Category Archives: string manipulation

13Dec/17

Formatting Strings In PowerShell Using Fixed Width Columns

Working with strings in PowerShell is fun, I don’t care what you say. In this post, I’m going to show you how to clean up the strings your code outputs, at least in some situations.

Say you have a variable $fileExtensions which you populated with this command.

And, for some reason, instead of the default output which is formatted like a table, I want output presented like this.

This is a silly example, but notice that even though there are extensions of varying length (.ps1 and .dll are four characters including the dot, and .xlsx is five), all of the “file extension: <number>” is aligned.

How’d I do that? Let’s start with some code that doesn’t work.

How incredibly unfortunately unattractive! Luckily, it’s not too hard to fix. Check out this code.

Oh yes look at that goodness. In this example I’m using the -f  operator to insert the variables into the string. Let’s break down the new string I’m creating.

{0} and {1] are basically placeholders. The -f operator is going to insert the variables that come after it ($_.Name and $_.Count) into the 0 and 1 spots.

The ,-8 is a formatting instruction. The 8 means that this part of the string is going to be a column that takes up 8 characters worth of space. The negative sign means that the data inserted is left aligned. If I had used “positive eight” it would have been right aligned.

Now you can take this and run, to do fun things like this.

29Nov/17

Beginner PowerShell Tip: Using Variable Properties In Strings

If you’re just getting started in PowerShell, it’s possible that you haven’t bumped into this specific issue yet. Say you’ve got a variable named $user and this is how you assigned a value to it.

Using the Active Directory module, you got a specific user. Now, you want to report two properties back to the end user: SamAccountName and Enabled. The desired output looks like this:

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11Oct/17

What’s the difference between -split and .split() in PowerShell?

Here’s a question I see over and over and over again: “I have a string and I’m trying to split it on this part, but it’s jumbling it into a big mess. What’s going on?” Well, there’s splitting a string in PowerShell, and then there’s splitting a string in PowerShell. Confused? Let me explain.

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13Sep/17

Piping PowerShell Output Into Bash

With Windows 10, you can install Bash on Windows. Cool, right? Having Bash on Windows goes a long way towards making Windows a more developer-friendly environment and opens a ton of doors. The one I’m going to show you today is more of a novelty than anything else, but maybe you’ll find something neat to do with it.

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09Aug/17

Add A Column To A CSV Using PowerShell

Say you have a CSV file full of awesome, super great, amazing information. It’s perfect, except it’s missing a column. Luckily, you can use Select-Object along with the other CSV cmdlets to add a column.

In our example, let’s say that you have a CSV with two columns “ComputerName” and “IPAddress” and you want to add a column for “Port3389Open” to see if the port for RDP is open or not. It’s only a few lines of code from being done.

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28Dec/16

Does A String Start Or End In A Certain Character?

Can you tell in PowerShell if a string ends in a specific character, or if it starts in one? Of course you can. Regex to the rescue!

It’s a pretty simple task, actually. Consider the following examples

In the first two examples, I’m checking to see if the string ends in a backslash. In the last two examples, I’m seeing if the string starts with one. The regex pattern being matched for the first two is .+?\$ . What’s that mean? Well, the first part .+? means “any character, and as many of them as it takes to get to the next part of the regex. The second part \\ means “a backslash” (because \ is the escape character, we’re basically escaping the escape character. The last part $ is the signal for the end of the line. Effectively what we have is “anything at all, where the last thing on the line is a backslash” which is exactly what we’re looking for. In the second two examples, I’ve just moved the \\ to the start of the line and started with ^ instead of ending with $ because ^ is the signal for the start of the line.

Now you can do things like this.

Here, I’m checking to see if the string ‘bears’ ends in a backslash, and if it doesn’t, I’m appending one.

Cool, right?

26Oct/16

Quick Tip: Get All The Security Patches Installed On A Server Since A Specific Date

Recently, I needed to get a list of all the security patches I’d installed on a group of servers in the last year. It turns out that there’s a WMI class for this and it’s super easy to retrieve this info.

In the win32_quickfixengineering class, you’ll find all the security patches installed on a system. One of the properties is the InstalledOn attribute which more recent than a year ago.

If you have a list of servers to do this for, this is still really easy.

Just paste them into a here-string and execute this for each of them.

03Aug/16

Quick Tip: PowerShell Regex To Get Value Between Quotation Marks

If you’ve got a value like the following…

… that maybe came from the body of a file, was returned by some other part of a script, etc., and you just want the portions that are actually between the quotes, the quickest and easiest way to get it is through a regular expression match.

That’s right, forget splitting or trimming or doing other weird string manipulation stuff. Just use the [regex]::matches() feature of PowerShell to get your values.

Matches takes two parameters. 1. The value to look for matches in, in this case the here-string in my $s variable, and 2. The regular expression to be used for matching. Since Matches returns a few items, we are making sure to just select the value for each match.

So what is that regex doing? Let’s break it down into it’s parts.

  • (?<=\”) this part is a look behind as specified by the ?<= part. In this case, whatever we are matching will come right after a quote. Doing the look behind prevents the quotation mark itself from actually being part of the matched value. Notice I have to escape the quotation mark character.
  • .+? this part basically matches as many characters as it takes to get to whatever the next part of the regex is. Look into regex lazy mode vs greedy mode.
  • (?=\”) this part is a look ahead as specified by the ?= part. We’re looking ahead for a quotation mark because whatever comes after our match is done will be a quotation mark.

So basically what we’ve got is “whatever comes after a quotation mark, and as much of that as you need until you get to another quotation mark”. Easy, right? Don’t you love regex?