title: Appending to file, sed unterminated address regex
body: <p>I'm trying to append to the end of a file, using the style from this <a href="https://unix.stackexchange.com/a/26639/179769">answer</a> but I get the error:</p>
  
  <blockquote>
    <p>sed: -e expression #1, char 16: unterminated address regex</p>
  </blockquote>
  
  <p>the command (I've also tried without the <code>-i</code> and same error):</p>
  
  <pre><code>sed -i -e '\$ahaha_value=26' example.txt
  </code></pre>
  
  <p>where I'm expecting <code>$</code> to get the end of the file and <code>a</code> to append.</p>
  
  <p>I've looked at these questions <a href="https://stackoverflow.com/questions/27729772/unterminated-address-regex-while-using-sed">here</a>, <a href="https://stackoverflow.com/questions/39772457/sed-e-expression-1-char-16-unterminated-address-regex">here</a>, and <a href="https://stackoverflow.com/questions/22234430/sed-unterminated-address-regex">here</a>. The issues there seem to be regex based and I don't see the issue with my regex.</p>