Running Linux Cron Jobs Every 30 Seconds

Cron is an incredibly useful tool in the Linux operating system. It allows users to schedule tasks, also known as jobs, to run automatically at specific times or dates. While it is designed to schedule tasks to run at least once per minute, there are techniques you can use to run tasks every 30 seconds. This article provides a deep dive into understanding how to manipulate cron jobs in such a way to run tasks on a more frequent schedule.

What is a Cron Job?

The term “cron” comes from the Greek word “Chronos”, which means time. In Linux, cron is a time-based job scheduler that enables users to schedule jobs (commands or scripts) to run periodically at fixed times, dates, or intervals.

How to Run Cron Jobs Every 30 Seconds?

Cron is designed to wake up every minute and check for tasks to execute. Therefore, by default, it does not support scheduling tasks every 30 seconds. However, there is a workaround to this limitation.

To schedule a task to run every 30 seconds, you will need to create two cron jobs that run every minute, but the second job will have a 30-second delay.

Here’s how you can accomplish this:

1. Open the crontab file:

   crontab -e 
   

2. In the crontab file, add the following lines:
   * * * * * /path/to/your/script.sh * * * * * (sleep 30; /path/to/your/script.sh)

   1 2	* * * * * /path/to/your/script.sh * * * * * (sleep 30; /path/to/your/script.sh)

   The first line means that the script is run every minute, while the second line also schedules the script to run every minute, but with a 30-second sleep before it runs. As a result, the script will execute every 30 seconds.

   Please replace `/path/to/your/script.sh` with the actual path to your script.

Conclusion

While the Linux cron utility doesn’t natively support scheduling tasks every 30 seconds, by using a creative workaround, it’s entirely possible. The ability to automate tasks with such frequency can be powerful in the right situations, but it should be used with care to avoid putting too much load on your system. Remember, understanding the tools at your disposal is the first step towards optimizing your processes and making the most of your Linux system.