Description of problem:

I've long been annoyed by

 $ sudo ether-wake mercury
Specify -i <interface>.

The man page of ether-wake says:

OPTIONS

       -i ifname
              Use interface ifname instead of the default "eth0".

but it's no longer true that "eth0" is the default.  These days, the default ethernet interface varies, so you have to probe to find the name.

I have a patch that iterates of all interfaces by default.