tcsh(1)
NAME
tcsh - C shell with file name completion and command line editing
SYNOPSIS
tcsh [-bcdefFimnqstvVxX] [-Dname[=value]] [arg ...] tcsh -l
DESCRIPTION
tcsh is an enhanced but completely compatible version of the Berkeley
UNIX C shell, csh(1). It is a command language interpreter usable both
as an interactive login shell and a shell script command processor. It
includes a command-line editor (see The command-line editor),
programmable word 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 does not load any resource or startup files, or perform
any command hashing, and thus starts faster.
-F The shell uses fork(2) instead of vfork(2) to spawn processes. (+)
-i The shell is interactive and prompts for its top-level input, even
if it appears to not be a terminal. Shells are interactive without
this option if their inputs and outputs are terminals.
-l The shell is a login shell. Applicable only if -l is the only flag
specified.
-m The shell loads ~/.tcshrc even if it does not belong to the
effective user. Newer versions of su(1) can pass -m to the shell.
(+)
-n The shell parses commands but does not execute them. This aids in
debugging shell scripts.
-q The shell accepts SIGQUIT (see Signal handling) and behaves when it
is used under a debugger. Job control is disabled. (u)
-s Command input is taken from the standard input.
-t The shell reads and executes a single line of input. A `\' may be
used to escape the newline at the end of this line and continue
onto another line.
-v Sets the verbose shell variable, so that command input is echoed
after history substitution.
-x Sets the echo shell variable, so that commands are echoed
immediately before execution.
-V Sets the verbose shell variable even before executing ~/.tcshrc.
-X Is to -x as -V is to -v.
--help
Print a help message on the standard output and exit. (+)
--version
Print the version/platform/compilation options on the standard
output and exit. This information is also contained in the version
shell variable. (+)
After processing of flag arguments, if arguments remain but none of the
-c, -i, -s, or -t options were given, the first argument is taken as
the name of a file of commands, or ``script'', to be executed. The
shell opens this file and saves its name for possible resubstitution by
`$0'. Because many systems use either the standard version 6 or
version 7 shells whose shell scripts are not compatible with this
shell, the shell uses such a `standard' shell to execute a script whose
first character is not a `#', i.e., that does not start with a comment.
Remaining arguments are placed in the argv shell variable.
Startup and shutdown
A login shell begins by executing commands from the system files
/etc/csh.cshrc and /etc/csh.login. It then executes commands from
files in the user's home directory: first ~/.tcshrc (+) or, if
~/.tcshrc is not found, ~/.cshrc, then ~/.history (or the value of the
histfile shell variable), then ~/.login, and finally ~/.cshdirs (or the
value of the dirsfile shell variable) (+). The shell may read
/etc/csh.login before instead of after /etc/csh.cshrc, and ~/.login
before instead of after ~/.tcshrc or ~/.cshrc and ~/.history, if so
compiled; see the version shell variable. (+)
Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or ~/.cshrc on
startup.
For examples of startup files, please consult
http://tcshrc.sourceforge.net.
Commands like stty(1) and tset(1), which need be run only once per
login, usually go in one's ~/.login file. Users who need to use the
same set of files with both csh(1) and tcsh can have only a ~/.cshrc
which checks for the existence of the tcsh shell variable (q.v.) before
using tcsh-specific commands, or can have both a ~/.cshrc and a
~/.tcshrc which sources (see the builtin command) ~/.cshrc. The rest
of this manual uses `~/.tcshrc' to mean `~/.tcshrc or, if ~/.tcshrc is
not found, ~/.cshrc'.
In the normal case, the shell begins reading commands from the
terminal, prompting with `> '. (Processing of arguments and the use of
the shell to process files containing command scripts are described
later.) The shell repeatedly reads a line of command input, breaks it
into words, places it on the command history list, parses it and
executes each command in the line.
One can log out by typing `^D' on an empty line, `logout' or `login' or
via the shell's autologout mechanism (see the autologout shell
variable). When a login shell terminates it sets the logout shell
variable to `normal' or `automatic' as appropriate, then executes
commands from the files /etc/csh.logout and ~/.logout. The shell may
drop DTR on logout if so compiled; see the version shell variable.
The names of the system login and logout files vary from system to
system for compatibility with different csh(1) variants; see FILES.
Editing
We first describe The command-line editor. The Completion and listing
and Spelling correction sections describe two sets of functionality
that are implemented as editor commands but which deserve their own
treatment. Finally, Editor commands lists and describes the editor
commands specific to the shell and their default bindings.
The command-line editor (+)
Command-line input can be edited using key sequences much like those
used in 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 at just the end; completed
text pushes the rest of the line to the right. Completion in the
middle of a word often results in leftover characters to the right of
the cursor that need to be deleted.
Commands and variables can be completed in much the same way. For
example, typing `em[tab]' would complete `em' to `emacs' if emacs were
the only command on your system beginning with `em'. 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 lists at only the end of the line; in the
middle of a line it deletes the character under the cursor and on an
empty line it logs one out or, if ignoreeof is set, does nothing.
`M-^D', bound to the editor command list-choices, lists completion
possibilities anywhere on a line, and list-choices (or any one of the
related editor commands that do or don't delete, list and/or log out,
listed under delete-char-or-list-or-eof) can be bound to `^D' with the
bindkey builtin command if so desired.
The complete-word-fwd and complete-word-back editor commands (not bound
to any keys by default) can be used to cycle up and down through the
list of possible completions, replacing the current word with the next
or previous word in the list.
The shell variable fignore can be set to a list of suffixes to be
ignored by completion. Consider the following:
> ls
Makefile condiments.h~ main.o side.c
README main.c meal side.o
condiments.h main.c~
> set fignore = (.o \~)
> emacs ma[^D]
main.c main.c~ main.o
> emacs ma[tab]
> emacs main.c
`main.c~' and `main.o' are ignored by completion (but not listing),
because they end in suffixes in fignore. Note that a `\' was needed in
front of `~' to prevent it from being expanded to home as described
under Filename substitution. fignore is ignored if only one completion
is possible.
If the complete shell variable is set to `enhance', completion 1)
ignores case and 2) considers periods, hyphens and underscores (`.',
`-' and `_') to be word separators and hyphens and underscores to be
equivalent. If you had the following files
comp.lang.c comp.lang.perl comp.std.c++
comp.lang.c++ comp.std.c
and typed `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.
If the complete shell variable is set to `Enhance', completion ignores
case and differences between a hyphen and an underscore word separator
only when the user types a lowercase character or a hyphen. Entering
an uppercase character or an underscore will not match the
corresponding lowercase character or hyphen word separator. Typing `rm
a--file[^D]' in the directory of the previous example would still list
all three files, but typing `rm A--file' would match only
`A_silly_file' and typing `rm a__file[^D]' would match just
`A_silly_file' and `another_silly_file' because the user explicitly
used an uppercase or an underscore character.
Completion and listing are affected by several other shell variables:
recexact can be set to complete on the shortest possible unique match,
even if more typing might result in a longer match:
> ls
fodder foo food foonly
> set recexact
> rm fo[tab]
just beeps, because `fo' could expand to `fod' or `foo', but if we type
another `o',
> rm foo[tab]
> rm foo
the completion completes on `foo', even though `food' and `foonly' also
match. autoexpand can be set to run the expand-history editor command
before each completion attempt, autocorrect can be set to spelling-
correct the word to be completed (see Spelling correction) before each
completion attempt and correct can be set to complete commands
automatically after one hits `return'. matchbeep can be set to make
completion beep or not beep in a variety of situations, and nobeep can
be set to never beep at all. nostat can be set to a list of
directories and/or patterns that match directories to prevent the
completion mechanism from stat(2)ing those directories. listmax and
listmaxrows can be set to limit the number of items and rows
(respectively) that are listed without asking first.
recognize_only_executables can be set to make the shell list only
executables when listing commands, but it is quite slow.
Finally, the complete builtin command can be used to tell the shell how
to complete words other than filenames, commands and variables.
Completion and listing do not work on glob-patterns (see Filename
substitution), but the list-glob and expand-glob editor commands
perform equivalent functions for glob-patterns.
Spelling correction (+)
The shell can sometimes correct the spelling of filenames, commands and
variable names as well as completing and listing them.
Individual words can be spelling-corrected with the spell-word editor
command (usually bound to M-s and M-S) and the entire input buffer with
spell-line (usually bound to M-$). The correct shell variable can be
set to `cmd' to correct the command name or `all' to correct the entire
line each time return is typed, and autocorrect can be set to correct
the word to be completed before each completion attempt.
When spelling correction is invoked in any of these ways and the shell
thinks that any part of the command line is misspelled, it prompts with
the corrected line:
> set correct = cmd
> lz /usr/bin
CORRECT>ls /usr/bin (y|n|e|a)?
One can answer `y' or space to execute the corrected line, `e' to leave
the uncorrected command in the input buffer, `a' to abort the command
as if `^C' had been hit, and anything else to execute the original line
unchanged.
Spelling correction recognizes user-defined completions (see the
complete builtin command). If an input word in a position for which a
completion is defined resembles a word in the completion list, spelling
correction registers a misspelling and suggests the latter word as a
correction. However, if the input word does not match any of the
possible completions for that position, spelling correction does not
register a misspelling.
Like completion, spelling correction works anywhere in the line,
pushing the rest of the line to the right and possibly leaving extra
characters to the right of the cursor.
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 that are bound to
letters by default are bound to both lower- and uppercase letters for
convenience.
complete-word (tab)
Completes a word as described under Completion and listing.
complete-word-back (not bound)
Like complete-word-fwd, but steps up from the end of the list.
complete-word-fwd (not bound)
Replaces the current word with the first word in the list of
possible completions. May be repeated to step down through the
list. At the end of the list, beeps and reverts to the
incomplete word.
complete-word-raw (^X-tab)
Like complete-word, but ignores user-defined completions.
copy-prev-word (M-^_)
Copies the previous word in the current line into the input
buffer. See also insert-last-word.
dabbrev-expand (M-/)
Expands the current word to the most recent preceding one for
which the current is a leading substring, wrapping around the
history list (once) if necessary. Repeating dabbrev-expand
without any intervening typing changes to the next previous
word etc., skipping identical matches much like history-search-
backward does.
delete-char (bound to `Del' if using the standard /etc/csh.cshrc)
Deletes the character under the cursor. See also delete-char-
or-list-or-eof.
delete-char-or-eof (not bound)
Does delete-char if there is a character under the cursor or
end-of-file on an empty line. See also delete-char-or-list-or-
eof.
delete-char-or-list (not bound)
Does delete-char if there is a character under the cursor or
list-choices at the end of the line. See also delete-char-or-
list-or-eof.
delete-char-or-list-or-eof (^D)
Does delete-char if there is a character under the cursor,
list-choices at the end of the line or end-of-file on an empty
line. See also those three commands, each of which does only a
single action, and delete-char-or-eof, delete-char-or-list and
list-or-eof, each of which does a different two out of the
three.
down-history (down-arrow, ^N)
Like up-history, but steps down, stopping at the original input
line.
end-of-file (not bound)
Signals an end of file, causing the shell to exit unless the
ignoreeof shell variable (q.v.) is set to prevent this. See
also delete-char-or-list-or-eof.
expand-history (M-space)
Expands history substitutions in the current word. See History
substitution. See also magic-space, toggle-literal-history and
the autoexpand shell variable.
expand-glob (^X-*)
Expands the glob-pattern to the left of the cursor. See
Filename substitution.
expand-line (not bound)
Like expand-history, but expands history substitutions in each
word in the input buffer.
expand-variables (^X-$)
Expands the variable to the left of the cursor. See Variable
substitution.
history-search-backward (M-p, M-P)
Searches backwards through the history list for a command
beginning with the current contents of the input buffer up to
the cursor and copies it into the input buffer. The search
string may be a glob-pattern (see Filename substitution)
containing `*', `?', `[]' or `{}'. up-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.
delete (or any character bound to backward-delete-char)
Undoes the effect of the last character typed and
deletes a character from the search pattern if
appropriate.
^G If the previous search was successful, aborts the
entire search. If not, goes back to the last
successful search.
escape Ends the search, leaving the current line in the
input buffer.
Any other character not bound to self-insert-command terminates
the search, leaving the current line in the input buffer, and
is then interpreted as normal input. In particular, a carriage
return causes the current line to be executed. Emacs mode
only. See also i-search-fwd and history-search-backward.
i-search-fwd (not bound)
Like i-search-back, but searches forward.
insert-last-word (M-_)
Inserts the last word of the previous input line (`!$') into
the input buffer. See also copy-prev-word.
list-choices (M-^D)
Lists completion possibilities as described under Completion
and listing. See also delete-char-or-list-or-eof and list-
choices-raw.
list-choices-raw (^X-^D)
Like list-choices, but ignores user-defined completions.
list-glob (^X-g, ^X-G)
Lists (via the ls-F builtin) matches to the glob-pattern (see
Filename substitution) to the left of the cursor.
list-or-eof (not bound)
Does list-choices or end-of-file on an empty line. See also
delete-char-or-list-or-eof.
magic-space (not bound)
Expands history substitutions in the current line, like expand-
history, and inserts a space. magic-space is designed to be
bound to the space bar, but is not bound by default.
normalize-command (^X-?)
Searches for the current word in PATH and, if it is found,
replaces it with the full path to the executable. Special
characters are quoted. Aliases are expanded and quoted but
commands within aliases are not. This command is useful with
commands that take commands as arguments, e.g., `dbx' and `sh
-x'.
normalize-path (^X-n, ^X-N)
Expands the current word as described under the `expand'
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. If the special alias
helpcommand is defined, it is run with the command name as a
sole argument. Else, documentation should be in a file named
command.help, command.1, command.6, command.8 or command, which
should be in one of the directories listed in the HPATH
environment variable. If there is more than one help file only
the first is printed.
self-insert-command (text characters)
In insert mode (the default), inserts the typed character into
the input line after the character under the cursor. In
overwrite mode, replaces the character under the cursor with
the typed character. The input mode is normally preserved
between lines, but the inputmode shell variable can be set to
`insert' or `overwrite' to put the editor in that mode at the
beginning of each line. See also overwrite-mode.
sequence-lead-in (arrow prefix, meta prefix, ^X)
Indicates that the following characters are part of a multi-key
sequence. Binding a command to a multi-key sequence really
creates two bindings: the first character to sequence-lead-in
and the whole sequence to the command. All sequences beginning
with a character bound to sequence-lead-in are effectively
bound to undefined-key unless bound to another command.
spell-line (M-$)
Attempts to correct the spelling of each word in the input
buffer, like spell-word, but ignores words whose first
character is one of `-', `!', `^' or `%', or which contain `\',
`*' or `?', to avoid problems with switches, substitutions and
the like. See Spelling correction.
spell-word (M-s, M-S)
Attempts to correct the spelling of the current word as
described under Spelling correction. Checks each component of
a word which appears to be a pathname.
toggle-literal-history (M-r, M-R)
Expands or `unexpands' history substitutions in the input
buffer. See also expand-history and the autoexpand shell
variable.
undefined-key (any unbound key)
Beeps.
up-history (up-arrow, ^P)
Copies the previous entry in the history list into the input
buffer. If histlit is set, uses the literal form of the entry.
May be repeated to step up through the history list, stopping
at the top.
vi-search-back (?)
Prompts with `?' for a search string (which may be a glob-
pattern, as with history-search-backward), searches for it and
copies it into the input buffer. The bell rings if no match is
found. Hitting return ends the search and leaves the last
match in the input buffer. Hitting escape ends the search and
executes the match. vi mode only.
vi-search-fwd (/)
Like vi-search-back, but searches forward.
which-command (M-?)
Does a which (see the description of the builtin command) on
the first word of the input buffer.
yank-pop (M-y)
When executed immediately after a yank or another yank-pop,
replaces the yanked string with the next previous string from
the killring. This also has the effect of rotating the
killring, such that this string will be considered the most
recently killed by a later yank command. Repeating yank-pop
will cycle through the killring any number of times.
Lexical structure
The shell splits input lines into words at blanks and tabs. The
special characters `&', `|', `;', `<', `>', `(', and `)' and the
doubled characters `&&', `||', `<<' and `>>' are always separate words,
whether or not they are surrounded by whitespace.
When the shell's input is not a terminal, the character `#' is taken to
begin a comment. Each `#' and the rest of the input line on which it
appears is discarded before further parsing.
A special character (including a blank or tab) may be prevented from
having its special meaning, and possibly made part of another word, by
preceding it with a backslash (`\') or enclosing it in single (`''),
double (`"') or backward (``') quotes. When not otherwise quoted a
newline preceded by a `\' is equivalent to a blank, but inside quotes
this sequence results in a newline.
Furthermore, all Substitutions (see below) except History substitution
can be prevented by enclosing the strings (or parts of strings) in
which they appear with single quotes or by quoting the crucial
character(s) (e.g., `$' or ``' for Variable substitution or Command
substitution respectively) with `\'. (Alias substitution is no
exception: quoting in any way any character of a word for which an
alias has been defined prevents substitution of the alias. The usual
way of quoting an alias is to precede it with a backslash.) History
substitution is prevented by backslashes but not by single quotes.
Strings quoted with double or backward quotes undergo Variable
substitution and Command 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 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 `!{3}d'.
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 search or event
number in 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. With the `s' modifier, only the
patterns contained in the original word are substituted,
not patterns that contain any substitution result.
p Print the new command line but do not execute it.
q Quote the substituted words, preventing further
substitutions.
x Like q, but break into words at blanks, tabs and newlines.
Modifiers are applied to only the first modifiable word (unless `g' is
used). It is an error for no word to be modifiable.
For example, the `diff' command might have been written as `diff
wumpus.man.old !#^:r', using `:r' to remove `.old' from the first
argument on the same line (`!#^'). We could say `echo hello out
there', then `echo !*:u' to capitalize `hello', `echo !*:au' to say it
out loud, or `echo !*:agu' to really shout. We might follow `mail -s
"I forgot my password" rot' with `!:s/rot/root' to correct the spelling
of `root' (but see Spelling correction for a different approach).
There is a special abbreviation for substitutions. `^', when it is the
first character on an input line, is equivalent to `!:s^'. Thus we
might have said `^rot^root' to make the spelling correction in the
previous example. This is the only history substitution which does not
explicitly begin with `!'.
(+) In csh as such, only one modifier may be applied to each history or
variable expansion. In tcsh, more than one may be used, for example
% mv wumpus.man /usr/man/man1/wumpus.1
% man !$:t:r
man wumpus
In csh, the result would be `wumpus.1:r'. A substitution followed by a
colon may need to be insulated from it with braces:
> mv a.out /usr/games/wumpus
> setenv PATH !$: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 multi-
word values are ignored.
After the input line is aliased and parsed, and before each command is
executed, variable substitution is performed keyed by `$' characters.
This expansion can be prevented by preceding the `$' with a `\' except
within `"'s where it always occurs, and within `''s where it never
occurs. Strings quoted by ``' are interpreted later (see Command
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 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 some of 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 the command line of the last command executed. (+)
$< Substitutes a line from the standard input, with no further
interpretation thereafter. It can be used to read from the
keyboard in a shell script. (+) While csh always quotes $<, as
if it were equivalent to `$<:q', tcsh does not. Furthermore,
when tcsh is waiting for a line to be typed the user may type
an interrupt to interrupt the sequence into which the line is
to be substituted, but csh does not allow this.
The editor command expand-variables, normally bound to `^X-$', can be
used to interactively expand individual variables.
Command, filename and directory stack substitution
The remaining substitutions are applied selectively to the arguments of
builtin commands. This means that portions of expressions which are
not evaluated are not subjected to these expansions. For commands
which are not internal to the shell, the command name is substituted
separately from the argument list. This occurs very late, after input-
output redirection is performed, and in a child of the main shell.
Command substitution
Command substitution is indicated by a command enclosed in ``'. The
output from such a command is broken into separate words at blanks,
tabs and newlines, and null words are discarded. The output is
variable and command substituted and put in place of the original
string.
