File I/O with std::ifstream and std::ofstream

Intermediate13 min read•Updated: 2026-10-22

📁 File I/O with std::ifstream and std::ofstream

Introduction

Persistent data storage requires reading and writing files on disk. The <fstream> header provides stream classes for files:

std::ofstream: Output file stream (for writing to disk).
std::ifstream: Input file stream (for reading from disk).
std::fstream: Bidirectional stream (read and write).

💾 Writing to a Text File

1#include <iostream>
2#include <fstream>
3#include <string>
4 
5int main() {
6    // std::ios::app appends to existing file; default without it truncates/overwrites
7    std::ofstream outFile("students.txt", std::ios::out);
8 
9    if (!outFile.is_open()) {
10        std::cerr << "[ERROR]: Failed to create/open students.txt\n";
11        return 1;
12    }
13 
14    outFile << "101,Aarav Sharma,Modern C++\n";
15    outFile << "102,Sneha Gupta,Java Development\n";
16    outFile << "103,Vikram Singh,Python Advanced\n";
17 
18    outFile.close(); // Explicit close (also closed automatically in destructor)
19    std::cout << "Data saved to students.txt successfully!\n";
20    return 0;
21}

📖 Reading from a Text File Line-by-Line

1#include <iostream>
2#include <fstream>
3#include <string>
4 
5int main() {
6    std::ifstream inFile("students.txt");
7 
8    if (!inFile.is_open()) {
9        std::cerr << "[ERROR]: File not found or inaccessible!\n";
10        return 1;
11    }
12 
13    std::string line;
14    int lineCounter = 1;
15 
16    std::cout << "=== Reading students.txt ===\n";
17    while (std::getline(inFile, line)) {
18        std::cout << "Line " << lineCounter++ << ": " << line << "\n";
19    }
20 
21    return 0;
22}

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Reading/Writing Binary Files with read() and write()

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Standard Exception Hierarchy (std::exception, std::runtime_error)	Reading/Writing Binary Files with read() and write()

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Reading/Writing Binary Files with read() and write()

File I/O with std::ifstream and std::ofstream

Intermediate13 min read•Updated: 2026-10-22

Study Materials

📁 File I/O with std::ifstream and std::ofstream

Introduction

Persistent data storage requires reading and writing files on disk. The <fstream> header provides stream classes for files:

std::ofstream: Output file stream (for writing to disk).
std::ifstream: Input file stream (for reading from disk).
std::fstream: Bidirectional stream (read and write).

💾 Writing to a Text File

1#include <iostream>
2#include <fstream>
3#include <string>
4 
5int main() {
6    // std::ios::app appends to existing file; default without it truncates/overwrites
7    std::ofstream outFile("students.txt", std::ios::out);
8 
9    if (!outFile.is_open()) {
10        std::cerr << "[ERROR]: Failed to create/open students.txt\n";
11        return 1;
12    }
13 
14    outFile << "101,Aarav Sharma,Modern C++\n";
15    outFile << "102,Sneha Gupta,Java Development\n";
16    outFile << "103,Vikram Singh,Python Advanced\n";
17 
18    outFile.close(); // Explicit close (also closed automatically in destructor)
19    std::cout << "Data saved to students.txt successfully!\n";
20    return 0;
21}

📖 Reading from a Text File Line-by-Line

1#include <iostream>
2#include <fstream>
3#include <string>
4 
5int main() {
6    std::ifstream inFile("students.txt");
7 
8    if (!inFile.is_open()) {
9        std::cerr << "[ERROR]: File not found or inaccessible!\n";
10        return 1;
11    }
12 
13    std::string line;
14    int lineCounter = 1;
15 
16    std::cout << "=== Reading students.txt ===\n";
17    while (std::getline(inFile, line)) {
18        std::cout << "Line " << lineCounter++ << ": " << line << "\n";
19    }
20 
21    return 0;
22}

Next Lesson

Reading/Writing Binary Files with read() and write()

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Standard Exception Hierarchy (std::exception, std::runtime_error)	Reading/Writing Binary Files with read() and write()

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next