title: Docker exec quoting variables
body: <p>I'd like to know if there's a way to do this</p>
  
  <p>Let's say the <code>dockerfile</code> contains this line, that specifies path of an executable</p>
  
  <p><code>ENV CLI /usr/local/bin/myprogram</code></p>
  
  <p>I'd like to be able to call this program using ENV variable name through <code>exec</code> command.</p>
  
  <p>For example
  <code>docker exec -it &lt;my container&gt; 'echo something-${CLI}</code>
  Expecting 
  <code>something-/usr/local/bin/myprogram</code></p>
  
  <p>However that returns:</p>
  
  <p><code>OCI runtime exec failed: exec failed: container_linux.go:348: starting container process caused "exec: \"${CLI} do something\": executable file not found in $PATH": unknown</code></p>