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

Remember, on Linux "everything" is a file.

The best way would be to use the approved kernel<->userspace communication, namely sysfs, mounted at /sys. Network devices are linked at /sys/class/net

If you wish to use the ioctl interface, look at man netdevice