Variable substitution in docker-compose command - variables

Question

I need to pass env variable from file to a command in a docker-compose but it seems impossible.
So I try first with environment var but it doesn't work again. How can I do that?
version: '3'
services:
nginx-service-xxx:
image: service-xxx-nginx:latest
ports:
- 80:80
restart: always
service-xxx:
image: service-xxx:latest
# env_file:
# - db-settings.env
environment:
- PORT=80
- PG-HOST=192.168.0.101
- PG-DATABASE=xxx
- PG-USER=postgres
- PG-PASSWORD=postgres
restart: always
command: python xxx/main.py --port=$$PORT --pg-host=$$PG-HOST --pg-database=$$PG-DATABASE --pg-user=$$PG-USER --pg-password=$$PG-PASSWORD

Answer 1

try to move the complexity of the command to a docker entry point.
First, you need to add the following entry point to your project (make it executable)
#!/bin/bash -e
case $1 in
web)
python xxx/main.py --port=$PORT --pg-host=$PG-HOST --pg-database=$PG-DATABASE --pg-user=$PG-USER --pg-password=$PG-PASSWORD
;;
*)
exec "$#"
;;
esac
exit 0
update the docker file for your service
From base-image
COPY ./docker-entrypoint.sh /
ENTRYPOINT ["/docker-entrypoint.sh"]
update compose
version: '3'
services:
nginx-service-xxx:
image: service-xxx-nginx:latest
ports:
- 80:80
restart: always
service-xxx:
image: service-xxx:latest
environment:
- PORT=80
- PG-HOST=192.168.0.101
- PG-DATABASE=xxx
- PG-USER=postgres
- PG-PASSWORD=postgres
restart: always
command: web