Linux Recurring Task plan detailed

Linux Recurring Task plan detailed

One-time task execution:

At,batch At Interactive: Let the user enter more than one command to execute at the at> prompt; Batch processing: Writes the command of the task to the file by the at to call; Use format : At time At > CTRL+D: Submitting a task

At jobs have queues : represented by a single letter

View Job : At-l =atq

[[email protected] ~]# at 10:46at> ls-ld/etcat> <eot>job 1 at 2015-08-25 10:46[[email protected] ~]# at-l12 015-08-25 10:46 a root

Delete a job that has not been executed :

At-d Job_num ATRM Job_num

[[email protected] ~]# at-l22015-08-25 10:55 a root[[email protected] ~]# at-d 2

At batch mode :

At-f/path/to/at_job_file Time

[[email protected] ~]# at-f at.txt 10:55job 2 at 2015-08-25 10:55

Time: Blur Times

Now,noon,midnight,teatime,tomoroow

[Email protected] ~]# at now+5minat> ls-l/tmpat> cat/etc/issueat> <eot>job 4 at 2015-08-25 11:00

Note: The execution results of a task plan are sent to the task submitter by mail!!!

Recurring Task Scheduler: Cron

Crond: Daemon

Service process: Blocking, polling

System cron:

Files:/etc/crontab In a system cron, any command that is to be executed periodically will not be kept consistent with the variables of any user's path, but defined by its own environment variable;

User cron:

/var/spoo;/cron/username

Etc/crontab files: Define a separate task for each row

[[Email protected] ~]# cat /etc/crontab shell=/bin/bashpath=/sbin:/bin:/usr/sbin:/usr /binmailto=roothome=/# for details see man 4 crontabs# example of  job definition:  define job # .---------------- minute  (0 - 59)   minutes #  | &NBSP:------------- hour  (0 - 23)   hours # |  |  .- --------- day of month  (1 - 31)   days # |  |  |  &NBSP:------- month  (1 - 12)  OR jan,feb,mar,apr ...  month # |   |  |  | &NBSP---- day of week  (0 - 6) (sunday=0  OR 7) or sun,mon,tue,wed,thu,fri,sat  Week # |  |  |  |   |# *  *  *  *  * user-name command to  be executed

Time notation: 1. Each time bit should use the value within the range of valid values for which it is available 2. * On a time bit indicates all valid values for the corresponding bit 3,-: consecutive time adjacent points to take the value of 1-5 4., discrete time point value 1, 5 5,/#: For the specified time range of every # once 5-45/3 * * * * 0/2 * * */bin/echo "Hello" &>/dev/null executed every 2 hours

Note: Reject messages with output redirection:

&>/dev/null >/dev/null 2>&1

User cron: Use the crontab command to implement

-l: View your cron task List -E: Open your own cron profile with the editor defined in the editor variable -r: Remove crontab file -u UserName: Configure crontab jobs for other users reminder: If you use% in crontab user commands, you have to escape to \%     5 3 * * */bin/touch ~/testfile_ ' date +\%y-\%m-\%d '. txt After using single quotes,% can also not escape     5 3 * * */bin/touch ~/testfile_ ' date + ' \%y-\%m-\%d ' . txt

[[email protected] ~]$ Crontab-lno crontab for Docker[email protected] ~]$ Crontab-eno crontab for docker-using an EMP Ty ONE*/3 * * * */bin/echo "How is it?" [Email protected] ~]# Ls/var/spool/cron/docker

Crontab file Format:

Blank rows are ignored #开头行是注释

How to implement a second-level task:

* * * * * for i in {}n/echo

How to implement a second-level task:

* * * * for i in {0..4};d O/bin/echo "How is it?"; Sleep10;done

Anacron: is a supplement to crontab that checks whether a task in crontab has not been executed in the past period, If it is not executed, it is executed at some point after the boot, regardless of whether the cycle arrives.

This article is from the "Ling" blog, make sure to keep this source http://19871018.blog.51cto.com/3485797/1689885

Linux Recurring Task plan detailed