Deep-dive into File Handling in C++ — covering everything from syntax to idioms, best practices, and key functions. This will be both foundational and idiomatic, aligned with writing clean, modern C++.


1. Header Required

#include <fstream>

Gives access to:


2. File Stream Classes

Class Purpose
ifstream For reading from files
ofstream For writing to files
fstream For both read and write

3. File Opening Modes (flags)

Include from <ios> (indirect via <fstream>)

Mode Meaning
ios::in Open for reading (default for ifstream)
ios::out Open for writing (default for ofstream)
ios::app Append to end
ios::ate Move to end after opening
ios::trunc Truncate existing file
ios::binary Binary mode

Combine modes using | (bitwise OR)

fstream file("data.txt", ios::in | ios::out | ios::app);

4. Common Functions