FFLUSH(3) - man page online | library functions

Flush a stream.

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 underlying write function. For input streams associated with seekable files (e.g., disk files, but not pipes or ter‐ minals), 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), fopen(3), setbuf(3), unlocked_stdio(3)
COLOPHON This page is part of release 4.04 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
GNU 2015-03-02 FFLUSH(3)
This manual Reference Other manuals
fflush(3) referred by explain(1) | explain(3) | explain_fclose(3) | explain_fclose_or_die(3) | explain_fflush(3) | explain_fflush_or_die(3) | fclose(3) | fcloseall(3) | fgetln(3) | fmemopen(3) | fopen(3) | fpurge(3) | fseek(3) | log(3pub) | mongoc_stream_flush(3) | popen(3) | setbuf(3) | stdin(3) | stdio(3) | xdr(3)
refer to attributes(7) | fclose(3) | fopen(3) | fsync(2) | setbuf(3) | sync(2) | unlocked_stdio(3) | write(2)