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 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 4.15 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/.

GNU                                                                 2017-09-15                                                           FFLUSH(3)