NAME
tcsh - C shell with file name completion and command line
editing
SYNOPSIS
tcsh [-bcdefFimnqstvVxX] [-Dname[=value]] [arg ...]
tcsh -l
DESCRIPTION
tcsh is an enhanced but completely compatible version of the
Berkeley UNIX C shell, csh(1). It is a command language
interpreter usable both as an interactive login shell and a
shell script command processor. It includes a command-line
editor (see The command-line editor), programmable word
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 specified by
invoking the shell with the -l flag as the only argument.
The rest of the flag arguments are interpreted as follows:
-b Forces a ``break'' from option processing, causing any
further shell arguments to be treated as non-option
arguments. The remaining arguments will not be
interpreted as shell options. This may be used to pass
options to a shell script without confusion or possible
subterfuge. The shell will not run a set-user ID script
without this option.
-c Commands are read from the following argument (which
must be present, and must be a single argument), stored
in the command shell variable for reference, and
executed. Any remaining arguments are placed in the
argv shell variable.
-d The shell loads the directory stack from ~/.cshdirs as
described under Startup and shutdown, whether or not it
is a login shell. (+)
-Dname[=value]
Sets the environment variable name to value. (Domain/OS
only) (+)
-e The shell exits if any invoked command terminates
abnormally or yields a non-zero exit status.
-f The shell 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 variable),
then ~/.login, and finally ~/.cshdirs (or the value of the
dirsfile shell variable) (+). The shell may read
/etc/csh.login before instead of after /etc/csh.cshrc, and
~/.login before instead of after ~/.tcshrc or ~/.cshrc and
~/.history, if so compiled; see the version shell variable.
(+)
Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or
~/.cshrc on startup.
Commands like stty(1) and tset(1), which need be run only
once per login, usually go in one's ~/.login file. Users
who need to use the same set of files with both csh(1) and
tcsh can have only a ~/.cshrc which checks for the existence
of the tcsh shell variable (q.v.) before using tcsh-specific
commands, or can have both a ~/.cshrc and a ~/.tcshrc which
sources (see the builtin command) ~/.cshrc. The rest of
this manual uses `~/.tcshrc' to mean `~/.tcshrc or, if
~/.tcshrc is not found, ~/.cshrc'.
In the normal case, the shell begins reading commands from
the terminal, prompting with `> '. (Processing of arguments
and the use of the shell to process files containing command
scripts are described later.) The shell repeatedly reads a
line of command input, breaks it into words, places it on
the command history list, parses it and executes each
command in the line.
One can log out by typing `^D' on an empty line, `logout' or
`login' or via the shell's autologout mechanism (see the
autologout shell variable). When a login shell terminates
it sets the logout shell variable to `normal' or `automatic'
as appropriate, then executes commands from the files
/etc/csh.logout and ~/.logout. The shell may drop DTR on
logout if so compiled; see the version shell variable.
The names of the system login and logout files vary from
system to system for compatibility with different csh(1)
variants; see FILES.
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
commands but which deserve their own treatment. Finally,
Editor commands lists and describes the editor commands
specific to the shell and their default bindings.
The command-line editor (+)
Command-line input can be edited using key sequences much
like those used in GNU Emacs or vi(1). The editor is active
only when the edit shell variable is set, which it is by
default in interactive shells. The bindkey builtin can
display and change key bindings. Emacs-style key bindings
are used by default (unless the shell was compiled
otherwise; see the version shell variable), but bindkey can
change the key bindings to vi-style bindings en masse.
The shell always binds the arrow keys (as defined in the
TERMCAP environment variable) to
down down-history
up up-history
left backward-char
right forward-char
unless doing so would alter another single-character
binding. One can set the arrow key escape sequences to the
empty string with settc to prevent these bindings. The
ANSI/VT100 sequences for arrow keys are always bound.
Other key bindings are, for the most part, what Emacs and
vi(1) users would expect and can easily be displayed by
bindkey, so there is no need to list them here. Likewise,
bindkey can list the editor commands with a short
description of each.
Note that editor commands do not have the same notion of a
``word'' as does the shell. The editor delimits words with
any non-alphanumeric characters not in the shell variable
wordchars, while the shell recognizes only whitespace and
some of the characters with special meanings to it, listed
under Lexical structure.
Completion and listing (+)
The shell is often able to complete words when given a
unique abbreviation. Type part of a word (for example `ls
/usr/lost') and hit the tab key to run the complete-word
editor command. The shell completes the filename
`/usr/lost' to `/usr/lost+found/', replacing the incomplete
word with the complete word in the input buffer. (Note the
terminal `/'; completion adds a `/' to the end of completed
directories and a space to the end of other completed words,
to speed typing and provide a visual indicator of successful
completion. The addsuffix shell variable can be unset to
prevent this.) If no match is found (perhaps
`/usr/lost+found' doesn't exist), the terminal bell rings.
If the word is already complete (perhaps there is a
`/usr/lost' on your system, or perhaps you were thinking too
far ahead and typed the whole thing) a `/' or space is added
to the end if it isn't already there.
Completion works anywhere in the line, not just at the end;
completed text pushes the rest of the line to the right.
Completion in the middle of a word often results in leftover
characters to the right of the cursor which need to be
deleted.
Commands and variables can be completed in much the same
way. For example, typing `em[tab]' would complete `em' to
`emacs' if emacs were the only command on your system
beginning with `em'. Completion can find a command in any
directory in path or if given a full pathname. Typing `echo
$ar[tab]' would complete `$ar' to `$argv' if no other
variable began with `ar'.
The shell parses the input buffer to determine whether the
word you want to complete should be completed as a filename,
command or variable. The first word in the buffer and the
first word following `;', `|', `|&', `&&' or `||' is
considered to be a command. A word beginning with `$' is
considered to be a variable. Anything else is a filename.
An empty line is `completed' as a filename.
You can list the possible completions of a word at any time
by typing `^D' to run the delete-char-or-list-or-eof editor
command. The shell lists the possible completions using the
ls-F builtin (q.v.) and reprints the prompt and unfinished
command line, for example:
> 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
abbreviated with `=' (see Directory stack substitution). For
example,
> ls ~k[^D]
kahn kas kellogg
> ls ~ke[tab]
> ls ~kellogg/
or
> set local = /usr/local
> ls $lo[tab]
> ls $local/[^D]
bin/ etc/ lib/ man/ src/
> ls $local/
Note that variables can also be expanded explicitly with the
expand-variables editor command.
delete-char-or-list-or-eof only lists at the end of the
line; in the middle of a line it deletes the character under
the cursor and on an empty line it logs one out or, if
ignoreeof is set, does nothing. `M-^D', bound to the editor
command list-choices, lists completion possibilities
anywhere on a line, and list-choices (or any one of the
related editor commands which do or don't delete, list
and/or log out, listed under delete-char-or-list-or-eof) can
be bound to `^D' with the bindkey builtin command if so
desired.
The complete-word-fwd and complete-word-back editor commands
(not bound to any keys by default) can be used to cycle up
and down through the list of possible completions, replacing
the current word with the next or previous word in the list.
The shell variable fignore can be set to a list of suffixes
to be ignored by completion. Consider the following:
> ls
Makefile condiments.h~ main.o side.c
README main.c meal side.o
condiments.h main.c~
> set fignore = (.o \~)
> emacs ma[^D]
main.c main.c~ main.o
> emacs ma[tab]
> emacs main.c
`main.c~' and `main.o' are ignored by completion (but not
listing), because they end in suffixes in fignore. Note
that a `\' was needed in front of `~' to prevent it from
being expanded to home as described under Filename
substitution. fignore is ignored if only one completion is
possible.
If the complete shell variable is set to `enhance',
completion 1) ignores case and 2) considers periods, hyphens
and underscores (`.', `-' and `_') to be word separators and
hyphens and underscores to be equivalent. If you had the
following files
comp.lang.c comp.lang.perl comp.std.c++
comp.lang.c++ comp.std.c
and typed `mail -f c.l.c[tab]', it would be completed to
`mail -f comp.lang.c', and ^D would list `comp.lang.c' and
`comp.lang.c++'. `mail -f c..c++[^D]' would list
`comp.lang.c++' and `comp.std.c++'. Typing `rm a--file[^D]'
in the following directory
A_silly_file a-hyphenated-file another_silly_file
would list all three files, because case is ignored and
hyphens and underscores are equivalent. Periods, however,
are not equivalent to hyphens or underscores.
Completion and listing are affected by several other shell
variables: recexact can be set to complete on the shortest
possible unique match, even if more typing might result in a
longer match:
> ls
fodder foo food foonly
> set recexact
> rm fo[tab]
just beeps, because `fo' could expand to `fod' or `foo', but
if we type another `o',
> rm foo[tab]
> rm foo
the completion completes on `foo', even though `food' and
`foonly' also match. autoexpand can be set to run the
expand-history editor command before each completion
attempt, autocorrect can be set to spelling-correct the word
to be completed (see Spelling correction) before each
completion attempt and correct can be set to complete
commands automatically after one hits `return'. matchbeep
can be set to make completion beep or not beep in a variety
of situations, and nobeep can be set to never beep at all.
nostat can be set to a list of directories and/or patterns
which match directories to prevent the completion mechanism
from stat(2)ing those directories. listmax and listmaxrows
can be set to limit the number of items and rows
(respectively) that are listed without asking first.
recognize_only_executables can be set to make the shell list
only executables when listing commands, but it is quite
slow.
Finally, the complete builtin command can be used to tell
the shell how to complete words other than filenames,
commands and variables. Completion and listing do not work
on glob-patterns (see Filename substitution), but the list-
glob and expand-glob editor commands perform equivalent
functions for glob-patterns.
Spelling correction (+)
The shell can sometimes correct the spelling of filenames,
commands and variable names as well as completing and
listing them.
Individual words can be spelling-corrected with the spell-
word editor command (usually bound to M-s and M-S) and the
entire input buffer with spell-line (usually bound to M-$).
The correct shell variable can be set to `cmd' to correct
the command name or `all' to correct the entire line each
time return is typed, and autocorrect can be set to correct
the word to be completed before each completion attempt.
When spelling correction is invoked in any of these ways and
the shell thinks that any part of the command line is
misspelled, it prompts with the corrected line:
> set correct = cmd
> lz /usr/bin
CORRECT>ls /usr/bin (y|n|e|a)?
One can answer `y' or space to execute the corrected line,
`e' to leave the uncorrected command in the input buffer,
`a' to abort the command as if `^C' had been hit, and
anything else to execute the original line unchanged.
Spelling correction recognizes user-defined completions (see
the complete builtin command). If an input word in a
position for which a completion is defined resembles a word
in the completion list, spelling correction registers a
misspelling and suggests the latter word as a correction.
However, if the input word does not match any of the
possible completions for that position, spelling correction
does not register a misspelling.
Like completion, spelling correction works anywhere in the
line, pushing the rest of the line to the right and possibly
leaving extra characters to the right of the cursor.
