Dirección MAC Address
cat strings.txt | grep -a -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}'

Dirección IP
cat strings.txt | grep -a -o -E '([0-9]{1,3}[\.]){3}[0-9]{1,3}'

Correo electrónico
cat strings.txt | grep -a -o -E "\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b"

URL
cat strings.txt | grep -a -o -E '\b(https?|ftp|file)://[-A-Za-z0-9+&@#/%?=~_|!:,.;]*[-A-Za-z0-9+&@#/%=~_|]'
O más simple:
cat strings.txt | grep -a -o -E '\b(https?|ftp|file)://[-A-Za-z0-9+/%?=_.]*[-A-Za-z0-9+/%=_]'