File Handling

There are three classes included in C++ to work with files:

ofstream - creates and writes to files
ifstream - reads from files
fstream - a combination of ofstream and ifstream (can create, read, and write).

To write to a file, first we need to include the library <fstream>, then we open the file with ofstream class or fstream class. Then we use the insertion operator (<<) to write and finally, we close the file.

Syntax: fprintf(pointer_name, "text we want to write");

Example:


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

    int main() {
      // Create and open a text file
      ofstream MyFile("filename.txt");

      // Write to the file
      MyFile << "Hello!";

      // Close the file
      MyFile.close();
    }

We can also append to a file using ofstream. But, we need to include the mode std::ios::app in the open() function.

Syntax: variable_name.open(file_name, std::ios::app);

Example:


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

    int main() {
      // Declaring a variable 
      ofstream myfile;

      // Open and append "Hello!" the file 
      myfile.open("text.txt", ios::app)
      myfile << "Hello!"

      // Close the file
      myfile.close();

      return 0;
    }

To read a file, first we need to include the library <fstream>, then we open the file with ifstream class or fstream class. We need to prepare a text string variable to store the file content. Then, we use the getline() function and finally, we close the file.
Note: getline() function only read a single line of text, so if you want to read several line of text, use loops to loop through the getline() function.

Example:


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

    int main() {
        //Create a variable string
        string mytext;
        
        // Read from the text file
        ifstream MyFile("filename.txt");

        // Read the file using getline() function
        getline(MyFile, mytext);
        cout << mytext;

        // Close the file
        MyFile.close();
    }

fstream can do both what ifstream and ofstream does. Example:


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

    int main() {
        // Create and open a text file
        fstream MyFile("filename.txt");

        // Write to the file
        MyFile << "Hello!";

        // Close the file
        MyFile.close();
    }


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

    int main() {
        //Create a variable string
        string mytext;
        
        // Read from the text file
        fstream MyFile("filename.txt");

        // Read the file using getline() function
        getline(MyFile, mytext);
        cout << mytext;

        // Close the file
        MyFile.close();
    }

Navigation Bar

File Handling

Table of Contents

ofstream (Create and Write to a File)

ifstream (Read a File)

fstream