#!/usr/bin/perl -w
#<SortPW2.pl> /etc/passwd sort by ID

my $PASSWD="passwd";
my $fpid = open(PFILE, "<$PASSWD") or die "Password File Not Found: $!\n";

my %ids;
while (my $line = <PFILE>) {
   @ID = split(/:/, $line);
   my $id = ${ID[0]};
   if ($ids{$id}) {
       print "'$id' is duplicate\n";
   } else {
      $ids{$id} = 1;
   }
}