Installing bash

You can install a newer bash using brew if you want to go beyond the bash offered by the operating system distributed one from Apple.

Install from Homebrew:

$ brew install bash

Make the new bash interpreter located in /usr/local/bin/ a login shell:

$ sudo echo '/usr/local/bin/bash' >> /etc/shells

Change your personal login shell

$ chsh -s /usr/local/bin/bash

References