The aio_return system call returns the final status of the asynchronous I/O request associated with the structure pointed to by iocb.
The aio_return system call should only be called once, to obtain the final status of an asynchronous I/O operation once aio_error(2) returns something other than EINPROGRESS.
If the asynchronous I/O request has completed, the status is returned as described in read(2), write(2), or fsync(2). On failure, aio_return returns -1 and sets errno to indicate the error condition.
The aio_return system call will fail if: