replaced by the given informa-
tion:
%n The name of the user who logged in/out.
%a The observed action, i.e. `logged on', `logged
off' or `replaced olduser on'.
%l The terminal (tty) on which the user logged
in/out.
%M The full hostname of the remote host, or
`local' if the login/logout was from the local
host.
%m The hostname of the remote host up to the
first `.'. The full name is printed if it is
an IP address or an X Window System display.
%M and %m are available only on systems which
store the remote hostname in /etc/utmp. If unset,
`%n has %a %l from %m.' is used, or `%n has %a
%l.' on systems which don't store the remote host-
name.
wordchars (+)
A list of non-alphanumeric characters to be con-
sidered part of a word by the forward-word, back-
ward-word etc. editor commands. If unset,
`*?_-.[]~=' is used.
ENVIRONMENT
AFSUSER (+)
Equivalent to the afsuser shell variable.
COLUMNS The number of columns in the terminal. See Termi-
nal management.
DISPLAY Used by X Window System (see X(1)). If set, the
shell does not set autologout (q.v.).
EDITOR The pathname to a default editor. See also the
VISUAL environment variable and the run-fg-editor
editor command.
GROUP (+)
Equivalent to the group shell variable.
HOME Equivalent to the home shell variable.
HOST (+)
Initialized to the name of the machine on which
the shell is running, as determined by the geth-
ostname(2) system call.
HOSTTYPE (+)
Initialized to the type of machine on which the
shell is running, as determined at compile time.
This variable is obsolete and will be removed in a
future version.
HPATH (+)
A colon-separated list of directories in which the
run-help editor command looks for command documen-
tation.
LANG Gives the preferred character environment. See
Native Language System support.
LC_CTYPE
If set, only ctype character handling is changed.
See Native Language System support.
LINES The number of lines in the terminal. See Terminal
management.
LS_COLORS
The format of this variable is reminicent of the
termcap(5) file format; a colon-separated list of
expressions of the form "xx=string", where "xx" is
a two-character variable name. The variables with
their associated defaults are:
no 0 Normal (non-filename) text
fi 0 Regular file
di 01;34 Directory
ln 01;36 Symbolic link
pi 33 Named pipe (FIFO)
so 01;35 Socket
bd 01;33 Block device
cd 01;32 Character device
ex 01;32 Executable file
mi (none) Missing file (defaults to fi)
or (none) Orphanned symbolic link (defaults to ln)
lc ^[[ Left code
rc m Right code
ec (none) End code (replaces lc+no+rc)
You only need to include the variables you want to
change from the default.
File names can also be colorized based on filename
extension. This is specified in the LS_COLORS
variable using the syntax "*ext=string". For
example, using ISO 6429 codes, to color all C-lan-
guage source files blue you would specify
"*.c=34". This would color all files ending in .c
in blue (34) color.
Control characters can be written either in
C-style-escaped notation, or in stty-like ^-nota-
tion. The C-style notation adds ^[ for Escape, _
for a normal space characer, and ? for Delete. In
addition, the ^[ escape character can be used to
override the default interpretation of ^[, ^, :
and =.
Each file will be written as <lc> <color-code>
<rc> <filename> <ec>. If the <ec> code is unde-
fined, the sequence <lc> <no> <rc> will be used
instead. This is generally more convenient to
use, but less general. The left, right and end
codes are provided so you don't have to type com-
mon parts over and over again and to support weird
terminals; you will generally not need to change
them at all unless your terminal does not use ISO
6429 color sequences but a different system.
If your terminal does use ISO 6429 color codes,
you can compose the type codes (i.e. all except
the lc, rc, and ec codes) from numerical commands
separated by semicolons. The most common commands
are:
0 to restore default color
1 for brighter colors
4 for underlined text
5 for flashing text
30 for black foreground
31 for red foreground
32 for green foreground
33 for yellow (or brown) foreground
34 for blue foreground
35 for purple foreground
36 for cyan foreground
37 for white (or gray) foreground
40 for black background
41 for red background
42 for green background
43 for yellow (or brown) background
44 for blue background
45 for purple background
46 for cyan background
47 for white (or gray) background
Not all commands will work on all systems or dis-
play devices.
