$)      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.  (Mnemonic: parentheses  are  used  to
             GROUP things.  The effective gid is the group that's
             RIGHT for you, if you're running setgid.)

             Note: $<, $>, $( and $) can only be set on  machines
             that  support the corresponding set[re][ug]id() rou-
             tine.  $( and $) can only  be  swapped  on  machines
             supporting setregid().