std::filesystem::path::compare

 

C++

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Feature test macros(C++20)

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Filesystem library(C++17)

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Technical specifications

Symbols index

External libraries

 

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator    filesystem::file_status filesystem::space_info	filesystem::file_type filesystem::file_time_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options
Functions
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path filesystem::temp_directory_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

std::filesystem::path

Member types
Member constants
path::native_formatpath::generic_formatpath::auto_format
Member functions
path::path path::~path path::operator= path::assign path::appendpath::operator/= path::concatpath::operator+= path::clear path::make_preferred path::remove_filename path::replace_filename path::replace_extension    path::swap path::compare path::beginpath::end	path::c_strpath::nativepath::operator string_type path::stringpath::u8stringpath::u16stringpath::u32stringpath::wstring path::generic_stringpath::generic_u8stringpath::generic_u16stringpath::generic_u32stringpath::generic_wstring path::lexically_normalpath::lexically_relativepath::lexically_proximate
Path decomposition
path::root_name path::root_directory path::root_path path::relative_path path::parent_path path::filename path::stem path::extension path::empty	path::has_root_pathpath::has_root_namepath::has_root_directorypath::has_relative_pathpath::has_parent_pathpath::has_filenamepath::has_stempath::has_extension path::is_absolutepath::is_relative
Non-member functions
operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)	operator/ operator<<operator>> swap(std::filesystem::path) hash_value u8path
Helper classes
hash<std::filesystem::path>	formatter<std::filesystem::path> (C++26)

 

int compare(const path& p )constnoexcept;	(1)	(since C++17)
int compare(const string_type& str )const; int compare(std::basic_string_view<value_type> str )const;	(2)	(since C++17)
int compare(const value_type* s )const;	(3)	(since C++17)

Compares the lexical representations of the path and another path.

1) If root_name().native().compare(p.root_name().native()) is nonzero, returns that value.

Otherwise, if has_root_directory()!= p.has_root_directory(), returns a value less than zero if has_root_directory() is false and a value greater than zero otherwise.

Otherwise returns a value less than, equal to or greater than ​0​ if the relative portion of the path (relative_path()) is respectively lexicographically less than, equal to or greater than the relative portion of p (p.relative_path()). Comparison is performed element-wise, as if by iterating both paths from begin() to end() and comparing the result of native() for each element.

2) Equivalent to compare(path(str)).

3) Equivalent to compare(path(s)).

Parameters

p	-	a path to compare to
str	-	a string or string view representing path to compare to
s	-	a null-terminated string representing path to compare to

Return value

A value less than ​0​ if the path is lexicographically less than the given path.

A value equal to ​0​ if the path is lexicographically equal to the given path.

A value greater than ​0​ if the path is lexicographically greater than the given path.

Exceptions

2,3) May throw implementation-defined exceptions.

Notes

For two-way comparisons, binary operators may be more suitable.

Example

Run this code

#include <filesystem>#include <iostream>#include <string_view>namespace fs = std::filesystem;   void demo(fs::path p1, fs::path p2, std::string_view msg){std::cout<< p1;constint rc = p1.compare(p2);if(rc <0)std::cout<<" < ";elseif(rc >0)std::cout<<" > ";elsestd::cout<<" == ";std::cout<< p2 <<" \t: "<< msg <<'\n';}   int main(){ demo("/a/b/", "/a/b/", "simple"); demo("/a/b/", "/a/b/c", "simple"); demo("/a/b/../b", "/a/b", "no canonical conversion"); demo("/a/b", "/a/b/.", "no canonical conversion"); demo("/a/b/", "a/c", "absolute paths order after relative ones");}

Output:

"/a/b/" == "/a/b/"  : simple "/a/b/" < "/a/b/c" : simple "/a/b/../b" > "/a/b" : no canonical conversion "/a/b" < "/a/b/." : no canonical conversion "/a/b/" > "a/c"  : absolute paths order after relative ones

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2936	C++17	compared all path elements directly	root name and root directory handled separately

See also

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++17)(C++17)(until C++20)(C++17)(until C++20)(C++17)(until C++20)(C++17)(until C++20)(C++17)(until C++20)(C++20)

lexicographically compares two paths (function)