How to forward a variable to a container?

Question

Docker

Until today, I had no dealings with Docker, so I apologize if my question seems naive.

I want to achieve that every time the container is launched weba, a new value is generated HOST. I generate it via bash and save it in $HOST.

How to forward a variable to a container?

version: '3'

services:
  nginx-proxy:
    image: jwilder/nginx-proxy
    ports:
      - 8080:80
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro

  weba:
    build:
      context: web/a
    expose:
      - 8081
    environment:
      - VIRTUAL_HOST=${HOST}.localhost
    depends_on:
      - nginx-proxy

What command can I do this?

Answer 1

Environment variables in Compose. Example .
Use environment variables