how to get external ip address?

[microstarwwx]

Does anybody know how to get external ip address with c and socket?

To make things clear,

A linux machine may have multiple ip address, for example,

127.0.0.1 (local ip address)
198.12.1.12 (external address)

if there a c function like getaddrinfo(..) which can get the external address(198.12.1.12), rather than the local address(127.0.0.1)?

Thanks a lot.

[GNU-Fan]

I don't know how, but the tool ifconfig can tell such things.
So I would browse the source code of that tool to look how it does the job.