Thread: Quick Compilation Question

I have a directory structure somewhat like the whats below with many more levels and many more source and header files. In all the source files, the headers are included with "String.h" regardless of the current files location (so that would be the include used in say Prime.c). I am currently using the -I option with all of the directories to get it to find the headers. Is there some easier way, for example some recursive -I option that I could just say -I src?

proj
---Makefile
---src
------Makefile
------util
---------Makefile
---------Threads.c
---------Threads.h
---------String.c
---------String.h
------math
---------Makefile
---------Prime.c
---------Prime.h
---------Matrix.c
---------Matrix.h
---bin
---lib

Thanks!
chacham15