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std::filesystem::exists(3) C++ Standard Libary std::filesystem::exists(3) NAME std::filesystem::exists - std::filesystem::exists Synopsis Defined in header <filesystem> bool exists( std::filesystem::file_status s ) noexcept; (1) (since C++17) bool exists( const std::filesystem::path& p ); bool exists( const std::filesystem::path& p, std::error_code& ec ) (2) (since C++17) noexcept; Checks if the given file status or path corresponds to an existing file or directory. 1) Equivalent to status_known(s) && s.type() != file_type::not_found. 2) Let s be a std::filesystem::file_status determined as if by sta- tus(p) or status(p, ec) (symlinks are followed), respectively. Returns ex- ists(s). The non-throwing overload calls ec.clear() if status_known(s). Parameters s - file status to check p - path to examine ec - out-parameter for error reporting in the non-throwing overload Return value true if the given path or file status corresponds to an existing file or directory, false otherwise. Exceptions 2) The overload that does not take a std::error_code& parameter throws filesystem::filesystem_error on underlying OS API errors, con- structed with p as the first path argument and the OS error code as the error code argu- ment. The overload taking a std::error_code& parameter 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 The information provided by this function is usually also provided as a byproduct of directory iteration. During directory iteration, calling exists(*it- erator) is less efficient than exists(iterator->status()). Example // Run this code #include <iostream> #include <fstream> #include <cstdint> #include <filesystem> namespace fs = std::filesystem; void demo_exists(const fs::path& p, fs::file_status s = fs::file_sta- tus{}) { std::cout << p; if(fs::status_known(s) ? fs::exists(s) : fs::exists(p)) std::cout << " exists\n"; else std::cout << " does not exist\n"; } int main() { const fs::path sandbox{"sandbox"}; fs::create_directory(sandbox); std::ofstream{sandbox/"file"}; // create regular file fs::create_symlink("non-existing", sandbox/"symlink"); demo_exists(sandbox); for (const auto& entry : fs::directory_iterator(sandbox)) demo_exists(entry, entry.status()); // use cached status from directory entry fs::remove_all(sandbox); } Output: "sandbox" exists "sandbox/symlink" does not exist "sandbox/file" exists See also status determines file attributes symlink_status determines file attributes, checking the symlink tar- get (C++17) (function) (C++17) file_status represents file type and permissions (C++17) (class) exists checks whether directory entry refers to existing file system object (public member function of std::filesystem::direc- tory_entry) http://cppreference.com 2022.07.31 std::filesystem::exists(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Output: | See also
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