Because mostly you are just shelling out. Also you can't just use any mac addr as some bits are reserved, e.g. multicast. But you can collapse that as so or su

Because mostly you are just shelling out. Also you can't just use any mac addr as some bits are reserved, e.g. multicast. But you can collapse that as so or suchlike: ifconfig eth34 hw ether $(openssl rand 6 | xxd -p | sed 's/\(..\)/\1:/g; s/:$//') Obviously doing this is wrong anyway but that will do what your script does.