UNIX: A Summary of the C Shell

Job Control

allows you to work on several jobs at once, switching back and forth between them as you desire:

Format: command [optional job number]

Command	Meaning
`bg` [`%`job]	execute the job (specified by `%`job - default: current job) in the background
`fg` [`%`job]	run job (specified by `%`job) in foreground
`kill` [signal] [`%`job/PID]	iterminate a process or send a signal. If it fails use `kill -9` [`%`job/PID]
`stop` [`%`job]	stop the job (specified by `%`job)
`suspend`	stop the current shell (like for foreground jobs)
`notify` [`%`job]	notify user immediately on change of status of job (specified by `%`job)
`jobs` [`-l`]	list active and stopped background jobs (with process Ids). Current background job is indicated by '`+`', next by '`-`'
<CTRL>-c	terminate foreground job
<CTRL>-z	suspend foreground job

Job Number	Meaning
`PID`	process ID
`%`	current job
`%`n	job n
`%`str	job with str as command name
`%?`str	job with str anywhere in command string
`%-`	previous job

Example:


  % jobs
  % echo $status
  0
  % prog1 &
  [1] 5913
  % prog2
  % -z
  suspended
  % bg
  [2] 5924
  % jobs
  [1] + 5913 Suspended (tty output) prog1
  [2]   5924 Running                prog2
  % fg
  prog1
  bin fertig
  % jobs
  [2] + 5924 Running                prog2
  % %2
  prog2

C Shell Variables

There are two kinds of C shell variables:

user defined variables
predefined variables

User Defined Variables

Variable modifiers apply to the following (replace var with argv to refer to command line arguments):

variable	meaning
`$`var	value of var
`${`var`}`	value of var, insulate var string
`$`var`[`n`]`	value of nth word from var wordlist
`${`var[n`]}`	value of nth word from var wordlist, insulate var string
`$`var`[*]`	same as `$`var
`$`var`[n-m]`	words n through m from var wordlist
`${`var`[`n`-`m`]}`	words n through m from wordlist, insulate var string
`$`var`[$#`var`]`	last word from var wordlist
`$`var`{[$#`var`]}`	last word from var wordlist, insulate var string
`$`n	same as `$argv[`n`]` (n restricted to 1-9)
`$*`	same as `$argv[*]`
`$#`var	number of words in var
`${#`var`}`	number of words in var, insulate var string

Variable modifiers do not apply to the following:

variable	meaning
`$0`	name of script file
`$?`var	1 if var is defined; 0 if not
`${?`var`}`	1 if var is defined; 0 if not; insulate var string
`$$`	process ID of parent shell
`$!`	process ID of last started background job
`$<`	read a line from stdin (BSD)

Variable modifiers:

Modifier	Meaning
`:e`	extension (BSD)
`:h`	header name
`:r`	root name
`:t`	tail
`:q`	quote
`:x`	quote an expand into individual words
`:g`[`hrtes`]	modify all words in wordlist using specified modifier

Example:


  % set e = 2.718282
  % set p = $HOME
  % echo e
  e
  % echo $e
  2.718282
  % echo $e5
  e5 Undefined variable
  % echo 5$e
  52.718282
  % echo $p$e
  /disk1/users/peter2.718282
  % echo $p5$e
  p5 Undefined variable
  % echo ${p}5$e
  /disk1/users/peter52.718282

Predefined C Shell Variables

Variable	Meaning
`argv`	argument vector Wordlist variable containing the argument list passed to shell scripts. Contains the empty string ( ) by default.
`cdpath`	change directory path (unset by default) Wordlist variable containing the full pathnames of alternate directories to search for arguments to `cd` (and `pushd` and `popd`).
`child`	child process (non-BSD, unset by default) Contains the process ID of the most recently invoked background process. When the process terminates, variable `child` is undefined.
`cwd`	current working directory Contains the full pathname of the current working directory.
`echo`	echo mode (set/unset) When set, each command is displayed just before execution. Commands reflect history, alias, command, filename, and variable substitutions. May enable in a script with the `csh -x` option.
`histchars`	history substitution characters Contains the two history substitution characters. If unset, these characters are ! and ^
`history`	history list size. (unset by default) Contains the number of past commands the shell will store in the history list
`home`	home directory Contains the full pathname of the user's home directory. This variable is initialized by the C shell from the environment variable `HOME`.
`ignoreeof`	ignore end-of-file character (set/unset) When set, the shell will not terminate by reading an end-of-file character from the keyboard (i.e., <CTRL-d>). To logout, use the `logout` command. To exit a child shell, use the `exit` command.
`mail`	mail file Wordlist or single variable containing the pathnames where the C shell checks for mail. If the first word is numeric, the shell checks for mail in that many seconds. The default interval is 10 minutes. If the mail variable contains more than one mail file, the mail message is "New mail in ..."; otherwise the message is "You have new mail." Unset by default, and the shell uses mail file `/usr/spool/spool/mail/$USER` (or `$LOGNAME`)
`noclobber`	do not clobber files (set/unset) When set, the shell prevents redirection commands from overwriting an existing file. It also prevents append commands from creating a file. Use ! to override the `noclobber` option on a single command.
`noglob`	do not allow file expansion (set/unset) When set, filename expansion is inhibited.
`nonomatch`	no error on nonmatching file expansion characters (set/unset) When set, a command containing file expansion characters that do not match any files does not produce an error. If no files match, the command is invoked with the characters unexpanded. When unset, the shell reports an error and does not invoke the command.
`notify`	notify of job completions (set/unset) (BSD) When set, the shell notifies users of job completions asynchronousfy. When unset, notification is just before the prompt.
`path`	command path list Wordlist variable containing the pathnames the shell should search to find commands. The C shell sets path to (`. /bin /usr/bin`) by default. The C shell maintains `path` and the environment variable `PATH` together (`path` is forwarded to `PATH`).
`prompt`	C shell prompt Contains the C shell prompt string. Default value is '% '.
`savehist`	save commands in history list (BSD, unset by default) Contains the number of commands the shell should save upon logout. The shell places these commands back into the active history list automatically at login without executing. them. The commands are stored in file `~/.history`.
`shell`	default shell file Contains the full pathname of the default shell. The shell invokes this program to execute shell scripts. Default value is `/bin/csh`.
`status`	last command status Contains the completion status of the last invoked command. Built-in commands return 0 if successful and 1 if unsuccessful.
`term`	terminal ID (BSD) Contains the name of the terminal type. lnitialized by default to the value in file `/etc/ttytype` corresponding to the `tty` line.
`time`	automatic timing control (unset by default) Contains the maximum number of seconds in CPU time the shell allows a command to consume without reporting usage statistics.
`user`	user's name (BSD) Contains the user's login name. The shell initializes it from the environment variable `USER` (or `LOGNAME`).
`verbose`	verbose mode (set/unset) When set, the shell displays the command after history substitutions but before alias, command, filename, and variable substitutions. May be invoked in shell scripts with the `csh -v` option.