Update to v4.0. Add shell script

Author: alex-mous

PrinterPiServer/power_button.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+#
+#   power_button.sh - Script to monitor power button (GPIO2) and shutdown if pressed.
+#   Also controls LED to indicate shutdown (GPIO4)
+#
+#   Copyright (C) 2020  PolarPiBerry
+#
+#   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 <https://www.gnu.org/licenses/>.
+echo "2" > /sys/class/gpio/export
+echo "in" > /sys/class/gpio/gpio2/direction
+
+echo "4" > /sys/class/gpio/export
+echo "out" > /sys/class/gpio/gpio4/direction
+
+echo "1" > /sys/class/gpio/gpio4/value;
+sleep 3;
+echo "0" > /sys/class/gpio/gpio4/value;
+
+sleep 20; #Wait at least 20 seconds before taking affect
+
+while true; do
+        state=`cat /sys/class/gpio/gpio2/value`;
+        if [ $state = "0" ]; then
+                echo "1" > /sys/class/gpio/gpio4/value;
+                sleep 3;
+                state=`cat /sys/class/gpio/gpio2/value`;
+                if [ $state = "0" ]; then
+                        echo "Shutting down now"
+                        sudo shutdown -h now
+                fi
+        fi
+        sleep 1;
+done;
+