This is incredibly simple, but it’s amazing how many people (ab)use Perl to do something that awk was designed for.

Here’s how to find your existing Linux styled ethernet interfaces:

%ifconfig -a | awk '(/inet\ addr/||/^eth/||/^lo/)&&!/127/ \
gsub(/inet\ addr:/, "") { print $1}'
eth0
10.10.0.212
eth1
85.92.154.212
eth1:1
192.168.30.1
lo
127.0.0.1

Those of you who might be able to read that will ask: Why not /127/? It’s a dummy test. :)