title: Grep with a variable
body: <p>I would like to <code>grep</code> a number of documents by using a set of search terms and to specify the number of characters after match. Here is what I tried</p>
  
  <pre><code>grep  -F -o -P "$(&lt;search.txt).{0,4}" foo.txt
  </code></pre>
  
  <p>but I get the message 'grep: conflicting matchers specified' because <code>-F</code> and '-oP' cannot be combined. It does not work with '-E' either. </p>