FFLUSH
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Page Index
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 underlying write function.
For input streams associated with seekable files
(e.g., disk files, but not pipes or terminals),
fflush()
discards any buffered data that has been fetched from the underlying file,
but has not been consumed 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).
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
fflush()
| Thread safety | MT-Safe
|
CONFORMING TO
C89, C99, POSIX.1-2001, POSIX.1-2008.
POSIX.1-2001 did not specify the behavior for flushing of input streams,
but the behavior is specified in POSIX.1-2008.
NOTES
Note that
fflush()
flushes only 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),
fileno(3),
fopen(3),
setbuf(3),
unlocked_stdio(3)
COLOPHON
This page is part of release 5.10 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.