changing groups and newgrp

[utzoo!decvax!pur-ee!purdue!mab]

     I use a program called "sg", which acts just like "su" except that  it
changes  groups;  this is a bit better than "newgrp" because if you mistype
your group name or can't change to the given group for any reason you don't
get  logged  off.  It's  basically just like "su", so you lose your history
list (if you're in C-Shell) or any  unexported  environment  variables  (if
you're  in  the Bourne shell). To return to your login group, just exit the
subshell.
     One note: it has to be run as setuid to root. Otherwise, you can't  do
the required setgid.
                                                        Matt