Custom Drupal bootstrap using file-API

Question

i am using a single php-file Drupal bootstrap to generate a standalone cronjob PHP file.

Here is my setup (the file resides in a subfolder, thats why i have to build up the base path like this)

/**
 * Drupal bootstrap
 */
$path = str_replace("sites/all/modules/custom/my_module/cron", 
"", DIRNAME(__FILE__));

define('DRUPAL_ROOT', $path);

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
//require_once DRUPAL_ROOT . '/includes/common.inc';
//require_once DRUPAL_ROOT . '/includes/module.inc';
//require_once DRUPAL_ROOT . '/includes/unicode.inc';
//require_once DRUPAL_ROOT . '/includes/file.inc';

drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

Whenever i am trying to use filebased functions like

$wrapper = file_stream_wrapper_get_instance_by_uri('public://mypath');
$wrapper->realpath();

or

drupal_realpath('public://mypath');

the result is always

bool FALSE

Do you know what i am missing here on my custom bootstrap that file operations do not work?

Thanks

Answer 1

In the meantime i found the solution.

All filepaths are handled relativley internally inside Drupal.

Whenever you are using some Drupal bootstrap inside a file that is not located at the ROOT-directory, make sure to use a:

chdir(DRUPAL_ROOT);

right before your function calls.