sub md5sum{
  my $file = shift;
  my $digest = "";
  eval{
    open(FILE, $file) or die "Can't find file $file\n";
    my $ctx = Digest::MD4->new;
    $ctx->addfile(*FILE);
    $digest = $ctx->hexdigest;
    close(FILE);
  };
  if($@){
    print $@;
    return "";
  }
  return $digest;
}