Detailed explanation of the usage of the CRONTAB command processing timing task in Linux system

Execute the Operation command regularly, each user has own crontab, the configuration file exists under/var, cannot be edited directly.

-E Set Timer

-l lists the current timer settings

-R Delete Timer settings

-I interactive mode, to remove the timer settings to first ask

1th column 2nd Column 3 4 5 6

The 1th column represents minutes 1~59 per minute with * or */1

The 2nd column represents the hour 1~23 (0 for 0 points)

The 3rd column represents the date 1~31

The 4th column represents the month 1~12

The 5th list of the week 0~6 (0 for Sunday)

6th column the command to run

Crontab a lot of examples of writing rules, the following from the Internet to find, lazy, hey

* * * */usr/local/etc/rc.d/lighttpd restart

The above example shows a 21:30 reboot lighttpd per night.

4 1,10,22 * */USR/LOCAL/ETC/RC.D/LIGHTTPD restart

The above example represents the 4:45 restart LIGHTTPD for 1, 10, and 22nd of each month.

1 * * 6,0/USR/LOCAL/ETC/RC.D/LIGHTTPD restart

The above example shows the 1:10 restart lighttpd every Saturday and Sunday.

0,30 18-23 * * * */usr/local/etc/rc.d/lighttpd restart

The example above indicates that the LIGHTTPD is restarted every 30 minutes from 18:00 to 23:00 every day.

0 * * 6/USR/LOCAL/ETC/RC.D/LIGHTTPD restart

The above example indicates that the 11:00 PM restarts lighttpd every Saturday.

0 * * * */usr/local/etc/rc.d/lighttpd restart

Restart lighttpd every hour.

* 23-7/1 * * * */usr/local/etc/rc.d/lighttpd restart

Between 11 o'clock and 7 in the morning, restart lighttpd every hour.

0 4 * mon-wed/usr/local/etc/rc.d/lighttpd restart

4th per month with 11 points per Monday to Wednesday restart LIGHTTPD

0 4 1/USR/LOCAL/ETC/RC.D/LIGHTTPD * Restart

Restart lighttpd at 4 o ' January 1.

Special symbols

Symbolic meaning

* Indicates any time can be

-Represents a range of values

For example:

00 17-19 * * * means 17 18 19 performs the task, indicating the separation time.

For example

30 17,18,19 * * * means 17.30 18.30 19.30 Execution/n represents the number, indicating how often it is executed

Example 1

The code is as follows:

[Root@localhost ~]# crontab-l #查看定时运行的程序

* * */bin/sh/var/www/database/bak.sh

3 * * */bin/sh/var/www/database/mylinux.sh

5 * * 0/sbin/reboot

The code is as follows:

[Root@localhost ~]# crontab-e #添加, edit

Example 2

Set crontab every minute to execute the problem, today I posted up to facilitate the use of everyone, the students will drift over it

Execute */5 * * * * every five minutes

0 per hour * * * * * *

Daily Execution 0 0 * * *

Perform 0 0 * * 0 per week

0 0 1 * * * per month

Annual Implementation 0 0 1 1 *