The BSD backend of MacOS has ps built in. The BSD General Commands Manual says that
The biggest change is in the interpretation of the -u option, which now displays processes belonging to the specified username(s). Thus, "ps -aux" will fail (unless you want to know about user "x"). As a convenience, however, "ps aux" still works as it did in Tiger.
I am wondering what the current standard is for this—dare I write—obsolete command+parameter sequence.