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std::filesy...th::compare(3) C++ Standard Libary std::filesy...th::compare(3) NAME std::filesystem::path::compare - std::filesystem::path::compare Synopsis int compare( const path& p ) const noexcept; (1) (since C++17) int compare( const string_type& str ) const; (2) (since C++17) int compare( std::basic_string_view<value_type> str ) const; 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(), re- turns 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 lexi- cographically 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 <iostream> #include <filesystem> #include <string_view> namespace fs = std::filesystem; void demo(fs::path p1, fs::path p2, std::string_view msg) { using std::cout; cout << p1; const int rc = p1.compare(p2); if(rc < 0) cout << " < "; else if(rc > 0) cout << " > "; else cout << " == "; 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 retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct be- havior LWG 2936 C++17 compared all path elements root name and root directory handled directly separately See also operator== operator!= operator< operator<= operator> operator>= lexicographically compares two paths operator<=> (function) (until C++20) (until C++20) (until C++20) (until C++20) (until C++20) (C++20) http://cppreference.com 2022.07.31 std::filesy...th::compare(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Output: | See also
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