def cmd_cwd(param)
      send_unauthorised and return unless logged_in?
      path = build_path(param)

      @driver.change_dir(path) do |result|
        if result
          @name_prefix = path
          send_response "250 Directory changed to #{path}"
        else
          send_permission_denied
        end
      end
    end
def cmd_cwd(param)
      send_unauthorised and return unless logged_in?
      path = build_path(param)

      @driver.change_dir(path) do |result|
        if result
          @name_prefix = path
          send_response "250 Directory changed to #{path}"
        else
          send_permission_denied
        end
      end
    end
change directory