Creating a WMI Script

Creating a WMI Script

You can view or manipulate any information made available through WMI using scripts. Scripts can be written in any scripting language that supports Microsoft ActiveX script hosting, including Visual Basic Scripting Edition (VBScript), PowerShell, and Perl. Windows Script Host (WSH), Active Server Pages, and Internet Explorer can all host WMI scripts.

Note  

The primary scripting language currently supported by WMI is PowerShell. However, WMI also contains a robust body of scripting support for VBScript and other languages that access the Scripting API for WMI.

 

WMI Scripting Languages

The two main languages supported by WMI are PowerShell and VBScript (through the Windows Script Host, or WSH).

  • PowerShell was designed with tight integration with WMI in mind. As such, much of the underlying elements of WMI are built into the WMI cmdlets: Get-WmiObject, Set-WmiInstance, Invoke-WmiMethod, and Remove-WmiObject. The following table describes the general processes used for accessing WMI information. Note that while most of these examples use Get-WMIObject, many of the PowerShell WMI cmdlets have the same parameters, such as -Class or -Credentials. Therefore, many of these processes also work for other objects. For a more in-depth discussion of PowerShell and WMI, see Using the Get-WMiObject Cmdlet and Windows PowerShell - the WMI Connection.

  • VBScript, in contrast, explicitly makes calls to the Scripting API for WMI, as mentioned above. Other languages, such as Perl, can also use the scripting API for WMI. However, for the purposes of this documentation, most samples that demonstrate the scripting API for WMI will use VBScript. When a programming technique is specific to VBScript, however, it will be called out.

    VBScript has essentially two separate ways of accessing WMI. The first is using an SWbemLocator object to connect to WMI. Alternately, you can use GetObject and a moniker. A moniker is a string that can describe a number of elements: your credentials, impersonation settings, what computer you want to connect to, the WMI namespace (ie, the general location where WMI stores groups of objects), and what WMI object you want to retrieve. Many of the examples below describe both techniques. For more information, see Constructing a Moniker String and Describing the Location of a WMI Object.

    Regardless of what technique you use to connect to WMI, you will likely retrieve one or more objects from the Scripting API. The most common is SWbemObject, which WMI uses to describe a WMI object. Alternately, you may use an SWbemServices object to describe the WMI service itself, or an SWbemObjectPath object to describe the location of a WMI object. For more information, see Scripting with SWbemObject and Scripting Helper Objects.

Using WMI and a Scripting Language, How Do I...

...connect to WMI?

For VBScript and the Scripting API for WMI, retrieve an SWbemServices object with a moniker and a call to GetObject. Alternately, you can connect to the server with a call to SWbemLocator.ConnectServer. You can then use the object to access a specific WMI namespace or WMI class instance.

For PowerShell, connecting to WMI is generally done directly in the cmdlet call; as such, no additional steps are necessary.

For more information, see Describing the Location of a WMI Object, Constructing a Moniker String, and Connecting to WMI with VBScript.


Set objLocator = CreateObject("WbemScripting.SWbemLocator")
Set objService = objLocator.ConnectServer(".", "root\cimv2")

' Second example: implicitly uses the local compuer (.) and default namespace ("root\cimv2")
Set objWMIService = GetObject("winmgmts:")

...retrieve information from WMI?

For VBScript and the Scripting API for WMI, use a retrieval function, such as WbemServices.Get or WbemServices.InstancesOf. You may also place the class name of the object to retrieve in a moniker, which may be more efficient.

For PowerShell, use the -Class parameter. Note that -Class is the default parameter; as such, you don't need to explicitly state it.

For more information, see Retrieving WMI Class or Instance Data.


Set objLocator = CreateObject("WbemScripting.SWbemLocator")
Set objService = objLocator.ConnectServer(".", "root\cimv2")
Set colScheduledJobs = objService.InstancesOf("Win32_ScheduledJob")

' Second example
SSet Service = GetObject("WinMgmts:{impersonationLevel=impersonate}!Win32_Service=""ALERTER""")

...create a WMI query?

For VBScript and the Scripting API for WMI, use the SWbemServices.ExecQuery method.

For PowerShell, use the -Query parameter. You can also filter using the -Filter parameter.

