title: Way to pass a script as a docker build argument?
body: <p>I want to pass a multi-line script as a argument to docker build command, something like that:</p>
  
  <pre><code>docker build -t tertparam --build-arg load_cat_agent=true --build-arg deploy_cat_script='
  echo "aaa";
  echo "bbb"
  ' --no-cache .
  </code></pre>
  
  <p>and execute it during build, my Dockerfile is like </p>
  
  <pre><code>FROM python:3-alpine
  
  ARG load_cat_agent
  ARG deploy_cat_script
  
  ADD . /root/
  WORKDIR /root/
  
  RUN if [ $load_cat_agent == "true" ]; then \
           $deploy_cat_script;\
      fi
      CMD /root/start.sh &amp;&amp; /root/wait.sh
  </code></pre>
  
  <p>but i found that it always just print </p>
  
  <pre><code>Step 6/7 : RUN if [ $load_cat_agent == "true" ]; then    $deploy_cat_script;    fi
   ---&gt; Running in 7868c310e8e5
  
  "aaa" echo "bbb"
  </code></pre>
  
  <p>how can i do that?</p>