Standard library header <filesystem> (C++17)

 

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This header is part of the filesystem support library.

Includes
<compare> (C++20)	Three-way comparison operator support
Classes
Defined in namespace std::filesystem
path (C++17)	represents a path (class)
filesystem_error (C++17)	an exception thrown on file system errors (class)
directory_entry (C++17)	a directory entry (class)
directory_iterator (C++17)	an iterator to the contents of the directory (class)
recursive_directory_iterator (C++17)	an iterator to the contents of a directory and its subdirectories (class)
file_status (C++17)	represents file type and permissions (class)
space_info (C++17)	information about free and available space on the filesystem (class)
file_type (C++17)	the type of a file (enum)
perms (C++17)	identifies file system permissions (enum)
perm_options (C++17)	specifies semantics of permissions operations (enum)
copy_options (C++17)	specifies semantics of copy operations (enum)
directory_options (C++17)	options for iterating directory contents (enum)
file_time_type (C++17)	represents file time values (typedef)
Defined in namespace std
std::hash<std::filesystem::path> (C++17)	hash support for std::filesystem::path (class template specialization)
Forward declarations
Defined in header <functional>
Defined in namespace std
hash (C++11)	hash function object (class template)
Functions
Defined in namespace std::filesystem
u8path (C++17)(deprecated in C++20)	creates a path from a UTF-8 encoded source (function)
absolute (C++17)	composes an absolute path (function)
canonicalweakly_canonical (C++17)	composes a canonical path (function)
relativeproximate (C++17)	composes a relative path (function)
copy (C++17)	copies files or directories (function)
copy_file (C++17)	copies file contents (function)
copy_symlink (C++17)	copies a symbolic link (function)
create_directorycreate_directories (C++17)(C++17)	creates new directory (function)
create_hard_link (C++17)	creates a hard link (function)
create_symlinkcreate_directory_symlink (C++17)(C++17)	creates a symbolic link (function)
current_path (C++17)	returns or sets the current working directory (function)
exists (C++17)	checks whether path refers to existing file system object (function)
equivalent (C++17)	checks whether two paths refer to the same file system object (function)
file_size (C++17)	returns the size of a file (function)
hard_link_count (C++17)	returns the number of hard links referring to the specific file (function)
last_write_time (C++17)	gets or sets the time of the last data modification (function)
permissions (C++17)	modifies file access permissions (function)
read_symlink (C++17)	obtains the target of a symbolic link (function)
removeremove_all (C++17)(C++17)	removes a file or empty directory removes a file or directory and all its contents, recursively (function)
rename (C++17)	moves or renames a file or directory (function)
resize_file (C++17)	changes the size of a regular file by truncation or zero-fill (function)
space (C++17)	determines available free space on the file system (function)
statussymlink_status (C++17)(C++17)	determines file attributes determines file attributes, checking the symlink target (function)
temp_directory_path (C++17)	returns a directory suitable for temporary files (function)
File types
is_block_file (C++17)	checks whether the given path refers to block device (function)
is_character_file (C++17)	checks whether the given path refers to a character device (function)
is_directory (C++17)	checks whether the given path refers to a directory (function)
is_empty (C++17)	checks whether the given path refers to an empty file or directory (function)
is_fifo (C++17)	checks whether the given path refers to a named pipe (function)
is_other (C++17)	checks whether the argument refers to an other file (function)
is_regular_file (C++17)	checks whether the argument refers to a regular file (function)
is_socket (C++17)	checks whether the argument refers to a named IPC socket (function)
is_symlink (C++17)	checks whether the argument refers to a symbolic link (function)
status_known (C++17)	checks whether file status is known (function)

Synopsis

#include <compare>
 
namespace std::filesystem {
  // paths
  class path;
 
  // path non-member functions
  void swap(path& lhs, path& rhs) noexcept;
  size_t hash_value(const path& p) noexcept;
 
  // filesystem errors
  class filesystem_error;
 
  // directory entries
  class directory_entry;
 
  // directory iterators
  class directory_iterator;
 
  // range access for directory iterators
  directory_iterator begin(directory_iterator iter) noexcept;
  directory_iterator end(directory_iterator) noexcept;
 
  // recursive directory iterators
  class recursive_directory_iterator;
 
  // range access for recursive directory iterators
  recursive_directory_iterator begin(recursive_directory_iterator iter) noexcept;
  recursive_directory_iterator end(recursive_directory_iterator) noexcept;
 