Command substitutions inside double quotes (`"') retain blanks and
tabs; only newlines force new words. The single final newline does not
force a new word in any case. It is thus possible for a command
substitution to yield only part of a word, even if the command outputs
a complete line.
By default, the shell since version 6.12 replaces all newline and
carriage return characters in the command by spaces. If this is
switched off by unsetting csubstnonl, newlines separate commands as
usual.
Filename substitution
If a word contains any of the characters `*', `?', `[' or `{' or begins
with the character `~' it is a candidate for filename substitution,
also known as ``globbing''. This word is then regarded as a pattern
(``glob-pattern''), and replaced with an alphabetically sorted list of
file names which match the pattern.
In matching filenames, the character `.' at the beginning of a filename
or immediately following a `/', as well as the character `/' must be
matched explicitly (unless either globdot or globstar or both are
set(+)). The character `*' matches any string of characters, including
the null string. The character `?' matches any single character. The
sequence `[...]' matches any one of the characters enclosed. Within
`[...]', a pair of characters separated by `-' matches any character
lexically between the two.
(+) Some glob-patterns can be negated: The sequence `[^...]' matches
any single character not specified by the characters and/or ranges of
characters in the braces.
An entire glob-pattern can also be negated with `^':
> echo *
bang crash crunch ouch
> echo ^cr*
bang ouch
Glob-patterns which do not use `?', `*', or `[]' or which use `{}' or
`~' (below) are not negated correctly.
The metanotation `a{b,c,d}e' is a shorthand for `abe ace ade'. Left-
to-right order is preserved: `/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 globstar shell variable can be set to allow `**' or `***' as a file
glob pattern that matches any string of characters including `/',
recursively traversing any existing sub-directories. For example, `ls
**.c' will list all the .c files in the current directory tree. If
used by itself, it will match match zero or more sub-directories (e.g.
`ls /usr/include/**/time.h' will list any file named `time.h' in the
/usr/include directory tree; `ls /usr/include/**time.h' will match any
file in the /usr/include directory tree ending in `time.h'; and `ls
/usr/include/**time**.h' will match any .h file with `time' either in a
subdirectory name or in the filename itself). To prevent problems with
recursion, the `**' glob-pattern will not descend into a symbolic link
containing a directory. To override this, use `***' (+)
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 by only those commands.
Nonetheless, it too can be prevented by quoting.
Commands
The next three sections describe how the shell executes commands and
deals with their input and output.
Simple commands, pipelines and sequences
A simple command is a sequence of words, the first of which specifies
the command to be executed. A series of simple commands joined by `|'
characters forms a pipeline. The output of each command in a pipeline
is connected to the input of the next.
Simple commands and pipelines may be joined into sequences with `;',
and will be executed sequentially. Commands and pipelines can also be
joined into sequences with `||' or `&&', indicating, as in the C
language, that the second is to be executed only if the first fails or
succeeds respectively.
A simple command, pipeline or sequence may be placed in parentheses,
`()', to form a simple command, which may in turn be a component of a
pipeline or sequence. A command, pipeline or sequence can be executed
without waiting for it to terminate by following it with an `&'.
Builtin and non-builtin command execution
Builtin commands are executed within the shell. If any component of a
pipeline except the last is a builtin command, the pipeline is executed
in a subshell.
Parenthesized commands are always executed in a subshell.
(cd; pwd); pwd
thus prints the home directory, leaving you where you were (printing
this after the home directory), while
cd; pwd
leaves you in the home directory. Parenthesized commands are most
often used to prevent cd from affecting the current shell.
When a command to be executed is found not to be a builtin command the
shell attempts to execute the command via execve(2). Each word in the
variable path names a directory in which the shell will look for the
command. If the shell is not given a -f option, the shell hashes the
names in these directories into an internal table so that it will try
an execve(2) in only a directory where there is a possibility that the
command resides there. This greatly speeds command location when a
large number of directories are present in the search path. This
hashing mechanism is not used:
1. If hashing is turned explicitly off via unhash.
2. If the shell was given a -f argument.
3. For each directory component of path which does not begin with a
`/'.
4. If the command contains a `/'.
In the above four cases the shell concatenates each component of the
path vector with the given command name to form a path name of a file
which it then attempts to execute it. If execution is successful, the
search stops.
If the file has execute permissions but is not an executable to the
system (i.e., it is neither an executable binary nor a script that
specifies its interpreter), then it is assumed to be a file containing
shell commands and a new shell is spawned to read it. The shell
special alias may be set to specify an interpreter other than the shell
itself.
On systems which do not understand the `#!' script interpreter
convention the shell may be compiled to emulate it; see the version
shell variable. If so, the shell checks the first line of the file to
see if it is of the form `#!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, it is truncated,
its previous contents being lost.
If the shell variable noclobber is set, then the file must not
exist or be a character special file (e.g., a terminal or
`/dev/null') or an error results. This helps prevent
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.
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 (+)
R Has been migrated (Convex only) (+)
L Applies subsequent operators in a multiple-operator test to a
symbolic link rather than to the file to which the link points
(+) *
file is command and filename expanded and then tested to see if it has
the specified relationship to the real user. If file does not exist or
is inaccessible or, for the operators indicated by `*', if the
specified file type does not exist on the current system, then all
enquiries return false, i.e., `0'.
These operators may be combined for conciseness: `-xy file' is
equivalent to `-x file && -y file'. (+) For example, `-fx' is true
(returns `1') for plain executable files, but not for directories.
L may be used in a multiple-operator test to apply subsequent operators
to a symbolic link rather than to the file to which the link points.
For example, `-lLo' is true for links owned by the 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 unambiguous prefix of
the string typed in to start it: `%ex' would normally restart a
suspended ex(1) job, if there were only one suspended job whose name
began with the string `ex'. It is also possible to say `%?string' to
specify a job whose text contains string, if there is only one such
job.
The shell maintains a notion of the current and previous jobs. In
output pertaining to jobs, the current job is marked with a `+' and the
previous job with a `-'. The abbreviations `%+', `%', and (by analogy
with the syntax of the history mechanism) `%%' all refer to the current
job, and `%-' refers to the previous job.
The job control mechanism requires that the stty(1) option `new' be set
on some systems. It is an artifact from a `new' implementation of the
tty driver which allows generation of interrupt characters from the
keyboard to tell jobs to stop. See stty(1) and the setty builtin
command for details on setting options in the new tty driver.
Status reporting
The shell learns immediately whenever a process changes state. It
normally informs you whenever a job becomes blocked so that no further
progress is possible, but only right before it prints a prompt. This
is done so that it does not otherwise disturb your work. If, however,
you set the shell variable notify, the shell will notify you
immediately of changes of status in background jobs. There is also a
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 `There are suspended jobs.' You may use the jobs command to
see what they are. If you do this or immediately try to exit again,
the shell will not warn you a second time, and the suspended jobs will
be terminated.
Automatic, periodic and timed events (+)
There are various ways to run commands and take other actions
automatically at various times in the ``life cycle'' of the shell.
They are summarized here, and described in detail under the appropriate
Builtin commands, Special shell variables and Special aliases.
The sched builtin command puts commands in a scheduled-event list, to
be executed by the shell at a given time.
The beepcmd, cwdcmd, periodic, precmd, postcmd, and jobcmd Special
aliases can be set, respectively, to execute commands when the shell
wants to ring the bell, when the working directory changes, every
tperiod minutes, before each prompt, before each command gets executed,
after each command gets executed, and when a job is started or is
brought into the foreground.
The autologout shell variable can be set to log out or lock the shell
after a given number of minutes of inactivity.
The mail shell variable can be set to check for new mail periodically.
The printexitvalue shell variable can be set to print the exit status
of commands which exit with a status other than zero.
The rmstar shell variable can be set to ask the user, when `rm *' is
typed, if that is really what was meant.
The time shell variable can be set to execute the time builtin command
after the completion of any process that takes more than a given number
of CPU seconds.
The watch and who shell variables can be set to report when selected
users log in or out, and the log builtin command reports on those users
at any time.
Native Language System support (+)
The shell is eight bit clean (if so compiled; see the version shell
variable) and thus supports character sets needing this capability.
NLS support differs depending on whether or not the shell was compiled
to use the system's NLS (again, see version). In either case, 7-bit
ASCII is the default character code (e.g., the classification of which
characters are printable) and sorting, and changing the LANG or
LC_CTYPE environment variables causes a check for possible changes in
these respects.
When using the system's NLS, the setlocale(3) function is called to
determine appropriate character code/classification and sorting (e.g.,
a 'en_CA.UTF-8' would yield "UTF-8" as a character code). This
function typically examines the LANG and LC_CTYPE environment
variables; refer to the system documentation for further details. When
not using the system's NLS, the shell simulates it by assuming that the
ISO 8859-1 character set is used whenever either of the LANG and
LC_CTYPE variables are set, regardless of their values. Sorting is not
affected for the simulated NLS.
In addition, with both real and simulated NLS, all printable characters
in the range \200-\377, i.e., those that have M-char bindings, are
automatically rebound to self-insert-command. The corresponding
binding for the escape-char sequence, if any, is left alone. These
characters are not rebound if the NOREBIND environment variable is set.
This may be useful for the simulated NLS or a primitive real NLS which
assumes full ISO 8859-1. Otherwise, all M-char bindings in the range
\240-\377 are effectively undone. Explicitly rebinding the relevant
keys with bindkey is of course still possible.
Unknown characters (i.e., those that are neither printable nor control
characters) are printed in the format \nnn. If the tty is not in 8 bit
mode, other 8 bit characters are printed by converting them to ASCII
and using standout mode. The shell never changes the 7/8 bit mode of
the tty and tracks user-initiated changes of 7/8 bit mode. NLS users
(or, for that matter, those who want to use a meta key) may need to
explicitly set the tty in 8 bit mode through the appropriate stty(1)
command in, e.g., the ~/.login file.
OS variant support (+)
A number of new builtin commands are provided to support features in
particular operating systems. All are described in detail in the
Builtin commands section.
On systems that support TCF (aix-ibm370, aix-ps2), getspath and
setspath get and set the system execution path, getxvers and setxvers
get and set the experimental version prefix and migrate migrates
processes between sites. The jobs builtin prints the site on which
each job is executing.
