This code will catch duplicate IDs that are identical. 
#!/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;
   }
}

[download]
I wish also to catch IDs that differ only in case. (ie. root , Root , ROOT) Thanx.

In reply to Re^2: Search a hash case insensitive by Saved
in thread Search a hash case insensitive by Saved

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