price_check.sh

#!/usr/bin/env bash
# GistID: 21910d755c6222cc3e89bce8071c9bd5

STATE_FILE="/tmp/price_prev"

price=$($1)
subject=$2
notify=${3:-'true'}

prev=""
[ -f "$STATE_FILE" ] && prev=$(cat "$STATE_FILE")

color="\033[0m"

if [ -n "$prev" ]; then
  if (( $(echo "$price > $prev" | bc -l) )); then
    color="\033[31m"   # green
    [ $notify == "true" ] && notify-send --app-name=notifphone "Prix a changé" "Le prix $subject <b>augmente</b> : $price €"
  elif (( $(echo "$price < $prev" | bc -l) )); then
    color="\033[32m"   # red
    [ $notify == "true" ] && notify-send --app-name=notifphone "Prix a changé" "Le prix $subject <b>baisse</b> : $price €"
  fi
fi

printf "${color}%s\033[0m\n" "$price"

echo "$price" > "$STATE_FILE"