basic c++ read file

read-and-sum.cpp

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

int main(int argc, char const *argv[]) {
  if (argc < 2) {
    cout << "Usage: "  << argv[0] << " filename.txt" << endl;
    return 0;
  }

  ifstream fs(argv[1]);
  string line;
  int sum = 0;
  if (fs.is_open()) {
    while (getline(fs, line)) {
      try {
        int x = stoi(line);
        sum += x;
      } catch(exception& e) {
        cout << "\"" << line << "\" parse failed."  << endl;
        cout << "in function " << e.what() << endl;
        return 0;
      }
    }
    cout << "sum: " << sum << endl;
  } else {
    cout << "open file " << argv[1] << " failed." << endl;
  }

  return 0;
}