[Sellize]

Untested but should work

PHP код:

CMD:offcheck(playerid,params[])
{
    new offnick[MAX_PLAYER_NAME];
    if(sscanf(params,"s[128]",offnick)) return SendClientMessage(playerid, -1, "Usage: /offcheck [full name]");
    if(IsPlayerConnected(GetPlayerIdFromName(offnick)) return SendClientMessage(playerid, -1, "You cannot use this command on online players.");
    // Code
    return 1;
}
stock GetPlayerIdFromName(playername[])
{
  for(new i = 0; i <= MAX_PLAYERS; i++)
  {
    if(IsPlayerConnected(i))
    {
      new playername2[MAX_PLAYER_NAME];
      GetPlayerName(i, playername2, sizeof(playername2));
      if(strcmp(playername2, playername, true, strlen(playername)) == 0)
      {
        return i;
      }
    }
  }
  return INVALID_PLAYER_ID;
}