ifconfig MAC changer

#! /bin/bash
#This script changes the mac address of a specified interface in modern linux OSes using only (mostly) the ifconfig command.
#It should work out of the box without any third party downloads.
#Noah B.
#Last edit 2/2/2016

#Prompt for root
[ "$UID" -eq 0 ] || exec sudo bash "$0" "$@"

int=$1

#if no int specified, ask for one
if [ -z "$int" ]
then
    read -p "Enter interface: " int
fi
if [ ! -z "$int" ]

if ! [ -z $2 ]
then
    newmac="$2"
else
    newmac="02:"`cat /dev/urandom | tr -dc 'A-F0-9' | fold -w 10 | head -n 1 | sed 's/\(..\)/\1:/g;s/:$//'`
fi

curmac=`ifconfig $int | grep -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}'`

#take down int
then
    printf "\nTaking down interface...\n\n"
sleep 1
ifconfig $int down
echo "Current (old) MAC for $int: $curmac"

sleep 1

#change mac address
ifconfig $int hw ether $newmac
#bring up int & restart netmanager
printf "\nMAC changed, bringing interface up and restarting netman...\n\n"
sleep 1
ifconfig $int up
service network-manager restart
#update curmac value
curmac=`ifconfig $int | grep -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}'`
printf "\nCurrent (new) MAC for $int: $curmac\n"
#ifconfig $int
else
echo "error"
fi