A few terminal programs do not recognize the
default end code properly. If all text gets col-
orized after you do a directory listing, try
changing the no and fi codes from 0 to the numeri-
cal codes for your standard fore- and background
colors.
MACHTYPE (+)
The machine type (microprocessor class or machine
model), as determined at compile time.
NOREBIND (+)
If set, printable characters are not rebound to
self-insert-command. See Native Language System
support.
OSTYPE (+)
The operating system, as determined at compile
time.
PATH A colon-separated list of directories in which to
look for executables. Equivalent to the path
shell variable, but in a different format.
PWD (+) Equivalent to the cwd shell variable, but not syn-
chronized to it; updated only after an actual
directory change.
REMOTEHOST (+)
The host from which the user has logged in
remotely, if this is the case and the shell is
able to determine it. Set only if the shell was so
compiled; see the version shell variable.
SHLVL (+)
Equivalent to the shlvl shell variable.
SYSTYPE (+)
The current system type. (Domain/OS only)
TERM Equivalent to the term shell variable.
TERMCAP The terminal capability string. See Terminal man-
agement.
USER Equivalent to the user shell variable.
VENDOR (+)
The vendor, as determined at compile time.
VISUAL The pathname to a default full-screen editor. See
also the EDITOR environment variable and the run-
fg-editor editor command.
FILES
/etc/csh.cshrc Read first by every shell. ConvexOS,
Stellix and Intel use /etc/cshrc and NeXTs
use /etc/cshrc.std. A/UX, AMIX, Cray and
IRIX have no equivalent in csh(1), but
read this file in tcsh anyway. Solaris
2.x does not have it either, but tcsh
reads /etc/.cshrc. (+)
/etc/csh.login Read by login shells after /etc/csh.cshrc.
ConvexOS, Stellix and Intel use
/etc/login, NeXTs use /etc/login.std,
Solaris 2.x uses /etc/.login and A/UX,
AMIX, Cray and IRIX use /etc/cshrc.
~/.tcshrc (+) Read by every shell after /etc/csh.cshrc
or its equivalent.
~/.cshrc Read by every shell, if ~/.tcshrc doesn't
exist, after /etc/csh.cshrc or its equiva-
lent. This manual uses `~/.tcshrc' to
mean `~/.tcshrc or, if ~/.tcshrc is not
found, ~/.cshrc'.
~/.history Read by login shells after ~/.tcshrc if
savehist is set, but see also histfile.
~/.login Read by login shells after ~/.tcshrc or
~/.history. The shell may be compiled to
read ~/.login before instead of after
~/.tcshrc and ~/.history; see the version
shell variable.
~/.cshdirs (+) Read by login shells after ~/.login if
savedirs is set, but see also dirsfile.
/etc/csh.logout Read by login shells at logout. ConvexOS,
Stellix and Intel use /etc/logout and
NeXTs use /etc/logout.std. A/UX, AMIX,
Cray and IRIX have no equivalent in
csh(1), but read this file in tcsh anyway.
Solaris 2.x does not have it either, but
tcsh reads /etc/.cshrc. (+)
~/.logout Read by login shells at logout after
/etc/csh.logout or its equivalent.
/bin/sh Used to interpret shell scripts not start-
ing with a `#'.
/tmp/sh* Temporary file for `<<'.
/etc/passwd Source of home directories for `~name'
substitutions.
The order in which startup files are read may differ if
the shell was so compiled; see Startup and shutdown and
the version shell variable.
NEW FEATURES (+)
This manual describes tcsh as a single entity, but experi-
enced csh(1) users will want to pay special attention to
tcsh's new features.
A command-line editor, which supports GNU Emacs or
vi(1)-style key bindings. See The command-line editor and
Editor commands.
