#!/bin/sh set -e export LANG=C ip -brief link show dev "$1" | read iface state mac rest which="" while read testmac scheme; do if [ "$which" ]; then continue; fi if [ "$mac" = "$(echo "$testmac" | tr A-F a-f)" ]; then which="$scheme"; fi done if [ "$which" ]; then echo "$which"; else exit 1; fi