Linux: Monitoring changes in a webpage

Question

I have some web pages that I need to frequently check. Is there any tool that will check for updates and send notifications by mail or RSS. These pages are not RSS supported.

I am looking for a Linux standalone application, browser extension, or a service that sends mails.

Answer 1

I use http://www.watchthatpage.com/ which allows you to add pages and when the content changes they send an email. Works well for me most of the time, but they occasionally get blocked as spam, I suspect because people forget they have set it up.

Answer 2

Even if a site doesn't have RSS, you can add it to Google Reader and be notified of changes to the page.

Answer 3

I've never tried it, but something like http://page2rss.com/ could work.

Answer 4

Simple script with database can do it.

Pseudocode:

page_url = 'http://site.com/page_to_check'
page_content = http_fetch(page_url)
md5_page_hash = md5(page_content)
//query database
result = db.query('SELECT * FROM pages WHERE url="page_url"')
if(result) {
  //webpage info is already in db
  //check hashes
  if(md5_page_hash != result.page_md5_hash) {
    //page updated, so we can send notification letter, sms, etc...
    //...  notification stuff
    //...
    //update md5 hash of the page in db
    db.query('UPDATE pages WHERE url="page_url" SET page_md5_hash="md5_page_hash"')
  }
} else {
  //there is no info about this page in db, so add it
  db.query('INSERT pages(page_url, page_md5_hash) VALUES("page_url", "md5_page_hash")')
}