8.2.x system.module system_cron()
8.0.x system.module system_cron()
8.1.x system.module system_cron()
6.x system.module system_cron()
7.x system.module system_cron()

Implements hook_cron().

Remove older rows from flood and batch table. Remove old temporary files.


modules/system/system.module, line 3044
Configuration system that lets administrators modify the workings of the site.


function system_cron() {
  // Cleanup the flood.
    ->condition('expiration', REQUEST_TIME, '<')

  // Remove temporary files that are older than DRUPAL_MAXIMUM_TEMP_FILE_AGE.
  // Use separate placeholders for the status to avoid a bug in some versions
  // of PHP. See http://drupal.org/node/352956.
  $result = db_query('SELECT fid FROM {file_managed} WHERE status <> :permanent AND timestamp < :timestamp', array(
    ':permanent' => FILE_STATUS_PERMANENT,
  foreach ($result as $row) {
    if ($file = file_load($row->fid)) {
      $references = file_usage_list($file);
      if (empty($references)) {
        if (!file_delete($file)) {
          watchdog('file system', 'Could not delete temporary file "%path" during garbage collection', array('%path' => $file->uri), WATCHDOG_ERROR);
      else {
        watchdog('file system', 'Did not delete temporary file "%path" during garbage collection, because it is in use by the following modules: %modules.', array('%path' => $file->uri, '%modules' => implode(', ', array_keys($references))), WATCHDOG_INFO);

  // Delete expired cache entries.
  // Avoid invoking hook_flush_cashes() on every cron run because some modules
  // use this hook to perform expensive rebuilding operations (which are only
  // designed to happen on full cache clears), rather than just returning a
  // list of cache tables to be cleared.
  $cache_object = cache_get('system_cache_tables');
  if (empty($cache_object)) {
    $core = array('cache', 'cache_path', 'cache_filter', 'cache_page', 'cache_form', 'cache_menu');
    $cache_tables = array_merge(module_invoke_all('flush_caches'), $core);
    cache_set('system_cache_tables', $cache_tables);
  else {
    $cache_tables = $cache_object->data;
  foreach ($cache_tables as $table) {
    cache_clear_all(NULL, $table);

  // Cleanup the batch table and the queue for failed batches.
    ->condition('timestamp', REQUEST_TIME - 864000, '<')
    ->condition('created', REQUEST_TIME - 864000, '<')
    ->condition('name', 'drupal_batch:%', 'LIKE')

  // Reset expired items in the default queue implementation table. If that's
  // not used, this will simply be a no-op.
      'expire' => 0,
    ->condition('expire', 0, '<>')
    ->condition('expire', REQUEST_TIME, '<')