Cycle the screen through "locked" and "unlocked" states while leaving user input blocked

lock-control.sh

#!/bin/bash

# Script to control screen lock
#
# Dependencies: xtrlock, xscreensaver and xscreensaver-command
# 
# Use case: you want the cycle the screen between ON (all windows visible)
# and OFF (blank screen saver, password needed to unlock) states while disabling user input
# when screen is ON. Great for kiosk PC-s to turn the screen off during the night.
# 
# The screen can either be "locked" or "unlocked"
#   - locked: screen is "blank" (screensaver), needs a password to unlock
#   - unlocked: everything on the screen can be seen, but no user input is allowed (xtrlock)
#
# Usage Example:
#  These cron entries lock the screen after the workday ends and unlock it at 9am.
#  cron: name="lock-screen" minute="0" hour="09" weekday="1-5" job="/usr/local/bin/lock-control --lock" user=kiosk
#  cron: name="unlock-screen" minute="0" hour="18" weekday="1-5" job="/usr/local/bin/lock-control --unlock" user=kiosk
#
# Author Ando Roots <ando@sqroot.eu> 2016

function usage
{
    echo "usage: lock-control.sh [-l] | [-u] | [-h]"
}

function lock
{
  echo "Locking screen..."

  # Kill xtrlock if it's running
  if pidof "xtrlock" > /dev/null
  then
    killall xtrlock
    sleep 1
  fi

  # Start xscreensaver if it's not running
  if ! pidof "xscreensaver" > /dev/null
  then
    echo "Starting xscreensaver..."
    DISPLAY=:0 xscreensaver -nosplash &
    sleep 1
  fi
  
  # Lock screen
  DISPLAY=:0 xscreensaver-command -lock
}

function unlock
{
  echo "Unlocking screen..."
  
  # Stop the screensaver
  if pidof "xscreensaver" > /dev/null
  then
    killall xscreensaver
    sleep 1
  fi
  
  # Disable user input
  DISPLAY=:0 xtrlock &
}

while [ "$1" != "" ]; do
    case $1 in
        -l | --lock )           shift
                                lock
                                ;;
        -u | --unlock )         unlock
                                ;;
        -h | --help )           usage
                                exit
                                ;;
        * )                     usage
                                exit 1
    esac
    shift
done