Where Knowing How to Program Paid Off

So today I was copying the music off of my iPod onto one of my HDDs. All was going well, at least I thought. I went to add a few directories to XMMS to randomize and play when I realized something had gone wrong- no files were added to my play list. On further inspection I learned that the reason behind this is the application I used to extract the songs didn’t give them their .mp3 extension. Come to find out when I was customizing the format for the file names (I’m picky) I had to explicitly define “.%e” or whatever, for the extension.

Whoops.

So I was left with 4,500 tracks and none of them had an extension. Enter: Ruby. After some quick prototyping in the Ruby IRB, I wrote up a quick and dirty script that would loop through my music structure (Music Directory / Artist / Album / <songs>) and add “.mp3″ to the end of every extension. I’ve gone ahead and modified it a little to be less dirty, so I figure I’ll share with you what I have.

#!/usr/bin/ruby
 
class AddMp3Extension
  # Take in the main music directory, slice off the ending slash if it exists,
  # initialize our instance variables and kick off the show.
  #
  #  @param    string    The top level of our music directory
  def initialize(musicDir)
    if musicDir[-1, 1] == "/"
      musicDir = musicDir[0, musicDir.length - 1]
    end
 
    @musicDirectory = musicDir
    @numRenamed = 0
 
    puts "Starting rename process..."
    begin_main_loop
    puts "Rename process complete!  #{@numRenamed} files were renamed."
  end
 
private
 
  # Begin looping through the directory.  Every time we find another
  # directory we'll enter it (it'll be an album) and then rename all
  # the junk inside it.
  def begin_main_loop(dir = @musicDirectory)
    curDir = dir
    curDirContents = Dir.entries(dir)
 
    curDirContents.each do |f|
      unless f == "." || f == ".."
        curFile = "#{curDir/#{f}"
        find_extension = curFile.split(".")
 
        if is_directory?(curFile)
          begin_main_loop(curFile)
        end
 
        if is_file?(curFile) && find_extension.last != "mp3"
          newName = "#{curFile}.mp3"
 
          File.rename(curFile, newName)
          @numRenamed += 1
        end
      end
    end
  end
 
  # Takes a file path and checks to see if it's a directory.  If it
  # is we shoot back a true value.
  #
  #  @param    string    The directory we're interested in
  def is_directory?(dir)
    dir = File.ftype(dir).downcase
 
    if dir == "directory"
      return true
    end
 
    return false
  end
 
  # Check to see if we're working with a file, rather than a directory.
  # If so then more likely than not (barring any user error) we have
  # ourselves an mp3 without its extension.
  #
  #  @param    string    Location of the file we're validating
  def is_file?(file)
    file = File.ftype(file).downcase
 
    if file == "file"
      return true
    end
 
    return false
  end
 
  # Every *nix directory has two special placeholders within it: . and ..
  # So take the current file and make sure it's neither of those.
  #
  #  @param    string    Location of the file we're validating
  def is_special?(file)
    return true if file == "." || file == ".."
 
    return false
  end
end
 
unless ARGV[0].empty?
  begin_renaming = AddMp3Extension.new(ARGV[0])
else
  puts "Correct format: add_mp3_extension "
end

Now I make no claim that this is the best way to accomplish the goal.  Perhaps tomorrow, when I haven’t been up for about 20 hours I’ll write a version that is closer to being production quality.

Either way, just thought I’d share. Later.