Unable to set a docker image envar with another envar

Build Environment
5

Thank you for your quick reply, Jaryt.

Something is puzzling me with this approach you proposed. The appending that takes place on BASH_ENV would occur only after the spin up of the postgres image which requires the configuration. It fails right away.

image
image651×1192 109 KB

Am I missing something here? Is there a way to execute this command before the docker part comes into play? Here is my config.yml now:

config.yml 
version: 2.1
orbs:
  ruby: circleci/ruby@0.1.2

jobs:
  build:
    docker:
      - image: circleci/ruby:2.6.3-stretch-node
        environment:
          RAILS_ENV: test
          RACK_ENV: test
      - image: postgres:12.3
    executor: ruby/default
    steps:
      - run:
          name: Define Environment Variables at Runtime
          command: |
            echo 'export POSTGRES_USER=$TEST_DB_USERNAME' >> $BASH_ENV
            echo 'export POSTGRES_PASSWORD=$TEST_DB_PASSWORD' >> $BASH_ENV
            echo 'export POSTGRES_DB=$TEST_DB_NAME' >> $BASH_ENV
            source $BASH_ENV
      ...