How to get fully qualified domain name on Windows in Delphi

Question

I need to get a fully qualified domain name for a Windows machine on a domain in Delphi.

I've tried to use LookupAccountSid but it gives me only the netbios domain name, in my case it is "intranet" but I need the full "intranet.companyname.com"

Any Ideas?

Answer 1

Try the GetUserNameEx Windows API function.

const
  NameUnknown            = 0;
  NameFullyQualifiedDN   = 1;
  NameSamCompatible      = 2;
  NameDisplay            = 3;
  NameUniqueId           = 6;
  NameCanonical          = 7;
  NameUserPrincipal      = 8;
  NameCanonicalEx        = 9;
  NameServicePrincipal   = 10;
  NameDnsDomain          = 12;

function GetUserNameExString(ANameFormat: DWORD): string;
var
  Buf: array[0..256] of Char;
  BufSize: DWORD;
  GetUserNameEx: function (NameFormat: DWORD; lpNameBuffer: LPSTR;
    var nSize: ULONG): BOOL; stdcall;
begin
  Result := '';
  BufSize := SizeOf(Buf) div SizeOf(Buf[0]);
  GetUserNameEx := GetProcAddress(GetModuleHandle('secur32.dll'), 'GetUserNameExA');
  if Assigned(GetUserNameEx) then
    if GetUserNameEx(ANameFormat, Buf, BufSize) then
      Result := Buf;
end;

using the NameDnsDomain format for example, will result www.mydomain.com\user_name if you are logged into "www.mydomain.com" domain.

---

Since I now implemented this for my own needs in our application, @iPath's comment was quit right. better use GetComputerNameEx, and specify one of the COMPUTER_NAME_FORMAT for your own needs.

A Delphi implementation would look like this (Unicode version):

interface
...
type
  COMPUTER_NAME_FORMAT = (
    ComputerNameNetBIOS,
    ComputerNameDnsHostname,
    ComputerNameDnsDomain,
    ComputerNameDnsFullyQualified,
    ComputerNamePhysicalNetBIOS,
    ComputerNamePhysicalDnsHostname,
    ComputerNamePhysicalDnsDomain,
    ComputerNamePhysicalDnsFullyQualified,
    ComputerNameMax);

function GetComputerNameExString(ANameFormat: COMPUTER_NAME_FORMAT): WideString;

implementation
...
function GetComputerNameExW(NameType: COMPUTER_NAME_FORMAT; lpBuffer: LPWSTR;
  var nSize: DWORD): BOOL; stdcall; external kernel32 name 'GetComputerNameExW';

function GetComputerNameExString(ANameFormat: COMPUTER_NAME_FORMAT): WideString;
var
  nSize: DWORD;
begin
  nSize := 1024;
  SetLength(Result, nSize);
  if GetComputerNameExW(ANameFormat, PWideChar(Result), nSize) then
    SetLength(Result, nSize)
  else
    Result := '';
end;