Check out example codes for "c++ stream string into fiel". It will help you in understanding the concepts better.

Code Example 1

#include <fstream>
#include <string>
#include <iostream>

int main()
{
    std::string input;
    std::cin >> input;
    std::ofstream out("output.txt");
    out << input;
    out.close();
    return 0;
}

Code Example 2

string filetostring(){
	ifstream file("file", ios::binary);
    string fileStr;

    istreambuf_iterator<char> inputIt(file), emptyInputIt;
    back_insert_iterator<string> stringInsert(fileStr);

    copy(inputIt, emptyInputIt, stringInsert);

    return fileStr;
}

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