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std::filesystem::is_empty(3) C++ Standard Libary std::filesystem::is_empty(3) NAME std::filesystem::is_empty - std::filesystem::is_empty Synopsis Defined in header <filesystem> bool is_empty( const std::filesystem::path& p ); (since C++17) bool is_empty( const std::filesystem::path& p, std::error_code& ec ); Checks whether the given path refers to an empty file or directory. Parameters p - path to examine ec - error code to modify in case of error Return value true if the file indicated by p or if the type indicated s refers to an empty file or directory, false otherwise. The non-throwing overload returns false if an error occurs. Exceptions 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. Example // Run this code #include <filesystem> #include <fstream> #include <iostream> #include <cstdio> int main() { namespace fs = std::filesystem; const fs::path tmp_dir{ fs::temp_directory_path() }; std::cout << std::boolalpha << "Temp dir: " << tmp_dir << '\n' << "is_empty(): " << fs::is_empty(tmp_dir) << '\n'; const fs::path tmp_name{ tmp_dir / std::tmpnam(nullptr) }; std::cout << "Temp file: " << tmp_name << '\n'; std::ofstream file{ tmp_name.string() }; std::cout << "is_empty(): " << fs::is_empty(tmp_name) << '\n'; file << "cppreference.com"; file.flush(); std::cout << "is_empty(): " << fs::is_empty(tmp_name) << '\n' << "file_size(): " << fs::file_size(tmp_name) << '\n'; file.close(); fs::remove(tmp_name); } Possible output: Temp dir: "/tmp" is_empty(): false Temp file: "/tmp/fileCqd9DM" is_empty(): true is_empty(): false file_size(): 16 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 3013 C++17 error_code overload marked noexcept but can noexcept removed allocate memory See also status determines file attributes symlink_status determines file attributes, checking the symlink tar- get (C++17) (function) (C++17) exists checks whether path refers to existing file system object (C++17) (function) http://cppreference.com 2022.07.31 std::filesystem::is_empty(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Example | Possible output: | See also
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