setup_output_dir

# File lib/rdoc/rdoc.rb, line 173
  def setup_output_dir(dir, force)
    flag_file = output_flag_file dir

    last = {}

    if @options.dry_run then
      # do nothing
    elsif File.exist? dir then
      error "#{dir} exists and is not a directory" unless File.directory? dir

      begin
        open flag_file do |io|
          unless force then
            Time.parse io.gets

            io.each do |line|
              file, time = line.split "\t", 2
              time = Time.parse(time) rescue next
              last[file] = time
            end
          end
        end
      rescue SystemCallError, TypeError
        error Directory #{dir} already exists, but it looks like it isn't an RDoc directory.Because RDoc doesn't want to risk destroying any of your existing files,you'll need to specify a different output directory name (using the --op <dir>option)
      end unless @options.force_output
    else
      FileUtils.mkdir_p dir
      FileUtils.touch output_flag_file dir
    end

    last
  end