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\___/|_| |_|\__,_/___\___/ \__|
crontab —
config and usage
This applies to the user crontab, the system crontab is
/etc/crontab.
MINUTE HOUR DAY_OF_MONTH MONTH
DAY_OF_WEEK COMMAND
The fields MINUTE, HOUR, DAY, MONTH, DAY_OF_WEEK can have the
following values:
| - Numeric: MINUTE (0-60), HOUR (0-23), DAY_OF_MONTh (1-31), MONTH
(1-12), DAY_OF_WEEK (0-6).
The week starts on Sunday with the value 0.
|
| - Asterisk: * means it executes every MINUTE, HOUR, DAY, MONTH,
DAY_OF_WEEK depending on the field where it is set. |
| - Text: The first 3 letters of the name of the month or day of the week.
It is case-insensitive. MONTH (Jan-Dec), DAY_OF_WEEK (Sun-Sat). |
| - Ranges: Example, using 15-30 for MINUTE will run every minute between
the minutes 15 and 30. |
| - Lists: Values can be separated by comma, example: DAY_OF_WEEK Mon,Wed
to run on Mondays and Wednesdays. |
| - Frequency: specified as /NUMBER, example: */10 will run every 10
minutes. |
| - The options can be combined, example: MINUTE 15-30/5,45 will run every
5 minutes between the minutes 15 and 30 and will also run at minute
45. |
| - The command can be a command or command chain. |
15 5-10 * * 1 5 date >
log
This will output date to the file log Monday through Friday 15
minutes after the hour between 5am and 10am any day of the month all
months.
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To ensure crontab can execute the command, use the full path of
the command, which can be found using the command
whereis, and full path for files and
directories.
$ whereis date
| OpenBSD output |
: /bin/date |
| linux output |
: date: /usr/bin/date /bin/date
/usr/man/man1/date.1.gz |
15 5-10 * * 1 5 /usr/bin/date >
/home/user/log
Some environment variables may not be found, environment variables
can be set at the beginning of the crontab file. Example:
HOME=/home/user
15 5-10 * * 1 5 /usr/bin/date > ${HOME}/log