Manpage of FFLUSH
FFLUSHSection: Linux Programmer's Manual (3)
NAMEfflush - flush a stream
DESCRIPTIONFor output streams, fflush() forces a write of all user-space buffered data for the given output or update streamvia the stream's underlying write function.
For input streams associated with seekable files (e.g., disk files, but not pipes or terminals), fflush() discards any buffered data that has been fetched from the underlying file, but has not been consumed by the application.
The open status of the stream is unaffected.
If the streamargument is NULL, fflush() flushes allopen output streams.
For a nonlocking counterpart, see unlocked_stdio(3).
RETURN VALUEUpon successful completion 0 is returned. Otherwise, EOFis returned and errnois set to indicate the error.
- streamis not an open stream, or is not open for writing.
The function fflush() may also fail and set errnofor any of the errors specified for write(2).
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
CONFORMING TOC89, C99, POSIX.1-2001, POSIX.1-2008.
NOTESNote that fflush() flushes only the user-space buffers provided by the C library. To ensure that the data is physically stored on disk the kernel buffers must be flushed too, for example, with sync(2) or fsync(2).
SEE ALSOfsync(2), sync(2), write(2), fclose(3), fopen(3), setbuf(3), unlocked_stdio(3)
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Time: 22:27:53 GMT, June 20, 2016