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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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fflush(3) Library Functions Manual fflush(3)
fflush - flush a stream
Standard C library (libc, -lc)
#include <stdio.h>
int fflush(FILE *_Nullable stream);
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).
Upon successful completion 0 is returned. Otherwise, EOF is
returned and 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 write(2).
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼─────────┤
│ fflush() │ Thread safety │ MT-Safe │
└─────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
C89, 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.
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).
fsync(2), sync(2), write(2), fclose(3), fileno(3), fopen(3),
fpurge(3), setbuf(3), unlocked_stdio(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-05-02 fflush(3)
Pages that refer to this page: fsync(2), fclose(3), fcloseall(3), fmemopen(3), fopen(3), fpurge(3), fseek(3), open_memstream(3), popen(3), setbuf(3), stdin(3), stdio(3), xdr(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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