Wednesday, June 21, 2006
Cron job - quick & dirty
Here's how you set up a cron job on a linux machine:
That's of course, the quick & dirty way to get you going. If you need more information, just do man crontab or google it!
- Write the shell script you want to execute wherever you want. Say, /tmp/myCron.sh
- Try executing this script manually from the console. Make sure it does what you need.
-
>sudo vi /etc/crontab
Here I'm assuming that you have root access using sudo and you know that you ought to be careful with sudo etc. - Now in this file, you will see something like this:
47 1 * * * root run-parts /etc/cron.daily
This means : Run all scripts under the directory /etc/cron.daily every day at 01:47 (AM). See what your crontab file is set up to do. Here is the generic description of the format:
00,30 12,13,14 1 4 3 <user> run-parts <dir>00,30 This is where you specify the minutes (0-59) We have
chosen both :00 and :30 (right on the hour and
half hour)12,13,14 These are the hours, it is in military time so 0-23
(this example equals to 12pm, 1pm, and 2pm)1 The day of the month (1-31) This is of course the first
day of the month.4 This is the month (1-12) April in this case 3 This is the day of the week (0-6 with 0 being Sunday)
Wednesday is being used in example.<user> Run the cron job as this user <dir> Run the cron job parts (scripts) from this dir - Based on the contents of your crontab file, copy your script in the right place. In my case it would be:
>sudo cp /tmp/myCron.sh /etc/cron.daily/ - Make sure the script is executable.
>sudo chmod +x /etc/cron.daily/myCron.sh - That's it! Now to test your cron job, look at the system date as:
>date
Wed Jun 21 03:34:00 PDT 2006
Assuming you got the above output for the system date, you can schedule the cron job (cron.daily) to run at the next minute as:34 3 * * * root run-parts /etc/cron.daily
That's of course, the quick & dirty way to get you going. If you need more information, just do man crontab or google it!
