Two simple programs using Linux AIO interface:

aio_passwd.c reads /etc/passwd. It doesn't do it in truly async way (since the file is not opened with O_DIRECT), but it's good to illustrate the blocking nature of io_submit.

aio_poll.c uses IOCB_CMD_POLL to wait for a packet from a networking socet, in truly async way. The io_submit does not block and we are blocking in io_getevents, awaiting POLLIN event notification. This requires kernel 4.18 or newer.