[sansk]

the tittle says everything..

[Patrick]

What command processor are you using?

[sansk]

ZCMD

[Patrick]

Here you go, I've included some explanation inside, Enjoy!

pawn Код:

public OnPlayerCommandPerformed(playerid, cmdtext[], success)//callback from #include <zcmd>
{//open
    if(!success)//If the command does not exist on the server, ! = false
        return SendClientMessage(playerid, COLOR_WHITE, "Your Error Message Here.");//showing the message
    return 1;
}//close

[sansk]

Thanks a lot!
and for not just giving me something to past but telling me how it works.

[Konstantinos]

OnPlayerCommandPerformed is called after a command execution. If the command does not exist returns 0, so..

pawn Код:

if(!success)
// if it returns 0, send an error message