GROUPS(1) — UNIX Programmer’s Manual
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 passwd(5) database. and possibly to other groups as specified in the group(5) database. 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
FILES
/etc/passwd, /etc/group - if NetInfo is not running
BUGS
More groups should be allowed.
4.2 Berkeley Distribution — April 29, 1985