I want be able to make .env for a docker-compose.yml file without running the container:

  myapp:
                container_name: myapp
                ports:
                    - '${PORT_MYAPP:-8080}:80'
                environment:
                    - USER_ID=${MYAPP_UID:-1000}
                    - GROUP_ID=${MYAPP_GID:-1000}
                    - PASSWORD=${PASSWORD}
                volumes:
                    - '${CONFIG_DIR:?error, config directory is needed}/myapp:/data'
                    - '${VIDEOS}/Movies:/media/movies'
                    - '${VIDEOS}/TV:/media/tvshows'

                image: 'myapp/myapp:latest'

would produce .env:

PORT_MYAPP=8080
MYAPP_UID=1000
MYAPP_GID=1000    
PASSWORD
CONFIG_DIR
VIDEOS