Pass a variable to a Dockerfile from a docker-compose.yml file
<p>I have several docker-compose.yml files that I want to use the same Dockerfile with, with a slight variation. So I want to pass an argument to that Dockerfile so that I can do something slightly different depending on whatever value the variable is set to.</p>

<p><strong>What I have tried so far</strong></p>

<p>docker-compose-A.yml file</p>

<pre><code>version: '2'

services:
  django:
    build:
      context: .
      dockerfile: ./docker/Dockerfile
      args:
        - SOMETHING=foo
</code></pre>

<p>docker-compose-B.yml file</p>

<pre><code>version: '2'

services:
  django:
    build:
      context: .
      dockerfile: ./docker/Dockerfile
      args:
        - SOMETHING=bar
</code></pre>

<p>I have a dockerfile I want to use SOMETHING in. e.g.</p>

<pre><code># Dockerfile
RUN echo $SOMETHING
</code></pre>

<p>That doesn't work. SOMETHING is not passed to the dockerfile.</p>

<p>Am I doing this incorrectly or is this not the intended usage?</p>

<p>Is there any other way to pass a variable to a Dockerfile from a docker-compose.yml file?</p>