Programmable, interactive word completion and listing.
See Completion and listing and the complete and uncomplete
builtin commands.
Spelling correction (q.v.) of filenames, commands and
variables.
Editor commands (q.v.) which perform other useful func-
tions in the middle of typed commands, including documen-
tation lookup (run-help), quick editor restarting (run-fg-
editor) and command resolution (which-command).
An enhanced history mechanism. Events in the history list
are time-stamped. See also the history command and its
associated shell variables, the previously undocumented
`#' event specifier and new modifiers under History sub-
stitution, the *-history, history-search-*, i-search-*,
vi-search-* and toggle-literal-history editor commands and
the histlit shell variable.
Enhanced directory parsing and directory stack handling.
See the cd, pushd, popd and dirs commands and their asso-
ciated shell variables, the description of Directory stack
substitution, the dirstack, owd and symlinks shell vari-
ables and the normalize-command and normalize-path editor
commands.
Negation in glob-patterns. See Filename substitution.
New File inquiry operators (q.v.) and a filetest builtin
which uses them.
A variety of Automatic, periodic and timed events (q.v.)
including scheduled events, special aliases, automatic
logout and terminal locking, command timing and watching
for logins and logouts.
Support for the Native Language System (see Native Lan-
guage System support), OS variant features (see OS variant
support and the echo_style shell variable) and system-
dependent file locations (see FILES).
Extensive terminal-managment capabilities. See Terminal
management.
New builtin commands including builtins, hup, ls-F, new-
grp, printenv, which and where (q.v.).
New variables that make useful information easily avail-
able to the shell. See the gid, loginsh, oid, shlvl,
tcsh, tty, uid and version shell variables and the HOST,
REMOTEHOST, VENDOR, OSTYPE and MACHTYPE environment vari-
ables.
A new syntax for including useful information in the
prompt string (see prompt). and special prompts for loops
and spelling correction (see prompt2 and prompt3).
Read-only variables. See Variable substitution.
BUGS
When a suspended command is restarted, the shell prints
the directory it started in if this is different from the
current directory. This can be misleading (i.e. wrong) as
the job may have changed directories internally.
Shell builtin functions are not stoppable/restartable.
Command sequences of the form `a ; b ; c' are also not
handled gracefully when stopping is attempted. If you
suspend `b', the shell will then immediately execute `c'.
This is especially noticeable if this expansion results
from an alias. It suffices to place the sequence of com-
mands in ()'s to force it to a subshell, i.e. `( a ; b ; c
)'.
Control over tty output after processes are started is
primitive; perhaps this will inspire someone to work on a
good virtual terminal interface. In a virtual terminal
interface much more interesting things could be done with
output control.
Alias substitution is most often used to clumsily simulate
shell procedures; shell procedures should be provided
rather than aliases.
Commands within loops are not placed in the history list.
Control structures should be parsed rather than being rec-
ognized as built-in commands. This would allow control
commands to be placed anywhere, to be combined with `|',
and to be used with `&' and `;' metasyntax.
foreach doesn't ignore here documents when looking for its
end.
It should be possible to use the `:' modifiers on the out-
put of command substitutions.
The screen update for lines longer than the screen width
is very poor if the terminal cannot move the cursor up
(i.e. terminal type `dumb').
HPATH and NOREBIND don't need to be environment variables.
Glob-patterns which do not use `?', `*' or `[]' or which
use `{}' or `~' are not negated correctly.
The single-command form of if does output redirection even
if the expression is false and the command is not exe-
cuted.
ls-F includes file identification characters when sorting
filenames and does not handle control characters in file-
names well. It cannot be interrupted.
Report bugs to tcsh-bugs@mx.gw.com, preferably with fixes.
If you want to help maintain and test tcsh, send mail to
listserv@mx.gw.com with the text `subscribe tcsh <your
name>' on a line by itself in the body. You can also `sub-
scribe tcsh-bugs <your name>' to get all bug reports, or
`subscribe tcsh-diffs <your name>' to get the development
list plus diffs for each patchlevel.
