#include <iostream>

int main ()
{
    std::cout << "Hello world!"<<std::endl;
    std::cout << "Goodbye world!"<<std::endl;
    return 0;
}

g++ -g -pg main.cpp -o a.out
./a.out

gprof: can't open: gmon.out (No such file or directory)

ls -la /usr/bin/g++ /usr/bin/clang++