Where do I find the header files for C on OS X Mountain Lion?

Question

Where do I find the header files for C on OSX Mountain Lion?

A few articles on the web say they are in /usr/include but when I cd to /usr there is no include folder!

Answer 1

From Paul R's comment:
"You need to install Xcode and the CLT (Command Line Tools) first - they are not installed by default."

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So first download Xcode from App Store. Once you have Xcode.app, install the command line tools it includes.

Only then are the headers available in their default locations. (/usr/include)

Answer 2

I have just found a working solution to install the include/ directory which contain the headers that you are looking for (Mojave 10.14.6 - Xcode 10.3), just run :

open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg