mirror of https://github.com/mkerrisk/man-pages
114 lines
3.4 KiB
Groff
114 lines
3.4 KiB
Groff
.\" Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl)
|
|
.\"
|
|
.\" This is free documentation; you can redistribute it and/or
|
|
.\" modify it under the terms of the GNU General Public License as
|
|
.\" published by the Free Software Foundation; either version 2 of
|
|
.\" the License, or (at your option) any later version.
|
|
.\"
|
|
.\" The GNU General Public License's references to "object code"
|
|
.\" and "executables" are to be interpreted as the output of any
|
|
.\" document formatting or typesetting system, including
|
|
.\" intermediate and printed output.
|
|
.\"
|
|
.\" This manual is distributed in the hope that it will be useful,
|
|
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
.\" GNU General Public License for more details.
|
|
.\"
|
|
.\" You should have received a copy of the GNU General Public
|
|
.\" License along with this manual; if not, write to the Free
|
|
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
|
|
.\" USA.
|
|
.\"
|
|
.TH AIO_READ 3 2003-11-14 "" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
aio_read \- asynchronous read
|
|
.SH SYNOPSIS
|
|
.sp
|
|
.B "#include <aio.h>"
|
|
.sp
|
|
.BI "int aio_read(struct aiocb *" aiocbp );
|
|
.SH DESCRIPTION
|
|
The
|
|
.BR aio_read ()
|
|
function requests an asynchronous "n = read(fd, buf, count)"
|
|
with fd, buf, count given by
|
|
.IR aiocbp->aio_fildes ,
|
|
.IR aiocbp->aio_buf ,
|
|
.IR aiocbp->aio_nbytes ,
|
|
respectively. The return status n can be retrieved upon completion using
|
|
.BR aio_return (3).
|
|
.LP
|
|
The data is read starting at the absolute file offset
|
|
.IR aiocbp->aio_offset ,
|
|
regardless of the current file position. After this request,
|
|
the value of the current file position is unspecified.
|
|
.LP
|
|
The "asynchronous" means that this call returns as soon as the
|
|
request has been enqueued; the read may or may not have completed
|
|
when the call returns. One tests for completion using
|
|
.BR aio_error (3).
|
|
.LP
|
|
If _POSIX_PRIORITIZED_IO is defined, and this file supports it,
|
|
then the asynchronous operation is submitted at a priority equal
|
|
to that of the calling process minus
|
|
.IR aiocbp->aio_reqprio .
|
|
.LP
|
|
The field
|
|
.I aiocbp->aio_lio_opcode
|
|
is ignored.
|
|
.LP
|
|
No data is read from a regular file beyond its maximum offset.
|
|
.SH "RETURN VALUE"
|
|
On success, 0 is returned. On error the request is not enqueued, \-1
|
|
is returned, and
|
|
.I errno
|
|
is set appropriately. If an error is first detected later, it will
|
|
be reported via
|
|
.BR aio_return (3)
|
|
(returns status \-1) and
|
|
.BR aio_error (3)
|
|
(error status whatever one would have gotten in
|
|
.IR errno ,
|
|
such as EBADF).
|
|
.SH ERRORS
|
|
.TP
|
|
.B EAGAIN
|
|
Out of resources.
|
|
.TP
|
|
.B EBADF
|
|
.I aio_fildes
|
|
is not a valid file descriptor open for reading.
|
|
.TP
|
|
.B EINVAL
|
|
One or more of
|
|
.IR aio_offset ,
|
|
.IR aio_reqprio ,
|
|
.IR aio_nbytes
|
|
are invalid.
|
|
.TP
|
|
.B ENOSYS
|
|
This function is not supported.
|
|
.TP
|
|
.B EOVERFLOW
|
|
The file is a regular file, we start reading before end-of-file
|
|
and want at least one byte, but the starting position is past
|
|
the maximum offset for this file.
|
|
.SH NOTES
|
|
It is a good idea to zero out the control block before use.
|
|
This control block must not be changed while the read operation
|
|
is in progress.
|
|
The buffer area being read into
|
|
.\" or the control block of the operation
|
|
must not be accessed during the operation or undefined results may
|
|
occur. The memory areas involved must remain valid.
|
|
.SH "CONFORMING TO"
|
|
POSIX.1-2001
|
|
.SH "SEE ALSO"
|
|
.BR aio_cancel (3),
|
|
.BR aio_error (3),
|
|
.BR aio_fsync (3),
|
|
.BR aio_return (3),
|
|
.BR aio_suspend (3),
|
|
.BR aio_write (3)
|