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

my $GROUPfile="/etc/group";
my $gfpid = open(GFILE, "<$GROUPfile") or die "$GROUPfile File Not Found: $!\n";
my $PASSWD="/etc/passwd";
my $pfpid = open(PFILE, "<$PASSWD") or die "$PASSWD File Not Found: $!\n";
@PWLINES = <PFILE>;

while (my $line = <GFILE>) {
   @GRP = split(/:/, $line);
   if (length($GRP[3]) < 2){
     print "$GRP[0]:$GRP[2] is zero length\n";

     my @GIDs = map { (split /:/)[3] } @PWLINES;
     my $seen = 0;
     for my $GID (@GIDs) {
        if ($GID == $GRP[2]) {
           $seen = 1
        }
     }
     if (not $seen) {
        print "$GRP[0]:$GRP[2] has no users\n";
     }
   }
}