NAME
fflush,
fflush_unlocked, fpurge
— flush a stream
LIBRARY
library “libc”
SYNOPSIS
#include
<stdio.h>
int
fflush(FILE
*stream);
int
fflush_unlocked(FILE
*stream);
int
fpurge(FILE
*stream);
DESCRIPTION
The functionfflush()
forces a write of all buffered data for the given output or update
stream via the stream's underlying write function. The
open status of the stream is unaffected.
If the stream argument is
NULL,
fflush()
flushes all
open output streams.
The
fflush_unlocked()
function is equivalent to fflush(), except that the
caller is responsible for locking the stream with
flockfile(3) before calling it. This function may be used to
avoid the overhead of locking the stream and to prevent races when multiple
threads are operating on the same stream.
The function
fpurge()
erases any input or output buffered in the given
stream. For output streams this discards any unwritten
output. For input streams this discards any input read from the underlying
object but not yet obtained via
getc(3); this includes any text pushed back via
ungetc(3).
RETURN VALUES
Upon successful completion 0 is returned. Otherwise,
EOF is returned and the global variable
errno is set to indicate the error.
ERRORS
- [
EBADF] - The stream argument is not an open stream.
The function fflush() may also fail and
set errno for any of the errors specified for the
routine write(2), except that in case of stream
being a read-only descriptor, fflush() returns
0.
SEE ALSO
STANDARDS
The fflush() function conforms to
ISO/IEC 9899:1990
(“ISO C90”).
HISTORY
The fflush() function first appeared in
Version 4 AT&T UNIX. The
fpurge() function first appeared in
4.4BSD.