title: How to use conditional control flow in awk
body: <p>I have a file whose content is like:</p>
  
  <pre><code>...
  ... Precision is ill-defined and being set to 0.0 due to no predicted samples ...
  ...
  Score metric (precision_score): 0.0
  ...
  </code></pre>
  
  <p>where the line containing <code>Precision is ill-defined and being set to 0.0 due to no predicted samples</code> may or may not exist, and the line containing <code>Score metric (precision_score):</code> may or may not exist.</p>
  
  <p>I want to use AWK to create a variable <code>precision</code>, and </p>
  
  <ul>
  <li><p>if the line containing <code>Precision is ill-defined and being set to 0.0 due to no predicted samples</code> exists, set the value of <code>precision</code> to <code>inf</code>, </p></li>
  <li><p>otherwise, if  the line containing <code>Score metric (precision_score):</code> exists, set the value of <code>precision</code> to the number following <code>Score metric (precision_score):</code></p></li>
  </ul>
  
  <p>I wonder how to implement that in awk? Thanks.</p>