Help with unknown command?

[xXMADEXx]

Is there a way so that if someone types an unknow command that the server will output to them "Server: Error that command does not exist" ? If it is, how would i do this?

[TAPL]

As far as i know, there aren't a way to get the exist commands, you can add them manually to a table and then use event onPlayerCommand and check if the command was in the table or not.