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
completions.
copy-prev-word (M-^_)
Copies the previous word in the current line into
the input buffer. See also insert-last-word.
dabbrev-expand (M-/)
Expands the current word to the most recent
preceding one for which the current is a leading
substring, wrapping around the history list (once)
if necessary. Repeating dabbrev-expand without any
intervening typing changes to the next previous word
etc., skipping identical matches much like history-
search-backward does.
delete-char (not bound)
Deletes the character under the cursor. See also
delete-char-or-list-or-eof.
delete-char-or-eof (not bound)
Does delete-char if there is a character under the
cursor or end-of-file on an empty line. See also
delete-char-or-list-or-eof.
delete-char-or-list (not bound)
Does delete-char if there is a character under the
cursor or list-choices at the end of the line. See
also delete-char-or-list-or-eof.
delete-char-or-list-or-eof (^D)
Does delete-char if there is a character under the
cursor, list-choices at the end of the line or end-
of-file on an empty line. See also those three
commands, each of which only does a single action,
and delete-char-or-eof, delete-char-or-list and
list-or-eof, each of which does a different two out
of the three.
down-history (down-arrow, ^N)
Like up-history, but steps down, stopping at the
original input line.
end-of-file (not bound)
Signals an end of file, causing the shell to exit
unless the ignoreeof shell variable (q.v.) is set to
prevent this. See also delete-char-or-list-or-eof.
expand-history (M-space)
Expands history substitutions in the current word.
See History substitution. See also magic-space,
toggle-literal-history and the autoexpand shell
variable.
expand-glob (^X-*)
Expands the glob-pattern to the left of the cursor.
See Filename substitution.
expand-line (not bound)
Like expand-history, but expands history
substitutions in each word in the input buffer,
expand-variables (^X-$)
Expands the variable to the left of the cursor. See
Variable substitution.
history-search-backward (M-p, M-P)
Searches backwards through the history list for a
command beginning with the current contents of the
input buffer up to the cursor and copies it into the
input buffer. The search string may be a glob-
pattern (see Filename substitution) containing `*',
`?', `[]' or `{}'. up-history and down-history will
proceed from the appropriate point in the history
list. Emacs mode only. See also history-search-
forward and i-search-back.
history-search-forward (M-n, M-N)
Like history-search-backward, but searches forward.
i-search-back (not bound)
Searches backward like history-search-backward,
copies the first match into the input buffer with
the cursor positioned at the end of the pattern, and
prompts with `bck: ' and the first match. Additional
characters may be typed to extend the search, i-
search-back may be typed to continue searching with
the same pattern, wrapping around the history list
if necessary, (i-search-back must be bound to a
single character for this to work) or one of the
following special characters may be typed:
^W Appends the rest of the word under the
cursor to the search pattern.
char)
delete (or any character bound to backward-
delete-
Undoes the effect of the last character
typed and deletes a character from the
search pattern if appropriate.
^G If the previous search was successful,
aborts the entire search. If not, goes
back to the last successful search.
escape Ends the search, leaving the current
line in the input buffer.
Any other character not bound to self-insert-command
terminates the search, leaving the current line in
the input buffer, and is then interpreted as normal
input. In particular, a carriage return causes the
current line to be executed. Emacs mode only. See
also i-search-fwd and history-search-backward.
i-search-fwd (not bound)
Like i-search-back, but searches forward.
insert-last-word (M-_)
Inserts the last word of the previous input line
(`!$') into the input buffer. See also copy-prev-
word.
list-choices (M-^D)
Lists completion possibilities as described under
Completion and listing. See also delete-char-or-
list-or-eof and list-choices-raw.
list-choices-raw (^X-^D)
Like list-choices, but ignores user-defined
completions.
list-glob (^X-g, ^X-G)
Lists (via the ls-F builtin) matches to the glob-
pattern (see Filename substitution) to the left of
the cursor.
list-or-eof (not bound)
Does list-choices or end-of-file on an empty line.
See also delete-char-or-list-or-eof.
magic-space (not bound)
Expands history substitutions in the current line,
like expand-history, and 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 commands 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 component of the
file name part of the EDITOR or VISUAL environment
variables, or, if neither is set, `ed' or `vi'. If
such a job is found, it is restarted as if `fg %job'
had been typed. This is used to toggle back and
forth between an editor and the shell easily. Some
people bind this command to `^Z' so they can do this
even more easily.
run-help (M-h, M-H)
Searches for documentation on the current command,
using the same notion of `current command' as the
completion routines, and prints it. There is no way
to use a pager; run-help is designed for short help
files. Documentation should be in a file named
command.help, command.1, command.6, command.8 or
command, which should be in one of the directories
listed in the HPATH enviroment variable. If there
is more than one help file only the first is
printed.
self-insert-command (text characters)
In insert mode (the default), inserts the typed
character into the input line after the character
under the cursor. In overwrite mode, replaces the
character under the cursor with the typed character.
The input mode is normally preserved between lines,
but the inputmode shell variable can be set to
`insert' or `overwrite' to put the editor in that
mode at the beginning of each line. See also
overwrite-mode.
sequence-lead-in (arrow prefix, meta prefix, ^X)
Indicates that the following characters are part of
a multi-key sequence. Binding a command to a multi-
key sequence really creates two bindings: the first
character to sequence-lead-in and the whole sequence
to the command. All sequences beginning with a
character bound to sequence-lead-in are effectively
bound to undefined-key unless bound to another
command.
spell-line (M-$)
Attempts to correct the spelling of each word in the
input buffer, like spell-word, but ignores words
whose first character is one of `!', `.', `\', `^',
`-', `*' or `%' 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. Hitting return
ends the search and leaves the last match in the
input buffer. Hitting escape ends the search and
executes the match. vi mode only.
vi-search-fwd (/)
Like vi-search-back, but searches forward.
which-command (M-?)
Does a which (see the description of the builtin
command) on the first word of the input buffer.
Lexical structure
The shell splits input lines into words at blanks and tabs.
The special characters `&', `|', `;', `<', `>', `(', and `)'
and the doubled characters `&&', `||', `<<' and `>>' are
always separate words, whether or not they are surrounded by
whitespace.
When the shell's input is not a terminal, the character `#'
is taken to begin a comment. Each `#' and the rest of the
input line on which it appears is discarded before further
parsing.
A special character (including a blank or tab) may be
prevented from having its special meaning, and possibly made
part of another word, by preceding it with a backslash (`\')
or enclosing it in single (`''), double (`"') or backward
(``') quotes. When not otherwise quoted a newline preceded
by a `\' is equivalent to a blank, but inside quotes this
sequence results in a newline.
Furthermore, all Substitutions (see below) except History
substitution can be prevented by enclosing the strings (or
parts of strings) in which they appear with single quotes or
by quoting the crucial character(s) (e.g. `$' or ``' for
Variable substitution or Command substitution respectively)
with `\'. History substitutions are quoted in the same way
by backslashes but not by single quotes. Strings quoted
with double or backward quotes undergo Variable substitution
and Command substitution, but other substitutions are
prevented.
Text inside single or double quotes becomes a single word
(or part of one). Metacharacters in these strings,
including blanks and tabs, do not form separate words. Only
in one special case (see Command substitution below) can a
double-quoted string yield parts of more than one word;
single-quoted strings never do. Backward quotes are special:
they signal Command substitution (q.v.), which may result in
more than one word.
Quoting complex strings, particularly strings which
themselves contain quoting characters, can be confusing.
Remember that quotes need not be used as they are in human
writing! It may be easier to quote not an entire string, but
only those parts of the string which need quoting, using
different types of quoting to do so if appropriate.
The backslash_quote shell variable (q.v.) can be set to make
backslashes always quote `\', `'', and `"'. (+) This may
make complex quoting tasks easier, but it can cause syntax
errors in csh(1) scripts.
Substitutions
We now describe the various transformations the shell
performs on the input in the order in which they occur. We
note in passing the data structures involved and the
commands and variables which affect them. Remember that
substitutions can be prevented by quoting as described under
Lexical structure.
History substitution
Each command, or ``event'', input from the terminal is saved
in the history list. The previous command is always saved,
and the history shell variable can be set to a number to
save that many commands. The histdup shell variable can be
set to not save duplicate events or consecutive duplicate
events.
Saved commands are numbered sequentially from 1 and stamped
with the time. It is not usually necessary to use event
numbers, but the current event number can be made part of
the prompt by placing an `!' in the prompt shell variable.
The shell actually saves history in expanded and literal
(unexpanded) forms. If the histlit shell variable is set,
commands that display and store history use the literal
form.
The history builtin command can print, store in a file,
restore and clear the history list at any time, and the
savehist and histfile shell variables can be can be set to
store the history list automatically on logout and restore
it on login.
History substitutions introduce words from the history list
into the input stream, making it easy to repeat commands,
repeat arguments of a previous command in the current
command, or fix spelling mistakes in the previous command
with little typing and a high degree of confidence.
History substitutions begin with the character `!'. They may
begin anywhere in the input stream, but they do not nest.
The `!' may be preceded by a `\' to prevent its special
meaning; for convenience, a `!' is passed unchanged when it
is followed by a blank, tab, newline, `=' or `('. History
substitutions also occur when an input line begins with `^'.
This special abbreviation will be described later. The
characters used to signal history substitution (`!' and `^')
can be changed by setting the histchars shell variable. Any
input line which contains a history substitution is printed
before it is executed.
A history substitution may have an ``event specification'',
which indicates the event from which words are to be taken,
a ``word designator'', which selects particular words from
the chosen event, and/or a ``modifier'', which manipulates
the selected words.
An event specification can be
n A number, referring to a particular event
-n An offset, referring to the event n before the
current event
# The current event. This should be used
carefully in csh(1), where there is no check for
recursion. tcsh allows 10 levels of recursion.
(+)
! The previous event (equivalent to `-1')
s The most recent event whose first word begins
with the string s
?s? The most recent event which contains the string
s. The second `?' can be omitted if it is
immediately followed by a newline.
For example, consider this bit of someone's history list:
9 8:30 nroff -man wumpus.man
10 8:31 cp wumpus.man wumpus.man.old
11 8:36 vi wumpus.man
12 8:37 diff wumpus.man.old wumpus.man
The commands are shown with their event numbers and time
stamps. The current event, which we haven't typed in yet,
is event 13. `!11' and `!-2' refer to event 11. `!!'
refers to the previous event, 12. `!!' can be abbreviated
`!' if it is followed by `:' (`:' is described below). `!n'
refers to event 9, which begins with `n'. `!?old?' also
refers to event 12, which contains `old'. Without word
designators or modifiers history references simply expand to
the entire event, so we might type `!cp' to redo the copy
command or `!!|more' if the `diff' output scrolled off the
top of the screen.
History references may be insulated from the surrounding
text with braces if necessary. For example, `!vdoc' would
look for a command beginning with `vdoc', and, in this
example, not find one, but `!{v}doc' would expand
unambiguously to `vi wumpus.mandoc'. Even in braces,
history substitutions do not nest.
(+) While csh(1) expands, for example, `!3d' to event 3 with
the letter `d' appended to it, tcsh expands it to the last
event beginning with `3d'; only completely numeric arguments
are treated as event numbers. This makes it possible to
recall events beginning with numbers. To expand `!3d' as in
csh(1) say `!\3d'.
To select words from an event we can follow the event
specification by a `:' and a designator for the desired
words. The words of an input line are numbered from 0, the
first (usually command) word being 0, the second word (first
argument) being 1, etc. The basic word designators are:
0 The first (command) word
n The nth argument
^ The first argument, equivalent to `1'
$ The last argument
% The word matched by an ?s? search
x-y A range of words
-y Equivalent to `0-y'
* Equivalent to `^-$', but returns nothing if the
event contains only 1 word
x* Equivalent to `x-$'
x- Equivalent to `x*', but omitting the last word
(`$')
Selected words are inserted into the command line separated
by single blanks. For example, the `diff' command in the
previous example might have been typed as `diff !!:1.old
!!:1' (using `:1' to select the first argument from the
previous event) or `diff !-2:2 !-2:1' to select and swap the
arguments from the `cp' command. If we didn't care about the
order of the `diff' we might have said `diff !-2:1-2' or
simply `diff !-2:*'. The `cp' command might have been
written `cp wumpus.man !#:1.old', using `#' to refer to the
current event. `!n:- hurkle.man' would reuse the first two
words from the `nroff' command to say `nroff -man
hurkle.man'.
