Shulou(Shulou.com)06/03 Report--

1. Installation of Crontab

1. Install Crontab under Debian

Apt-get install cron / / Debian is installed in most cases. / etc/init.d/cron restart / / restart Crontab

II. Usage of Crontab

1. View the crontab scheduled execution task list

Crontab-l

2. Add crontab to execute tasks regularly.

Crontab-e

Entering crontab task commands may be different because of the crontab default editor.

As shown in the above figure, the nano editor is relatively easy to use, just enter it in the crontab command format at the end of the file, Ctrl+x exit, and then enter y to save.

The other is the vi editor, first press the I key, enter in the crontab command format at the end of the file, then press the ESC key, and then enter: wq enter.

3. Crontab task command writing format

Format minutehourdayofmonthmonthdayofweek command explain minute hour date monthly payment weekly command range 0-590 "231" 311 "1207" 0 and 7 represent Sunday

We often use the four symbols *,-/ n in crontab. All right, let's draw a table to make it clearer:

The symbolic interpretation * (asterisk) represents all valid values. For example, 023 * backup executes the backup command no matter what day it is, exactly 23:00 on what day it is. , (comma) means to split multiple values For example, the command command is executed at 09:30 on the 1st, 16th and 20th of each month on 309 1, 16 and 20 command. -(minus sign) represents a period of time. For example, 09-17 * checkmail executes the checkmail command / n at 9: 00 to 17:00 every day for a long time every n. For example, * / 5 * check executes the check command every 5 minutes, which is the same as 0-59 check 5.

Here are some examples to deepen our understanding:

Execute the backup program at 3:00 every morning: 0 3 * / root/backup.sh

Execute log cleanup program at 08:30 every Sunday: 308 * * 7 / root/clear.sh

Execute the test program at 50 o'clock every week: 0 0 * * 1 pm 5 test

Execute the wenchuan program at 14:00 on May 12 every year: 0 14 12 5 * / root/wenchuan

Restart php-fpm:*/15 18-23 * / etc/init.d/php-fpm every 15 minutes from 18:00 to 23:00 every night

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