GROUPS(1) BSD Reference Manual GROUPS(1)
groups - show group memberships
groups [user]
The groups utility has been obsoleted by the id(1) utility, and is equivalent to id -Gn [user]. The command id -p is suggested for normal interactive use. The groups utility displays the groups to which you (or the optionally specified user) belong. The groups utility exits 0 on success or >0 if an error occurred.
id(1) MirBSD #10-current June 6, 1993 1