Man1 - groups.1

groups - display current group names

groups [/user/]

The groups 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 parameter 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 or sg to change his current real and effective group ID.

/etc/group

Group account information.

*newgrp*(1), *getgid*(2), *getgroups*(2), *getuid*(2).