checkbook accepts a file containing chess moves in algebraic notation and checks the file for illegal moves. The file may be either a complete game or opening segments of a game separated by lines beginning with '#' or '!'.
Castling and en-passant moves are allowed. But in castling moves no check is made whether the pieces have moved before or whether a intervening square is under attack.
The -x option allows use of checkbook with xboard game files. Its only effect is to cause the first 2 lines of the file to be skipped. Moves may be numbered but do not need to be. Moves must be in full algebraic format (i.e. a2a4). Short notation is not allowed.
gnuchess(6) chesstool(6) xboard(6)