The usage of crontab Command to deal with scheduled tasks in Linux system

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Execute the operation command regularly, each user has its own crontab, and the configuration file is stored under / var and cannot be edited directly.

-e set timer

-l lists the settings for the current timer

-r delete timer settings

-I interactive mode, ask first when deleting timer settings

Column 1 column 2 3 4 5 6

Column 1 represents minutes 1: 59 per minute is represented by * or * / 1.

The second column represents the hour 1: 23 (0 means 0 o'clock)

The third column represents the date 1: 31

The fourth column represents the month from January to December.

The fifth column identification number is 0006 (0 means Sunday)

Column 6 commands to run

There are many examples of crontab writing rules, the following from the Internet, lazy, heh heh

30 21 * / usr/local/etc/rc.d/lighttpd restart

The above example shows that lighttpd is restarted at 21:30 every night.

45-4-1-10-10-22 * / usr/local/etc/rc.d/lighttpd restart

The above example shows that lighttpd is restarted at 4: 45 on the 1st, 10th, and 22nd of each month.

10 1 * * 6 0 / usr/local/etc/rc.d/lighttpd restart

The above example shows that lighttpd is restarted at 1: 10 every Saturday and Sunday.

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

The above example shows that lighttpd is restarted every 30 minutes between 18: 00 and 23: 00 every day.

0 23 * * 6 / usr/local/etc/rc.d/lighttpd restart

The above example shows that lighttpd is restarted at 11: 00 pm every Saturday.

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

Restart lighttpd every hour

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

Restart lighttpd every other hour between 11:00 and 7 a.m.

0 11 4 * mon-wed / usr/local/etc/rc.d/lighttpd restart

Restart lighttpd on the 4th of each month and 11:00 from Monday to Wednesday

0 4 1 jan * / usr/local/etc/rc.d/lighttpd restart

Restart lighttpd at 4: 00 on January 1st

Special symbol

Symbolic meaning

* indicates that any time is fine

-indicates the range of values

For example:

00 17-19 * means 17 18 19 all perform tasks, indicating separation time.

For example

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

Example 1

The code is as follows:

[root@localhost ~] # crontab-l # View programs that run regularly

59 23 * / bin/sh / var/www/database/bak.sh

59 3 * / bin/sh / var/www/database/mylinux.sh

59 5 * 0 / sbin/reboot

The code is as follows:

[root@localhost ~] # crontab-e # add, edit

Example 2

Set the crontab to execute regularly every minute, and so on. Today, I posted it for everyone to use. Students who will be able to do so will float by.

Execute * / 5 * every five minutes

Execute 0 * per hour

Perform 0 0 * every day

Execute 0 0 * 0 every week

Execute 0 01 * * every month

0 0 1 1 * per year

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