Tutorial on writing an extension library

[Ian Nicholson]

I'd like to write a simple c++ plugin that writes a string to a text 
file, but the documentation on developer.ubuntu.com isn't really 
clicking for me.  Is there a tutorial out there that walks through what 
I need to do, or some sample code?
Unfortunately I haven't touched c++ for a while, so I need something 
basically targeted at a beginner.