20120607

http://www.cnblogs.com/codingmonkey/articles/2431078.html

Linux中link，unlink，close，fclose详解
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Flushing output on a buffered stream means transmitting all accumulated characters to the file. There are many circumstances when buffered output on a stream is flushed automatically:

    When you try to do output and the output buffer is full.
    When the stream is closed. See Closing Streams.
    When the program terminates by calling exit. See Normal Termination.
    When a newline is written, if the stream is line buffered.
    Whenever an input operation on any stream actually reads data from its file.

http://www.gnu.org/software/libc/manual/html_node/Flushing-Buffers.html