How do I execute a command and get the output of the command within C++ using POSIX?

Question

I am looking for a way to get the output of a command when it is run from within a C++ program. I have looked at using the system() function, but that will jus

Answer 1

#include 
#include 
#include 
#include 
#include 
#include 

std::string exec(const char* cmd) {
    std::array buffer;
    std::string result;
    std::unique_ptr pipe(popen(cmd, "r"), pclose);
    if (!pipe) {
        throw std::runtime_error("popen() failed!");
    }
    while (fgets(buffer.data(), buffer.size(), pipe.get()) != nullptr) {
        result += buffer.data();
    }
    return result;
}

Pre-C++11 version:

#include 
#include 
#include 
#include 

std::string exec(const char* cmd) {
    char buffer[128];
    std::string result = "";
    FILE* pipe = popen(cmd, "r");
    if (!pipe) throw std::runtime_error("popen() failed!");
    try {
        while (fgets(buffer, sizeof buffer, pipe) != NULL) {
            result += buffer;
        }
    } catch (...) {
        pclose(pipe);
        throw;
    }
    pclose(pipe);
    return result;
}

Replace popen and pclose with _popen and _pclose for Windows.