AIO_WRITE(2) BSD System Calls Manual AIO_WRITE(2)NAMEaio_write — asynchronous write to a file (REALTIME)
Standard C Library (libc, -lc)
aio_write(struct aiocb *aiocbp);
The aio_write() system call allows the calling process to write
aiocbp->aio_nbytes from the buffer pointed to by aiocbp->aio_buf to the
descriptor aiocbp->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 aiocbp->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 aiocbp->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 aiocbp->aio_reqprio.
The aiocbp 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 aiocbp->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 aiocbp and the
buffer that the aiocbp->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 aiocbp should be zeroed before the
aio_write() system call to avoid passing bogus context information to the
Modifications of the Asynchronous I/O Control Block structure or the buf‐
fer contents after the request has been enqueued, but before the request
has completed, are not allowed.
If the file offset in aiocbp->aio_offset is past the offset maximum for
aiocbp->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() system call will fail if:
[EAGAIN] Due to system resource limitations, the request was
[ENOSYS] The aio_write() system call is not supported.
The following conditions may be synchronously detected when the
aio_write() system call is made, or asynchronously, at any time there‐
after. If they are detected at call time, aio_write() returns -1 and
sets errno appropriately; otherwise the aio_return() system call 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] The aiocbp->aio_fildes argument is invalid, or is not
opened for writing.
[EINVAL] The offset aiocbp->aio_offset is not valid.
[EINVAL] The priority specified by aiocbp->aio_reqprio is not a
[EINVAL] The number of bytes specified by aiocbp->aio_nbytes is
[EINVAL] The constant in aiocbp->aio_sigevent.sigev_notify is
set to SIGEV_THREAD (SIGEV_THREAD is not supported).
If the request is successfully enqueued, but subsequently canceled or an
error occurs, the value returned by the aio_return() system call is per
the write(2) system call, and the value returned by the aio_error() sys‐
tem call is either one of the error returns from the write(2) system
call, or one of:
[EBADF] The aiocbp->aio_fildes argument is invalid for writ‐
[ECANCELED] The request was explicitly canceled via a call to
SEE ALSOaio_cancel(2), aio_error(2), aio_return(2), aio_suspend(2), aio(4)STANDARDS
The aio_write() system call is expected to conform to the IEEE Std 1003.1
The aio_write() system call first appeared in FreeBSD 3.0.
This manual page was written by Wes Peters ⟨email@example.com⟩.
Invalid information in aiocbp->_aiocb_private may confuse the kernel.
BSD September 18, 2008 BSD