Simple bash script that waiting hosts in environment. Usable with docker compose, when some containers not started and we doesn't have some host in environment.

wait_until_hosts.sh

#!/bin/bash
hosts=( "$@" )
total_hosts=${#hosts[@]}

while :
do
    l_hosts=( ${hosts[@]} )

    for i in ${!l_hosts[@]}
    do
        host=${l_hosts[$i]}
        if [[ $(ping $host -c 1 -W 1 2>&1 | grep unknown) ]];
        then
            :
        else
            # Host success
            total_hosts=$(expr $total_hosts - 1)
            hosts[$i]=""
        fi
    done

    if [[ 0 -ne $total_hosts ]];
    then
        sleep 0.4
    else
        exit 0
    fi

done

Usage:

./wait_until_hosts.sh mysql.dev some-other-host