Find the IP of a Raspberry Pi (or any computer really) on the network by MAC

findbymac.sh

#!/bin/bash
#
# Find the IP address of a client by MAC on the same network. Sudo privilege and nmap required.
#
# usage: ./findbymac.sh <MAC_ADDRESS>
#
# The first argument to the script is the MAC address or part of the MAC address.
# 
# example: sudo ./findbymac.sh "aa:b8"
#

if [ $# -eq 0 ] 
  then
    echo "usage: $0 <MAC_ADDRESS>"
    exit 1
fi
if ! [ -x "$(command -v nmap)" ]
  then
    echo "Please install nmap"
    exit 1
fi
MAC=$1
LOCALIP=$(hostname -I | awk '{print $1}')
MASK=$(echo "$IP" | sed 's/[0-9]\+/0\/24/4')
TARGETIP=$(sudo nmap -sP $MASK | grep -B 2 -i "$MAC" | head -n 1 | awk '{print $5}')
echo $TARGETIP