File Handling in C++

Programming mein jab hum apna data kisi file mein store karna chahte hain ya file se read karna chahte hain, tab use hota hai File Handling. C++ hume ifstream, ofstream, aur fstream jaise classes deta hai jo file operations ko easy bana dete hain.

In this blog we'll learn about:

• File read & write karna
• File modes kya hote hain
• Text aur Binary files ka difference

1. File Handling ke liye konsi header file?

#include <fstream> // File handling ke liye
#include <iostream>
using namespace std;

2. File Write karna using ofstream

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

int main() {
    ofstream file("example.txt");  // file create ya open karega
    if (file.is_open()) {
        file << "Hello Duniya!\n";
        file << "File Handling is easy.\n";
        file.close();  // file close karna zaruri hai
        cout << "File written successfully.\n";
    } else {
        cout << "File open nahi hui.\n";
    }
    return 0;
}

ofstream is used for writing into files.

3. File Read karna using ifstream

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

int main() {
    ifstream file("example.txt");  // file read mode mein open
    string line;
    if (file.is_open()) {
        while (getline(file, line)) {
            cout << line << endl;
        }
        file.close();
    } else {
        cout << "File read nahi ho payi.\n";
    }
    return 0;
}

getline() ek line puri read karta hai jab tak newline ('\n') na mile.

4. File Modes in C++

File open karte time hume specify karna padta hai ki kaunsa mode chahiye. Kuch common file modes:

ios::in: File read mode

ios::out: File write mode

ios::app: Append at end

ios::ate: Move pointer to end immediately after opening

ios::trunc: Delete old content if file exists

ios::binary: Binary file mode

Example:

ofstream file("data.txt", ios::app);  // existing file ke end mein write karega

🔹 5. File Pointers in C++

C++ mein 2 important file pointers hote hain:

PointerPurposegetReading positionputWriting position

Hum seekg() aur seekp() ka use karke file mein specific position par jump kar sakte hain.

Example:

ifstream file("data.txt");
file.seekg(0, ios::end);  // pointer ko end par le jao
int size = file.tellg();  // file ka size return karega
cout << "File size: " << size << " bytes\n";
file.close();

6. Binary vs Text File

FeatureText FileBinary FileHuman readableHaan (Yes)Nahi (No)SizeZyadaKamExample.txt, .csv.exe, .dat, .binRead/WriteLine by lineByte by byte

Binary file write & read:

#include <fstream>
using namespace std;

int main() {
    int num = 25;

    // Write binary
    ofstream out("binary.bin", ios::binary);
    out.write((char*)&num, sizeof(num));
    out.close();

    // Read binary
    int readNum;
    ifstream in("binary.bin", ios::binary);
    in.read((char*)&readNum, sizeof(readNum));
    in.close();

    cout << "Read from binary: " << readNum << endl;
    return 0;
}