The `:' separating the event specification from the word
designator can be omitted if the argument selector begins
with a `^', `$', `*', `%' or `-'. For example, our `diff'
command might have been `diff !!^.old !!^' or, equivalently,
`diff !!$.old !!$'. However, if `!!' is abbreviated `!', an
argument selector beginning with `-' will be interpreted as
an event specification.
A history reference may have a word designator but no event
specification. It then references the previous command.
Continuing our `diff' example, we could have said simply
`diff !^.old !^' or, to get the arguments in the opposite
order, just `diff !*'.
The word or words in a history reference can be edited, or
``modified'', by following it with one or more modifiers,
each preceded by a `:':
h Remove a trailing pathname component, leaving
the head.
t Remove all leading pathname components, leaving
the tail.
r Remove a filename extension `.xxx', leaving the
root name.
e Remove all but the extension.
u Uppercase the first lowercase letter.
l Lowercase the first uppercase letter.
s/l/r/ Substitute l for r. l is simply a string like
r, not a regular expression as in the eponymous
ed(1) command. Any character may be used as the
delimiter in place of `/'; a `\' can be used to
quote the delimiter inside l and r. The
character `&' in the r is replaced by l; `\'
also quotes `&'. If l is empty (``''), the l
from a previous substitution or the s from a
previous `?s?' event specification is used. The
trailing delimiter may be omitted if it is
immediately followed by a newline.
& Repeat the previous substitution.
g Apply the following modifier once to each word.
a (+) Apply the following modifier as many times as
possible to a single word. `a' and `g' can be
used together to apply a modifier globally. In
the current implementation, using the `a' and
`s' modifiers together can lead to an infinite
loop. For example, `:as/f/ff/' will never
terminate. This behavior might change in the
future.
p Print the new command line but do not execute
it.
q Quote the substituted words, preventing further
substitutions.
x Like q, but break into words at blanks, tabs and
newlines.
Modifiers are applied only to the first modifiable word
(unless `g' is used). It is an error for no word to be
modifiable.
For example, the `diff' command might have been written as
`diff wumpus.man.old !#^:r', using `:r' to remove `.old'
from the first argument on the same line (`!#^'). We could
say `echo hello out there', then `echo !*:u' to capitalize
`hello', `echo !*:au' to say it out loud, or `echo !*:agu'
to really shout. We might follow `mail -s "I forgot my
password" rot' with `!:s/rot/root' to correct the spelling
of `root' (but see Spelling correction for a different
approach).
There is a special abbreviation for substitutions. `^',
when it is the first character on an input line, is
equivalent to `!:s^'. Thus we might have said `^rot^root'
to make the spelling correction in the previous example.
This is the only history substitution which does not
explicitly begin with `!'.
(+) In csh as such, only one modifier may be applied to each
history or variable expansion. In tcsh, more than one may be
used, for example
% 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 reference, the argument list is left
untouched.
Thus if the alias for `ls' were `ls -l' the command `ls
/usr' would become `ls -l /usr', the argument list here
being undisturbed. If the alias for `lookup' were `grep !^
/etc/passwd' then `lookup bill' would become `grep bill
/etc/passwd'. Aliases can be used to introduce parser
metasyntax. For example, `alias print 'pr \!* | lpr''
defines a ``command'' (`print') which pr(1)s its arguments
to the line printer.
Alias substitution is repeated until the first word of the
command has no alias. If an alias substitution does not
change the first word (as in the previous example) it is
flagged to prevent a loop. Other loops are detected and
cause an error.
Some aliases are referred to by the shell; see Special
aliases.
Variable substitution
The shell maintains a list of variables, each of which has
as value a list of zero or more words. The values of shell
variables can be 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; attempting
to do so will cause an error. Once made read-only, a
variable cannot be made writable, so `set -r' should be used
with caution. Environment variables cannot be made read-
only.
Some variables are set by the shell or referred to by it.
For instance, the argv variable is an image of the shell's
argument list, and words of this variable's value are
referred to in special ways. Some of the variables referred
to by the shell are toggles; the shell does not care what
their value is, only whether they are set or not. For
instance, the verbose variable is a toggle which causes
command input to be echoed. The -v command line option sets
this variable. Special shell variables lists all variables
which are referred to by the shell.
Other operations treat variables numerically. The `@'
command permits numeric calculations to be performed and the
result assigned to a variable. Variable values are,
however, always represented as (zero or more) strings. For
the purposes of numeric operations, the null string is
considered to be zero, and the second and subsequent words
of multiword values are ignored.
After the input line is aliased and parsed, and before each
command is executed, variable substitution is performed
keyed by `$' characters. This expansion can be prevented by
preceding the `$' with a `\' except within `"'s where it
always occurs, and within `''s where it never occurs.
Strings quoted by ``' are interpreted later (see Command
substitution below) so `$' substitution does not occur there
until later, if at all. A `$' is passed unchanged if
followed by a blank, tab, or end-of-line.
Input/output redirections are recognized before variable
expansion, and are variable expanded separately. Otherwise,
the command name and entire argument list are expanded
together. It is thus possible for the first (command) word
(to this point) to generate more than one word, the first of
which becomes the command name, and the rest of which become
arguments.
Unless enclosed in `"' or given the `:q' modifier the
results of variable substitution may eventually be command
and filename substituted. Within `"', a variable whose
value consists of multiple words expands to a (portion of a)
single word, with the words of the variable's value
separated by blanks. When the `:q' modifier is applied to a
substitution the variable will expand to multiple words with
each word separated by a blank and quoted to prevent later
command or filename substitution.
The following metasequences are provided for introducing
variable values into the shell input. Except as noted, it
is an error to reference a variable which is not set.
$name
${name} Substitutes the words of the value of variable name,
each separated by a blank. Braces insulate name
from following characters which would otherwise be
part of it. Shell variables have names consisting
of up to 20 letters and digits starting with a
letter. The underscore character is considered a
letter. If name is not a shell variable, but is set
in the environment, then that value is returned (but
`:' modifiers and the other forms given below are
not available in this case).
$name[selector]
${name[selector]}
Substitutes only the selected words from the value
of name. The selector is subjected to `$'
substitution and may consist of a single number or
two numbers separated by a `-'. The first word of a
variable's value is numbered `1'. If the first
number of a range is omitted it defaults to `1'. If
the last member of a range is omitted it defaults to
`$#name'. The selector `*' selects all words. It
is not an error for a range to be empty if the
second argument is omitted or in range.
$0 Substitutes the name of the file from which command
input is being read. An error occurs if the name is
not known.
$number
${number}
Equivalent to `$argv[number]'.
$* Equivalent to `$argv', which is equivalent to
`$argv[*]'.
The `:' modifiers described under History substitution,
except for `:p', can be applied to the substitutions above.
More than one may be used. (+) Braces may be needed to
insulate a variable substitution from a literal colon just
as with History substitution (q.v.); any modifiers must
appear within the braces.
The following substitutions can not be modified with `:'
modifiers.
$?name
${?name}
Substitutes the string `1' if name is set, `0' if it
is not.
$?0 Substitutes `1' if the current input filename is
known, `0' if it is not. Always `0' in interactive
shells.
$#name
${#name}
Substitutes the number of words in name.
$# Equivalent to `$#argv'. (+)
$%name
${%name}
Substitutes the number of characters in name. (+)
$%number
${%number}
Substitutes the number of characters in
$argv[number]. (+)
$? Equivalent to `$status'. (+)
$$ Substitutes the (decimal) process number of the
(parent) shell.
$! Substitutes the (decimal) process number of the last
background process started by this shell.
$< Substitutes a line from the standard input, with no
further interpretation thereafter. It can be used
to read from the keyboard in a shell script. (+)
While csh always quotes $<, as if it were equivalent
to `$<:q', tcsh does not. Furthermore, when tcsh is
waiting for a line to be typed the user may type an
interrupt to interrupt the sequence into which the
line is to be substituted, but csh does not allow
this.
The editor command expand-variables, normally bound to `^X-
$', can be used to interactively expand individual
variables.
Command, filename and directory stack substitution
The remaining substitutions are applied selectively to the
arguments of builtin commands. This means that portions of
expressions which are not evaluated are not subjected to
these expansions. For commands which are not internal to
the shell, the command name is substituted separately from
the argument list. This occurs very late, after input-
output redirection is performed, and in a child of the main
shell.
Command substitution
Command substitution is indicated by a command enclosed in
``'. The output from such a command is broken into separate
words at blanks, tabs and newlines, and null words are
discarded. The output is variable and command substituted
and put in place of the original string.
Command substitutions inside double quotes (`"') retain
blanks and tabs; only newlines force new words. The single
final newline does not force a new word in any case. It is
thus possible for a command substitution to yield only part
of a word, even if the command outputs a complete line.
Filename substitution
If a word contains any of the characters `*', `?', `[' or
`{' or begins with the character `~' it is a candidate for
filename substitution, also known as ``globbing''. This word
is then regarded as a pattern (``glob-pattern''), and
replaced with an alphabetically sorted list of file names
which match the pattern.
In matching filenames, the character `.' at the beginning of
a filename or immediately following a `/', as well as the
character `/' must be matched explicitly. The character `*'
matches any string of characters, including the null string.
The character `?' matches any single character. The
sequence `[...]' matches any one of the characters enclosed.
Within `[...]', a pair of characters separated by `-'
matches any character lexically between the two.
(+) Some glob-patterns can be negated: The sequence
`[^...]' matches any single character not specified by the
characters and/or ranges of characters in the braces.
An entire glob-pattern can also be negated with `^':
> echo *
bang crash crunch ouch
> echo ^cr*
bang ouch
Glob-patterns which do not use `?', `*', or `[]' or which
use `{}' or `~' (below) are not negated correctly.
The metanotation `a{b,c,d}e' is a shorthand for `abe ace
ade'. Left-to-right order is preserved:
`/usr/source/s1/{oldls,ls}.c' expands to
`/usr/source/s1/oldls.c /usr/source/s1/ls.c'. The results of
matches are sorted separately at a low level to preserve
this order: `../{memo,*box}' might expand to `../memo
../box ../mbox'. (Note that `memo' was not sorted with the
results of matching `*box'.) It is not an error when this
construct expands to files which do not exist, but it is
possible to get an error from a command to which the
expanded list is passed. This construct may be nested. As
a special case the words `{', `}' and `{}' are passed
undisturbed.
The character `~' at the beginning of a filename refers to
home directories. Standing alone, i.e. `~', it expands to
the invoker's home directory as reflected in the value of
the home shell variable. When followed by a name consisting
of letters, digits and `-' characters the shell searches for
a user with that name and substitutes their home directory;
thus `~ken' might expand to `/usr/ken' and `~ken/chmach' to
`/usr/ken/chmach'. If the character `~' is followed by a
character other than a letter or `/' or appears elsewhere
than at the beginning of a word, it is left undisturbed. A
command like `setenv MANPATH
/usr/man:/usr/local/man:~/lib/man' does not, therefore, do
home directory substitution as one might hope.
