id(1) on Linux
The text a090183c1a08, as Debian 1.2 (Rex), Debian 1.1 (Buzz) shipped it.
print real and effective UIDs and GIDs
Flags it lists
-
--group -
--groups -
--help -
--name -
--real -
--user -
--version -
-G -
-g -
-n -
-r -
-u