std::filesystem::directory_iterator

class directory_iterator;

directory_iterator is a LegacyInputIterator that iterates over the directory_entry elements of a directory (but does not visit the subdirectories). The iteration order is unspecified, except that each directory entry is visited only once. The special pathnames dot and dot-dot are skipped.

If the directory_iterator reports an error or is advanced past the last directory entry, it becomes equal to the default-constructed iterator, also known as the end iterator. Two end iterators are always equal, dereferencing or incrementing the end iterator is undefined behavior.

If a file or a directory is deleted or added to the directory tree after the directory iterator has been created, it is unspecified whether the change would be observed through the iterator.

Member types

Member functions

Non-member functions

Additionally, operator== and operator!= are (until C++20)operator== is (since C++20) provided as required by LegacyInputIterator.

It is unspecified whether operator!= is provided because it can be synthesized from operator==, and (since C++20) whether an equality operator is a member or non-member.

Helper templates

namespace std::ranges {
template<>
inline constexpr bool
    enable_borrowed_range<std::filesystem::directory_iterator> = true;
}

namespace std::ranges {
template<>
inline constexpr bool enable_view<std::filesystem::directory_iterator> = true;
}

These specializations for directory_iterator make it a borrowed_range and a view.

Notes

Many low-level OS APIs for directory traversal retrieve file attributes along with the next directory entry. The constructors and the non-const member functions of std::filesystem::directory_iterator store these attributes, if any, in the pointed-to std::filesystem::directory_entry without calling directory_entry::refresh, which makes it possible to examine the attributes of the directory entries as they are being iterated over, without making additional system calls.

Example

#include <fstream>
#include <iostream>
#include <filesystem>
#include <algorithm>
 
int main()
{
    const std::filesystem::path sandbox{"sandbox"};
    std::filesystem::create_directories(sandbox/"dir1"/"dir2");
    std::ofstream{sandbox/"file1.txt"};
    std::ofstream{sandbox/"file2.txt"};
 
    std::cout << "directory_iterator:\n";
    // directory_iterator can be iterated using a range-for loop
    for (auto const& dir_entry : std::filesystem::directory_iterator{sandbox}) 
    {
        std::cout << dir_entry.path() << '\n';
    }
 
    std::cout << "\ndirectory_iterator as a range:\n";
    // directory_iterator behaves as a range in other ways, too
    std::ranges::for_each( std::filesystem::directory_iterator{sandbox},
                           [](const auto& dir_entry) {
                             std::cout << dir_entry << '\n';
                           } );
 
    std::cout << "\nrecursive_directory_iterator:\n";
    for (auto const& dir_entry : std::filesystem::recursive_directory_iterator{sandbox}) 
    {
        std::cout << dir_entry << '\n';
    }
 
    // delete the sandbox dir and all contents within it, including subdirs
    std::filesystem::remove_all(sandbox);
}

directory_iterator:
"sandbox/file2.txt"
"sandbox/file1.txt"
"sandbox/dir1"
 
directory_iterator as a range:
"sandbox/file2.txt"
"sandbox/file1.txt"
"sandbox/dir1"
 
recursive_directory_iterator:
"sandbox/file2.txt"
"sandbox/file1.txt"
"sandbox/dir1"
"sandbox/dir1/dir2"

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also