Linux crontab Format detailed description

Crontab is a service that most Linux distributions bring with them a timed execution program. The CRONTAB-E command enables you to open a text editor to edit a timed task for the current user.

The specific format is as follows:

Name: crontab

Use Rights: All users

How to use:

crontab file [-u user]-replaces the current crontab with the specified files.

Crontab-[-u user]-replaces the current crontab with standard input.

crontab-1[user]-lists the user's current crontab.

crontab-e[user]-Edit user's current crontab.

crontab-d[user]-deletes the user's current crontab.

Crontab-c dir-Specifies the directory for crontab.

crontab file format: M H d M D cmd.

1 One task per line

2 Categorize 6 columns per task, with space or tab spacing between each column

3 The first 5 columns represent a timed cycle, and the last column represents the program

The order of the first 5 columns in 4 is: time-sharing and Lunar Week

5 means to write a specific time only at some time, and each cycle is performed with a * representative

Give a few concrete examples:

1 * * * * command (1 minutes per hour to execute orders, such as: 0 points 1 points, 1 point 1 points ...) ）
* * * * Command (executed every minute, 1440 times a day)
0 0 1 * * Command (1th # 0:0 per month)

* * * */usr/local/etc/rc.d/lighttpd restart
The above example represents 21:30 restart Apache per night.

4 1,10,22 * */USR/LOCAL/ETC/RC.D/LIGHTTPD restart
The above example represents the 4:45 reboot of Apache for 1, 10, and 22nd per month.

1 * * 6,0/USR/LOCAL/ETC/RC.D/LIGHTTPD restart
The above example shows the 1:10 reboot of Apache every Saturday and Sunday.

0,30 18-23 * * * */usr/local/etc/rc.d/lighttpd restart
The example above shows that Apache 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 11:00 PM restarts Apache every Saturday.

* */1 * * * */usr/local/etc/rc.d/lighttpd restart
Restart Apache every hour

* 23-7/1 * * * */usr/local/etc/rc.d/lighttpd restart
From 11 o'clock to 7 in the morning, restart Apache every hour.

0 4 * mon-wed/usr/local/etc/rc.d/lighttpd restart
4th per month with 11 points per Monday to Wednesday restart Apache

0 4 1/USR/LOCAL/ETC/RC.D/LIGHTTPD * Restart
Restart Apache at 4 o ' January 1.