How to use crontab

This is a short snippet about how to use the UNIX program Crontab.

Recently, I was told to write a script to download some IGU data from a certain FTP server. Advisor hopes to keep the script a regular work on the server, which means to make the script automatically executes it everyday. I thought there may be a lot work to do, but then I found crontab. It’s easy to use it, here is a simple introduction.

Any user can set up their own crontab task on the machine, here, a task can be a script or a program. Two main usage:

• crontab -l to see the current list of tasks.
• crontab -e will open the default editor to edit the list.

The rule of the list can be described as below:
minute(s) hour(s) day(s) month(s) weekday(s) command(s)

Descriptions of these fields can be found HERE.