aio_read - asynchronous read
#include <aio.h>
int aio_read(struct aiocb *aiocbp);
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(3type) 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 to indicate the error. 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).
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)