Can't write the output of a loop to a file

Question

Hello Im coding a very basic password generator and I want to write the output of the loop to a file using ofstream. My idea was each time the loop runs output one vocal from the array abc. I don't know to to make it to work and obvs. there is a better way of doing it.

#include <stdio.h>
#include <iostream>
#include <cstdlib>
#include <time.h>
#include <fstream>


using namespace std;

int main(){

    srand(time(0));

    cout << "You'r PW is: \t" << endl;
    char abc [] {'A', 'a', 'B' ,'b', 'C', 'c', 'D', 'd', 'E', 'e', 'F', 'f', 'G', 'g', 'H', 'h', 'I', 'i', 'J', 'j', 'K', 'k', 'L', 'l', 'M', 'm', 'N', 'n', 'O', 'o', 'P', 'p', 'Q', 'q', 'R', 'r', 'S', 's', 'T', 't', 'U', 'u', 'V', 'v', 'W', 'x', 'Y', 'y', 'Z', 'z'};

    for(int i = 0; i <15; i++){
        int randomNum =  rand() % 53;
        cout << abc[randomNum];
        ofstream fob;
        fob.open("contr.txt");
        fob << abc[randomNum];
    }
}

By the way, I am getting characters like ',' and '->' which isn't in my array.

There is no need to create an array of chars to generate random characters. — user3437460, Feb 10 '15 at 20:26
Add `cout << sizeof(abc) << "\n";` right under where you declare the array. Compare that number to the value you are using for mod. — Retired Ninja, Feb 10 '15 at 20:28
Also, for a better way to generate the random numbers, see [Generating random integer from a range](http://stackoverflow.com/questions/5008804/generating-random-integer-from-a-range). — Simon, Feb 10 '15 at 21:05

score 2 · Accepted Answer · answered Feb 10 '15 at 20:32

2

Have to move

ofstream fob;
fob.open("contr.txt");

out of loop. Now you rewrite file on every iteration.

answered Feb 10 '15 at 20:32

KonK

290
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8

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Indexing out of the bounds of the array is also a problem. Assuming all of the letters were in the array the number should be 52, but there are 2 letters missing. – Retired Ninja Feb 10 '15 at 20:40

score 1 · Answer 2 · answered Feb 10 '15 at 20:35

The problem here is very simple and there are two solutions to it. What your program does is create and open a new stream to a file every iteration of the loop, but by default the ofstream overwrites the files it opens so you can either move the stream opening out of the loop(the better way) or add the flag ios::app as a second argument to the stream opener in order to append the content you're outputting.

score 1 · Answer 3 · answered Feb 10 '15 at 20:46

1

Additionally, you should be using int randomNum = rand() % 52;. to choose a number in the set {0, 1, 2, ... 51}, which will be one of all the possible indexes to your array assuming you forgot to put 'X' in your array.

answered Feb 10 '15 at 20:46

Patch92

1,054
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Can't write the output of a loop to a file

3 Answers3