code: func SystemdVersion(systemdBinaryPath string) (int, error) {
  	versionBytes, err := exec.Command(systemdBinaryPath, "--version").CombinedOutput()
  	if err != nil {
  		return -1, errwrap.Wrap(fmt.Errorf("unable to probe %s version", systemdBinaryPath), err)
  	}
  	versionStr := strings.SplitN(string(versionBytes), "\n", 2)[0]
  	var version int
  	n, err := fmt.Sscanf(versionStr, "systemd %d", &version)
  	if err != nil || n != 1 {
  		return -1, fmt.Errorf("cannot parse version: %q", versionStr)
  	}
  
  	return version, nil
  }
docs: // SystemdVersion parses and returns the version of a given systemd binary