#!/usr/bin/perl
use strict;
use warnings;

use Getopt::Std;
my %opt;
Get_Args();

open (MASTER , '<' , $opt{m}) or die "Unable to open $opt{m} as master : $!";
open (SLAVE  , '<' , $opt{s}) or die "Unable to open $opt{s} as slave : $!";
open (OUTPUT , '>' , $opt{o}) or die "Unable to open $opt{o} for output : $!";
select OUTPUT;

my (%master , %slave);
%slave  = map {chomp; $_ => undef} <SLAVE>;

while ( <MASTER> ) {
    chomp;
    print "$_ exists on master but not slave\n" if ! exists $slave{$_};
    $master{$_} = undef;
}

delete @slave{ keys %master };
print "$_ exists on slave but not master\n" for keys %slave;

sub Get_Args {
    my $Usage = qq{Usage: $0 -m <master file> -s <slave file> -o <output file>
        -h : This help message.
        -m : master file
        -s : slave file
        -o : output file
    } . "\n";

    getopts( 'hm:s:o:' , \%opt ) or die $Usage;
    die $Usage if $opt{h} || ! $opt{m} || ! $opt{s} || ! $opt{o};
}