Getting Services from the Service Container

You can access services from the service container by:

Injecting services to the command Class

Using the arguments section when registering your Command class at the file.

    class: Drupal\example\Command\DefaultCommand`
    arguments: ['@entity_type.manager']
      - { name: drupal.command }

Adding a new protected property.

   * The $entityTypeManager definition.
   * @var EntityTypeManager
  protected $entityTypeManager;

Passing the service using the __construct method.

   * Constructs a new DefaultCommand object.
  public function __construct(EntityTypeManager $entity_type_manager) {
    $this->entityTypeManager = $entity_type_manager;

Extending the ContainerAwareCommand base Class on your Command class.

By doing this you have access to the service container, in other words, you have access to any configured service using the provided get method.

protected function execute(InputInterface $input, OutputInterface $output)
    $uid = $input->getArgument('uid');
    $entityTypeManager = $this->get('entity_type.manager');;
    if ($entityTypeManager) {
        $user = $entityTypeManager->getStorage('user')->load($uid);