THE T IN TCSH
In 1964, DEC produced the PDP-6. The PDP-10 was a later
re-implementation. It was re-christened the DECsystem-10
in 1970 or so when DEC brought out the second model, the
KI10.
TENEX was created at Bolt, Beranek & Newman (a Cambridge,
Mass. think tank) in 1972 as an experiment in demand-paged
virtual memory operating systems. They built a new pager
for the DEC PDP-10 and created the OS to go with it. It
was extremely successful in academia.
In 1975, DEC brought out a new model of the PDP-10, the
KL10; they intended to have only a version of TENEX, which
they had licensed from BBN, for the new box. They called
their version TOPS-20 (their capitalization is trade-
marked). A lot of TOPS-10 users (`The OPerating System
for PDP-10') objected; thus DEC found themselves support-
ing two incompatible systems on the same hardware--but
then there were 6 on the PDP-11!
TENEX, and TOPS-20 to version 3, had command completion
via a user-code-level subroutine library called ULTCMD.
With version 3, DEC moved all that capability and more
into the monitor (`kernel' for you Unix types), accessed
by the COMND% JSYS (`Jump to SYStem' instruction, the
supervisor call mechanism [are my IBM roots also show-
ing?]).
The creator of tcsh was impressed by this feature and sev-
eral others of TENEX and TOPS-20, and created a version of
csh which mimicked them.
LIMITATIONS
Words can be no longer than 1024 characters.
The system limits argument lists to 10240 characters.
The number of arguments to a command which involves file-
name expansion is limited to 1/6th the number of charac-
ters allowed in an argument list.
Command substitutions may substitute no more characters
than are allowed in an argument list.
To detect looping, the shell restricts the number of alias
substitutions on a single line to 20.
SEE ALSO
csh(1), emacs(1), ls(1), newgrp(1), sh(1), setpath(1),
stty(1), su(1), tset(1), vi(1), x(1), access(2),
execve(2), fork(2), killpg(2), pipe(2), setrlimit(2),
sigvec(2), stat(2), umask(2), vfork(2), wait(2), mal-
loc(3), setlocale(3), tty(4), a.out(5), termcap(5), envi-
ron(7), termio(7), Introduction to the C Shell
VERSION
This manual documents tcsh 6.08.00 (Astron) 1998-10-02.
AUTHORS
William Joy
Original author of csh(1)
J.E. Kulp, IIASA, Laxenburg, Austria
Job control and directory stack features
Ken Greer, HP Labs, 1981
File name completion
Mike Ellis, Fairchild, 1983
Command name recognition/completion
Paul Placeway, Ohio State CIS Dept., 1983-1993
Command line editor, prompt routines, new glob syntax
and numerous fixes and speedups
Karl Kleinpaste, CCI 1983-4
Special aliases, directory stack extraction stuff,
login/logout watch, scheduled events, and the idea of
the new prompt format
Rayan Zachariassen, University of Toronto, 1984
ls-F and which builtins and numerous bug fixes, modifi-
cations and speedups
Chris Kingsley, Caltech
Fast storage allocator routines
Chris Grevstad, TRW, 1987
Incorporated 4.3BSD csh into tcsh
Christos S. Zoulas, Cornell U. EE Dept., 1987-94
Ports to HPUX, SVR2 and SVR3, a SysV version of getwd.c,
SHORT_STRINGS support and a new version of sh.glob.c
James J Dempsey, BBN, and Paul Placeway, OSU, 1988
A/UX port
Daniel Long, NNSC, 1988
wordchars
Patrick Wolfe, Kuck and Associates, Inc., 1988
vi mode cleanup
David C Lawrence, Rensselaer Polytechnic Institute, 1989
autolist and ambiguous completion listing
