std::vector<std::string> directory_content(std::string path, bool sub_directory = false)
Return each sub-files's path of the directory "path" in a std::vector of std::string. If "sub_directory" is true, adds the sub-files of the sub-directories in "path".
If any kinds of error occurs, the returned std::vector is empty.
std::string file_extension(std::string path, bool with_point = false)
Return the extension of "path", with the point at the start if "with_point" is true.
std::string file_name(std::string path, bool with_extension = false)
Return the name of "path", with the extension if "with_extension" is true.