Ok. I didn't know whether ioctl could be used in some other way to obtain the 'down' interfaces as well. That was more my reason for asking. I wasn't (intentionally) trying to be annoyingly pedantic. »

Just to be clear... the show_ints code can only see interfaces which are in an 'up' state. If you were truly doing interface discovery (i.e. for an installer or some such) and no interfaces are in a configured state, what would the code look like to identify the interfaces? »