Linux under Crontab detailed

Overview

Task scheduling: Refers to a particular command or program that the system executes at a certain time

Task Scheduling Classification:

-System work: Some important work must be performed periodically, such as virus scanning, etc.

-Individual users work: Individual users may want to perform certain programs

Task Dispatch commands

Set Task Scheduler file:/etc/crontab

Set up personal Task Scheduler, execute crontab ‐e Command, then enter task to dispatch file

"Case"5 * * * * ls ‐l/etc/>/tmp/to.txt, meaning to say five minutes per hour to execute the ls command

Rules for scheduling files

Field name	Description	Range
Minutes	The number of minutes per hour to execute	0-59
Hours	The first hours of the day are executed	0-23
Date	Day of the Month execution	1-31
Calendar	The month ordinal of the year is executed	1-12
Week	Day of the Week execution	0-6

Using Task scheduling

-Set Tasks

-Crontab‐e

-Perform date >/home/mydate2 at certain intervals

-Want to go to the day of the morning 2:xx to perform date >>/home/mydate2, you can crontab ‐e added:0 2 * * * Date >>/home/mydate2

-Wish to execute every minute: Add in crontab ‐e :* * * * *date >>/home/mydate2

-How to schedule multiple tasks

- write multiple commands directly in Crontab ‐e (not recommended)

-Can put all tasks, write to an executable file (Shell programming)

-Terminate task scheduling

-Crontab‐r: Terminating task scheduling

-Crontab‐l: Lists which tasks are currently scheduled

Linux under Crontab detailed