FFLUSH(3) Linux Programmers Manual FFLUSH(3)
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 streams underlying write
function. The open status of the stream is unaffected.
If the stream argument is NULL, fflush() flushes all open output
For a non-locking counterpart, see unlocked_stdio(3).
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, for example, with sync(2) or
fsync(2), sync(2), write(2), fclose(3), fopen(3), setbuf(3),
This page is part of release 3.05 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 1993-11-29 FFLUSH(3)