This subclause describes operations on file systems and their components, such as paths, regular files, and directories.
Conformance is specified in terms of behavior. Ideal behavior is not always implementable, so the conformance subclauses take that into account.
Some behavior is specified by reference to POSIX ([fs.norm.ref]). How such behavior is actually implemented is unspecified. [ Note: This constitutes an “as if” rule allowing implementations to call native operating system or other APIs. — end note ]
Implementations are encouraged to provide such behavior as it is defined by POSIX. Implementations shall document any behavior that differs from the behavior defined by POSIX. Implementations that do not support exact POSIX behavior are encouraged to provide behavior as close to POSIX behavior as is reasonable given the limitations of actual operating systems and file systems. If an implementation cannot provide any reasonable behavior, the implementation shall report an error as specified in [fs.err.report]. [ Note: This allows users to rely on an exception being thrown or an error code being set when an implementation cannot provide any reasonable behavior. — end note ]
Implementations are not required to provide behavior that is not supported by a particular file system. [ Example: The FAT file system used by some memory cards, camera memory, and floppy disks does not support hard links, symlinks, and many other features of more capable file systems, so implementations are not required to support those features on the FAT file system. — end example ]
Some behavior is specified as being operating system dependent ([fs.def.osdep]). The operating system an implementation is dependent upon is implementation-defined.
It is permissible for an implementation to be dependent upon an operating system emulator rather than the actual underlying operating system.
Behavior is undefined if calls to functions provided by this subclause introduce a file system race ([fs.def.race]).
If the possibility of a file system race would make it unreliable for a program to test for a precondition before calling a function described herein, Requires: is not specified for the function. [ Note: As a design practice, preconditions are not specified when it is unreasonable for a program to detect them prior to calling the function. — end note ]
POSIX® is a registered trademark of The IEEE. Windows® is a registered trademark of Microsoft Corporation. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO or IEC of these products.
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.
An absolute path that has no elements that are symbolic links, and no dot or dot-dot elements ([path.generic]).
A file within a file system that acts as a container of directory entries that contain information about other files, possibly including other directory files.
An object within a file system that holds user or system data. Files can be written to, or read from, or both. A file has certain attributes, including type. File types include regular files and directories. Other types of files, such as symbolic links ([fs.def.symlink]), may be supported by the implementation.
A collection of files and certain of their attributes.
The condition that occurs when multiple threads, processes, or computers interleave access and modification of the same object within a file system.
The name of a file. Filenames dot and dot-dot have special meaning. The following characteristics of filenames are operating system dependent:
The permitted characters. [ Example: Some operating systems prohibit the ASCII control characters (0x00 – 0x1F) in filenames. — end example ]
The maximum permitted length.
Filenames that are not permitted.
Filenames that have special meaning.
Case awareness and sensitivity during path resolution.
Special rules that may apply to file types other than regular files, such as directories.
A link ([fs.def.link]) to an existing file. Some file systems support multiple hard links to a file. If the last hard link to a file is removed, the file itself is removed. [ Note: A hard link can be thought of as a shared-ownership smart pointer to a file. — end note ]
A directory entry that associates a filename with a file. A link is either a hard link ([fs.def.hardlink]) or a symbolic link ([fs.def.symlink]).
For narrow character strings, the operating system dependent current encoding for pathnames ([fs.def.pathname]). For wide character strings, the implementation defined execution wide-character set encoding ([lex.charset]).
The operating system dependent pathname format accepted by the host operating system.
A path with no redundant current directory (dot) elements, no redundant parent directory (dot-dot) elements, and no redundant directory-separators. The normal form for an empty path is an empty path. The normal form for a path ending in a directory-separator that is not the root directory has a current directory (dot) element appended. A path in normal form is said to be normalized. The process of obtaining a normalized path from a path that is not in normal form is called normalization. [ Note: The rule that appends a current directory (dot) element supports operating systems like OpenVMS that use different syntax for directory names and regular file names. — end note ]
Behavior that is dependent upon the behavior and characteristics of an operating system. See [fs.conform.os].
⟨of a directory⟩ the directory that both contains a directory entry for the given directory and is represented by the filename dot-dot in the given directory.
⟨of other types of files⟩ a directory containing a directory entry for the file under discussion.
A sequence of elements that identify the location of a file within a filesystem. The elements are the root-nameopt, root-directoryopt, and an optional sequence of filenames. The maximum number of elements in the sequence is operating system dependent.
A character string that represents the name of a path. Pathnames are formatted according to the generic pathname format grammar ([path.generic]) or an operating system dependent native pathname format.
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: POSIX specifies the mechanism in section 4.11, Pathname resolution. — end example ]
A path that is not absolute, and as such, only unambiguously identifies the location of a file when resolved ([fs.def.pathres]) relative to an implied starting location. The elements of a path that determine if it is relative are operating system dependent. [ Note: Pathnames “.” and “..” are relative paths. — end note ]
A type of file with the property that when the file is encountered during pathname resolution, a string stored by the file is used to modify the pathname resolution. [ Note: Symbolic links are often called symlinks. A symbolic link can be thought of as a raw pointer to a file. If the file pointed to does not exist, the symbolic link is said to be a “dangling” symbolic link. — end note ]
Throughout this subclause, char, wchar_t, char16_t, and char32_t are collectively called encoded character types.
Functions with template parameters named EcharT shall not participate in overload resolution unless EcharT is one of the encoded character types.
Template parameters named InputIterator shall meet the input iterator requirements ([input.iterators]) and shall have a value type that is one of the encoded character types.
[ Note: Use of an encoded character type implies an associated encoding. Since signed char and unsigned char have no implied encoding, they are not included as permitted types. — end note ]
Template parameters named Allocator shall meet the Allocator requirements ([allocator.requirements]).
Unless otherwise specified, references to entities described in this subclause are assumed to be qualified with ::std::filesystem::.
namespace std::filesystem {
// [class.path], paths
class path;
// [path.non-member], path non-member functions
void swap(path& lhs, path& rhs) noexcept;
size_t hash_value(const path& p) noexcept;
bool operator==(const path& lhs, const path& rhs) noexcept;
bool operator!=(const path& lhs, const path& rhs) noexcept;
bool operator< (const path& lhs, const path& rhs) noexcept;
bool operator<=(const path& lhs, const path& rhs) noexcept;
bool operator> (const path& lhs, const path& rhs) noexcept;
bool operator>=(const path& lhs, const path& rhs) noexcept;
path operator/ (const path& lhs, const path& rhs);
// [path.io], path inserter and extractor
template <class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, const path& p);
template <class charT, class traits>
basic_istream<charT, traits>&
operator>>(basic_istream<charT, traits>& is, path& p);
// [path.factory], path factory functions
template <class Source>
path u8path(const Source& source);
template <class InputIterator>
path u8path(InputIterator first, InputIterator last);
// [class.filesystem_error], filesystem errors
class filesystem_error;
// [class.directory_entry], directory entries
class directory_entry;
// [class.directory_iterator], directory iterators
class directory_iterator;
// [directory_iterator.nonmembers], range access for directory iterators
directory_iterator begin(directory_iterator iter) noexcept;
directory_iterator end(const directory_iterator&) noexcept;
// [class.rec.dir.itr], recursive directory iterators
class recursive_directory_iterator;
// [rec.dir.itr.nonmembers], range access for recursive directory iterators
recursive_directory_iterator begin(recursive_directory_iterator iter) noexcept;
recursive_directory_iterator end(const recursive_directory_iterator&) noexcept;
// [class.file_status], file status
class file_status;
struct space_info {
uintmax_t capacity;
uintmax_t free;
uintmax_t available;
};
// [fs.enum], enumerations
enum class file_type;
enum class perms;
enum class copy_options;
enum class directory_options;
using file_time_type = chrono::time_point<trivial-clock>;
// [fs.op.funcs], filesystem operations
path absolute(const path& p, const path& base = current_path());
path canonical(const path& p, const path& base = current_path());
path canonical(const path& p, error_code& ec);
path canonical(const path& p, const path& base, error_code& ec);
void copy(const path& from, const path& to);
void copy(const path& from, const path& to, error_code& ec) noexcept;
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) noexcept;
bool copy_file(const path& from, const path& to);
bool copy_file(const path& from, const path& to, error_code& ec) noexcept;
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) noexcept;
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) noexcept;
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 exists(file_status s) noexcept;
bool exists(const path& p);
bool exists(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;
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) noexcept;
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);
void permissions(const path& p, perms prms, 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) noexcept;
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 system_complete(const path& p);
path system_complete(const path& p, error_code& ec);
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);
}
trivial-clock is an implementation-defined type that satisfies the TrivialClock requirements ([time.clock.req]) and that is capable of representing and measuring file time values. Implementations should ensure that the resolution and range of file_time_type reflect the operating system dependent resolution and range of file time values.
Filesystem library functions often provide two overloads, one that throws an exception to report file system errors, and another that sets an error_code. [ Note: This supports two common use cases:
Uses where file system errors are truly exceptional and indicate a serious failure. Throwing an exception is an appropriate response.
Uses where file system errors are routine and do not necessarily represent failure. Returning an error code is the most appropriate response. This allows application specific error handling, including simply ignoring the error.
