groupmems(8) on Linux
The text 37a9280c89ab, as Debian 11 (Bullseye) shipped it.
administer members of a user's primary group
Flags it lists
-
--add -
--delete -
--group -
--help -
--list -
--purge -
--root -
-R -
-a -
-d -
-g -
-h -
-l -
-p