linux man page for fflush

FFLUSH(3)						     Linux Programmer's Manual							 FFLUSH(3)

NAME
       fflush - flush a stream

SYNOPSIS
       #include <stdio.h>

       int fflush(FILE *stream);

DESCRIPTION
       For output streams, fflush() forces a write of all user-space buffered data for the given output or update stream via the stream's underly-
       ing write function.  For input streams, fflush() discards any buffered data that has been fetched from the underlying  file,  but  has  not
       been by the application.  The open status of the stream is unaffected.

       If the stream argument is NULL, fflush() flushes all open output streams.

       For a nonlocking counterpart, see unlocked_stdio(3).

RETURN VALUE
       Upon successful completion 0 is returned.  Otherwise, EOF is returned and errno is set to indicate the error.

ERRORS
       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 write(2).

CONFORMING TO
       C89, C99, POSIX.1-2001, POSIX.1-2008.

       The standards do not specify the behavior for input streams.  Most other implementations behave the same as Linux.

NOTES
       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).

SEE ALSO
       fsync(2), sync(2), write(2), fclose(3), fopen(3), setbuf(3), unlocked_stdio(3)

COLOPHON
       This page is part of release 3.27 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
								    2009-09-06								 FFLUSH(3)