How to use environment variables in docker compose

Question

I would like to be able to use env variables inside docker-compose.yml, with values passed in at the time of docker-compose up. This is the example.

I am

Answer 1

It seems that docker-compose has native support now for default environment variables in file.

all you need to do is declare your variables in a file named .env and they will be available in docker-compose.yml.

For example, for .env file with contents:

MY_SECRET_KEY=SOME_SECRET
IMAGE_NAME=docker_image

You could access your variable inside docker-compose.yml or forward them into the container:

my-service:
  image: ${IMAGE_NAME}
  environment:
    MY_SECRET_KEY: ${MY_SECRET_KEY}