=over
=item $EFFECTIVE_GROUP_ID
=item $EGID
=item $)
The effective gid of this process. If you are on a machine that
supports membership in multiple groups simultaneously, gives a space
separated list of groups you are in. The first number is the one
returned by getegid(), and the subsequent ones by getgroups(), one of
which may be the same as the first number.
Similarly, a value assigned to C<$)> must also be a space-separated
list of numbers. The first number sets the effective gid, and
the rest (if any) are passed to setgroups(). To get the effect of an
empty list for setgroups(), just repeat the new effective gid; that is,
to force an effective gid of 5 and an effectively empty setgroups()
list, say C< $) = "5 5" >.
You can change both the effective gid and the real gid at the same
time by using POSIX::setgid() (use only a single numeric argument).
(Mnemonic: parentheses are used to I things. The effective gid
is the group that's I for you, if you're running setgid.)
C<< $< >>, C<< $> >>, C<$(> and C<$)> can be set only on
machines that support the corresponding I routine. C<$(>
and C<$)> can be swapped only on machines supporting setregid().
=back