High Quality Content by WIKIPEDIA articles tcsh (pronunciation: /ˌtiːˈsiːʃɛl/ "tee-cee-shell," /ˈtiːʃɛl/ "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.