Hello, It's been years since i've used C++ so i'm trying to get the cobwebs out.

i'm writing a program in C, using a makefile and compiling it with gcc.
using the -D command i'm using things like #ifdef _DEBUG print debuging messages.


In my makefile i have a value called PREFIX which is /usr or /usr/local
I would like to pass that to my program so it knows where it's files are located. but i can't seem to extract the string from the #define.

If i pass it a command like -D pi=3.1415 i can in the program call int someint = 3*3*pi
but i can't get it to work with strings.

I'm assuming it probably can't be done. so how do i at compile time pass this prefix so my program knows where the files it's looking for are?

Thanks
Kevin A