How to include custom .h files in /usr/include

Question

I have some custom .h files placed under /usr/include, but in a directory (/usr/include/itsmag1c), and I'm trying to include them in my C file. I'm guessing that because I use

#include "filename.h";

for files in the same directory, and I would use angle brackets for including a file like math.h or stdio.h. Am I right in guessing that I would use the angle brackets for including my custom header files? If so, my program wont compile, I get the error that the included files cannot be found. Can someone please point to me how I would include these files, or would it be best to have them in the same directory as my program?

Answer 1

Two choices:

1. Use #include <itsmagic1c/filename.h>

2. Use #include <filename.h> as before but add a -I switch.

Boost etc use method 1. (which works well provided you have Boost installed in system locations as you would on a reasonably standard Linux box with reasonable package management).

Method 2. is fine too, but more work on the build system, Makefiles, etc.