Bash helper function to get a specific environment variable from a Docker container

docker_get_env.sh

#!/bin/bash

# Retrieves an enviroment variable from a docker container
docker_get_env()
{
    env_json=$(docker inspect --format '{{ json .Config.Env }}' ${1})
    length=$(echo ${env_json} | jq '. | length')

    for (( i=0; i<${length}; i++ ))
    do
       item=$(echo ${env_json} | jq '.['${i}']')
       item=$(echo "[" $(echo -n ${item} | sed -n 's/=/", "/p') "]")

       key=$(echo ${item} | jq '.[0]')
       value=$(echo ${item} | jq '.[1]' --raw-output)

        if [[ ${key} == *"$2"* ]]; then
            echo ${value}
            return 0
        fi
    done

    return 1
}

# Usage
password=$(docker_get_env my-db-container MYSQL_ROOT_PASSWORD)
echo $password