LaunchAgents

On launchd and launchdctl:
https://www.launchd.info

On launchd.plist:
https://www.manpagez.com/man/5/launchd.plist/

LaunchAgent-AppDelegate-DispatchSource

private func setupEventHandlers() {
    signal(SIGHUP, SIG_IGN)
    signal(SIGINT, SIG_IGN)
    signal(SIGTERM, SIG_IGN)
    
    sighupSource.setEventHandler {
        [weak self] in
        
        self?.handleQuitEvent("SIGHUP")
    }
    sighupSource.resume()
    
    sigintSource.setEventHandler {
        [weak self] in
        
        self?.handleQuitEvent("SIGINT")
    }
    sigintSource.resume()
    
    sigtermSource.setEventHandler {
        [weak self] in
        
        self?.handleQuitEvent("SIGTERM")
    }
    sigtermSource.resume()
}

LaunchAgent-AppDelegate-NotificationCenter

Launch agent with AppDelegate should use NotificationCenter

private func setupWorkspaceNotifications() {
    let center = NSWorkspace.shared.notificationCenter
    center.addObserver(self, selector: #selector(AppDelegate.handleWillPowerOff(_:)), name: NSWorkspace.willPowerOffNotification, object: nil)
}

@objc
private func handleWillPowerOff(_ notification: Notification) {
    handleQuitEvent()
}

LaunchAgent-DispatchSource

func main() -> Int32 {
    signal(SIGTERM, SIG_IGN)
    let termSource = DispatchSource.makeSignalSource(signal: SIGTERM)
    termSource.setEventHandler {
        handleQuitEvent()
        
        exit(EXIT_SUCCESS)
    }
    termSource.resume()
    
    dispatchMain()
}

Additional Information

LLDB process handling

To change how LLDB handles signals:

process handle <SIGNALNAME> [ --pass <true|false|1|0> ] [ --stop <true|false|1|0> ] [ --notify <true|false|1|0> ]

Sample:

process handle SIGTERM --stop false --pass true

Launch agent *.plist (App.plist)

LSUIElement <boolean>

A Boolean value indicating whether the app is an agent app that runs in the background and doesn't appear in the Dock.

Launch agent *.plist (launchd.plist)

ExitTimeOut <integer>

The amount of time launchd waits before sending a SIGKILL signal. The default value is 20 seconds. The value zero is interpreted as infinity.

Notes

Each sample has a directory Install which contains helper shell scripts to install (generate launchd.plist) and run the launch agent.