open my $fh, "<$ack_filename" or die "open error: $!";
  my $file_size;
  while (<$fh>) {
    chomp;
    if (m|<file_size>([^<]*)</file_size>|i) {
      $file_size = $1;
      last;
    }
  }
  $fh->close;
  print $file_size;