Controlling Processes - Solaris 9 System Administrator - page 115

Commands that are executed automatically by being placed in a crontab file
are referred to as cron jobs . Commands to be executed only once at a future
time can be submitted using the at command instead of modifying the
crontab s. The at command is described in the next section.
The two general classes of crontab s are system crontab s, which are owned
by system accounts such as root, lp, and so on, and user crontab s, which are
created and maintained by non-administrative user accounts.
Default cron Settings
Like other system utilities, parameters can be set to control the behavior of
the cron command. These settings are listed in the /etc/default/cron file.
The cron command will log its activities in the /var/cron/log file if the fol-
lowing entry is contained in the /etc/default/cron file:
CRONLOG=YES
This is the default. To disable logging, change YES to NO and reboot the sys-
tem or restart cron using the /etc/init.d/cron run control (rc) script.
Other entries that can be added to the /etc/default/cron include PATH ,
which sets the PATH shell environment parameter for user cron jobs, and
SUPATH , which sets the PATH shell environment variable for root cron jobs.
The following listing shows the PATH and SUPATH settings:
PATH=/usr/bin:/usr/ucb:
SUPATH=/usr/sbin:/usr/bin:
The crontab Files
The /var/spool/cron/crontabs directory contains both the system and
the user crontab files. These files have the same name as the account name
of the owner. For example, the crontab for the guest user account is named
guest .
The crontab file contains entries that specify a command to execute along
with a time and frequency of execution. Commands can be executed daily,
weekly, or monthly at any time of the day.
A crontab entry consists of six fields separated by spaces or tabs. An asterisk
(*) is used as a placeholder in a field that is not used. Table 5.5 lists the fields
of a crontab entry.