cron(C)

cron -- execute commands scheduled by at, batch, and crontab

Syntax

/etc/cron

Description

The cron command is the clock daemon that executes commands at specified dates and times. cron processes jobs submitted with at(C), batch(C), and crontab(C). cron never exits; the cron command usually appears in the /etc/rc2 scripts to be invoked by init(M) when the system is brought up in multiuser mode.

The variable MAXCRON, if set in /etc/default/cron, controls the maximum number of running processes that cron can own at any one time. The default value is 100.

Diagnostics

A history of all actions by cron can be recorded in /usr/lib/cron/log. This logging occurs only if the variable CRONLOG is set to YES in /etc/default/cron. By default this value is set to NO and no logging occurs.

If logging is turned on, you can use the variable MAXLOGSIZE defined in /etc/default/cron to limit the size in 512-byte blocks to which the log file will grow. If it exceeds this limit, its contents are moved to /usr/lib/cron/olog. The default value of MAXLOGSIZE is 2048 blocks.

Limitations

cron will set the supplemental group list to that of the user requesting the job.

Files

/etc/default/cron: cron default configuration
/usr/lib/cron: main cron directory
/usr/lib/cron/atjobs: at directory
/usr/spool/cron/crontabs: crontab directory
/usr/lib/cron/log: accounting information
/usr/lib/cron/olog: overflow file for log file
/usr/lib/cron/queuedefs: cron data file

Standards conformance

cron is conformant with:

AT&T SVID Issue 2.