Docker ENTRYPOINT for env check before container start

!check_env.sh

#!/bin/bash

echo "Environment variables check:"

declare -a unset=()

while IFS= read -r line
do
    var_name="${line//=}"
    if [[ -z "${!var_name+x}" ]]; then
        echo "- $var_name is unset."
        unset+=($var_name)
    fi
    
done < ".env"


if (( ${#unset[@]} > 0)); then
    echo "${#unset[@]} unset vars. Exit! 🛑"
    exit 1
else
    echo "All vars set. Continue! ✅"
fi

.env

APP_NAME=
ENV_NAME=
APP_PORT=

entrypoint.sh

#!/bin/sh

set -e
./check_env.sh

exec "$@"