shell 生成MAC地址

    # cat /dev/urandom |od -x |awk '{print $2,$3,$4}' |head -n 1 |sed -e 's/[[:space:]]//g' -e 's/\(..\)\(..\)\(..\)\(..\)\(..\)\(..\)/\1:\2:\3:\4:\5:\6/g'
    e7:43:de:52:5d:57