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New to Powershell? Let me jot down a few good-to-know things. Some you already know. Some might save you hours of googling.

Use Set-StrictMode -Version 2.0.

Powershell 5.1 is the last Windows Powershell. From 6 it runs on Dotnet core and more platforms.

Use Pester for automatic testing. It runs tests and can mock. Note that mocking works differently in Powershell than C# as they load code in different ways.

Don’t patch together your Powershell scripts. Use the systems thinking you usally do and create a sturdy, thought out, solution with bricks of the right size. Just like you would any other solution.

For caveats let me explain the file below, row by row.

File JustASimpleScript.ps1

$temp

$temp = ‘LocalVariable’

function LocalFunction( $foo, $bar ){
Write-Host “Local variable is $temp.”
$foo    # The last executed row is returned.
}

LocalFunction ‘MyParameter’

Enter the above in your favourite text editor. Save it as JustASimpleScript.ps1. Open a console and navigate to the proper folder. Execute Powershell to get Powershell started. Then execute .\JustASimpleScript.ps1′. The result shows both an exception and some more proper output.

Set-StrictMode is like `option explicit` in old VB6, it throws an error if you try to evaluate a variable that has not been set, that parenthesises are not used when calling functions and called methods do exist.
No code example at Stackoverflow shows it and almost no blog article.

Variables are recognised by the leading dollar sign.

As we used Set-StrictMode above this row throws an exception. But… the program continues to run!

Strings are delimited with apostrophes. Quotation works but is over kill, see below.

Nothing special about declaring a function like this. Declare a function with parenthesises but call it without; it is very easy to get this wrong. Also; the parameters are optional by default.

Write-Host is the normal way of outputting text in the console. If it is the correct way is another discussion I won’t dive into without more knowledge.

Also note the quotation marks. They mean that anything that looks like a variable inside should be evaluated. Just like PHP. Just like C# by prefixing a string with $. Many online examples use quotation marks for every string. By the time of writing I consider that less good.

To fool newbies, Powershell implicitly returns the last executed row with an output. I suggest to make it more readable, prefix with return like so:

Comments starts with a # sign.

Stuff within curly brackets are a code block. A code block is not only the contents of a method or an if statement but can also be passed around, like a() => {…} lambda in C#.

This ia a method call. As long as it is Powershell leave out the parenthesises. Otherwise you have converted your list of parameters to a single parameter call and the single parameters is a list. This rule is not hard to remember but reading code that calls method with lists as parameters is hard to grasp for a newbie. Adding insult to injury, calling a C# method from Powershell might change the rule.

Using a file like this, ending in ps1 is typically done by “dot sourcing”. It is quick, dirty and pollutes the global name space. Things you would never to in your “regular language”.

A call like below makes the contents live only just in the call.

If you want to make the $temp variable and the LocalFunction live on you start it with yet a period and a space like so:

But probably you want to make a module instead. Which you find in part 2.

Finally, don’t forget:

• Think System.
• Use automatic tests.
• Use Set-StrictMode -Version 2.0.

Tags: Powershell