I don't understand how that can work.

ps -gu is an illegal option on any server I have seen. If you specify -g or -u, you must suppy a list of groups or users.

Below is the usage doc from ps on our sun system.

usage: ps [ -aAdeflcjLPy ] [ -o format ] [ -t termlist ]
[ -u userlist ] [ -U userlist ] [ -G grouplist ]
[ -p proclist ] [ -g pgrplist ] [ -s sidlist ]

What is the correct string. While I know that this is outside the original scope of the question, I am curious (yellow).