The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
System cron jobs are defined in
crontab-format files in
/etc/crontab or in files in
/etc/cron.d. A crontab file
usually consists of definitions for the SHELL,
PATH, MAILTO, and
HOME variables for the environment in which the
jobs run, followed by the job definitions themselves. Comment
lines start with a # character. Job definitions
are specified in the following format:
minute hour day month day-of-week user commandwhere the fields are:
-
minute 0-59.
-
hour 0-23.
-
day 1-31.
-
month 1-12 or
jan,feb,...,dec.-
day-of-week 0-7 (Sunday is 0 or 7) or
sun,mon,...,sat.-
user The user to run the command as, or
*for the owner of thecrontabfile.-
command The shell script or command to be run.
For the minute through
day-of week fields, you can use the
following special characters:
-
* (asterisk) All valid values for the field.
-
- (dash) A range of integers, for example,
1-5.-
, (comma) A list of values, for example,
0,2,4.-
/ (forward slash) A step value, for example,
/3in thehourfield means every three hours.
For example, the following entry would run a command every five minutes on weekdays:
0-59/5 * * * 1-5 * commandRun a command at one minute past midnight on the first day of the months April, June, September, and November:
1 0 1 4,6,9,11 * * command
root can add job definition entries to
/etc/crontab, or add
crontab-format files to the
/etc/cron.d directory.
If you add an executable job script to the
/etc/cron.hourly directory,
crond runs the script once every hour. Your
script should check that it is not already running.
For more information, see the crontab(5) manual
page.