Cirnath: I didn't think you were trying to be pedantic - it's a good point. Browsing through the header files SIOCGIFCONF is the only function I see that returns a list of interfaces and, as you correctly point out, it doesn't return down interfaces - if it doesn't have an IP address. A down interface with an IP address does show up (how weird is that?) I guess the behaviour of SIOCGIFCONF is down to the whim of the kernel developers. »

Yes you are correct, I probably should have made that clear in the article. I'm just really trying to demonstrate ioctls calls rather write a fully fledged "interface discovery" utility. If I were, I'd probably just get them out of /proc/net/dev. But thanks for the clarification. »

Thanks for the feedback Rakesh. The article appeared in Linux Magazine a couple of months ago, so they are responsible for publishing the article on-line. To save space the editor took the code listings out and put them on the web. I don't know why the URL doesn't work, but I've let them know - hopefully it will be fixed soon. However, as an alternative, I've put the tar file here: http://agholt.googlepages.com/ioctl.tar.gz »