change file at given position : file pointer « File Stream « C++ Tutorial

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

#include <iostream>    
#include <fstream>   
#include <stdlib.h>   
using namespace std;
main(int argc, char *argv[])   
{   
  if(argc!=3) {   
    cout << "Usage: CHANGE <filename> <byte>\n";   
    return 1;   
  }   
     
  fstream out(argv[1], ios::in|ios::out);   
  if(!out) {   
    cout << "Cannot open file";   
    return 1;   
  }   
     
  out.seekp(atoi(argv[2]), ios::beg);   
     
  out.put('X');   
  out.close();   
     
  return 0;   
}