10. Using bzip2 to recompress other compression formats

The following perl program takes files compressed in other formats (.tar.gz, .tgz. .tar.Z, and .Z for this iteration) and repacks them for better compression. The perl source has all kinds of neat documentation on what it does and how it does what it does.

#!/usr/bin/perl -w

#######################################################
#                                                     #
# This program takes compressed and gzipped programs  #
# in the current directory and turns them into bzip2  #
# format.  It handles the .tgz extension in a         #
# reasonable way, producing a .tar.bz2 file.          #
#                                                     #
#######################################################
$counter = 0;
$saved_bytes = 0;
$totals_file = '/tmp/machine_bzip2_total';
$machine_bzip2_total = 0;

while(<*[Zz]>) {
    next if /^bzip2-0.1pl2.tar.gz$/;
    push @files, $_;
}
$total = scalar(@files);

foreach (@files) {
    if (/tgz$/) {
        ($new=$_) =~ s/tgz$/tar.bz2/;
    } else {
        ($new=$_) =~ s/\.g?z$/.bz2/i;
    }
    $orig_size = (stat $_)[7];
    ++$counter;
    print "Repacking $_ ($counter/$total)...\n";
    if ((system "gzip -cd $_ |bzip2 >$new") == 0) {
        $new_size = (stat $new)[7];
        $factor = int(100*$new_size/$orig_size+.5);
        $saved_bytes += $orig_size-$new_size;
        print "$new is about $factor% of the size of $_. :",($factor<100)?')':'(',"\n";
        unlink $_;
    } else {
        print "Arrgghh!  Something happened to $_: $!\n";
    }
}
print "You've ",
      ($saved_bytes>=0)?"saved":"lost",
      " $saved_bytes bytes of storage space :",
       ($saved_bytes>=0)?")":"(", "\n";

unless (-e '/tmp/machine_bzip2_total') {
    system ('echo "0" >/tmp/machine_bzip2_total');
    system ('chmod', '0666', '/tmp/machine_bzip2_total');
}


chomp($machine_bzip2_total = `cat $totals_file`);
open TOTAL, ">$totals_file"
     or die "Can't open system-wide total: $!";
$machine_bzip2_total += $saved_bytes;
print TOTAL $machine_bzip2_total;
close TOTAL;

print "That's a machine-wide total of ",`cat $totals_file`," bytes saved.\n";