— end note ]
Functions not having an argument of type error_code& handle errors as follows, unless otherwise specified:
When a call by the implementation to an operating system or other underlying API results in an error that prevents the function from meeting its specifications, an exception of type filesystem_error shall be thrown. For functions with a single path argument, that argument shall be passed to the filesystem_error constructor with a single path argument. For functions with two path arguments, the first of these arguments shall be passed to the filesystem_error constructor as the path1 argument, and the second shall be passed as the path2 argument. The filesystem_error constructor's error_code argument is set as appropriate for the specific operating system dependent error.
Failure to allocate storage is reported by throwing an exception as described in [res.on.exception.handling].
Destructors throw nothing.
Functions having an argument of type error_code& handle errors as follows, unless otherwise specified:
If a call by the implementation to an operating system or other underlying API results in an error that prevents the function from meeting its specifications, the error_code& argument is set as appropriate for the specific operating system dependent error. Otherwise, clear() is called on the error_code& argument.
An object of class path represents a path ([fs.def.path]) and contains a pathname ([fs.def.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.
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;
// [path.construct], constructors and destructor
path() noexcept;
path(const path& p);
path(path&& p) noexcept;
path(string_type&& source);
template <class Source>
path(const Source& source);
template <class InputIterator>
path(InputIterator first, InputIterator last);
template <class Source>
path(const Source& source, const locale& loc);
template <class InputIterator>
path(InputIterator first, InputIterator last, const locale& loc);
~path();
// [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);
// [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);
// [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);
// [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;
// [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::string u8string() const;
std::u16string u16string() const;
std::u32string u32string() const;
// [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::string generic_u8string() const;
std::u16string generic_u16string() const;
std::u32string generic_u32string() const;
// [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;
// [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;
// [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;
// [path.gen], generation
path lexically_normal() const;
path lexically_relative(const path& base) const;
path lexically_proximate(const path& base) const;
// [path.itr], iterators
class iterator;
using const_iterator = iterator;
iterator begin() const;
iterator end() const;
private:
string_type pathstring; // exposition only
};
}
value_type is a typedef for the operating system dependent encoded character type used to represent pathnames.
The value of preferred_separator is the operating system dependent preferred-separator character ([path.generic]).
[ Example: 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 ]
pathname: root-name root-directoryopt relative-pathopt root-directory relative-pathopt relative-path
root-name: An operating system dependent name that identifies the starting location for absolute paths. [ Note: Many operating systems define a name beginning with two directory-separator characters as a root-name that identifies network or other resource locations. Some operating systems define a single letter followed by a colon as a drive specifier – a root-name identifying a specific device such as a disk drive. — end note ]
root-directory: directory-separator
relative-path: filename relative-path directory-separator relative-path directory-separator filename
filename: name dot dot-dot
name: A sequence of characters other than directory-separator characters. [ Note: Operating systems often place restrictions on the characters that may be used in a filename. For wide portability, users may wish to limit filename characters to the POSIX Portable Filename Character Set:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 . _ - — end note ]
dot: The filename consisting solely of a single period character (.).
dot-dot: The filename consisting solely of two period characters (..).
directory-separator: slash slash directory-separator preferred-separator preferred-separator directory-separator
preferred-separator: An operating system dependent directory separator character. May be a synonym for slash.
slash: The slash character (/).
Multiple successive directory-separator characters are considered to be the same as one directory-separator character.
The filename dot is treated as a reference to the current directory. The filename dot-dot is treated as a reference to the parent directory. What the filename dot-dot refers to relative to root-directory is implementation-defined. Specific filenames may have special meanings for a particular operating system.
[ Note: The format conversions described in this section are not applied on POSIX- or Windows-based operating systems because on these systems:
The generic format is acceptable as a native path.
There is no need to distinguish between native format and generic format in function arguments.
Paths for regular files and paths for directories share the same syntax.
— end note ]
Function arguments that take character sequences representing paths may use the generic pathname format grammar ([path.generic]) or the native pathname format ([fs.def.native]). If and only if such arguments are in the generic format and the generic format is not acceptable to the operating system as a native path, conversion to native format shall be performed during the processing of the argument.
[ Note: Some operating systems may have no unambiguous way to distinguish between native format and generic format arguments. This is by design as it simplifies use for operating systems that do not require disambiguation. An implementation for an operating system where disambiguation is required is permitted to distinguish between the formats. — end note ]
If the native format requires paths for regular files to be formatted differently from paths for directories, the path shall be treated as a directory path if its last element is a directory-separator, otherwise it shall be treated as a path to a regular file.
For member function arguments that take character sequences representing paths and for member functions returning strings, value type and encoding conversion is performed if the value type of the argument or return value differs from path::value_type. For the argument or return value, the method of conversion and the encoding to be converted to is determined by its value type:
char: The encoding is the native narrow encoding ([fs.def.native.encode]). The method of conversion, if any, is operating system dependent. [ Note: For POSIX-based operating systems path::value_type is char so no conversion from char value type arguments or to char value type return values is performed. For Windows-based operating systems, the native narrow encoding is determined by calling a Windows API function. — end note ] [ Note: This results in behavior identical to other C and C++ standard library functions that perform file operations using narrow character strings to identify paths. Changing this behavior would be surprising and error prone. — end note ]
wchar_t: The encoding is the native wide encoding ([fs.def.native.encode]). The method of conversion is unspecified. [ Note: For Windows-based operating systems path::value_type is wchar_t so no conversion from wchar_t value type arguments or to wchar_t value type return values is performed. — end note ]
char16_t: The encoding is UTF-16. The method of conversion is unspecified.
char32_t: The encoding is UTF-32. The method of conversion is unspecified.
If the encoding being converted to has no representation for source characters, the resulting converted characters, if any, are unspecified.
In addition to the requirements ([fs.req]), function template parameters named Source shall be one of:
basic_string<EcharT, traits, Allocator>. A function argument const Source& source shall have an effective range [source.begin(), source.end()).
basic_string_view<EcharT, traits>. A function argument const Source& source shall have an effective range [source.begin(), source.end()).
A type meeting the input iterator requirements that iterates over a NTCTS. The value type shall be an encoded character type. A function argument const Source& source shall have an effective range [source, end) where end is the first iterator value with an element value equal to iterator_traits<Source>::value_type().
A character array that after array-to-pointer decay results in a pointer to the start of a NTCTS. The value type shall be an encoded character type. A function argument const Source& source shall have an effective range [source, end) where end is the first iterator value with an element value equal to iterator_traits<decay_t<Source>>::value_type().
Functions taking template parameters named Source shall not participate in overload resolution unless either Source is a specialization of basic_string or basic_string_view or the qualified-id iterator_traits<decay_t<Source>>::value_type is valid and denotes a possibly const encoded character type ([temp.deduct]).
[ Note: See path conversions ([path.cvt]) for how the value types above and their encodings convert to path::value_type and its encoding. — end note ]
Arguments of type Source shall not be null pointers.
Effects: Constructs an object of class path.
Postconditions: empty() == true.
path(const path& p);
path(path&& p) noexcept;
Effects: Constructs an object of class path with pathstring having the original value of p.pathstring. In the second form, p is left in a valid but unspecified state.
Effects: Constructs an object of class path with pathstring having the original value of source. source is left in a valid but unspecified state.
template <class Source>
path(const Source& source);
template <class InputIterator>
path(InputIterator first, InputIterator last);
Effects: Constructs an object of class path, storing the effective range of source ([path.req]) or the range [first, last) in pathstring, converting format and encoding if required ([path.cvt]).
template <class Source>
path(const Source& source, const locale& loc);
template <class InputIterator>
path(InputIterator first, InputIterator last, const locale& loc);
Requires: The value type of Source and InputIterator is char.
Effects: Constructs an object of class path, storing the effective range of source or the range [first, last) in pathstring, after converting format if required and after converting the encoding as follows:
If value_type is wchar_t, converts to the native wide encoding ([fs.def.native.encode]) using the codecvt<wchar_t, char, mbstate_t> facet of loc.
Otherwise a conversion is performed using the codecvt<wchar_t, char, mbstate_t> facet of loc, and then a second conversion to the current narrow encoding.
[ Example: A string is to be read from a database that is encoded in ISO/IEC 8859-1, and used to create a directory:
namespace fs = std::filesystem; std::string latin1_string = read_latin1_data(); codecvt_8859_1<wchar_t> latin1_facet; std::locale latin1_locale(std::locale(), latin1_facet); fs::create_directory(fs::path(latin1_string, latin1_locale));
For POSIX-based operating systems, the path is constructed by first using latin1_facet to convert ISO/IEC 8859-1 encoded latin1_string to a wide character string in the native wide encoding ([fs.def.native.encode]). The resulting wide string is then converted to a narrow character pathstring string in the current native narrow encoding. If the native wide encoding is UTF-16 or UTF-32, and the current native narrow encoding is UTF-8, all of the characters in the ISO/IEC 8859-1 character set will be converted to their Unicode representation, but for other native narrow encodings some characters may have no representation.
For Windows-based operating systems, the path is constructed by using latin1_facet to convert ISO/IEC 8859-1 encoded latin1_string to a UTF-16 encoded wide character pathstring string. All of the characters in the ISO/IEC 8859-1 character set will be converted to their Unicode representation. — end example ]
path& operator=(const path& p);
Effects: If *this and p are the same object, has no effect. Otherwise, modifies pathstring to have the original value of p.pathstring.
Returns: *this.
path& operator=(path&& p) noexcept;
Effects: If *this and p are the same object, has no effect. Otherwise, modifies pathstring to have the original value of p.pathstring. p is left in a valid but unspecified state. [ Note: A valid implementation is swap(p). — end note ]
Returns: *this.
path& operator=(string_type&& source);
path& assign(string_type&& source);
Effects: Modifies pathstring to have the original value of source. source is left in a valid but unspecified state.
