aio_read - asynchronous read
int aio_read(struct aiocb
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
read(fd, buf, count)
correspond (in order) to the fields
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 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_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
errno, such as EBADF).
Out of resources.
aio_fildes is not a valid file descriptor open for
One or more of
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 this file.
For an explanation of the terms used in this section, see attributes(7).
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
structure produce undefined results.
aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3), aio_suspend(3), aio_write(3), lio_listio(3), aio(7)
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