title: Replace special characters in a string with _ (underscore)
body: <p>I want to remove special characters from a string and replace them with the <code>_</code> character.</p>
  
  <p>For example:</p>
  
  <pre><code>string = "img_realtime_tr~ading3$"
  </code></pre>
  
  <p>The resulting string should look like "img_realtime_tr_ading3_";</p>
  
  <p>I need to replace those characters: <code>&amp; / \ # , + ( ) $ ~ % .. ' " : * ? &lt; &gt; { }</code></p>