Run script on OSX when doing fast user switching

Question

Is it possible to setup a script to run when users switch through fast user switching on OSX (El Capitan)? Earlier on, one could use a thing like this: http://www.radiotope.com/content/os-x-how-perform-action-during-fast-user-switch - but this method has not been possible for years now.

Answer 1

After some tries in wrong directions I came up with this quite elegant solution. My aim was to start and stop VPN connection only for specific Mac user. You can add final binary to User's login items or create a user agent in ~/Library/LaunchAgents More info: https://www.launchd.info/

You will need to be familiar with Swift and Xcode.

Create MacOS, Command line Tool project in Xcode and paste the following into main.swift

import AppKit

class VPNManager {
    init() {
        NSWorkspace.shared.notificationCenter.addObserver(
            self,
            selector: #selector(becameActive),
            name: NSWorkspace.sessionDidBecomeActiveNotification,
            object: nil
        )
        NSWorkspace.shared.notificationCenter.addObserver(
            self,
            selector: #selector(becameInactive),
            name: NSWorkspace.sessionDidResignActiveNotification,
            object: nil
        )
    }

    @objc func becameActive() {
        print("Workspace became active... starting VPN")
        let task = Process()
        task.launchPath = "/usr/sbin/networksetup"
        task.arguments = ["-connectpppoeservice","PrivateVPN (L2TP)"]
        let pipe = Pipe()
        task.standardOutput = pipe
        task.standardError = pipe
        task.launch()
        task.waitUntilExit()
        let data = pipe.fileHandleForReading.readDataToEndOfFile()
        let output = String(data: data, encoding: .utf8)
        print("start result:", output ?? "empty")
    }

    @objc func becameInactive() {
        print("Workspace became inactive... stopping VPN")
        let task = Process()
        task.launchPath = "/usr/sbin/networksetup"
        task.arguments = ["-disconnectpppoeservice","PrivateVPN (L2TP)"]
        let pipe = Pipe()
        task.standardOutput = pipe
        task.standardError = pipe
        task.launch()
        task.waitUntilExit()
        let data = pipe.fileHandleForReading.readDataToEndOfFile()
        let output = String(data: data, encoding: .utf8)
        print("stop result:", output ?? "empty")
    }
}

let vpnManager = VPNManager()

print("VPNManager initialized")
RunLoop.current.run()
print("VPNManager exiting")