C++ File Handling

C++ File Handling

File handling in C++ allows programs to read from and write to files. C++ provides classes in the <fstream> library for working with files: ofstream for writing, ifstream for reading, and fstream for both reading and writing.

File Opening Modes

• Always close files after opening them to free resources.
• Use ofstream to write, ifstream to read, and fstream for both operations.
• Check if the file opened successfully using if(!file).

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• ios::out – Open file for writing (creates a new file if it doesn’t exist).
• ios::in – Open file for reading.
• ios::app – Append data to the end of the file.
• ios::binary – Open file in binary mode.

Example: Writing to a File

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

int main() {
    ofstream outFile("example.txt"); // Create and open file for writing

    if(!outFile) {
        cout << "Error opening file!" << endl;
        return 1;
    }

    outFile << "Hello, C++ File Handling!" << endl;
    outFile << "This is a second line." << endl;

    outFile.close(); // Close the file
    cout << "Data written to file successfully." << endl;

    return 0;
}

Example: Reading from a File

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

int main() {
    ifstream inFile("example.txt"); // Open file for reading

    if(!inFile) {
        cout << "Error opening file!" << endl;
        return 1;
    }

    string line;
    while(getline(inFile, line)) {
        cout << line << endl;
    }

    inFile.close(); // Close the file

    return 0;
}

Output (Reading)

Hello, C++ File Handling!
This is a second line.

Important Notes

• Always close files after opening them to free resources.
• Use ofstream to write, ifstream to read, and fstream for both operations.
• Check if the file opened successfully using if(!file).

Next Topic

Next, learn about Namespaces in C++.