title: Bash: how to take a number from string? (regular expression maybe)
body: <p>I want to get a count of symbols in a file.</p>
  
  <pre><code>wc -c f1.txt | grep [0-9]
  </code></pre>
  
  <p>But this code return a line where grep found numbers. I want to retrun only <strong>38</strong>. How?</p>