How to use File in c++ code example

Example 1: file c++

#include <iostream>
#include <string>
#include <fstream> //write and read
//#include <ifstream> //read
//#include <ofstream> //write

int main () {
  std::string line;
  std::ofstream myfileWrite;
  std::ifstream myfileRead;
  myfileWrite.open("example.txt");
  myfileRead.open("example.txt");
  myfileWrite << "Writing this to a file.\n";
  while (getline(myfileRead,line)){
    std::cout << line << '\n';
  }
  myfileWrite.close();
  myfileRead.close();
  return 0;
}

Example 2: How to read a file in in C++

// io/read-file-sum.cpp - Read integers from file and print sum.
// Fred Swartz 2003-08-20

#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;

int main() {
    int sum = 0;
    int x;
    ifstream inFile;
    
    inFile.open("test.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1); // terminate with error
    }
    
    while (inFile >> x) {
        sum = sum + x;
    }
    
    inFile.close();
    cout << "Sum = " << sum << endl; 
    return 0;
}