[Greg Ross]

Where did the grep find it? Was it in a .h file? What does the definition look like?

What you should have is something like

int drive_mode;

in ONE .c file. And (assuming you really need to reference the variable in another program) in your .h file, put

extern int drive_mode;

If you have the

int drive_mode;

(without the extern keyword) in a .h file, and #include it in multiple files, you will get a multiple definition error.