31 Input/output library [input.output]

31.12 File systems [filesystems]

31.12.6 Class path [fs.class.path]

31.12.6.1 General [fs.class.path.general]

1
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An object of class path represents a path and contains a pathname.
Such an object is concerned only with the lexical and syntactic aspects of a path.
The path does not necessarily exist in external storage, and the pathname is not necessarily valid for the current operating system or for a particular file system.
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[Note 1: 
Class path is used to support the differences between the string types used by different operating systems to represent pathnames, and to perform conversions between encodings when necessary.
— end note]
3
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A path is a sequence of elements that identify the location of a file within a filesystem.
The elements are the root-name, root-directory, and an optional sequence of filenames ([fs.path.generic]).
The maximum number of elements in the sequence is operating system dependent ([fs.conform.os]).
4
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An absolute path is a path that unambiguously identifies the location of a file without reference to an additional starting location.
The elements of a path that determine if it is absolute are operating system dependent.
A relative path is a path that is not absolute, and as such, only unambiguously identifies the location of a file when resolved relative to an implied starting location.
The elements of a path that determine if it is relative are operating system dependent.
[Note 2: 
Pathnames “.” and “..” are relative paths.
— end note]
5
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A pathname is a character string that represents the name of a path.
Pathnames are formatted according to the generic pathname format grammar ([fs.path.generic]) or according to an operating system dependent native pathname format accepted by the host operating system.
6
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Pathname resolution is the operating system dependent mechanism for resolving a pathname to a particular file in a file hierarchy.
There may be multiple pathnames that resolve to the same file.
[Example 1: 
For POSIX-based operating systems, this mechanism is specified in POSIX, section 4.12, Pathname resolution.
— end example]
namespace std::filesystem { class path { public: using value_type = see below; using string_type = basic_string<value_type>; static constexpr value_type preferred_separator = see below; // [fs.enum.path.format], enumeration format enum format; // [fs.path.construct], 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 InputIterator> path(InputIterator first, InputIterator last, format fmt = auto_format); template<class Source> path(const Source& source, const locale& loc, format fmt = auto_format); template<class InputIterator> path(InputIterator first, InputIterator last, const locale& loc, format fmt = auto_format); ~path(); // [fs.path.assign], 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 InputIterator> path& assign(InputIterator first, InputIterator last); // [fs.path.append], appends path& operator/=(const path& p); template<class Source> path& operator/=(const Source& source); template<class Source> path& append(const Source& source); template<class InputIterator> path& append(InputIterator first, InputIterator last); // [fs.path.concat], 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 InputIterator> path& concat(InputIterator first, InputIterator last); // [fs.path.modifiers], 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; // [fs.path.nonmember], 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); // [fs.path.native.obs], 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; // [fs.path.generic.obs], 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; // [fs.path.compare], 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; // [fs.path.decompose], 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; // [fs.path.query], query 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; // [fs.path.gen], generation path lexically_normal() const; path lexically_relative(const path& base) const; path lexically_proximate(const path& base) const; // [fs.path.itr], iterators class iterator; using const_iterator = iterator; iterator begin() const; iterator end() const; // [fs.path.io], 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); }; }
7
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value_type is a typedef for the operating system dependent encoded character type used to represent pathnames.
8
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The value of the preferred_separator member is the operating system dependent preferred-separator character ([fs.path.generic]).
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[Example 2: 
For POSIX-based operating systems, value_type is char and preferred_separator is the slash character ('/').
For Windows-based operating systems, value_type is wchar_t and preferred_separator is the backslash character (L'\\').
— end example]