sumFromFile.cpp

#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <string>
using namespace std;

int main(const int argc, const char* argv[])
{
   if (argc != 2)
   {
      cerr << "Usage: ./sumFromFile fileName\n";
      exit(1);
   }

   ifstream inStream(argv[1]);
   string line;
   int sum = 0;
   while (getline(inStream, line))
   {
      sum += atoi(line.c_str());
   }
   cerr << "Sum: " << sum << endl;
   inStream.close();
}