CODEWITHSUNDEEP
vbscriptwmi
Sierramike
Sierramike

Reputation: 481

In VBScript, how can I retrieve the first element of an InstancesOf collection?

I'm writing a VBScript that should identify the OS details. I found an exemple here using InstancesOf Win32_Operating system, but instead of the foreach loop from the sample, I only want to address the first occurence, so I did:

Set SystemSet = GetObject("winmgmts:").InstancesOf ("Win32_OperatingSystem")
Set System = SystemSet.Item(0)

Also tried Set System = SystemSet(0), but each time I have a generic failure error message (Echec générique in french).

How can I achieve this so I can then compare the System.Caption string?

Upvotes: 3

Views: 733

Answers (1)

user692942
user692942

Reputation: 16682

The GetObject("winmgmts:") returns a SWbemServices object. According to the documentation for the SWbemServices object the InstanceOf() method:

From SWbemServices.InstancesOf method
creates an enumerator that returns the instances of a specified class according to the user-specified selection criteria.

The idea of an enumerator is to enumerate over a collection of objects this lends itself to the VBScript For Each statement for iterating over an enumerator.

A simple example would be;

Dim swbemInstances, swbemInstance
Set swbemInstances = GetObject("winmgmts:").InstancesOf("Win32_OperatingSystem")
For Each swbemInstance In swbemInstances
  WScript.Echo swbemInstance.Caption
Next

You can access an instance directly from the enumerator using the ItemIndex method which as the documentation says;

From SWbemObjectSet.ItemIndex method
returns the SWbemObject associated with the specified index into the collection. The index indicates the position of the element within the collection. Collection numbering starts at zero.

Note: Interesting point the documentation actually cites the Win32_OperatingSystem class as an example where you likely want to retrieve only one instance and explains how to use ItemIndex to facilitate it.

From SWbemObjectSet.ItemIndex method - Examples
Only one instance of Win32_OperatingSystem exists for each operating system installation. Creating the GetObject path to obtain the single instance is awkward so scripts normally enumerate Win32_OperatingSystem even though only one instance is available. The following VBScript code example shows how to use the ItemIndex method to get to the one Win32_OperatingSystem without using a For Each loop.

Something like;

Dim swbemInstance
Set swbemInstance = GetObject("winmgmts:").InstancesOf("Win32_OperatingSystem").ItemIndex(0)
WScript.Echo swbemInstance.Caption

Also mentioned in the comments

Upvotes: 4

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