NAME¶

std::filesystem::path - std::filesystem::path

Synopsis¶

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

Objects of type path represent paths on a filesystem. Only syntactic aspects of
paths are handled: the pathname may represent a non-existing path or even one that
is not allowed to exist on the current file system or OS.

The path name has the following syntax:

1. root-name(optional): identifies the root on a filesystem with multiple roots
(such as "C:" or "//myserver"). In case of ambiguity, the longest sequence of
characters that forms a valid root-name is treated as the root-name. The
standard library may define additional root-names besides the ones understood by
the OS API.
2. root-directory(optional): a directory separator that, if present, marks this
path as absolute. If it is missing (and the first element other than the root
name is a file name), then the path is relative and requires another path as the
starting location to resolve to a file name.
3. Zero or more of the following:

* file-name: sequence of characters that aren't directory separators or preferred
directory separators (additional limitations may be imposed by the OS or file
system). This name may identify a file, a hard link, a symbolic link, or a
directory. Two special file-names are recognized:

* dot: the file name consisting of a single dot character . is a directory name
that refers to the current directory.
* dot-dot: the file name consisting of two dot characters .. is a directory name
that refers to the parent directory.
* directory-separators: the forward slash character / or the alternative character
provided as path::preferred_separator. If this character is repeated, it is
treated as a single directory separator: /usr///////lib is the same as /usr/lib.

A path can be normalized by following this algorithm:

1. If the path is empty, stop (normal form of an empty path is an empty path).
2. Replace each directory-separator (which may consist of multiple slashes) with a
single path::preferred_separator.
3. Replace each slash character in the root-name with path::preferred_separator.
4. Remove each dot and any immediately following directory-separator.
5. Remove each non-dot-dot filename immediately followed by a directory-separator
and a dot-dot, along with any immediately following directory-separator.
6. If there is root-directory, remove all dot-dots and any directory-separators
immediately following them.
7. If the last filename is dot-dot, remove any trailing directory-separator.
8. If the path is empty, add a dot (normal form of ./ is .).

The path can be traversed element-wise via iterators returned by the begin() and
end() functions, which views the path in generic format and iterates over root name,
root directory, and the subsequent file name elements (directory separators are
skipped except the one that identifies the root directory). If the very last element
in the path is a directory separator, the last iterator will dereference to an empty
element.

Calling any non-const member function of a path invalidates all iterators referring
to elements of that object.

If the OS uses a native syntax that is different from the portable generic syntax
described above, library functions that are defined to accept "detected format"
accept path names in both formats: a detected format argument is taken to be in the
generic format if and only if it matches the generic format but is not acceptable to
the operating system as a native path. On those OS where native format differs
between pathnames of directories and pathnames of files, a generic pathname is
treated as a directory path if it ends on a directory separator and a regular file
otherwise.

In any case, the path class behaves as if it stores a pathname in the native format
and automatically converts to generic format as needed (each member function
specifies which format it interprets the path as).

On POSIX systems, the generic format is the native format and there is no need to
distinguish or convert between them.

Paths are implicitly convertible to and from std::basic_strings, which makes it
possible to use them with other file APIs.

The stream operators use std::quoted so that spaces do not cause truncation when
later read by stream input operator.

Decomposition member functions (e.g. extension) return filesystem::path objects
instead of string objects as other APIs do.

Member types and constants¶

Type Definition
value_type character type used by the native encoding of the filesystem: char on
POSIX, wchar_t on Windows
string_type std::basic_string<value_type>
a constant LegacyInputIterator with a value_type of path that meets
all requirements of LegacyBidirectionalIterator except that for two
equal dereferenceable iterators a and b of type const_iterator, there
const_iterator is no requirement that *a and *b refer to the same object.

It is unspecified whether const_iterator is actually a
LegacyBidirectionalIterator
iterator an alias to const_iterator
determines how to interpret string representations of pathnames.

The following enumerators are also defined:

format Constant Explanation
(C++17) native_format native pathname format
generic_format generic pathname format
auto_format implementation-defined format, auto-detected where
possible

(enum)

Member constants¶

alternative directory separator which may be used in addition
constexpr value_type to the portable /. On Windows, this is the backslash character
preferred_separator \. On POSIX, this is the same forward slash / as the portable
[static] separator
(public static member constant)

Member functions¶

constructor constructs a path
(public member function)
destructor destroys a path object
(public member function)
operator= assigns another path
(public member function)
assign assigns contents
(public member function)
Concatenation
append appends elements to the path with a directory separator
operator/= (public member function)
concat concatenates two paths without introducing a directory
operator+= separator
(public member function)

Modifiers¶

clear erases the contents
(public member function)
make_preferred converts directory separators to preferred directory separator
(public member function)
remove_filename removes filename path component
(public member function)
replace_filename replaces the last path component with another path
(public member function)
replace_extension replaces the extension
(public member function)
swap swaps two paths
(public member function)
Format observers
c_str returns the native version of the path
native (public member function)
operator string_type
string
wstring returns the path in native pathname format converted to a
u8string string
u16string (public member function)
u32string
generic_string
generic_wstring returns the path in generic pathname format converted to a
generic_u8string string
generic_u16string (public member function)
generic_u32string
Compare
compares the lexical representations of two paths
compare lexicographically
(public member function)

Generation¶

lexically_normal converts path to normal form
lexically_relative converts path to relative form
lexically_proximate converts path to proximate form
(public member function)
Decomposition
root_name returns the root-name of the path, if present
(public member function)
root_directory returns the root directory of the path, if present
(public member function)
root_path returns the root path of the path, if present
(public member function)
relative_path returns path relative to the root path
(public member function)
parent_path returns the path of the parent path
(public member function)
filename returns the filename path component
(public member function)
returns the stem path component (filename without the final
stem extension)
(public member function)
extension returns the file extension path component
(public member function)
Queries
empty checks if the path is empty
(public member function)
has_root_path
has_root_name
has_root_directory
has_relative_path checks if the corresponding path element is not empty
has_parent_path (public member function)
has_filename
has_stem
has_extension
is_absolute checks if root_path() uniquely identifies file system location
is_relative (public member function)

Iterators¶

begin iterator access to the path as a sequence of elements
end (public member function)

Non-member functions¶

Defined in namespace std::filesystem
swap(std::filesystem::path) swaps two paths
(C++17) (function)
hash_value calculates a hash value for a path object
(C++17) (function)
operator==
operator!=
operator<
operator<=
operator>
operator>=
operator<=> lexicographically compares two paths
(C++17) (function)
(C++17)(until C++20)
(C++17)(until C++20)
(C++17)(until C++20)
(C++17)(until C++20)
(C++17)(until C++20)
(C++20)
operator/ concatenates two paths with a directory separator
(C++17) (function)
operator<< performs stream input and output on a quoted path
operator>> (function)
(C++17)
u8path creates a path from a UTF-8 encoded source
(C++17)(deprecated in C++20) (function)

Helper classes¶

Defined in namespace std
std::hash<std::filesystem::path> hash support for std::filesystem::path
(C++17) (class template specialization)
std::formatter<std::filesystem::path> formatting support for filesystem::path
(C++26) (class template specialization)

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 3657 C++17 hash for path was disabled enabled