#!/bin/sh
# Repeatedly download a specified web page
# until a specified regexp matches its source
# then notify the specified email address.
#
# For example:
# watch_website.sh http://ticketek.com.au/ 'Ke[sS$]+ha' andrewt@unsw.edu.au

repeat_seconds=300  #check every 5 minutes

if test $# = 3
then
    url=$1
    regexp=$2
    email_address=$3
else
    echo "Usage: $0 <url> <regex> <email-address>" 1>&2
    exit 1
fi

while true
do
    if curl --silent "$url"|grep -E "$regexp" >/dev/null
    then
        # the 2nd echo is for testing, remove to really send email
        echo "Generated by $0" |
        echo mail -s "website '$url' now matches regex '$regexp'" "$email_address"
        exit 0
    fi
    sleep $repeat_seconds
done