--- fsync       ruby 1.7 feature

    񤭹Ѥ IO Фơƥॳfsync(2) [manual page] 
    ¹ԤޤflushԤä(OS٥)ޤǥ
    񤭹ޤƤʤˤǡǥ˽񤭽Фޤ

     0 ֤ޤԤ㳰 Errno::EXXX ȯ
    ޤself 񤭹ѤǤʤ㳰 IOError ȯ
    ޤ

