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
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
The open status of the stream is unaffected.
If the stream
argument is NULL, fflush
() flushes all
For a nonlocking counterpart, see unlocked_stdio
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
For an explanation of the terms used in this section, see attributes
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.
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