Inserting dot after 2 chars till the end of file in C++ - c++

Question

Good day, everyone
I would like to insert a dot (or any other char), after specified amount chars read (in my case it's 2)
So here is my code:
#include <fstream>
#include <string>
using namespace std;
string dot = "."; //Char to insert
char ch;
unsigned i=0; //Symbol counter
int counter = 2; //How much letters to skip before insertion
int main(){
fstream fin("file.txt", fstream::in);
while (fin >> noskipws >> ch) {
ofstream file;
file.open ("file2.txt");
file << ch;
file.close();
i++;
if(i == counter){
file.open ("file2.txt");
file << dot;
file.close();
i = 0;
}
}
return 0;
}
What i have written in my new file2.txt is "0".
P.S. I'm quite new in C++ so please explain in depth as for newbie (if you have time)
Thank you in advance.
EDIT: After applying few fixes output is now "."
EDIT2: It doesn't allow me to answer to my self post (because I'm newbie in this forum and have to wait 7h before answering), I'm going to post my fixed code here
Fixed version:
#include <fstream>
#include <string>
using namespace std;
string dot = "."; //Char to insert
char ch;
unsigned i = 0; //Symbol counter
int counter = 2; //How much letters to skip before insertion
int main(){
ofstream file;
file.open ("file2.txt");
fstream fin("file.txt", fstream::in);
while (fin >> noskipws >> ch) {
file << ch;
i++;
if(i == counter){
file << dot;
i = 0;
}
}
file.close();
fin.close();
return 0;
}
Thank you everyone for replies.

Answer 1

For a simple application like this, open the output file before you start reading, and don't close it until you're done. As written, the output file gets opened every time a character is read and then overwrites whatever was in the file before. You could open the file in append mode to stick new data on the end, but it's much simpler (and faster) to just keep it open.

Answer 2

Each time you write something to your output file, you open it, write your output, then close it. Because of the way you are opening your file, each of your writes start at the beginning of the file.
If instead, you leave your output file open until you are finished writing all your data, then next write will continue at the point the previous write ended, producing the sequence of output you are expecting.
ofstream file;
file.open("file2.txt");
while (fin >> noskipws >> ch) {
file << ch;
i++;
if (i == counter) {
file << dot;
i = 0;
}
}

Answer 3

Just open file in beginning , updated it and finally close all files.
ofstream file; <------------+
file.open ("file2.txt"); |
|
while (fin >> noskipws >> ch) { |
|
//ofstream file; ---+ |
+----->------+
//file.open ("file2.txt"); ---+
file << ch;
//file.close();
i++;
if(i == counter){
//file.open ("file2.txt");
file << dot;
//file.close();
i=0;
}
}
//Close files
file.close();
fin.close() ;

Answer 4

When you write to a file in a loop, you most likely want to to open the file outside of the loop. Normally when you open a file for writing, the old content will be overwritten.
So do this:
ofstream file ("file2.txt")
while (...)
{
...
file << ....
...
}