if c.Process != nil {
		return errors.New("exec: already started")
	}

	started := false
	defer func() {
		closeDescriptors(c.childIOFiles)
		c.childIOFiles = nil

		if !started {
			closeDescriptors(c.parentIOPipes)
			c.parentIOPipes = nil
		}
	}()

	if c.Path == "" && c.Err == nil && c.lookPathErr == nil {
		c.Err = errors.New("exec: no command")
	}