public function cmdAddAlias()
    {
        $params = $this->getParam();

        if (count($params) != 3) {
            $this->errorAndExit($this->text('Invalid command'));
        }

        list($entity, $entity_id, $alias) = $params;

        if (empty($entity) || empty($entity_id) || empty($alias) || !is_numeric($entity_id)) {
            $this->errorAndExit($this->text('Invalid argument'));
        }

        if (!$this->alias->loadEntity($entity, $entity_id)) {
            $this->errorAndExit($this->text('Invalid argument'));
        }

        $result = $this->addAlias($entity, $entity_id, $alias);

        if (empty($result)) {
            $this->errorAndExit($this->text('Unexpected result'));
        }

        $this->line($result);
        $this->output();
    }