Change your login shell, either interactively or on the command line. Warn if shell does not exist in /etc/shells. Specify the full path to the shell. chsh prompts for your password. Only a privileged user can change another user’s shell.
Print valid shells, as listed in /etc/shells, and then exit.
Specify new login shell.
Print help message and then exit.
Print version information and then exit.
chsh -s /bin/tcsh