title: Docker run time environment variable is not available
body: <p>I have the need to pass a variable at runtime when the docker run command is run and the same is to be read inside the container.</p>
  
  <p>This is the docker run command that i use</p>
  
  <pre><code>docker run  -it -e "URL=test" test bash
  </code></pre>
  
  <p>But the variable URL is not available inside the container. My Dockerfile as below</p>
  
  <pre><code>FROM ubuntu
  
  RUN apt-get update
  RUN echo "test"
  RUN echo "The url is " $URL &gt;&gt; /out.log
  </code></pre>
  
  <p>Inside the container, out.log shows only the following ouput</p>
  
  <blockquote>
    <p>The url is</p>
  </blockquote>
  
  <p>What am i missing?</p>