macOS script to toggle between static ip and dhcp using different routers

switch-network.sh

#!/usr/bin/env bash
set -euo pipefail

inetInterfaceIp=$( \
    ifconfig \
      | perl -0777 -pe 's/\n+^[ \t]/ /gm' \
      | grep 'inet ' \
      | grep RUNNING \
      | grep -v LOOPBACK \
      | sed -nE 's/([a-z0-9]+).* inet ([^ ]+).*/\1 \2/p' \
      | grep -vE '\.1$' \
      | head -n1
)

inetInterface=$(echo "$inetInterfaceIp" | awk '{ print $1 }')
inetIp=$(echo "$inetInterfaceIp" | awk '{ print $2 }')
networkSetupInterface=$( \
    networksetup -listallhardwareports \
      | grep -E 'Port:|Device:' \
      | sed 's/Hardware /\n/' \
      | sed -E 's/[A-Za-z]+: //g' \
      | grep . \
      | perl -0777 -pe 's/^(.+)\n(.+)/\2 \1/gm' \
      | awk '$1 == "'"$inetInterface"'" { print $0 }' \
      | sed -E 's/[^ ]+ //'
  )

router=${1:-}

if [[ "$router" == "0" ]] || [[ "$router" == "" ]] && [[ "$inetIp" != 192.168.100.* ]]; then
  echo "Setting $networkSetupInterface ($inetInterface) DHCP"
  networksetup -setdhcp "$networkSetupInterface"
  networksetup -setdnsservers "$networkSetupInterface" Empty
else
  lastOctet=$(echo "$inetIp" | cut -d. -f4)
  if [[ "$router" == "" ]]; then
    router="2"
  fi
  newIp="192.168.$router.$lastOctet"
  echo "Setting $networkSetupInterface ($inetInterface) Static IP $newIp"
  networksetup -setmanual "$networkSetupInterface" "$newIp" 255.255.255.0 "192.168.$router.1"
  networksetup -setdnsservers "$networkSetupInterface" 1.1.1.1 9.9.9.9
fi