NAME
fflush, fpurge
— flush a stream
SYNOPSIS
#include
<stdio.h>
int
fflush(FILE
*stream);
int
fpurge(FILE
*stream);
DESCRIPTION
The function
fflush()
forces a write of all buffered data for the given output or update
stream via the stream's underlying write function. If
stream is a stream opened for reading with
fdopen(3),
fopen(3), or
freopen(3) of a seekable file and it is not already at EOF then
fflush() sets the seek position of the file to the
file position of the stream and discards any text pushed back via
ungetc(3)
or ungetwc(3). The open status of the stream is unaffected.
If the stream argument is
NULL,
fflush()
flushes all
open output streams.
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)
or ungetwc(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] - stream 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).
SEE ALSO
STANDARDS
The fflush() function conforms to
IEEE Std 1003.1-2024 (“POSIX.1”).
HISTORY
A predecessor flush() first appeared in
Version 1 AT&T UNIX. The
fflush() function first appeared in
Version 4 AT&T UNIX. The
fpurge() function first appeared in
4.3BSD-Reno.