highlight.js [1] does this, though by running highlighters rather than using some learning-based mechanism. It feels wasteful to run this on display rather than storage, though. SourceClassifier [2] also works, though with less languages. And here's [3] an implementation made with Bayes and Go.

[1] http://softwaremaniacs.org/soft/highlight/en/ http://softwaremaniacs.org/media/soft/highlight/test.html

[2] http://blog.chrislowis.co.uk/2009/01/04/identify-programming...

[3] https://github.com/octplane/go-code-classifier