How to setup cron jobs in Ubuntu
Cron is a time-based job scheduler in Unix-like operating systems. Cron helps to run commands or scripts at a given time and date. After setup cron it will execute periodically.
Install the cron package on Ubuntu:
apt-get install cron
Check cron status:
systemctl status cron
* * * * * command
In the syntax first * stand for representing minutes [0-59]. Second * stands for representing hour[0-23]. Third * stand for representing day [0-31]. Fourth star stands for representing month[0-12]. Fifth * stand for representing day of the week[0-7].
Here are some more examples of how to use cron’s scheduling component:
* * * * *- Run the command every minute.
15 * * * *- Run the command 15 minutes after every hour.
0,10,20,30 * * * *- Run the command every 10 minutes.
*/15 * * * *- Run the command every 15 minutes.
0 4 * * *- Run the command every day at 4:00 AM.
0 4 * * 2-4- Run the command every Tuesday, Wednesday, and Thursday at 4:00 AM.
20,40 */8 * 7-12 *- Run the command on the 20th and 40th minute of every 8th hour every day of the last 6 months of the year.
Example1:If we want to schedule on first day of each month at 11
0 11 1 * * /path/script.sh
Example2: Set up and run php script every day at
0 11 * * * /path/script.php
Example3: Set up and call url every day at
0 11 * * * curl http://www.google.com
Following options are available in crontab:
crontab -l : List the all your cron jobs.
crontab -r : Delete the current cron jobs.