def attach(shmaddr = nil, flags = 0)
      shmaddr = shmat(@shmid, shmaddr, flags)
      check_result(shmaddr)
      shmaddr
    end
def attach(shmaddr = nil, flags = 0)
      shmaddr = shmat(@shmid, shmaddr, flags)
      check_result(shmaddr)
      shmaddr
    end
Attach to a shared memory address object and return it.
 See shmat(2). If +shmaddr+ is nil, the shared memory is attached
 at the first available address as selected by the system. See
 shmat(2).