Linux常用命令笔记---计划任务

 [root@szm logrotate.d]# at -h

Usage: at [-V] [-q x] [-f file] [-mldbv] time

       at -c job ...

       atq [-V] [-q x]

       atrm [-V] job ...

       batch

-m：完成计划任务之后以邮件方式告之任务执行的结果 -f：从文件中读取计划任务代替从标准输入录入计划任务 -l：查看计划任务，与atq命令功能相同 -d：删除一个指定的计划任务，与atrm命令功能相同 -c：显示计划任务的执行命令 -t：时间执行 Ctrl+D退出编辑

 

[root@szm logrotate.d]# at now+5min

at> ls .

at> <EOT> 

job 3 at 2013-03-13 14:46

[root@szm logrotate.d]# atq

3 2013-03-13 14:46 a root

[root@szm logrotate.d]# at -c 3

 

无法修改at计划任务，只能删除后重写

 

[root@szm logrotate.d]# at -d 3

[root@szm logrotate.d]# atrm 4

 

batch与at不同的是,batch命令控制的调试工作会在cpu的工作负载小于0.8的时候执行用户创建的计划任务。

 

at命令的控制： 1.[root@szm logrotate.d]# cat /etc/at.deny  2.[root@szm logrotate.d]# cat /etc/at.allow 如果两个文件都有用户，以allow为准，如果没有这两个文件，只能root使用at

[root@szm logrotate.d]# echo "szm" >> /etc/at.deny 

[szm@szm Desktop]$ at now+5

You do not have permission to use at.

 

[root@szm logrotate.d]# touch /etc/at.allow

[root@szm logrotate.d]# echo "szm" >> /etc/at.allow

 

[szm@szm Desktop]$ at now+5 min

at> ls

at> <EOT>

job 4 at 2013-03-13 15:02

 

重复执行的计划任务：crontab

 

[root@szm logrotate.d]# crontab --help

crontab: invalid option -- '-'

crontab: usage error: unrecognized option

usage: crontab [-u user] file

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

(default operation is replace, per 1003.2)

-e (edit user's crontab)

-l (list user's crontab)

-r (delete user's crontab)

-i (prompt before deleting user's crontab)

-s (selinux context)

 

保存位置：[root@szm logrotate.d]# cat /var/spool/cron/

 

minute hour day of mounth month day of week ----------- * , - /n

[root@szm logrotate.d]# crontab -e

no crontab for root - using an empty one

crontab: installing new crontab

[root@szm logrotate.d]# crontab -l

* */5 * * * /bin/cp /etc/passwd /tmp/passwd

[root@szm logrotate.d]# cat /var/spool/cron/root 

* */5 * * * /bin/cp /etc/passwd /tmp/passwd

[root@szm logrotate.d]# crontab -r

[root@szm logrotate.d]# crontab -l

no crontab for root

[root@szm logrotate.d]# cat /etc/crontab 

SHELL=/bin/bash

PATH=/sbin:/bin:/usr/sbin:/usr/bin

MAILTO=root

HOME=/

 

# For details see man 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

 

计划任务管理机制：anacron

 

crontab管理错过时使用anacron

 

[root@szm logrotate.d]# cat /etc/anacrontab 

# /etc/anacrontab: configuration file for anacron

 

# See anacron(8) and anacrontab(5) for details.

 

SHELL=/bin/sh

PATH=/sbin:/bin:/usr/sbin:/usr/bin

MAILTO=root

# the maximal random delay added to the base delay of the jobs

RANDOM_DELAY=45

# the jobs will be started during the following hours only

START_HOURS_RANGE=3-22

 

#period in days   delay in minutes   job-identifier   command

1 5 cron.daily nice run-parts /etc/cron.daily

7 25 cron.weekly nice run-parts /etc/cron.weekly

@monthly 45 cron.monthly nice run-parts /etc/cron.monthly

 

[root@szm logrotate.d]# ll /etc/cron*/*ana*

-rwxr-xr-x. 1 root root 424 Jul 19  2011 /etc/cron.hourly/0anacron

 

[root@szm logrotate.d]# cat /etc/cron.hourly/0anacron 

#!/bin/bash

#in case file doesn't exist 

if test -r /var/spool/anacron/cron.daily; then

    day=`cat /var/spool/anacron/cron.daily`

fi

if [ `date +%Y%m%d` = "$day" ]; then

    exit 0;

fi

 

# in case anacron is already running,

# there will be log (daemon won't be running twice).

if test -x /usr/bin/on_ac_power; then

    /usr/bin/on_ac_power &> /dev/null

    if test $? -eq 1; then

    exit 0

    fi

fi

/usr/sbin/anacron -s