193 lines
5.4 KiB
Groff
193 lines
5.4 KiB
Groff
.\" 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
|
|
function 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
|
|
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
|
|
function 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
|
|
call is not supported.
|
|
.El
|
|
.Pp
|
|
The following conditions may be synchronously detected when the
|
|
.Fn aio_write
|
|
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
|
|
function 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
|
|
.Fa iocb->aio_fildes
|
|
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
|
|
function is per the
|
|
.Xr write 2
|
|
call, and the value returned by the
|
|
.Fn aio_error
|
|
function is either one of the error returns from the
|
|
.Xr write 2
|
|
call, or one of:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
.Fa iocb->aio_fildes
|
|
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 STANDARDS
|
|
.Fn aio_write
|
|
is expected to conform to the
|
|
.St -p1003.2
|
|
standard.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
Function 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.
|