| This subsection describes the following: 5.4.1. Variable Substitution In the following substitutions, braces ({ }) are optional, except when needed to separate a variable name from following characters that would otherwise be considered part of the name. Variable | Description |
|---|
${var} | The value of variable var. | ${var[i]} | Select word or words in position i of var. i can be a single number, a range m-n, a range -n (missing m implies 1), a range m- (missing n implies all remaining words), or * (select all words). i also can be a variable that expands to one of these values. | ${#var} | The number of words in var. | ${#argv} | The number of arguments. | $# | Same as ${#argv}. | ${%var} | The number of characters in var. | ${%n} | The number of characters in $argv[n]. | $0 | Name of the program. | ${argv[n]} | Individual arguments on command line (positional parameters); 1  9. | ${n} | Same as ${argv[n]}. | ${argv[*]} | All arguments on command line. | $* | Same as {$argv[*]}. | $argv[$#argv] | The last argument. | ${?var} | Return 1 if var is set; 0 if var is not set. | $?0 | Return 1 if input filename is known, 0 if not. | $$ | Process number of current shell; useful as part of a filename for creating temporary files with unique names. | $? | Same as $status. | $! | Process ID number of last background process started by the shell. | $_ | Text of the command line of the last command executed. | $< | Read a line from standard input. |
5.4.1.1. Examples Sort the third through last arguments and save the output in a file whose name is unique to this process: sort $argv[3-] > tmp.$$
In a .tcshrc file, process commands only if the shell is interactive (i.e., if the prompt variable is set): if ($?prompt) then set commands, alias commands, etc. endif
5.4.2. Variable Modifiers Except for $?var, $?0, $#var, $%var, $#, $$, $?, $!, $_, and $<, the variable substitutions in the preceding section may be followed by one of these modifiers (when braces are used, the modifier goes inside them): :r | Return the variable's root (the portion before the last dot). | :e | Return the variable's extension. | :h | Return the variable's header (the directory portion). | :t | Return the variable's tail (the portion after the last slash). | :gr | Return all roots. | :ge | Return all extensions. | :gh | Return all headers. | :gt | Return all tails. | :q | Quote a wordlist variable, keeping the items separate. Prevents further substitution. Useful when the variable contains filename metacharacters that should not be expanded. | :x | Quote a pattern, expanding it into a wordlist. |
5.4.2.1. Examples using pathname modifiers The following table shows the effect of pathname modifiers if the aa variable is set as follows: set aa=(/progs/num.c /book/chap.ps)
Variable portion | Specification | Output result |
|---|
Normal variable | echo $aa | /progs/num.c /book/chap.ps | | | | | Second root | echo $aa[2]:r | /book/chap | Second header | echo $aa[2]:h | /book | Second tail | echo $aa[2]:t | chap.ps | Second extension | echo $aa[2]:e | ps | | | | | Root | echo $aa:r | /progs/num /book/chap.ps | Global root | echo $aa:gr | /progs/num /book/chap | Header | echo $aa:h | /progs /book/chap.ps | Global header | echo $aa:gh | /progs /book | Tail | echo $aa:t | num.c /book/chap.ps | Global tail | echo $aa:gt | num.c chap.ps | Extension | echo $aa:e | c /book/chap.ps | Global extension | echo $aa:ge | c ps |
5.4.2.2. Examples using quoting modifiers Unless quoted, the shell expands variables to represent files in the current directory: % set a="[a-z]*" A="[A-Z]*" % echo "$a" "$A" [a-z]* [A-Z]* % echo $a $A at cc m4 Book Doc % echo $a:x $A [a-z]* Book Doc % set d=($a:q $A:q) % echo $d at cc m4 Book Doc % echo $d:q [a-z]* [A-Z]* % echo $d[1]+++ $d[2] at cc m4 +++ Book Doc % echo $d[1]:q [a-z]*
5.4.3. Predefined Shell Variables Variables can be set in one of two ways; by assigning a value: set var=value
or by simply turning the variable on: set var
The latter case is useful for simple "Is the variable set?" kinds of tests. In the following list, variables that accept values are shown with the equals sign followed by the type of value they accept; the value is then described. (Note, however, that variables such as argv, cwd, and status are never explicitly assigned.) For variables that are turned on or off, the list describes what they do when set. tcsh automatically sets (and, in some cases, updates) the variables addsuffix, argv, autologout, command, csubstnonl, cwd, dirstack, echo-style, edit, gid, home, loginsh, logout, owd, path, prompt, prompt2, prompt3, shell, shlvl, status, tcsh, term, tty, uid, user, and version.
