Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
AIO_WRITE(2)		  FreeBSD System Calls Manual		  AIO_WRITE(2)

     aio_write -- asynchronous write to	a file (REALTIME)

     Standard C	Library	(libc, -lc)

     #include <aio.h>

     aio_write(struct aiocb *iocb);

     The aio_write() function allows the calling process to write
     iocb-_aio_nbytes from the buffer pointed to by iocb-_aio_buf to the
     descriptor	iocb-_aio_fildes.  The call returns immediately	after the
     write request has been enqueued to	the descriptor;	the write may or may
     not have completed	at the time the	call returns.  If the request could
     not be enqueued, generally	due to invalid arguments, the call returns
     without having enqueued the request.

     If	O_APPEND is set	for iocb-_aio_fildes, aio_write() operations append to
     the file in the same order	as the calls were made.	 If O_APPEND is	not
     set for the file descriptor, the write operation will occur at the	abso-
     lute position from	the beginning of the file plus iocb-_aio_offset.

     If	_POSIX_PRIORITIZED_IO is defined, and the descriptor supports it, then
     the enqueued operation is submitted at a priority equal to	that of	the
     calling process minus iocb-_aio_reqprio.

     The iocb pointer may be subsequently used as an argument to aio_return()
     and aio_error() in	order to determine return or error status for the
     enqueued operation	while it is in progress.

     If	the request is successfully enqueued, the value	of iocb-_aio_offset
     can be modified during the	request	as context, so this value must not be
     referenced	after the request is enqueued.

     The Asynchronous I/O Control Block	structure pointed to by	iocb and the
     buffer that the iocb-_aio_buf member of that structure references must
     remain valid until	the operation has completed.  For this reason, use of
     auto (stack) variables for	these objects is discouraged.

     The asynchronous I/O control buffer iocb should be	zeroed before the
     aio_write() call to avoid passing bogus context information to the	ker-

     Modifications of the Asynchronous I/O Control Block structure or the
     buffer contents after the request has been	enqueued, but before the
     request has completed, are	not allowed.

     If	the file offset	in iocb-_aio_offset is past the	offset maximum	for
     iocb-_aio_fildes, no I/O will occur.

     The aio_write() function returns the value	0 if successful; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the

     The aio_write() function will fail	if:

     [EAGAIN]		The request was	not queued because of system resource

     [ENOSYS]		The aio_write()	call is	not supported.

     The following conditions may be synchronously detected when the
     aio_write() call is made, or asynchronously, at any time thereafter.  If
     they are detected at call time, aio_write() returns -1 and	sets errno
     appropriately; otherwise the aio_return() function	must be	called,	and
     will return -1, and aio_error() must be called to determine the actual
     value that	would have been	returned in errno.

     [EBADF]		iocb-_aio_fildes is invalid, or	is not opened for

     [EINVAL]		The offset iocb-_aio_offset is not valid, the priority
			specified by iocb-_aio_reqprio is not a	valid prior-
			ity, or	the number of bytes specified by
			iocb-_aio_nbytes is not	valid.

     If	the request is successfully enqueued, but subsequently canceled	or an
     error occurs, the value returned by the aio_return() function is per the
     write(2) call, and	the value returned by the aio_error() function is
     either one	of the error returns from the write(2) call, or	one of:

     [EBADF]		iocb-_aio_fildes is invalid for	writing.

     [ECANCELED]	The request was	explicitly canceled via	a call to

     [EINVAL]		The offset iocb-_aio_offset would be invalid.

     aio_write() is expected to	conform	to the IEEE Std	1003.2 (``POSIX.2'')

     The aio_write Function first appeared in FreeBSD 3.0.

     This manual page was written by Wes Peters	<>.

     Asynchronous I/O operations cannot	be canceled in this implementation.
     Invalid information in iocb-__aiocb_private may confuse the kernel.

FreeBSD	4.7			 June 2, 1999			   FreeBSD 4.7


Want to link to this manual page? Use this URL:

home | help