How to include header files from different directories?

Question

Hi,
Sorry for the newb question, but I can't figure this out. I'm trying to compile a simple piece of code (C++) that uses header files in a directory different from the Project directory; header files are in /opt/csw/postgresql/include/pqxx. I've tried a few different things, adding that directory to the include directives under Resource Files, add existing files from a folder, etc etc. Whenever I try to build, dmake bails with status -1. I can't seem to get this working, can someone explain how to use header files from different directories?
Thanks,
SlowToady

Answer 1

Header files are usually specified relative to a base directory. If the base directory is not a system directory -- /usr/include or the compiler installation directory -- add a command-line directive
-I path/to/base/dirfor each such directory.
The path can be absolute, such as
-i /opt/csw/postgresql/includeor relative, such as
-I ../../my/includeIn your source code, specify the header file relative to the base directory, and be sure to use quotes, not angle brackets. Example:
#include "header.h"  // right
#include <header.h>  // wrongThe angle brackets are used for system headers, like <iostream> or <stdlib.h>.
The rules above are common to all compilers on Unix and Linux, and generally to all C and C++ compilers.
For more details, read about the -I option in the C++ Users Guide. You can find the guide by pointing your browser to the "docs" directory in the compiler installation, or go here:
http://docs.sun.com/app/docs/doc/819-5267
All command-line options are described in Appendix A.