Under BS2000, bs2cmd executes commands of the underlying BS2000/OSD
operating system.
Under Domain/OS, inlib adds shared libraries to the current
environment, rootnode changes the rootnode and ver changes the systype.
Under Mach, setpath is equivalent to Mach's setpath(1).
Under Masscomp/RTU and Harris CX/UX, universe sets the universe.
Under Harris CX/UX, ucb or att runs a command under the specified
universe.
Under Convex/OS, warp prints or sets the universe.
The VENDOR, OSTYPE and MACHTYPE environment variables indicate
respectively the vendor, operating system and machine type
(microprocessor class or machine model) of the system on which the
shell thinks it is running. These are particularly useful when sharing
one's home directory between several types of machines; one can, for
example,
set path = (~/bin.$MACHTYPE /usr/ucb /bin /usr/bin .)
in one's ~/.login and put executables compiled for each machine in the
appropriate directory.
The version shell variable indicates what options were chosen when the
shell was compiled.
Note also the newgrp builtin, the afsuser and echo_style shell
variables and the system-dependent locations of the shell's input files
(see FILES).
Signal handling
Login shells ignore interrupts when reading the file ~/.logout. The
shell ignores quit signals unless started with -q. Login shells catch
the terminate signal, but non-login shells inherit the terminate
behavior from their parents. Other signals have the values which the
shell inherited from its parent.
In shell scripts, the shell's handling of interrupt and terminate
signals can be controlled with onintr, and its handling of hangups can
be controlled with hup and nohup.
The shell exits on a hangup (see also the logout shell variable). By
default, the shell's children do too, but the shell does not send them
a hangup when it exits. hup arranges for the shell to send a hangup to
a child when it exits, and nohup sets a child to ignore hangups.
Terminal management (+)
The shell uses three different sets of terminal (``tty'') modes:
`edit', used when editing, `quote', used when quoting literal
characters, and `execute', used when executing commands. The shell
holds some settings in each mode constant, so commands which leave the
tty in a confused state do not interfere with the shell. The shell
also matches changes in the speed and padding of the tty. The list of
tty modes that are kept constant can be examined and modified with the
setty builtin. Note that although the editor uses CBREAK mode (or its
equivalent), it takes typed-ahead characters anyway.
The echotc, settc and telltc commands can be used to manipulate and
debug terminal capabilities from the command line.
On systems that support SIGWINCH or SIGWINDOW, the shell adapts to
window resizing automatically and adjusts the environment variables
LINES and COLUMNS if set. If the environment variable TERMCAP contains
li# and co# fields, the shell adjusts them to reflect the new window
size.
REFERENCE
The next sections of this manual describe all of the available Builtin
commands, Special aliases and Special shell variables.
Builtin commands
%job A synonym for the fg builtin command.
%job & A synonym for the bg builtin command.
: Does nothing, successfully.
@
@ name = expr
@ name[index] = expr
@ name++|--
@ name[index]++|--
The first form prints the values of all shell variables.
The second form assigns the value of expr to name. The third
form assigns the value of expr to the index'th component of
name; both name and its index'th component must already exist.
expr may contain the operators `*', `+', etc., as in C. If
expr contains `<', `>', `&' or `' then at least that part of
expr must be placed within `()'. Note that the syntax of expr
has nothing to do with that described under Expressions.
The fourth and fifth forms increment (`++') or decrement (`--')
name or its index'th component.
The space between `@' and name is required. The spaces between
name and `=' and between `=' and expr are optional. Components
of expr must be separated by spaces.
alias [name [wordlist]]
Without arguments, prints all aliases. With name, prints the
alias for name. With name and wordlist, assigns wordlist as
the alias of name. wordlist is command and filename
substituted. name may not be `alias' or `unalias'. See also
the unalias builtin command.
alloc Shows the amount of dynamic memory acquired, broken down into
used and free memory. With an argument shows the number of
free and used blocks in each size category. The categories
start at size 8 and double at each step. This command's output
may vary across system types, because systems other than the
VAX may use a different memory allocator.
bg [%job ...]
Puts the specified jobs (or, without arguments, the current
job) into the background, continuing each if it is stopped.
job may be a number, a string, `', `%', `+' or `-' as described
under Jobs.
bindkey [-l|-d|-e|-v|-u] (+)
bindkey [-a] [-b] [-k] [-r] [--] key (+)
bindkey [-a] [-b] [-k] [-c|-s] [--] key command (+)
Without options, the first form lists all bound keys and the
editor command to which each is bound, the second form lists
the editor command to which key is bound and the third form
binds the editor command command to key. Options include:
-l Lists all editor commands and a short description of each.
-d Binds all keys to the standard bindings for the default
editor.
-e Binds all keys to the standard GNU Emacs-like bindings.
-v Binds all keys to the standard vi(1)-like bindings.
-a Lists or changes key-bindings in the alternative key map.
This is the key map used in vi command mode.
-b key is interpreted as a control character written
^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:
Bell
Backspace
\e Escape
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
\v Vertical tab
\nnn The ASCII character corresponding to the octal
number nnn
`\' nullifies the special meaning of the following character,
if it has any, notably `\' and `^'.
bs2cmd bs2000-command (+)
Passes bs2000-command to the BS2000 command interpreter for
execution. Only non-interactive commands can be executed, and
it is not possible to execute any command that would overlay
the image of the current process, like /EXECUTE or /CALL-
PROCEDURE. (BS2000 only)
break Causes execution to resume after the end of the nearest
enclosing foreach or while. The remaining commands on the
current line are executed. Multi-level breaks are thus
possible by writing them all on one line.
breaksw Causes a break from a switch, resuming after the endsw.
builtins (+)
Prints the names of all builtin commands.
bye (+) A synonym for the logout builtin command. Available only if
the shell was so compiled; see the version shell variable.
case label:
A label in a switch statement as discussed below.
cd [-p] [-l] [-n|-v] [I--] [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. (+) Using -- forces a break from option
processing so the next word is taken as the directory name even
if it begins with '-'. (+)
See also the implicitcd shell variable.
chdir A synonym for the cd builtin command.
complete [command [word/pattern/list[:select]/[[suffix]/] ...]] (+)
Without arguments, lists all completions. With command, lists
completions for command. With command and word etc., defines
completions.
command may be a full command name or a glob-pattern (see
Filename substitution). It can begin with `-' to indicate that
completion should be used only when command is ambiguous.
word specifies which word relative to the current word is to be
completed, and may be one of the following:
c Current-word completion. pattern is a glob-pattern
which must match the beginning of the current word on
the command line. pattern is ignored when completing
the current word.
C Like c, but includes pattern when completing the
current word.
n Next-word completion. pattern is a glob-pattern which
must match the beginning of the previous word on the
command line.
N Like n, but must match the beginning of the word two
before the current word.
p Position-dependent completion. pattern is a numeric
range, with the same syntax used to index shell
variables, which must include the current word.
list, the list of possible completions, may be one of the
following:
a Aliases
b Bindings (editor commands)
c Commands (builtin or external commands)
C External commands which begin with the supplied
path prefix
d Directories
D Directories which begin with the supplied path
prefix
e Environment variables
f Filenames
F Filenames which begin with the supplied path prefix
g Groupnames
j Jobs
l Limits
n Nothing
s Shell variables
S Signals
t Plain (``text'') files
T Plain (``text'') files which begin with the
supplied path prefix
v Any variables
u Usernames
x Like n, but prints select when list-choices is
used.
X Completions
$var Words from the variable var
(...) Words from the given list
`...` Words from the output of command
select is an optional glob-pattern. If given, words from only
list that match select are considered and the fignore shell
variable is ignored. The last three types of completion may
not have a select pattern, and x uses select as an explanatory
message when the list-choices editor command is used.
suffix is a single character to be appended to a successful
completion. If null, no character is appended. If omitted (in
which case the fourth delimiter can also be omitted), a slash
is appended to directories and a space to other words.
command invoked from `...` version has additional environment
variable set, the variable name is COMMAND_LINE and contains
(as its name indicates) contents of the current (already typed
in) command line. One can examine and use contents of the
COMMAND_LINE variable in her custom script to build more
sophisticated completions (see completion for svn(1) included
in this package).
Now for some examples. Some commands take only directories as
arguments, so there's no point completing plain files.
> complete cd 'p/1/d/'
completes only the first word following `cd' (`p/1') with a
directory. p-type completion can also be used to narrow down
command completion:
> co[^D]
complete compress
> complete -co* 'p/0/(compress)/'
> co[^D]
> compress
This completion completes commands (words in position 0, `p/0')
which begin with `co' (thus matching `co*') to `compress' (the
only word in the list). The leading `-' indicates that this
completion is to be used with only ambiguous commands.
> complete find 'n/-user/u/'
is an example of n-type completion. Any word following `find'
and immediately following `-user' is completed from the list of
users.
> complete cc 'c/-I/d/'
demonstrates c-type completion. Any word following `cc' and
beginning with `-I' is completed as a directory. `-I' is not
taken as part of the directory because we used lowercase c.
Different lists are useful with different commands.
> complete alias 'p/1/a/'
> complete man 'p/*/c/'
> complete set 'p/1/s/'
> complete true 'p/1/x:Truth has no options./'
These complete words following `alias' with aliases, `man' with
commands, and `set' with shell variables. `true' doesn't have
any options, so x does nothing when completion is attempted and
prints `Truth has no options.' when completion choices are
listed.
Note that the man example, and several other examples below,
could just as well have used 'c/*' or 'n/*' as 'p/*'.
Words can be completed from a variable evaluated at completion
time,
> complete ftp 'p/1/$hostnames/'
> set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu
> ftp [^C]
> set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu
uunet.uu.net)
> ftp [^D]
rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net
or from a command run at completion time:
> complete kill 'p/*/`ps | awk \{print\ \$1\}`/'
> kill -9 [^D]
23113 23377 23380 23406 23429 23529 23530 PID
Note that the complete command does not itself quote its
arguments, so the braces, space and `$' in `{print $1}' must be
quoted explicitly.
