/**
  * {@inheritdoc}
  */
 protected function canBeUsed()
 {
     return in_array($this->shell->getType(), array(Shell::TYPE_BSD, Shell::TYPE_DARWIN)) && parent::canBeUsed();
 }
 /**
  * {@inheritdoc}
  */
 protected function canBeUsed()
 {
     return $this->shell->getType() === Shell::TYPE_UNIX && parent::canBeUsed();
 }