Inside a crontab File

The cron daemon schedules system events according to commands found within each crontab file. A crontab file consists of commands, one per line, that will be executed at regular intervals. The beginning of each line contains date and time information that tells the cron daemon when to execute the command.

For example, a crontab file named root is supplied during SunOS software installation. Its contents include these command lines:

0 20 * * 0,4 /etc/cron.d/logchecker
 5  4 * * 0   /usr/lib/newsyslog
15  3 * * *   /usr/lib/fs/nfs/nfsfind
 1  2 * * *  [ -x /usr/sbin/rtc ] && /usr/sbin/rtc -c > /dev/null 2>&1

The first command line instructs the system to run logchecker at 10 on Sundays and Thursdays nights. The second command line schedules the system to run newsyslog at 4:05 every Sunday morning. The third command line orders the system to execute nfsfind daily at 3:15 in the morning The fourth command line instructs the system to check for daylight savings time and makes corrections if necessary. If there is no RTC time zone nor an /etc/rtc_config file, this entry will do nothing.

For more information about the syntax of lines within a crontab file, see "Syntax of crontab File Entries".

The crontab files are stored in /usr/spool/cron/crontabs (or /var/spool/cron/crontabs). Several crontab files besides root are provided during SunOS software installation (see Table 59-2).

Other crontab files are named after the user accounts in which they are created, such as bob, mary, smith, or jones.

Besides the default crontab file, users can create crontab files to schedule their own system events. To access crontab files belonging to root or other users, superuser privileges are required.

Procedures explaining how to create, edit, display, and remove crontab files are described in "Commands for Scheduling System Events".