Selective HDMI vs Hyperpixel switch

rc.local.switch-screen.sh

#!/bin/sh

# Original source in https://forums.pimoroni.com/t/hyperpixel-selective-output-eg-on-boot/5193/15
#
# Reboots the RPi enabling/disabling HDMI/Hyperpixel depending if HDMI is used or not
# If the machine starts to reboot on a loop, mount /boot on a different machine, and
# create a file in /boot/no-display-reboot

_HDMI_DEVICE=$(tvservice -l | perl -n -e '/Display Number (\d+), type HDMI 0$/ && print $1')

if [ -z "$_HDMI_DEVICE" ]; then
  _HDMI_EXISTS=false
else
  _HDMI_EXISTS=$(tvservice -v $_HDMI_DEVICE -d /dev/null | grep "^Written ")
fi

# Check to see if HDMI display is connected.
#_HDMI_EXISTS=$(tvservice -l | grep "HDMI" ) || true
# Is device in LCD mode?
_ISLCD=$(tvservice -s | grep "LCD") || true

if [ -z "$_HDMI_EXISTS" ]; then
  if [ "$_ISLCD" ]; then
    echo "[  \e[32mOK\e[39m  ] NO HDMI connected, Hyperpixel display config already active\n"
    #do nothing
  else
    echo "[\e[91mFAILED\e[39m] NO HDMI connected, switching to Hyperpixel config\n"
    #change config to Hyperpixel and reboot since no display detected
    sudo cp /boot/hyper-config.txt /boot/config.txt

    if [ ! -e "/boot/no-display-reboot" ]; then
      sudo reboot
    fi
  fi
else
  if [ "$_ISLCD" ]; then
    echo "[\e[91mFAILED\e[39m] HDMI is connected, but Hyperpixel config is being used\n"
    #we need to switch to HDMI display config and reboot
    sudo cp /boot/hdmi-config.txt /boot/config.txt
    if [ ! -e "/boot/no-display-reboot" ]; then
      sudo reboot
    fi
  else
    echo "[  \e[32mOK\e[39m  ] HDMI is connected, HDMI config detected, so turning off LCD BL\n"
    #we need to shut off the GPIO backlight on the Hyperpixel display since we aren't using it
    gpio -g mode 19 out
    gpio -g write 19 0
  fi
fi