Category: Powershell

Missy Januszko has some tips on turning those Powershell scripts into reusable functions:

Breaking down your code may mean chopping apart your lengthy script into smaller pieces. As a best practice, a function should do only one thing. A retrieval cmdlet retrieves information and sends that information to the pipeline. Conversely, a functional cmdlet performs an act but not a retrieval act. It may take input from another cmdlet and act upon that input. It may or may not send output information to the pipeline. Lastly, output cmdlets format output in a desired display. As a result, this will allow us to use the pipeline more effectively to pass parameters between functions. In the above example, most of the function is a retrieval function. The exception is that it formats the output into a table with the last line. I will remove that line and let the user of the function decide how they want it formatted.

As a friendly warning to operations folks who are using more and more Powershell, when you do it right, you end up being a developer.  But we can keep that a secret, just between you and me.

Adam Bertram explains what hash tables are and why they’re useful:

Notice that each of the keys is unique. This is required in a hash table. It’s not possible to add two keys with the same name. Below I’ve defined the SomeKey2 key twice.

We’ve just talked about creating a hash table and adding key/value pairs at creation time. It’s also possible to add keys to an already created hash table in a number of different ways, either through dot notation, enclosing the key in brackets, or by using the Add() method. Each approach has the same effect.

Hash tables are quite useful in Powershell for storing key-value pairs, like if you’re building a dictionary of configuration settings.

Amy Herold has scraped PASS Summit 2017 submissions using Powershell:

Never having done a web scrape before, this was the perfect subject for my first time – grabbing all the sessions submitted to PASS Summit 2017…and doing it with PowerShell! Here is the script I used for this. I have accounted for the following:

• Apostrophes (aka single quote). They will break your insert unless you have two of them, and for some reason, people seem to use them all over the place.

• Formatting the string data for insert. No, your data will not magically come out right in your insert with single quotes so you need to add them.

• Additional ID and deleted fields.

• Speaker URL and ID. Will be using this to scrape speaker details later.

• Accurate lower and upper bounds. These were arrived at by trial and error (you’re welcome), as well as the clean up of the data I scraped. More on this later.

Powershell probably wouldn’t be my first language for web scrapes—that’d be Python—but Amy shows how to get a scrape going.

Adam Bertram explains the difference between the where-object and the where method in Powershell:

The Where-Object command is a sort of generic filtering command. Use this command to filter any kind of object in PowerShell. The Where-Object command has a FilterScript parameter, which is a scriptblock that allows the user to place code in it. If this scriptblock contains code that returns anything but $false, $null, or an empty string, it will allow whichever object the user passes to it.

For example, let’s say I’ve got a folder full of files. I’d like to see only text files and only those text files modified today. To make this happen, I can use the provider-specific filter with the Get-ChildItem command and also the Where-Object command.

Read on to see how that compares to the where method.  Given the latter’s limitations, I’ll probably stick to where-object anytime performance is not critical.

Claudio Silva shows how to re-run statements in your Powershell history:

While we were running some commands we talked about Get-History cmdlet.

For those who don’t know

this cmdlet lists all the commands that you already ran on the current session.

I wondered if it is possible to pipe the Get-History output and run it again. I could bet yes but I never tried before.

The answer is that yes, you can, and Claudio shows how.

Richie Lee has a method for checking whether a variable exists in Powershell:

Recently I needed to check that a variable exists in the PowerShell session currently running. This is actually far easier than it sounds. So here is a simple demo for how it works. The magic here is the “Test-Path variable:my_variable” on lines 4. It tests that a variable of that name exists. If it does, great, let’s print out the value. If not, let’s alert that it doesn’t. The second example of this on line 11 will do exactly that.

Read on to see Test-Path in action.

Amy Herold has a quick Powershell script to retrieve detailed system info (via msinfo32.exe) for a set of servers:

With this script you can generate system information files and save them to a specified location. It makes sure a connection can be made to the server first, and then outputs the file. The files are created one at a time, so if you pass in a longer list of servers, you shouldn’t crash your machine. From my testing, this will take some time to run as these files don’t output quickly. Despite that, the output is worth it. This can be modified to pull your list of servers from a file or from a Central Management Server (CMS) instance.

This is a useful script, with the next step being to turn it into a cmdlet that accepts the set of servers from the pipeline.