Waiting for TCP connection is up using simple bash script

wait_for_tcp_socket_ready.sh

#!/bin/sh

# source : https://github.com/aanand/docker-wait/blob/master/wait

set -e

host=$(env | grep _TCP_ADDR | cut -d = -f 2)
port=$(env | grep _TCP_PORT | cut -d = -f 2)

echo -n "waiting for TCP connection to $host:$port..."

while ! nc -w 1 $host $port 2>/dev/null
do
  echo -n .
  sleep 1
done

echo 'ok'