Execute a shell command, reading its output

run.cc

#include <iostream>
#include <stdexcept>
#include <string>

std::string run(const char* cmd)
{
        FILE *in;
        char buff[512];
        std::string result;

        if(!(in = popen(cmd, "r")))
                throw std::runtime_error("popen() failed");

        while(fgets(buff, sizeof(buff), in)!=NULL) result += buff;

        pclose(in);
        return result;
}

int main()
{
        std::cout << run("ls -sail");
        run("ls -sail"); // won't print anything
        return 0;
}