Editing Tcsh (section)

==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 (programming)|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 <code>sh</code> to match the default user shell<ref>{{cite web | url=https://docs.freebsd.org/en/articles/linux-users/ | title=FreeBSD Quickstart Guide for Linux Users }}</ref> whereas [[OpenBSD]] uses the [[Korn shell]] <code>ksh</code> for both root and regular users.<ref>{{cite web | url=https://www.openbsdhandbook.com/openbsd_for_linux_users/ | title=OpenBSD for Linux Users }}</ref>)

tcsh added filename and command completion and command line editing concepts borrowed from the [[TENEX (operating system)|TENEX]] operating system, which is the source of the “t”.<ref name=Greer>
{{Cite newsgroup
| author     = Ken Greer
| title      = C shell with command and filename recognition/completion
| date       = 3 Oct 1983
| newsgroup  = net.sources
| url        = https://groups.google.com/group/net.sources/msg/7073bf41cc5da330?hl=en
| access-date = 29 December 2010
}}</ref>  Because it only added functionality and did not change what was there, tcsh remained [[backward compatible]]<ref>[https://web.archive.org/web/20060117151444/http://www.tcsh.org/tcsh.html/DESCRIPTION.html tcsh(1) man page]. tcsh.</ref> with the original C shell.  Though it started as a side branch from the original csh source tree that [[Bill Joy]] had created, tcsh is now the main branch for ongoing development.

tcsh is very stable but new releases continue to appear roughly once a year, consisting mostly of minor bug fixes.<ref>Fixes file in tcsh-17 June 2000.</ref>

On many systems, such as [[macOS]] and [[Red Hat Linux]], <code>csh</code> is actually <code>tcsh</code>.  Often one of the two files is either a [[hard link]] or a [[symbolic link]] to the other, so that either name refers to the same improved version of the C shell (although behavior may be altered depending on which name is used).

On [[Debian]] and some derivatives (including [[Ubuntu (operating system)|Ubuntu]]), there are two different packages: csh and tcsh. The former is based on the original BSD version of csh<ref>[https://launchpad.net/ubuntu/+source/csh Ubuntu - Details of package csh]. launchpad.net.</ref><ref>[https://tracker.debian.org/pkg/csh Debian - Details of package csh]. tracker.debian.org.</ref> and the latter is the improved tcsh.<ref>[https://launchpad.net/ubuntu/+source/tcsh Ubuntu - Details of package tcsh]. launchpad.net.</ref><ref>[https://tracker.debian.org/pkg/tcsh Debian - Details of package tcsh]. tracker.debian.org.</ref>