Watch for web page change

watch-for-change.sh

#!/bin/sh

# Require curl and html-xml-utils

TMPFILE1=$(mktemp)
TMPFILE2=$TMPFILE1-1

function checkIfPageChanged() {
  URL="$1"
  EMAIL_ADDRESS="$2"
  CSS_SELECTOR="$3"
  curl --silent "$URL" -A "Maxme/1.0 (Watching for changes; https://github.com/maxme/)" \
    | hxclean \
    | hxselect "$CSS_SELECTOR" > $TMPFILE1 2> /dev/null
  diff $TMPFILE1 $TMPFILE2 > /dev/null 2> /dev/null
  if [ $? -eq 1 ]; then
    # page changed, send an email
    echo "$URL was modified since last time"
    diff $TMPFILE2 $TMPFILE1 | mail -s "[modified web page] $URL" "$EMAIL_ADDRESS"
  fi
  mv $TMPFILE1 $TMPFILE2
}

if [ x$4 == x ]; then
  echo "Usage: $0 URL EMAIL_ADDRESS SLEEP_TIME_SEC CSS_SELECTOR"
  echo "Example: $0 https://github.com/maxme/bitcoin-arbitrage/pulls pr@bia.is 3600 .issues-listing"
  exit 1
fi

URL=$1
EMAIL_ADDRESS=$2
SLEEP_TIME=$3
CSS_SELECTOR=$4

while True; do
  echo "Check if $URL changed"
  checkIfPageChanged "$URL" "$EMAIL_ADDRESS" "$CSS_SELECTOR"
  sleep $SLEEP_TIME
done