watch xscreensaver for lock and unlock

xscreensaver_watch.sh

#!/bin/sh
# Watch xscreensaver and react to status changes.
#
# Replaced my previous perl-based recipe with this:
# http://semicomplete.googlecode.com/svn/tools/xscreensaver-watch.sh
#
# Include somewhere in X session startup with:
#
#     xscreensaver-watch &

lock() {
    # Log this somewhere with `date` instead of just echoing.
    echo `uname -n` screen is now blank
    # Do other things here, like stop music playback & mute speakers.
}

unlock() {
    # Log this somewhere with `date` instead of just echoing.
    echo `uname -n` screen is now unblank
    # Do other things here, like resume music playback & unmute speakers.
}

xscreensaver-command -watch | while read a; do
    echo "$a" | grep -q '^LOCK' && lock
    echo "$a" | grep -q '^UNBLANK' && unlock
done