--- sid_available?

    ¸ ID ̵ͭ

    ¸桼 ID ĴĶɤ򿿵֤ͤ
    ¸桼 ID Ĥʤ true ֤
    ¸桼 ID ̵ͭΤȽǤʤĶǤϡ
    ͤϿͤǤ (βǽ⤢) Ȥդɬס
    ߤϡξΤ줫­
    ¸桼 ID ĤΤȽꤹ롥
     setresuid 
     seteuid 
     _POSIX_SAVED_IDS ȤƤ