addsuffix Append / to directories and a space to files during tab completion to indicate a precise match.
afsuser Set value to be used instead of the local username for Kerberos authentication with the autologout locking feature.
ampm Display all times in 12-hour format.
argv=( args) List of arguments passed to current command; default is ( ).
autocorrect Check spelling before attempting to complete commands.
autoexpand Expand history (such as ! references) during command completion.
autolist[=ambiguous] Print possible completions when correct one is ambiguous. If ambiguous is specified, print possible completions only when completion adds no new characters.
autologout=( logout-minutes [ locking-minutes]) Log out after logout-minutes of idle time. Lock the terminal after locking-minutes of idle time, requiring a password before continuing. Not used if the DISPLAY environment variable is set.
backslash_quote Always allow backslashes to quote \, ', and ".
catalog Use tcsh.${catalog} as the filename of the message catalog. The default is tcsh.
cdpath=( dirs) List of alternate directories to search when locating arguments for cd, popd, or pushd.
color Turn on color for ls-F, ls, or both. Setting to nothing is equivalent to setting for both.
colorcat Enable color escape sequence for Native Language System (NLS) support and display NLS messages in color.
command If set, holds the command passed to the shell with the -c option.
complete=enhance If set to enhance, ignore case in completion, treat ., -, and _ as word separators, and consider _ and - to be the same.
continue=( cmdlist) cmdlist is a list of command names. If a stopped job consists of one of the named commands, restart that job when the user enters the corresponding command name, instead of starting a new job.
continue_args=( cmdlist) Like continue, but execute the following: echo 'pwd' $argv > ~/.cmd_pause; %cmd
correct={cmd|complete|all} When cmd, spellcheck commands. When complete, complete commands. When all, spellcheck whole command line.
csubstnonl Newlines and carriage returns in command substitution output are replaced by spaces. Set by default.
cwd= dir Full pathname of current directory.
dextract When set, the pushd command extracts the desired directory and puts it at the top of the stack instead of rotating the stack.
dirsfile= file History file consulted by dirs -S and dirs -L. Default is ~/.cshdirs.
dirstack Directory stack, in array format. dirstack[1] is always equivalent to cwd. The other elements can be artificially changed.
dspmbyte= code Enable use of multibyte code; for use with Kanji. See the tcsh manpage for details.
dunique Make sure that each directory exists only once in the stack.
echo Redisplay each command line before execution; same as tcsh -x.
echo_style={bsd|sysv|both|none} Don't echo a newline with the -n option (bsd), parse escaped characters (sysv), do both, or do neither.
edit Enable command-line editor. Set by default for interactive shells.
ellipsis For use with prompt variable. Use ... to represent skipped directories.
fignore=( suffs) List of filename suffixes to ignore during filename completion.
filec This variable exists for compatibility with the 4.3 BSD csh. By default, it is ignored in tcsh. However, if edit has been unset, then if filec is set a filename that is partially typed on the command line can be expanded to its full name when the Escape key is pressed. If more than one filename matches, type CTRL-D (EOF) to list possible completions.
gid User's group ID.
group User's group name.
histchars= ab A two-character string that sets the characters to use in history-substitution and quick-substitution (default is !^).
histdup={all|prev|erase} Maintain a record only of unique history events (all), do not enter a new event when it is the same as the previous one (prev), or remove an old event that is the same as the new one (erase).
histfile= file History file consulted by history -S and history -L. Default is ~/.history.
histlit Do not expand history lines when recalling them.
history=( n format) The first word indicates the number of commands to save in the history list. The second indicates the format with which to display that list. See the section "Formatting for the Prompt Variable" later in this chapter for possible formats.
home= dir Home directory of user, initialized from the environment variable HOME. The ~ character is shorthand for this value.
ignoreeof Ignore an end-of-file (EOF) from terminals; prevents accidental logout.
implicitcd[=verbose] If a directory name is entered as a command, cd to that directory. Can be set to verbose to echo the cd to standard output.
inputmode={insert|overwrite} Control editor's mode.
killdup={all|prev|erase} Enter only unique strings in the kill ring (all), do not enter a new string when it is the same as the current killed string (prev), or erase from the kill ring an old string that is the same as the current string (erase).
killring= num Set the number of killed strings to keep in memory to num. The default is 30. If unset or set to a number less than two, keep only the most recently killed string.
listflags=( flags [ path]) One or more of the a, A, or x options for the ls-F built-in command. The second word can be set to the path for the ls command.
listjobs[=long] When a job is suspended, list all jobs (in long format, if specified).
