How can I name the text file I create after the current date/time

Question

First of all, my knowledge of X++ is minimal, I just need to edit the code I've been given. I have a C++ program which creates a text file and stores data in it. Right now the program is using:

outfile.open("C:/Users/Admin/Documents/MATLAB/datafile.txt", std::ios::app);

But I need to change this code so each time i run this code, it will create a new file name. My suggestion is to somehow incorporate the time/date as the file name, but I am unsure how to do this. I've tried researching around, and it looks like using time_t is the way to go, but I'm unsure how to utilize it for my case.

Is it possible to save the time/date as a variable, then use:

outfile.open("C:/Users/td954/Documents/MATLAB/<DEFINED VARIABLE>", std::ios::app);
//                                            ^^^^^^^^^^^^^^^^^^

if so, how would I go about this?

Thanks guys

Answer 1

Here's code:

time_t currentTime = time(0);
tm* currentDate = localtime(&currentTime);
char filename[256] = {0};

strcpy(filename, "C:/Users/Admin/Documents/MATLAB/datafile");
strcat(filename, fmt("-%d-%d-%d@%d.%d.%d.txt",
       currentDate->tm_hour, currentDate->tm_min, currentDate->tm_sec,
       currentDate->tm_mday, currentDate->tm_mon+1,
       currentDate->tm_year+1900).c_str());

outfile.open(filename, std::ios::app);

tm* and time_t are in ctime header. fmt is just function like sprintf, which formats string. Implementation(not mine, found on stackoverflow IIRC):

#include <cstdarg>
std::string fmt(const std::string& fmt, ...) {
    int size = 200;
    std::string str;
    va_list ap;
    while (1) {
        str.resize(size);
        va_start(ap, fmt);
        int n = vsnprintf((char*)str.c_str(), size, fmt.c_str(), ap);
        va_end(ap);
        if (n > -1 && n < size) {
            str.resize(n);
            return str;
        }
        if (n > -1)
            size = n + 1;
        else
            size *= 2;
    }
    return str;
}