Monitoring Files and Folders with launchd: WatchPaths in Practice

Thu, 26 Mar 2026 18:56:00 +0000

In the previous post about launchd, scheduling worked by time: StartCalendarInterval defined “every day at 7 AM” and the system took care of the rest, including recovering missed executions when the Mac was asleep. For periodic tasks like sending a daily briefing or running a maintenance script, that model works perfectly — it is the functional equivalent of cron, but integrated into the macOS lifecycle.

But not every automation makes sense tied to a clock. Some tasks only need to happen when something changes. A backup that runs every hour is wasting 23 executions per day if the database was only modified once. An image conversion that runs every 5 minutes has nothing to convert most of the time, and when it finally does, up to 5 minutes have passed since the file appeared. The time-based model works, but it is polling disguised as scheduling — and polling is almost always the least elegant solution to any synchronization problem.

Script-Logic on /var/log/janio

Monitoring Files and Folders with launchd: WatchPaths in Practice