Make it work out of the box and a few slight changes

I didn't test it with `ip` command because I don't have it and I don't use Arch Linux, I mocked up a fake one for testing with sample output I found online, but modifications should be fine.

Since you set to Bash, I think it looks better to use not-so-much-newer (or Bash-only) syntax, like `[[ ]]` and `$( )`, but that's just my personal preference.

See your smac.sh [via forums](https://bbs.archlinux.org/viewtopic.php?pid=1225223#p1225223)