− asynchronous read
aio_read(struct aiocb *aiocbp);
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
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
The data is
read starting at the absolute file offset
aiocbp−>aio_offset, regardless of the
current file offset. After the call, the value of the
current file offset is unspecified.
"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.
_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_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).
Out of resources.
aio_fildes is not a valid file descriptor open
One or more of aio_offset, aio_reqprio, or
aio_nbytes are invalid.
aio_read() is not implemented.
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
aio_read() function is available since glibc 2.1.
explanation of the terms used in this section, see
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.
I/O operations specifying the same aiocb structure
produce undefined results.
aio_write(3), lio_listio(3), aio(7)
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