It is an error for a glob-pattern containing `*', `?', `['
or `~', with or without `^', not to match any files.
However, only one pattern in a list of glob-patterns must
match a file (so that, e.g., `rm *.a *.c *.o' would fail
only if there were no files in the current directory ending
in `.a', `.c', or `.o'), and if the nonomatch shell variable
is set a pattern (or list of patterns) which matches nothing
is left unchanged rather than causing an error.
The noglob shell variable can be set to prevent filename
substitution, and the expand-glob editor command, normally
bound to `^X-*', can be used to interactively expand
individual filename substitutions.
Directory stack substitution (+)
The directory stack is a list of directories, numbered from
zero, used by the pushd, popd and dirs builtin commands
(q.v.). dirs can print, store in a file, restore and clear
the directory stack at any time, and the savedirs and
dirsfile shell variables can be set to store the directory
stack automatically on logout and restore it on login. The
dirstack shell variable can be examined to see the directory
stack and set to put arbitrary directories into the
directory stack.
The character `=' followed by one or more digits expands to
an entry in the directory stack. The special case `=-'
expands to the last directory in the stack. For example,
> dirs -v
0 /usr/bin
1 /usr/spool/uucp
2 /usr/accts/sys
> echo =1
/usr/spool/uucp
> echo =0/calendar
/usr/bin/calendar
> echo =-
/usr/accts/sys
The noglob and nonomatch shell variables and the expand-glob
editor command apply to directory stack as well as filename
substitutions.
Other substitutions (+)
There are several more transformations involving filenames,
not strictly related to the above but mentioned here for
completeness. Any filename may be expanded to a full path
when the symlinks variable (q.v.) is set to `expand'.
Quoting prevents this expansion, and the normalize-path
editor command does it on demand. The normalize-command
editor command expands commands in PATH into full paths on
demand. Finally, cd and pushd interpret `-' as the old
working directory (equivalent to the shell variable owd).
This is not a substitution at all, but an abbreviation
recognized only by those commands. Nonetheless, it too can
be prevented by quoting.
Commands
The next three sections describe how the shell executes
commands and deals with their input and output.
Simple commands, pipelines and sequences
A simple command is a sequence of words, the first of which
specifies the command to be executed. A series of simple
commands joined by `|' characters forms a pipeline. The
output of each command in a pipeline is connected to the
input of the next.
Simple commands and pipelines may be joined into sequences
with `;', and will be executed sequentially. Commands and
pipelines can also be joined into sequences with `||' or
`&&', indicating, as in the C language, that the second is
to be executed only if the first fails or succeeds
respectively.
A simple command, pipeline or sequence may be placed in
parentheses, `()', to form a simple command, which may in
turn be a component of a pipeline or sequence. A command,
pipeline or sequence can be executed without waiting for it
to terminate by following it with an `&'.
Builtin and non-builtin command execution
Builtin commands are executed within the shell. If any
component of a pipeline except the last is a builtin
command, the pipeline is executed in a subshell.
Parenthesized commands are always executed in a subshell.
(cd; pwd); pwd
thus prints the home directory, leaving you where you were
(printing this after the home directory), while
cd; pwd
leaves you in the home directory. Parenthesized commands
are most often used to prevent cd from affecting the current
shell.
When a command to be executed is found not to be a builtin
command the shell attempts to execute the command via
execve(2). Each word in the variable path names a directory
in which the shell will look for the command. If it is
given neither a -c nor a -t option, the shell hashes the
names in these directories into an internal table so that it
will only try an execve(2) in a directory if there is a
possibility that the command resides there. This greatly
speeds command location when a large number of directories
are present in the search path. If this mechanism has been
turned off (via unhash), if the shell was given a -c or -t
argument or in any case for each directory component of path
which does not begin with a `/', the shell concatenates the
current working directory with the given command name to
form a path name of a file which it then attempts to
execute.
If the file has execute permissions but is not an executable
to the system (i.e. it is neither an executable binary nor a
script which specifies its interpreter), then it is assumed
to be a file containing shell commands and a new shell is
spawned to read it. The shell special alias may be set to
specify an interpreter other than the shell itself.
On systems which do not understand the `#!' script
interpreter convention the shell may be compiled to emulate
it; see the version shell variable. If so, the shell checks
the first line of the file to see if it is of the form
`#!interpreter arg ...'. If it is, the shell starts
interpreter with the given args and feeds the file to it on
standard input.
Input/output
The standard input and standard output of a command may be
redirected with the following syntax:
< name Open file name (which is first variable, command and
filename expanded) as the standard input.
<< word Read the shell input up to a line which is identical
to word. word is not subjected to variable, filename
or command substitution, and each input line is
compared to word before any substitutions are done
on this input line. Unless a quoting `\', `"', `'
or ``' appears in word variable and command
substitution is performed on the intervening lines,
allowing `\' to quote `$', `\' and ``'. Commands
which are substituted have all blanks, tabs, and
newlines preserved, except for the final newline
which is dropped. The resultant text is placed in
an anonymous temporary file which is given to the
command as standard input.
> name
>! name
>& name
>&! name
The file name is used as standard output. If the
file does not exist then it is created; if the file
exists, its is truncated, its previous contents
being lost.
If the shell variable noclobber is set, then the
file must not exist or be a character special file
(e.g. a terminal or `/dev/null') or an error
results. This helps prevent accidental destruction
of files. In this case the `!' forms can be used to
suppress this check.
The forms involving `&' route the diagnostic output
into the specified file as well as the standard
output. name is expanded in the same way as `<'
input filenames are.
>> name
>>& name
>>! name
>>&! name
Like `>', but appends output to the end of name. If
the shell variable noclobber is set, then it is an
error for the file not to exist, unless one of the
`!' forms is given.
A command receives the environment in which the shell was
invoked as modified by the input-output parameters and the
presence of the command in a pipeline. Thus, unlike some
previous shells, commands run from a file of shell commands
have no access to the text of the commands by default;
rather they receive the original standard input of the
shell. The `<<' mechanism should be used to present inline
data. This permits shell command scripts to function as
components of pipelines and allows the shell to block read
its input. Note that the default standard input for a
command run detached is not the empty file /dev/null, but
the original standard input of the shell. If this is a
terminal and if the process attempts to read from the
terminal, then the process will block and the user will be
notified (see Jobs).
Diagnostic output may be directed through a pipe with the
standard output. Simply use the form `|&' rather than just
`|'.
The shell cannot presently redirect diagnostic output
without also redirecting standard output, but `(command >
output-file) >& error-file' is often an acceptable
workaround. Either output-file or error-file may be
`/dev/tty' to send output to the terminal.
Features
Having described how the shell accepts, parses and executes
command lines, we now turn to a variety of its useful
features.
Control flow
The shell contains a number of commands which can be used to
regulate the flow of control in command files (shell
scripts) and (in limited but useful ways) from terminal
input. These commands all operate by forcing the shell to
reread or skip in its input and, due to the implementation,
restrict the placement of some of the commands.
The foreach, switch, and while statements, as well as the
if-then-else form of the if statement, require that the
major keywords appear in a single simple command on an input
line as shown below.
If the shell's input is not seekable, the shell buffers up
input whenever a loop is being read and performs seeks in
this internal buffer to accomplish the rereading implied by
the loop. (To the extent that this allows, backward gotos
will succeed on non-seekable inputs.)
Expressions
The if, while and exit builtin commands use expressions with
a common syntax. The expressions can include any of the
operators described in the next three sections. Note that
the @ builtin command (q.v.) has its own separate syntax.
Logical, arithmetical and comparison operators
These operators are similar to those of C and have the same
precedence. They include
|| && | ^ & == != =~ !~ <= >=
< > << >> + - * / % ! ~ ( )
Here the precedence increases to the right, `==' `!=' `=~'
and `!~', `<=' `>=' `<' and `>', `<<' and `>>', `+' and `-',
`*' `/' and `%' being, in groups, at the same level. The
`==' `!=' `=~' and `!~' operators compare their arguments as
strings; all others operate on numbers. The operators `=~'
and `!~' are like `!=' and `==' except that the right hand
side is a glob-pattern (see Filename substitution) against
which the left hand operand is matched. This reduces the
need for use of the switch builtin command in shell scripts
when all that is really needed is pattern matching.
Strings which begin with `0' are considered octal numbers.
Null or missing arguments are considered `0'. The results
of all expressions are strings, which represent decimal
numbers. It is important to note that no two components of
an expression can appear in the same word; except when
adjacent to components of expressions which are
syntactically significant to the parser (`&' `|' `<' `>' `('
`)') they should be surrounded by spaces.
Command exit status
Commands can be executed in expressions and their exit
status returned by enclosing them in braces (`{}'). Remember
that the braces should be separated from the words of the
command by spaces. Command executions succeed, returning
true, i.e. `1', if the command exits with status 0,
otherwise they fail, returning false, i.e. `0'. If more
detailed 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 (+)
L Applies subsequent operators in a multiple-operator
test to a symbolic link rather than to the file to
which the link points (+) *
file is command and filename expanded and then tested to see
if it has the specified relationship to the real user. If
file does not exist or is inaccessible or, for the operators
indicated by `*', if the specified file type does not exist
on the current system, then all enquiries return false, i.e.
`0'.
These operators may be combined for conciseness: `-xy file'
is equivalent to `-x file && -y file'. (+) For example,
`-fx' is true (returns `1') for plain executable files, but
not for directories.
L may be used in a multiple-operator test to apply
subsequent operators to a symbolic link rather than to the
file to which the link points. For example, `-lLo' is true
for links owned by the invoking user. Lr, Lw and Lx are
always true for links and false for non-links. L has a
different meaning when it is the last operator in a
multiple-operator test; see below.
It is possible but not useful, and sometimes misleading, to
combine operators which expect file to be a file with
operators which do not, (e.g. X and t). Following L with a
non-file operator can lead to particularly strange results.
Other operators return other information, i.e. not just `0'
or `1'. (+) They have the same format as before; op may be
one of
A Last file access time, as the number of seconds
since the epoch
A: Like A, but in timestamp format, e.g. `Fri May
14 16:36:10 1993'
M Last file modification time
M: Like M, but in timestamp format
C Last inode modification time
C: Like C, but in timestamp format
D Device number
I Inode number
F Composite file identifier, in the form
device:inode
L The name of the file pointed to by a symbolic
link
N Number of (hard) links
P Permissions, in octal, without leading zero
P: Like P, with leading zero
Pmode Equivalent to `-P file & mode', e.g. `-P22 file'
returns `22' if file is writable by group and
other, `20' if by group only, and `0' if by
neither
Pmode: Like Pmode:, with leading zero
U Numeric userid
U: Username, or the numeric userid if the username
is unknown
G Numeric groupid
G: Groupname, or the numeric groupid if the
groupname is unknown
Z Size, in bytes
Only one of these operators may appear in a multiple-
operator test, and it must be the last. Note that L has a
different meaning at the end of and elsewhere in a
multiple-operator test. Because `0' is a valid return value
for many of these operators, they do not return `0' when
they fail: most return `-1', and F returns `:'.
If the shell is compiled with POSIX defined (see the version
shell variable), the result of a file inquiry is based on
the permission bits of the file and not on the result of the
access(2) system call. For example, if one tests a file
with -w whose permissions would ordinarily allow writing but
which is on a file system mounted read-only, the test will
succeed in a POSIX shell but fail in a non-POSIX shell.
