TIL: Setting cron jobs from Node

Here’s a neat little trick/hack I learned today for being able to quickly control crontab jobs from routes in your node application.

In my case, for testing purposes, I wanted to be able to control when my simulator kicked off traffic without having to log into the box and manually change the file. So I had the idea of adding in two additional routes that would modify the crontab file on the test box: /cronjob/enable and /cronjob/disable.

The goal for this was simple. Create two different txt files, one empty file called clear.txt that would be used to clear the jobs, and another called cron.txt that contained the cron tasks I wanted created.

Cron jobs can be added to crontab by using the following format: crontab <filename>. So the goal now was to be able to send these commands to the command line.

To do so, you can use the following with child-processes:

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const { exec } = require('child_process');
exec('crontab clear.txt', (err, stdout, stderr) => {
 if (err) {
   console.log('Unable to clear cron jobs!');
 } else {
     console.log('Crontab cleared.');
 }
});

And repeat the process on the route for adding the cron job with its respective cron .txt file.

💚