Returns: *this.
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);
Effects: Stores the effective range of source ([path.req]) or the range [first, last) in pathstring, converting format and encoding if required ([path.cvt]).
Returns: *this.
The append operations use operator/= to denote their semantic effect of appending preferred-separator when needed.
Requires: !p.has_root_name().
Effects: Appends path::preferred_separator to pathstring unless:
an added directory-separator would be redundant, or
an added directory-separator would change a relative path into an absolute path [ Note: An empty path is relative. — end note ], or
p.empty() is true, or
*p.native().cbegin() is a directory-separator.
Then appends p.native() to pathstring.
Returns: *this.
template <class Source>
path& operator/=(const Source& source);
template <class Source>
path& append(const Source& source);
Effects: Equivalent to: return operator/=(path(source));
template <class InputIterator>
path& append(InputIterator first, InputIterator last);
Effects: Equivalent to: return operator/=(path(first, last));
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);
Postconditions: native() == prior_native + effective-argument, where prior_native is native() prior to the call to operator+=, and effective-argument is:
if x is present and is const path&, x.native(); otherwise,
if source is present, the effective range of source ([path.req]); otherwise,
if first and last are present, the range [first, last); otherwise,
x.
If the value type of effective-argument would not be path::value_type, the actual argument or argument range is first converted ([path.type.cvt]) so that effective-argument has value type path::value_type.
Returns: *this.
Postconditions: empty() == true.
Effects: Each directory-separator is converted to preferred-separator.
Returns: *this.
[ Example:
path p("foo/bar");
std::cout << p << '\n';
p.make_preferred();
std::cout << p << '\n';
On an operating system where preferred-separator is the same as directory-separator, the output is:
"foo/bar" "foo/bar"
On an operating system where preferred-separator is a backslash, the output is:
"foo/bar" "foo\bar"
— end example ]
Postconditions: !has_filename().
Returns: *this.
[ Example:
std::cout << path("/foo").remove_filename(); // outputs "/"
std::cout << path("/").remove_filename(); // outputs ""
— end example ]
path& replace_filename(const path& replacement);
Effects: Equivalent to:
remove_filename(); operator/=(replacement);
Returns: *this.
[ Example:
std::cout << path("/").replace_filename("bar"); // outputs "bar"
— end example ]
path& replace_extension(const path& replacement = path());
Effects: pathstring (the stored path) is modified as follows:
Any existing extension()([path.decompose]) is removed from the stored path, then
If replacement is not empty and does not begin with a dot character, a dot character is appended to the stored path, then
replacement is concatenated to the stored path.
Returns: *this.
void swap(path& rhs) noexcept;
Effects: Swaps the contents of the two paths pathstring and rhs.pathstring.
Complexity: Constant time.
The string returned by all native format observers is in the native pathname format ([fs.def.native]).
Returns: pathstring.
const value_type* c_str() const noexcept;
Returns: pathstring.c_str().
Returns: pathstring.
[ Note: Conversion to string_type is provided so that an object of class path can be given as an argument to existing standard library file stream constructors and open functions. — end note ]
template <class EcharT, class traits = char_traits<EcharT>,
class Allocator = allocator<EcharT>>
basic_string<EcharT, traits, Allocator>
string(const Allocator& a = Allocator()) const;
Returns: pathstring.
Remarks: All memory allocation, including for the return value, shall be performed by a. Conversion, if any, is specified by [path.cvt].
std::string string() const;
std::wstring wstring() const;
std::string u8string() const;
std::u16string u16string() const;
std::u32string u32string() const;
Returns: pathstring.
Remarks: Conversion, if any, is performed as specified by [path.cvt]. The encoding of the string returned by u8string() is always UTF-8.
Generic format observer functions return strings formatted according to the generic pathname format ([path.generic]). The forward slash ('/') character is used as the directory-separator character.
[ Example: On an operating system that uses backslash as its preferred-separator, path("foo\\bar").generic_string() returns "foo/bar". — end example ]
template <class EcharT, class traits = char_traits<EcharT>,
class Allocator = allocator<EcharT>>
basic_string<EcharT, traits, Allocator>
generic_string(const Allocator& a = Allocator()) const;
Returns: pathstring, reformatted according to the generic pathname format ([path.generic]).
Remarks: All memory allocation, including for the return value, shall be performed by a. Conversion, if any, is specified by [path.cvt].
std::string generic_string() const;
std::wstring generic_wstring() const;
std::string generic_u8string() const;
std::u16string generic_u16string() const;
std::u32string generic_u32string() const;
Returns: pathstring, reformatted according to the generic pathname format ([path.generic]).
Remarks: Conversion, if any, is specified by [path.cvt]. The encoding of the string returned by generic_u8string() is always UTF-8.
int compare(const path& p) const noexcept;
Returns:
A value less than 0, if native() for the elements of *this are lexicographically less than native() for the elements of p; otherwise,
a value greater than 0, if native() for the elements of *this are lexicographically greater than native() for the elements of p; otherwise,
0.
Remarks: The elements are determined as if by iteration over the half-open range [begin(), end()) for *this and p.
int compare(const string_type& s) const
int compare(basic_string_view<value_type> s) const;
Returns: compare(path(s)).
int compare(const value_type* s) const
Returns: compare(path(s)).
Returns: root-directory, if pathstring includes root-directory, otherwise path().
Returns: root_name() / root_directory().
Returns: A path composed from pathstring, if !empty(), beginning with the first filename after root-path. Otherwise, path().
Returns: (empty() || begin() == --end()) ? path() : pp, where pp is constructed as if by starting with an empty path and successively applying operator/= for each element in the range [begin(), --end()).
Returns: empty() ? path() : *--end().
[ Example:
std::cout << path("/foo/bar.txt").filename(); // outputs "bar.txt"
std::cout << path("/").filename(); // outputs "/"
std::cout << path(".").filename(); // outputs "."
std::cout << path("..").filename(); // outputs ".."
— end example ]
Returns: if filename() contains a period but does not consist solely of one or two periods, returns the substring of filename() starting at its beginning and ending with the character before the last period. Otherwise, returns filename().
[ Example:
std::cout << path("/foo/bar.txt").stem(); // outputs "bar"
path p = "foo.bar.baz.tar";
for (; !p.extension().empty(); p = p.stem())
std::cout << p.extension() << '\n';
// outputs: .tar
// .baz
// .bar
— end example ]
Returns: if filename() contains a period but does not consist solely of one or two periods, returns the substring of filename() starting at the rightmost period and for the remainder of the path. Otherwise, returns an empty path object.
Remarks: Implementations are permitted to define additional behavior for file systems which append additional elements to extensions, such as alternate data streams or partitioned dataset names.
[ Example:
std::cout << path("/foo/bar.txt").extension(); // outputs ".txt"
— end example ]
[ Note: The period is included in the return value so that it is possible to distinguish between no extension and an empty extension. Also note that for a path p, p.stem()+p.extension() == p.filename(). — end note ]
Returns: pathstring.empty().
Returns: !root_path().empty().
Returns: !root_name().empty().
bool has_root_directory() const;
Returns: !root_directory().empty().
bool has_relative_path() const;
Returns: !relative_path().empty().
Returns: !parent_path().empty().
Returns: !filename().empty().
Returns: !stem().empty().
Returns: !extension().empty().
Returns: true if pathstring contains an absolute path ([fs.def.absolute.path]), else false.
[ Example: path("/").is_absolute() is true for POSIX-based operating systems, and false for Windows-based operating systems. — end example ]
Returns: !is_absolute().
path lexically_normal() const;
Returns: *this in normal form ([fs.def.normal.form]).
[ Example:
assert(path("foo/./bar/..").lexically_normal() == "foo");
assert(path("foo/.///bar/../").lexically_normal() == "foo/.");
The above assertions will succeed. The second example ends with a current directory (dot) element appended to support operating systems that use different syntax for directory names and regular file names.
On Windows, the returned path's directory-separator characters will be backslashes rather than slashes, but that does not affect path equality. — end example ]
path lexically_relative(const path& base) const;
Returns: *this made relative to base. Does not resolve ([fs.def.pathres]) symlinks. Does not first normalize ([fs.def.normal.form]) *this or base.
Effects: Determines the first mismatched element of *this and base as if by:
auto [a, b] = mismatch(begin(), end(), base.begin(), base.end());
Then,
if a == begin() and b == base.begin(), returns path(); otherwise
if a == end() and b == base.end(), returns path("."); otherwise
returns an object of class path that is default-constructed, followed by
application of operator/=(path("..")) for each element in [b, base.end()), and then
application of operator/= for each element in [a, end()).
[ Example:
assert(path("/a/d").lexically_relative("/a/b/c") == "../../d");
assert(path("/a/b/c").lexically_relative("/a/d") == "../b/c");
assert(path("a/b/c").lexically_relative("a") == "b/c");
assert(path("a/b/c").lexically_relative("a/b/c/x/y") == "../..");
assert(path("a/b/c").lexically_relative("a/b/c") == ".");
assert(path("a/b").lexically_relative("c/d") == "");
The above assertions will succeed. On Windows, the returned path's directory-separator characters will be backslashes rather than forward slashes, but that does not affect path equality. — end example ]
[ Note: If symlink following semantics are desired, use the operational function relative(). — end note ]
[ Note: If normalization ([fs.def.normal.form]) is needed to ensure consistent matching of elements, apply lexically_normal() to *this, base, or both. — end note ]
path lexically_proximate(const path& base) const;
Returns: If the value of lexically_relative(base) is not an empty path, return it. Otherwise return *this.
