create_cache_lock (Raggle::Engine)

    # File raggle, line 4999
        def Engine::create_cache_lock
          path = $config['cache_lock_path']

          # open cache lock for writing
          unless $config['cache_lock'] = File::open(path, 'w')
            die "Couldn't open \"#{path}\"."
          end

          # obtain cache lock
          unless $config['cache_lock'].flock(File::LOCK_EX | File::LOCK_NB)
            $stderr.puts "WARNING: Couldn't obtain cache lock: " <<
                         "Another instance of Raggle is running.\n"
            $stderr.puts "WARNING: Disabling feed caching for this instance."
            $stderr.puts "WARNING: Press enter to continue."

            # wait for user response
            $stdin.gets

            # disable feed caching and theme saving
            $config['use_cache_lock'] = false
            $config['save_feed_list'] = false
            $config['save_feed_cache'] = false
            $config['save_theme'] = false
          end
        end