How to log cron jobs?
* * * * * myjob.sh >> /var/log/myjob.log 2>&1
will log all output from the cron job to /var/log/myjob.log
You might use mail to send emails. Most systems will send unhandled cron job output by email to root or the corresponding user.
By default cron logs to /var/log/syslog so you can see cron related entries by using:
grep CRON /var/log/syslog
https://askubuntu.com/questions/56683/where-is-the-cron-crontab-log