PIPE & cmd linux

#include <iostream>
#include <stdexcept>
#include <stdio.h>
#include <string>
/********************************************************************************/
using namespace std;
/********************************************************************************/
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 (!feof(pipe)) {
            if (fgets(buffer, 128, pipe) != NULL)
                result += buffer;
        }
    } catch (...) {
        pclose(pipe);
        throw;
    }
    pclose(pipe);
    return result;
}
/********************************************************************************/
int main(){
    std::cout <<  exec( "ls");
}
/********************************************************************************/