A common issue in projects regarding data acquisition or frequently run scripts is the need to automate these processes. There area various methods to achieving this. The most common one is crontab. As an alternative, Windows users can utilize Windows Task Scheduler which is a desktop application for running specific executables after a predefined trigger.

For example purposes, let’s consider a bash script my_scipt.sh located in the user directory.

crontab

crontab (short for “cron table”), is a time-based job scheduler in Unix-like operating systems. It allows users to schedule jobs (commands or scripts) to run periodically at fixed times, dates, or intervals.

Creating a Cron Job

To schedule a task using crontab, begin by creating a file in a location of your choice, under any name you prefer. Now, you can add entries for each job you want to schedule. A crontab file entry looks like this:

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* * * * * ~/my_script.sh

where each asterisk position corresponds to subsequentially:

  • minutes
  • hours
  • days of the month
  • months
  • weekdays

The asterisk means “EVERY minute/hour/day/…”. Instead, you can type a specific number (or numbers, separated by a comma) which indicate when the script is about to start. For example, to run the script at 5:34 PM, on the first and fifteenth day of each month, you need to enter:

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34 17 1,15 * * ~/my_script.sh

Finally, to apply changes in the crontab file, run the following command in your terminal:

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crontab /path/to/crontab/file