Alec Wolman, DEC, 1989
Newlines in the prompt
Matt Landau, BBN, 1989
~/.tcshrc
Ray Moody, Purdue Physics, 1989
Magic spacebar history expansion
Mordechai ????, Intel, 1989
printprompt() fixes and additions
Kazuhiro Honda, Dept. of Computer Science, Keio
University, 1989
Automatic spelling correction and prompt3
Per Hedeland, Ellemtel, Sweden, 1990-
Various bugfixes, improvements and manual updates
Hans J. Albertsson (Sun Sweden)
ampm, settc and telltc
Michael Bloom
Interrupt handling fixes
Michael Fine, Digital Equipment Corp
Extended key support
Eric Schnoebelen, Convex, 1990
Convex support, lots of csh bug fixes, save and restore
of directory stack
Ron Flax, Apple, 1990
A/UX 2.0 (re)port
Dan Oscarsson, LTH Sweden, 1990
NLS support and simulated NLS support for non NLS sites,
fixes
Johan Widen, SICS Sweden, 1990
shlvl, Mach support, correct-line, 8-bit printing
Matt Day, Sanyo Icon, 1990
POSIX termio support, SysV limit fixes
Jaap Vermeulen, Sequent, 1990-91
Vi mode fixes, expand-line, window change fixes, Symme-
try port
Martin Boyer, Institut de recherche d'Hydro-Quebec, 1991
autolist beeping options, modified the history search to
search for the whole string from the beginning of the
line to the cursor.
Scott Krotz, Motorola, 1991
Minix port
David Dawes, Sydney U. Australia, Physics Dept., 1991
SVR4 job control fixes
Jose Sousa, Interactive Systems Corp., 1991
Extended vi fixes and vi delete command
Marc Horowitz, MIT, 1991
ANSIfication fixes, new exec hashing code, imake fixes,
where
Bruce Sterling Woodcock, sterling@netcom.com, 1991-1995
ETA and Pyramid port, Makefile and lint fixes,
ignoreeof=n addition, and various other portability
changes and bug fixes
Jeff Fink, 1992
complete-word-fwd and complete-word-back
Harry C. Pulley, 1992
Coherent port
Andy Phillips, Mullard Space Science Lab U.K., 1992
VMS-POSIX port
Beto Appleton, IBM Corp., 1992
Walking process group fixes, csh bug fixes, POSIX file
tests, POSIX SIGHUP
Scott Bolte, Cray Computer Corp., 1992
CSOS port
Kaveh R. Ghazi, Rutgers University, 1992
Tek, m88k, Titan and Masscomp ports and fixes. Added
autoconf support.
Mark Linderman, Cornell University, 1992
OS/2 port
Mika Liljeberg, liljeber@kruuna.Helsinki.FI, 1992
Linux port
Tim P. Starrin, NASA Langley Research Center Operations,
1993
Read-only variables
Dave Schweisguth, Yale University, 1993-4
New manpage and tcsh.man2html
Larry Schwimmer, Stanford University, 1993
AFS and HESIOD patches
Luke Mewburn, RMIT University, 1994-6
Enhanced directory printing in prompt, added ellipsis
and rprompt.
Edward Hutchins, Silicon Graphics Inc., 1996
Added implicit cd.
Martin Kraemer, 1997
Ported to Siemens Nixdorf EBCDIC machine
Amol Deshpande, Microsoft, 1997
Ported to WIN32 (Windows/95 and Windows/NT); wrote all
the missing library and message catalog code to inter-
face to Windows.
Taga Nayuta, 1998
Color ls additions.
THANKS TO
Bryan Dunlap, Clayton Elwell, Karl Kleinpaste, Bob Manson,
Steve Romig, Diana Smetters, Bob Sutterfield, Mark Verber,
Elizabeth Zwicky and all the other people at Ohio State
for suggestions and encouragement
All the people on the net, for putting up with, reporting
bugs in, and suggesting new additions to each and every
version
Richard M. Alderson III, for writing the `T in tcsh' sec-
tion
Astron 6.08.00 2 October 1998 1
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