Minecraft 1.8: Check if player is at a specific Y position

Can you tell me if it is possible to use the testfor command to check if a player stands on a specific Y position?

I tried it with /testfor @e[type=Player] {Pos:{Y:57d}}, but it won't work.

The error was [Player] did not match the required data structure

Use @p[y=<y value>], replacing with the y coordinate you wish to search.

Additionally, you can define a cubic search area with @p[x=<x value>,y=<y value>,z=<z value>], replacing <x value>, <y value>, and <z value> with their respective values.

Do not put spaces after the commas. For more information, visit:

http://minecraft.gamepedia.com/Tutorials/Command_Block http://minecraft.gamepedia.com/Commands