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("Informacije.txt")
    datoteka.open("my_file.txt", fstream::in | fstream::out | fstream::app);
}/*I'm writing IN the file outside of that if statement.

So what it should do is create a file if it was not created before, and if it is created write into that file.

Hello there, so what I wanted from my program is that it check if the file already exists, sothe program open if it does and I can write in it, if the file is not opened(have not been created before) the program create it. So the problem is when I create a .csv file, and finish writing and I wanted to check if the written is really there, the file cannot be opened. In .txt file, everything is blank.

See related question stackoverflow.com/questions/12774207/…. — Mihai8
– Mihai8, Commented May 31, 2014 at 7:44
When you're done with the datoteka in the if-block the file is closed. The original outside the if-block was never opened, so anything you're do to that doesn't actually "do" anything. (I can only imagine the unchecked IO you didn't post) What is the point of the datoteka in the if-block anyway? — WhozCraig
– WhozCraig, Commented May 31, 2014 at 7:53

Software_Designer · Accepted Answer · 2014-05-31 08:30:56Z

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;
}

user9385340 · Accepted Answer · 2020-03-05 10:53:05Z

7

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;
    }

answered Mar 5, 2020 at 10:53

user9385340

Collectives™ on Stack Overflow

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

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related