renaming unnamed buffer at creation

[Yakov Lerner]

Now that my attempt to write unnamed buffer under
name /tmp/N failed, I want to autoname empty buffer.
My first attempt does not work. Autoevent is ot invoked.

function! TempName()
   let x=1
   while filereadable("/tmp/".x)
       let x = x + 1
   endwhile
   return "/tmp/".x
endfun

au BufNew * if(expand('<afile>') == '') | call input("AAA") | endif
au BufNew * if(expand('<afile>') == '') | exe "file ".TempName() | endif

Yakov