Manage your shells on Linux

To show all your shells, you can run:
$ cat /etc/shells

and to choose one of them 
simpliy run it directory on terminal

ex:$ /bin/bash

for more info we can check: https://bash.cyberciti.biz/guide//etc/shells

to set specific shell as default, we can simiply use 'chsh':
$ chsh -s /bin/bash

To know the current shell: 
$ echo $SHELL


https://www.shellscript.sh/