How can I monitor changes to an online PDF simply?

Question

How can I get an alert when changes to an online PDF have occurred? Simple solutions will carry the day.

Answer 1

Do this once:

wget -O file.pdf http://example.com/file.pdf
md5sum file.pdf > file.md5

The set this up in a cron job:

wget -O file.pdf http://example.com/file.pdf
md5sum -c file.md5

Of course, you'll need to modify the paths in the code sample so that the wget and md5sum commands can find the downloaded file. If md5sum does no report OK, then you know the file has changed. Have your script send an alert email or take some other action. (You didn't mention your OS so I answered on how I would do it on Linux.)

Answer 2

Of course, after providing my first answer I found a couple of websites that do this. I've never used any of these so I can't speak to their reputation or reliability. I used free website content monitoring as the Google search term.

• ChangeDetect
• TheWebWatcher
• WatchThatPage