netz39-infra-ansible/templates/hobbes/kiosk.sh.j2

#!/bin/bash

# Check if the script is run by root
if [ "$EUID" -ne 0 ]
  then echo "Please run as root"
  exit
fi

# MQTT broker details
BROKER="{{ kiosk_mqtt_host }}"
TOPIC="{{ kiosk_mqtt_topic }}"

# Variable to store the PID of the fbi process
fbi_pid=0

# Function to be executed on SIGTERM
on_sigterm() {
    echo "SIGTERM received, exiting..."

    # Kill the fbi process
    # As the process forks itself, we do not get a reliable PID and killall is needed
    killall fbi

    # Remove the temporary file
    rm -f /tmp/grafana.png
    exit 0
}

# Trap SIGTERM and call on_sigterm() when it is received
trap 'on_sigterm' SIGTERM

while true
do
    # Subscribe to the topic and save received data to a file
    mosquitto_sub -h $BROKER -t $TOPIC -C 1 > /tmp/grafana.png

    # Kill the previous fbi process
    # As the process forks itself, we do not get a reliable PID and killall is needed
    killall fbi

    # Display the image
    fbi -T 1 -noverbose -a /tmp/grafana.png &

    # Wait to avoid a race condition between
    # fbi starting and mosquitto truncating the file
    sleep 1
done