pcap_get_selectable_fd(3pcap) on macOS
The text 3802af6aced1, as Mac OS X 10.8.5, Mac OS X 10.8.4, Mac OS X 10.8.3, Mac OS X 10.8.2, Mac OS X 10.8.1, Mac OS X 10.8, Mac OS X 10.7.5, Mac OS X 10.7.4, Mac OS X 10.7.3, Mac OS X 10.7.2, Mac OS X 10.7.1, Mac OS X 10.7 shipped it.
get a file descriptor on which a select() can be done for a live capture