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

I have a simple bash script I created for this it just means running it on your file before use: https://github.com/antonosmond/subber

Basically just create your compose file using double curly braces to denote environment variables e.g:

app:
    build: "{{APP_PATH}}"
ports:
    - "{{APP_PORT_MAP}}"

Anything in double curly braces will be replaced with the environment variable of the same name so if I had the following environment variables set:

APP_PATH=~/my_app/build
APP_PORT_MAP=5000:5000

on running subber docker-compose.yml the resulting file would look like:

app:
    build: "~/my_app/build"
ports:
    - "5000:5000"