Instructions are missing a vital line...

[owenBoyle]

It is not entirely clear that by cron expression you mean including the job definition.

So * * * * * myjob.sh parses, but * * * * * doesn't.

Call me paranoid, but I only wanted to parse the time definition part and didn't want to paste in my embarassing job-name. So it took me ages to understand how to get it to work.

After that, it was plain sailing!

[danielmotaleite]

just add a true or something else:

   * * * * * true