Drush and database credentials from external sources

Question

For some specific automation reasons, I use the following snippet in settings.php rather than defining db credentials directly in it.

$databases = array(
  'default' => array(
    'default' => array(
      'database' => $_SERVER['DB_NAME'],
      'username' => ini_get('mysql.default_user'),
      'password' => ini_get('mysql.default_password'),
      'host' => 'localhost',
      'port' => '',
      'driver' => 'mysql',
      'prefix' => '',
    ),
  ),
);

And when I try to use drush, it won't pick up database credentials. How can I give the right database credentials to Drush? Can I define something in drushrc files per project?

The following is what I get from drush status.

Drupal version : 7.22
Site URI : http://default
Database driver : mysql
Database hostname : localhost
Database username :
Database name:
Default theme : garland
Administration theme : garland
PHP configuration : /etc/php5/cli/php.ini
Drush version : 5.4
Drush configuration :
Drupal root : /home/oep/www/dev/docroot Site path : sites/default
File directory path : sites/default/files

Answer 1

As you can see, drush is run from command line interface, so it uses cli/php.ini and not regular one. If you feel like keeping password and username in ini file, you need to make sure there are synchronized between WWW and CLI php.ini files.