def chown(user_and_group)
      return unless user_and_group
      user, group = user_and_group.split(':').map {|s| s == '' ? nil : s}
      FileUtils.chown user, group, selected_items.map(&:path)
      ls
    end
def chown(user_and_group)
      return unless user_and_group
      user, group = user_and_group.split(':').map {|s| s == '' ? nil : s}
      FileUtils.chown user, group, selected_items.map(&:path)
      ls
    end
Change the file owner of the selected files and directories.

 ==== Parameters
 * +user_and_group+ - user name and group name separated by : (e.g. alice, nobody:nobody, :admin)