move to position 2 in the stream and output a 0 in position 2 : file pointer « File Stream « C++ Tutorial

1. C++ Tutorial
2. File Stream
3. file pointer

#include <iostream>
#include <fstream>

using namespace std;

int main(int argc, char** argv)
{
  ofstream fout("test.out");

  fout << "12345";

  long curPos = fout.tellp();
  if (curPos == 5) {
    cout << "Test passed: Currently at position 5" << endl;
  } else {
    cout << "Test failed: Not at position 5" << endl;
  }

  fout.seekp(2, ios_base::beg);
  fout << 0;
  fout.flush();

  ifstream fin("test.out");
  int testVal;
  fin >> testVal;
  if (testVal == 12045) {
    cout << "Test passed: Value is 12045" << endl;
  } else {
    cout << "Test failed: Value is not 12045 (it was " << testVal << ")" << endl;
  }
}