title: Cron send email with STDERR but NOT STDOUT?
body: <p>I have some python scripts that run on a daily basis in cron.  How can I have cron send me an email <em>ONLY WHEN THERE IS STDERR OUTPUT</em> from my script?  I want to be able to mail multiple recipients, and set the subject line individually for each cron entry.</p>
  
  <p>I tried this:</p>
  
  <pre><code>./prog &gt; /dev/null | mail . . . 
  </code></pre>
  
  <p>but it didn't work -- I still receive blank emails when there is no STDERR.  Do I need to do this in the script itself?</p>
  
  <p>Sorry if this seems basic, I have googled a lot but can't seem to find this answered succintly.</p>