title: Docker image wait for postgres image to start - without Bash
body: <p>I have a standard Python docker image that needs to start after postgers is properly started in its standard image.</p>
  <p>I understand that I can add this Bash command in the docker-compose file:</p>
  <pre><code>command: bash -c 'while !&lt;/dev/tcp/db/5432; do sleep 1; done; npm start'
  depends_on:
    - mypostgres
  </code></pre>
  <p>But I don't have bash installed in the standard python docker image, and I'm trying to keep the installation minimal.</p>
  <p><strong>Is there a way to wait for postgres without having bash installed in my image?</strong></p>