Symbol read twice from ifstream [duplicate]

Question

This question already has answers here:

Why is iostream::eof inside a loop condition (i.e. `while (!stream.eof())`) considered wrong? (5 answers)

Closed 8 years ago.

I found a strange behavior with std::ifstream (or more probably I'm missing something on how to properly use it). I have the following program:

#include <iostream>
#include <fstream>

int main(int argc, char** argv) {

        std::ifstream file;
        file.open(argv[1]);

        while(not file.eof()) {
                int x;
                file >> x;
                std::cout << x << std::endl;
        }

        return 0;
}

I call it on a file that contains numbers separated by spaces, like the following:

1 34 567 3

The program outputs:

1
34
567
3
3

The last number is always duplicated. I guess it's because it does not reach EOF after reading the last number, it reaches the mandatory '\n' of text files, and the next file >> x gives me again the last read number.

How can I properly detect that there is no more number to read?

Answer 1

Please try:

int x;
    while(file >> x;) {  
       std::cout << x << std::endl;
      }

For better understanding Please go through this.

Hope this will help you.