title: How to ensure only one file is returned by checking for newline
body: <p>What is the <em>simplest</em> way to check if a string contains newline?</p>
  
  <p>For example, after</p>
  
  <pre><code>FILE=$(find . -name "pattern_*.sh")
  </code></pre>
  
  <p>I'd like to check for newline to ensure only one file matched.</p>