Is there a way to provide docker-compose env-file from stdin?-CodePudding

In docker run one can do

docker run --env-file <(env | grep ^APP_) ...

Is there a similar way for docker-compose? I would like to avoid physical env file.

CodePudding user response：

The equivalent of --env-file option of the docker cli in docker-compose is the env_file configuration option in the docker-compose file. But I think this requires a physical .env file.

If you want use the environment variables of your host machine, you can define them in docker-compose (with an optional fallback value):


version: "3.9"
services:
  app:
    image: myapp
    environment:
    - APP_MYVAR=${APP_MYVAR-fallbackvalue}

It's not so convenient as doing a grep of your ^APP_ vars, but one way to avoid the physical file.

CodePudding user response：

You can do it by supplying multiple compose files, as documented here. In your case the first one is a physical docker-compose.yml and the second one a Compose containing only the environment variables for the needed service. Obviously, env variables must be properly formatted, so a sed that prepends the string - is necessary because they are added as YAML list.

docker-compose -f docker-compose.yml -f <(printf "services:
  your_service:
    environment:\n$(env | grep ^APP_ | sed -e "s/^/    - /")"
) up

This is how Docker behaves:

When you supply multiple files, Compose combines them into a single configuration. Compose builds the configuration in the order you supply the files. Subsequent files override and add to their predecessors