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std::filesystem::recursive_directory_iterator

From cppreference.com
 
 
 
 
Defined in header <filesystem>
class recursive_directory_iterator;
(since C++17)

recursive_directory_iterator is a LegacyInputIterator that iterates over the directory_entry elements of a directory, and, recursively, over the entries of all subdirectories. The iteration order is unspecified, except that each directory entry is visited only once.

By default, symlinks are not followed, but this can be enabled by specifying the directory option follow_directory_symlink at construction time.

The special pathnames dot and dot-dot are skipped.

If the recursive_directory_iterator reports an error or is advanced past the last directory entry of the top-level directory, 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 recursive directory iterator has been created, it is unspecified whether the change would be observed through the iterator.

If the directory structure contains cycles, the end iterator may be unreachable.

Contents

[edit] 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

[edit] Member functions

constructs a recursive directory iterator
(public member function) [edit]
(destructor)
default destructor
(public member function) [edit]
Observers
accesses the pointed-to entry
(public member function) [edit]
returns the currently active options that affect the iteration
(public member function) [edit]
returns the current recursion depth
(public member function) [edit]
checks whether the recursion is disabled for the current directory
(public member function) [edit]
Modifiers
assigns contents
(public member function) [edit]
advances to the next entry
(public member function) [edit]
moves the iterator one level up in the directory hierarchy
(public member function) [edit]
disables recursion until the next increment
(public member function) [edit]

[edit] Non-member functions

range-based for loop support
(function) [edit]

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.

[edit] Helper templates

namespace std::ranges {

template<>
inline constexpr bool
    enable_borrowed_range<std::filesystem::recursive_directory_iterator> = true;

}
(since C++20)
namespace std::ranges {

template<>
inline constexpr bool
    enable_view<std::filesystem::recursive_directory_iterator> = true;

}
(since C++20)

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

[edit] Notes

A recursive_directory_iterator typically holds a reference-counted pointer (to satisfy shallow-copy semantics of LegacyInputIterator) to an implementation object, which holds:

  • a container (such as std::vector) of non-recursive directory_iterators that forms the recursion stack
  • the recursion depth counter (accessible with depth())
  • the directory options used at construction (accessible with options())
  • the pending recursion flag (accessible with recursion_pending(), may be combined with the directory options to save space)

[edit] Example

#include <fstream>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
 
int main()
{
    fs::current_path(fs::temp_directory_path());
    fs::create_directories("sandbox/a/b");
    std::ofstream("sandbox/file1.txt");
    fs::create_symlink("a", "sandbox/syma");
    for(auto& p: fs::recursive_directory_iterator("sandbox"))
        std::cout << p.path() << '\n';
    fs::remove_all("sandbox");
}

Possible output:

"sandbox/a"
"sandbox/a/b"
"sandbox/file1.txt"
"sandbox/syma"

[edit] 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 recursive_directory_iterator was neither a borrowed_range nor a view it is both

[edit] See also

an iterator to the contents of the directory
(class) [edit]
a directory entry
(class) [edit]
options for iterating directory contents
(enum) [edit]