Unix shells include Almquist shell (ash),Bourne shell (B shell, sh), C shell (csh), Bourne Again Shell (bash), Debian Almquist shell (dash), Korn shell (ksh), Public domain Korn shell (pdksh), MirBSD Korn shell (mksh), Z shell (zsh) etc. There are several ways to find out what shell we are using.

$ echo $0
/bin/bash

or

$ ps -p $$
PID TTY TIME CMD
21002 pts/1 00:00:00 bash