[ Note: If symlink following semantics are desired, use the operational function proximate(). — end note ]
[ Note: If normalization ([fs.def.normal.form]) is needed to ensure consistent matching of elements, apply lexically_normal() to *this, base, or both. — end note ]
Path iterators iterate over the elements of pathstring in the generic format ([path.generic]).
A path::iterator is a constant iterator satisfying all the requirements of a bidirectional iterator ([bidirectional.iterators]) except that, for dereferenceable iterators a and b of type path::iterator with a == b, there is no requirement that *a and *b are bound to the same object. Its value_type is path.
Calling any non-const member function of a path object invalidates all iterators referring to elements of that object.
For the elements of pathstring in the generic format, the forward traversal order is as follows:
The root-name element, if present.
The root-directory element, if present. [ Note: the generic format is required to ensure lexicographical comparison works correctly. — end note ]
Each successive filename element, if present.
dot, if one or more trailing non-root slash characters are present.
Returns: An iterator for the first present element in the traversal list above. If no elements are present, the end iterator.
Returns: The end iterator.
void swap(path& lhs, path& rhs) noexcept;
Effects: Equivalent to: lhs.swap(rhs);
size_t hash_value (const path& p) noexcept;
Returns: A hash value for the path p. If for two paths, p1 == p2 then hash_value(p1) == hash_value(p2).
bool operator< (const path& lhs, const path& rhs) noexcept;
Returns: lhs.compare(rhs) < 0.
bool operator<=(const path& lhs, const path& rhs) noexcept;
Returns: !(rhs < lhs).
bool operator> (const path& lhs, const path& rhs) noexcept;
Returns: rhs < lhs.
bool operator>=(const path& lhs, const path& rhs) noexcept;
Returns: !(lhs < rhs).
bool operator==(const path& lhs, const path& rhs) noexcept;
[ Note: Path equality and path equivalence have different semantics.
Equality is determined by the path non-member operator==, which considers the two path's lexical representations only. Thus path("foo") == "bar" is never true.
Equivalence is determined by the equivalent() non-member function, which determines if two paths resolve ([fs.def.pathres]) to the same file system entity. Thus equivalent("foo", "bar") will be true when both paths resolve to the same file.
Programmers wishing to determine if two paths are “the same” must decide if “the same” means “the same representation” or “resolve to the same actual file”, and choose the appropriate function accordingly. — end note ]
bool operator!=(const path& lhs, const path& rhs) noexcept;
Returns: !(lhs == rhs).
path operator/ (const path& lhs, const path& rhs);
Effects: Equivalent to: return path(lhs) /= rhs;
template <class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, const path& p);
Effects: Equivalent to: os << quoted(p.string<charT, traits>()); [ Note: The quoted function is described in [quoted.manip]. — end note ]
Returns: os.
template <class charT, class traits>
basic_istream<charT, traits>&
operator>>(basic_istream<charT, traits>& is, path& p);
Effects: Equivalent to:
basic_string<charT, traits> tmp; is >> quoted(tmp); p = tmp;
Returns: is.
template <class Source>
path u8path(const Source& source);
template <class InputIterator>
path u8path(InputIterator first, InputIterator last);
Requires: The source and [first, last) sequences are UTF-8 encoded. The value type of Source and InputIterator is char.
Returns:
If value_type is char and the current native narrow encoding ([fs.def.native.encode]) is UTF-8, return path(source) or path(first, last); otherwise,
if value_type is wchar_t and the native wide encoding is UTF-16, or if value_type is char16_t or char32_t, convert source or [first, last) to a temporary, tmp, of type string_type and return path(tmp); otherwise,
convert source or [first, last) to a temporary, tmp, of type u32string and return path(tmp).
Remarks: Argument format conversion ([path.fmt.cvt]) applies to the arguments for these functions. How Unicode encoding conversions are performed is unspecified.
[ Example: A string is to be read from a database that is encoded in UTF-8, and used to create a directory using the native encoding for filenames:
namespace fs = std::filesystem; std::string utf8_string = read_utf8_data(); fs::create_directory(fs::u8path(utf8_string));
For POSIX-based operating systems with the native narrow encoding set to UTF-8, no encoding or type conversion occurs.
For POSIX-based operating systems with the native narrow encoding not set to UTF-8, a conversion to UTF-32 occurs, followed by a conversion to the current native narrow encoding. Some Unicode characters may have no native character set representation.
For Windows-based operating systems a conversion from UTF-8 to UTF-16 occurs. — end example ]
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;
};
}
The class filesystem_error defines the type of objects thrown as exceptions to report file system errors from functions described in this subclause.
Constructors are provided that store zero, one, or two paths associated with an error.
Postconditions: The postconditions of this function are indicated in Table [tab:filesystem_error.1].
| Expression | Value |
| runtime_error::what() | what_arg.c_str() |
| code() | ec |
| path1().empty() | true |
| path2().empty() | true |
filesystem_error(const string& what_arg, const path& p1, error_code ec);
Postconditions: The postconditions of this function are indicated in Table [tab:filesystem_error.2].
| Expression | Value |
| runtime_error::what() | what_arg.c_str() |
| code() | ec |
| path1() | Reference to stored copy of p1 |
| path2().empty() | true |
filesystem_error(const string& what_arg, const path& p1, const path& p2, error_code ec);
Postconditions: The postconditions of this function are indicated in Table [tab:filesystem_error.3].
| Expression | Value |
| runtime_error::what() | what_arg.c_str() |
| code() | ec |
| path1() | Reference to stored copy of p1 |
| path2() | Reference to stored copy of p2 |
const path& path1() const noexcept;
Returns: A reference to the copy of p1 stored by the constructor, or, if none, an empty path.
const path& path2() const noexcept;
Returns: A reference to the copy of p2 stored by the constructor, or, if none, an empty path.
const char* what() const noexcept override;
Returns: A string containing runtime_error::what(). The exact format is unspecified. Implementations are encouraged but not required to include path1.native_string() if not empty, path2.native_string() if not empty, and system_error::what() strings in the returned string.
This enum class specifies constants used to identify file types, with the meanings listed in Table [tab:enum.file_type].
The enum class type copy_options is a bitmask type ([bitmask.types]) that specifies bitmask constants used to control the semantics of copy operations. The constants are specified in option groups with the meanings listed in Table [tab:enum.copy_options]. Constant none is shown in each option group for purposes of exposition; implementations shall provide only a single definition. Calling a library function with more than a single constant for an option group results in undefined behavior.
| Option group controlling copy_file function effects for existing target files | |
| Constant | Meaning |
| none | (Default) Error; file already exists. |
| skip_existing | Do not overwrite existing file, do not report an error. |
| overwrite_existing | Overwrite the existing file. |
| update_existing | Overwrite the existing file if it is older than the replacement file. |
| Option group controlling copy function effects for sub-directories | |
| Constant | Meaning |
| none | (Default) Do not copy sub-directories. |
| recursive | Recursively copy sub-directories and their contents. |
| Option group controlling copy function effects for symbolic links | |
| Constant | Meaning |
| none | (Default) Follow symbolic links. |
| copy_symlinks | Copy symbolic links as symbolic links rather than copying the files that they point to. |
| skip_symlinks | Ignore symbolic links. |
| Option group controlling copy function effects for choosing the form of copying | |
| Constant | Meaning |
| none | (Default) Copy content. |
| directories_only | Copy directory structure only, do not copy non-directory files. |
| create_symlinks | Make symbolic links instead of copies of files. The source path shall be an absolute path unless the destination path is in the current directory. |
| create_hard_links | Make hard links instead of copies of files. |
The enum class type perms is a bitmask type ([bitmask.types]) that specifies bitmask constants used to identify file permissions, with the meanings listed in Table [tab:enum.perms].
| Name | Value | POSIX | Definition or notes |
| (octal) | macro | ||
| none | 0 | There are no permissions set for the file. | |
| owner_read | 0400 | S_IRUSR | Read permission, owner |
| owner_write | 0200 | S_IWUSR | Write permission, owner |
| owner_exec | 0100 | S_IXUSR | Execute/search permission, owner |
| owner_all | 0700 | S_IRWXU |
Read, write, execute/search by owner; owner_read | owner_write | owner_exec |
| group_read | 040 | S_IRGRP | Read permission, group |
| group_write | 020 | S_IWGRP | Write permission, group |
| group_exec | 010 | S_IXGRP | Execute/search permission, group |
| group_all | 070 | S_IRWXG |
Read, write, execute/search by group; group_read | group_write | group_exec |
| others_read | 04 | S_IROTH | Read permission, others |
| others_write | 02 | S_IWOTH | Write permission, others |
| others_exec | 01 | S_IXOTH | Execute/search permission, others |
| others_all | 07 | S_IRWXO |
Read, write, execute/search by others; others_read | others_write | others_exec |
| all | 0777 | owner_all | group_all | others_all | |
| set_uid | 04000 | S_ISUID | Set-user-ID on execution |
| set_gid | 02000 | S_ISGID | Set-group-ID on execution |
| sticky_bit | 01000 | S_ISVTX | Operating system dependent. |
| mask | 07777 | all | set_uid | set_gid | sticky_bit | |
| unknown | 0xFFFF | The permissions are not known, such as when a file_status object is created without specifying the permissions | |
| add_perms | 0x10000 | permissions() shall bitwise or the perm argument's permission bits to the file's current permission bits. | |
| remove_perms | 0x20000 | permissions() shall bitwise and the complement of perm argument's permission bits to the file's current permission bits. | |
| symlink_nofollow | 0x40000 | permissions() shall change the permissions of symbolic links. |
The enum class type directory_options is a bitmask type ([bitmask.types]) that specifies bitmask constants used to identify directory traversal options, with the meanings listed in Table [tab:enum.directory_options].
