Linux下使用crontab创建定时任务

1. 安装
2. 添加定时任务
3. 查看已创建的任务

安装

apt-get install cron

cron包括两部分，其中crond是一个守护进程，负责周期性的执行用户指定的任务。而crontab是一个用户级别的工具，用户可以通过crontab来编写各种任务

添加定时任务

进入编辑界面：crontab -e

定时任务格式：m h dom mon dow command

• m 分钟 0-59
• h 小时 0-23
• dom 天 1-31
• mon 月 1-12
• dow 周 0-6（0是周日）
• command 命令

示例：

* * * * * date >> time.log  # 每分钟记录时间
*/2 * * * * date >> time.log  # 每隔2分钟记录时间
5 * * * * date >> time.log  # 每小时的第5分钟
5,7 * * * * date >> time.log  # 每小时的第5和7分钟

查看已创建的任务

$ crontab -l
# Edit this file to introduce tasks to be run by cron.
# 
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# 
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').# 
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# 
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 
# For more information see the manual pages of crontab(5) and cron(8)
# 
# m h  dom mon dow   command
10 0 * * * sh -c "a.sh"
10 0 * * * sh -c "b.sh"