listlinks In the ls-F command, include the type of file to which links point (directory, nonexistent file, nondirectory).
listmax= num Do not allow the list-choices editor command to print more than num choices before prompting.
listmaxrows= num Do not allow the list-choices editor command to print more than num rows of choices before prompting.
loginsh Set if shell is a login shell.
logout Indicates status of an imminent logout (normal, automatic, or hangup). Useful in a ~/.logout file.
mail=( n files) One or more files checked for new mail every five minutes or (if n is supplied) every n seconds.
matchbeep={never|nomatch|ambiguous|notunique} Specifies circumstances under which completion should beep: never, if no match exists, if multiple matches exist, or if multiple matches exist and one is exact. If unset, ambiguous is used.
nobeep Disable beeping, such as for ambiguous file completion.
noclobber Don't redirect output to an existing file; prevents accidental destruction of files.
noding Don't print DING! in prompt time specifiers when the hour changes.
noglob Turn off filename expansion; useful in shell scripts.
nokanji Disable Kanji (if supported).
nonomatch Treat filename metacharacters as literal characters if no match exists (e.g., vi ch* creates new file ch* instead of printing "No match").
nostat=( directory-list) Do not stat directory-list during completion.
notify Notify user of completed jobs right away, instead of waiting for the next prompt.
owd Old working directory.
path=( dirs) List of pathnames in which to search for commands to execute. Initialized from PATH; the default is . /usr/ucb /bin /usr/bin. However, standard start-up scripts may change it.
printexitvalue Print all nonzero exit values.
prompt=' str' String that prompts for interactive input; default is %# in interactive shells. See the section "Formatting for the Prompt Variable" later in this chapter for formatting information.
prompt2=' str' String that prompts for interactive input in foreach and while loops and continued lines (those with escaped newlines). See the section "Formatting for the Prompt Variable" for formatting information.
prompt3=' str' String that prompts for interactive input in automatic spelling correction. See the section "Formatting for the Prompt Variable" for formatting information.
promptchars= cc Use the two characters specified as cc with the %# prompt sequence to indicate normal users and the superuser, respectively.
pushdsilent Do not print directory stack when pushd and popd are invoked.
pushdtohome Change to home directory when pushd is invoked without arguments.
recexact Consider completion to be concluded on first exact match.
recognize_only_executables When command completion is invoked, show only executable files.
rmstar Prompt before executing the command rm *.
rprompt= string The string to print on the right side of the screen while the prompt is displayed on the left. The string may have the same special contents as for the prompt variable.
savedirs Execute dirs -S before exiting.
savehist=( max [merge]) Execute history -S before exiting. Save no more than max lines of history. If merge specified, merge those lines with previous history saves, and sort by time.
sched= string Format for sched's printing of events. See the section "Formatting for the Prompt Variable" for formatting information.
shell= file Pathname of the shell program.
shlvl Number of nested shells.
status= n Exit status of last command. Built-in commands return 0 (success) or 1 (failure).
symlinks={chase|ignore|expand} Specify manner in which to deal with symbolic links. Expand them to real directory name in cwd (chase), treat them as real directories (ignore), or expand arguments that resemble pathnames (expand).
tcsh Version of tcsh.
term Terminal type.
time=' n % c' If command execution takes more than n CPU seconds, report user time, system time, elapsed time, and CPU percentage. Supply optional %c flags to show other data. See the tcsh manpage for the details.
tperiod Number of minutes between executions of the periodic alias (described later in this chapter).
tty Name of tty, if applicable.
uid User ID.
user Login name of user, initialized from USER.
verbose Display a command after history substitution; same as tcsh -v.
version Shell's version and additional information, including options set at compile time.
visiblebell Flash screen instead of beeping.
watch=([ n] user terminal...) Watch for user logging in at terminal, where terminal can be a device name or any. Check every n minutes, or 10 by default.
who= string Specify information to be printed by watch. See the tcsh manpage for the details.
wordchars= chars List of all nonalphanumeric characters that may be part of a word. Default is *?_-.[ ]~=.
