Opening an existing text file erases its contents altogether

Question

I am trying to open a text file (it has content). Every time I open it, the content of the file ends up being erased altogether, which I do not want.

#include <fstream>
#include <iostream>

using namespace std;

int main() {
    string filename;
    cout << "Enter File name : ";
    cin >> filename;
    fstream file;
    file.open(filename, fstream::out);
    file.close();
    return 0;
}

Answer 1

Instead of fstream::out which discards everything which was previously present in the file, you should use fstream::app which will not delete the contents of the file and continue writing to it from its end.

From cppreference:

Constant	Explanation
app	seek to the end of stream before each write
binary	open in binary mode
in	open for reading
out	open for writing
trunc	discard the contents of the stream when opening
ate	seek to the end of stream immediately after open
noreplace (C++23)	open in exclusive mode