fflush - flush a stream
int fflush(FILE *stream);
The function fflush forces a write of all user-space buffered data for
the given output or update stream via the stream's underlying write
function. The open status of the stream is unaffected.
If the stream argument is NULL, fflush flushes all open output streams.
Upon successful completion 0 is returned. Otherwise, EOF is returned
and the global variable errno is set to indicate the error.
EBADF Stream is not an open stream, or is not open for writing.
The function fflush may also fail and set errno for any of the errors
specified for the routine write(2).
Note that fflush() only flushes 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, e.g. with sync(2) or fsync(2).
The fflush function conforms to ANSI X3.159-1989 (``ANSI C'').
write(2), fclose(3), fopen(3), fsync(2), sync(2), write(2), setbuf(3)
BSD MANPAGE 1993-11-29 FFLUSH(3)
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