One of my friends writes, "the wiki language is really nice, i'd like to use the converter as a standalone parser similar to txt2html on the unix shell command line."
I think, you might be interested in this: http://sourceforge.net/projects/wiki2xhtml/. It is written in Java, currently in beta stage. GUI is planned.
Others are others and me is me.
Basically you would have to implement (or incorporate) engines for different wikis… Or create an universal engine with different rulesets for different wikis…
I think it might be quite complicated if you want to go beyond simple formatting rules. Things like bold, italic are easy to implement, but other have quite complicated patterns/regular expressions (at least for the engines I know).
If you want I can give you access to Wikidot's parser (based on PEAR::Text_Wiki) — I think Text_Wiki is a very good base for writing a universal parser… But it is written in PHP. So command-line would be quite limited (not everyone has a PHP installed). Python would be better IMHO.
michal
Michał Frąckowiak @ Wikidot Inc.
Visit my blog at michalf.me