Question

I am working on a small program that takes a input file and processors the data in the file. With my current code (see below) when you enter a valid file name it just freezes the command line (drops down a line and just shows a flashing _ ) and I have to kill the program to get out. If you enter a invalid file name the if(!file) gets called and runs fine.
Whats really odd is that if I put a debugging cout above that if statement it will not get called if the file name is correct. Hope you can help and if you need more info let me know!

This is my current code:

using namespace std;
#include <iostream>
#include <stdexcept>
#include <string>
#include <fstream>
#include <vector>
#include <cctype>
#include "Student.h"

int main(){
    string filename, name;
    char *inputfile;
    ifstream file;
    vector<Student> students;
    const int SIZE = 200;
    char buffer [SIZE];
    int regno, i;

    cout << "Enter file name: ";
    cin >> filename;
    inputfile = const_cast<char*> (filename.c_str());
    file.open(inputfile);
    if (!file){
        cout << "Failed to open " << filename << endl;
        exit(1);
    }
    while (!file.eof()){
        file.getline(buffer, SIZE);
        i = 0;
        regno = 0;
        while (isdigit(buffer[i])){
            regno = (regno*10)+buffer[i];
        }
        cout << regno;
    }
    file.close();

}

Answer 1

Your problems is that you never increase i in the cycle.

Here:

    i = 0;
    regno = 0;
    while (isdigit(buffer[i])){
        regno = (regno*10)+buffer[i];
    }

You go into infinite cycle as i always stays 0.

Also why do you do the const_cast? You can open using a const char * too. So you can write this:

cin >> filename;
file.open(filename.c_str());

And code will still work.