+#!/bin/sh
+
+# Helper script to start/lock the screen with an available screen locker.
+
+# Copyright (C) 2015 Simon Ruderich
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+set -eu
+
+
+usage() {
+ printf 'usage: %s start <lock time (min)> <lock binary>\n' "$0"
+ printf ' %s lock\n' "$0"
+ exit 1
+}
+
+installed() {
+ type "$1" >/dev/null 2>&1
+}
+
+
+if test $# -eq 0; then
+ usage
+fi
+
+if test x"$1" = xstart; then
+ if test $# -ne 3; then
+ usage
+ fi
+ lock_time_minutes="$2"
+ lock_binary="$3"
+
+ # NOTE: We must redirect stdout of the spawned background processes to
+ # /dev/null or a potential caller which uses our output will wait forever
+ # on the inherited stdin (and we become a zombie)! Thanks to Beano on [1]
+ # for the idea, read on 2015-08-23.
+ #
+ # [1]: https://stackoverflow.com/questions/3748432/insane-crond-behavior-keeps-making-defunct-bash-processes/3750028#3750028
+
+ if installed xscreensaver; then
+ echo "xscreensaver.lockTimeout: $lock_time_minutes" | xrdb -merge
+ xscreensaver >/dev/null &
+ echo xscreensaver
+ elif installed xautolock; then
+ if installed "$lock_bin"; then
+ xautolock -secure -time "$lock_time_minutes" \
+ -locker "$lock_binary" \
+ >/dev/null &
+ echo xautolock
+ else
+ echo "Locker '$lock_bin' not installed. Auto lock won't work!"
+ exit 1
+ fi
+ else
+ echo "No locker found. Auto lock won't work!"
+ exit 1
+ fi
+
+elif test x"$1" = xlock; then
+ if test $# -ne 1; then
+ usage
+ fi
+
+ if installed xscreensaver; then
+ # Start xscreensaver if it's not already running. xscreensaver-command
+ # ensures xscreensaver is available for the current X session.
+ xscreensaver-command -time >/dev/null 2>&1 || xscreensaver &
+
+ xscreensaver-command -lock
+ # It can take a while for xscreensaver to start, wait until it's
+ # ready.
+ while test $? -eq 255; do
+ xscreensaver-command -lock
+ done
+ elif installed xtrlock; then
+ # Sleep is necessary to allow xtrlock to grab the keyboard input.
+ sleep 1
+ xtrlock
+ else
+ echo 'No screen locker found!'
+ exit 1
+ fi
+
+else
+ usage
+fi