Recognize Minecraft player names, via command block?

Is it possible to use a command block to identify the player's name?

So that a player's name is put on a sign, is that possible?

Go to mcstacker.net

the website generates dir commands from a selection of different things

I bet you can do that too

With @p you have the name of the next player.

No, I want the player's name to be written on a sign

I don't know the exact command now, but setblock should work.