The cron(8) daemon examines cron entries once every minute.
Display of the user's crontab file is performed by crontab -l while editing is done with the -e switch. (Make sure that the EDITOR environment variable is set to your favorite editor program)
cronatb entries are date time fields followed by the command to be executed at that time. The time and date fields are:
|day of month||1-31|
|month||1-12 (or names, see below)|
|day of week||0-7 (0 or 7 is Sun, or use names)|
A field may be an asterisk (*), which always stands for ``first-last''.
Ranges of numbers are allowed. Ranges are two numbers separated with a hyphen. The specified range is inclusive. For example, 8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10 and 11.
Lists are allowed. A list is a set of numbers (or ranges) separated by commas. Examples: ``1,2,5,9'', ``0-4,8-12''.
Step values can be used in conjunction with ranges. Following a range with ``/
Names can also be used for the ``month'' and ``day of week'' fields. Use the first three letters of the particular day or month (case doesn't matter). Ranges or lists of names are not allowed.
EXAMPLE CRON FILE
# use /bin/sh to run commands, no matter what /etc/passwd says SHELL=/bin/sh # mail any output to `paul', no matter whose crontab this is MAILTO=paul # # run five minutes after midnight, every day 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 # run at 2:15pm on the first of every month -- output mailed to paul 15 14 1 * * $HOME/bin/monthly # run at 10 pm on weekdays, annoy Joe 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 5 4 * * sun echo "run at 5 after 4 every sunday"
Finally here is my DB Server crontab which backs up the entire database every day at 6:00pm and backups up the archive logs at past 35 every two hours.
oracle@poulcheria:~> crontab -l # DO NOT EDIT THIS FILE - edit the master and reinstall. # (/tmp/crontab.21301 installed on Fri Feb 2 09:45:47 2007) # (Cron version -- $Id: crontab.c,v 2.13 1994/01/17 03:20:37 vixie Exp $) 0 18 * * * /home/oracle/backup_jobs/perform_backup 35 */2 * * * /home/oracle/backup_jobs/perform_archlog_backup