title: Grep multiple files using regex for specifying filenames to search for
body: <p>Let's say I have <code>n</code> files with names like <code>link123.txt</code>, <code>link345.txt</code>, <code>link645.txt</code>, etc.</p>
  <p>I'd like to grep a subset of these <code>n</code> files for a keyword. For example:</p>
  <pre class="lang-bash prettyprint-override"><code>grep 'searchtext' link123.txt link 345.txt ...
  </code></pre>
  <p>I'd like to do something like</p>
  <pre class="lang-bash prettyprint-override"><code>grep 'searchtext' link[123\|345].txt
  </code></pre>
  <p>How can I mention the filenames as regex in this case?</p>