std::filesystem::file_size - cppreference.com (original) (raw)

If p does not exist, reports an error.

For a regular file p, returns the size determined as if by reading the st_size member of the structure obtained by POSIX stat (symlinks are followed).

The result of attempting to determine the size of a directory (as well as any other file that is not a regular file or a symlink) is implementation-defined.

The non-throwing overload returns static_cast<std::uintmax_t>(-1) on errors.

[edit] Parameters

[edit] Return value

The size of the file, in bytes.

[edit] Exceptions

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

1. Throws std::filesystem::filesystem_error on underlying OS API errors, constructed with p as the first path argument and the OS error code as the error code argument.

2. Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur.

[edit] Example

#include #include #include #include namespace fs = std::filesystem;   struct HumanReadable { std::uintmax_t size{};   private: friend std::ostream& operator<<(std::ostream& os, HumanReadable hr) { int o{}; double mantissa = hr.size; for (; mantissa >= 1024.; mantissa /= 1024., ++o); os << std::ceil(mantissa * 10.) / 10. << "BKMGTPE"[o]; return o ? os << "B (" << hr.size << ')' : os; } };   int main(int, char const* argv[]) { fs::path example = "example.bin"; fs::path p = fs::current_path() / example; std::ofstream(p).put('a'); // create file of size 1 std::cout << example << " size = " << fs::file_size(p) << '\n'; fs::remove(p);   p = argv[0]; std::cout << p << " size = " << HumanReadable{fs::file_size(p)} << '\n';   try { std::cout << "Attempt to get size of a directory:\n"; [[maybe_unused]] auto x_x = fs::file_size("/dev"); } catch (fs::filesystem_error& e) { std::cout << e.what() << '\n'; }   for (std::error_code ec; fs::path bin : {"cat", "mouse"}) { bin = "/bin"/bin; if (const std::uintmax_t size = fs::file_size(bin, ec); ec) std::cout << bin << " : " << ec.message() << '\n'; else std::cout << bin << " size = " << HumanReadable{size} << '\n'; } }

Possible output:

"example.bin" size = 1 "./a.out" size = 22KB (22512) Attempt to get size of a directory: filesystem error: cannot get file size: Is a directory [/dev] "/bin/cat" size = 50.9KB (52080) "/bin/mouse" : No such file or directory

[edit] See also

| | changes the size of a regular file by truncation or zero-fill (function) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | determines available free space on the file system (function) [edit] | | | returns the size of the file to which the directory entry refers (public member function of std::filesystem::directory_entry) [edit] |