#!/usr/bin/perl -w
#<UnusedGrp.pl> Find unused Groups in /etc/group
use strict;

my $GROUPfile="/etc/group";
my $gfpid = open(GFILE, "<", $GROUPfile) or die "$GROUPfile Open failed: $!\n";
my $PASSWD="/etc/passwd";
my $pfpid = open(PFILE, "<", $PASSWD) or die "$PASSWD Open failed: $!\n";

my %gids;
while (my $line = <PFILE>) {
    my @user = split /:/, $line;
    $gids{$user[3]}++;
}


while (my $line = <GFILE>) {
   my @GRP = split(/:/, $line);

   if (length $GRP[3] > 1) { # $GRP[0]:$GRP[2] is not zero length
      next;
   }

   if ($gids{$GRP[2]}) { # GID found in passwd
      next;
   }

   print "$GRP[0] has no users and no GID references\n"
}