Help please, code execution outputs instead of
123456 just
456 Why the file is cleared before writing? Trunc not set
#include "stdafx.h" #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ofstream a{ "1.txt",ios_base::ate }; a << "123"; a.close(); ofstream b{ "1.txt",ios_base::ate }; b << "456"; b.close(); ifstream c{ "1.txt" }; string str; c >> str; cout << str; return 0; } You need to use app in your second writer to append the content to the file instead of rewritting it, as follows:
#include "stdafx.h" #include <iostream> #include <fstream> #include <string> using namespace std; int main() { ofstream a{ "1.txt",ios_base::ate }; a << "123"; a.close(); ofstream b{ "1.txt",ios_base::app }; //notice here is app instead of ate b << "456"; b.close(); ifstream c{ "1.txt" }; string str; c >> str; cout << str; return 0; } As in this question :
std::ios_base::ate does NOT imply std::ios_base::app
So if you use ate it does not mean that it will append the content to the file.
You can find the different between ios_base:ate and ios_base:app here
For your code, you can change it like this:
ofstream b {"1.txt", ios_base:app}; 