File inquiry operators can also be evaluated with the
filetest builtin command (q.v.) (+).
Jobs
The shell associates a job with each pipeline. It keeps a
table of current jobs, printed by the jobs command, and
assigns them small integer numbers. When a job is started
asynchronously with `&', the shell prints a line which looks
like
[1] 1234
indicating that the job which was started asynchronously was
job number 1 and had one (top-level) process, whose process
id was 1234.
If you are running a job and wish to do something else you
may hit the suspend key (usually `^Z'), which sends a STOP
signal to the current job. The shell will then normally
indicate that the job has been `Suspended' and print another
prompt. If the listjobs shell variable is set, all jobs
will be listed like the jobs builtin command; if it is set
to `long' the listing will be in long format, like `jobs
-l'. You can then manipulate the state of the suspended
job. You can put it in the ``background'' with the bg
command or run some other commands and eventually bring the
job back into the ``foreground'' with fg. (See also the
run-fg-editor editor command.) A `^Z' takes effect
immediately and is like an interrupt in that pending output
and unread input are discarded when it is typed. The wait
builtin command causes the shell to wait for all background
jobs to complete.
The `^]' key sends a delayed suspend signal, which does not
generate a STOP signal until a program attempts to read(2)
it, to the current job. This can usefully be typed ahead
when you have prepared some commands for a job which you
wish to stop after it has read them. The `^Y' key performs
this function in csh(1); in tcsh, `^Y' is an editing
command. (+)
A job being run in the background stops if it tries to read
from the terminal. Background jobs are normally allowed to
produce output, but this can be disabled by giving the
command `stty tostop'. If you set this tty option, then
background jobs will stop when they try to produce output
like they do when they try to read input.
There are several ways to refer to jobs in the shell. The
character `%' introduces a job name. If you wish to refer
to job number 1, you can name it as `%1'. Just naming a job
brings it to the foreground; thus `%1' is a synonym for `fg
%1', bringing job 1 back into the foreground. Similarly,
saying `%1 &' resumes job 1 in the background, just like `bg
%1'. A job can also be named by an unambigous prefix of the
string typed in to start it: `%ex' would normally restart a
suspended ex(1) job, if there were only one suspended job
whose name began with the string `ex'. It is also possible
to say `%?string' to specify a job whose text contains
string, if there is only one such job.
The shell maintains a notion of the current and previous
jobs. In output pertaining to jobs, the current job is
marked with a `+' and the previous job with a `-'. The
abbreviations `%+', `%', and (by analogy with the syntax of
the history mechanism) `%%' all refer to the current job,
and `%-' refers to the previous job.
The job control mechanism requires that the stty(1) option
`new' be set on some systems. It is an artifact from a
`new' implementation of the tty driver which allows
generation of interrupt characters from the keyboard to tell
jobs to stop. See stty(1) and the setty builtin command for
details on setting options in the new tty driver.
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 terminated.
Automatic, periodic and timed events (+)
There are various ways to run commands and take other
actions automatically at various times in the ``life cycle''
of the shell. They are summarized here, and described in
detail under the appropriate Builtin commands, Special shell
variables and Special aliases.
The sched builtin command puts commands in a scheduled-event
list, to be executed by the shell at a given time.
The beepcmd, cwdcmd, periodic and precmd Special aliases can
be set, respectively, to execute commands when the shell
wants to ring the bell, when the working directory changes,
every tperiod minutes and before each prompt.
The autologout shell variable can be set to log out or lock
the shell after a given number of minutes of inactivity.
The mail shell variable can be set to check for new mail
periodically.
The printexitvalue shell variable can be set to print the
exit status of commands which exit with a status other than
zero.
The rmstar shell variable can be set to ask the user, when
`rm *' is typed, if that is really what was meant.
The time shell variable can be set to execute the time
builtin command after the completion of any process that
takes more than a given number of CPU seconds.
The watch and who shell variables can be set to report when
selected users log in or out, and the log builtin command
reports on those users at any time.
Native Language System support (+)
The shell is eight bit clean (if so compiled; see the
version shell variable) and thus supports character sets
needing this capability. NLS support differs depending on
whether or not the shell was compiled to use the system's
NLS (again, see version). In either case, 7-bit ASCII is
the default for character classification (e.g. which
characters are printable) and sorting, and changing the LANG
or LC_CTYPE environment variables causes a check for
possible changes in these respects.
When using the system's NLS, the setlocale(3) function is
called to determine appropriate character classification and
sorting. This function typically examines the LANG and
LC_CTYPE environment variables; refer to the system
documentation for further details. When not using the
system's NLS, the shell simulates it by assuming that the
ISO 8859-1 character set is used whenever either of the LANG
and LC_CTYPE variables are set, regardless of their values.
Sorting is not affected for the simulated NLS.
In addition, with both real and simulated NLS, all printable
characters in the range \200-\377, i.e. those that have M-
char bindings, are automatically rebound to self-insert-
command. The corresponding binding for the escape-char
sequence, if any, is left alone. These characters are not
rebound if the NOREBIND environment variable is set. This
may be useful for the simulated NLS or a primitive real NLS
which assumes full ISO 8859-1. Otherwise, all M-char
bindings in the range \240-\377 are effectively undone.
Explicitly rebinding the relevant keys with bindkey is of
course still possible.
Unknown characters (i.e. those that are neither printable
nor control characters) are printed in the format \nnn. If
the tty is not in 8 bit mode, other 8 bit characters are
printed by converting them to ASCII and using standout mode.
The shell never changes the 7/8 bit mode of the tty and
tracks user-initiated changes of 7/8 bit mode. NLS users
(or, for that matter, those who want to use a meta key) may
need to explicitly set the tty in 8 bit mode through the
appropriate stty(1) command in, e.g., the ~/.login file.
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 current
environment, rootnode changes the rootnode and ver changes
the systype.
Under Mach, setpath is equivalent to Mach's setpath(1).
Under Masscomp/RTU, universe sets the universe.
Under Convex/OS, warp prints or sets the universe.
The VENDOR, OSTYPE and MACHTYPE environment variables
indicate respectively the vendor, operating system and
machine type (microprocessor class or machine model) of the
system on which the shell thinks it is running. These are
particularly useful when sharing one's home directory
between several types of machines; one can, for example,
set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .)
in one's ~/.login and put executables compiled for each
machine in the appropriate directory.
The version shell variable indicates what options were
chosen when the shell was compiled.
Note also the newgrp builtin, the afsuser and echo_style
shell variables and the system-dependent locations of the
shell's input files (see FILES).
Signal handling
Login shells ignore interrupts when reading the file
~/.logout. The shell ignores quit signals unless started
with -q. Login shells catch the terminate signal, but non-
login shells inherit the terminate behavior from their
parents. Other signals have the values which the shell
inherited from its parent.
In shell scripts, the shell's handling of interrupt and
terminate signals can be controlled with onintr, and its
handling of hangups can be controlled with hup and nohup.
The shell exits on a hangup (see also the logout shell
variable). By default, the shell's children do too, but the
shell does not send them a hangup when it exits. hup
arranges for the shell to send a hangup to a child when it
exits, and nohup sets a child to ignore hangups.
Terminal management (+)
The shell uses three different sets of terminal (``tty'')
modes: `edit', used when editing, `quote', used when
quoting literal characters, and `execute', used when
executing commands. The shell holds some settings in each
mode constant, so commands which leave the tty in a confused
state do not interfere with the shell. The shell also
matches changes in the speed and padding of the tty. The
list of tty modes that are kept constant can be examined and
modified with the setty builtin. Note that although the
editor uses CBREAK mode (or its equivalent), it takes
typed-ahead characters anyway.
The echotc, settc and telltc commands can be used to
manipulate and debug terminal capabilities from the command
line.
On systems that support SIGWINCH or SIGWINDOW, the shell
adapts to window resizing automatically and adjusts the
environment variables LINES and COLUMNS if set. If the
environment variable TERMCAP contains li# and co# fields,
the shell adjusts them to reflect the new window size.
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
The first form prints the values of all shell
variables. The second form sets the specified name
to the value of expr. If expr contains `<', `>',
`&' or `' then at least that part of expr must be
placed within `()'. The third form assigns the
value of expr to the index'th argument of name.
Both name and its index'th component must already
exist.
expr may contain the operators `*', `+', etc. as in
C. The space separating the name from the
assignment operator is optional. Spaces are,
however, mandatory in separating components of expr
which would otherwise be single words.
Special postfix `++' and `--' operators increment
and decrement name respectively, e.g. `@ i++'.
Note that the syntax of expr has nothing to do with
that described under Expressions.
alias [name [wordlist]]
Without arguments, prints all aliases. With name,
prints the alias for name. With name and wordlist,
assigns wordlist as the alias of name. wordlist is
command and filename substituted. name may not be
`alias' or `unalias'. See also the unalias builtin
command.
alloc Shows the amount of dynamic memory acquired, broken
down into used and free memory. With an argument
shows the number of free and used blocks in each
size category. The categories start at size 8 and
double at each step. This command's output may vary
across system types, 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
description of each.
-d Binds all keys to the standard bindings for the
default editor.
-e Binds all keys to the standard GNU Emacs-like
bindings.
-v Binds all keys to the standard vi(1)-like
bindings.
-a Lists or changes key-bindings in the alternative
key map. This is the key map used in vi command
mode.
-b key is interpreted as a control character
written ^character (e.g. `^A') or C-character
(e.g. `C-A'), a meta character written M-
character (e.g. `M-A'), a function key written
F-string (e.g. `F-string'), or an extended
prefix key written X-character (e.g. `X-A').
-k key is interpreted as a symbolic arrow key name,
which may be one of `down', `up', `left' or
`right'.
-r Removes key's binding. Be careful: `bindkey -r'
does not bind key to self-insert-command (q.v.),
it unbinds key completely.
-c command is interpreted as a builtin or external
command instead of an editor command.
-s command is taken as a literal string and treated
as terminal input when key is typed. Bound keys
in command are themselves reinterpreted, and
this continues for ten levels of interpretation.
-- Forces a break from option processing, so the
next word is taken as key even if it begins with
'-'.
-u (or any invalid option)
Prints a usage message.
key may be a single character or a string. If a
command is bound to a string, the first character of
the string is bound to sequence-lead-in and the
entire string is bound to the command.
Control characters in key can be literal (they can
be typed by preceding them with the editor command
quoted-insert, normally bound to `^V') or written
caret-character style, e.g. `^A'. Delete is written
`^?' (caret-question mark). key and command can
contain backslashed escape sequences (in the style
of System V echo(1)) as follows:
\a Bell
\b Backspace
\e Escape
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
\v Vertical tab
\nnn The ASCII character corresponding to the
octal number nnn
`\' nullifies the special meaning of the following
character, if it has any, notably `\' and `^'.
break Causes execution to resume after the end of the
nearest enclosing foreach or while. The remaining
commands on the current line are executed. Multi-
level breaks are thus possible by writing them all
on one line.
breaksw Causes a break from a switch, resuming after the
endsw.
builtins (+)
Prints the names of all builtin commands.
bye (+) A synonym for the logout builtin command. Available
only if the shell was so compiled; see the version
shell variable.
case label:
A label in a switch statement as discussed below.
cd [-p] [-l] [-n|-v] [name]
If a directory name is given, changes the shell's
working directory to name. If not, changes to home.
