As an ad-hoc method, it's been common in some perl apps I use to maintain an ever-larger list of extensions (.c, .cpp, .h, .pl, ...) to recognize if a file is source code. I can think of a number of problems with this approach:

1) All files have to have an extension. It's not uncommon for people to save scripts and makefiles without one.
2) There's an implicit assumption that there is a one-to-one mapping between each unique extension and the kind of content it should have.
3) You have to continually maintain a list of these extensions.

There's got to be a better way. From within *nix I might often do something like this 

$ file -s some_file.c

[download]

and then see: 

some_file.c: ASCII C program text

[download]

This brings me to some more questions: Is there a nice tidy perl module to accomplish this effect? If not, how best to implement it?

In reply to How best to identify & Categorize Source Code? by Zadeh

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