  // file status
  class file_status;
 
  struct space_info {
    uintmax_t capacity;
    uintmax_t free;
    uintmax_t available;
 
    friend bool operator==(const space_info&, const space_info&) = default;
  };
 
  // enumerations
  enum class file_type;
  enum class perms;
  enum class perm_options;
  enum class copy_options;
  enum class directory_options;
 
  using file_time_type = chrono::time_point<chrono::file_clock>;
 
  // filesystem operations
  path absolute(const path& p);
  path absolute(const path& p, error_code& ec);
 
  path canonical(const path& p);
  path canonical(const path& p, error_code& ec);
 
  void copy(const path& from, const path& to);
  void copy(const path& from, const path& to, error_code& ec);
  void copy(const path& from, const path& to, copy_options options);
  void copy(const path& from, const path& to, copy_options options,
            error_code& ec);
 
  bool copy_file(const path& from, const path& to);
  bool copy_file(const path& from, const path& to, error_code& ec);
  bool copy_file(const path& from, const path& to, copy_options option);
  bool copy_file(const path& from, const path& to, copy_options option,
                 error_code& ec);
 
  void copy_symlink(const path& existing_symlink, const path& new_symlink);
  void copy_symlink(const path& existing_symlink, const path& new_symlink,
                    error_code& ec) noexcept;
 
  bool create_directories(const path& p);
  bool create_directories(const path& p, error_code& ec);
 
  bool create_directory(const path& p);
  bool create_directory(const path& p, error_code& ec) noexcept;
 
  bool create_directory(const path& p, const path& attributes);
  bool create_directory(const path& p, const path& attributes,
                        error_code& ec) noexcept;
 
  void create_directory_symlink(const path& to, const path& new_symlink);
  void create_directory_symlink(const path& to, const path& new_symlink,
                                error_code& ec) noexcept;
 
  void create_hard_link(const path& to, const path& new_hard_link);
  void create_hard_link(const path& to, const path& new_hard_link,
                        error_code& ec) noexcept;
 
  void create_symlink(const path& to, const path& new_symlink);
  void create_symlink(const path& to, const path& new_symlink,
                      error_code& ec) noexcept;
 
  path current_path();
  path current_path(error_code& ec);
  void current_path(const path& p);
  void current_path(const path& p, error_code& ec) noexcept;
 
  bool equivalent(const path& p1, const path& p2);
  bool equivalent(const path& p1, const path& p2, error_code& ec) noexcept;
 
  bool exists(file_status s) noexcept;
  bool exists(const path& p);
  bool exists(const path& p, error_code& ec) noexcept;
 
  uintmax_t file_size(const path& p);
  uintmax_t file_size(const path& p, error_code& ec) noexcept;
 
  uintmax_t hard_link_count(const path& p);
  uintmax_t hard_link_count(const path& p, error_code& ec) noexcept;
 
  bool is_block_file(file_status s) noexcept;
  bool is_block_file(const path& p);
  bool is_block_file(const path& p, error_code& ec) noexcept;
 
  bool is_character_file(file_status s) noexcept;
  bool is_character_file(const path& p);
  bool is_character_file(const path& p, error_code& ec) noexcept;
 
  bool is_directory(file_status s) noexcept;
  bool is_directory(const path& p);
  bool is_directory(const path& p, error_code& ec) noexcept;
 
  bool is_empty(const path& p);
  bool is_empty(const path& p, error_code& ec);
 
  bool is_fifo(file_status s) noexcept;
  bool is_fifo(const path& p);
  bool is_fifo(const path& p, error_code& ec) noexcept;
 
  bool is_other(file_status s) noexcept;
  bool is_other(const path& p);
  bool is_other(const path& p, error_code& ec) noexcept;
 
  bool is_regular_file(file_status s) noexcept;
  bool is_regular_file(const path& p);
  bool is_regular_file(const path& p, error_code& ec) noexcept;
 
  bool is_socket(file_status s) noexcept;
  bool is_socket(const path& p);
  bool is_socket(const path& p, error_code& ec) noexcept;
 
  bool is_symlink(file_status s) noexcept;
  bool is_symlink(const path& p);
  bool is_symlink(const path& p, error_code& ec) noexcept;
 
  file_time_type last_write_time(const path& p);
  file_time_type last_write_time(const path& p, error_code& ec) noexcept;
  void last_write_time(const path& p, file_time_type new_time);
  void last_write_time(const path& p, file_time_type new_time,
                       error_code& ec) noexcept;
 
  void permissions(const path& p, perms prms, perm_options opts=perm_options::replace);
  void permissions(const path& p, perms prms, error_code& ec) noexcept;
  void permissions(const path& p, perms prms, perm_options opts, error_code& ec);
 
