If file exist, work with it, if no, create it

Question

fstream datoteka;
datoteka.open(\"Informacije.txt\",  fstream::in | fstream::out | fstream::app);

if(!datoteka.is_open()){              
    ifstream datoteka(\"Inf         


        

Answer 1

datoteka.open(filename, std::fstream::in | std::fstream::out | std::fstream::app); works fine.

#include <fstream>
#include <iostream>
using namespace std;

int main(void)
{

     char filename[ ] = "Informacije.txt";
     fstream appendFileToWorkWith;

     appendFileToWorkWith.open(filename, std::fstream::in | std::fstream::out | std::fstream::app);


      // If file does not exist, Create new file
      if (!appendFileToWorkWith ) 
      {
        cout << "Cannot open file, file does not exist. Creating new file..";

        appendFileToWorkWith.open(filename,  fstream::in | fstream::out | fstream::trunc);
        appendFileToWorkWith <<"\n";
        appendFileToWorkWith.close();

       } 
      else   
      {    // use existing file
         cout<<"success "<<filename <<" found. \n";
         cout<<"\nAppending writing and working with existing file"<<"\n---\n";

         appendFileToWorkWith << "Appending writing and working with existing file"<<"\n---\n";
         appendFileToWorkWith.close();
         cout<<"\n";

    }




   return 0;
}

Answer 2

If filename does not exist, the file is created. Otherwise, the fstream::app, If file filename already exists, append the data to the file instead of overwriting it.

int writeOnfile (char* filetext) {
       ofstream myfile;
       myfile.open ("checkSellExit_file_output.csv", fstream::app);
       myfile << filetext;
       myfile.close();
       return 0;
    }