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AIO_READ(3) Linux Programmer's Manual AIO_READ(3)
aio_read - asynchronous read
#include <aio.h>
int aio_read(struct aiocb *aiocbp);
Link with -lrt.
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.
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).
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.
The aio_read() function is available since glibc 2.1.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├───────────┼───────────────┼─────────┤
│aio_read() │ Thread safety │ MT-Safe │
└───────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008.
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.
See aio(7).
aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3),
aio_suspend(3), aio_write(3), lio_listio(3), aio(7)
This page is part of release 4.12 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/.
2016-03-15 AIO_READ(3)
Pages that refer to this page: clone(2), execve(2), fork(2), aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3), aio_suspend(3), aio_write(3), lio_listio(3), aio(7), sigevent(7)