title: How to display the value of all the variables in Makefile
body: <p>I am learning how to write Makefile. I found the .VARIABLES variable which holds all the variables valid in Makefile. </p>
  
  <p>I can check the variables' name with command like this:</p>
  
  <pre><code>test:
      @echo "${.VARIABLES}" | tr ' ' '\n'
  </code></pre>
  
  <p>But I don't know how to should the values of them. Can anyone teach me to to do that?</p>