When I wiped my laptop a few updates ago my user login name was my full name (I want it to be shorter in command line to be my first and middle name), how do I change the user login name on this OS, El Capitan 10.11 Beta?
How do I change my user login name on El Capitan?
System Preferences > Users & Groups > Unlock Padlock > right-click your account in the left panel > Click Advanced Options...
For the command line prompt, you need to change the entry next to Account Name. In spite of the warning above, this won't prevent you from accessing your account, but you will need to restart your Mac for the change to take effect.
Let me know how it goes.
-Max