iTunes track information in your terminal!

now_playing.rb

# Show iTunes information in real-time in the terminal

def status
  cmd = "osascript -e 'tell application \"iTunes\" to player state'"
  `#{cmd}`
end

def track_name
  cmd = "osascript -e 'tell application \"iTunes\" to name of current track'"
  `#{cmd}`
end

def track_artist
  cmd = "osascript -e 'tell application \"iTunes\" to artist of current track'"
  `#{cmd}`
end

def track_album
  cmd = "osascript -e 'tell application \"iTunes\" to album of current track'"
  `#{cmd}`
end

# Return how far we are into the current track
def position
  cmd = "osascript -e 'tell application \"iTunes\" to player position'"
  pos = `#{cmd}`
  pos.to_i
end

def position_string(pos)
  frac = (pos.to_i)/(60.to_f)
  min  = frac.to_i
  sec  = ((frac - min)*60).ceil
  min = min.to_s
  sec = sec.to_s
  min = ' ' + min if min.size == 1
  sec = '0' + sec if sec.size == 1
  "#{min}:#{sec}"
end

def track_time
  cmd = "osascript -e 'tell application \"iTunes\" to time of current track'"
  `#{cmd}`.to_f
end

def track_length
  cmd = "osascript -e 'tell application \"iTunes\" to duration of current track'"
  len = `#{cmd}`
  len.to_i
end

progress_width = 30
tick_size = 0
len = 0
pos = 0
tick_char = "="
prev_track = ""
loop do
  st = status.strip
  if st == 'playing'
    name = track_name
    if name != prev_track
      # Get info
      artist = track_artist
      album  = track_album

      len        = track_length
      pos        = position
      rem        = (len - pos).abs
      rem_string = position_string(rem)
      pos_string = position_string(pos)
      tick_size  = len / progress_width

      # Display info
      print "\e[1A\e[2K"*4
      puts name, artist, album
      puts "#{pos_string} [#{' '*progress_width}] #{rem_string}"
    else
      pos        = position
      rem        = (len - pos)
      pos_string = position_string(pos)
      rem_string = position_string(rem)
      ticks = (pos / tick_size).floor
      spaces = progress_width - ticks
      print "\e[1A\e[2K"
      puts "#{pos_string} [#{tick_char*ticks}#{' '*spaces}] #{rem_string}"
    end
    prev_track = track_name
  else
    prev_track = ""
  end

  sleep 0.1
end

What does print "\e[1A\e[2K"*4 do? I assume it's allowing you to do the overwriting of the previous info, but what exactly does the \e[1A\e[2K voodoo mean?

Those are terminal control characters; there's a whole bunch of different ones for doing all sorts of things.
"\e[1A" moves the cursor up one line (the command is "\e[nA", where n is the number of lines).
"\e[2K" clears the current line.
That's essentially how I update the progress bar without having to redraw everything.

More information on terminal control characters: http://www.termsys.demon.co.uk/vtansi.htm (note that "\e" is the same as ESC)

Huh, that's nifty. Thanks, I didn't know about those!