StackFormation\Helper\Div::isProgramInstalled PHP Method

    public static function isProgramInstalled($program)
    {
        $out = null;
        $return = null;
        @exec('which ' . $program, $out, $return);
        return $return === 0;
    }

 /**
  * @param \StackFormation\Template[] $templates
  * @param string|null                $description
  * @param array                      $additionalData
  *
  * @return string
  * @throws \Exception
  */
 public function merge(array $templates, $description = null, array $additionalData = [])
 {
     if (count($templates) == 0) {
         throw new \InvalidArgumentException('No templates given');
     }
     $mergedTemplate = ['AWSTemplateFormatVersion' => '2010-09-09'];
     $mergeKeys = ['Parameters', 'Mappings', 'Conditions', 'Resources', 'Outputs', 'Metadata'];
     foreach ($templates as $template) {
         if (!$template instanceof \StackFormation\Template) {
             throw new \InvalidArgumentException('Expecting an array of \\StackFormation\\Template objects');
         }
         try {
             $array = $template->getDecodedJson();
             // Copy the current description into the final template
             if (!empty($array['Description'])) {
                 $mergedTemplate['Description'] = $array['Description'];
             }
             // Merge keys from current template with final template
             foreach ($mergeKeys as $mergeKey) {
                 if (isset($array[$mergeKey]) && is_array($array[$mergeKey])) {
                     foreach ($array[$mergeKey] as $key => $value) {
                         if (isset($mergedTemplate[$mergeKey][$key])) {
                             // it's ok if the parameter has the same name and type...
                             if ($mergeKey != 'Parameters' || $value['Type'] != $mergedTemplate[$mergeKey][$key]['Type']) {
                                 throw new \Exception("Duplicate key '{$key}' found in '{$mergeKey}'");
                             }
                         }
                         $mergedTemplate[$mergeKey][$key] = $value;
                     }
                 }
             }
         } catch (TemplateDecodeException $e) {
             if (Div::isProgramInstalled('jq')) {
                 $tmpfile = tempnam(sys_get_temp_dir(), 'json_validate_');
                 file_put_contents($tmpfile, $template->getProcessedTemplate());
                 passthru('jq . ' . $tmpfile);
                 unlink($tmpfile);
             }
             throw $e;
         }
     }
     // If a description override is specified use it
     if (!empty($description)) {
         $mergedTemplate['Description'] = trim($description);
     }
     if (empty($mergedTemplate['Description'])) {
         $mergedTemplate['Description'] = 'Merged Template';
     }
     $mergedTemplate = array_merge_recursive($mergedTemplate, $additionalData);
     $json = json_encode($mergedTemplate, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
     // Check for max template size
     if (strlen($json) > self::MAX_CF_TEMPLATE_SIZE) {
         $json = json_encode($mergedTemplate, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
         // Re-check for max template size
         if (strlen($json) > self::MAX_CF_TEMPLATE_SIZE) {
             throw new \Exception(sprintf('Template too big (%s bytes). Maximum template size is %s bytes.', strlen($json), self::MAX_CF_TEMPLATE_SIZE));
         }
     }
     return $json;
 }