A bash script which checks the status of a web server before executing commands.

wait-for-webserver.sh

#!/bin/bash
# wait-for-nlu.sh

set -e

host="$1"
shift
cmd="$@"

http_status="$(curl -s -o /dev/null -I -w "%{http_code}" http://www.webserver.com:8080/)"
while [ $http_status -ne 200 ] 
do
    >&2 echo "NLU service is unavailable - sleeping"
    sleep 10
    http_status=http_status
done

>&2 echo "NLU service is up - executing command"
exec $cmd