Any example of writing an NPAPI plugin in Linux?

I need to write a browser plugin to communicate with another process, and it seems I have to use NPAPI plugins. Is there any example or open source NPAPI plugin I can refer to?

Many thanks for your reply.

Summary of answers

1. http://mxr.mozilla.org/seamonkey/source/modules/plugin/samples/
2. http://www.firebreath.org/
3. http://code.google.com/p/nixysa/
4. http://code.google.com/p/npapi-file-io/

2 and 3 are both frameworks to make plugin development easier.

I found one example at http://mxr.mozilla.org/seamonkey/source/modules/plugin/samples/

you could also use the open source FireBreath plugin framework; they are nearing a 1.0 release for windows only, but it would not be hard to port it to linux; mac os shouldn't be bad either, but it will take a little work to get CMake to generate the correct bundle type =]

Yes, I am one of the primary maintainers, so I'm a bit biased. You can also find some good general information on how NPAPI works on my blog, starting here: http://colonelpanic.net/2009/03/building-a-firefox-plugin-part-one/