Overwriting an Existing Directory

When you try to create a directory that already exists using std::filesystem::create_directory(), the function will return false. It does not throw an exception in this case.

However, if you use std::filesystem::create_directories(), it will create the entire directory path if any part of it does not exist and will not throw an error if the directory already exists.

Here's an example to illustrate this behavior:

1#include <filesystem>
2#include <iostream>
3namespace fs = std::filesystem;
4
5int main() {
6  fs::path dir_path{R"(c:\test)"};  
7  try {
8    bool created = fs::create_directory(dir_path);
9    if (created) {
10      std::cout << "Directory created";  
11    } else {
12      std::cout << "Directory already exists";  
13    }
14  } catch (fs::filesystem_error &e) {
15    std::cerr << e.what() << '\n';
16  }
17}

1Directory already exists

In this example:

• We define dir_path as the path to the directory we want to create.
• We call std::filesystem::create_directory() and check its return value.
• If the directory already exists, create_directory() returns false, and we print "Directory already exists."

To handle scenarios where you might need to create a nested directory structure, you can use std::filesystem::create_directories():

1#include <filesystem>
2#include <iostream>
3
4namespace fs = std::filesystem;
5
6int main() {
7  fs::path nested_dir_path{R"(c:\test\subdir)"};  
8  try {
9    bool created =
10      fs::create_directories(nested_dir_path);
11    if (created) {
12      std::cout << "Directories created";  
13    } else {
14      std::cout << "Directories already exist";  
15    }
16  } catch (fs::filesystem_error &e) {
17    std::cerr << e.what();
18  }
19}

1Directories already exist

In this case:

• std::filesystem::create_directories() creates all necessary parent directories if they do not exist.
• If the directory structure already exists, it simply returns false without throwing an exception.

Using std::filesystem::create_directories() is particularly useful when you want to ensure the entire path exists without worrying about whether each individual directory exists.

Both functions handle errors gracefully, so you should always wrap these calls in a try block and catch any std::filesystem::filesystem_error exceptions to handle other potential issues, such as permission errors or invalid paths.

Overwriting an Existing Directory

If you want to overwrite an existing directory, you will need to delete the existing directory and then create a new one. Here's how you can do it:

1#include <filesystem>
2#include <iostream>
3
4namespace fs = std::filesystem;
5
6int main() {
7  fs::path dir_path{R"(c:\test)"};
8  try {
9    if (fs::exists(dir_path)) {
10      fs::remove_all(dir_path);
11      std::cout << "Existing directory removed\n"; 
12    }
13    fs::create_directory(dir_path);  
14    std::cout << "Directory created";
15  } catch (fs::filesystem_error &e) {
16    std::cerr << e.what();
17  }
18}

1Existing directory removed
2Directory created

In this example:

• We check if the directory exists using std::filesystem::exists().
• If it exists, we remove it and all its contents using std::filesystem::remove_all().
• After removing the existing directory, we create a new one using std::filesystem::create_directory().

Using std::filesystem::remove_all() ensures that the existing directory and all its contents are deleted, allowing you to create a fresh directory in its place. Always be cautious with this approach, as it will permanently delete all files and subdirectories within the specified directory.

This method provides a clear way to overwrite an existing directory by first removing it and then creating a new one.