Code is failing to run properly after trying to read input from file

Question

I have an input file set up like this:

Hello there
1 4
Goodbye now
4.9 3

And I try to read the data as so:

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

int main(){
    ifstream input("file.txt");
    string name;
    double num1, num2;

    while(!input.eof()){
        getline(input, name);
        input >> num1;
        input >> num2;

        cout << name << endl;
        cout << num1 << " " << num2 << endl;
    }
}

But the read seems to be failing. Can anyone help me here?

Prefer "\n" to std::endl unless you have a reason to flush. — aschepler
– aschepler, Commented Dec 4, 2013 at 3:18

Community · Accepted Answer · 2017-05-23 12:13:06Z

2

Problem 1: getline with >>. Solution from this post: C++ iostream: Using cin >> var and getline(cin, var) input errors

Problem 2: inupt.eof() to test the end of loop, this post: Why is iostream::eof inside a loop condition considered wrong?

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

int main(){
  ifstream input("dat.txt");
  string name;
  double num1, num2;

  while (getline(input, name)) {  // getline fails at the end of file
    input >> num1 >> num2;
    input.ignore();
    cout << name << endl;
    cout << num1 << " " << num2 << endl;
  }
}

edited May 23, 2017 at 12:13

CommunityBot

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answered Dec 4, 2013 at 3:17

gongzhitaao

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2 Comments

Abhishek Bagchi Over a year ago

The output i get with your code for the file contents mentioned in the question is Hello there \n 1 4 \n 0 4

gongzhitaao Over a year ago

@AbhishekBagchi Interesting, I got the correct output with gcc 4.8 on Ubuntu 13.10.

Abhishek Bagchi · Accepted Answer · 2014-03-06 07:14:56Z

0

This would work..

ifstream input("command2");
string name;
double num1, num2;

int x;

while(getline(input, name)){
    input >> num1;
    input >> num2;
    input.clear();
    cout << name << endl;
    cout << num1 << " " << num2 << endl;
    string dummy;
    getline(input,dummy);
}

I write the second getline() to make sure that the \n at the line with 1 4 is read.

Without that, what i get is

Hello there
1 4

0 4
Goodbye now
4.9 3

Hope this helps.

answered Mar 6, 2014 at 7:14

Abhishek Bagchi

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