code: func (t *tcShaper) interfaceExists() (bool, string, error) {
  	data, err := t.e.Command("tc", "qdisc", "show", "dev", t.iface).CombinedOutput()
  	if err != nil {
  		return false, "", err
  	}
  	value := strings.TrimSpace(string(data))
  	if len(value) == 0 {
  		return false, "", nil
  	}
  	return true, value, nil
  }
docs: // tests to see if an interface exists, if it does, return true and the status line for the interface
  // returns false, "", <err> if an error occurs.