A demonstration of using launchd LaunchEvents to trigger LaunchDaemons on-demand (as opposed to cron-like triggering) by taking advantage of Apple's XPC framework. This allows, for example, commands to be run when the network configuration or power state of a Mac changes.
Feel free to use this example per the terms of the included license, although you'll probably want to remove the smaddock references from any production use. ;)
This is a port of @snosrap's Objective-C XPC event handler to a Javascript for Automation (JXA) handler. Many thanks to @PicoMitchell for the JXA help!
- This example launches on BSD notifications (
com.apple.notifyd.matching) instead of IOKit events (com.apple.iokit.matching) but either or both are possible in the same LaunchDaemon. - Why JXA: https://scriptingosx.com/2021/11/the-unexpected-return-of-javascript-for-automation/
- Why LaunchEvents must be consumed: https://stackoverflow.com/questions/13987671/launchd-plist-runs-every-10-seconds-instead-of-just-once
- Why the process must not exit after consuming: https://developer.apple.com/forums/thread/133915
- At WWDC 2022 Apple announced some changes to how launchd services will be handled in macOS 13; it's unclear at the time of writing if this will impact the functionality demonstrated in this repository.
To execute this example as-is:
- Install the files
- munkipkg method:
- Install munkipkg
- Clone this repository locally
- Run
munkipkgon the repo local root directory - Run the installer built by
munkipkg
- Manual method:
- Copy the files from the payload directory of this repo to their corresponding location in your filesystem
- Change the owner of all the copied files to
root - Run
sudo launchctl bootstrap system /Library/LaunchDaemons/com.github.smaddock.xpc_handler.plist
- munkipkg method:
- Test the LaunchEvents
- Turn your WiFi off and on a couple times
- Sleep and wake your Mac a couple times
- Inspect
/private/var/log/smaddock.logto see the logged events