usb-lock.sh

#!/usr/bin/env bash
USB_SERIAL="TODO"

START_CMD="xscreensaver -no-splash"
LOCK_CMD="xscreensaver-command --lock"
UNLOCK_CMD="killall xscreensaver"

LAST_SEEN=""

#return 1 if device is found, 0 otherwise
function checkUSB()
{
    USB_SERIAL_ID_LIST=$(lsusb -v 2>/dev/null | grep 'iSerial' | awk '{print $3}' | grep '\S')
    for id in ${USB_SERIAL_ID_LIST};
    do
        if [ "$id" = "$USB_SERIAL" ];
        then
            #device detected
            echo "1"
            return
        fi
    done
    #not detected
    echo "0"
    return
}

# Notify us if the state changes
function stateChange()
{
    state=$(checkUSB)
    #echo "S: $state"

    if [[ "$LAST_SEEN" = "1" && "$state" = "0" ]];
    then
        LAST_SEEN=$state
        #device unpluged, lock computer
        echo "Lock"
        $LOCK_CMD > /dev/null
    elif [[ "$LAST_SEEN" = "0" && "$state" = "1" ]];
    then
        LAST_SEEN=$state
        #device plugged in, unlock computer
        echo "Unlock"
        $UNLOCK_CMD 2>/dev/null
        $START_CMD &
    fi
}

# Main loop
while true
do
    stateChange

    sleep 1
done

# Cleanup
kill $!
wait $! 2>/dev/null