Can all UCI engines output a FEN for the current position or is it just StockFish? I know in StockFish if you type &quot;d&quot; you get an ascii view of the board and a FEN string for the current state. Is there any command in other UCI engines such as Rybka 4 that will output a FEN string?
From reading various chess source codes, mostly before 2005, I can state that most don't a FEN output.  Any that would allow for a non-starting position should accept FEN, as it's just a special form of PGN.
Crafty and san_kit both have a &quot;fen&quot; command.