Linux's Scheduled Tasks

1 at: One-time task configuration, its tasks can only be performed at the specified times, provided that the ATD service is turned on.

[Email protected] ~]# at 17:45 2017-05-30 #设置任务

at> ls/> A.txt

At> <EOT>

Job 3 at 2017-05-30 17:45

[Email protected] ~]# ATQ #查看一次性任务

32017-05-30 17:45 a root

[Email protected] ~]# ATRM 3 #删除任务

2 crontab: Periodic task configuration, which greatly reduces the operation of repetitive system management tasks. The corresponding system service is crond.

2.1 crontab Configuration files and directories

/etc/crontab--System task profile, system installation automatically set, not recommended modification. The shell environment, executable path, and other variable operations are set in the file.

The configuration file for the/var/spool/cron/--user scheduled task is stored in the directory with the same file name as the user.

[Email protected] cron]# ls-l/var/spool/cron/*

-RW-------. 1 root root Apr 17:28/var/spool/cron/zwj

2.2 Creating and managing scheduled Tasks using Crontab

Options:-e Edit Scheduled Task list

-u specifies which user the task plan belongs to, usually the root user to edit, delete other users ' scheduled tasks

-L Display Scheduled Tasks list

-R Delete Scheduled Task list

[Email protected] cron]# crontab-e-u zwj #为用户zwj建立任务计划

*/2 * * * */bin/ls/>/home/zwj/a.txt

[Email protected] cron]# crontab-l-u zwj #查看用户zwj的任务计划

[Email protected] cron]# crontab-l #查看当前用户的任务计划

No crontab for Root

[Email protected] cron]# crontab-r #清除当前用户的所有计划任务

[[email protected] cron]# crontab-l-U zwj #清除zwj的计划任务, root access required

Attached: example of the format of a scheduled task

Basic format:
* * * * * command
Time-sharing Weekly command

-: Indicates a continuous time range, such as "1-4", indicating 1,2,3,4

,: Indicates a discontinuous range, such as "1,5,8"

/: Represents the interval frequency, such as "*/3" in the date segment, that represents every 3 days.

7 * * */sbin/service sshd start #每天7:30 Start sshd Service

0 0 */5 * */bin/rm-rf/var/ftp/pub/* #每隔5天清空ftp公共目录

0 1 5,15 * */sbin/service httpd restart #每月5号和15号1点重启httpd服务

0 1 5-15 * */bin/rm-rf/var/ftp/pub/* #每月5到15号1点清空ftp公共目录

0 1 * * 6,7/script/a.sh #每周六, Day 1 o'clock in the morning execute script

0 1-7/1 * * */script/a.sh #每天1点到7点之间, scripts executed every 1 hours

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Linux's Scheduled Tasks