To find out which shells are available on the Unix or Linux system, we can use the cat command to display the contents of the /etc/shells file. This file contains a list of all the shells that are available on the system.  For example:  $ cat /etc/shells
# /etc/shells: valid login shells
/bin/sh
/bin/bash
/usr/bin/sh
/usr/bin/bash
/usr/local/bin/bash  We can also use chsh (change shell) command to see which shells are available and to change the default shell for the user account. For example:  $ chsh
Changing the login shell for username
Enter the new value, or press ENTER for the default
Login Shell [/bin/bash]:  This will display a list of available shells, and we can choose one from the list or enter the path to a different shell. We should know that the list of available shells may vary depending on the specific operating system and version, and may include other shells such as zsh, csh, and more.