what is similar function to epoll's unregister function for kqueue?

Question

Python Epoll has function called epoll.unregister which removes a registered file descriptor from the epoll object. Does any one know what is the function in Kqueue which is similar this. For kqueue I could only find how to delete events.

Answer 1

You use kqueue.control to register or unregister an event.

An example:

import select
import os

os.mkfifo('my.fifo')
f = os.open('my.fifo', os.O_RDONLY|os.O_NONBLOCK)

try:
    kq = select.kqueue()

    # Add FD to the queue
    kq.control([select.kevent(f, select.KQ_FILTER_READ, select.KQ_EV_ADD|select.KQ_EV_ENABLE)], 0)

    # Should break as soon as we received something.
    i = 0
    while True:
        events = kq.control(None, 1, 1.0) # max_events, timeout
        print(i, events)
        i += 1
        if len(events) >= 1:
            print('We got:', os.read(f, events[0].data))
            break

    # Remove FD from the queue.
    kq.control([select.kevent(f, select.KQ_FILTER_READ, select.KQ_EV_DELETE)], 0)

    # Should never receive anything now even if we write to the pipe.
    i = 0
    while True:
        events = kq.control(None, 1, 1.0) # max_events, timeout
        print(i, events)
        i += 1
        if len(events) >= 1:
            print('We got:', os.read(f, events[0].data))
            break

finally:
    os.close(f)
    os.remove('my.fifo')

You could also check the test case for kqueue to see how it's used. (And like select(), the file descriptor could be any Python objects with a fileno() method as well.)