A bash script waiting for port some host and port to become available without netcat or similar

wait-for.sh

#!/usr/bin/env bash
host=${1:?missing host}
port=${2:?missing port}
timeout=${3:-180}
until (exec 3<>"/dev/tcp/$host/$port") &>/dev/null; do
	((timeout == 0)) && exit 1
	((timeout--))
	echo -n .
	sleep 1
done
echo