I would like to parseout rs5443, 61902 and the 291008.

Easy. Millions of ways to do so.

This could vary in each file.

Yes, well, there's the catch, isn't it? If you can tell how it can vary from file to file, you accomplish two things:

• You're more than halfway finding the answer yourself.
• You increase the chance that a suggestion offered here will actually works for a different file than the example you provide.

A win-win situation!