Appending a new line in a file(log file) in c++

Question

I have a logging functionality and in this I have got log files. Now every time I run the program I want that previously written file should not get deleted and should be ap

Answer 1

You want to open the file in "append" mode, so it doesn't delete the previous contents of the file. You do that by specifying ios_base::app when you open the file:

std::ofstream log("logfile.txt", std::ios_base::app | std::ios_base::out);

For example, each time you run this, it will add one more line to the file:

#include 
#include 

int main(){
    std::ofstream log("logfile.txt", std::ios_base::app | std::ios_base::out);

    log << "line\n";
    return 0;
}

So, the first time you run it, you get

line

The second time:

line
line

and so on.