How to get SDL error as integer, enum or something else, except string?

I was working on a project using SDL2 and C. When it opens images as SDL_Surface, sometimes when the filename provided is not an image, it would return error message saying that Unsupported image format. I currently use SDL_GetError() to print the error message, but would like to print my own error message instead of the error message provided by SDL_GetError(). How can I get the SDL error as an integer or enum or some other value, so that I can handle the error on my own?