For more information, see Querying WMI.


strComputer = "."
Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
Set colScheduledJobs = objWMIService.ExecQuery("Select * from Win32_ScheduledJob")
For Each objJob in colScheduledJobs
    Wscript.Echo "Job ID: " & objJob.JobId & "Command: " & objJob.Command & VBNewLine

...enumerate through a list of WMI objects?

For VBScript and the Scripting API for WMI, use the SWbemObjectSet container object, which is treated in script as a collection that can be enumerated. You can retrieve an SWbemObjectSet from a call from SWbemServices.InstancesOf or SWbemServices.ExecQuery.

PowerShell is able to retrieve and handle enumerations as it would any other object; there is nothing particularly unique to WMI.

For more information, see Accessing a Collection.


For Each Disk In GetObject("winmgmts:").InstancesOf ("CIM_LogicalDevice")

...access a different WMI namespace?

For VBScript and the Scripting API for WMI, state the namespace in the moniker, or else you can explicitly state the namespace in the call to SwbemLocator.ConnectServer.

For PowerShell, use the -Namespace parameter. The default namespace is "root\cimV2"; however, many older classes are stored in "root\default".

To find the location of a given WMI class, look at the reference page. Alternately, you can manually explore a namespace using get-WmiObject.


Set objLocator = CreateObject("WbemScripting.SWbemLocator")
Set objService = objLocator.ConnectServer(".", "root\cimv2")

' Second example
Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" & "." & "\root\cimv2")

...retrieve all child instances of a class?

For languages that directly use the Scripting API for WMI and PowerShell, WMI supports retrieving the child classes of a base class. As such, in order to retrieve the child instances, you need to only search for the parent class. The following example searches for CIM_LogicalDisk, which is a preinstalled WMI class that represents logical disks on a Windows-based computer system. As such, searching for this parent class also returns instances of Win32_LogicalDisk, which is what Windows uses to describe hard drives. For more information, see Common Information Model. WMI supplies an entire schema of such preinstalled classes that allow you to access and control managed objects. For more information, see Win32 Classes and WMI Classes..


For Each Disk In GetObject("winmgmts:").InstancesOf ("CIM_LogicalDisk")
  WScript.Echo "Instance:", Disk.Name

...locate a WMI object?

For both the Scripting API for WMI and PowerShell, WMI uses a combination of namespace, class name, and key properties to uniquely identify a given WMI instance. Together, this is known as the WMI object path. For VBScript, the SWbemObject.Path_ property describes the path for any given object returned by the scripting API. For PowerShell, every WMI object will have a __PATH property. For more information, see Describing the Location of a WMI Object

In addition to namespace and class name, a WMI object will also have a key property, which uniquely identifies that instance compared to other instances on your machine. For example, the DeviceID property is the key property for the Win32_LogicalDisk class. For more information, see Managed Object Format (MOF).

Finally, the Relative path is simply a shortened form of the path, and includes the class name and key value. In the examples below, the path may be "\\computerName\root\cimv2:Win32_LogicalDisk.DeviceID="D:"", while the relative path would be ""Win32LogicalDisk.DeviceID="D""".


For Each Disk In GetObject("winmgmts:").InstancesOf ("CIM_LogicalDisk")
  WScript.Echo "Instance:", Disk.Path_.Relpath

'or to get the path
For Each Disk In GetObject("winmgmts:").InstancesOf ("CIM_LogicalDisk")
  WScript.Echo "Instance:", Disk.Path_


...set information in WMI?

For VBScript and the Scripting API for WMI, use the SWbemObject.Put_ method.

For PowerShell, you can either use the Put method, or else Set-WmiInstance.

For more information, see Modifying an Instance Property.


wbemCimtypeString = 8
Set objSWbemService = GetObject("Winmgmts:root\default")
Set objClass = objSWbemService.Get()
objClass.Path_.Class = "NewClass"

' Add a property
' String property
objClass.Properties_.add "PropertyName", wbemCimtypeString  
' Make the property a key property 
objClass.Properties_("PropertyName").Qualifiers_.add "key", true

' Write the new class to the root\default namespace in the repository
Set objClassPath = objClass.Put_
WScript.Echo objClassPath.Path

'Create an instance of the new class using SWbemObject.SpawnInstance
Set objNewInst = GetObject("Winmgmts:root\default:NewClass").Spawninstance_

objNewInst.PropertyName = "My Instance"

' Write the instance into the repository
Set objInstancePath = objNewInst.Put_
WScript.Echo objInstancePath.Path


...use different credentials?

