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.
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.
Key Features of std::filesystem
The main components of std::filesystem include:
- 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 .
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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