A simple bash script to enable demo mode on a Marshmallow+ device via ADB (based on http://bit.ly/295BHLx)

demo.sh

#!/bin/sh

# License for any modification to the original (linked below):
# ----------------------------------------------------------------------------
# "THE BEER-WARE LICENSE" (Revision 42):
# Sebastiano Poggi wrote this file. As long as you retain 
# this notice you can do whatever you want with this stuff. If we meet some day,
# and you think this stuff is worth it, you can buy us a beer in return.
#
# Based on http://bit.ly/295BHLx

DEBUG=false

function log {
  if [ "$DEBUG" = true ]; then
    echo "🐞 [DEBUG] $1"
  fi
}

function checkAdb {
  if [[ $ADB == "" ]]; then
    ADB=adb
  fi

  command -v $ADB >/dev/null 2>&1 || { echo >&2 "❌ This command requires adb but it’s not on the PATH.\nYou can specify adb's path with the ADB variable."; exit 1; }
  log "Using ADB with command: '$ADB'"
}

function silent {
  $1 &>/dev/null
}

function readClockFromDeviceOsVersion {
  VERSION=$($ADB shell getprop ro.build.version.release)
  log "Read version: $VERSION"

  # Example VERSION: "8.1.0"
  MAJOR=${VERSION%%.*}   # Drop VERSION from first '.' onwards
  MINOR=${VERSION#*.}    # Drop VERSION before first '.' (included)
  MINOR=${MINOR%%.*}     # Drop MINOR from first '.' onwards
  log "Parsed: major='$MAJOR', minor='$MINOR'"

  if [[ $MINOR == "" ]]; then
    MINOR="0"
  fi
  if [[ $MAJOR != "" ]]; then
    echo "ℹ️  Using device Android version for clock time. Detected version: $MAJOR.$MINOR"
    MAJOR=$(printf %02d $MAJOR)   # Left-pad with zeroes to 2 digits

    if [[ $MINOR -lt 10 ]]; then
      # Right-pad minor version (e.g., '1' -> '10')
      MINOR="${MINOR}0"
    fi

    HHMM="$MAJOR$MINOR"
    log "Clock value: $HHMM"
  else
    HHMM="1010"
    echo "❌ parsing clock value, using default: $HHMM"
  fi
}

function setupDemoMode {
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command enter || exit"
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command clock -e hhmm ${HHMM}"
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command battery -e plugged false -e level 100"
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command network -e nosim hide"
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command network -e wifi show -e level 4"
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command network -e mobile show -e datatype 4g -e level 4 -e fully true"
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command notifications -e visible false"
}

function enableDemoMode {
  adb shell settings put global sysui_demo_allowed 1
}

############################################## SCRIPT BEGINS HERE #########################################

CMD=$1

checkAdb

if [[ $CMD != "on" && $CMD != "off" ]]; then
  echo "⚠️ Usage: $0 on|off [hhmm]" >&2
  exit
fi

echo "🔍 Finding device..."
silent "$ADB wait-for-device"

if [ $CMD == "on" ]; then

  if [[ "$2" != "" ]]; then
    HHMM="$2"
  else
    readClockFromDeviceOsVersion
  fi

  echo "ℹ️  Enabling demo mode..."
  enableDemoMode
  setupDemoMode
elif [ $CMD == "off" ]; then
  echo "ℹ️  Disabling demo mode..."
  silent "$ADB shell am broadcast -a com.android.systemui.demo -e command exit"
fi

echo "✅ Done."