title: how to stop make -n from echoing same command multiple times
body: <p>I am using GNU make and have a <code>Makefile</code> which looks like this:</p>
  <pre><code>AB = A.txt B.txt
  
  ${AB}: makeAB.py
      python makeAB.py
  
  C.txt: ${AB} makeC.py
      python makeC.py
  </code></pre>
  <p>When I type <code>make -n C.txt</code>, assuming <code>makeAB.py</code> needs to run, I get the output:</p>
  <pre><code>python makeAB.py
  python makeAB.py
  python makeC.py
  </code></pre>
  <p>Is there any way to write the <code>Makefile</code> so that the line <code>python makeAB.py</code> is not repeated? This is just a toy example, but in my actual application <code>AB</code> consists of many files, so I potentially get a whole screen of unnecessary output.</p>
  <p>p.s. When called without <code>-n</code>, <code>make</code> (sensibly) only runs <code>python makeAB.py</code> once. So my problem is just with <code>make -n</code>.</p>