In Linux, it is pretty simple to find out the MAC address.
If you analyze properly, the interface name and the first and last fields on a line containing no leading whitespace.
But If any one of the indented lines has inet addr: the latest interface name and MAC address should be printed.
ifconfig -a |
awk '/^[a-z]/ { iface=$1; mac=$NF; next }
/inet addr:/ { print iface, mac }'
You should note it down that multiple interfaces can meet your criteria. Then, the multiple lines will be printed by scripts. If you only want to print the first match, add; exit right before the final closing brace.