std::filesystem::directory_iterator

 

C++

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Technical specifications

Symbols index

External libraries

 

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator      filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

std::filesystem::directory_iterator

Member functions

directory_iterator::directory_iterator

directory_iterator::operator*directory_iterator::operator->

directory_iterator::operator=

incrementoperator++

Non-member functions

begin(std::filesystem::directory_iterator)end(std::filesystem::directory_iterator)

 

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*operator->	accesses the pointed-to entry (public member function)
incrementoperator++	advances to the next entry (public member function)

Non-member functions

begin(std::filesystem::directory_iterator)end(std::filesystem::directory_iterator) (C++17)

range-based for loop support (function)

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 specializations

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

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 <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>
 
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 nor a view	it is both

See also

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