re flags that users specify on the
command line when they run an executable.  In the command</p>
<pre>
   fgrep -l -f /var/tmp/foo johannes brahms
</pre>
<p><code>-l</code> and <code>-f /var/tmp/foo</code> are the two
commandline flags.  (<code>johannes</code> and <code>brahms</code>,
which don't start with a dash, are <b>commandline arguments</b>.)</p>

<p>Typically, an application lists what flags the user is allowed to
pass in, and what arguments they take -- in this example,
<code>-l</code> takes no arg