For VBScript and the Scripting API for WMI, use the UserName and Password parameters in the SWbemLocator.ConnectServer method.

For PowerShell, use the -Credential parameter.

Note that you can only use alternate credentials on a remote system. For more information, see Securing Scripting Clients.


strComputer = "remoteComputerName" 
strDomain = "DOMAIN" 
Wscript.StdOut.Write "Please enter your user name:"
strUser = Wscript.StdIn.ReadLine 
Set objPassword = CreateObject("ScriptPW.Password")
Wscript.StdOut.Write "Please enter your password:"
strPassword = objPassword.GetPassword()
 
Set objSWbemLocator = CreateObject("WbemScripting.SWbemLocator")
Set objSWbemServices = objSWbemLocator.ConnectServer(strComputer, _
                                                     "Root\CIMv2", _
                                                     strUser, _
                                                     strPassword, _
                                                     "MS_409", _
                                                     "ntlmdomain:" + strDomain)
Set colSwbemObjectSet = objSWbemServices.ExecQuery("Select * From Win32_Process")
For Each objProcess in colSWbemObjectSet
    Wscript.Echo "Process Name: " & objProcess.Name 
Next

...access a remote computer?

For VBScript and the Scripting API for WMI, explicitly state the name of the computer in either the moniker, or else in the call to SWbemLocator.ConnectServer. For more information, see Connecting to WMI Remotely with VBScript.

For PowerShell, use the -ComputerName parameter. For more information, see Connecting to WMI Remotely with PowerShell.


Set objLocator = CreateObject("WbemScripting.SWbemLocator")
Set objService = objLocator.ConnectServer("myRemoteServerName", "root\cimv2")
Set colScheduledJobs = objService.ExecQuery("SELECT * FROM Win32_ScheduledJob")
For Each objJob in colScheduledJobs
    Wscript.Echo "Job ID: " & objJob.JobId & "Command: " & objJob.Command & VBNewLine

'example 2

strComputer = "myRemoteServerName"
Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
Set colScheduledJobs = objWMIService.ExecQuery("Select * from Win32_ScheduledJob")
For Each objJob in colScheduledJobs
    Wscript.Echo "Job ID: " & objJob.JobId & "Command: " & objJob.Command & VBNewLine

...set the Authentication and Impersonation levels?

For VBScript and the Scripting API for WMI, use the SWbemServices.Security_ property on the returned server object, or else set the relevant values in the moniker.

For PowerShell, use the -Authentication and -Impersonation parameters, respectively. For more information, see Securing Scripting Clients.

For more information, see Securing Scripting Clients.



' First example
Set Service = GetObject("WinMgmts:{impersonationLevel=impersonate}!Win32_Service=""ALERTER""")

' Second example
Set Locator = CreateObject("WbemScripting.SWbemLocator")
Set Service = Locator.ConnectServer       
service.Security_.ImpersonationLevel = wbemImpersonationLevelImpersonate  
Set objinstance = Service.Get("Win32_Service=""ALERTER""")

...handle errors in WMI?

For the Scripting API for WMI, the provider may supply an SWbemLastError object to give further information on an error.

In VBScript in particular, error handling is also supported using the native Err object. You may also access the SWbemLastErrorobject, as described above. For more information, see Retrieving an Error Code.

For PowerShell, you can use the standard PowerShell error handling techniques. For more information, see An Introduction to Error Handling in PowerShell.



'using Err
On Error Resume Next
Set objProcess = GetObject("winmgmts:root\cimv2:Win32_Process.Handle='one'")
Wscript.Echo Err.Number

'using SWbemLastError

On Error Resume Next
Set obj = GetObject("winmgmts:root\cimv2:Win32_Process.Handle='one'")
Set LastError = createobject("wbemscripting.swbemlasterror")
Wscript.Echo "Operation = " & LastError.operation & VBCRLF & "ParameterInfo = " _
            & LastError.ParameterInfo & VBCRLF & "ProviderName = " & LastError.ProviderName


 

 

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