How can I wait until xscreensaver is unlocked?

Question

How can I wait until xscreensaver is unlocked? xscreensaver-command -lock locks the screen, but it returns before the screen is unlocked again. xscreensaver provides an xscreensaver-command -watch to print UNBLANK events, but how do I parse them and make sure xscreensaver-command -watch is killed afterwards?

Answer 1

This program will exit after xscreensaver is unlocked (or "unblanked" after an activation that does not require a password):

#!/bin/bash

set -eu

FIFO=/tmp/xscreensaver-wait-for-unlock-$$.fifo
rm -f "$FIFO"
mkfifo "$FIFO"

# Kill `xscreensaver-command -watch` when we exit
trap "exit" INT TERM
trap "kill %1; rm -f $FIFO" EXIT

xscreensaver-command -watch > $FIFO &

while read line; do
    if echo -E "$line" | grep -q "^UNBLANK "; then
        # Make sure the screen is actually unlocked
        xscreensaver-command -time | grep -q " screen non-blanked since " && exit 0 || echo "saw UNBLANK but screen was not unlocked"
    fi
done < $FIFO