Ghetto: Your Solution for Workarounds™

I like to make playlists. But I also reorganize my music something like once or twice a year. Because of that my playlists get broken as they are really just lists of filenames. This past summer I wrote some code in ruby that would find files with the same basename but ignore the directory structure, and reconstruct playlists from that. It worked perfectly except every now and then I would get a live version or two. This works because I have an sqlite database of all of my music thanks to amaroK.

Well, I decided that I would update the script so that I wouldn’t have those issues with live versions. I decided that I would have an intermediate filetype, which I would basically keep around forever. Announcing the FRU media playlist filetype! Actually not that exciting. Anyway, here are a couple scripts:

m3u2fru.pl6:

#!/home/frew/personal/rakudo/perl6

use Ghetto;

for =$*IN -> $line {
   unless $line ~~ /^\#/ {
      my $file = $line.split('/').pop;

      my $cmd = qq{dcop amarok collection query "SELECT title,artist.name,album.name FROM tags JOIN artist ON artist.id = artist  JOIN album ON album.id = album WHERE url LIKE \\"%/$file\\""};
      my ( $track,$artist,$album ) = Ghetto::run($cmd).split("\n");
      say $track;
      say $artist;
      say $album;
      say '--';
   }
}

fru2m3u.pl6:

#!/home/frew/personal/rakudo/perl6

use Ghetto;

for =$*IN -> $track,$artist,$album,$sep {
   my $cmd = qq{dcop amarok collection query "SELECT url FROM tags JOIN artist ON artist.id = artist  JOIN album ON album.id = album WHERE artist.name = \\"$artist\\" and album.name = \\"$album\\" and title = \\"$track\\""};
   # this insanity is to take the first character off because amaroK adds a
   # . to the front of all the file names.  There's probably a better way
   # to do this.
   say Ghetto::run($cmd).split("\n")[0].reverse.chop.reverse;
}

But the more important part, is the Ghetto module. Currently rakudo does not have any way to get the output of a command, but it can read from files, so we can fake it:

module Ghetto;

sub run($cmd) {
   # create a random filename to store output in
   my $tmp = ".tmp-{(1..100).pick}-ghetto";

   # use the real run command, :: means root namespace
   ::run("$cmd > '$tmp'");

   # open the file
   my $data_file = open($tmp, :r);
   
   # put the data from the file into a variable
   my $val;
   for =$data_file { $val ~= "$_\n"; }

   # delete the file
   unlink($tmp);

   #gimme my data!
   return $val;
}

Obviously this is slow, bad in that it could possibly overwrite files, etc. It’s ghetto. But the idea is that later when we actually can do something like this without a ghetto solution it won’t be hard to fix your code.

I also thought it was fun to do a pipe-based solution. The way I had it set up before was something like this:

./plup.rb old.m3u new.m3u

That’s alright, but I would usually look at the output to make sure it was right. Now I do this:

cat old.m3u | ./m3u2fru.pl6 | ./fru2m3u.pl6 > new.m3u

Sure it’s longer, but I can easily see the output at any point in the process. Furthermore, since I am using zsh (maybe bash can do this too, not sure) I can do this:

cat old.m3u | ./m3u2fru.pl6 >new.fru | ./fru2m3u.pl6 > new.m3u

So I can keep the intermediate results for next time!

Posted Sat, Mar 7, 2009

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