Minecraft – use the /testfor command In Minecraft

minecraft-java-edition

I found the /testfor command today in Minecraft, but when I use it in a command block it says

Usage: /testfor <player>

and when I do that it then says

/testfor must be used by command blocks with an analog output.

What does that mean and how can I use the command?

Best Answer

As per the Minecraft Wiki Commands page, the syntax of the /testfor command is either of:

/testfor <playername>
/testfor <selector>

So, e.g., a command block that fires the command /testfor notch, with a redstone comparator attached to it, would output a signal from the comparator, assuming that Notch is playing on that server.

Using the Command Block selectors syntax lets you do things like /testfor @a[r=3], which will cause the comparator to emit a signal strength equal to the number of players within three meters. Or /testfor @a[m=2], which would cause the comparator to emit a signal strength equal to the number of Creative Mode players currently on the server.

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