Linux commands: Task Scheduler crontab Anacrontab at cron

Task Schedule:

1. Perform one task at a time in the future: at Batch

Format: At time at-l View Schedule list

At> COMMAND

At> Ctrl+d

Specify time:

Absolute time: hh:mm DD. Mm. YY Mm/dd/yy

Relative Time: now+#

Unit: Minutes,hours,days,weeks

Blur Time: Noon,midnight,teatime

The execution result of the command is sent to the user who scheduled the task as a message

At-l View non-executed scheduled Tasks at-l=atq

At-d job_id Canceling an unscheduled scheduled task at-d scheduled task ID number

At blacklist and whitelist files/etc/at.deny/etc/at.allow

[Email protected] ~]# at-l

[Email protected] ~]# at-l

32016-12-17 08:36 a root

22016-12-17 08:28 a root

[Email protected] ~]# at-d 2

[Email protected] ~]# at-l

32016-12-17 08:36 a root number 2 task schedule canceled

Usage:

[[email protected] ~]# at now+3minutes 3 minutes after execution

At> Ls/var need to execute Ls/var command

At> Cat/etc/fstab need to execute Cat/etc/fstab command

at> <EOT> Complete Task plan by ctrl+d

Job 1 at 2016-12-17 08:16

[Email protected] ~]#

2. Perform a task periodically: the results of the execution will be sent to the administrator in the form of mail

Cron: Self is a service that runs uninterrupted

Anacron:cron, can be implemented to enable cron for various reasons in the past time the execution of the task did not perform the normal execution once;

cron configuration file:/etc/crontab

[Email protected] ~]# Cat/etc/crontab

Shell=/bin/bash #定义执行脚本的shell为/bin/bash

Path=/sbin:/bin:/usr/sbin:/usr/bin #定义脚本执行的环境变量位置

Mailto=root #执行结果发送给root用户

home=/ #家目录

# Run-parts: indicates that all command scripts are executed in the order of the directory or document

* * * * * Root run-parts/etc/cron.hourly the first minute of every hour

4 * * * Root run-parts/etc/cron.daily daily 4:02

4 * * 0 root run-parts/etc/cron.weekly every Sunday 4:22

4 1 * * Root run-parts/etc/cron.monthly monthly 1st 4:42

Cron:

System Cron Task:

Configuration file/etc/crontab

Format: minutes, hours, days, months, weeks, user tasks

User Cron Task:

Configuration file/var/spool/cron/username

Format: Minutes Hours day Month Week task

Valid values for TIME:

Minutes: 0-59 Hours: 0-23 days: January-3 January: 1-12 weeks: 0-7,0 and 7 denote Sunday

Time-Pass representation:

*: All valid values corresponding to

3 * * *: 3rd minutes per hour

3 * * 7: Every Sunday hour of the 3rd minute

13 12 * *: 12 points per day, 13 minutes

,: Discrete point in time:

10,40 02 * * 2,5: Every Tuesday, Friday 2:10 and 2:40

-: Continuous point in time:

10 02 * 1-5: Every Monday to Friday 2:10

/#: Each time within the corresponding range of values must be fixed at a point in time that is smaller than each unit

*/3 * * * *: every 3 minutes

10 */2 * *: executed every 2 hours

10 06 */2 * *: Executed every 2 days

CRON environment variable: Cron executes all commands to go down the path specified by the PATH environment variable

3, the user task management:

Crontab to crontab execution, the Crond service must be running,

View the running Status service Cront status

[[Email protected] ~]# service Crond status

Crond (PID 3733) is running ...

-L: Lists all cron tasks for the current user

-e: Edit the cron task, press A to enter, press ESC and enter: Wq Save to exit.

[[email protected] ~]# crontab-e First enter crontab-e and press A to edit,

After editing, press ESC and enter: Wq Save to exit.

*/3 * * * */bin/echo "How is it?"

-r: Delete all cron tasks and remove only one of the scheduled tasks, just crontab-e edit to delete the tasks

-u:username managing Cront tasks for their users

Anacrontab:/etc/anacrontab

This article is from the "Learn Linux history" blog, please be sure to keep this source http://woyaoxuelinux.blog.51cto.com/5663865/1883578

Linux commands: Task Scheduler crontab Anacrontab at cron