#include <fstream>
#include <iostream>

using namespace std;

int main()
{
char filename[] = "text.txt";
std::fstream file;

file.open(filename, ios::out | ios::trunc);
file << "This text will now be inside of " << filename << std::endl;
file.close();

while(true) {
  file.open(filename, std::ofstream::out | std::ofstream::trunc);
  file.close();
  //do stuff with truncated file
}

file.open(filename, ios::in);
std::string line;
std::getline(file, line);

std::cout << line << std::endl;
}

file.open(filename, ios::out | ios::trunc); // If not exists create - if exists clear.
file.close(); // Here we have got always empty file - even if file is not empty!

SaveFile("text.txt", "");