One command can have multiple completions:
> complete dbx 'p/2/(core)/' 'p/*/c/'
completes the second argument to `dbx' with the word `core' and
all other arguments with commands. Note that the positional
completion is specified before the next-word completion.
Because completions are evaluated from left to right, if the
next-word completion were specified first it would always match
and the positional completion would never be executed. This is
a common mistake when defining a completion.
The select pattern is useful when a command takes files with
only particular forms as arguments. For example,
> complete cc 'p/*/f:*.[cao]/'
completes `cc' arguments to files ending in only `.c', `.a', or
`.o'. select can also exclude files, using negation of a glob-
pattern as described under Filename substitution. One might
use
> complete rm 'p/*/f:^*.{c,h,cc,C,tex,1,man,l,y}/'
to exclude precious source code from `rm' completion. Of
course, one could still type excluded names manually or
override the completion mechanism using the complete-word-raw
or list-choices-raw editor commands (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 works at only the beginning of a
word.
suffix is used to add a nonstandard suffix (not space or `/'
for directories) to completed words.
> complete finger 'c/*@/$hostnames/' 'p/1/u/@'
completes arguments to `finger' from the list of users, appends
an `@', and then completes after the `@' from the `hostnames'
variable. Note again the order in which the completions are
specified.
Finally, here's a complex example for inspiration:
> complete find \
'n/-name/f/' 'n/-newer/f/' 'n/-{,n}cpio/f/' \
n/-exec/c/' 'n/-ok/c/' 'n/-user/u/' \
'n/-group/g/' 'n/-fstype/(nfs 4.2)/' \
'n/-type/(b c d f l p s)/' \
c/-/(name newer cpio ncpio exec ok user \
group fstype type atime ctime depth inum \
ls mtime nogroup nouser perm print prune \
size xdev)/' \
'p/*/d/'
This completes words following `-name', `-newer', `-cpio' or
`ncpio' (note the pattern which matches both) to files, words
following `-exec' or `-ok' to commands, words following `user'
and `group' to users and groups respectively and words
following `-fstype' or `-type' to members of the given lists.
It also completes the switches themselves from the given list
(note the use of c-type completion) and completes anything not
otherwise completed to a directory. Whew.
Remember that programmed completions are ignored if the word
being completed is a tilde substitution (beginning with `~') or
a variable (beginning with `$'). complete is an experimental
feature, and the syntax may change in future versions of the
shell. See also the uncomplete builtin command.
continue
Continues execution of the nearest enclosing while or foreach.
The rest of the commands on the current line are executed.
default:
Labels the default case in a switch statement. It should come
after all case labels.
dirs [-l] [-n|-v]
dirs -S|-L [filename] (+)
dirs -c (+)
The first form prints the directory stack. The top of the
stack is at the left and the first directory in the stack is
the current directory. With -l, `~' or `~name' in the output
is expanded explicitly to home or the pathname of the home
directory for user name. (+) With -n, entries are wrapped
before they reach the edge of the screen. (+) With -v, entries
are printed one per line, preceded by their stack positions.
(+) If more than one of -n or -v is given, -v takes precedence.
-p is accepted but does nothing.
With -S, the second form saves the directory stack to filename
as a series of cd and pushd commands. With -L, the shell
sources filename, which is presumably a directory stack file
saved by the -S option or the savedirs mechanism. In either
case, dirsfile is used if filename is not given and ~/.cshdirs
is used if dirsfile is unset.
Note that login shells do the equivalent of `dirs -L' on
startup and, if savedirs is set, `dirs -S' before exiting.
Because only ~/.tcshrc is normally sourced before ~/.cshdirs,
dirsfile should be set in ~/.tcshrc rather than ~/.login.
The last form clears the directory stack.
echo [-n] word ...
Writes each word to the shell's standard output, separated by
spaces and terminated with a newline. The echo_style shell
variable may be set to emulate (or not) the flags and escape
sequences of the BSD and/or System V versions of echo; see
echo(1).
echotc [-sv] arg ... (+)
Exercises the terminal capabilities (see termcap(5)) in args.
For example, 'echotc home' sends the cursor to the home
position, 'echotc cm 3 10' sends it to column 3 and row 10, and
'echotc ts 0; echo "This is a test."; echotc fs' prints "This
is a test." in the status line.
If arg is 'baud', 'cols', 'lines', 'meta' or 'tabs', prints the
value of that capability ("yes" or "no" indicating that the
terminal does or does not have that capability). One might use
this to make the output from a shell script less verbose on
slow terminals, or limit command output to the number of lines
on the screen:
> set history=`echotc lines`
> @ history--
Termcap strings may contain wildcards which will not echo
correctly. One should use double quotes when setting a shell
variable to a terminal capability string, as in the following
example that places the date in the status line:
> set tosl="`echotc ts 0`"
> set frsl="`echotc fs`"
> echo -n "$tosl";date; echo -n "$frsl"
With -s, nonexistent capabilities return the empty string
rather than causing an error. With -v, messages are verbose.
else
end
endif
endsw See the description of the foreach, if, switch, and while
statements below.
eval arg ...
Treats the arguments as input to the shell and executes the
resulting command(s) in the context of the current shell. This
is usually used to execute commands generated as the result of
command or variable substitution, because parsing occurs before
these substitutions. See tset(1) for a sample use of eval.
exec command
Executes the specified command in place of the current shell.
exit [expr]
The shell exits either with the value of the specified expr (an
expression, as described under Expressions) or, without expr,
with the value 0.
fg [%job ...]
Brings the specified jobs (or, without arguments, the current
job) into the foreground, continuing each if it is stopped.
job may be a number, a string, `', `%', `+' or `-' as described
under Jobs. See also the run-fg-editor editor command.
filetest -op file ... (+)
Applies op (which is a file inquiry operator as described under
File inquiry operators) to each file and returns the results as
a space-separated list.
foreach name (wordlist)
...
end Successively sets the variable name to each member of wordlist
and executes the sequence of commands between this command and
the matching end. (Both foreach and end must appear alone on
separate lines.) The builtin command continue may be used to
continue the loop prematurely and the builtin command break to
terminate it prematurely. When this command is read from the
terminal, the loop is read once prompting with `foreach? ' (or
prompt2) before any statements in the loop are executed. If
you make a mistake typing in a loop at the terminal you can rub
it out.
getspath (+)
Prints the system execution path. (TCF only)
getxvers (+)
Prints the experimental version prefix. (TCF only)
glob wordlist
Like echo, but the `-n' parameter is not recognized and words
are delimited by null characters in the output. Useful for
programs which wish to use the shell to filename expand a list
of words.
goto word
word is filename and command-substituted to yield a string of
the form `label'. The shell rewinds its input as much as
possible, searches for a line of the form `label:', possibly
preceded by blanks or tabs, and continues execution after that
line.
hashstat
Prints a statistics line indicating how effective the internal
hash table has been at locating commands (and avoiding exec's).
An exec is attempted for each component of the path where the
hash function indicates a possible hit, and in each component
which does not begin with a `/'.
On machines without vfork(2), prints only the number and size
of hash buckets.
history [-hTr] [n]
history -S|-L|-M [filename] (+)
history -c (+)
The first form prints the history event list. If n is given
only the n most recent events are printed or saved. With -h,
the history list is printed without leading numbers. If -T is
specified, timestamps are printed also in comment form. (This
can be used to produce files suitable for loading with 'history
-L' or 'source -h'.) With -r, the order of printing is most
recent first rather than oldest first.
With -S, the second form saves the history list to filename.
If the first word of the savehist shell variable is set to a
number, at most that many lines are saved. If the second word
of savehist is set to `merge', the history list is merged with
the existing history file instead of replacing it (if there is
one) and sorted by time stamp. (+) Merging is intended for an
environment like the X Window System with several shells in
simultaneous use. Currently it succeeds only when the shells
quit nicely one after another.
With -L, the shell appends filename, which is presumably a
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,
causes the non-interactive shell only to exit on a hangup for
the remainder of the script. See also Signal handling and the
nohup builtin command.
if (expr) command
If expr (an expression, as described under Expressions)
evaluates true, then command is executed. Variable
substitution on command happens early, at the same time it does
for the rest of the if command. command must be a simple
command, not an alias, a pipeline, a command list or a
parenthesized command list, but it may have arguments.
Input/output redirection occurs even if expr is false and
command is thus not executed; this is a bug.
if (expr) then
...
else if (expr2) then
...
else
...
endif If the specified expr is true then the commands to the first
else are executed; otherwise if expr2 is true then the commands
to the second else are executed, etc. Any number of else-if
pairs are possible; only one endif is needed. The else part is
likewise optional. (The words else and endif must appear at
the beginning of input lines; the if must appear alone on its
input line or after an else.)
inlib shared-library ... (+)
Adds each shared-library to the current environment. There is
no way to remove a shared library. (Domain/OS only)
jobs [-l]
Lists the active jobs. With -l, lists process IDs in addition
to the normal information. On TCF systems, prints the site on
which each job is executing.
kill [-s signal] %job|pid ...
kill -l The first and second forms sends the specified signal (or, if
none is given, the TERM (terminate) signal) to the specified
jobs or processes. job may be a number, a string, `', `%', `+'
or `-' as described under Jobs. Signals are either given by
number or by name (as given in /usr/include/signal.h, stripped
of the prefix `SIG'). There is no default job; saying just
`kill' does not send a signal to the current job. If the
signal being sent is TERM (terminate) or HUP (hangup), then the
job or process is sent a CONT (continue) signal as well. The
third 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 (if supported by the
OS):
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
memoryuse
the maximum amount of physical memory a process may have
allocated to it at a given time
vmemoryuse
the maximum amount of virtual memory a process may have
allocated to it at a given time (address space)
vmemoryuse
the maximum amount of virtual memory a process may have
allocated to it at a given time
heapsize
the maximum amount of memory a process may allocate per
brk() system call
descriptors or openfiles
the maximum number of open files for this process
concurrency
the maximum number of threads for this process
memorylocked
the maximum size which a process may lock into memory
using mlock(2)
maxproc
the maximum number of simultaneous processes for this
user id
sbsize the maximum size of socket buffer usage for this user
swapsize
the maximum amount of swap space reserved or used for
this user
maxlocks
the maximum number of locks for this user
maxsignal
the maximum number of pending signals for this user
maxmessage
the maximum number of bytes in POSIX mqueues for this
user
maxnice
the maximum nice priority the user is allowed to raise
mapped from [19...-20] to [0...39] for this user
maxrtprio
the maximum realtime priority for this user maxrttime
the timeout for RT tasks in microseconds for this user.
