aio_return - get return status of asynchronous I/O operation
ssize_t aio_return(struct aiocb *aiocbp);
The aio_return() function returns the final return status for the asynchronous I/O request with control block pointed to by aiocbp.
This function should be called only once for any given request, after aio_error(3) returns something other than EINPROGRESS.
If the asynchronous I/O operation has completed, this function returns the value that would have been returned in case of a synchronous read, write, or fsync request. Otherwise the return value is undefined. On error, the error value is returned.
EINVAL aiocbp does not point at a control block for an asynchronous I/O request of which the return status has not been retrieved yet.