How user variable inside another variable in docker-compose.yml

Question

I have a .env file like this:

PROJECT_DIR=./test_dir
SUB_DIR=$(PROJECT_DIR)/sub_dir

And docker-compose.yml file like this:

version: '3.5'

services:
    service_nginx:
        image: nginx
        volumes:
            - ${SUB_DIR}:/var/www/html

But I can't use $SUB_DIR in docker-compose.yml file for volume, I got error like this:

ERROR: Named volume "$(PROJECT_DIR)/sub_dir:/var/www/html:rw" is used in service "service_nginx" but no declaration was found in the volumes section.

Does this answer your question? [Using environment variable for volume name in docker compose](https://stackoverflow.com/questions/45103843/using-environment-variable-for-volume-name-in-docker-compose) — D Malan, Jan 22 '20 at 12:15
You could try [this](https://github.com/docker/compose/issues/2636#issuecomment-363688635). — D Malan, Jan 22 '20 at 12:26
@DelenaMalan I don't have problem with using variable. The problem is there is a variable inside the variable — saderi, Jan 22 '20 at 12:42

score 1 · Answer 1 · answered Jan 22 '20 at 14:36

1

Update your env file as follows

export PROJECT_DIR=./test_dir
export SUB_DIR=$(PROJECT_DIR)/sub_dir

Then run the following command to read the varialbes;

. ./.env

Then deploy the stack from same terminal session.

answered Jan 22 '20 at 14:36

Nitish

1 Answers1