Select random line from IO object

io_ext.rb

# See http://stackoverflow.com/questions/11007111/ruby-whats-an-elegant-way-to-pick-a-random-line-from-a-text-file
class IO
  # Selects a random "line" from a file (might not be a line if different separator is passed).
  # @param *args Same arguments as IO.foreach
  # @return A random line from the IO object
  def self.random_line(*args)
    chosen_line = nil
    self.foreach(*args).each_with_index do |line, number|
      chosen_line = line if rand < 1.0/(number+1)
    end
    chosen_line
  end
end