Cron Job in linux
Linux/Unix provide the crontab inbuilt utility to schedule any script.
Let’s go through an example and see how crontab would be setup with the help of an example.
Considering we have a java file, and this is wrapped up in a jar file. We are gonna to schedule that jar using crontab.
Create a shell script file(test.sh) with the entry
java -cp .:test.jar Scheduler
test.jar: jar file name
Scheduler: Main class
crontab command is used to edit/list crontab:
How to edit the crontab
To edit a crontab entries, use crontab -e as shown below. By default this will edit the current logged-in users crontab.
How to view the crontab
To view your crontab entries type crontab –l from your linux account as shown below.
Syntax of Crontab:
1 2 3 4 5 /root/test.sh
1: Minute (0-59)
2: Hours (0-23)
3: Day (0-31)
4: Month (1-12)
5: Day of the week(0-6)
/root/test.sh – Script or command name to schedule
Let’s create a crontab. We are gonna to schedule test.sh file that will run daily midnight. Hit the crontab -e to install the crontab and add the entry 1 0 * * * /root/test.sh and save the file.
Now test.sh file will run daily midnight at 00:01AM..
That’t it !!
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