The Quixotic Engineer

This winter I took a course called System Software. In it, we learned a neat programming language called Perl. Perl was handy for that class because it happens to be very good at parsing text, and we used it to write a simple compiler. Being the pragmatic kind of person that I am, I immediately began to think of ways to use this new found skill, and the opportunity arose in a rather roundabout way.

You see, I have what I’d describe as a fairly large collection of music (roughly 18.6 days worth according to iTunes). This sometimes causes problems when I’m out shopping for CDs and I can’t quite recall which ones I already own. iTunes is able to export a list of your music as an XML document, but you end up with a large unwieldy file with roughly 15 lines per song.

The solution: create a small Perl script to go through every line of this gigantic XML document and create a list of albums matched with artists. The result of my code monkeying is in the box below. Is the script terribly well written? Not especially. Did my album problem really need solving that badly? Not particularly. Was this a good excuse to play around with Perl a bit? Damn right. Enjoy.

#!/usr/bin/perl
#===========================================
#Script written by Matthew Gallant
#===========================================

$filename = $ARGV[0];
print("Extracting album list from $filename... ");
open(READ, "$filename") ||
die("\nError: $filename not found or cannot be opened.");
my %albums;
my $artist;
while(my $line = <READ>)
{
  if($line =~ m/<key>Artist<\/key&gt/)
  {
    chomp($line);
    $line =~ s/^\s+<key>Artist<\/key&gt<string>//;
    $line =~ s/&#38;/&/;
    $line =~ s/<\/string>//;
    if($line =~ m/^The /)
    {
      $line =~ s/^The //;
      $line = $line . ", The";
    }
    $artist = $line;
  }
  elsif($line =~ m/<key>Album<\/key>/)
  {
    chomp($line);
    $line =~ s/^\s+<key>Album<\/key><string>//;
    $line =~ s/&#38;/&/;
    $line =~ s/ \(Disc \d\)//;
    $line =~ s/<\/string>//;
    if($line ne "N/A")
    {
      my %artistalbums;
      if(exists $albums{$artist})
      {
        my $albumsref = $albums{$artist};
        %artistalbums = %$albumsref;
      }
      $artistalbums{$line} = "";
      $albums{$artist} = \%artistalbums;
    }
  }
}
close(READ);
print("Complete.\n");
print("Writing album list to Album List.txt... ");
open(WRITE, ">Album List.txt") ||
die("\nError: Album List.txt cannot be written to.\n");
for my $key (sort(keys %albums))
{
  $tempkey = $key;
  if($tempkey =~ m/, The$/)
  {
    $tempkey =~ s/, The//;
    $tempkey = "The " . $tempkey;
  }
  printf WRITE ("%-40.39s", $tempkey);
  my $valuesref = $albums{$key};
  my %values = %$valuesref;
  foreach my $album (sort(keys %values))
  {
    print WRITE ("$album\n\t\t\t\t\t");
  }
  print WRITE ("\n");
}
close(WRITE);
print("Complete.");
exit(0);