private function execCommand(array $command): array
  {
    $this->logVerbose('Execute: %s', implode(' ', $command));
    list($output, $ret) = ProgramExecution::exec1($command, null);
    if ($ret!=0)
    {
      foreach ($output as $line)
      {
        $this->logInfo($line);
      }
      $this->logError("Error executing '%s'.", implode(' ', $command));
    }
    else
    {
      foreach ($output as $line)
      {
        $this->logVerbose($line);
      }
    }

    return $output;
  }