5.4.4. Formatting for the Prompt Variable tcsh provides a list of substitutions that can be used in formatting the prompt. The list of available substitutions includes: %% | Literal %. | %/ | The present working directory. | %~ | The present working directory, in ~ notation. | %# | # for the superuser, > for others. | %? | Previous command's exit status. | %$var | The value of the shell or environment variable var. | %{string%} | Include string as a literal escape sequence to change terminal attributes (but should not move the cursor location); cannot be the last sequence in the prompt. | \c, ^c | Parse c as in the bindkey built-in command. | %b | End boldfacing. | %B | Begin boldfacing. | %c[[0]n], %.[[0]n] | The last n (default 1) components of the present working directory; if a leading 0 is specified, replace removed components with /<skipped>. | %C | Similar to %c, but use full pathnames instead of ~ notation. | %d | Day of the week (e.g., Mon, Tue). | %D | Day of month (e.g., 09, 10). | %h, %!, ! | Number of current history event. | %j | The number of jobs. | %l | Current tty. | %L | Clear from the end of the prompt to the end of the display or the line. | %m | First component of hostname. | %M | Fully qualified hostname. | %n | Username. | %p | Current time, with seconds (12-hour mode). | %P | Current time, with seconds (24-hour format). | %R | In prompt2, the parser status; in prompt3, the corrected string; and in history, the history string. | %s | End standout mode (reverse video). | %S | Begin standout mode (reverse video). | %t, %@ | Current time (12-hour format). | %T | Current time (24-hour format). | %u | End underlining. | %U | Begin underlining. | %w | Month name (e.g., Jan, Feb). | %W | Month number (e.g., 09, 10). | %y | Year, two digits (e.g., 06, 07). | %Y | Year, four digits (e.g., 2006, 2007). |
5.4.5. Sample .tcshrc File # PREDEFINED VARIABLES set path=(~ ~/bin /usr/ucb /bin /usr/bin) set mail=(/var/mail/tom) if ($?prompt) then # settings for interactive use set echo set noclobber ignoreeof set cdpath=(/usr/lib /var/spool/uucp) # Now I can type cd macros # instead of cd /usr/lib/macros set history=100 set prompt='tom \!% ' # includes history number set time=3 # MY VARIABLES set man1="/usr/share/man/man1" # lets me do cd $man1, ls $man1 set a="[a-z]*" # lets me do vi $a set A="[A-Z]*" # or grep string $A # ALIASES alias c "clear; dirs" # use quotes to protect ; or | alias h "history|more" alias j jobs -l alias ls ls -sFC # redefine ls command alias del 'mv \!* ~/tmp_dir' # a safe alternative to rm endif
5.4.6. Environment Variables tcsh maintains a set of environment variables , which are distinct from shell variables and aren't really part of the shell. Shell variables are meaningful only within the currently running shell, but environment variables are exported automatically, making them available to other programs run by the shell. For example , shell variables are accessible only to the particular script in which they're defined, whereas environment variables can be used by any shell scripts, mail utilities, or editors you might invoke. Environment variables are assigned as follows: setenv VAR value
By convention, environment variable names are all uppercase. You can create your own environment variables, or you can use the predefined environment variables that follow. The following environment variables have corresponding tcsh shell variables. When either one changes, the value is copied to the other. AFSUSER | Alternative to local user for Kerberos authentication with autologout locking; same as afsuser. | GROUP | User's group name; same as group. | HOME | Home directory; same as home. | PATH | Search path for commands; same as path. | SHLVL | Number of nested shell levels; same as shlvl. | TERM | Terminal type; same as term. | USER | User's login name; same as user. |
Other environment variables, which do not have corresponding shell variables, include the following: COLUMNS | Number of columns on terminal. | DISPLAY | Identifies user's display for the X Window System. If set, the shell doesn't set autologout. | EDITOR | Pathname to default editor. See also VISUAL. | EXINIT | A string of ex commands similar to those found in the startup .exrc file (e.g., set ai). Used by vi and ex. See also Chapter 9. | HOST | Name of machine. | HOSTTYPE | Type of machine. Obsolete; will be removed eventually. | HPATH | Colon-separated list of directories to search for documentation for the run-help editor command. | LANG | Preferred language. Used for native language support. | LC_CTYPE | The locale, as it affects character handling. Used for native language support. | LINES | Number of lines on the screen. | LOGNAME | Another name for the USER variable. | LS_COLORS | Colors for use with the ls command. See the tcsh manpage for detailed information. | MACHTYPE | Type of machine. | MAIL | The file that holds mail. Used by mail programs. This is not the same as the shell variable mail, which only checks for new mail. | NOREBIND | Printable characters not rebound. Used for native language support. | OSTYPE | Operating system. | PWD | The current directory; the value is copied from cwd, but only after a directory change. | REMOTEHOST | Machine name of remote host from which the user logged in. | SHELL | Undefined by default; once initialized to shell, the two are identical. | TERMCAP | The file that holds the cursor-positioning codes for your terminal type. Default is /etc/termcap. | VENDOR | System vendor. | VISUAL | Pathname to default full-screen editor. See also EDITOR. |
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