:
: 3개의 차이점을 알고 싶습니다.
:
: .bash_profile을 편집하고 . .bash_profile을 하라고
:
: 하는데 왜 해야하는지요?
:
: /etc/profile을 편집하고 source /etc/profile을 하라고 하는데
:
: 왜 해야하는지요?
:
: 그리고 어떤 file을 편집하고 sync를 하라고 하는데 왜 인지요?
:
: 이 3개의 차이점을 가르쳐 주세요?ㅑ
 
answer: 'sync' writes any data brffered in memory out to disk.
        This can include (but is not limited to) modified superblocks,
         modified inodes, and delayed reads and writes. The must be
         implemented by the kerner;
         The 'sync' program does nothing but exercise the 'syne' system call.
          The kernel keeps date in memory to avoid doing (relatively slow)
         disk reads and writes. This improves performance, but if the computer
         crashes, doata may be lost or the filesystem corrupted as a result.
         'sync' ensures everything in memory is written to disk.
        'source'