  path proximate(const path& p, error_code& ec);
  path proximate(const path& p, const path& base = current_path());
  path proximate(const path& p, const path& base, error_code& ec);
 
  path read_symlink(const path& p);
  path read_symlink(const path& p, error_code& ec);
 
  path relative(const path& p, error_code& ec);
  path relative(const path& p, const path& base = current_path());
  path relative(const path& p, const path& base, error_code& ec);
 
  bool remove(const path& p);
  bool remove(const path& p, error_code& ec) noexcept;
 
  uintmax_t remove_all(const path& p);
  uintmax_t remove_all(const path& p, error_code& ec);
 
  void rename(const path& from, const path& to);
  void rename(const path& from, const path& to, error_code& ec) noexcept;
 
  void resize_file(const path& p, uintmax_t size);
  void resize_file(const path& p, uintmax_t size, error_code& ec) noexcept;
 
  space_info space(const path& p);
  space_info space(const path& p, error_code& ec) noexcept;
 
  file_status status(const path& p);
  file_status status(const path& p, error_code& ec) noexcept;
 
  bool status_known(file_status s) noexcept;
 
  file_status symlink_status(const path& p);
  file_status symlink_status(const path& p, error_code& ec) noexcept;
 
  path temp_directory_path();
  path temp_directory_path(error_code& ec);
 
  path weakly_canonical(const path& p);
  path weakly_canonical(const path& p, error_code& ec);
}
 
// hash support
namespace std {
  template<class T> struct hash;
  template<> struct hash<filesystem::path>;
}
 
namespace std::ranges {
  template<>
  inline constexpr bool enable_borrowed_range<filesystem::directory_iterator> = true;
  template<>
  inline constexpr bool
    enable_borrowed_range<filesystem::recursive_directory_iterator> = true;
 
  template<>
  inline constexpr bool enable_view<filesystem::directory_iterator> = true;
  template<>
  inline constexpr bool enable_view<filesystem::recursive_directory_iterator> = true;
}
 
// deprecated
namespace std::filesystem {
  template<class Source>
    path u8path(const Source& source);
  template<class InputIterator>
    path u8path(InputIt first, InputIt last);
}

Class std::filesystem::path

namespace std::filesystem {
  class path {
  public:
    using value_type  = /* see description */;
    using string_type = basic_string<value_type>;
    static constexpr value_type preferred_separator = /* see description */;
 
    // enumeration format
    enum format;
 
    // constructors and destructor
    path() noexcept;
    path(const path& p);
    path(path&& p) noexcept;
    path(string_type&& source, format fmt = auto_format);
    template<class Source>
      path(const Source& source, format fmt = auto_format);
    template<class InputIt>
      path(InputIt first, InputIt last, format fmt = auto_format);
    template<class Source>
      path(const Source& source, const locale& loc, format fmt = auto_format);
    template<class InputIt>
      path(InputIt first, InputIt last, const locale& loc, format fmt = auto_format);
    ~path();
 
    // assignments
    path& operator=(const path& p);
    path& operator=(path&& p) noexcept;
    path& operator=(string_type&& source);
    path& assign(string_type&& source);
    template<class Source>
      path& operator=(const Source& source);
    template<class Source>
      path& assign(const Source& source);
    template<class InputIt>
      path& assign(InputIt first, InputIt last);
 
    // appends
    path& operator/=(const path& p);
    template<class Source>
      path& operator/=(const Source& source);
    template<class Source>
      path& append(const Source& source);
    template<class InputIt>
      path& append(InputIt first, InputIt last);
 
    // concatenation
    path& operator+=(const path& x);
    path& operator+=(const string_type& x);
    path& operator+=(basic_string_view<value_type> x);
    path& operator+=(const value_type* x);
    path& operator+=(value_type x);
    template<class Source>
      path& operator+=(const Source& x);
    template<class ECharT>
      path& operator+=(ECharT x);
    template<class Source>
      path& concat(const Source& x);
    template<class InputIt>
      path& concat(InputIt first, InputIt last);
 
    // modifiers
    void  clear() noexcept;
    path& make_preferred();
    path& remove_filename();
    path& replace_filename(const path& replacement);
    path& replace_extension(const path& replacement = path());
    void  swap(path& rhs) noexcept;
 
    // non-member operators
    friend bool operator==(const path& lhs, const path& rhs) noexcept;
    friend strong_ordering operator<=>(const path& lhs, const path& rhs) noexcept;
 
    friend path operator/ (const path& lhs, const path& rhs);
 
    // native format observers
    const string_type& native() const noexcept;
    const value_type*  c_str() const noexcept;
    operator string_type() const;
 
    template<class ECharT, class Traits = char_traits<ECharT>,
             class Allocator = allocator<ECharT>>
      basic_string<ECharT, Traits, Allocator>
        string(const Allocator& a = Allocator()) const;
    std::string    string() const;
    std::wstring   wstring() const;
    std::u8string  u8string() const;
    std::u16string u16string() const;
    std::u32string u32string() const;
 
    // generic format observers
    template<class ECharT, class Traits = char_traits<ECharT>,
             class Allocator = allocator<ECharT>>
      basic_string<ECharT, Traits, Allocator>
        generic_string(const Allocator& a = Allocator()) const;
    std::string    generic_string() const;
    std::wstring   generic_wstring() const;
    std::u8string  generic_u8string() const;
    std::u16string generic_u16string() const;
    std::u32string generic_u32string() const;
 
    // compare
    int compare(const path& p) const noexcept;
    int compare(const string_type& s) const;
    int compare(basic_string_view<value_type> s) const;
    int compare(const value_type* s) const;
 
    // decomposition
    path root_name() const;
    path root_directory() const;
    path root_path() const;
    path relative_path() const;
    path parent_path() const;
    path filename() const;
    path stem() const;
    path extension() const;
 
    // query
    [[nodiscard]] bool empty() const noexcept;
    bool has_root_name() const;
    bool has_root_directory() const;
    bool has_root_path() const;
    bool has_relative_path() const;
    bool has_parent_path() const;
    bool has_filename() const;
    bool has_stem() const;
    bool has_extension() const;
    bool is_absolute() const;
    bool is_relative() const;
 
    // generation
    path lexically_normal() const;
    path lexically_relative(const path& base) const;
    path lexically_proximate(const path& base) const;
 
    // iterators
    class iterator;
    using const_iterator = iterator;
 
    iterator begin() const;
    iterator end() const;
 
    // path inserter and extractor
    template<class CharT, class Traits>
      friend basic_ostream<CharT, Traits>&
        operator<<(basic_ostream<CharT, Traits>& os, const path& p);
    template<class CharT, class Traits>
      friend basic_istream<CharT, Traits>&
        operator>>(basic_istream<CharT, Traits>& is, path& p);
  };
}

Class std::filesystem::filesystem_error

namespace std::filesystem {
  class filesystem_error : public system_error {
  public:
    filesystem_error(const string& what_arg, error_code ec);
    filesystem_error(const string& what_arg,
                     const path& p1, error_code ec);
    filesystem_error(const string& what_arg,
                     const path& p1, const path& p2, error_code ec);
 
    const path& path1() const noexcept;
    const path& path2() const noexcept;
    const char* what() const noexcept override;
  };
}

Class std::filesystem::directory_entry

namespace std::filesystem {
  class directory_entry {
  public:
    // constructors and destructor
    directory_entry() noexcept = default;
    directory_entry(const directory_entry&) = default;
    directory_entry(directory_entry&&) noexcept = default;
    explicit directory_entry(const filesystem::path& p);
    directory_entry(const filesystem::path& p, error_code& ec);
    ~directory_entry();
 
    // assignments
    directory_entry& operator=(const directory_entry&) = default;
    directory_entry& operator=(directory_entry&&) noexcept = default;
 
    // modifiers
    void assign(const filesystem::path& p);
    void assign(const filesystem::path& p, error_code& ec);
    void replace_filename(const filesystem::path& p);
    void replace_filename(const filesystem::path& p, error_code& ec);
    void refresh();
    void refresh(error_code& ec) noexcept;
 
    // observers
    const filesystem::path& path() const noexcept;
    operator const filesystem::path&() const noexcept;
    bool exists() const;
    bool exists(error_code& ec) const noexcept;
    bool is_block_file() const;
    bool is_block_file(error_code& ec) const noexcept;
    bool is_character_file() const;
    bool is_character_file(error_code& ec) const noexcept;
    bool is_directory() const;
    bool is_directory(error_code& ec) const noexcept;
    bool is_fifo() const;
    bool is_fifo(error_code& ec) const noexcept;
    bool is_other() const;
    bool is_other(error_code& ec) const noexcept;
    bool is_regular_file() const;
    bool is_regular_file(error_code& ec) const noexcept;
    bool is_socket() const;
    bool is_socket(error_code& ec) const noexcept;
    bool is_symlink() const;
    bool is_symlink(error_code& ec) const noexcept;
    uintmax_t file_size() const;
    uintmax_t file_size(error_code& ec) const noexcept;
    uintmax_t hard_link_count() const;
    uintmax_t hard_link_count(error_code& ec) const noexcept;
    file_time_type last_write_time() const;
    file_time_type last_write_time(error_code& ec) const noexcept;
    file_status status() const;
    file_status status(error_code& ec) const noexcept;
    file_status symlink_status() const;
    file_status symlink_status(error_code& ec) const noexcept;
 
