Script to lock OSX on yubikey removal & -HUP yubikey agent

osx-lock-on-remove-yubikey.sh

#!/bin/bash -u

prev_state="unknown"
prev_lock_state="unknown"

state="unknown"
lock_state="unknown"

function lock {
    killall -HUP yubikey-agent
    open -a ScreenSaverEngine.app
}

while true; do
    prev_state=$state
    prev_lock_state=$lock_state
    if $(system_profiler SPUSBDataType 2>/dev/null | grep -q YubiKey); then
        state="attached"
    else
        state="detached"
    fi
    if (ps ax | grep -q [S]creenSaverEngine); then
        lock_state="locked"
    else
        lock_state="unlocked"
    fi
    echo $prev_state, $state, $prev_lock_state, $lock_state
    if [ "$prev_state" = "attached" -a "$state" = "detached" ]; then
        echo locking
        lock
    fi
    if [ "$prev_lock_state" = "unlocked" -a "$lock_state" = "locked" ]; then
        echo "flushing"
        killall -HUP yubikey-agent
    fi
    sleep 1
done