| Name | Meaning |
| none | (Default) Skip directory symlinks, permission denied is an error. |
| follow_directory_symlink | Follow rather than skip directory symlinks. |
| skip_permission_denied | Skip directories that would otherwise result in permission denied. |
namespace std::filesystem {
class file_status {
public:
// [file_status.cons], constructors and destructor
explicit file_status(file_type ft = file_type::none,
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;
// [file_status.mods], modifiers
void type(file_type ft) noexcept;
void permissions(perms prms) noexcept;
// [file_status.obs], observers
file_type type() const noexcept;
perms permissions() const noexcept;
};
}
An object of type file_status stores information about the type and permissions of a file.
explicit file_status() noexcept;
Postconditions: type() == file_type::none and permissions() == perms::unknown.
explicit file_status(file_type ft, perms prms = perms::unknown) noexcept;
Postconditions: type() == ft and permissions() == prms.
file_type type() const noexcept;
Returns: The value of type() specified by the postconditions of the most recent call to a constructor, operator=, or type(file_type) function.
perms permissions() const noexcept;
Returns: The value of permissions() specified by the postconditions of the most recent call to a constructor, operator=, or permissions(perms) function.
void type(file_type ft) noexcept;
Postconditions: type() == ft.
void permissions(perms prms) noexcept;
Postconditions: permissions() == prms.
namespace std::filesystem {
class directory_entry {
public:
// [directory_entry.cons], constructors and destructor
explicit directory_entry(const path& p);
directory_entry() noexcept = default;
directory_entry(const directory_entry&) = default;
directory_entry(directory_entry&&) noexcept = default;
~directory_entry();
// assignments:
directory_entry& operator=(const directory_entry&) = default;
directory_entry& operator=(directory_entry&&) noexcept = default;
// [directory_entry.mods], modifiers
void assign(const path& p);
void replace_filename(const path& p);
// [directory_entry.obs], observers
const path& path() const noexcept;
operator const path&() 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;
bool operator==(const directory_entry& rhs) const noexcept;
bool operator!=(const directory_entry& rhs) const noexcept;
bool operator<=(const directory_entry& rhs) const noexcept;
bool operator> (const directory_entry& rhs) const noexcept;
bool operator>=(const directory_entry& rhs) const noexcept;
private:
path pathobject; // exposition only
};
}
A directory_entry object stores a path object.
explicit directory_entry(const path& p);
Effects: Constructs an object of type directory_entry.
Postconditions: path() == p.
Postconditions: path() == p.
void replace_filename(const path& p);
Postconditions: path() == x.parent_path() / p where x is the value of path() before the function is called.
const path& path() const noexcept;
operator const path&() const noexcept;
Returns: pathobject.
file_status status() const;
file_status status(error_code& ec) const noexcept;
Returns: status(path()) or status(path(), ec), respectively.
Throws: As specified in [fs.err.report].
file_status symlink_status() const;
file_status symlink_status(error_code& ec) const noexcept;
Returns: symlink_status(path()) or symlink_status(path(), ec), respectively.
Throws: As specified in [fs.err.report].
bool operator==(const directory_entry& rhs) const noexcept;
Returns: pathobject == rhs.pathobject.
bool operator!=(const directory_entry& rhs) const noexcept;
Returns: pathobject != rhs.pathobject.
bool operator< (const directory_entry& rhs) const noexcept;
Returns: pathobject < rhs.pathobject.
bool operator<=(const directory_entry& rhs) const noexcept;
Returns: pathobject <= rhs.pathobject.
bool operator> (const directory_entry& rhs) const noexcept;
Returns: pathobject > rhs.pathobject.
bool operator>=(const directory_entry& rhs) const noexcept;
Returns: pathobject >= rhs.pathobject.
An object of type directory_iterator provides an iterator for a sequence of directory_entry elements representing the files in a directory. [ Note: For iteration into sub-directories, see class recursive_directory_iterator ([class.rec.dir.itr]). — end note ]
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&;
// [directory_iterator.members], 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) noexcept;
directory_iterator(const path& p, directory_options options,
error_code& ec) noexcept;
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) noexcept;
// other members as required by [input.iterators], input iterators
};
}
directory_iterator satisfies the requirements of an input iterator ([input.iterators]).
If an iterator of type directory_iterator reports an error or is advanced past the last directory element, that iterator shall become equal to the end iterator value. The directory_iterator default constructor shall create an iterator equal to the end iterator value, and this shall be the only valid iterator for the end condition.
The end iterator is not dereferenceable.
Two end iterators are always equal. An end iterator shall not be equal to a non-end iterator.
The result of calling the path() member of the directory_entry object obtained by dereferencing a directory_iterator is a reference to a path object composed of the directory argument from which the iterator was constructed with filename of the directory entry appended as if by operator/=.
Directory iteration shall not yield directory entries for the current (dot) and parent (dot-dot) directories.
The order of directory entries obtained by dereferencing successive increments of a directory_iterator is unspecified.
[ Note: Programs performing directory iteration may wish to test if the path obtained by dereferencing a directory iterator actually exists. It could be a symbolic link to a non-existent file. Programs recursively walking directory trees for purposes of removing and renaming entries may wish to avoid following symbolic links.
If a file is removed from or added to a directory after the construction of a directory_iterator for the directory, it is unspecified whether or not subsequently incrementing the iterator will ever result in an iterator referencing the removed or added directory entry. See POSIX readdir_r. — end note ]
directory_iterator() noexcept;
Effects: Constructs the end iterator.
explicit directory_iterator(const path& p);
directory_iterator(const path& p, directory_options options);
directory_iterator(const path& p, error_code& ec) noexcept;
directory_iterator(const path& p, directory_options options, error_code& ec) noexcept;
Effects: For the directory that p resolves to, constructs an iterator for the first element in a sequence of directory_entry elements representing the files in the directory, if any; otherwise the end iterator. However, if
(options & directory_options::skip_permission_denied) != directory_options::none
and construction encounters an error indicating that permission to access p is denied, constructs the end iterator and does not report an error.
Throws: As specified in [fs.err.report].
[ Note: To iterate over the current directory, use directory_iterator(".") rather than directory_iterator(""). — end note ]
directory_iterator(const directory_iterator& rhs);
directory_iterator(directory_iterator&& rhs) noexcept;
Effects: Constructs an object of class directory_iterator.
Postconditions: *this has the original value of rhs.
directory_iterator& operator=(const directory_iterator& rhs);
directory_iterator& operator=(directory_iterator&& rhs) noexcept;
Effects: If *this and rhs are the same object, the member has no effect.
Postconditions: *this has the original value of rhs.
Returns: *this.
directory_iterator& operator++();
directory_iterator& increment(error_code& ec) noexcept;
Effects: As specified for the prefix increment operation of Input iterators ([input.iterators]).
Returns: *this.
Throws: As specified in [fs.err.report].
These functions enable range access for directory_iterator.
Returns: iter.
directory_iterator end(const directory_iterator&) noexcept;
Returns: directory_iterator().
An object of type recursive_directory_iterator provides an iterator for a sequence of directory_entry elements representing the files in a directory and its sub-directories.
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&;
// [rec.dir.itr.members], 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) noexcept;
recursive_directory_iterator(const path& p, error_code& ec) noexcept;
recursive_directory_iterator(const recursive_directory_iterator& rhs);
recursive_directory_iterator(recursive_directory_iterator&& rhs) noexcept;
~recursive_directory_iterator();
// [rec.dir.itr.members], observers
directory_options options() const;
int depth() const;
bool recursion_pending() const;
const directory_entry& operator*() const;
const directory_entry* operator->() const;
// [rec.dir.itr.members], 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) noexcept;
void pop();
void pop(error_code& ec);
void disable_recursion_pending();
// other members as required by [input.iterators], input iterators
};
}
Calling options, depth, recursion_pending, pop or disable_recursion_pending on an iterator that is not dereferenceable results in undefined behavior.
The behavior of a recursive_directory_iterator is the same as a directory_iterator unless otherwise specified.
[ Note: If the directory structure being iterated over contains cycles then the end iterator may be unreachable. — end note ]
recursive_directory_iterator() noexcept;
Effects: Constructs the end iterator.
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) noexcept;
recursive_directory_iterator(const path& p, error_code& ec) noexcept;
Effects: Constructs a iterator representing the first entry in the directory p resolves to, if any; otherwise, the end iterator. However, if
(options & directory_options::skip_permission_denied) != directory_options::none
and construction encounters an error indicating that permission to access p is denied, constructs the end iterator and does not report an error.
Postconditions: options() == options for the signatures with a directory_options argument, otherwise options() == directory_options::none.
Throws: As specified in [fs.err.report].
