checking for sudo access (from bundler gem)

gistfile1.rb

    def requires_sudo?
      return @requires_sudo if @checked_for_sudo

      path = bundle_path
      path = path.parent until path.exist?
      sudo_present = !(`which sudo` rescue '').empty?

      @checked_for_sudo = true
      @requires_sudo = settings.allow_sudo? && !File.writable?(path) && sudo_present
    end

    def mkdir_p(path)
      if requires_sudo?
        sudo "mkdir -p '#{path}'" unless File.exist?(path)
      else
        FileUtils.mkdir_p(path)
      end
    end

    def sudo(str)
      `sudo -p 'Enter your password to install the bundled RubyGems to your system: ' #{str}`
    end