Hey, Scripting Guy! Quick-Hits Friday: The Scripting Guys Respond to a Bunch of Questions (12/25/09)

Hey, Scripting Guy! I have noticed that there are multiple ways to query a WMI object. I can use filter, query, where, and select. What is the difference? Does it depend on what you are querying, and is one faster than the other?

-- EJ

Hello EJ,

There are many ways of querying a WMI object. The one I use is the one that pops to mind at the time. If I am working interactively at the Windows PowerShell console, I will often use the alias for the Get-WmiObject cmdlet and the class parameter in the first position without naming the parameter. This is shown here:

Gwmi WIN32_bios

Using the gwmi alias and the WMI class name is faster than spelling out the gwmi alias with the –query parameter. This is seen here:

gwmi –query “Select * from WIN32_bios”

From a results standpoint, both the –query parameter and the -class parameter return the same objects.

The two commands are a lot faster than VBScript (even faster than Scriptomatic). Keep in mind the methods are the same. You may want to look at the WMI Week of Hey, Scripting Guy! articles.

At times, however, I need to use a particular method or functionality because of what I am doing. In general, I would say you should use the syntax that feels natural. When working at the Windows PowerShell command line, I almost never use the –query parameter anymore. I instead use –class filter. I seldom use –property to filter out properties; instead, I generally return the entire object and deal with it in the output in the pipeline. Here are examples of that:

Get-Wmiobject –class WIN32_process –property name
PS C:\> Get-Wmiobject -class WIN32_process -property name


__GENUS          : 2
__CLASS          : Win32_Process
__SUPERCLASS     :
__DYNASTY        :
__RELPATH        :
__PROPERTY_COUNT : 1
__DERIVATION     : {}
__SERVER         :
__NAMESPACE      :
__PATH           :
Name             : System Idle Process

__GENUS          : 2
__CLASS          : Win32_Process
__SUPERCLASS     :
__DYNASTY        :
__RELPATH        :
__PROPERTY_COUNT : 1
__DERIVATION     : {}
__SERVER         :
__NAMESPACE      :
__PATH           :
Name             : System

__GENUS          : 2
__CLASS          : Win32_Process
__SUPERCLASS     :
__DYNASTY        :
__RELPATH        :
__PROPERTY_COUNT : 1
__DERIVATION     : {}
__SERVER         :
__NAMESPACE      :
__PATH           :
<output truncated …>
Get-WmiObject –Class WIN32_Process | Select name
name
----
System Idle Process
System
smss.exe
csrss.exe
wininit.exe
csrss.exe
services.exe
<output truncated …>