C++ File Streaming

In C++, file streaming allows you to read from and write to files using stream objects. The C++ standard library provides the <iostream> header, which includes the necessary classes and functions for file input/output operations. In this article, we will explore file streaming in C++ with examples.

1. Writing to a File

To write data to a file in C++, you can use an output file stream object, such as std::ofstream. Here's an example:

#include <iostream>
#include <fstream>

int main() {
    std::ofstream outputFile("output.txt");

    if (outputFile.is_open()) {
        outputFile << "Hello, World!" << std::endl;
        outputFile << "This is a line of text." << std::endl;

        outputFile.close();
    } else {
        std::cout << "Failed to open the file." << std::endl;
    }

    return 0;
}

In the above code, we create an output file stream object named outputFile and open a file named output.txt. We use the stream insertion operator (<<) to write data to the file. After writing, we close the file using the close() function. If the file fails to open, we output an error message.

2. Reading from a File

To read data from a file in C++, you can use an input file stream object, such as std::ifstream. Here's an example:

#include <iostream>
#include <fstream>
#include <string>

int main() {
    std::ifstream inputFile("input.txt");

    if (inputFile.is_open()) {
        std::string line;
        while (std::getline(inputFile, line)) {
            std::cout << line << std::endl;
        }

        inputFile.close();
    } else {
        std::cout << "Failed to open the file." << std::endl;
    }

    return 0;
}

In the above code, we create an input file stream object named inputFile and open a file named input.txt. We use the getline() function to read each line of the file and output it to the console. After reading, we close the file. If the file fails to open, we output an error message.

3. Appending to a File

If you want to append data to an existing file without overwriting its contents, you can use the std::ofstream object with the std::ios::app flag. Here's an example:

#include <iostream>
#include <fstream>

int main() {
    std::ofstream outputFile("data.txt", std::ios::app);

    if (outputFile.is_open()) {
        outputFile << "New data" << std::endl;

        outputFile.close();
    } else {
        std::cout << "Failed to open the file." << std::endl;
    }

    return 0;
}

In the above code, we open the file data.txt in append mode by passing the std::ios::app flag to the std::ofstream constructor. This ensures that the new data is appended to the existing content of the file instead of overwriting it. We then write the new data to the file and close it. If the file fails to open, we output an error message.

File streaming in C++ provides a convenient way to read from and write to files. Whether you need to save data to a file or retrieve data from it, file streaming allows you to handle file input/output operations efficiently in your C++ programs.