How can I count the number of files in a directory?

Question

Ryan McCombe · Accepted Answer

Counting the number of files in a directory is a common task that can be accomplished by iterating through the directory entries and incrementing a counter for each file.

Here's an example that counts regular files in a directory:

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  int file_count = 0;  // Initialize counter 
11
12  for (auto iter{start}; iter != end; ++iter) {
13    if (iter->is_regular_file()) {  
14      ++file_count;
15    }
16  }
17
18  std::cout << "Number of files: " << file_count;
19}

1Number of files: 3

Steps to Count Files:

Initialize Iterator: Create a std::filesystem::directory_iterator for the target directory.
Initialize Counter: Set a counter variable to zero.
Iterate and Count: Loop through the directory entries, incrementing the counter for each regular file.

Counting Files and Directories Separately:

You can also count files and directories separately:

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  int file_count = 0;
11  int dir_count = 0;
12
13  for (auto iter{start}; iter != end; ++iter) {
14    if (iter->is_regular_file()) {
15      ++file_count;
16    } else if (iter->is_directory()) {
17      ++dir_count;
18    }
19  }
20
21  std::cout << "Number of files: "
22    << file_count << '\n';
23  std::cout << "Number of directories: "
24    << dir_count << '\n';
25}

1Number of files: 3
2Number of directories: 1

Using Range-Based Algorithms:

You can also use range-based algorithms to count files:

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

1Number of files: 3

Counting with Recursive Iteration:

If you want to count files in a directory and its subdirectories, use std::filesystem::recursive_directory_iterator:

1#include <filesystem>
2#include <iostream>
3
4namespace fs = std::filesystem;
5
6int main() {
7  fs::recursive_directory_iterator start{
8    R"(c:\test)"};
9  fs::recursive_directory_iterator end{};
10
11  int file_count = 0;
12
13  for (auto iter{start}; iter != end; ++iter) {
14    if (iter->is_regular_file()) {
15      ++file_count;
16    }
17  }
18
19  std::cout << "Number of files: " << file_count;
20}

1Number of files: 3

Counting files is a fundamental operation that can be easily implemented using the techniques shown above, whether for flat or recursive directory structures.

Directory Iterators

Count Files in Directory

Steps to Count Files:

Counting Files and Directories Separately:

Using Range-Based Algorithms:

Counting with Recursive Iteration:

Directory Iterators

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