AIO_READ
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME
aio_read - asynchronous read
SYNOPSIS
#include <aio.h>
int aio_read(struct aiocb *aiocbp);
Link with -lrt.
DESCRIPTION
The
aio_read()
function queues the I/O request described by the buffer pointed to by
aiocbp.
This function is the asynchronous analog of
read(2).
The arguments of the call
read(fd, buf, count)
correspond (in order) to the fields
aio_fildes,
aio_buf,
and
aio_nbytes
of the structure pointed to by
aiocbp.
(See
aio(7)
for a description of the
aiocb
structure.)
The data is read starting at the absolute position
aiocbp->aio_offset,
regardless of the file offset.
After the call,
the value of the file offset is unspecified.
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
aio_error(3).
The return status of a completed I/O operation can be obtained by
aio_return(3).
Asynchronous notification of I/O completion can be obtained by setting
aiocbp->aio_sigevent
appropriately; see
sigevent(7)
for details.
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
aiocbp->aio_reqprio.
The field
aiocbp->aio_lio_opcode
is ignored.
No data is read from a regular file beyond its maximum offset.
RETURN VALUE
On success, 0 is returned.
On error, the request is not enqueued, -1
is returned, and
errno
is set appropriately.
If an error is detected only later, it will
be reported via
aio_return(3)
(returns status -1) and
aio_error(3)
(error status---whatever one would have gotten in
errno,
such as
EBADF).
ERRORS
- EAGAIN
-
Out of resources.
- EBADF
-
aio_fildes
is not a valid file descriptor open for reading.
- EINVAL
-
One or more of
aio_offset,
aio_reqprio,
or
aio_nbytes
are invalid.
- ENOSYS
-
aio_read()
is not implemented.
- 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.
VERSIONS
The
aio_read()
function is available since glibc 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
aio_read()
| Thread safety | MT-Safe
|
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
It is a good idea to zero out the control block before use.
The control block must not be changed while the read operation
is in progress.
The buffer area being read into
must not be accessed during the operation or undefined results may occur.
The memory areas involved must remain valid.
Simultaneous I/O operations specifying the same
aiocb
structure produce undefined results.
EXAMPLE
See
aio(7).
SEE ALSO
aio_cancel(3),
aio_error(3),
aio_fsync(3),
aio_return(3),
aio_suspend(3),
aio_write(3),
lio_listio(3),
aio(7)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- EXAMPLE
-
- SEE ALSO
-
- COLOPHON
-
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