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' or `g' or `gigabytes' may
also be used. For cputime the default scaling is `seconds',
while `m' for minutes or `h' for hours, or a time of the form
`mm:ss' giving minutes and seconds may be used.
If maximum-use is `unlimited', then the limitation on the
specified resource is removed (this is equivalent to the
unlimit builtin command).
For both resource names and scale factors, unambiguous prefixes
of the names suffice.
log (+) Prints the watch shell variable and reports on each user
indicated in watch who is logged in, regardless of when they
last logged in. See also watchlog.
login Terminates a login shell, replacing it with an instance of
/bin/login. This is one way to log off, included for
compatibility with sh(1).
logout Terminates a login shell. Especially useful if ignoreeof is
set.
ls-F [-switch ...] [file ...] (+)
Lists files like `ls -F', but much faster. 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 (on only systems that have them, of
course):
@ 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.
The ls-F builtin can list files using different colors
depending on the filetype or extension. See the color shell
variable and the LS_COLORS environment variable.
migrate [-site] pid|%jobid ... (+)
migrate -site (+)
The first form migrates the process or job to the site
specified or the default site determined by the system path.
The second form is equivalent to `migrate -site $$': it
migrates the current process to the specified site. Migrating
the shell itself can cause unexpected behavior, because the
shell does not like to lose its tty. (TCF only)
newgrp [-] [group] (+)
Equivalent to `exec newgrp'; 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, causes the
non-interactive shell only to ignore hangups for the remainder
of the script. See also Signal handling and the hup builtin
command.
notify [%job ...]
Causes the shell to notify the user asynchronously when the
status of any of the specified jobs (or, without %job, the
current job) changes, instead of waiting until the next prompt
as is usual. job may be a number, a string, `', `%', `+' or
`-' as described under Jobs. See also the notify shell
variable.
onintr [-|label]
Controls the action of the shell on interrupts. Without
arguments, restores the default action of the shell on
interrupts, which is to terminate shell scripts or to return to
the terminal command input level. With `-', causes all
interrupts to be ignored. With label, causes the shell to
execute a `goto label' when an interrupt is received or a child
process terminates because it was interrupted.
onintr is ignored if the shell is running detached and in
system startup files (see FILES), where interrupts are disabled
anyway.
popd [-p] [-l] [-n|-v] [+n]
Without arguments, pops the directory stack and returns to the
new top directory. With a number `+n', discards the 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 the autorehash shell variable is not set and new
commands are added to directories in path while you are logged
in. With autorehash, a new command will be found
automatically, except in the special case where another command
of the same name which is located in a different directory
already exists in the hash table. Also flushes the cache of
home directories built by tilde expansion.
repeat count command
The specified command, which is subject to the same
restrictions as the command in the one line if statement above,
is executed count times. I/O redirections occur exactly once,
even if count is 0.
rootnode //nodename (+)
Changes the rootnode to //nodename, so that `/' will be
interpreted as `//nodename'. (Domain/OS only)
sched (+)
sched [+]hh:mm command (+)
sched -n (+)
The first form prints the scheduled-event list. The sched
shell variable may be set to define the format in which the
scheduled-event list is printed. The second form adds command
to the scheduled-event list. For example,
> sched 11:00 echo It\'s eleven o\'clock.
causes the shell to echo `It's eleven o'clock.' at 11 AM. The
time may be in 12-hour AM/PM format
> sched 5pm set prompt='[%h] It\'s after 5; go home: >'
or may be relative to the current time:
> sched +2:15 /usr/lib/uucp/uucico -r1 -sother
A relative time specification may not use AM/PM format. The
third form removes item n from the event list:
> sched
1 Wed Apr 4 15:42 /usr/lib/uucp/uucico -r1 -sother
2 Wed Apr 4 17:00 set prompt=[%h] It's after 5; go
home: >
> sched -2
> sched
1 Wed Apr 4 15:42 /usr/lib/uucp/uucico -r1 -sother
A command in the scheduled-event list is executed just before
the first prompt is printed after the time when the command is
scheduled. It is possible to miss the exact time when the
command is to be run, but an overdue command will execute at
the next prompt. A command which comes due while the shell is
waiting for user input is executed immediately. However,
normal operation of an already-running command will not be
interrupted so that a scheduled-event list element may be run.
This mechanism is similar to, but not the same as, the at(1)
command on some Unix systems. Its major disadvantage is that
it may not run a command at exactly the specified time. Its
major advantage is that because sched runs directly from the
shell, it has access to shell variables and other structures.
This provides a mechanism for changing one's working
environment based on the time of day.
set
set name ...
set name=word ...
set [-r] [-f|-l] name=(wordlist) ... (+)
set name[index]=word ...
set -r (+)
set -r name ... (+)
set -r name=word ... (+)
The first form of the command prints the value of all shell
variables. Variables which contain more than a single word
print as a parenthesized word list. The second form sets name
to the null string. The third form sets name to the single
word. The fourth form sets name to the list of words in
wordlist. In all cases the value is command and filename
expanded. If -r is specified, the value is set read-only. If
-f or -l are specified, set only unique words keeping their
order. -f prefers the first occurrence of a word, and -l the
last. The fifth form sets the index'th component of name to
word; this component must already exist. The sixth form lists
only the names of all shell variables that are read-only. The
seventh form makes name read-only, whether or not it has a
value. The eighth form is the same as the third form, but make
name read-only at the same time.
These arguments can be repeated to set and/or make read-only
multiple variables in a single set command. Note, however,
that variable expansion happens for all arguments before any
setting occurs. Note also that `=' can be adjacent to both
name and word or separated from both by whitespace, but cannot
be adjacent to only one or the other. See also the unset
builtin command.
setenv [name [value]]
Without arguments, prints the names and values of all
environment variables. 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)).
termname [terminal type] (+)
Tests if terminal type (or the current value of TERM if no
terminal type is given) has an entry in the hosts termcap(5) or
terminfo(5) database. Prints the terminal type to stdout and
returns 0 if an entry is present otherwise returns 1.
time [command]
Executes command (which must be a simple command, not an alias,
a pipeline, a command list or a parenthesized command list) and
prints a time summary as described under the time variable. If
necessary, an extra shell is created to print the time
statistic when the command completes. Without command, prints
a time summary for the current shell and its children.
umask [value]
Sets the file creation mask to value, which is given in octal.
Common values for the mask are 002, giving all access to the
group and read and execute access to others, and 022, giving
read and execute access to the group and others. Without
value, prints the current file creation mask.
unalias pattern
Removes all aliases whose names match pattern. `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 [-hf] [resource]
Removes the limitation on resource or, if no resource is
specified, all resource limitations. With -h, the
corresponding hard limits are removed. Only the super-user may
do this. Note that unlimit may not exit successful, since most
systems do not allow descriptors to be unlimited. With -f
errors are ignored.
unset pattern
Removes all variables whose names match pattern, unless they
are read-only. `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.
jobcmd Runs before each command gets executed, or when the command
changes state. This is similar to postcmd, but it does not
print builtins.
> alias jobcmd 'echo -n "^[]2\;\!#:q^G"'
then executing vi foo.c will put the command string in the
xterm title bar.
helpcommand
Invoked by the run-help editor command. The command name for
which help is sought is passed as sole argument. For example,
if one does
> alias helpcommand '\!:1 --help'
then the help display of the command itself will be invoked,
using the GNU help calling convention. Currently there is no
easy way to account for various calling conventions (e.g., the
customary Unix `-h'), except by using a table of many commands.
periodic
Runs every tperiod minutes. This provides a convenient means
for checking on common but infrequent changes such as new mail.
For example, if one does
> set tperiod = 30
> alias periodic checknews
then the checknews(1) program runs every 30 minutes. If
periodic is set but tperiod is unset or set to 0, periodic
behaves like precmd.
precmd Runs just before each prompt is printed. For example, if one
does
> alias precmd date
then date(1) runs just before the shell prompts for each
command. There are no limits on what precmd can be set to do,
but discretion should be used.
postcmd Runs before each command gets executed.
> alias postcmd 'echo -n "^[]2\;\!#:q^G"'
then executing vi foo.c will put the command string in the
xterm title bar.
shell Specifies the interpreter for executable scripts which do not
themselves specify an interpreter. The first word should be a
full path name to the desired interpreter (e.g., `/bin/csh' or
`/usr/local/bin/tcsh').
Special shell variables
The variables described in this section have special meaning to the
shell.
The shell sets addsuffix, argv, autologout, csubstnonl, command,
echo_style, edit, gid, group, home, loginsh, oid, path, prompt,
prompt2, prompt3, shell, shlvl, tcsh, term, tty, uid, user and version
at startup; they do not change thereafter unless changed by the user.
The shell updates cwd, dirstack, owd and status when necessary, and
sets logout on logout.
The shell synchronizes group, home, path, shlvl, term and user with the
environment variables of the same names: whenever the environment
variable changes the shell changes the corresponding shell variable to
match (unless the shell variable is read-only) and vice versa. Note
that although cwd and PWD have identical meanings, they are not
synchronized in this manner, and that the shell automatically
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. If this is set to
onlyhistory, then only history will be expanded and a second
completion will expand filenames.
autolist (+)
If set, possibilities are listed after an ambiguous completion.
