PowerShell provides a tremendous boon to productivity for computer professionals of all types. But, you have to admit: it can be a bit daunting to get up to speed! Indeed, as someone who has a fair amount of experience using it, I still find myself having to look up how to do things–frequently. So I started keeping track of the recipes I was using the most. And came up with a list of 400 or so, published in 4 parts.
If you haven’t taken a look at Tug, now’s a great time. Eugene Bekker has been doing a ton of heavy lifting, taking my .NET Core proof-of-concept code and turning it into a formal ASP.NET MVC project.
You can certainly find a number of articles around that present PowerShell pitfalls that can easily trip you up if you are not careful. I took a different approach in my three-part series, A Plethora of PowerShell Pitfalls. The first two parts are presented in quiz format, together covering the top 10 “gotchas”. They will help you test your awareness to see if you even realized the danger and did not know you’ve been skirting those traps for awhile. After you’ve had an opportunity to consider the conundrums presented, I then go into detailed explanations for why they happen and how to fix them. The third and final part is a compendium of all the common “gotchas” that I put together after reviewing all the other lists out there. The more than 35 entries in the list cover, I believe, a good 98% of the issues you would likely encounter. Yes, there are more esoteric pitfalls as well, but I ran out of web page… 🙂 Part 1: Pesky Parameter Problems Part 2: A Portion of Potential Puzzles Part 3: The Compendium
Pipelining is an important concept in PowerShell. Though the idea did not originate with PowerShell (you can find it used decades earlier in Unix, for example), PowerShell does provide the unique advantage of being able to pipeline not just text, but first-class .NET objects. Pipelining has several advantages:
It helps to conserve memory resources. Say you want to modify text in a huge file. Without a pipeline you might read the huge file into memory, modify the appropriate lines, and write the file back out to disk. If it is large enough you might not even have enough memory to read the whole thing.
It can substantially improve actual performance. Commands in a pipeline are run concurrently-even if you have only a single processor, because when one process blocks, for example, while reading a large chunk of your file, then another process in the pipeline can do a unit of work in the meantime.
It can have a significant effect on your end-user experience, enhancing the perceived performance dramatically. If your end-user executes a sequence of commands that takes 60 seconds, then until 60 seconds has elapsed he/she would see nothing without pipelining, whereas output could start appearing almost immediately with pipelining.
PowerShell provides a variety of techniques for using pipelining but it is all to easy to do it wrong, so you think you are pipelining but in fact you are not. In my article Ins and Outs of the PowerShell Pipeline, I discuss the most common things that can trip you up with implementing pipelining and how to avoid them.
Sometimes, as a developer, you want to be be able to keep track of free space on a drive, the size of a log, the load on your CPU, the number of users logged in, etc. With PowerShell, it is typically just a matter of finding the right cmdlet amidst the large (and rapidly growing) pool of cmdlets provided by Microsoft and by third parties. Then you just run Get-Foo to check details about the foo resource. And then you come back 5 minutes later and run it again because you want to see how it changes over time. But wouldn’t it be nice if you could just have it run automatically at regular intervals in a separate window that you could just keep in the corner of your screen? Well, I found the barebones of just such a utility sometime ago (authored by Marc van Orsouw, aka ‘thePowerShellGuy’). His original post is no longer available, but I expanded upon his code and, over time, added features, bug fixes, and enhancements, making it more useful and more user-friendly. Here are a few screenshots of the Monitor Factory in action. Monitor the size of a database
For those of you that have been at PowerShell Summits over the last few years you’ll have heard Jeffrey Snover state that he wanted to take PowerShell to other platforms.
Now its happened
Jeffrey has announced that an ALPHA release of PowerShell is now available for Linux and Mac. Currently available for Ubuntu, Centos, Red Hat and Mac OS X with more to come
“To be or not to be”. Without getting into a debate over whether Shakespeare was musing about being a logician, suffice to say that in writing prose, the rules of when and how to use quotation marks are relatively clear. In PowerShell, not so much. Sure, there is an about_Quoting_Rules documentation page, and that is a good place to start, but that barely covers half the topic. It assumes you need quotes and then helps you appreciate some of the factors to consider when choosing single quotes or double quotes. But do you need quotes? Remember PowerShell is a shell/command language so “obviously” you can do things like this:
So you’ve decided to write a bunch of commands to help automate the administration of ____. Awesome! Let’s try and make sure you get off on the right path, with this high-level overview of command design.
Start with an inventory
You’ll need to start by deciding _what commands to write, _and an inventory is often the best way to begin. Start by inventorying your nouns. For example, suppose you’re writing a command set for some internal order-management system. You probably have nouns like Customer, Employee, Order, OrderItem, CustomerAddress, and so on. Write ’em all down in an Excel spreadsheet, one noun per row. Then inventory your verbs. For each noun, what can you do with it? For example, you can probably create orders, so a New-Order command will be needed. Make a “New” column in your spreadsheet, and put an “X” in the row next to the Order noun. However, you probably can’t remove an order from the system, so although your spreadsheet might have a “Remove” column to cover things like Remove-Employee, that column won’t get an “X” in the Order row. Orders might be voidable, though, so what’s a good verb for that? https://msdn.microsoft.com/en-us/library/ms714428(v=vs.85).aspx has the official verb list, but there’s no “Void” or “Cancel” that seems appropriate. Don’t go making up new verbs!!! Instead, it might be that Set-Order could be the answer, enabling approved changes to orders, including cancelling them (but retaining the record). Finally, pick a prefix for your nouns. If your order system is named “Order Awesomeness,” then maybe OAwe is a good noun prefix, as in Set-OAweOrder. The prefix will help keep your command names from bumping up against other people’s, so making sure that noun prefix is pretty unique… is pretty important.
Quick as you can, can you explain what each of these different parentheses-, brace-, and bracket-laden expressions does?
${save-items} ${C:tmp.txt} $($x=1;$y=2;$x;$y) (1,2,3 -join '*') (8 + 4)/2 $hashTable.ContainsKey($x) @(1) @{abc='hello'} {param($color="red"); "color=$color"} $hash['blue'] [Regex]::Escape($x) [int]"5.2" When you’re reading someone else’s PowerShell code, you will come across many of these constructs, and more. And you know how challenging it can be to search for punctuation on the web (symbolhound.com not withstanding) ! That is why I put together a reference chart containing all of PowerShell’s symbology on one page. making it much easier when you need to look up a PowerShell symbol as you read code–or to browse for the right construct when you are writing code. Download the Complete Guide to PowerShell Punctuation wallchart from here.