If name is `-' it is interpreted as the previous
working directory (see Other substitutions). (+) If
name is not a subdirectory of the current directory
(and does not begin with `/', `./' or `../'), each
component of the variable cdpath is checked to see
if it has a subdirectory name. Finally, if all else
fails but name is a shell variable whose value
begins with `/', 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. (+)
chdir A synonym for the cd builtin command.
(+)
complete [command [word/pattern/list[:select]/[[suffix]/] ...]]
Without arguments, lists all completions. With
command, lists completions for command. With
command and word etc., defines completions.
command may be a full command name or a glob-pattern
(see Filename substitution). It can begin with `-'
to indicate that completion should be used only when
command is ambiguous.
word specifies which word relative to the current
word is to be completed, and may be one of the
following:
c Current-word completion. pattern is a
glob-pattern which must match the beginning
of the current word on the command line.
pattern is ignored when completing the
current word.
C Like c, but includes pattern when completing
the current word.
n Next-word completion. pattern is a glob-
pattern which must match the beginning of
the previous word on the command line.
N Like n, but must match the beginning of the
word two before the current word.
p Position-dependent completion. pattern is a
numeric range, with the same syntax used to
index shell variables, which must include
the current word.
list, the list of possible completions, may be one
of the following:
a Aliases
b Bindings (editor commands)
c Commands (builtin or external commands)
C External commands which begin with the
supplied path prefix
d Directories
D Directories which begin with the
supplied path prefix
e Environment variables
f Filenames
F Filenames which begin with the supplied
path prefix
g Groupnames
j Jobs
l Limits
n Nothing
s Shell variables
S Signals
t Plain (``text'') files
T Plain (``text'') files which begin with
the supplied path prefix
v Any variables
u Usernames
x Like n, but prints select when list-
choices is used.
X Completions
$var Words from the variable var
(...) Words from the given list
`...` Words from the output of command
select is an optional glob-pattern. If given, only
words from list which match select are considered
and the fignore shell variable is ignored. The last
three types of completion may not have a select
pattern, and x uses select as an explanatory message
when the list-choices editor command is used.
suffix is a single character to be appended to a
successful completion. If null, no character is
appended. If omitted (in which case the fourth
delimiter can also be omitted), a slash is appended
to directories and a space to other words.
Now for some examples. Some commands take only
directories as arguments, so there's no point
completing plain files.
> complete cd 'p/1/d/'
completes only the first word following `cd' (`p/1')
with a directory. p-type completion can also be
used to narrow down command completion:
> co[^D]
complete compress
> complete -co* 'p/0/(compress)/'
> co[^D]
> compress
This completion completes commands (words in
position 0, `p/0') which begin with `co' (thus
matching `co*') to `compress' (the only word in the
list). The leading `-' indicates that this
completion is to be used only with ambiguous
commands.
> complete find 'n/-user/u/'
is an example of n-type completion. Any word
following `find' and immediately following `-user'
is completed from the list of users.
> complete cc 'c/-I/d/'
demonstrates c-type completion. Any word following
`cc' and beginning with `-I' is completed as a
directory. `-I' is not taken as part of the
directory because we used lowercase c.
Different lists are useful with different commands.
> complete alias 'p/1/a/'
> complete man 'p/*/c/'
> complete set 'p/1/s/'
> complete true 'p/1/x:Truth has no options./'
These complete words following `alias' with aliases,
`man' with commands, and `set' with shell variables.
`true' doesn't have any options, so x does nothing
when completion is attempted and prints `Truth has
no options.' when completion choices are listed.
Note that the man example, and several other
examples below, could just as well have used 'c/*'
or 'n/*' as 'p/*'.
Words can be completed from a variable evaluated at
completion time,
> complete ftp 'p/1/$hostnames/'
> set hostnames = (rtfm.mit.edu
tesla.ee.cornell.edu)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu
> ftp [^C]
> set hostnames = (rtfm.mit.edu
tesla.ee.cornell.edu uunet.uu.net)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net
or from a command run at completion time:
> complete kill 'p/*/`ps | awk \{print\ \$1\}`/'
> kill -9 [^D]
23113 23377 23380 23406 23429 23529 23530 PID
Note that the complete command does not itself quote
its arguments, so the braces, space and `$' in
`{print $1}' must be quoted explicitly.
One command can have multiple completions:
> complete dbx 'p/2/(core)/' 'p/*/c/'
completes the second argument to `dbx' with the word
`core' and all other arguments with commands. Note
that the positional completion is specified before
the next-word completion. Since completions are
evaluated from left to right, if the next-word
completion were specified first it would always
match and the positional completion would never be
executed. This is a common mistake when defining a
completion.
The select pattern is useful when a command takes
only files with particular forms as arguments. For
example,
> 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'
completion. Of course, one could still type excluded
names manually or override the completion mechanism
using the complete-word-raw or list-choices-raw
editor commands (q.v.).
The `C', `D', `F' and `T' lists are like `c', `d',
`f' and `t' respectively, but they use the select
argument in a different way: to restrict completion
to files beginning with a particular path prefix.
For example, the Elm mail program uses `=' as an
abbreviation for one's mail directory. One might use
> 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 completion) and
completes anything not otherwise completed to a
directory. Whew.
Remember that programmed completions are ignored if
the word being completed is a tilde substitution
(beginning with `~') or a variable (beginning with
`$'). complete is an experimental feature, and the
syntax may change in future versions of the shell.
See also the uncomplete builtin command.
continue
Continues execution of the nearest enclosing while
or foreach. The rest of the commands on the current
line are executed.
default:
Labels the default case in a switch statement. It
should come after all case labels.
dirs [-l] [-n|-v]
dirs -S|-L [filename] (+)
dirs -c (+)
The first form prints the directory stack. The top
of the stack is at the left and the first directory
in the stack is the current directory. With -l, `~'
or `~name' in the output is expanded explicitly to
home or the pathname of the home directory for user
name. (+) With -n, entries are wrapped before they
reach the edge of the screen. (+) With -v, entries
are printed one per line, preceded by their stack
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
presumably a directory stack file saved by the -S
option or the savedirs mechanism. In either case,
dirsfile is used if filename is not given and
~/.cshdirs is used if dirsfile is unset.
Note that login shells do the equivalent of `dirs
-L' on startup and, if savedirs is set, `dirs -S'
before exiting. Because only ~/.tcshrc is normally
sourced before ~/.cshdirs, dirsfile should be set in
~/.tcshrc rather than ~/.login.
The last form clears the directory stack.
echo [-n] word ...
Writes each word to the shell's standard output,
separated by spaces and terminated with a newline.
The echo_style shell variable may be set to emulate
(or not) the flags and escape sequences of the BSD
and/or System V versions of echo; see echo(1).
echotc [-sv] arg ... (+)
Exercises the terminal capabilities (see termcap(5))
in args. For example, 'echotc home' sends the
cursor to the home position, 'echotc cm 3 10' sends
it to column 3 and row 10, and 'echotc ts 0; echo
"This is a test."; echotc fs' prints "This is a
test." in the status line.
If arg is 'baud', 'cols', 'lines', 'meta' or 'tabs',
prints the value of that capability ("yes" or "no"
indicating that the terminal does or does not have
that capability). One might use this to make the
output from a shell script less verbose on slow
terminals, or limit command output to the number of
lines on the screen:
> set history=`echotc lines`
> @ history--
Termcap strings may contain wildcards which will not
echo correctly. One should use double quotes when
setting a shell variable to a terminal capability
string, as in the following example that places the
date in the status line:
> set tosl="`echotc ts 0`"
> set frsl="`echotc fs`"
> echo -n "$tosl";date; echo -n "$frsl"
With -s, nonexistent capabilities return the empty
string rather than causing an error. With -v,
messages are verbose.
else
end
endif
endsw See the description of the foreach, if, switch, and
while statements below.
eval arg ...
Treats the arguments as input to the shell and
executes the resulting command(s) in the context of
the current shell. This is usually used to execute
commands generated as the result of command or
variable substitution, 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
specified expr (an expression, as described under
Expressions) or, without expr, with the value of the
status variable.
fg [%job ...]
Brings the specified jobs (or, without arguments,
the current job) into the foreground, continuing
each if it is stopped. job may be a number, a
string, `', `%', `+' or `-' as described under Jobs.
See also the run-fg-editor editor command.
filetest -op file ... (+)
Applies op (which is a file inquiry operator as
described under File inquiry operators) to each file
and returns the results as a space-separated list.
foreach name (wordlist))
...
end Successively sets the variable name to each member
of wordlist and executes the sequence of commands
between this command and the matching end. (Both
foreach and end must appear alone on separate
lines.) The builtin command continue may be used to
continue the loop prematurely and the builtin
command break to terminate it prematurely. When
this command is read from the terminal, the loop is
read once prompting with `foreach? ' (or prompt2)
before any statements in the loop are executed. If
you make a mistake typing in a loop at the terminal
you can rub it out.
getspath (+)
Prints the system execution path. (TCF only)
getxvers (+)
Prints the experimental version prefix. (TCF only)
glob wordlist
Like echo, but no `\' escapes are recognized and
words are delimited by null characters in the
output. Useful for programs which wish to use the
shell to filename expand a list of words.
goto word
word is filename and command-substituted to yield a
string of the form `label'. The shell rewinds its
input as much as possible, searches for a line of
the form `label:', possibly preceded by blanks or
tabs, and continues execution after that line.
hashstat
Prints a statistics line indicating how effective
the internal hash table has been at locating
commands (and avoiding exec's). An exec is attempted
for each component of the path where the hash
function indicates a possible hit, and in each
component which does not begin with a `/'.
On machines without vfork(2), prints only the number and
size of hash buckets. history [-hr] [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 and with time-stamps 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
presumably a history list saved by the -S option or
the savehist mechanism, to the history list. -M is
like -L, but the contents of filename are merged
into the history list and sorted by timestamp. In
either case, histfile is used if filename is not
given and ~/.history is used if histfile is unset.
`history -L' is exactly like 'source -h' except that
it does not require a filename.
Note that login shells do the equivalent of `history
-L' on startup and, if savehist is set, `history -S'
before exiting. Because only ~/.tcshrc is normally
sourced before ~/.history, histfile should be set in
~/.tcshrc rather than ~/.login.
If histlit is set, the first and second forms print
and save the literal (unexpanded) form of the
history list.
The last form clears the history list.
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
Expressions) evaluates true, then command is
executed. Variable substitution on command happens
early, at the same time it does for the rest of the
if command. command must be a simple command, not
an alias, a pipeline, a command list or a
parenthesized command list, but it may have
arguments. Input/output redirection occurs even if
expr is false and command is thus not executed; this
is a bug.
if (expr)) then
...
else if (expr2)) then
...
else
...
endif If the specified expr is true then the commands to
the first else are executed; otherwise if expr2 is
true then the commands to the second else are
executed, etc. Any number of else-if pairs are
possible; only one endif is needed. The else part
is likewise optional. (The words else and endif
must appear at the beginning of input lines; the if
must appear alone on its input line or after an
else.)
inlib shared-library ... (+)
Adds each shared-library to the current environment.
There is no way to remove a shared library.
(Domain/OS only)
jobs [-l]
Lists the active jobs. With -l, lists process IDs in
addition to the normal information. On TCF systems,
prints the site on which each job is executing.
kill [-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 process 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
maximum-use is given, then the current limit is
printed; if no resource is given, then all
limitations are given. If the -h flag is given, the
hard limits are used instead of the current limits.