If set to `ambiguous', possibilities are listed only when no
new characters are added by completion.
autologout (+)
The first word is the number of minutes of inactivity before
automatic logout. The optional second word is the number of
minutes of inactivity before automatic locking. When the shell
automatically logs out, it prints `auto-logout', sets the
variable logout to `automatic' and exits. When the shell
automatically locks, the user is required to enter 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.
autorehash (+)
If set, the internal hash table of the contents of the
directories in the path variable will be recomputed if a
command is not found in the hash table. In addition, the list
of available commands will be rebuilt for each command
completion or spelling correction attempt if set to `complete'
or `correct' respectively; if set to `always', this will be
done for both cases.
backslash_quote (+)
If set, backslashes (`\') always quote `\', `'', and `"'. This
may make complex quoting tasks easier, but it can cause syntax
errors in csh(1) scripts.
catalog The file name of the message catalog. If set, tcsh use
`tcsh.${catalog}' as a message catalog instead of default
`tcsh'.
cdpath A list of directories in which cd should search for
subdirectories if they aren't found in the current directory.
color If set, it enables color display for the builtin ls-F and it
passes --color=auto to ls. Alternatively, it can be set to
only ls-F or only ls to enable color to only one command.
Setting it to nothing is equivalent to setting it to (ls-F ls).
colorcat
If set, it enables color escape sequence for NLS message files.
And display colorful NLS messages.
command (+)
If set, the command which was passed to the shell with the -c
flag (q.v.).
compat_expr (+)
If set, the shell will evaluate expressions right to left, like
the original csh.
complete (+)
If set to `igncase', the completion becomes case insensitive.
If set to `enhance', completion ignores case and considers
hyphens and underscores to be equivalent; it will also treat
periods, hyphens and underscores (`.', `-' and `_') as word
separators. If set to `Enhance', completion matches uppercase
and underscore characters explicitly and matches lowercase and
hyphens in a case-insensivite manner; it will treat periods,
hypens and underscores as word separators.
continue (+)
If set to a list of commands, the shell will continue the
listed commands, instead of starting a new one.
continue_args (+)
Same as continue, but the shell will execute:
echo `pwd` $argv > ~/.<cmd>_pause; %<cmd>
correct (+)
If set to `cmd', commands are automatically spelling-corrected.
If set to `complete', commands are automatically completed. If
set to `all', the entire command line is corrected.
csubstnonl (+)
If set, newlines and carriage returns in command substitution
are replaced by spaces. Set by default.
cwd The full pathname of the current directory. See also the
dirstack and owd shell variables.
dextract (+)
If set, `pushd +n' extracts the nth directory from the
directory stack rather than rotating it to the top.
dirsfile (+)
The default location in which `dirs -S' and `dirs -L' look for
a history file. If unset, ~/.cshdirs is used. Because only
~/.tcshrc is normally sourced before ~/.cshdirs, dirsfile
should be set in ~/.tcshrc rather than ~/.login.
dirstack (+)
An array of all the directories on the directory stack.
`$dirstack[1]' is the current working directory, `$dirstack[2]'
the first directory on the stack, etc. Note that the current
working directory is `$dirstack[1]' but `=0' in directory stack
substitutions, etc. One can change the stack arbitrarily by
setting dirstack, but the first element (the current working
directory) is always correct. See also the cwd and owd shell
variables.
dspmbyte (+)
Has an effect iff 'dspm' is listed as part of the version shell
variable. If set to `euc', it enables display and editing EUC-
kanji(Japanese) code. If set to `sjis', it enables display and
editing Shift-JIS(Japanese) code. If set to `big5', it enables
display and editing Big5(Chinese) code. If set to `utf8', it
enables display and editing Utf8(Unicode) code. If set to the
following format, it enables display and editing of original
multi-byte code format:
> set dspmbyte = 0000....(256 bytes)....0000
The table requires just 256 bytes. Each character of 256
characters corresponds (from left to right) to the ASCII codes
0x00, 0x01, ... 0xff. Each character is set to number 0,1,2
and 3. Each number has the following meaning:
0 ... not used for multi-byte characters.
1 ... used for the first byte of a multi-byte character.
2 ... used for the second byte of a multi-byte character.
3 ... used for both the first byte and second byte of a
multi-byte character.
Example:
If set to `001322', the first character (means 0x00 of the
ASCII code) and second character (means 0x01 of ASCII code) are
set to `0'. Then, it is not used for multi-byte characters.
The 3rd character (0x02) is set to '1', indicating that it is
used for the first byte of a multi-byte character. The 4th
character(0x03) is set '3'. It is used for both the first byte
and the second byte of a multi-byte character. The 5th and 6th
characters (0x04,0x05) are set to '2', indicating that they are
used for the second byte of a multi-byte character.
The GNU fileutils version of ls cannot display multi-byte
filenames without the -N ( --literal ) option. If you are
using this version, set the second word of dspmbyte to "ls".
If not, for example, "ls-F -l" cannot display multi-byte
filenames.
Note:
This variable can only be used if KANJI and DSPMBYTE has been
defined at compile time.
dunique (+)
If set, pushd removes any instances of name from the stack
before pushing it onto the stack.
echo If set, each command with its arguments is echoed just before
it is executed. For non-builtin commands all expansions occur
before echoing. Builtin commands are echoed before command and
filename substitution, because these substitutions are then
done selectively. Set by the -x command line option.
echo_style (+)
The style of the echo builtin. May be set to
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 the local system default. The BSD and System
V options are described in the echo(1) man pages on the
appropriate systems.
edit (+)
If set, the command-line editor is used. Set by default in
interactive shells.
ellipsis (+)
If set, the `%c'/`%.' and `%C' prompt sequences (see the prompt
shell variable) indicate skipped directories with an ellipsis
(`...') instead of `/<skipped>'.
euid (+)
The user's effective user ID.
euser (+)
The first matching passwd entry name corresponding to the
effective user ID.
fignore (+)
Lists file name suffixes to be ignored by completion.
filec In tcsh, completion is always used and this variable is ignored
by default. If edit is unset, then the traditional csh
completion is used. If set in csh, filename completion is
used.
gid (+) The user's real group ID.
globdot (+)
If set, wild-card glob patterns will match files and
directories beginning with `.' except for `.' and `..'
globstar (+)
If set, the `**' and `***' file glob patterns will match any
string of characters including `/' traversing any existing sub-
directories. (e.g. `ls **.c' will list all the .c files in
the current directory tree). If used by itself, it will match
match zero or more sub-directories (e.g. `ls
/usr/include/**/time.h' will list any file named `time.h' in
the /usr/include directory tree; whereas `ls
/usr/include/**time.h' will match any file in the /usr/include
directory tree ending in `time.h'). To prevent problems with
recursion, the `**' glob-pattern will not descend into a
symbolic link containing a directory. To override this, use
`***'
group (+)
The user's group name.
highlight
If set, the incremental search match (in i-search-back and i-
search-fwd) and the region between the mark and the cursor are
highlighted in reverse video.
Highlighting requires more frequent terminal writes, which
introduces extra overhead. If you care about terminal
performance, you may want to leave this unset.
histchars
A string value determining the characters used in History
substitution (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. Note that the `prev' and
`all' options renumber history events so there are no gaps.
histfile (+)
The default location in which `history -S' and `history -L'
look for a history file. If unset, ~/.history is used.
histfile is useful when sharing the same home directory between
different machines, or when saving separate histories on
different terminals. Because only ~/.tcshrc is normally
sourced before ~/.history, histfile should be set in ~/.tcshrc
rather than ~/.login.
histlit (+)
If set, builtin and editor commands and the savehist mechanism
use the literal (unexpanded) form of lines in the history list.
See also the toggle-literal-history editor command.
history The first word indicates the number of history events to save.
The optional second word (+) indicates the format in which
history is printed; if not given, `%h\t%T\t%R\n' is used. The
format sequences are described below under prompt; note the
variable meaning of `%R'. Set to `100' by default.
home Initialized to the home directory of the invoker. The filename
expansion of `~' refers to this variable.
ignoreeof
If set to the empty string or `0' and the input device is a
terminal, the end-of-file command (usually generated by the
user by typing `^D' on an empty line) causes the shell to print
`Use "exit" to leave tcsh.' instead of exiting. This prevents
the shell from accidentally being killed. Historically this
setting exited after 26 successive EOF's to avoid infinite
loops. If set to a number n, the shell ignores n - 1
consecutive end-of-files and exits on the nth. (+) If unset,
`1' is used, i.e., the shell exits on a single `^D'.
implicitcd (+)
If set, the shell treats a directory name typed as a command as
though it were a request to change to that directory. If set
to verbose, the change of directory is echoed to the standard
output. This behavior is inhibited in non-interactive shell
scripts, or for command strings with more than one word.
Changing directory takes precedence over executing a like-named
command, but it is done after alias substitutions. Tilde and
variable expansions work as expected.
inputmode (+)
If set to `insert' or `overwrite', puts the editor into that
input mode at the beginning of each line.
killdup (+)
Controls handling of duplicate entries in the kill ring. If
set to `all' only unique strings are entered in the kill ring.
If set to `prev' and the last killed string is the same as the
current killed string, then the current string is not entered
in the ring. If set to `erase' and the same string is found in
the kill ring, the old string is erased and the current one is
inserted.
killring (+)
Indicates the number of killed strings to keep in memory. Set
to `30' by default. If unset or set to less than `2', the
shell will only keep the most recently killed string. Strings
are put in the killring by the editor commands that delete
(kill) strings of text, e.g. backward-delete-word, kill-line,
etc, as well as the copy-region-as-kill command. The yank
editor command will yank the most recently killed string into
the command-line, while yank-pop (see Editor commands) can be
used to yank earlier killed strings.
listflags (+)
If set to `x', `a' or `A', or any combination thereof (e.g.,
`xA'), they are used as flags to ls-F, making it act like `ls
-xF', `ls -Fa', `ls -FA' or a combination (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 A list of files and directories to check for incoming mail,
optionally preceded by a numeric word. Before each prompt, if
10 minutes have passed since the last check, the shell checks
each file and 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, 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.
noding If set, disable the printing of `DING!' in the prompt time
specifiers at the change of hour.
noglob If set, Filename substitution and Directory stack substitution
(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.
padhour If set, enable the printing of padding '0' for hours, in 24 and
12 hour formats. E.G.: 07:45:42 vs. 7:45:42.
parseoctal
To retain compatibily with older versions numeric variables
starting with 0 are not interpreted as octal. Setting this
variable enables proper octal parsing.
path A list of directories in which to look for executable commands.
