code: func SetsysForUid(id int, key, value string) error {
  	if !_IS_ROOT {
  		return ErrNoRoot
  	}
  
  	_settings, err := getSettingsForUid(id)
  	if err != nil {
  		return err
  	}
  	return _Set(_settings.global, key, value)
  }
docs: // SetsysForUid sets the value of the environment variable named by the key that
  // affects the system as a whole. You must be Root.
  // It returns an error, if any.