Linux crontab Task Scheduler

I. Description of CRONTAB

Linux crontab task scheduling is to perform the corresponding tasks within the specified time frequency.

Ii. details of crontab documents

1. crontab files in Linux/etc/crontab

2. View crontab File # Vi/etc/crontab file description below

Shell=/bin/bash
Path=/sbin:/bin:/usr/sbin:/usr/bin
Mailto=root
home=/

# for details see Mans 4 Crontabs

# Example of Job definition:
#.----------------Minute (0-59)
# | .-------------Hour (0-23)
# |  | .----------Day of Month (1-31)
# |  |  | .-------month (1-12) OR jan,feb,mar,apr ...
# |  |  |  | .----Day of Week (0-6) (sunday=0 or 7) or Sun,mon,tue,wed,thu,fri,sat
# |  |  |  | |
# * * * * * * user-name command to be executed

Iii. crontab Command Description

crontab [-u username] [-l|-e|-r]

Parameters:

-U: Only root can do this task, that is, to help other users new/delete crontab work schedule;

-e: Edit Crontab's work;

-L: Consult Crontab's work content;

-R: Delete all the work of crontab, if you want to delete only one item, please use-e to edit.

Special characters	Representative meaning
* (asterisk)	Mean to accept at any moment. For example, the day, month, and week of an example are *, which means that the follow-up order is executed 12:00 on the day of the week, regardless of the month.
, (comma)	Represents the meaning of the separation period. For example, if the work to be performed is 3:00 and 6:00, it will be: 0 3,6 * * command The time is still five columns, but the second column is 3,6, representing 3 and 6.
-(minus)	Represents a period of time, for example, between 8 and 12 hours of 20 points per hour of work: 8-12 * * * command Look carefully at the second column to become 8-12. The meaning of representing 8,9,10,11,12
/n (Slash)	n represents a number, which is the meaning of every n unit interval, for example, every five minutes: */5 * * * command with * and/5来, can also be written in 0-59/5, the same meaning

Iv. examples

CRONTAB-E; Open the current user schedule edit

* * */sbin/service httpd Restart * * *   /sbin/service sshd Start * * *   /sbin/service sshd Stop   * * Fsck/home * * * *   /home/bruce/backup   ; # every Monday to Friday 3 o'clock, in the directory/home, look for files with the file name *.xxx and delete the files 4 days ago.  #每月的1, 11, 21, 31st Yes 6:30 execute the LS command once

Finally, thank the following two bloggers for sharing

Linux task Scheduling operating mechanism reference http://blog.csdn.net/zhongbeida_xue/article/details/51280292

Linux task scheduling operation reference Http://www.cnblogs.com/mingforyou/p/3930636.html

Linux crontab Task Scheduler