Linux Command Line - Bash Scripting

hadley@hadley-MacBookPro:~$ which bash
/usr/bin/bash
hadley@hadley-MacBookPro:~$ cat /etc/shells 
# /etc/shells: valid login shells
/bin/sh
/bin/bash
/usr/bin/bash
/bin/rbash
/usr/bin/rbash
/bin/dash
/usr/bin/dash