http://stackoverflow.com/questions/23400933/most-efficient-way-of-creating-a-progress-bar-while-reading-input-from-a-file

progress.cpp

float aProgress = 0.0;
while (aProgress < 1.0) {
    int aBarWidth = 70;

    std::cout << "[";
    int aPos = (int) (aBarWidth * aProgress);
    for (int i = 0; i < aBarWidth; ++i) {
        if (i < aPos) std::cout << "=";
        else if (i == aPos) std::cout << ">";
        else std::cout << " ";
    }
    std::cout << "] " << (int) (aProgress * 100.0) << " %\r";
    std::cout.flush();

    aProgress += 0.16; // for demonstration only
}
std::cout << std::endl;