top: 'include' filter delimiter is missing : <p>I'm trying to filter top's output by command, but when I type <code>O</code>, then</p>

<pre><code>COMMAND?apache2
</code></pre>

<p>I get the following error:</p>

<pre><code>'include' filter delimiter is missing
</code></pre>

<p>I've looked at the top man page, but can't seem to work out what's going on.</p>
