RULES for pawns on files b-g.
White (the side with extra pawn) wins if at least any two of the following conditions are met:
* (a) his king is in front of the pawn
* (b) he has the opposition
* (c) his king is on the sixth rank.
It's a draw if black (the defending side) can get his king to the square in front of the pawn, or the square two spaces in front of the pawn, with one exception. An example of this exception is White King=c6 White Pawn=d6 Black King=d8. With white to move, he wins. This example may be moved horizontally to cover any of the files except when the pawn is on the a or h files.
If the pawn is on the a or h file, it's more difficult to win. If the black king can reach c8 or f8 respectively, then the game is draw because he can either get to the corner, and can't be driven away, or if the white king is already in the corner, keep it there by force. The exception to this rule is when the white king is on b6 (g6), and the pawn is on a6 (h6), and black's king is on c8 (f8). With white to move in that situation, it's a win after h7.