NAME

cron − clock daemon

SYNOPSIS

/usr/sbin/cron

AVAILABILITY

SUNWcsr

DESCRIPTION

The cron command starts a process that executes commands at specified dates and times.  Regularly scheduled commands can be specified according to instructions found in crontab files in the directory /var/spool/cron/crontabs.  Users can submit their own crontab file using the crontab command.  Commands which are to be executed only once may be submitted using the at command. 

cron only examines crontab files and at command files during process initialization and when a file changes using the crontab or at commands.  This reduces the overhead of checking for new or changed files at regularly scheduled intervals. 

Since cron never exits, it should be executed only once.  This is done routinely through /etc/rc2.d/S75cron at system boot time.  /etc/cron.d/FIFO is used as a lock file to prevent the execution of more than one cron. 

To keep a log of all actions taken by cron, CRONLOG=YES (by default) must be specified in the /etc/default/cron file.  If CRONLOG=NO is specified, no logging is done.  Keeping the log is a user configurable option since cron usually creates huge log files. 

The PATH for user cron jobs can be set using PATH= in /etc/default/cron.  The PATH for root cron jobs can be set using SUPATH= in /etc/default/cron.  The security implications of setting PATH and SUPATH should be carefully considered. 

Example /etc/default/cron file:

CRONLOG=YES
PATH=/usr/bin:/usr/ucb:

This example enables logging and sets the default PATH used by non-root jobs to /usr/bin:/usr/ucb:.  Root jobs will continue to use /usr/sbin:/usr/bin. 

FILES

/etc/cron.d main cron directory

/etc/cron.d/FIFO used as a lock file

/etc/default/cron contains cron default settings

/var/cron/log accounting information

/var/spool/cron spool area

SEE ALSO

at(1), crontab(1), sh(1)

DIAGNOSTICS

A history of all actions taken by /var/cron/log. 

Sun Microsystems  —  Last change: 6 Mar 1993