tcsh

tcsh ( “tee-see-shell”, “tee-shell”, or as “tee see ess aitch”, tcsh) is a Unix shell based on and backward compatible with the C shell (csh).

==Shell== It is essentially the C shell with programmable command-line completion, command-line editing, and a few other features. Unlike the other common shells, functions cannot be defined in a tcsh script and the user must use aliases instead (as in csh). It is the native root shell for some BSD-based systems, including FreeBSD 13 and earlier. (FreeBSD 14 changed the default root shell to sh to match the default user shell whereas OpenBSD uses the Korn shell ksh for both root and regular users.)