The aio_read system call allows the calling process to read iocb->aio_nbytes from the descriptor iocb->aio_fildes beginning at the offset iocb->aio_offset into the buffer pointed to by iocb->aio_buf. The call returns immediately after the read request has been enqueued to the descriptor; the read may or may not have completed at the time the call returns.
If _POSIX_PRIORITIZED_IO is defined, and the descriptor supports it, then the enqueued operation is submitted at a priority equal to that of the calling process minus iocb->aio_reqprio.
The iocb->aio_lio_opcode argument is ignored by the aio_read system call.
The iocb pointer may be subsequently used as an argument to aio_return and aio_error in order to determine return or error status for the enqueued operation while it is in progress.
If the request could not be enqueued (generally due to invalid arguments), then the call returns without having enqueued the request.
If the request is successfully enqueued, the value of iocb->aio_offset can be modified during the request as context, so this value must not be referenced after the request is enqueued.
The Asynchronous I/O Control Block structure pointed to by iocb and the buffer that the iocb->aio_buf member of that structure references must remain valid until the operation has completed. For this reason, use of auto (stack) variables for these objects is discouraged.
The asynchronous I/O control buffer iocb should be zeroed before the aio_read call to avoid passing bogus context information to the kernel.
Modifications of the Asynchronous I/O Control Block structure or the buffer contents after the request has been enqueued, but before the request has completed, are not allowed.
If the file offset in iocb->aio_offset is past the offset maximum for iocb->aio_fildes, no I/O will occur.
.Rv -std aio_read
The aio_read system call will fail if: