@[Link("pcap")]
lib LibPcap
  PCAP_ERRBUF_SIZE = UInt8.new(256)
  fun pcap_lookupdev(errbuf : LibC::Char* ) : LibC::Char*
end

err = LibPcap::PCAP_ERRBUF_SIZE.dup
dev = LibPcap.pcap_lookupdev(pointerof(err))

raise Exception.new("Couldn't find a default interface: #{String.new(err)}") if dev.null?

puts String.new(dev)