1.Save this code1 as lockWatcher.swift2:

#!/usr/bin/env swift

import Foundation

class ScreenLockObserver {
    init() {
        let dnc = DistributedNotificationCenter.default()

        // listen for screen lock
        let _ = dnc.addObserver(forName: NSNotification.Name("com.apple.screenIsLocked"), object: nil, queue: .main) { _ in
            NSLog("Screen Locked")
            self.runBashScript(path: "~/bin/logout.sh")
        }

        // listen for screen unlock
        let _ = dnc.addObserver(forName: NSNotification.Name("com.apple.screenIsUnlocked"), object: nil, queue: .main) { _ in
            NSLog("Screen Unlocked")
            self.runBashScript(path: "~/bin/login.sh")
        }

        RunLoop.main.run()
    }

    private func runBashScript(path: String) {
        let task = Process()
        task.launchPath = "/bin/bash"
        task.arguments = ["-c", path]
        task.launch()
        task.waitUntilExit()
    }
}

let _ = ScreenLockObserver()

chmod +x lockWatcher.swift

1. Go to Settings -> General -> Login Items
2. Click the + under the Open at Login list.
3. And select the lockWatcher.swift2 file.