NAME¶

std::filesystem::directory_iterator - std::filesystem::directory_iterator

Synopsis¶

Defined in header <filesystem>
class directory_iterator; (since C++17)

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 type Definition
value_type std::filesystem::directory_entry
difference_type std::ptrdiff_t
pointer const std::filesystem::directory_entry*
reference const std::filesystem::directory_entry&
iterator_category std::input_iterator_tag

Member functions¶

constructor constructs a directory iterator
(public member function)
destructor default destructor
(public member function)
operator= assigns contents
(public member function)
operator* accesses the pointed-to entry
operator-> (public member function)
increment advances to the next entry
operator++ (public member function)

Non-member functions¶

begin(std::filesystem::directory_iterator) range-based for loop support
end(std::filesystem::directory_iterator) (function)
(C++17)

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<> (since
inline constexpr bool C++20)
enable_borrowed_range<std::filesystem::directory_iterator> = true;

}
namespace std::ranges {

template<> (since
inline constexpr bool enable_view<std::filesystem::directory_iterator> = C++20)
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¶

// Run this code

#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);
}

Possible output:¶

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.

DR Applied to Behavior as published Correct behavior
LWG 3480 C++20 directory_iterator was neither a borrowed_range it is both
nor a view

See also¶

recursive_directory_iterator an iterator to the contents of a directory and its
(C++17) subdirectories
(class)
directory_options options for iterating directory contents
(C++17) (enum)
directory_entry a directory entry
(C++17) (class)