fflush - flush a stream
int fflush(FILE *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, 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
For a nonlocking counterpart, see unlocked_stdio(3)
Upon successful completion 0 is returned. Otherwise, EOF
is returned and
is set to indicate the error.
- 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)
Multithreading (see pthreads(7))¶
() function is thread-safe.
C89, C99, POSIX.1-2001, POSIX.1-2008.
The standards do not specify the behavior for input streams. Most other
implementations behave the same as Linux.
Note that fflush
() only flushes 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)
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