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 command
where 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 thecrontab
file.-
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,
/3
in thehour
field means every three hours.
For example, the following entry would run a command every five minutes on weekdays:
0-59/5 * * * 1-5 * command
Run 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.