Need to use newgrp or equivalent

[Guy Harris]

>Assuming you are using the standard /bin/sh, turning on the setuid bit
>of /bin/newgrp is unlikely to have any impact since the newgrp command
>is a built-in command (also built-in in ksh).

A built-in command that "exec"s "newgrp" as its last act; unless your
shell is itself set-UID, it's unlikely to be able to change your
effective group ID (unless your OS lets you do this without root
privileges, and most UNIX versions will, at most, let you change it to
match your real group ID or, in systems that support it, your saved
set-group ID).  So turning on the set-UID bit *could* have an impact.