[ Note: To iterate over the current directory, use recursive_directory_iterator(".") rather than recursive_directory_iterator(""). — end note ]
[ Note: By default, recursive_directory_iterator does not follow directory symlinks. To follow directory symlinks, specify options as directory_options::follow_directory_symlink — end note ]
recursive_directory_iterator(const recursive_directory_iterator& rhs);
Effects: Constructs an object of class recursive_directory_iterator.
recursive_directory_iterator(recursive_directory_iterator&& rhs) noexcept;
Effects: Constructs an object of class recursive_directory_iterator.
Postconditions: options(), depth(), and recursion_pending() return the values that rhs.options(), rhs.depth(), and rhs.recursion_pending(), respectively, had before the function call.
recursive_directory_iterator& operator=(const recursive_directory_iterator& rhs);
Effects: If *this and rhs are the same object, the member has no effect.
Returns: *this.
recursive_directory_iterator& operator=(recursive_directory_iterator&& rhs) noexcept;
Effects: If *this and rhs are the same object, the member has no effect.
Postconditions: options(), depth(), and recursion_pending() return the values that rhs.options(), rhs.depth(), and rhs.recursion_pending(), respectively, had before the function call.
Returns: *this.
directory_options options() const;
Returns: The value of the constructor options argument, if present, otherwise directory_options::none.
Throws: Nothing.
Returns: The current depth of the directory tree being traversed. [ Note: The initial directory is depth 0, its immediate subdirectories are depth 1, and so forth. — end note ]
Throws: Nothing.
bool recursion_pending() const;
Returns: true if disable_recursion_pending() has not been called subsequent to the prior construction or increment operation, otherwise false.
Throws: Nothing.
recursive_directory_iterator& operator++();
recursive_directory_iterator& increment(error_code& ec) noexcept;
Effects: As specified for the prefix increment operation of Input iterators ([input.iterators]), except that:
If there are no more entries at the current depth, then if depth()!= 0 iteration over the parent directory resumes; otherwise *this = recursive_directory_iterator().
Otherwise if
recursion_pending() && is_directory((*this)->status()) && (!is_symlink((*this)->symlink_status()) || (options() & directory_options::follow_directory_symlink) != directory_options::none)
then either directory (*this)->path() is recursively iterated into or, if
(options() & directory_options::skip_permission_denied) != directory_options::none
and an error occurs indicating that permission to access directory (*this)->path() is denied, then directory (*this)->path() is treated as an empty directory and no error is reported.
Returns: *this.
Throws: As specified in [fs.err.report].
void pop();
void pop(error_code& ec);
Effects: If depth() == 0, set *this to recursive_directory_iterator(). Otherwise, cease iteration of the directory currently being iterated over, and continue iteration over the parent directory.
Throws: As specified in [fs.err.report].
void disable_recursion_pending();
Postconditions: recursion_pending() == false.
[ Note: disable_recursion_pending() is used to prevent unwanted recursion into a directory. — end note ]
These functions enable use of recursive_directory_iterator with range-based for statements.
recursive_directory_iterator begin(recursive_directory_iterator iter) noexcept;
Returns: iter.
recursive_directory_iterator end(const recursive_directory_iterator&) noexcept;
Returns: recursive_directory_iterator().
Filesystem operation functions query or modify files, including directories, in external storage.
[ Note: Because hardware failures, network failures, file system races ([fs.def.race]), and many other kinds of errors occur frequently in file system operations, users should be aware that any filesystem operation function, no matter how apparently innocuous, may encounter an error; see [fs.err.report]. — end note ]
path absolute(const path& p, const path& base = current_path());
Returns: An absolute path ([fs.def.absolute.path]) composed according to Table [tab:absolute.path].
| p.has_root_directory() | !p.has_root_directory() | |
| p.has_root_name() | p |
2.4in
p.root_name() / absolute(base).root_directory() / absolute(base).relative_path() / p.relative_path() |
| !p.has_root_name() | absolute(base).root_name() / p | absolute(base) / p |
[ Note: For the returned path, rp, rp.is_absolute() is true. — end note ]
Throws: As specified in [fs.err.report].
path canonical(const path& p, const path& base = current_path());
path canonical(const path& p, error_code& ec);
path canonical(const path& p, const path& base, error_code& ec);
Effects: Converts p, which must exist, to an absolute path that has no symbolic link, ".", or ".." elements.
Returns: A path that refers to the same file system object as absolute(p, base). For the overload without a base argument, base is current_path(). Signatures with argument ec return path() if an error occurs.
Throws: As specified in [fs.err.report].
Remarks: !exists(p) is an error.
void copy(const path& from, const path& to);
void copy(const path& from, const path& to, error_code& ec) noexcept;
Effects: Equivalent to copy(from, to, copy_options::none) or copy(from, to, copy_options::none, ec), respectively.
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) noexcept;
Requires: At most one constant from each option group ([enum.copy_options]) is present in options.
Effects: Before the first use of f and t:
If
(options & copy_options::create_symlinks) != copy_options::none || (options & copy_options::skip_symlinks) != copy_options::none
then auto f = symlink_status(from) and if needed auto t = symlink_status(to).
Otherwise, if
(options & copy_options::copy_symlinks) != copy_options::none
then auto f = symlink_status(from) and if needed auto t = status(to).
Otherwise, auto f = status(from) and if needed auto t = status(to).
Effects are then as follows:
An error is reported as specified in [fs.err.report] if:
!exists(f), or
equivalent(from, to), or
is_other(f) || is_other(t), or
is_directory(f) && is_regular_file(t).
Otherwise, if is_symlink(f), then:
If (options & copy_options::skip_symlinks) != copy_options::none then return.
Otherwise if
!exists(t) && (options & copy_options::copy_symlinks) != copy_options::none
then copy_symlink(from, to).
Otherwise report an error as specified in [fs.err.report].
Otherwise, if is_regular_file(f), then:
If (options & copy_options::directories_only) != copy_options::none, then return.
Otherwise if (options & copy_options::create_symlinks) != copy_options::none, then create a symbolic link to the source file.
Otherwise if (options & copy_options::create_hard_links) != copy_options::none, then create a hard link to the source file.
Otherwise if is_directory(t), then copy_file(from, to/from.filename(), options).
Otherwise, copy_file(from, to, options).
Otherwise, if
is_directory(f) && ((options & copy_options::recursive) != copy_options::none || options == copy_options::none)
then:
If !exists(t), then create_directory(to, from).
Then, iterate over the files in from, as if by for (const directory_entry& x : directory_iterator(from)), and for each iteration
copy(x.path(), to/x.path().filename(), options | copy_options::unspecified)
Otherwise, for the signature with argument ec, ec.clear().
Otherwise, no effects.
Throws: As specified in [fs.err.report].
Remarks: For the signature with argument ec, any library functions called by the implementation shall have an error_code argument if applicable.
[ Example: Given this directory structure:
/dir1
file1
file2
dir2
file3
Calling copy("/dir1", "/dir3") would result in:
/dir1
file1
file2
dir2
file3
/dir3
file1
file2
Alternatively, calling copy("/dir1", "/dir3", copy_options::recursive) would result in:
/dir1
file1
file2
dir2
file3
/dir3
file1
file2
dir2
file3
— end example ]
bool copy_file(const path& from, const path& to);
bool copy_file(const path& from, const path& to, error_code& ec) noexcept;
Returns: copy_file(from, to, copy_options::none) or
copy_file(from, to, copy_options::none, ec), respectively.
Throws: As specified in [fs.err.report].
bool copy_file(const path& from, const path& to, copy_options options);
bool copy_file(const path& from, const path& to, copy_options options,
error_code& ec) noexcept;
Requires: At most one constant from each copy_options option group ([enum.copy_options]) is present in options.
Effects: As follows:
Report a file already exists error as specified in [fs.err.report] if:
!is_regular_file(from), or
exists(to) and !is_regular_file(to), or
exists(to) and equivalent(from, to), or
exists(to) and (options & (copy_options::skip_existing | copy_options::overwrite_existing | copy_options::update_existing)) == copy_options::none.
Otherwise, copy the contents and attributes of the file from resolves to, to the file to resolves to, if:
!exists(to), or
exists(to) and (options & copy_options::overwrite_existing) != copy_options::none, or
exists(to) and (options & copy_options::update_existing) != copy_options::none and from is more recent than to, determined as if by use of the last_write_time function ([fs.op.last_write_time]).
Otherwise, no effects.
Returns: true if the from file was copied, otherwise false. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
Complexity: At most one direct or indirect invocation of status(to).
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;
Effects: Equivalent to
function(read_symlink(existing_symlink), new_symlink) or
function(read_symlink(existing_symlink, ec), new_symlink, ec), respectively,
where function is create_symlink or
create_directory_symlink, as appropriate.
Throws: As specified in [fs.err.report].
bool create_directories(const path& p);
bool create_directories(const path& p, error_code& ec) noexcept;
Effects: Establishes the postcondition by calling create_directory() for any element of p that does not exist.
Postconditions: is_directory(p).
Returns: true if a new directory was created, otherwise false. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
Complexity: Ο(n) where n is the number of elements of p that do not exist.
bool create_directory(const path& p);
bool create_directory(const path& p, error_code& ec) noexcept;
Effects: Establishes the postcondition by attempting to create the directory p resolves to, as if by POSIX mkdir() with a second argument of static_cast<int>(perms::all). Creation failure because p resolves to an existing directory shall not be treated as an error.
Postconditions: is_directory(p).
