A shell script to toggle NIC MAC addresses between the factory default and a new random one

remac.sh

#!/bin/bash

if [ "$#" -ne 1 ]; then
  echo "Network device must be specified"
  exit 1
fi

DEVICE="$1"

OLD_MAC=$(ifconfig | grep "$DEVICE:" -A3 | grep ether | head -1 | cut -d ' ' -f 2)
NEW_MAC=$(openssl rand -hex 6 | sed 's/\(..\)/\1:/g;s/.$//')

if [ -z "$OLD_MAC" ]; then
  echo "Invalid network device specified"
  exit 1
fi

CONFIG_FILE="$HOME/.mac_address_$DEVICE"

if [ ! -f "$CONFIG_FILE" ]; then
  echo "$OLD_MAC" > "$CONFIG_FILE"
  ORIGINAL_MAC="$OLD_MAC"
else
  ORIGINAL_MAC=$(cat "$CONFIG_FILE")
fi

if [ "$OLD_MAC" == "$ORIGINAL_MAC" ]; then
  echo Setting new mac address: "$NEW_MAC"
  sudo ifconfig $DEVICE ether "$NEW_MAC"
else
  echo Resetting mac to original: "$ORIGINAL_MAC"
  sudo ifconfig $DEVICE ether "$ORIGINAL_MAC"
fi