Windows PowerShell Cmdlets
Introduction to Windows PowerShell Cmdlets
With PowerShell you have a choice, you can either type commands directly at the shell's command line, or else you can store the same commands in a text file. Naturally, you then call that script file, known as a cmdlet, from the PowerShell command line, or in the ISE (Integrated Scripting Environment).
As with other script languages, notepad is an alternative vehicle for writing or editing scripts, the only specific requirement is that you must save the cmdlet with the PowerShell extension of .ps1. Writing scripts has two extra benefits, it documents your commands, so that you don't forget them, and also, these cmdlet files provide a record of your PowerShell achievements.
PowerShell Cmdlet Topics
PowerShell Cmdlets (Command Lets)
First Meaning of
Second Meaning of
My tactic is once my lines of code achieve my basic objective, I call for 'SaveAs', and then use the copy for further development. Seven times out of ten the 'development' goes hopelessly wrong, at which point I am so grateful that I saved a working copy.
I hope that you are getting the idea of a cmdlet. Spend time perfecting the PowerShell commands, then save them in a text file. This technique saves you typing in lines of code and the command line, instead, you call the cmdlet by typing: dot slash and followed by its filename, for example .\memory. Incidentally, building PowerShell cmdlets fits in with my strategy of assembling scripts in sections.
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Creating PowerShell Cmdlets - Quick Instructions
Creating these Windows PowerShell cmdlets is straightforward, and most rewarding. Here are the three essential tasks to ensure that the instructions in these script files execute correctly.
Note 1: Let me explain, this is how I like to call cmdlets from a subdirectory. D: \scripts is my main script directory, however, I create cmdlets in subdirectories such as: D: \scripts\wmi\32proc.ps1 . Assuming that I am at the PowerShell command line in the D: \scripts folder, all that I type at the prompt is: .\wmi\32proc.
Note 2: It took me ages to deduce that all I needed was plain .\filename. Avoid over-think, when you call the cmdlet file you don't need to add the extension. Adding .ps1 is not necessary .\filename will suffice.
Note 3: While this dot slash (.\) method of executing the cmdlet script seems cumbersome, Microsoft decided on this method for security reasons. Hackers, phishers and the like could trick people into executing a rogue PowerShell script by clicking on it. However, nothing happens - unless you proceed the script with .\ this safety feature offers a measure of protection from such mischief makers.
The following instructions are the same as those above, but with extra step-by-step directions.
1a) PowerShell's ExecutionPolicy Command
I prefer this method, which employs PowerShell's own commands to control the script Execution Policy. At the PS prompt try the following 3 commands:
# PowerShell Set-ExecutionPolicy
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1b) PowerShell Registry Adjustment
For security, and by default, Microsoft prevent PowerShell from executing cmdlet scripts; consequently we need to change a specific registry setting to allow our cmdlets to execute. If you don't make my amendment you may get the following error message when you call for a cmdlet script. 'The execution of scripts is disabled on this system'.
Our task is to open the registry and amend the value of the REG_SZ ExecutionPolicy, specifically change Restricted to RemoteSigned. There are two additional values called Unrestricted and AllSigned. However, RemoteSigned is the best because it allows you to run scripts locally, while preventing people from hacking you from other machines e.g. the internet. To check the setting launch regedit and navigate to:
(In some versions of
PowerShell the path
maybe slightly different.
Change this registry key:
Filename and .ps1 extension
When you create your PowerShell cmdlet with notepad, the filename must have a .ps1 extension for example, RunningProcess.ps1. One way of creating such a file is to save your PowerShell commands in notepad, then from the file menu: Save As, Type, All Files, RunningProcess.ps1. Just to be doubly sure, you could put the filename in double quotes, for example: "RunningProcess.ps1". I maybe paranoid, but please check the file is not called RunningProcess.txt or RunningProcess.ps1.txt.
What you put in filename.ps1
are the same commands that you type in the PowerShell box. You could start
by creating a file with a simple Verb-Noun
pair, for example just:
This may seem too simple, but my philosophy is keep things straightforward and build on success.
Here is a more advanced set of instructions just to give you the idea of the joy of creating a PowerShell script.
# This script generates a report about Running Services