How do I filter the directory entries to only show files?

Question

Ryan McCombe · Accepted Answer

Filtering directory entries to show only files can be achieved using a combination of std::filesystem::directory_iterator and conditional checks within the iteration loop. Here's an example:

1#include <filesystem>
2#include <iostream>
3
4namespace fs = std::filesystem;
5
6int main() {
7  fs::directory_iterator start{R"(c:\test)"};
8  fs::directory_iterator end{};
9
10  for (auto iter{start}; iter != end; ++iter) {
11    if (iter->is_regular_file()) {  
12      std::cout << iter->path().string() << '\n';
13    }
14  }
15}

1c:\test\file.txt
2c:\test\hello.txt
3c:\test\document.pdf

Steps to Filter Entries:

Initialize the Iterator: Create a std::filesystem::directory_iterator pointing to the target directory.
Iterate with a Condition: Within the loop, use is_regular_file() to check if the current entry is a file.
Output or Process Files: If the condition is true, process the file (e.g., print its path).

Alternative Approach Using `std::ranges`:

You can also use std::ranges::filter() to streamline the process:

1#include <filesystem>
2#include <iostream>
3#include <ranges>
4
5namespace fs = std::filesystem;
6
7int main() {
8  auto entries = std::ranges::subrange{
9    fs::directory_iterator{R"(c:\test)"},
10    fs::directory_iterator{}};
11
12  auto files = entries | std::views::filter(
13    [](const fs::directory_entry& entry) {
14      return entry.is_regular_file();
15    }
16  );
17
18  for (const auto& file : files) {
19    std::cout << file.path().string() << '\n';
20  }
21}

1c:\test\file1.txt
2c:\test\file2.txt
3c:\test\file3.txt

This approach leverages the power of ranges to filter the entries in a more declarative manner. Both methods are effective for filtering directory entries to show only files.

Directory Iterators

Filter Directory Entries

Steps to Filter Entries:

Alternative Approach Using `std::ranges`:

Directory Iterators

Professional C++

Questions & Answers

Filter Directory Entries

Steps to Filter Entries:

Alternative Approach Using std::ranges:

Directory Iterators

Questions & Answers

Alternative Approach Using `std::ranges`: