instance method tail

# File railties/lib/rails/mongrel_server/commands.rb, line 259
      def tail(log_file)
        cursor = File.size(log_file)
        last_checked = Time.now
        tail_thread = Thread.new do
          File.open(log_file, 'r') do |f|
            loop do
              f.seek cursor
              if f.mtime > last_checked
                last_checked = f.mtime
                contents = f.read
                cursor += contents.length
                print contents
              end
              sleep 1
            end
          end
        end
        tail_thread
      end