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std::filesy...::equivalent(3) C++ Standard Libarystd::filesy...::equivalent(3) NAME std::filesystem::equivalent - std::filesystem::equivalent Synopsis Defined in header <filesystem> bool equivalent( const std::filesystem::path& p1, const std::filesystem::path& p2 ); bool equivalent( const std::filesystem::path& p1, (since C++17) const std::filesystem::path& p2, std::error_code& ec ) noexcept; Checks whether the paths p1 and p2 resolve to the same file system entity. If either p1 or p2 does not exist, an error is reported. The non-throwing overload returns false on errors. Parameters p1, p2 - paths to check for equivalence ec - out-parameter for error reporting in the non-throwing over- load Return value true if the p1 and p2 refer to the same file or directory and their file status is the same. false otherwise. Exceptions The overload that does not take a std::error_code& parameter throws filesystem::filesystem_error on underlying OS API errors, con- structed with p1 as the first path argument, p2 as the second path argument, and the OS er- ror code as the error code argument. The overload taking a std::error_code& parame- ter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails. Notes Two paths are considered to resolve to the same file system entity if the two candidate entities the paths resolve to are located on the same de- vice at the same location. For POSIX, this means that the st_dev and st_ino members of their POSIX stat structure, obtained as if by POSIX stat(), are equal. In particular, all hard links for the same file or directory are equivalent, and a symlink and its target on the same file system are equivalent. Example // Run this code #include <iostream> #include <cstdint> #include <filesystem> namespace fs = std::filesystem; int main() { // hard link equivalency fs::path p1 = "."; fs::path p2 = fs::current_path(); if(fs::equivalent(p1, p2)) std::cout << p1 << " is equivalent to " << p2 << '\n'; // symlink equivalency for(const fs::path lib : {"/lib/libc.so.6", "/lib/x86_64-linux- gnu/libc.so.6"}) { try { p2 = lib.parent_path() / fs::read_symlink(lib); } catch(std::filesystem::filesystem_error const& ex) { std::cout << ex.what() << '\n'; continue; } if(fs::equivalent(lib, p2)) std::cout << lib << " is equivalent to " << p2 << '\n'; } } Possible output: "." is equivalent to "/var/tmp/test" filesystem error: read_symlink: No such file or directory [/lib/libc.so.6] "/lib/x86_64-linux-gnu/libc.so.6" is equivalent to "/lib/x86_64-linux- gnu/libc-2.23.so" Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 2937 C++17 error condition specified incorrectly corrected See also compare compares the lexical representations of two paths lexicographically (public member function of std::filesystem::path) 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) status determines file attributes symlink_status determines file attributes, checking the symlink tar- get (C++17) (function) (C++17) http://cppreference.com 2022.07.31 std::filesy...::equivalent(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Possible output: | See also
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