The purpose is to create a script that can create a cronjob on a user’s computer. There are many cron related libraries on npm, however node-crontab is the only one I found that can access the system cron jobs of a computer instead of relying on setTimeout.

Basic Example

const crontab = require('crontab');

crontab.load(function(err, cron) {
  cron.create('ls', '0 7 * * 1-5');
  cron.save();
});

This example shows most of what you need to now. Replace ls with the command to run. The second argument takes the standard cron schedule syntax (in this example the command will run Monday-Friday at 7:00).

You may want to redirect the output of a command like this: ls > /dev/null 2>&1 so that, in the event of any errors, it doesn’t prompt the user with a message upon opening a new terminal session.

Listing Jobs

const jobs = crontab.jobs();

You can check current jobs using the method above or by running the command crontab -l in a terminal.

Summary

For me it was valuable to find this library, because it is the only one available that will actually access system cron jobs. For a real world example, reference my project slack-location-manager.

Further Reading