{"id":16281,"date":"2010-12-08T00:01:00","date_gmt":"2010-12-08T00:01:00","guid":{"rendered":"https:\/\/blogs.technet.microsoft.com\/heyscriptingguy\/2010\/12\/08\/use-a-powershell-module-to-work-with-wmi-permanent-events\/"},"modified":"2010-12-08T00:01:00","modified_gmt":"2010-12-08T00:01:00","slug":"use-a-powershell-module-to-work-with-wmi-permanent-events","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/scripting\/use-a-powershell-module-to-work-with-wmi-permanent-events\/","title":{"rendered":"Use a PowerShell Module to Work with WMI Permanent Events"},"content":{"rendered":"

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Summary:<\/span><\/b> Learn how to use a Windows PowerShell module to work with WMI permanent events.<\/span><\/p>\n

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\"Hey,<\/span><\/span><\/span><\/span><\/span><\/span>Hey, Scripting Guy! Your posts this week on permanent event consumers have been really cool. I am wondering, if they are so useful, why there is not a Windows PowerShell cmdlet to allow one to interact with them?<\/span><\/p>\n

— ST<\/span><\/p>\n

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\"Hey,<\/span><\/span><\/span><\/span><\/span><\/span>Hello ST, Microsoft Scripting Guy Ed Wilson here. As a matter of fact, Trevor Sullivan was thinking the same thing. One of the great things about Windows PowerShell is that if you do not like it, you can change it. Another great thing is that if something is missing, you can frequently write your own. With Windows PowerShell 2.0<\/span><\/a> modules, the code that you write (or find) can be adapted to behave in the same manner as a Windows PowerShell cmdlet. I will let Trevor introduce himself and his module. Take it away.<\/span><\/p>\n

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Background<\/span><\/b><\/p>\n

Hello, my name is Trevor Sullivan. I’ve been working on a Windows PowerShell module recently that makes working with Windows Management Instrumentation (WMI) permanent event registrations much easier! The name of this module is PowerEvents<\/b> — appropriately named to combine Windows PowerShell and WMI eventing. You can download this module for free, from http:\/\/powerevents.codeplex.com<\/span><\/a>, and there is ample documentation in the form of a PDF document, YouTube videos, and the CodePlex.com wiki.<\/span><\/p>\n

There were several reasons that I began developing this module. First and foremost, I wanted to make working with WMI permanent event registrations easy from Windows PowerShell. Second, I have noticed over time that many people seem interested in responding to system-level events, by running some Windows PowerShell code, a VBScript, or an executable. Occasionally, I’ll come across forum<\/span><\/a> posts, or e-mails on a mailing list, where someone wants something to occur in response to an event. Usually the person knows what they want to respond to, and what they want to occur, but perhaps are unaware of WMI events. To summarize, the secondary reason I developed this module, was to help spread the knowledge of WMI events, and to help make them easier for people to understand. Perusing through developer documentation on MSDN is not always what people would consider “easy.”<\/span><\/p>\n

To satisfy the requirements of these requests, it is sometimes sufficient to use temporary event registrations in WMI. In Windows PowerShell, this is made quite easy using the Register-WmiEvent<\/b> cmdlet. This cmdlet is included in Windows PowerShell 2.0. It is also relatively easy to use temporary event registrations in a VBScript or C#<\/span><\/a> program. Nevertheless, you must write a fair amount of code to get these working. What is arguably the largest downside to using temporary event registrations, is that they only survive as long as the program (or, process) hosting them (eg. cscript.exe, if you are using a VBScript). <\/span><\/p>\n

Unlike temporary event registrations, permanent event registrations are created purely inside WMI. Because the WMI process (wmiprvse.exe) is running constantly as a background service, these event registrations are always in effect, unless you explicitly remove them. Be aware that this does not replace an enterprise monitoring solution, but with some creativity on your part, you can easily automate your IT environment. In fact, you could even use the same concepts to automate event-driven actions on your home computers!<\/span><\/p>\n

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About PowerEvents<\/span><\/b><\/p>\n

As previously discussed, PowerEvents<\/b> intends to make working with WMI permanent event registrations easy. To that end, it provides several Windows PowerShell advanced functions to create the three necessary WMI objects, to create an end-to-end event Registration:<\/span><\/p>\n