This code snippet actually contains a few nifty things. There are two functions, hasVisited() and main(). hasVisited() makes use of a very handy function for CGI programmers: getenv. You can see I use it to retrieve REMOTE_ADDR which is the person's IP address. In main() it gets the count from a file and increments if needed and outputs back to the same file. It then outputs a simple HTML page that the user sees.

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

bool hasVisited()
// Figure out wether unique hit or not
// Returns true if ip address has visited
{
  bool visited = false;
  string userIP = getenv("REMOTE_ADDR");
  string nonUnique;

  ifstream input("iplist.cnt");
  while (input) {                   // See if IP is in list
    getline(input, nonUnique);
    if (userIP == nonUnique) {
      visited = true;
      break;
    }
  }
  input.close();
  
  if (visited == false) {               // Add IP to list
    ofstream output("iplist.cnt", ofstream::app);
    output << userIP << endl;
    output.close();
  }

  return (visited);
}


int main() {
  int uniqueHits;   // Default in case no counter file exists
  int rawHits;
  
  ifstream in("counter.cnt");
  if (!in) {
    uniqueHits = 0;
    rawHits = 0;
  }
  else {
    in >> uniqueHits;          // 1st number = unique hits
    in >> rawHits;             // 2nd number = raw hits
    in.close();
  }

  bool visited = hasVisited();  
  rawHits++;
  if (!visited)
    uniqueHits++;

  ofstream out;
  out.open("counter.cnt");  
  out << uniqueHits << ' ' << rawHits; 
  out.close();

  cout << "Content-type: text/html" << endl << endl
       << "<HTML><BODY>" << endl
       << "This is a hit counter written in C++. <hr>" << endl
       << "Your IP address: " << getenv("REMOTE_ADDR") << ".";
  if (visited) 
    cout << "(Not unique)";
  else
    cout << "(Unique)";
  cout << "<hr>" << endl
       << "Unique hits: " << uniqueHits << "<br>Raw hits: " << rawHits << endl;
  cout << "</BODY></HTML>" << endl;
}

Has been taken care of, snippet modified to incorporate the change.
Thanks for notifying this, your help in the code snippet section is greatly appreciated.

Hope you find out more such bugs :D