Title Capitalization of Keywords in Programming Languages

It should not be capitalized. If you're trying to make your documentation useful, don't introduce unnecessary complexities.

Use the lowercase int (in fact, use it in a different font, preferably monospaced) for the titles. And comment on the fact that it's lowercase, the first few times you use it, and explain why you're using it.

If you're writing about Unix or any dialect of C, your readers may often need orientation to the types of text conventions involved in programming, in contrast to the types involved in more ordinary writing.