Ubuntu 14.04lts with Perl 5.18.2.

This is a special case where Google did not help me. I do not want to turn off email for all cron jobs, I have about 15 jobs in my crontab. I need to see the emails cron sends me if there are errors.

This one job is a special case for which I need a solution. I have a bash script in my crontab which calls a perl script which is setup to check for email every 5 minutes. (It is not possible for me to setup a full MTA.) If there is no email the script does not output anything to STDOUT or STDERR yet cron still sends me a blank email with the full path of the bash script in the subject.

  1. I want cron and the Perl script to send me email if the perl script finds email and processes it, including if there are errors.
  2. I don't want cron to send me a blank email if there is no output from the Perl script because no email was found. The script runs every 5 minutes.

Anyone have any ideas?

EDIT: Confirmed. It was a stray newline that was my problem. Problem solved. Cron does not send an email if there is no output. Thank you! Your comment helped.

  • 3
    cron doesn't send mails on no output. Are you sure it is printing nothing to stderr/out? Not even blank lines or whitespace?
    – muru
    Dec 22 '14 at 19:31
  • I'm testing this right now. I found a newline and removed it. So far, no emails. I couldn't see the newline in alpine, my email reader.
    – Bulrush
    Dec 22 '14 at 19:40

It was a stray newline causing the blank email every 5 minutes.

Cron only sends an email if the cron job/program run has output. My output was a newline, which of course, I couldn't see in Alpine, but it was there. I found the newline that my program was printing and removed it.

Now I design my cron programs to never output anything unless it gets past the parameter checking.

  • Can you elaborate please? As it stands this answer is going to be deleted soon because it's too vague. Dec 23 '14 at 16:30
  • @DavidFoerster actually, it looks like that's all there is. cron doesn't send emails if there's no output, but if there's any output at all, even a blank line, it will send emails. Removing the superfluous newline was all that was necessary, it seems.
    – muru
    Dec 23 '14 at 17:07

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