|CRON(8)||System Manager's Manual||CRON(8)|
crondaemon schedules commands to be run at specified dates and times. Commands that are to be run periodically are specified within crontab(5) files. Commands that are only to be run once are scheduled via the at(1) and batch(1) commands. Normally, the
crondaemon is started from the /etc/rc command script. Because it can execute commands on a user's behalf,
cronshould be run late in the startup sequence, as close to the time when logins are accepted as possible.
cronloads crontab(5) and at(1) files when it starts up and also when changes are made via the crontab(1) and at(1) commands. Additionally,
cronchecks the modification time on the system crontab file (/etc/crontab), the crontab spool (/var/cron/tabs), and the at spool (/var/cron/atjobs) once a minute. If the modification time has changed, the affected files are reloaded. Any output produced by a command is sent to the user specified in the
MAILTOenvironment variable as set in the crontab(5) file or, if no
MAILTOvariable is set (or if this is an at(1) or batch(1) job), to the job's owner. If a command produces no output or if the
MAILTOenvironment variable is set to the empty string, no mail will be sent. The exception to this is at(1) or batch(1) jobs submitted with the
-mflag. In this case, mail will be sent even if the job produces no output.
cronwill detach from the current tty and become a daemon. The
-noption disables this behavior and causes it to run in the foreground.
cronto check for crontab changes immediately
|November 12, 2015||OpenBSD-6.0|