Shell script to set a static ip address in the systemd network unit. Needs sudo to write the file

set-static-ip.sh

#! /usr/bin/env bash

if [ "$#" -eq "0" ]; then
	echo "Usage: $0 <desired-ip-address>"
	curr_ip="$(ip route get 1.1.1.1 | awk '{print$7}')"
	echo "FYI your current IP address is: $curr_ip"
	exit 1
fi

# TODO: check if input looks like an ip

name=$(ip route get 1.1.1.1 | awk '{print$5}' | head -n1)
file="/etc/systemd/network/$name.network"
if [ -s "$file" ]; then
	echo "File $file already exists. Check the file contents and delete it if not important"
	exit 1
fi

cat >"$file" <<EOF
[Match]
Name=$name

[Network]
Address=$1
Gateway=$(ip route get 1.1.1.1 | awk '{print$3}' | head -n1)
DNS=8.8.8.8
DNS=8.8.4.4
EOF