title: c_include_path vs ld_library_path
body: <p>On either Ubunutu 12.04 or Springdale 6.4, using gcc and g++, what's the difference between <code>C_INCLUDE_PATH</code> (or <code>CPLUS_INCLUDE_PATH</code>) and <code>LD_LIBRARY_PATH</code>? Is the <code>LD</code> one only used at run-time, and the other two only at compile-time?</p>
  
  <p>Since the <code>INCLUDE</code> and <code>LIBRARY_PATH</code> environment variables seem to be ignored by GCC on these operating systems, which should I set when constructing my ~/.bashrc file to make it as portable as possible (modulo changes in the actual paths) across modern Linux OSes?</p>