“ps aux” works but “ps -aux” doesn't

Question

This might seem like a silly question but I haven\'t been able to find a clear answer.

This website states that the dash is optional in

ps aux
         


        

Answer 1

Back in the day (from the late 1970s), there were basically two varieties of UNIX, the AT&T version from Bell Labs and the BSD version from UC Berkeley. The options to ps were different in the two versions. OS X now mostly conforms to the modern UNIX standard which follows the AT&T options to ps. But since the BSD ps didn't require a leading '-' option and so many people were used to typing 'ps aux', Apple has decided to leave that sequence with its original BSD interpretation.