On Linux: how can I programmatically determine if a NIC interface is enabled and plugged in?

Question

I want to determine if a network card is enabled, up, and plugged in. Basically, I want to know if the network card will work. I need this information from with a C++ program, a

Answer 1

1. open AF_NETLINK socket
2. bind it to sockaddr_nl with nl_groups = RTMGRP_LINK
3. send message RTM_GETLINK to kernel
4. make poll/epoll on socket to read RTM_NEWLINK and RTM_DELLINK messages
5. you will receive initial interfaces list and its changes in future