The hard limits impose a ceiling on the values of
the current limits. Only the super-user may raise
the hard limits, but a user may lower or raise the
current limits within the legal range.
Controllable resources currently include cputime
(the maximum number of cpu-seconds to be used by
each process), filesize (the largest single file
which can be created), datasize (the maximum growth
of the data+stack region via sbrk(2) beyond the end
of the program text), stacksize (the maximum size of
the automatically-extended stack region),
coredumpsize (the size of the largest core dump that
will be created), and memoryuse, the maximum amount
of physical memory a process may have allocated to
it at a given time.
maximum-use may be given as a (floating point or
integer) number followed by a scale factor. For all
limits other than cputime the default scale is `k'
or `kilobytes' (1024 bytes); a scale factor of `m'
or `megabytes' may also be used. For cputime the
default scaling is `seconds', while `m' for minutes
or `h' for hours, or a time of the form `mm:ss'
giving minutes and seconds may be used.
For both resource names and scale factors,
unambiguous prefixes of the names suffice.
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 listing
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 dependent
(HP/UX only)
: Network special (HP/UX only)
If the listlinks shell variable is set, symbolic
links are identified in more detail (only, of
course, on systems which have them):
@ Symbolic link to a non-directory
> Symbolic link to a directory
& Symbolic link to nowhere
listlinks also slows down ls-F and causes partitions
holding files pointed to by symbolic links to be
mounted.
If the listflags shell variable is set to `x', `a'
or `A', or any combination thereof (e.g. `xA'), they
are used as flags to ls-F, making it act like `ls
-xF', `ls -Fa', `ls -FA' or a combination (e.g. `ls
-FxA'). On machines where `ls -C' is not the
default, ls-F acts like `ls -CF', unless listflags
contains an `x', in which case it acts like `ls
-xF'. ls-F passes its arguments to ls(1) if it is
given any switches, so `alias ls ls-F' generally
does the right thing. ls-F includes file
identification characters when sorting filenames;
this is a bug.
migrate [-site] pid|%jobid ... (+)
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 process
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
number, 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 commands
in simple if statements apply.
nohup [command]
With command, runs command such that it will ignore
hangup signals. Note that commands may set their
own response to hangups, overriding nohup. Without
an argument (allowed only in a shell script), causes
the shell to ignore hangups for the remainder of the
script. See also Signal handling and the hup
builtin command.
notify [%job ...]
Causes the shell to notify the user asynchronously
when the status of any of the specified jobs (or,
without %job, the current job) changes, instead of
waiting until the next prompt as is usual. job may
be a number, a string, `', `%', `+' or `-' as
described under Jobs. See also the notify shell
variable.
onintr [-|label]
Controls the action of the shell on interrupts.
Without arguments, restores the default action of
the shell on interrupts, which is to terminate shell
scripts or to return to the terminal command input
level. With `-', causes all interrupts to be
ignored. With label, causes the shell to execute a
`goto label' when an interrupt is received or a
child process terminates because it was interrupted.
onintr is ignored if the shell is running detached
and in system startup files (see FILES), where
interrupts are disabled anyway.
popd [-p] [-l] [-n|-v] [+n]
Without arguments, pops the directory stack and
returns to the new top directory. With a number
`+n', discards the n'th entry in the stack.
Finally, all forms of popd print the final directory
stack, just like dirs. The pushdsilent shell
variable can be set to prevent this and the -p flag
can be given to override pushdsilent. The -l, -n
and -v flags have the same effect on popd as on
dirs. (+)
printenv [name] (+)
Prints the names and values of all environment
variables or, with name, the value of the
environment variable name.
pushd [-p] [-l] [-n|-v] [name|+n]
Without arguments, exchanges the top two elements of
the directory stack. If pushdtohome is set, pushd
without arguments does `pushd ~', like cd. (+) With
name, pushes the current working directory onto the
directory stack and changes to name. If name is `-'
it is interpreted as the previous working directory
(see Filename substitution). (+) If dunique is set,
pushd removes any instances of name from the stack
before pushing it onto the stack. (+) With a number
`+n', rotates the nth element of the directory stack
around to be the top element and changes to it. If
dextract is set, however, `pushd +n' extracts the
nth directory, pushes it onto the top of the stack
and changes to it. (+)
Finally, all forms of pushd print the final
directory stack, just like dirs. The pushdsilent
shell variable can be set to prevent this and the -p
flag can be given to override pushdsilent. The -l,
-n and -v flags have the same effect on pushd as on
dirs. (+)
rehash Causes the internal hash table of the contents of
the directories in the path variable to be
recomputed. This is needed if 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 system 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 possible
to miss the exact time when the command is to be
run, but an overdue command will execute at the next
prompt. A command which comes due while the shell
is waiting for user input is executed immediately.
However, normal operation of an already-running
command will not be interrupted so that a
scheduled-event list element may be run.
This mechanism is similar to, but not the same as,
the at(1) command on some Unix systems. Its major
disadvantage is that it may not run a command at
exactly the specified time. Its major advantage is
that because sched runs directly from the shell, it
has access to shell variables and other structures.
This provides a mechanism for changing one's working
environment based on the time of day.
set
set name ...
set name=word ...
set name=(wordlist)) ...
set name[index]=word ...
set -r (+)
set -r name ... (+)
set -r name=word ... (+)
set -r name=(wordlist)) ... (+)
The first form of the command prints the value of
all shell variables. Variables which contain more
than a single word print as a parenthesized word
list. The second form sets name to the null string.
The third form sets name to the single word. The
fourth form sets name to the list of words in
wordlist. In all cases the value is command and
filename expanded. 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 and ninth forms are the
same as the third and fourth forms, but make name
read-only at the same time.
These arguments can be repeated to set and/or make
read-only multiple variables in a single set
command. Note, however, that variable expansion
happens for all arguments before any setting occurs.
Note also that `=' can be adjacent to both name and
word or separated from both by whitespace, but
cannot be adjacent to only one or the other. See
also the unset builtin command.
setenv [name [value]]
Without arguments, prints the names and values of
all environment variables. 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
capability cap (as defined in termcap(5)) has the
value value. No sanity checking is done. Concept
terminal users may have to `settc xn no' to get
proper wrapping at the rightmost column.
setty [-d|-q|-x] [-a] [[+|-]mode] (+)
Controls which tty modes (see Terminal management)
the shell does not allow to change. -d, -q or -x
tells setty to act on the `edit', `quote' or
`execute' set of tty modes respectively; without -d,
-q or -x, `execute' is used.
Without other arguments, setty lists the modes in
the chosen set which are fixed on (`+mode') or off
(`-mode'). The available modes, and thus the
display, vary from system to system. With -a, lists
all tty modes in the chosen set whether or not they
are fixed. With +mode, -mode or mode, fixes mode on
or off or removes control from mode in the chosen
set. For example, `setty +echok echoe' fixes
`echok' mode on and allows commands to turn `echoe'
mode on or off, both when the shell is executing
commands.
setxvers [string] (+)
Set the experimental version prefix to string, or
removes it if string is omitted. (TCF only)
shift [variable]
Without arguments, discards argv[1] and shifts the
members of argv to the left. It is an error for argv
not to be set or to have less than one word as
value. With variable, performs the same function on
variable.
source [-h] name [args ...]
The shell reads and executes commands from name.
The commands are not placed on the history list. If
any args are given, they are placed in argv. (+)
source commands may be nested; if they are nested
too deeply the shell may run out of file
descriptors. An error in a source at any level
terminates all nested source commands. With -h,
commands are placed on the history list instead of
being executed, much like `history -L'.
stop %job|pid ...
Stops the specified jobs or processes which are
executing in the background. job may be a number, a
string, `', `%', `+' or `-' as described under Jobs.
There is no default job; 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. Otherwise
control may fall through case labels and default
labels as in C. If no label matches and there is no
default, execution continues after the endsw.
telltc (+)
Lists the values of all terminal capabilities (see
termcap(5)).
time [command]
Executes command (which must be a simple command,
not an alias, a pipeline, a command list or a
parenthesized command list) and prints a time
summary as described under the time variable. If
necessary, an extra shell is created to print the
time statistic when the command completes. Without
command, prints a time summary for the current shell
and its children.
umask [value]
Sets the file creation mask to value, which is given
in octal. Common values for the mask are 002,
giving all access to the group and read and execute
access to others, and 022, giving read and execute
access to the group and others. Without value,
prints the current file creation mask.
unalias pattern
Removes all aliases whose names match pattern.
`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
compiled; see the version shell variable.
where command (+)
Reports all known instances of command, including
aliases, builtins and executables in path.
which command (+)
Displays the command that will be executed by the
shell after substitutions, path searching, etc. The
builtin command is just like which(1), but it
correctly reports tcsh aliases and builtins and is
10 to 100 times faster. See also the which-command
editor command.
while (expr))
...
end Executes the commands between the while and the
matching end while expr (an expression, as described
under Expressions) evaluates non-zero. while and
end must appear alone on their input lines. break
and continue may be used to terminate or continue
the loop prematurely. If the input is a terminal,
the user is prompted the first time through the loop
as with foreach.
Special aliases (+)
If set, each of these aliases executes automatically at the
indicated time. They are all initially undefined.
beepcmd Runs when the shell wants to ring the terminal bell.
cwdcmd Runs after every change of working directory. For
example, if the user is working on an X window
system using xterm(1) and a re-parenting window
manager that supports title bars such as twm(1) and
does
> alias cwdcmd 'echo -n "^[]2;${HOST}:$cwd ^G"'
then the shell will change the title of the running
xterm(1) to be the name of the host, a 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
convenient means for checking on common but
infrequent changes such as new mail. For example, if
one does
> set tperiod = 30
> alias periodic checknews
then the checknews(1) program runs every 30 minutes.
If periodic is set but tperiod is unset or set to 0,
periodic behaves like precmd.
precmd Runs just before each prompt is printed. For
example, if one does
> alias precmd date
then date(1) runs just before the shell prompts for
each command. There are no limits on what precmd
can be set to do, but discretion should be used.
shell Specifies the interpreter for executable scripts
which do not themselves specify an interpreter. The
first word should be a full path name to the desired
interpreter (e.g. `/bin/csh' or
`/usr/local/bin/tcsh').
Special shell variables
The variables described in this section have special meaning
to the shell.
The shell sets addsuffix, argv, autologout, 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
automatically 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 format.
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 ambiguous
completion. If set to `ambiguous', possibilities
are listed only when no new characters are added by
completion.
autologout (+)
The first word is the number of minutes of
inactivity before automatic logout. The optional
second word is the number of minutes of inactivity
before automatic locking. When the shell
automatically logs out, it prints `auto-logout',
sets the variable logout to `automatic' and exits.
When the shell automatically locks, the user is
required to enter his password to continue working.
Five incorrect attempts result in automatic logout.
Set to `60' (automatic logout after 60 minutes, and
no locking) by default in login and superuser
shells, but not if the shell thinks it is running
under a window system (i.e. the DISPLAY environment
variable is set), the tty is a pseudo-tty (pty) or
the shell was not so compiled (see the version shell
variable). See also the afsuser and logout shell
variables.
backslash_quote (+)
If set, backslashes (`\') always quote `\', `'', and
`"'. This may make complex quoting tasks easier, but
it can cause syntax errors in csh(1) scripts.
cdpath A list of directories in which cd should search for
subdirectories if they aren't found in the current
directory.