A null word specifies the current directory. If there is no
path variable then only full path names will execute. path is
set by the shell at startup from the PATH environment variable
or, if PATH does not exist, to a system-dependent default
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.
%N The effective user name.
%j The number of jobs.
%d The weekday in `Day' format.
%D The day in `dd' format.
%w The month in `Mon' format.
%W The month in `mm' format.
%y The year in `yy' format.
%Y The year in `yyyy' format.
%l The shell's tty.
%L Clears from the end of the prompt to end of the display or
the end of the line.
%$ Expands the shell or environment variable name immediately
after the `$'.
%# `>' (or the first character of the promptchars shell
variable) for normal users, `#' (or the second character of
promptchars) for the superuser.
%{string%}
Includes string as a literal escape sequence. It should be
used only to change terminal attributes and should not move
the cursor location. This cannot be the last sequence in
prompt.
%? The return code of the command executed just before the
prompt.
%R In prompt2, the status of the parser. In prompt3, the
corrected string. In history, the history string.
`%B', `%S', `%U' and `%{string%}' are available in only eight-
bit-clean shells; see the version shell variable.
The bold, standout and underline sequences are often used to
distinguish a superuser shell. For example,
> set prompt = "%m [%h] %B[%@]%b [%/] you rang? "
tut [37] [2:54pm] [/usr/accts/sys] you rang? _
If `%t', `%@', `%T', `%p', or `%P' is used, and noding is not
set, then print `DING!' on the change of hour (i.e, `:00'
minutes) instead of the actual time.
Set by default to `%# ' in interactive shells.
prompt2 (+)
The string with which to prompt in while and foreach loops and
after lines ending in `\'. The same format sequences may be
used as in prompt (q.v.); note the variable meaning of `%R'.
Set by default to `%R? ' in interactive shells.
prompt3 (+)
The string with which to prompt when confirming automatic
spelling correction. The same format sequences may be used as
in prompt (q.v.); note the variable meaning of `%R'. Set by
default to `CORRECT>%R (y|n|e|a)? ' in interactive shells.
promptchars (+)
If set (to a two-character string), the `%#' formatting
sequence in the prompt shell variable is replaced with the
first character for normal users and the second character for
the superuser.
pushdtohome (+)
If set, pushd without arguments does `pushd ~', like cd.
pushdsilent (+)
If set, pushd and popd do not print the directory stack.
recexact (+)
If set, completion completes on an exact match even if a longer
match is possible.
recognize_only_executables (+)
If set, command listing displays only files in the path that
are executable. Slow.
rmstar (+)
If set, the user is prompted before `rm *' is executed.
rprompt (+)
The string to print on the right-hand side of the screen (after
the command input) when the prompt is being displayed on the
left. It recognizes the same formatting characters as prompt.
It will automatically disappear and reappear as necessary, to
ensure that command input isn't obscured, and will appear only
if the prompt, command input, and itself will fit together on
the first line. If edit isn't set, then rprompt will be
printed after the prompt and before the command input.
savedirs (+)
If set, the shell does `dirs -S' before exiting. If the first
word is set to a number, at most that many directory stack
entries are saved.
savehist
If set, the shell does `history -S' before exiting. If the
first word is set to a number, at most that many lines are
saved. (The number 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, unless the variable
anyerror is set, and any error in a pipeline or a backquote
expansion will be propagated (this is the default csh behavior,
and the current tcsh default). 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
affects only builtin commands and filename completion.
If set to `expand', the shell tries to fix symbolic links by
actually expanding arguments which look like path names. This
affects any command, not just builtins. Unfortunately, this
does not work for hard-to-recognize filenames, such as those
embedded in command options. Expansion may be prevented by
quoting. While this setting is usually the most convenient, it
is sometimes misleading and sometimes confusing when it fails
to recognize an argument which should be expanded. A
compromise is to use `ignore' and use the editor command
normalize-path (bound by default to ^X-n) when necessary.
Some examples are in order. First, let's set up some play
directories:
> cd /tmp
> mkdir from from/src to
> ln -s from/src to/dst
Here's the behavior with symlinks unset,
> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/from
here's the behavior with symlinks set to `chase',
> cd /tmp/to/dst; echo $cwd
/tmp/from/src
> cd ..; echo $cwd
/tmp/from
here's the behavior with symlinks set to `ignore',
> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/to
and here's the behavior with symlinks set to `expand'.
> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ..; echo $cwd
/tmp/to
> cd /tmp/to/dst; echo $cwd
/tmp/to/dst
> cd ".."; echo $cwd
/tmp/from
> /bin/echo ..
/tmp/to
> /bin/echo ".."
..
Note that `expand' expansion 1) works just like `ignore' for
builtins like cd, 2) is prevented by quoting, 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
wide The shell is multibyte encoding clean (like UTF-8)
nls The system's NLS is used; default for systems with NLS
lf Login shells execute /etc/csh.login before instead of
after /etc/csh.cshrc and ~/.login before instead of after
~/.tcshrc and ~/.history.
dl `.' is put last in path for security; default
nd `.' is omitted from path for security
vi vi-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 if appropriate according to locale
settings, 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 on only systems that store the remote
hostname in /etc/utmp. If unset, `%n has %a %l from %m.' is
used, or `%n has %a %l.' on systems which don't store the
remote hostname.
wordchars (+)
A list of non-alphanumeric characters to be considered part of
a word by the forward-word, backward-word etc., editor
commands. If unset, `*?_-.[]~=' 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.
LS_COLORS
The format of this variable is reminiscent of the termcap(5)
file format; a colon-separated list of expressions of the form
"xx=string", where "xx" is a two-character variable name. The
variables with their associated defaults are:
no 0 Normal (non-filename) text
fi 0 Regular file
di 01;34 Directory
ln 01;36 Symbolic link
pi 33 Named pipe (FIFO)
so 01;35 Socket
do 01;35 Door
bd 01;33 Block device
cd 01;32 Character device
ex 01;32 Executable file
mi (none) Missing file (defaults to fi)
or (none) Orphaned symbolic link (defaults to ln)
lc ^[[ Left code
rc m Right code
ec (none) End code (replaces lc+no+rc)
You need to include only the variables you want to change from
the default.
File names can also be colorized based on filename extension.
This is specified in the LS_COLORS variable using the syntax
"*ext=string". For example, using ISO 6429 codes, to color all
C-language source files blue you would specify "*.c=34". This
would color all files ending in .c in blue (34) color.
Control characters can be written either in C-style-escaped
notation, or in stty-like ^-notation. The C-style notation
adds ^[ for Escape, _ for a normal space character, and ? for
Delete. In addition, the ^[ escape character can be used to
override the default interpretation of ^[, ^, : and =.
Each file will be written as <lc> <color-code> <rc> <filename>
<ec>. If the <ec> code is undefined, the sequence <lc> <no>
<rc> will be used instead. This is generally more convenient
to use, but less general. The left, right and end codes are
provided so you don't have to type common parts over and over
again and to support weird terminals; you will generally not
need to change them at all unless your terminal does not use
ISO 6429 color sequences but a different system.
If your terminal does use ISO 6429 color codes, you can compose
the type codes (i.e., all except the lc, rc, and ec codes) from
numerical commands separated by semicolons. The most common
commands are:
0 to restore default color
1 for brighter colors
4 for underlined text
5 for flashing text
30 for black foreground
31 for red foreground
32 for green foreground
33 for yellow (or brown) foreground
34 for blue foreground
35 for purple foreground
36 for cyan foreground
37 for white (or gray) foreground
40 for black background
41 for red background
42 for green background
43 for yellow (or brown) background
44 for blue background
45 for purple background
46 for cyan background
47 for white (or gray) background
Not all commands will work on all systems or display devices.
A few terminal programs do not recognize the default end code
properly. If all text gets colorized after you do a directory
listing, try changing the no and fi codes from 0 to the
numerical codes for your standard fore- and background colors.
MACHTYPE (+)
The machine type (microprocessor class or machine model), as
determined at compile time.
NOREBIND (+)
If set, printable characters are not rebound to self-insert-
command. See Native Language System support.
OSTYPE (+)
The operating system, as determined at compile time.
PATH A colon-separated list of directories in which to look for
executables. Equivalent to the path shell variable, but in a
different format.
PWD (+) Equivalent to the cwd shell variable, but not 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/.logout. (+)
~/.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-management 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.
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 and
does not handle control characters in filenames well. It cannot be
interrupted.
Command substitution supports multiple commands and conditions, but not
cycles or backward gotos.
Report bugs at http://bugs.gw.com/, preferably with fixes. If you want
to help maintain and test tcsh, send mail to tcsh-request@mx.gw.com
with the text `subscribe tcsh' on a line by itself in the body.
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, Massachusetts 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
The system limits argument lists to ARG_MAX 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 6.18.01 (Astron) 2012-02-14.
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 space bar 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. Added autoconf
support.
Mark Linderman, Cornell University, 1992
OS/2 port
Mika Liljeberg, liljeber@kruuna.Helsinki.FI, 1992
Linux port
Tim P. Starrin, NASA Langley Research Center Operations, 1993
Read-only variables
Dave Schweisguth, Yale University, 1993-4
New man page and tcsh.man2html
Larry Schwimmer, Stanford University, 1993
AFS and HESIOD patches
Luke Mewburn, RMIT University, 1994-6
Enhanced directory printing in prompt, added ellipsis and rprompt.
Edward Hutchins, Silicon Graphics Inc., 1996
Added implicit cd.
Martin Kraemer, 1997
Ported to Siemens Nixdorf EBCDIC machine
Amol Deshpande, Microsoft, 1997
Ported to WIN32 (Windows/95 and Windows/NT); wrote all the missing
library and message catalog code to interface to Windows.
Taga Nayuta, 1998
Color ls additions.
THANKS TO
Bryan Dunlap, Clayton Elwell, Karl Kleinpaste, Bob Manson, Steve Romig, Diana Smetters, Bob Sutterfield, Mark Verber, Elizabeth Zwicky and all the other people at Ohio State for suggestions and encouragement All the people on the net, for putting up with, reporting bugs in, and suggesting new additions to each and every version Richard M. Alderson III, for writing the `T in tcsh' section
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