How to Open and Close a File in C++?

In C++, we can open a file to perform read and write operations and close it when we are done. This is done with the help of fstream objects that create a stream to the file for input and output. In this article, we will learn how to open and close a file in C++.

Open and Close a File in C++

The fstream class contains the std::fstream::open() function that can be used to open files in different modes.

Syntax of fstream::open()

fstream_object.open(filename, mode);

The modes can be of three types:

• std::ios::in: This mode is used to open a file for reading only.
• std::ios::out: This mode is used to open a file for writing. If there is already content in the file then it will be overwritten in this mode.
• std::ios::app: This mode is called the append mode in which we open a file for writing at the end of the file.

We can close the file using std::fstream::close() function.

Algorithm

1. We will first create an fstream object.
2. Then we open the file using open() function in write mode(ios::out)
2. We then write some data to the file.
3. At the end, we close the file using close() function

C++ Program to Open and Close a File

// C++ program to demonstrate how to open and close a file
#include <fstream>
#include <iostream>

using namespace std;

int main()
{
    //  create and ofstream object and open the file in
    //  append mode
    ofstream fio("abc.txt", ios::app);

    // Check if the file is opened successfully
    if (fio.is_open()) {

        cout << "File opened successfully." << endl;

        // Append content to the file
        fio << "This text is appended to the file." << endl;

        // Close the file
        fio.close();

        cout << "File closed." << endl;
    }
    else {
        // Display error if file was not opened
        cout << "Error opening file!" << endl;
    }

    return 0;
}

File opened successfully.
File closed.