To change your login shell to the Korn shell (ksh):
chsh Changing login shell for sarah. Old shell name: /bin/csh New shell: ksh
This changes the user's login shell from the C shell (csh) to the Korn shell (ksh).
If you mistype the name of the shell or specify a shell that is not available on your system:
or
name is unacceptable as a new shell