newgrp - log in to a new group
newgrp changes the group identification of its caller, analogously to
login(1). The same person remains logged in, and the current directory
is unchanged, but calculations of access permissions to files are performed
with respect to the new group ID.
If no group is specified, the GID is changed to the login GID.
Originally by Michael Haardt. Currently maintained by Peter Orbaek
The newgrp command is part of the util-linux package and is available from