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

Since 1.25.4, docker-compose supports the option --env-file that enables you to specify a file containing variables.

Yours should look like this:

hostname=my-host-name

And the command:

docker-compose --env-file /path/to/my-env-file config