Method err

include/process/subprocess.hpp:263–266

* @return File descriptor representing the parent side (i.e., write * side) of this subprocess' stderr pipe or None if no pipe was * requested. */

   *     requested.
   */
  Option<int_fd> err() const
  {
    return data->err;
  }

  /**
   * Exit status of this subprocess captured as a Future (completed