groups - display current group names
command displays the current group names or ID values. If the
value does not have a corresponding entry in /etc/group, the value will be
displayed as the numerical group value. The optional user
will display the groups for the named user
Systems which do not support concurrent group sets will have the information
from /etc/group reported. The user must use newgrp
change his current real and effective group ID.
Group account information.