18 Jul C++ File Handling

To read and write to a file in C+, use the fstream library. The <iostream> and <fstream> header files are used to work on the fstream. With that, the following are the classes of the fstream to work on files in C++:

Create a File

To create a file in C++, include the following header files:

#include <iostream>
#include <fstream>

The following code snippet displays how to create a file myfile.txt:

ofstream DemoFile("E:\Amit\myfile.txt");

The file myfile.txt gets created at the location. The file is empty since we did not add any text to it:

Now, let us see how to create and write a file. We will continue the above example.

Create and Write to a File

To create and write a file in C++, include the following header files as we saw above:

#include <iostream>
#include <fstream>

To write, use the insertion operator i.e., << as shown below:

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

int main() {
    // Create a File
    ofstream DemoFile("E:\Amit\myfile.txt");
    
    // Write to the File
    DemoFile << "This is a demo text written to a file";

   // Close the File
    DemoFile.close()
}

The myfile.txt file is now having the following text as shown below:

Always remember to close an opened file using the close() method.

Read a File

To read a file in C++, use the fstream or ifstream class. Always remember to close an opened file using the close() method.

We will read the above myfile.txt with the following text:

Let us now see the example to read the above file i.e., myfile.txt that already exists:

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

int main () {
    // Create a File
    ofstream DemoFile("E:\Amit\myfile.txt");
    
    // Write to the File
    DemoFile << "This is a demo text written to a file";
 
   // Close the File
    DemoFile.close()

   // Create a string
   string str;

   // Read the file
   ifstream DemoFile("E:\Amit\myfile.txt");

   // Read the file linne by line
   while (getline (DemoFile, str)) {
     // Display the text from myfile.txt
     cout << str;
   }

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

Output

This is a demo text written to a file.