Watch a URL for a specific phrase, use Pushover to alert with back-off.

nexus_watch.sh

#!/bin/bash

# Pushover API key
TOKEN="PUSHOVER_API_KEY_HERE"

# List of device keys to push to
KEYS=( KEY_ONE KEY_TWO )

# Url to monitor
URL=https://play.google.com/store/devices/details?id=nexus_4_16gb
URL_TITLE="Open Nexus4 16gb Product Page"

# Phrase to watch for
PHRASE="In Stock"

#When found, sleep for 5 minutes (to start with)
FOUND_SLEEP=$((60*5))

#Increase the FOUND_SLEEP by 2x each 'find'
FOUND_SLEEP_FACTOR=2

# Function used to send pushover notification.
# Usage: notify $TITLE $MESSAGE
function notify()
{
  for USER in "${KEYS[@]}"
  do
    /usr/bin/curl -s \
    -F "token=$TOKEN" \
    -F "user=$USER" \
    -F "title=$1." \
    -F "message=$2" \
    -F "url=$URL" \
    -F "url_title=$URL_TITLE" \
    -F "priority=1" \
    https://api.pushover.net/1/messages
  done
}

function checkURL()
{
  curl -s $URL | grep -o "$PHRASE"

  if [ $? -eq 0 ]
  then
    notify "Nexus 4 : $PHRASE" "Nexus4 16gb Model status: $PHRASE. Sleeping for $FOUND_SLEEP before resuming monitoring."

    echo "Sleeping for $FOUND_SLEEP"
    sleep $FOUND_SLEEP
    FOUND_SLEEP=$(($FOUND_SLEEP * $FOUND_SLEEP_FACTOR))
  fi
}

echo "Starting URL monitoring."
while true
do
  DELAY=$[ ( $RANDOM % 100 ) + 40 ]

  echo "Checking $URL for $PHRASE"
  checkURL

  echo "Sleeping for $DELAY"
  sleep $DELAY
done
echo "Goodbye!"