--- shutdown([how])
    åȤΰʹߤ³λޤhow0Ǥ
    ʹߤμ1Ǥϡʹߤݤޤ
    how2λˤϡʹߤȤ˵ݤ
    ޤhowά2ꤷȤˤʤޤ
    shutdown(2)򻲾ȡ