Returns: true if a new directory was created, otherwise false. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool create_directory(const path& p, const path& existing_p);
bool create_directory(const path& p, const path& existing_p, error_code& ec) noexcept;
Effects: Establishes the postcondition by attempting to create the directory p resolves to, with attributes copied from directory existing_p. The set of attributes copied is operating system dependent. Creation failure because p resolves to an existing directory shall not be treated as an error. [ Note: For POSIX-based operating systems, the attributes are those copied by native API stat(existing_p.c_str(), &attributes_stat) followed by mkdir(p.c_str(), attributes_stat.st_mode). For Windows-based operating systems, the attributes are those copied by native API CreateDirectoryExW(existing_p.c_str(), p.c_str(), 0). — end note ]
Postconditions: is_directory(p).
Returns: true if a new directory was created, otherwise false. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
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;
Effects: Establishes the postcondition, as if by POSIX symlink().
Postconditions: new_symlink resolves to a symbolic link file that contains an unspecified representation of to.
Throws: As specified in [fs.err.report].
[ Note: Some operating systems require symlink creation to identify that the link is to a directory. Portable code should use create_directory_symlink() to create directory symlinks rather than create_symlink() — end note ]
[ Note: Some operating systems do not support symbolic links at all or support them only for regular files. Some file systems (such as the FAT file system) do not support symbolic links regardless of the operating system. — end note ]
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;
Effects: Establishes the postcondition, as if by POSIX link().
Throws: As specified in [fs.err.report].
[ Note: Some operating systems do not support hard links at all or support them only for regular files. Some file systems (such as the FAT file system) do not support hard links regardless of the operating system. Some file systems limit the number of links per file. — end note ]
void create_symlink(const path& to, const path& new_symlink);
void create_symlink(const path& to, const path& new_symlink,
error_code& ec) noexcept;
Effects: Establishes the postcondition, as if by POSIX symlink().
Postconditions: new_symlink resolves to a symbolic link file that contains an unspecified representation of to.
Throws: As specified in [fs.err.report].
[ Note: Some operating systems do not support symbolic links at all or support them only for regular files. Some file systems (such as the FAT file system) do not support symbolic links regardless of the operating system. — end note ]
path current_path();
path current_path(error_code& ec);
Returns: The absolute path of the current working directory, obtained as if by POSIX getcwd(). The signature with argument ec returns path() if an error occurs.
Throws: As specified in [fs.err.report].
Remarks: The current working directory is the directory, associated with the process, that is used as the starting location in pathname resolution for relative paths.
[ Note: The current_path() name was chosen to emphasize that the returned value is a path, not just a single directory name.
The current path as returned by many operating systems is a dangerous global variable. It may be changed unexpectedly by a third-party or system library functions, or by another thread. — end note ]
void current_path(const path& p);
void current_path(const path& p, error_code& ec) noexcept;
Effects: Establishes the postcondition, as if by POSIX chdir().
Postconditions: equivalent(p, current_path()).
Throws: As specified in [fs.err.report].
[ Note: The current path for many operating systems is a dangerous global state. It may be changed unexpectedly by a third-party or system library functions, or by another thread. — end note ]
bool equivalent(const path& p1, const path& p2);
bool equivalent(const path& p1, const path& p2, error_code& ec) noexcept;
Let s1 and s2 be file_statuss, determined as if by status(p1) and status(p2), respectively.
Effects: Determines s1 and s2. If (!exists(s1) && !exists(s2)) || (is_other(s1) && is_other(s2)) an error is reported ([fs.err.report]).
Returns: true, if s1 == s2 and p1 and p2 resolve to the same file system entity, else false. The signature with argument ec returns false if an error occurs.
Two paths are considered to resolve to the same file system entity if two candidate entities reside on the same device at the same location. This is determined as if by the values of the POSIX stat structure, obtained as if by stat() for the two paths, having equal st_dev values and equal st_ino values.
Throws: As specified in ([fs.err.report]).
bool exists(file_status s) noexcept;
Returns: status_known(s) && s.type() != file_type::not_found.
bool exists(const path& p);
bool exists(const path& p, error_code& ec) noexcept;
Let s be a file_status, determined as if by status(p) or status(p, ec), respectively.
Effects: The signature with argument ec calls ec.clear() if status_known(s).
Returns: exists(s).
Throws: As specified in [fs.err.report].
uintmax_t file_size(const path& p);
uintmax_t file_size(const path& p, error_code& ec) noexcept;
Returns: If !exists(p) || !is_regular_file(p) an error is reported ([fs.err.report]). Otherwise, the size in bytes of the file p resolves to, determined as if by the value of the POSIX stat structure member st_size obtained as if by POSIX stat(). The signature with argument ec returns static_cast<uintmax_t>(-1) if an error occurs.
Throws: As specified in [fs.err.report].
uintmax_t hard_link_count(const path& p);
uintmax_t hard_link_count(const path& p, error_code& ec) noexcept;
Returns: The number of hard links for p. The signature with argument ec returns static_cast<uintmax_t>(-1) if an error occurs.
Throws: As specified in [fs.err.report].
bool is_block_file(file_status s) noexcept;
Returns: s.type() == file_type::block.
bool is_block_file(const path& p);
bool is_block_file(const path& p, error_code& ec) noexcept;
Returns: is_block_file(status(p)) or is_block_file(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool is_character_file(file_status s) noexcept;
Returns: s.type() == file_type::character.
bool is_character_file(const path& p);
bool is_character_file(const path& p, error_code& ec) noexcept;
Returns: is_character_file(status(p)) or is_character_file(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool is_directory(file_status s) noexcept;
Returns: s.type() == file_type::directory.
bool is_directory(const path& p);
bool is_directory(const path& p, error_code& ec) noexcept;
Returns: is_directory(status(p)) or is_directory(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool is_empty(const path& p);
bool is_empty(const path& p, error_code& ec) noexcept;
Effects:
Determine file_status s, as if by status(p) or status(p, ec), respectively.
For the signature with argument ec, return false if an error occurred.
Otherwise, if is_directory(s):
Create directory_iterator itr, as if by directory_iterator(p) or directory_iterator(p, ec), respectively.
For the signature with argument ec, return false if an error occurred.
Otherwise, return itr == directory_iterator().
Otherwise:
Determine uintmax_t sz, as if by file_size(p) or file_size(p, ec), respectively.
For the signature with argument ec, return false if an error occurred.
Otherwise, return sz == 0.
Throws: As specified in [fs.err.report].
bool is_fifo(file_status s) noexcept;
Returns: s.type() == file_type::fifo.
bool is_fifo(const path& p);
bool is_fifo(const path& p, error_code& ec) noexcept;
Returns: is_fifo(status(p)) or is_fifo(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool is_other(file_status s) noexcept;
Returns: exists(s) && !is_regular_file(s) && !is_directory(s) && !is_symlink(s).
bool is_other(const path& p);
bool is_other(const path& p, error_code& ec) noexcept;
Returns: is_other(status(p)) or is_other(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool is_regular_file(file_status s) noexcept;
Returns: s.type() == file_type::regular.
bool is_regular_file(const path& p);
Returns: is_regular_file(status(p)).
Throws: filesystem_error if status(p) would throw filesystem_error.
bool is_regular_file(const path& p, error_code& ec) noexcept;
Effects: Sets ec as if by status(p, ec). [ Note: file_type::none, file_type::not_found and file_type::unknown cases set ec to error values. To distinguish between cases, call the status function directly. — end note ]
Returns: is_regular_file(status(p, ec)). Returns false if an error occurs.
bool is_socket(file_status s) noexcept;
Returns: s.type() == file_type::socket.
bool is_socket(const path& p);
bool is_socket(const path& p, error_code& ec) noexcept;
Returns: is_socket(status(p)) or is_socket(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
bool is_symlink(file_status s) noexcept;
Returns: s.type() == file_type::symlink.
bool is_symlink(const path& p);
bool is_symlink(const path& p, error_code& ec) noexcept;
Returns: is_symlink(symlink_status(p)) or is_symlink(symlink_status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
file_time_type last_write_time(const path& p);
file_time_type last_write_time(const path& p, error_code& ec) noexcept;
Returns: The time of last data modification of p, determined as if by the value of the POSIX stat structure member st_mtime obtained as if by POSIX stat(). The signature with argument ec returns file_time_type::min() if an error occurs.
Throws: As specified in [fs.err.report].
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;
Effects: Sets the time of last data modification of the file resolved to by p to new_time, as if by POSIX futimens().
Throws: As specified in [fs.err.report].
[ Note: A postcondition of last_write_time(p) == new_time is not specified since it might not hold for file systems with coarse time granularity. — end note ]
void permissions(const path& p, perms prms);
void permissions(const path& p, perms prms, error_code& ec);
Requires: !((prms & perms::add_perms) != perms::none && (prms & perms::remove_perms) != perms::none).
Effects: Applies the effective permissions bits from prms to the file p resolves to, or if that file is a symbolic link and symlink_nofollow is not set in prms, the file that it points to, as if by POSIX fchmodat(). The effective permission bits are determined as specified in Table [tab:fs.op.permissions], where s is the result of (prms & perms::symlink_nofollow) != perms::none ? symlink_status(p) : status(p).
| Bits present in prms | Effective bits applied |
| Neither add_perms nor remove_perms | prms & perms::mask |
| add_perms | s.permissions() | (prms & perms::mask) |
| remove_perms | s.permissions() & ~(prms & perms::mask) |
[ Note: Conceptually permissions are viewed as bits, but the actual implementation may use some other mechanism. — end note ]
Throws: As specified in [fs.err.report].
path proximate(const path& p, error_code& ec);
Returns: proximate(p, current_path(), ec).
