FFLUSH(3)

NAME
fflush - flush a stream

SYNOPSIS
#include <stdio.h>

int fflush(FILE *stream);

DESCRIPTION
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.

For a non-locking counterpart, see unlocked_stdio(3).

RETURN VALUE
Upon successful completion 0 is returned. Otherwise, EOF is returned and the global variable 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 the routine write(2).

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, e.g. with sync(2) or fsync(2).

CONFORMING TO
C89, C99.

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