Table of Contents
Key Features of std::filesystem
Common Use Cases and Examples
Check if a File Exists
List Files in a Directory
Create and Remove Directories
Handling Paths Correctly
Things to Watch Out For
Home Backend Development C++ What is std::filesystem in C 17?

What is std::filesystem in C 17?

Jul 14, 2025 am 12:39 AM
C++17

std::filesystem in C 17 is a standard library module for cross-platform file system operations. It provides core components such as path, file_status, directory_entry, etc., and supports functions such as checking file existence, traversing directories, creating and deleting directories and processing paths. 1. It replaces the previous practice of relying on platform API or third-party libraries; 2. It supports common operations such as exists(), create_directory(), directory_iterator, etc.; 3. Automatically handle path format differences in different systems; 4. Pay attention to exception handling, platform differences and performance issues when using it.

What is std::filesystem in C 17?

std::filesystem in C 17 is a standard library module that provides a set of classes and functions for manipulating files, directories, and paths in a portable way. Before C 17, developers often relied on platform-specific APIs or third-party libraries like Boost to handle file system operations. Now, with std::filesystem , you can write code that works across different operating systems without needing external dependencies.

What is std::filesystem in C 17?

Key Features of std::filesystem

The main components of std::filesystem include:

What is std::filesystem in C 17?
  • path : Represents a filesystem path (file or directory), handling string conversations, concatenation, and more.
  • file_status : Holds information about a file's type and permissions.
  • directory_entry : Represents an entry in a directory.
  • directory_iterator : Iterates through the contents of a directory.
  • recursive_directory_iterator : Traverses directories recursively.
  • Functions for checking file existence ( exists() ), copying files ( copy_file() ), creating directories ( create_directory() ), getting file size ( file_size() ), and more.

These tools make it easier to work with files and folders without relying on OS-specific calls.


Common Use Cases and Examples

Here are some everyday tasks you can do with std::filesystem .

What is std::filesystem in C 17?

Check if a File Exists

This is one of the most basic but essential operations:

 #include <filesystem>
namespace fs = std::filesystem;

if (fs::exists("example.txt")) {
    std::cout << "File exists\n";
}

You can also check if it's a regular file or a directory using is_regular_file() or is_directory() .

List Files in a Directory

Use directory_iterator to loop through files:

 for (const auto& entry : fs::directory_iterator(".")) {
    std::cout << entry.path() << "\n";
}

This prints all files and folders in the current working directory.

If you need to go into subdirectories too, just replace directory_iterator with recursive_directory_iterator .

Create and Remove Directories

Creating a directory is straightforward:

 fs::create_directory("new_folder");

And removing one:

 fs::remove_all("new_folder"); // Removes even if not empty

Note: remove() deletes only empty directories. For non-empty ones, use remove_all() .


Handling Paths Correctly

One of the biggest advantages of std::filesystem is how it handles paths consistently across platforms. You don't have to worry about backslashes vs. forward slashes — it takes care of that under the hood.

For example:

 fs::path p = "data" / "images" / "logo.png";
std::cout << p; // Outputs "data/images/logo.png" on Linux/macOS, "data\images\logo.png" on Windows

You can also extract parts of a path easily:

  • p.parent_path() returns "data/images"
  • p.filename() gives "logo.png"
  • p.extension() gives ".png"

This makes building and parsing paths much cleaner than using string manipulation.


Things to Watch Out For

While std::filesystem is powerful, there are a few gotchas:

  • It may throw exceptions by default. If you don't want that, pass an error code object as the last argument to many functions.
  • Not all operating systems support every feature — for example, certain permission-related functions behave differently on Windows and Unix-like systems.
  • Performance can be an issue when iterating large directories or deeply nested structures.

So always test your code on target platforms and consider wrapping filesystem calls in try-catch blocks unless you're sure they won't fail.


That's the core of what you need to know about std::filesystem . It's not overly complicated, but it does take some time to get used to the types and methods. Once you're familiar with them, though, it becomes a solid part of your C toolkit for file management.

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