bsd man page for groups

GROUPS(1)						      General Commands Manual							 GROUPS(1)

NAME
       groups - show group memberships

SYNOPSIS
       groups [user]

DESCRIPTION
       The  groups  command  shows the groups to which you or the optionally specified user belong.  Each user belongs to a group specified in the
       password file /etc/passwd and possibly to other groups as specified in the file /etc/group.  If you do not own a file  but  belong  to  the
       group which it is owned by then you are granted group access to the file.

       When a new file is created it is given the group of the containing directory.

SEE ALSO
       setgroups(2)

FILES
       /etc/passwd, /etc/group

BUGS
       More groups should be allowed.

4.2 Berkeley Distribution					  April 29, 1985							 GROUPS(1)