Throws: As specified in [fs.err.report].
path proximate(const path& p, const path& base = current_path());
path proximate(const path& p, const path& base, error_code& ec);
Returns: For the first form:
weakly_canonical(p).lexically_proximate(weakly_canonical(base));
For the second form:
weakly_canonical(p, ec).lexically_proximate(weakly_canonical(base, ec));
or path() at the first error occurrence, if any.
Throws: As specified in [fs.err.report].
path read_symlink(const path& p);
path read_symlink(const path& p, error_code& ec);
Returns: If p resolves to a symbolic link, a path object containing the contents of that symbolic link. The signature with argument ec returns path() if an error occurs.
Throws: As specified in [fs.err.report]. [ Note: It is an error if p does not resolve to a symbolic link. — end note ]
path relative(const path& p, error_code& ec);
Returns: relative(p, current_path(), ec).
Throws: As specified in [fs.err.report].
path relative(const path& p, const path& base = current_path());
path relative(const path& p, const path& base, error_code& ec);
Returns: For the first form:
weakly_canonical(p).lexically_relative(weakly_canonical(base));
For the second form:
weakly_canonical(p, ec).lexically_relative(weakly_canonical(base, ec));
or path() at the first error occurrence, if any.
Throws: As specified in [fs.err.report].
bool remove(const path& p);
bool remove(const path& p, error_code& ec) noexcept;
Effects: If exists(symlink_status(p, ec)), the file p is removed as if by POSIX remove(). [ Note: A symbolic link is itself removed, rather than the file it resolves to. — end note ]
Postconditions: !exists(symlink_status(p)).
Returns: false if p did not exist, otherwise true. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].
uintmax_t remove_all(const path& p);
uintmax_t remove_all(const path& p, error_code& ec) noexcept;
Effects: Recursively deletes the contents of p if it exists, then deletes file p itself, as if by POSIX remove(). [ Note: A symbolic link is itself removed, rather than the file it resolves to. — end note ]
Postconditions: !exists(symlink_status(p)).
Returns: The number of files removed. The signature with argument ec returns static_cast< uintmax_t>(-1) if an error occurs.
Throws: As specified in [fs.err.report].
void rename(const path& old_p, const path& new_p);
void rename(const path& old_p, const path& new_p, error_code& ec) noexcept;
Effects: Renames old_p to new_p, as if by POSIX rename().
[ Note:
If old_p and new_p resolve to the same existing file, no action is taken.
Otherwise, the rename may include the following effects:
if new_p resolves to an existing non-directory file, new_p is removed; otherwise,
if new_p resolves to an existing directory, new_p is removed if empty on POSIX compliant operating systems but may be an error on other operating systems.
A symbolic link is itself renamed, rather than the file it resolves to. — end note ]
Throws: As specified in [fs.err.report].
void resize_file(const path& p, uintmax_t new_size);
void resize_file(const path& p, uintmax_t new_size, error_code& ec) noexcept;
Postconditions: file_size(p) == new_size.
Throws: As specified in [fs.err.report].
Remarks: Achieves its postconditions as if by POSIX truncate().
space_info space(const path& p);
space_info space(const path& p, error_code& ec) noexcept;
Returns: An object of type space_info. The value of the space_info object is determined as if by using POSIX statvfs to obtain a POSIX struct statvfs, and then multiplying its f_blocks, f_bfree, and f_bavail members by its f_frsize member, and assigning the results to the capacity, free, and available members respectively. Any members for which the value cannot be determined shall be set to static_cast<uintmax_t>(-1). For the signature with argument ec, all members are set to static_cast<uintmax_t>(-1) if an error occurs.
Throws: As specified in [fs.err.report].
Remarks: The value of member space_info::available is operating system dependent. [ Note: available may be less than free. — end note ]
file_status status(const path& p);
Effects: As if:
error_code ec; file_status result = status(p, ec); if (result.type() == file_type::none) throw filesystem_error(implementation-supplied-message, p, ec); return result;
Returns: See above.
Throws: filesystem_error. [ Note: result values of file_status(file_type::not_found) and file_status(file_type::unknown) are not considered failures and do not cause an exception to be thrown. — end note ]
file_status status(const path& p, error_code& ec) noexcept;
Effects: If possible, determines the attributes of the file p resolves to, as if by using POSIX stat() to obtain a POSIX struct stat. If, during attribute determination, the underlying file system API reports an error, sets ec to indicate the specific error reported. Otherwise, ec.clear(). [ Note: This allows users to inspect the specifics of underlying API errors even when the value returned by status() is not file_status(file_type::none). — end note ]
Let prms denote the result of (m & perms::mask), where m is determined as if by converting the st_mode member of the obtained struct stat to the type perms.
Returns:
If ec != error_code():
If the specific error indicates that p cannot be resolved because some element of the path does not exist, returns file_status(file_type::not_found).
Otherwise, if the specific error indicates that p can be resolved but the attributes cannot be determined, returns file_status(file_type::unknown).
Otherwise, returns file_status(file_type::none).
[ Note: These semantics distinguish between p being known not to exist, p existing but not being able to determine its attributes, and there being an error that prevents even knowing if p exists. These distinctions are important to some use cases. — end note ]
Otherwise,
If the attributes indicate a regular file, as if by POSIX S_ISREG, returns file_status(file_type::regular, prms). [ Note: file_type::regular implies appropriate <fstream> operations would succeed, assuming no hardware, permission, access, or file system race errors. Lack of file_type::regular does not necessarily imply <fstream> operations would fail on a directory. — end note ]
Otherwise, if the attributes indicate a directory, as if by POSIX S_ISDIR, returns file_status(file_type::directory, prms). [ Note: file_type::directory implies directory_iterator(p) would succeed. — end note ]
Otherwise, if the attributes indicate a block special file, as if by POSIX S_ISBLK, returns file_status(file_type::block, prms).
Otherwise, if the attributes indicate a character special file, as if by POSIX S_ISCHR, returns file_status(file_type::character, prms).
Otherwise, if the attributes indicate a fifo or pipe file, as if by POSIX S_ISFIFO, returns file_status(file_type::fifo, prms).
Otherwise, if the attributes indicate a socket, as if by POSIX S_ISSOCK, returns file_status(file_type::socket, prms).
Otherwise, returns file_status(file_type::unknown, prms).
Remarks: If a symbolic link is encountered during pathname resolution, pathname resolution continues using the contents of the symbolic link.
bool status_known(file_status s) noexcept;
Returns: s.type() != file_type::none.
file_status symlink_status(const path& p);
file_status symlink_status(const path& p, error_code& ec) noexcept;
Effects: Same as status(), above, except that the attributes of p are determined as if by using POSIX lstat() to obtain a POSIX struct stat.
Let prms denote the result of (m & perms::mask), where m is determined as if by converting the st_mode member of the obtained struct stat to the type perms.
Returns: Same as status(), above, except that if the attributes indicate a symbolic link, as if by POSIX S_ISLNK, returns file_status(file_type::symlink, prms). The signature with argument ec returns file_status(file_type::none) if an error occurs.
Remarks: Pathname resolution terminates if p names a symbolic link.
Throws: As specified in [fs.err.report].
path system_complete(const path& p);
path system_complete(const path& p, error_code& ec);
Effects: Composes an absolute path from p, using the same rules used by the operating system to resolve a path passed as the filename argument to standard library open functions.
Returns: The composed path. The signature with argument ec returns path() if an error occurs.
Postconditions: For the returned path, rp, rp.is_absolute() is true.
Throws: As specified in [fs.err.report].
[ Example: For POSIX-based operating systems, system_complete(p) has the same semantics as absolute(p, current_path()).
For Windows-based operating systems, system_complete(p) has the same semantics as absolute(p, current_path()) if p.is_absolute() || !p.has_root_name() or p and current_path() have the same root_name(). Otherwise system_complete(p) acts as if absolute(p, cwd) is the current directory for the p.root_name() drive. For programs run by the command processor, however, the current directory for the p.root_name() drive may have been set by a prior program, and this may have unintended consequences. — end example ]
path temp_directory_path();
path temp_directory_path(error_code& ec);
Returns: An unspecifed directory path suitable for temporary files. An error shall be reported if !exists(p) || !is_directory(p), where p is the path to be returned. The signature with argument ec returns path() if an error occurs.
Throws: As specified in [fs.err.report].
[ Example: For POSIX-based operating systems, an implementation might return the path supplied by the first environment variable found in the list TMPDIR, TMP, TEMP, TEMPDIR, or if none of these are found, "/tmp".
For Windows-based operating systems, an implementation might return the path reported by the Windows GetTempPath API function. — end example ]
path weakly_canonical(const path& p);
path weakly_canonical(const path& p, error_code& ec);
Returns: p with symlinks resolved and the result normalized ([fs.def.normal.form]).
Effects: Using status(p) or status(p, ec), respectively, to determine existence, return a path composed by operator/= from the result of calling canonical() without a base argument and with a path argument composed of the leading elements of p that exist, if any, followed by the elements of p that do not exist, if any. For the first form, canonical() is called without an error_code argument. For the second form, canonical() is called with ec as an error_code argument, and path() is returned at the first error occurrence, if any.
Postconditions: The returned path is in normal form ([fs.def.normal.form]).
Remarks: Implementations are encouraged to avoid unnecessary normalization such as when canonical() has already been called on the entirety of p.
Throws: As specified in [fs.err.report].