On 04/10/2012 02:26 PM, H Vlems wrote: yes I know you did but the terms static and dynamic library just didn't register. Ahh ok. Do you understand the difference now? If not I can type up an explanation of how it all works. Are .so and .a libraries interchangeable for the linker, i.e. would this have worked too: NETWORK_OPT = -DUSE_NETWORK -isystem /usr/local/include /usr/lib/libpcap.so This is compiler-dependent, but it generally should work. The "proper" way to link against a library, though, is to use "-l<libname>" on the link command. -Dave -- Dave McGuire, AK4HZ New Kensington, PA