||It has been suggested that this article be merged into C shell. (Discuss) Proposed since May 2011.|
Screenshot of a sample tcsh session
|Developer(s)||Ken Greer, Paul Placeway, Christos Zoulas, et al.|
|Stable release||6.18.00 / January 14, 2012|
tcsh (pronunciation: // "tee-cee-shell", // "tee-shell", or as an acronym "tee cee ess aitch") is a Unix shell based on and compatible with the C shell (csh). It is essentially the C shell with programmable command line completion, command-line editing, and a few other features.
The “t” in tcsh comes from the “T” in TENEX, an operating system which inspired Ken Greer at Carnegie Mellon University, the author of tcsh, with its command-completion feature. Greer began working on his code to implement Tenex-style file name completion in September 1975, finally merging it into the C shell in December 1981. Mike Ellis at Fairchild A.I. Labs added command completion in September 1983. On October 3, 1983, Greer posted source to the net.sources newsgroup.
Paul Placeway from Ohio State University continued work on it in the 1980s, and since then it has been maintained by numerous people. Wilfredo Sanchez, the former lead engineer of Mac OS X, worked on tcsh in the early 1990s at MIT.
Significant features 
- Command history
- The built-in
historycommand displays the previously-entered commands
- Use of ↑ / ↓ at the command line to allow the user to select a command from the history to edit/execute
- Invoking previous commands using command history
!!executes the previous command
!nexecutes the nth command that was previously executed
!-nexecutes the command that was executed n commands ago
!stringexecutes the most recently-executed command that starts with string
!?stringexecutes the most recently-executed command that contains string
- Using history in new commands
!*- refers to all of the arguments from the previous command
!$- refers to the last argument from the previous command
!^- refers to the first argument from the previous command
!:n- refers to the nth argument from the previous command
!:m-n- refers to the mth through nth arguments from the previous command
!:n-$- refers to the nth through the last argument from the previous command
- The built-in
- Command line editing
- Auto-completion of file names and variables at the command line
- Alias argument selectors; the ability to define an alias to take arguments supplied to it and apply them to the commands that it refers to. Tcsh is the only shell that provides this feature.
\!#- argument selector for all arguments, including the alias/command itself; arguments need not be supplied.
\!*- argument selector for all arguments, excluding the alias/command; arguments need not be supplied.
\!$- argument selector for the last argument; argument need not be supplied, but if none is supplied, the alias name is considered to be the last argument.
\!^- argument selector for first argument; argument MUST be supplied.
\!:n- argument selector for the nth argument; argument MUST be supplied; n=0 refers to the alias/command name.
\!:m-n- argument selector for the arguments from the mth to the nth; arguments MUST be supplied.
\!:n-$- argument selector for the arguments from the nth to the last; at least argument n MUST be supplied.
#Alias the cd command so that when you change directories, the contents are immediately displayed. alias cd 'cd \!* && ls'
- Wildcard matching
if ( "$input" =~ [0-9]* ) then echo "the input starts with an integer" else echo "the input does NOT start with an integer" endif
- Job control
- The built-in
wherecommand. Works like the
whichcommand but shows all locations of the target command in the directories specified in
$PATHrather than only the one that will be used.
Early versions of Mac OS X shipped with tcsh as the default shell, but the default for new accounts is bash as of 10.3. (tcsh is still provided, and upgrading the OS does not change the shell of any existing accounts). The tcsh is the default root shell of FreeBSD (the default user shell is POSIX-based) and its descendants like DragonFly BSD and DesktopBSD.
See also