[Twizted]

Not tested, but should work fine:

pawn Код:

CMD:check(playerid, params[])
{
    new targetid;

    new Float:pX,
        Float:pY,
        Float:pZ;

    new string[128];

    if(sscanf(params, "u", targetid)) return SendClientMessage(playerid, -1, "/check (ID)");
    if(!IsPlayerConnected(targetid)) return SendClientMessage(playerid, -1, "That player isn't connected.");
    
    GetPlayerPos(targetid, pX, pY, pZ);
    format(string, sizeof(string), "ID %d position: %f, %f, %f", targetid, pX, pY, pZ);
    SendClientMessage(playerid, -1, string);

    return 1;
}