C++ Library - <filesystem>

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The <filesystem> header in C++, provides a set of functions for performing operations on the file system, such as manipulating paths, copying or deleting files and checking file status.

The <filesystem> library may be unavailable if a hierarchical file system is not accessible to the implementation, or if it does not provide the necessary capabilities. Some features may not be available if they are not supported by the underlying file system, such as FAT(File Allocation Table).

Including <filesystem> Header

To include the <filesystem> header in your C++ program, you can use the following syntax.

#include <filesystem>

Functions of <filesystem> Header

Below is list of all functions from <filesystem> header.

Path Manipulation Functions

This path manipulation functions operate on file paths to compose, convert or resolve them.

S.No Functions & Description
1 absolute

This function composes an absolute path based on a given relative or absolute path.
2 canonical & weakly_canonical

These functions convert a path to its canonical form by by resolving all symbolic links and relative paths.
3 relative, proximate

These functions composes a relative path from one path to another.
4 copy

This function copies files or directories.
5 copy_file

This function copies the contents of a single file.
6 copy_symlink

This function copies a symbolic link.
7 create_directory, create_directories

These functions creates single/multiple new directory.
8 create_hard_link

This function creates a hard link, allowing a single file to have multiple directory entries.
9 create_symlink, create_directory_symlink

These functions creates a symbolic link for a file.
10 current_path

This function returns or sets the current working directory.
11 exists

This function checks whether path refers to existing file system object.
12 equivalent

This function checks whether two paths refer to the same file system object.
13 file_size

This function returns the size of a file.
14 hard_link_count

This function returns the number of hard links referring to the specific file.
15 last_write_time

This function gets or sets the time of the last data modification.
16 permissions

This function modifies file access permissions.
17 read_symlink

This function obtains the target of a symbolic link.
18 remove

This function removes a file or empty directory.
19 remove_all

This function removes a file or removes a file or directory and all its contents, recursively.
20 rename

This function moves or renames a file or directory.
21 resize_file

This function changes the size of a regular file by truncation or zero-fill.
22 space

This function determines available free space on the file system.

Path Manipulation Example

In the following example we are going to use, exists() checking whether the specified path (filePath) refers to an existing file system object.

#include <iostream>
#include <filesystem>
int main() {
    std::filesystem::path filePath{"example.txt"};

    if (std::filesystem::exists(filePath)) {
        std::cout << "The file exists." << std::endl;
    } else {
        std::cout << "The file does not exist." << std::endl;
    }
    return 0;
}

Output

If we run the above code it will generate the following output 

The file does not exist.

File types

The <filesystem> library provides several functions that determine the type of file or directory specified by a path. These functions are used for understanding the characteristics of files and implementing logic based on file types.

S.No Functions & Description
1 is_block_file

This function checks whether the given path refers to block device.
2 is_character_file

This function checks whether the given path refers to a character device.
3 is_directory

This function checks whether the given path refers to a directory.
4 is_empty

This function checks whether the given path refers to an empty file or directory.
5 is_fifo

This function checks whether the given path refers to a named pipe.
6 is_other

This function checks whether the argument refers to an other file.
7 is_regular_file

This function checks whether the argument refers to a regular file.
8 is_socket

This function checks whether the argument refers to a named IPC socket.
9 is_symlink

This function checks whether the argument refers to a symbolic link.
10 status_known

This function checks whether file status is known.

Checking the Specified Path

In the following example we are going to use, is_directory to check if the specified path (dirPath) refers to a directory.

#include <iostream>
#include <filesystem>
int main() {
    std::filesystem::path dirPath{"my_directory"};

    if (std::filesystem::is_directory(dirPath)) {
        std::cout << "This path refers to a directory." << std::endl;
    } else {
        std::cout << "This path does not refer to a directory." << std::endl;
    }
    return 0;
}

Output

If we run the above code it will generate the following output 

This path does not refer to a directory.
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