#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
#include <cstdlib>
using namespace std;
 
struct CommandLineException
{
CommandLineException(int max, int actual)
  {
    cout << endl << "Too many command line arguments." << endl;
    cout << "A maximum of " << max << " arguments are permitted." << endl;
    cout << actual << " arguments were entered." << endl;
  }
};
 
struct FileException
{
  FileException(char* fn)
  {
    cout << endl << "File " << fn << " could not be opened." << endl;
  }
};
 
int main(int argc, char* argv[])
{
 
  try
  {
    char ifn[255], ofn[255];
    switch(argc)
    {
      case 1:
        cout << "Enter the input file name. ";
        cin >> ifn;
        cout << "Enter the output file name. ";
        cin >> ofn;
        break;
      case 2:
        strcpy(ifn, argv[1]);
        cout << "Enter the output file name. ";
        cin >> ofn;
        break;
      case 3:
        strcpy(ifn, argv[1]);
        strcpy(ofn, argv[2]);
        break;
      default:
        throw CommandLineException(2, argc - 1);
        break;
    }
    ifstream i(ifn); if(!i) throw FileException(ifn);
    ofstream o(ofn); if(!o) throw FileException(ofn);
 
    int testmsg;
    while (true)
    {
    if (i.eof()) break;
    i >> testmsg;
    cout << testmsg << " ";
    }
 
    o.close();
    i.close();
  }
  catch(...)
  {
    cout << "Program terminated." << endl;
    exit(EXIT_FAILURE);
  }
 
  return 0;
}

int testmsg;
    while (true)
    {
    if (i.eof()) break;
    i >> testmsg;
    cout << testmsg << " ";
    }

 while(!eof)

do
{
i >> testmsg;
cout << testmsg << endl;
}while(testmsg);

while (!i.eof)
{blah blah}

while (!eof)