Category: Powershell

Klaas Vandenberghe notes a discrepancy in how Measure-Object works, based on syntax:

So, is the -InputObject parameter broken? Not really, but we need to be aware of the logic behind it.
Maybe we are used to work with -ComputerName for a lot of cmdlets and functions, and we rely blindly upon the ability of the command to handle whatever collection we provide. We know this executes the action we chose, like Get-DbaSqlService or Get-DbaOperatingSystemor whatever, separately to every computer in the collection. The collection is ‘fold out’, ‘unpacked’, ‘split’.

-InputObject doesn’t do that! Is that wrong? Not necessarily, it may be a choice of design to have possibilities to enquire the properties of the collection itself and those of the ‘members’ or ‘children’. It’s just a surprise the behaviour differs from pipeline input to parameter input.

Something to keep in mind when writing Powershell scripts.

Jeff Hicks shows off some of the niceties of Powershell’s ConvertTo-HTML cmdlet:

This is because Convertto-Html, like Export-CSV and Export-Clixml, take the entire object. This is not just the default result you see on the screen. Remember, everything will be treated as a string. In my example, if I want a similar HTML file, I will have to recreate the output with Select-Object. This might require piping the original result to Get-Member to discover the “real” property names.

It won’t output beautiful results, but with the appropriate CSS theming, you can generate good internal reports.

Chrissy LeMaire shows how to save the dbatools module to install it offline:

There are essentially 3 ways to get the zip of our module

1. From PowerShell Gallery using Save-Module

2. From PowerShell Gallery by downloading from powershellgallery.com/api/v2/package/dbatools

3. By downloading from dbatools.io/zip

Read on to see examples for each of the three methods.

Adam Bertram shows how to write safer code by validating parameters:

Simply adding [Parameter()] to the parameter block makes this function “advanced.” Once we have this in place, we can then add in some parameter validation code. In our case, we need to ensure that the file provided with FilePath actually exists before proceeding. To do this, we’ll use the ValidateScript attribute which allows us to run any code we want. As long as it returns $true, it will allow the function to run.

function Set-File {
param(
[Parameter()]
[ValidateScript({ Test-Path -Path $_ -PathType Leaf})]
[string]$FilePath
)
}

Notice that I used the pipeline variable $_ in this example. This represents whatever value the parameter is. If the user provides a file path that does not exist, they will be notified.

Read the whole thing.

Klaas Vandenberghe shows some of the pattern matching and regular epxression functionality within Powershell:

This is like grep if you ever encountered that. The Select-String cmdlet finds a -pattern in text.
It has an -allmatches switch to … guess what 🙂

Get-ChildItem D:\Myscripts -File -Recurse *.sql | Select-String -pattern "drop\s+[?(database|table|login)"

will get us all our sql scripts in which we drop a database, table or login.
The returned MatchInfo object holds the matching parts of the script text, and also the name of the file and the line number where the match was found.

Get-ChildItem | Select-String is my most frequently used Powershell pipeline.