3.3.3 Extensions and incompatibilities

This section lists differences between Paul Vixie’s cron and the olde-worlde BSD and AT&T programs, for the benefit of system administrators and users who are upgrading all the way.

• When specifying day of week, both day 0 and day 7 will be considered Sunday. BSD and AT&T seem to disagree about this.
• Lists and ranges are allowed to co-exist in the same field. "1-3,7-9" would be rejected by AT&T or BSD cron – they want to see "1-3" or "7,8,9" ONLY.
• Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9".
• Names of months or days of the week can be specified by name.
• Environment variables can be set in the crontab. In BSD or AT&T, the environment handed to child processes is basically the one from /etc/rc.
• Command output is mailed to the crontab owner (BSD can’t do this), can be mailed to a person other than the crontab owner (SysV can’t do this), or the feature can be turned off and no mail will be sent at all (SysV can’t do this either).