newgrp

newgrp [-] [group]

Log in to group. If group name is not specified, your original group is reinstated. If - is given, log in using the same environment as when logging in as group. Solaris allows -l as well as -.

This command is also built in to the Bourne and Korn shells. On modern Unix systems that allow users to simultaneously be in multiple groups, this command is obsolete.