---

Manual Reference Pages  - FFLUSH (3)

---

fflush - flush a stream

CONTENTS

Synopsis
Description
Errors
Notes

#include <stdio.h>

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.

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

The function fflush() conforms to ANSI X3.159-1989 (‘‘ANSI C’’).

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

Jump to page    or go to Top of page |  Section 3 |  Main Index.