base64 encode and decode in terminal on MAC

As an example, base64 encode and decode the following username and password in terminal window on MAC.
Username: superman
Password: superpower

base64 encode:

echo -n 'superman:superpower' | base64

base64 decode:

echo 'c3VwZXJtYW46c3VwZXJwb3dlcg==' | base64 -D