[fs.op.exists]

bool filesystem::exists(file_status s) noexcept;

Returns: status_known(s) && s.type() != file_type::not_found.

bool filesystem::exists(const path& p);
bool filesystem::exists(const path& p, error_code& ec) noexcept;

Let s be a file_status, determined as if by status(p) or status(p, ec), respectively.

Effects: The signature with argument ec calls ec.clear() if status_known(s).

Throws: As specified in [fs.err.report].

31 Input/output library [input.output]