As I asked earlier, I was trying to figure out who the current user is. Since the proposed solution doesn't work, I thought, okay, let's try sending notifications from a LaunchAgent! Only, right, notifications are per-process, so I tried Distributed Notifications... and that doesn't seem to work across users. (Now, since I log while also sending the distributed notifications, I can see that it is working the way I want. Except that willPowerOffNotification doesn't actually seem to happen with a logout. Maybe that's because it's a CLI program? But the other notifications do work...)
