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Translating----geekpi
Linux FAQs with Answers--How to add a cron job on Linux
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> **Question**: I would like to schedule a task on my Linux box, so that the task runs periodically at fixed times. How can I add a cron job for this task on my Linux system?
The cron utility is the default task scheduler used in Linux. Using cron, you can schedule a task (e.g., a command or a shell-script) to run it periodically or one-time at a specific time of hour, day, week, month, etc. The cron tool is useful when you schedule a variety of regular maintenance jobs, such as periodic backup, rotating logs, checking filesystem, monitoring disk space, and so on.
### Add a Cron Job from the Command Line ###
To add a cron job, you can use a command-line tool called crontab.
Type the following command to create a new cron job to run as the current user.
$ crontab -e
If you want a cron job to run as any other user, type the following command instead.
$ sudo crontab -u <username> -e
You will be presented with a text editor window, where you can add or edit cron jobs. By default, nano editor will be used.
![](https://farm9.staticflickr.com/8586/16200331362_1385807ac0_b.jpg)
Each cron job is formatted as follows.
<minute> <hour> <day-of-month> <month-of-year> <day-of-week> <command>
The first five elements specify the schedule for a task, and the last element is the (full-path) command or script to execute according to the schedule.
![](https://farm8.staticflickr.com/7472/16199272841_dffe0b2873_b.jpg)
Here are a few useful cron job examples.
- *** * * * * /home/dan/bin/script.sh**: run every minute.
- **0 * * * * /home/dan/bin/script.sh**: run every hour.
- **0 0 * * * /home/dan/bin/script.sh**: run at 12am daily.
- **0 9,18 * * * /home/dan/bin/script.sh**: run at 9AM and 6PM twice a day.
- **0 9-18 * * * /home/dan/bin/script.sh**: run every hour from 9AM and 6PM.
- **0 9-18 * * 1-5 /home/dan/bin/script.sh**: run every hour from 9AM and 6PM every weekday.
- ***/10 * * * * /home/dan/bin/script.sh**: run every 10 minutes.
Once you are done with setting up cron job(s), press Ctrl+X to save and quit the editor. At this point, newly added cron jobs should be activated.
To browse existing cron jobs of yours, use the following command:
$ crontab -l
### Add a Cron Job from GUI ###
If you are in Linux desktop environment, you can use a GUI fronend for crontab to add or edit a cron job via a more user-friendly interface.
On GNOME desktop, there is GNOME Schedule (gnome-schedule package).
![](https://farm8.staticflickr.com/7484/16015054699_d96f0e9b6a_c.jpg)
On KDE desktop, there is Task Scheduler (kcron package).
![](https://farm8.staticflickr.com/7473/16175298266_825376c901_c.jpg)
--------------------------------------------------------------------------------
via: http://ask.xmodulo.com/add-cron-job-linux.html
译者:[译者ID](https://github.com/译者ID)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出

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Linux 有问必答: 如何在Linux中加入cron任务
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> **提问** 我想在我的Linux中安排一个计划任务该任务在固定时间周期性地运行。我该如何在Linux中添加一个cron任务
cron是Linux中默认的计划任务。使用cron你可以安排一个计划比如命令或者shell脚本周期性地运行或者在指定的小时、天、周、月等特定时间运行。cron在你安排不同的常规维护任务时是很有用的比如周期性地备份、日志循环、检查文件系统、监测磁盘空间等等。
### 从命令行中添加cron任务 ###
要添加cron任务你可以使用称为crontab的命令行工具。
输入下面的命令会创建一个以当前用户运行的新cron任务。
$ crontab -e
如果你想要以其他用户运行cron任务输入下面的命令。
$ sudo crontab -u <username> -e
你将会看见一个文本编辑窗口这里你可以添加或者编辑cron任务。默认使用nono编辑器。
![](https://farm9.staticflickr.com/8586/16200331362_1385807ac0_b.jpg)
每个cron任务的格式如下。
<minute> <hour> <day-of-month> <month-of-year> <day-of-week> <command>
前5个元素定义了任务的计划最后一个元素是命令或者脚本的完整路径。
![](https://farm8.staticflickr.com/7472/16199272841_dffe0b2873_b.jpg)
下面是一些cron任务示例。
- *** * * * * /home/dan/bin/script.sh**: 每分钟运行。
- **0 * * * * /home/dan/bin/script.sh**: 每小时运行。
- **0 0 * * * /home/dan/bin/script.sh**: 每12小时运行。
- **0 9,18 * * * /home/dan/bin/script.sh**: 在每天的9AM和6PM运行。
- **0 9-18 * * * /home/dan/bin/script.sh**: 在9AM到6PM的每个小时运行。
- **0 9-18 * * 1-5 /home/dan/bin/script.sh**: 周一到周五的9AM到6PM每小时运行。
- ***/10 * * * * /home/dan/bin/script.sh**: 每10分钟运行。
一旦完成上面的设置步骤后按下Ctrl+X来保存并退出编辑器。此时新增的计划任务应该已经激活了。
要查看存在的计划任务,使用下面的命令:
$ crontab -l
### 从GUI添加计划任务 ###
如果你在Linux桌面环境中你可以使用crontab的更加友好的GUI前端来添加或者添加一个cron任务。
在Gnome桌面中有一个Gnome Schedulegnome-schedule包
![](https://farm8.staticflickr.com/7484/16015054699_d96f0e9b6a_c.jpg)
在KDE桌面中有一个Task Schedulerkcron包
![](https://farm8.staticflickr.com/7473/16175298266_825376c901_c.jpg)
--------------------------------------------------------------------------------
via: http://ask.xmodulo.com/add-cron-job-linux.html
译者:[geekpi](https://github.com/geekpi)
校对:[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译,[Linux中国](http://linux.cn/) 荣誉推出