NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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

NAME         top

       fflush - flush a stream

SYNOPSIS         top

       #include <stdio.h>

       int fflush(FILE *stream);

DESCRIPTION         top

       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         top

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

ERRORS         top

       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         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌──────────┬───────────────┬─────────┐
       │Interface Attribute     Value   │
       ├──────────┼───────────────┼─────────┤
       │fflush()  │ Thread safety │ MT-Safe │
       └──────────┴───────────────┴─────────┘

CONFORMING TO         top

       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         top

       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         top

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

COLOPHON         top

       This page is part of release 4.02 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
       http://www.kernel.org/doc/man-pages/.

GNU                              2015-03-02                        FFLUSH(3)