// Example:  Write a program that sums the 2nd column of a file with 3 columns of numbers

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>
using namespace std;

int sumOf2ndColumnInFile(const string& filename);

int main()
{
    cout << sumOf2ndColumnInFile("numbers1.txt") << endl;
    cout << sumOf2ndColumnInFile("numbers2.txt") << endl;

    return 0;
}

int sumOf2ndColumnInFile(const string& filename)
{
    ifstream fin(filename.c_str());
    int sum = 0, number, dummy;
    if (!fin)
    {
        cerr << "Can't open " << filename << endl;
        exit(1);
    }
    while (!fin.eof())
    {
        fin >> dummy >> number >> dummy;
        sum += number;
    }
    return sum;
}

*****  OUTPUT  *****

23
15

Input Files

numbers1.txt

1   2   3    4   5   6    7   8   9

numbers2.txt

1   2   3    4   5   6    7   8   9