C r O n cron cron reads one or more configuration files containing scheduled tasks. c r o n t a b " " crontab" “Crontab.

Cron service

service crond start		# start service
service crond stop		# service shutdown
service crond restart	# restart service
service crond reload	Reload the configuration
service crond status	Check service status
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The configuration file

/var/spool/cron/	# All user cron tasks
/etc/crontab/		# CrON tasks set by the system administrator
/etc/cron.d/		# Cron script file to execute
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Add the homework

crontab -e
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Crontab The crontab file is automatically created if it does not exist. If you use it for the first time, you are prompted to select the editor and add information about scheduled tasks at the end of the command. Exit and save the configuration. For example:

15 10 * * * your/script/path
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/your/scr I pt/path /your/script/path /your/script/path

Homework format

C ron cron Scheduled task Information about cron jobs has a fixed format:

{minute} {hour} {day-of-month} {month} {day-of-week} {full-path-to-shell-script}
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M I nute minute Minute The value ranges from 0 to 59 0 \sim 59 0 to 59, h O u R hour hour The value ranges from 0 to 23 0 \sim 23 0 to 23, D ay− O f−mont H day-of-month day−of−month Values range from 1 to 31 1 \ SIM 31 1 to 31, M onth month Month Value range: 1 to 12 1 \sim 12 1 to 12, D ay−of−wee K day-of-week day−of−week Ranges from 0 to 7 0\ sim 7 0 to 7. Sunday can be 0 or 7 0\ or 7 0 or 7, F u L L − P a T H − T O − S H E L L − S C r I pt Full-path-to-shell-script Full −path−to−shell−script Indicates the script to be executed.

Check the homework

crontab -l
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The cr O N T ab crontab crontab file is displayed. You can view the job information of all scheduled tasks.

Delete operation

crontab -r
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You can delete the cro N T ab crontab crontab file. After the crontab file is deleted, all scheduled tasks are deleted. If you want to delete certain scheduled tasks, You can select − E-E − E to edit c R O N T ab crontab To delete tasks from the crontab file.

crontab -lr
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Delete the cro N T ab crontab crontab file and remind the user.

The sample

Execution per minute

* * * * * script
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Every hour 15, 15, 15 minutes and 45, 45, 45 minutes

15, 45 * * * * script
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Every day from 8 to 11 8 \ SIM 11, 15, 15 and 45, 45 minutes

15, 45 8-11 * * * script
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Every other day at 8:15 a.m. 8:15 a.m. 8:15 a.m

15 8 */2 * * script
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Every Monday morning at 10:15 10:15 10:15

15 10 * * 1 script
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It is executed at 10:15 10:15 on the 11th day of each month

15 10 1 * * script
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