docker-compose does not pass environment variable 'true', 'false', 'yes', 'no' (without quotes) unchanged to the container. YML parser recognizes these values as a boolean and converts them to either True or False. This is confusing since environment variables are generally just a string. I would expect all values to be passed to the container exactly as defined in the yml file as if they were a string.

Simple work around is to force them to be a string by quoting all environment variables.

test.sh

echo $SHOW

docker-compose.yml

test:
  image: ubuntu
  environment:
    SHOW: true
  command: sh /tmp/test.sh
  volumes:
    - './test.sh:/tmp/test.sh'

Expected Output:

test_1 | true

Actual Output:

test_1 | True

Work Around:

Put all environment variables in quotes to force it to behave as a string.

test:
  image: ubuntu
  environment:
    SHOW: 'true'
  command: sh /tmp/test.sh
  volumes:
    - './test.sh:/tmp/test.sh'