El Capitan availability checker - read the installation instructions in the bash script below

checker.sh

#!/usr/bin/env bash

# Installation instructions:
#   $ curl -s https://gist.githubusercontent.com/frdmn/c6700ade5a0fc906271f/raw/checker.sh > /usr/local/bin/osx-checker
#   $ chmod +x /usr/local/bin/osx-checker
#   $ osx-checker

URL="https://itunes.apple.com/search?entity=macSoftware&term=OS+X"
SEARCH_STRING="OS X El Capitan"
TIMEOUT_IN_SECONDS="60"

echo "${SEARCH_STRING} MAS availability checker"
echo ""

while true; do
  curl -s "${URL}" | python -mjson.tool | grep "trackCensoredName\": \"${SEARCH_STRING}"

  if [ "$?" == "0" ]; then
    say "${SEARCH_STRING} is now available for download"
    open $URL
    exit
  else
    echo "Nothing found yet. Trying again in ${TIMEOUT_IN_SECONDS} seconds..."
  fi

  sleep ${TIMEOUT_IN_SECONDS}
done