    bool operator==(const directory_entry& rhs) const noexcept;
    strong_ordering operator<=>(const directory_entry& rhs) const noexcept;
 
    // inserter
    template<class charT, class traits>
      friend basic_ostream<charT, traits>&
        operator<<(basic_ostream<charT, traits>& os, const directory_entry& d);
 
  private:
    filesystem::path pathobject;        // exposition only
    friend class directory_iterator;    // exposition only
  };
}

Class std::filesystem::directory_iterator

namespace std::filesystem {
  class directory_iterator {
  public:
    using iterator_category = input_iterator_tag;
    using value_type        = directory_entry;
    using difference_type   = ptrdiff_t;
    using pointer           = const directory_entry*;
    using reference         = const directory_entry&;
 
    // member functions
    directory_iterator() noexcept;
    explicit directory_iterator(const path& p);
    directory_iterator(const path& p, directory_options options);
    directory_iterator(const path& p, error_code& ec);
    directory_iterator(const path& p, directory_options options,
                       error_code& ec);
    directory_iterator(const directory_iterator& rhs);
    directory_iterator(directory_iterator&& rhs) noexcept;
    ~directory_iterator();
 
    directory_iterator& operator=(const directory_iterator& rhs);
    directory_iterator& operator=(directory_iterator&& rhs) noexcept;
 
    const directory_entry& operator*() const;
    const directory_entry* operator->() const;
    directory_iterator&    operator++();
    directory_iterator&    increment(error_code& ec);
 
    // other members as required by input iterators
  };
}

Class std::filesystem::recursive_directory_iterator

namespace std::filesystem {
  class recursive_directory_iterator {
  public:
    using iterator_category = input_iterator_tag;
    using value_type        = directory_entry;
    using difference_type   = ptrdiff_t;
    using pointer           = const directory_entry*;
    using reference         = const directory_entry&;
 
    // constructors and destructor
    recursive_directory_iterator() noexcept;
    explicit recursive_directory_iterator(const path& p);
    recursive_directory_iterator(const path& p, directory_options options);
    recursive_directory_iterator(const path& p, directory_options options,
                                 error_code& ec);
    recursive_directory_iterator(const path& p, error_code& ec);
    recursive_directory_iterator(const recursive_directory_iterator& rhs);
    recursive_directory_iterator(recursive_directory_iterator&& rhs) noexcept;
    ~recursive_directory_iterator();
 
    // observers
    directory_options  options() const;
    int                depth() const;
    bool               recursion_pending() const;
 
    const directory_entry& operator*() const;
    const directory_entry* operator->() const;
 
    // modifiers
    recursive_directory_iterator&
      operator=(const recursive_directory_iterator& rhs);
    recursive_directory_iterator&
      operator=(recursive_directory_iterator&& rhs) noexcept;
 
    recursive_directory_iterator& operator++();
    recursive_directory_iterator& increment(error_code& ec);
 
    void pop();
    void pop(error_code& ec);
    void disable_recursion_pending();
 
    // other members as required by input iterators
  };
}

Class std::filesystem::file_status

namespace std::filesystem {
  class file_status {
  public:
    // constructors and destructor
    file_status() noexcept : file_status(file_type::none) {}
    explicit file_status(file_type ft,
                         perms prms = perms::unknown) noexcept;
    file_status(const file_status&) noexcept = default;
    file_status(file_status&&) noexcept = default;
    ~file_status();
 
    // assignments
    file_status& operator=(const file_status&) noexcept = default;
    file_status& operator=(file_status&&) noexcept = default;
 
    // modifiers
    void       type(file_type ft) noexcept;
    void       permissions(perms prms) noexcept;
 
    // observers
    file_type  type() const noexcept;
    perms      permissions() const noexcept;
 
    friend bool operator==(const file_status& lhs, const file_status& rhs) noexcept
      { return lhs.type() == rhs.type() && lhs.permissions() == rhs.permissions(); }
  };
}