AIOWRITE(2)                BSD System Calls Manual               AIOWRITE(2)

NAME
     aiowrite -- asynchronous write to a file (REALTIME)

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     ##include <>

     int
     aiowrite(struct aiocb *iocb);

DESCRIPTION
     The aiowrite() system call allows the calling process to write
     iocb->aionbytes from the buffer pointed to by iocb->aiobuf to the
     descriptor iocb->aiofildes.  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 OAPEND is set for iocb->aiofildes, aiowrite() operations append to
     the file in the same order as the calls were made.  If OAPEND 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->aiooffset.

     If POSIXPRIORITIZEDIO 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->aioreqprio.

     The iocb pointer may be subsequently used as an argument to aioreturn()
     and aioerror() 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->aiooffset
     can be modified during the request as context, so this value must not be
     referenced after the request is enqueued.

RESTRICTIONS
     The Asynchronous I/O Control Block structure pointed to by iocb and the
     buffer that the iocb->aiobuf 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
     aiowrite() system call to avoid passing bogus context information to the
     kernel.

     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->aiooffset is past the offset maximum  for
     iocb->aiofildes, no I/O will occur.

RETURN VALUES
     The aiowrite() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERORS
     The aiowrite() system call will fail if:

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

     [ENOSYS]           The aiowrite() system call is not supported.

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

     [EBADF]            The iocb->aiofildes argument is invalid, or is not
                        opened for writing.

     [EINVAL]           The offset iocb->aiooffset is not valid, the priority
                        specified by iocb->aioreqprio is not a valid prior-
                        ity, or the number of bytes specified by
                        iocb->aionbytes is not valid.

     If the request is successfully enqueued, but subsequently canceled or an
     error occurs, the value returned by the aioreturn() system call is per
     the write(2) system call, and the value returned by the aioerror() sys-
     tem call is either one of the error returns from the write(2) system
     call, or one of:

     [EBADF]            The iocb->aiofildes argument is invalid for writing.

     [ECANCELED]        The request was explicitly canceled via a call to
                        aiocancel().

     [EINVAL]           The offset iocb->aiooffset would be invalid.

SEE ALSO
     aiocancel(2), aioerror(2), aioreturn(2), aiosuspend(2), aio(4)

STANDARDS
     The aiowrite() system call is expected to conform to the IE Std 1003.1
     (``POSIX.1'') standard.

HISTORY
     The aiowrite() system call first appeared in FreeBSD 3.0.

AUTHORS
     This manual page was written by Wes Peters .

BUGS
     Invalid information in iocb->aiocbprivate may confuse the kernel.

BSD                              June 2, 1999                              BSD