nextcloud/apps/contacts/temporaryupdate.php

<?php
/**
 * ownCloud - Addressbook
 *
 * @author Jakob Sack
 * @copyright 2011 Jakob Sack mail@jakobsack.de
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
// Init owncloud
require_once('../../lib/base.php');
$connector = new OC_Connector_Sabre_Principal;
$users = OC_User::getUsers();

foreach($users as $user){
	$foo = $connector->getPrincipalByPath('principals/'.$user);
	if(!isset($foo)){
		OC_Connector_Sabre_Principal::addPrincipal(array('uid'=>$user));
	}
}
echo "done";