File Handling

Definition:

File handling in C++ is a mechanism to create and perform read/write operations on a file.File handling is used to store data permanently in a computer. Using file handling we can store our data in secondary memory (Hard disk).

We can access various file handling methods in C++ by importing the <fstream> class.

<fstream> includes two classes for file handling:

ifstream:to read from a file.

ofstream:to create/open and write to a file.

Example 1: Opening/Closing a file

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

    int main() {

    // opening a text file for writing
    ofstream my_file("example.txt");

    // close the file
    my_file.close();

    return 0;
  }

This code will open and close the file example.txt.

Note: If there's no such file to open, ofstream my_file("example.txt"); will instead create a new file named example.txt.

Example 2: Read from a file

    #include <iostream>
    #include <fstream>
    using namespace std;         
    // open a text file for reading
    ifstream my_file("example.txt");

    // check the file for errors
    if(!my_file) {
        cout << "Error: Unable to open the file." << endl;
        return 1; 
    }

    // store the contents of the file in "line" string
    string line;

    // loop until the end of the text file
    while (!my_file.eof()) {

        // store the current line of the file
        // in the "line" variable
        getline(my_file, line);

        // print the line variable
        cout << line << endl;
    }

    // close the file
    my_file.close();

    return 0;
  }

Suppose example.txt contains the following text:

Then, our terminal will print the following output: