Piwik\Filechecks::getUserAndGroup PHP Method

    public static function getUserAndGroup()
    {
        $user = self::getUser();
        if (!function_exists('shell_exec')) {
            return $user . ':' . $user;
        }
        $group = trim(shell_exec('groups ' . $user . ' | cut -f3 -d" "'));
        if (empty($group)) {
            $group = 'www-data';
        }
        return $user . ':' . $group;
    }

 public function execute()
 {
     $label = $this->translator->translate('CustomPiwikJs_DiagnosticPiwikJsWritable');
     $file = new File(PIWIK_DOCUMENT_ROOT . '/piwik.js');
     if ($file->hasWriteAccess()) {
         return array(DiagnosticResult::singleResult($label, DiagnosticResult::STATUS_OK, ''));
     }
     $comment = $this->translator->translate('CustomPiwikJs_DiagnosticPiwikJsNotWritable');
     if (!SettingsServer::isWindows()) {
         $realpath = Filesystem::realpath(PIWIK_INCLUDE_PATH . '/piwik.js');
         $command = "<br/><code> chmod +w {$realpath}<br/> chown " . Filechecks::getUserAndGroup() . " " . $realpath . "</code><br />";
         $comment .= $this->translator->translate('CustomPiwikJs_DiagnosticPiwikJsMakeWritable', $command);
     }
     return array(DiagnosticResult::singleResult($label, DiagnosticResult::STATUS_WARNING, $comment));
 }