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', commands
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.
dunique (+)
If set, pushd removes any instances of name from the
stack before pushing it onto the stack.
echo If set, each command with its arguments is echoed
just before it is executed. For non-builtin
commands all expansions occur before echoing.
Builtin commands are echoed before command and
filename substitution, 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 backslashed
escape sequences; the default.
none Recognize neither.
Set by default to `both'. 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
completion.
filec In tcsh, completion is always used and this variable
is ignored. If set in csh, filename completion 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
history list. If set to `all' only unique history
events are entered in the history list. If set to
`prev' and the last history event is the same as the
current command, then the current command is not
entered in the history. If set to `erase' and the
same event is found in the history list, that old
event gets erased and the current one gets inserted.
histfile (+)
The default location in which `history -S' and
`history -L' look for a history file. If unset,
~/.history is used. histfile is useful when sharing
the same home directory between different machines,
or when saving separate histories on different
terminals. Because only ~/.tcshrc is normally
sourced before ~/.history, histfile should be set in
~/.tcshrc rather than ~/.login.
histlit (+)
If set, builtin and editor commands and the savehist
mechanism use the literal (unexpanded) form of lines
in the history list. See also the toggle-literal-
history editor command.
history The first word indicates the number of history
events to save. The optional second word (+)
indicates the format in which history is printed; if
not given, `%h\t%T\t%R\n' is used. The format
sequences are described below under prompt; note the
variable meaning of `%R'. Set to `100' by default.
home Initialized to the home directory of the invoker.
The filename expansion of `~' refers to this
variable.
ignoreeof
If set to the empty string or `0' and the input
device is a terminal, the end-of-file command
(usually generated by the user by typing `^D' on an
empty line) causes the shell to print `Use "exit" to
leave tcsh.' instead of exiting. This prevents the
shell from accidentally being killed. If set to a
number n, the shell ignores n - 1 consecutive end-
of-files and exits on the nth. (+) If unset, `1' is
used, i.e. the shell exits on a single `^D'.
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 suspended.
If set to `long', the listing is in long format.
listlinks (+)
If set, the ls-F builtin command shows the type of
file to which each symbolic link points.
listmax (+)
The maximum number of items which the list-choices
editor command will list without asking first.
listmaxrows (+)
The maximum number of rows of items which the list-
choices editor command will list without asking
first.
loginsh (+)
Set by the shell if it is a login shell. Setting or
unsetting it within a shell has no effect. See also
shlvl.
logout (+)
Set by the shell to `normal' before a normal logout,
`automatic' before an automatic logout, and `hangup'
if the shell was killed by a hangup signal (see
Signal handling). See also the autologout shell
variable.
mail 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 multiple files,
`You have new mail in name.') if the filesize is
greater than zero in size and has a modification
time greater than its access time.
If you are in a login shell, then no mail file is
reported unless it has been modified after the time
the shell has started up, 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
appropriate. This functionality is provided
primarily for those systems which store mail in this
manner, such as the Andrew Mail System.
If the first word of mail is numeric it is taken as
a different mail checking interval, in seconds.
Under very rare circumstances, the shell may report
`You have mail.' instead of `You have new mail.'
matchbeep (+)
If set to `never', completion never beeps. If set
to `nomatch', it beeps only when there is no match.
If set to `ambiguous, it beeps when there are
multiple matches. If set to `notunique', it beeps
when there is one exact and other longer matches.
If unset, `ambiguous' is used.
nobeep (+)
If set, beeping is completely disabled. See also
visiblebell.
noclobber
If set, restrictions are placed on output
redirection to insure that files are not
accidentally destroyed and that `>>' redirections
refer to existing files, as described in the
Input/output section.
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 version
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 causing
an error. It is still an error for the substitution
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 operation. This
is usually used to exclude directories which take
too much time to stat(2), for example /afs.
notify If set, the shell announces job completions
asynchronously. The default is to present job
completions just before printing a prompt.
oid (+) The user's real organization ID. (Domain/OS only)
owd (+) The old working directory, equivalent to the `-'
used by cd and pushd. See also the cwd and dirstack
shell variables.
path A list of directories in which to look for
executable commands. A null word specifies the
current directory. If there is no path variable
then only full path names will execute. path is set
by the shell at startup from the PATH environment
variable or, if PATH does not exist, to a system-
dependent default something like `(/usr/local/bin
/usr/bsd /bin /usr/bin .)'. The shell may put `.'
first or last in path or omit it entirely depending
on how it was compiled; see the version shell
variable. A shell which is given neither the -c nor
the -t option hashes the contents of the directories
in path after reading ~/.tcshrc and each time path
is reset. If one adds a new command to a directory
in path while the shell is active, one may need to
do a rehash for the shell to find it.
printexitvalue (+)
If set and an interactive program exits with a non-
zero status, the shell prints `Exit status'.
prompt The string which is printed before reading each
command from the terminal. prompt may include any
of the following formatting sequences (+), which are
replaced by the given information:
%/ The current working directory.
%~ The current working directory, but with one's
home directory represented by `~' and other
users' home directories represented by `~user'
as per Filename substitution. `~user'
substitution happens only if the shell has
already used `~user' in a pathname in the
current session.
%c[[0]n], %.[[0]n]
The trailing component of the current working
directory, or n trailing components if a digit n
is given. If n begins with `0', the number of
skipped components precede the trailing
component(s) in the format `/<skipped>trailing'.
If the ellipsis shell variable is set, skipped
components are represented by an ellipsis so the
whole becomes `...trailing'. `~' substitution
is done as in `%~' above, but the `~' component
is ignored when counting trailing components.
%C Like %c, but without `~' substitution.
%h, %!, !
The current history event number.
%M The full hostname.
%m The hostname up to the first `.'.
%S (%s)
Start (stop) standout mode.
%B (%b)
Start (stop) boldfacing mode.
%U (%u)
Start (stop) underline mode.
%t, %@
The time of day in 12-hour AM/PM format.
%T Like `%t', but in 24-hour format (but see the
ampm shell variable).
%p The `precise' time of day in 12-hour AM/PM
format, with seconds.
%P Like `%p', but in 24-hour format (but see the
ampm shell variable).
\c c is parsed as in bindkey.
^c c is parsed as in bindkey.
%% A single `%'.
%n The user name.
%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.
%# `>' (or the first character of the promptchars
shell variable) for normal users, `#' (or the
second character of promptchars) for the
superuser.
%{string%}
Includes string as a literal escape sequence.
It should be used only to change terminal
attributes and should not move the cursor
location. This cannot be the last sequence in
prompt.
%? The return code of the command executed just
before the prompt.
%R In prompt2, the status of the parser. In
prompt3, the corrected string. In history, the
history string.
`%B', `%S', `%U' and `%{string%}' are available 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 foreach
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)? ' in interactive shells.
promptchars (+)
If set (to a two-character string), the `%#'
formatting sequence in the prompt shell variable is
replaced with the first character for normal users
and the second character for the superuser.
pushdtohome (+)
If set, pushd without arguments does `pushd ~', like
cd.
pushdsilent (+)
If set, pushd and popd do not print the directory
stack.
recexact (+)
If set, completion completes on an exact match even
if a longer match is possible.
recognize_only_executables (+)
If set, command listing displays only files in the
path that are executable. Slow.
rmstar (+)
If set, the user is prompted before `rm *' is
executed.
savedirs (+)
If set, the shell does `dirs -S' before exiting.
savehist
If set, the shell does `history -S' before exiting.
If the first word is set to a number, at most that
many lines are saved. (The number 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 replacing 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 status
`0'.
symlinks (+)
Can be set to several different values to control
symbolic link (`symlink') resolution:
If set to `chase', whenever the current directory
changes to a directory containing a symbolic link,
it is expanded to the real name of the directory to
which the link points. This does not work for the
user's home directory; this is a bug.
If set to `ignore', the shell tries to construct a
current directory relative to the current directory
before the link was crossed. This means that 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 symbolic
links by actually expanding arguments which look
like path names. This affects any command, not just
builtins. Unfortunately, this does not work for
hard-to-recognize filenames, such as those embedded
in command options. Expansion may be prevented by
quoting. While this setting is usually the most
convenient, it is sometimes misleading and sometimes
confusing when it fails to recognize an argument
which should be expanded. A compromise is to use
`ignore' and use the editor command normalize-path
(bound by default to ^X-n) when necessary.
Some examples are in order. First, let's set up some
play directories:
> cd /tmp
> mkdir from from/src to
> ln -s from/src to/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 following
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
version number (see tcsh), origin, release date,
vendor, operating system and machine (see VENDOR,
OSTYPE and MACHTYPE) and a comma-separated list of
options which were set at compile time. Options
which are set by default in the distribution are
noted.
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
~/.history.
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 emulated
when executing shell scripts
ng The newgrp builtin is available
rh The shell attempts to set the REMOTEHOST
environment variable
afs The shell verifies your password with the
kerberos server if local authentication fails.
The afsuser shell variable or the AFSUSER
environment variable override your local
username if set.
An administrator may enter additional strings to
indicate differences in the local version.
visiblebell (+)
If set, a screen flash is used rather than the
audible bell. See also nobeep.
watch (+)
A list of user/terminal pairs to watch for logins
and logouts. If either the user is `any' all
terminals are watched for the given user and vice
versa. Setting watch to `(any any)' watches all
users and terminals. For example,
set watch = (george ttyd1 any console $user any)
reports activity of the user `george' on ttyd1, any
user on the console, and oneself (or a trespasser)
on any terminal.
Logins and logouts are checked every 10 minutes by
default, but the first word of watch can be set to a
number to check every so many minutes. For example,
set watch = (1 any any)
reports any login/logout once every minute. For the
impatient, the log builtin command triggers a watch
report at any time. All current logins are reported
(as with the log builtin) when watch is first set.
The who shell variable controls the format of watch
reports.
who (+) The format string for watch messages. The following
sequences are replaced by the given information:
%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 hostname.
wordchars (+)
A list of non-alphanumeric characters to be
considered part of a word by the forward-word,
backward-word etc. editor commands. If unset,
`*?_-.[]~=' is used.
ENVIRONMENT
AFSUSER (+)
Equivalent to the afsuser shell variable.
COLUMNS The number of columns in the terminal. See Terminal
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
gethostname(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
documentation.
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.
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
synchronized 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
management.
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
equivalent. 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 starting
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
experienced 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 functions
in the middle of typed commands, including documentation
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
substitution, 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
associated shell variables, the description of Directory
stack substitution, the dirstack, owd and symlinks shell
variables 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 Language
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, newgrp,
printenv, which and where (q.v.).
New variables that make useful information easily available
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 variables.
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 commands 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
recognized 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 output
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 executed.
ls-F includes file identification characters when sorting
filenames.
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
`subscribe 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 trademarked).
A lot of TOPS-10 users (`The OPerating System for PDP-10')
objected; thus DEC found themselves supporting 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 showing?]).
The creator of tcsh was impressed by this feature and
several 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 filename
expansion is limited to 1/6th the number of characters
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), malloc(3),
setlocale(3), tty(4), a.out(5), termcap(5), environ(7),
termio(7), Introduction to the C Shell
VERSION
This manual documents tcsh 6.06.00 (Cornell) 1995-04-29.
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,
modifications 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, Symmetry
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
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
Enhanced directory printing in prompt
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' section