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+.\" Copyright (c) 1999 Softweyr LLC.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY Softweyr LLC AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL Softweyr LLC OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd June 2, 1999
+.Dt AIO_WRITE 2
+.Os
+.Sh NAME
+.Nm aio_write
+.Nd asynchronous write to a file (REALTIME)
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In aio.h
+.Ft int
+.Fn aio_write "struct aiocb *iocb"
+.Sh DESCRIPTION
+The
+.Fn aio_write
+system call allows the calling process to write
+.Fa iocb->aio_nbytes
+from the buffer pointed to by
+.Fa iocb->aio_buf
+to the descriptor
+.Fa 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.
+.Pp
+If
+.Dv O_APPEND
+is set for
+.Fa iocb->aio_fildes ,
+.Fn aio_write
+operations append to the file in the same order as the calls were
+made.
+If
+.Dv O_APPEND
+is not set for the file descriptor, the write operation will occur at
+the absolute position from the beginning of the file plus
+.Fa iocb->aio_offset .
+.Pp
+If
+.Dv _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
+.Fa iocb->aio_reqprio .
+.Pp
+The
+.Fa iocb
+pointer may be subsequently used as an argument to
+.Fn aio_return
+and
+.Fn aio_error
+in order to determine return or error status for the enqueued operation
+while it is in progress.
+.Pp
+If the request is successfully enqueued, the value of
+.Fa iocb->aio_offset
+can be modified during the request as context, so this value must not
+be referenced after the request is enqueued.
+.Sh RESTRICTIONS
+The Asynchronous I/O Control Block structure pointed to by
+.Fa iocb
+and the buffer that the
+.Fa 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.
+.Pp
+The asynchronous I/O control buffer
+.Fa iocb
+should be zeroed before the
+.Fn aio_write
+system call to avoid passing bogus context information to the kernel.
+.Pp
+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.
+.Pp
+If the file offset in
+.Fa iocb->aio_offset
+is past the offset maximum for
+.Fa iocb->aio_fildes ,
+no I/O will occur.
+.Sh RETURN VALUES
+.Rv -std aio_write
+.Sh ERRORS
+The
+.Fn aio_write
+system call will fail if:
+.Bl -tag -width Er
+.It Bq Er EAGAIN
+The request was not queued because of system resource limitations.
+.It Bq Er ENOSYS
+The
+.Fn aio_write
+system call is not supported.
+.El
+.Pp
+The following conditions may be synchronously detected when the
+.Fn aio_write
+system call is made, or asynchronously, at any time thereafter.
+If they
+are detected at call time,
+.Fn aio_write
+returns -1 and sets
+.Va errno
+appropriately; otherwise the
+.Fn aio_return
+system call must be called, and will return -1, and
+.Fn aio_error
+must be called to determine the actual value that would have been
+returned in
+.Va errno .
+.Pp
+.Bl -tag -width Er
+.It Bq Er EBADF
+The
+.Fa iocb->aio_fildes
+argument
+is invalid, or is not opened for writing.
+.It Bq Er EINVAL
+The offset
+.Fa iocb->aio_offset
+is not valid, the priority specified by
+.Fa iocb->aio_reqprio
+is not a valid priority, or the number of bytes specified by
+.Fa iocb->aio_nbytes
+is not valid.
+.El
+.Pp
+If the request is successfully enqueued, but subsequently canceled
+or an error occurs, the value returned by the
+.Fn aio_return
+system call is per the
+.Xr write 2
+system call, and the value returned by the
+.Fn aio_error
+system call is either one of the error returns from the
+.Xr write 2
+system call, or one of:
+.Bl -tag -width Er
+.It Bq Er EBADF
+The
+.Fa iocb->aio_fildes
+argument
+is invalid for writing.
+.It Bq Er ECANCELED
+The request was explicitly canceled via a call to
+.Fn aio_cancel .
+.It Bq Er EINVAL
+The offset
+.Fa iocb->aio_offset
+would be invalid.
+.El
+.Sh SEE ALSO
+.Xr aio_cancel 2 ,
+.Xr aio_error 2 ,
+.Xr aio_return 2 ,
+.Xr aio_suspend 2 ,
+.Xr aio_waitcomplete 2 ,
+.Xr siginfo 3 ,
+.Xr aio 4
+.Sh STANDARDS
+The
+.Fn aio_write
+system call
+is expected to conform to the
+.St -p1003.1
+standard.
+.Sh HISTORY
+The
+.Fn aio_write
+system call first appeared in
+.Fx 3.0 .
+.Sh AUTHORS
+This manual page was written by
+.An Wes Peters Aq wes@softweyr.com .
+.Sh BUGS
+Invalid information in
+.Fa iocb->_aiocb_private
+may confuse the kernel.