Linux Shared Libraries c++

Question

I have a Shared Library wise.so. How I can use it in my programm? Do I need to include headers of that library?

I work with Eclipce under Linux. I have set a path to the library using -L and -l. But my function is not visible in the program.

Could you explain me how does Shared Library work?

Regards.

EDIT:

I get the following error:

int main() {
    char* path = "/export/home/pdmazubi3/workspace/proj1/src/pic.jpg";
    CEDD_Descriptor::CEDD ced; // undefined reference to `CEDD_Descriptor::CEDD::CEDD[in-charge]()'
    ced.execute(path);
}

Header:

class CEDD
    {
        public:
            CEDD(double Th0, double Th1, double Th2, double Th3,bool CompactDescriptor);
            CEDD();
            ~CEDD(void);

            double T0;
            double T1;
            double T2;
            double T3;
            bool Compact;

            double* execute(char* path);

        private:
            int cedd_segnum;                //number of segments
            int* cedd_partitionSize;        //number of pixels in each segment
    };

Answer 1

You need to include the header file in your application and link against it.

Have a look at how to use libraries in shared libraries and Linux howto .

If the header file is not in the same directory as your application (which it usually isn't) then you need to tell compiler where to look for it, you use -I/path/to/include to include path to include directory that contains the header file.

In linking step you need to point to the library. The general usage is to use -L/path/to/lib is path to directory containing your library followed by -l<libname> where <libname> is the name of library without lib eg if you have libboost_serialization-d-1_34_1.so you would use -lboost_serialization-d-1_34_1

Examples:

g++ -I/sw/include -Wall -g -I/usr/local/include/boost-1_36/ -c main.cpp -o main.o
g++ -L/sw/lib -lboost_serialization-d-1_34_1 -o x main.o 

Answer 2

Have you also modified the Include path (the -I option) so it knows where to look for the headers for the library? If you haven't done this then the compiler will complain about being unable to find functions/classes/structures/etc.