Why is the "for" cycle not creating multiple files?

Question

Why is this code not creating several files? ofstream should create a file when it encounters a file name that doesn't exist. However, for some reason, even though the names are different, it creates only one.

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

int main(void){
    ofstream fout;
    for (int a = 0; a <= 2; a++){
        string name = "test" + to_string(a) + ".txt";
        fout.open(name);
    }
    return 0;
}

Tried switching from "for" to "while" like this

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

int main(void){
    ofstream fout;
  int a = 0;
  while (a <= 2){
    string name = "test" + to_string(a) + to_string(a+1) + ".txt";
    fout.open(name);
    a++;
  }

    return 0;
}

but no result. Also I added another number (a+1) to the name and still got the same result with one created file

Remy Lebeau · Accepted Answer · 2024-09-10 21:42:42Z

3

You are opening the ofstream but not closing it. the open() method will fail if the stream is already open.

Try this:

ofstream fout;
for (int a = 0; a <= 2; a++){
    string name = "test" + to_string(a) + ".txt";
    fout.open(name);
    fout.close(); // <-- add this!
}

A better option is to simply move the ofstream object inside the loop so it is created and destroyed on each iteration:

for (int a = 0; a <= 2; a++){
    string name = "test" + to_string(a) + ".txt";
    ofstream fout(name);
}

answered Sep 10, 2024 at 21:42

Remy Lebeau

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BoP · Accepted Answer · 2024-09-10 21:25:55Z

3

You have to close the stream before you can open another one.

fout.open(name); will fail and return immediately if the stream is already open.

answered Sep 10, 2024 at 21:25

BoP

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