Just a minor quibble: the comments says this works on a *nix network interface, however, as far as I know it will only work on Linux. All the other Unix OSes I've worked with that implement the /proc filesystem only do so for processes. All the other funky directories don't exist.

But then there's always RRDtool for the rest :)

I also have a couple of machines running linux with dual-port NICs, and the oafs who wrote the drivers found nothing better to do than to create their own special directory under /proc. I don't have the details handy, but I'll update when I'm back at work.