[c++]Retrieving system information

I'm working with c++ language and I'm trying to collect as much a information as possible on a MAC OS system like ,
nb of cpu,
frequency
usage of cpu
memory
usage of mem
list of process and their cpu usage
...


I searched a bit and it seems that sysctl may be the best to collect most of the needed information but I get odd results for some request like hw.cpufrequency although i get the correct output while using the terminal command.

exemple of request

            int frequency;
            len = sizeof(frequency);
            if (sysctlbyname("hw.cpufrequency", &frequency, &len, NULL, 0) == -1){
                std::cout << "error";
            }
            else{
                std::cout << "frequency of processor " << frequency << std::endl;
            }

This gives me an error while searching for hw.busfrequency works well.

Am i looking at the right tools for this kind of job ?