Make Sure Run Script under 32-bit cscript.exe or wscript.exe when 32-bit COM object is required.

On 64-bit Windows, we have two different sets of Window Scripting Host (WSH), 32-bit or 64-bit. The defaults are located at C:\Windows\System32, where cscript.exe or wscript.exe (with GUI, e.g. message prompt) is used run the *.vbs or *.js WSH files. However, these are 64-bit, meaning that if you try to create a COM object (automation), you will get similar errors like the following. (Automation Server Can’t Create Objects).

Well, when you want to deploy some scripts that require a 32-bit COM (Component Object Model) object, you don’t want the system end up showing this error dialog. However, you also don’t have the control over user’s preferences on which particular sets of cscript.exe or wscript.exe should be used to invoke running the scripting files (you can change the opening configuration by right-click-open with-and-choose the right ?script.exe).

When, what we can achieve here is to check whether which script engine is used at the begining of the script execution. If it is 32-bit, then carry on otherwise, show a information dialog, like this.

We can check WScript.FullName to see its scripting engine file path contains the word ‘syswow64’, this works for most cases, unless some one intentionally puts a 64-bit engine under this folder. WoW64 stands for Windows 32-bit on Windows 64-bit. If a engine is 32-bit, then it surely be able to create 32-bit COM object.

The following VBScript checks the engine file path and exit printing the above dialog if it seems to be a 64-bit engine, e.g. ‘C:\windows\system32\cscript.exe’.

Dim Mode
If Not IsEmpty(WScript) Then
	If (InStr(LCase(WScript.FullName), "syswow64")) Then	
		'WScript.Echo "OK, It is in 32-bit"
		Mode = 0
	Else
		WScript.Echo "Please Use SysWOW64\cscript.exe or wscript.exe (32-bit) to lauch this script."	
		WScript.Quit
	End If
Else
	'We don't have access to WScript, most-likely-we are using MS Script Control.
	Mode = 1                       
End If

' Set the corresponding Message Box prompt.
Sub MessageBox(str)
	If Mode = 0 Then
		WScript.Echo str
	Else
		Msgbox str
	End If
End Sub

The above script also sets the correct message prompt function. If WScript is not available (empty), it is likely that we are using MS Script Control, where WScript.Echo is not available, we must use the alternative, Msgbox.

However, translating the above into JScript is a bit lengthy. Let’s look at the code first.

(function () {
	var mode;
	try {
		if (WScript != undefined) {
			var path = WScript.FullName.toLowerCase();
			if (path.indexOf('syswow64') >= 0) {
				mode = 0;
			} else {
				WScript.Echo("Please Use SysWOW64\\cscript.exe or wscript.exe (32-bit) to lauch this script.");
				WScript.Quit();
			}
		} else {
			mode = 1;
		}
	} catch (err) {
		mode = 1;
	}
	var obj = new ActiveXObject("WScript.Shell");
	function MessageBox(str) {
		if (mode == 0) {
			WScript.Echo(str);
		} else {
			obj.popup(str);
		}
	}
})();

We have to wrap the check in try … catch because if not, MS JScript Engine will complain that WScript is not defined under MS Script Control. As JScript does not provide inbuilt Msgbox as VBScript does, it can create COM object WScript.Shell to use its popup function to prompt a message, which can also be used in VBScript.

–EOF (The Ultimate Computing & Technology Blog) —