Category: Powershell

Allison Tharp is starting to learn Powershell:

PowerShell is developed by Microsoft, specifically for task automation and configuration management.  A shell is a user interface that gives the user access to services of an operating system.  The shell you are likely most familiar with is the Command Prompt.  PowerShell is like the Command Prompt in many ways, but it is much more powerful.

PowerShell is based on the .Net framework and is considered a scripting language.  Windows also developed the Windows PowerShell ISE (Integrated Scripting Environment).  This is a GUI that lets us make scripts without having to type all of the commands into the command line.

I highly recommend learning Powershell if you’re in the Windows administration space.  It’s not quite as useful on the development side (where you can quickly throw together a .NET app) but it’s great for scripting out those admin tasks.

Ed Elliott has a new Powershell module named DacFxed:

There is a solution? Well yes of course otherwise I wouldn’t have been writing this! DacFxed is a powershell module which:

• 1. References the DacFx nuget package so updating to the latest version is simple
• 2. Implements a hack (ooh) to allow contributors to be loaded from anywhere
• 3. Is published to the powershell gallery so to use it you just do “Install-Module -Name DacFxed -Scope User -Force”
• 4. Has a Publish-Database, New-PublishProfile and Get-DatabaseChanges CmdLets

Cool right, now a couple of things to mention. Firstly this is of course open source and available: https://github.com/GoEddie/DacFxed

This is a nice tool to deploy dacpac files using Powershell.  Check out the GitHub repo for more details.

Michael Bourgon has a few Powershell snippets he wrote this week:

I needed to parse out a Unix filename from a file.  The original “ls” looked like this:

-rw-rw-r– 1 psabcderfg data 646621 Jul 19 16:25 myfile16071901.Z

The unix command to parse it would
cat $fl |awk ‘{print $9}’

And the powershell equivalent is:
$newfiles = get-content $fl | foreach {$_.split(” “)[8]}
(the number is 8 instead of 9 because powershell arrays start at 0)

Check all of them out.

Phil Factor shows how to use Powershell’s push and pop methods to create an expression evaluator:

I use stacks for writing expression analysers. Generally I like at least two stacks, probably up to four. They tend to be different sizes and may have other differences. If written as objects, the code becomes much cleaner and easier to read. Why do I write expression analysers? You might imagine that you would never need such a thing, but once you have one, reasons for using it just keep appearing. They are handy for parsing document-based hierarchical data structures, for parsing grammars and for creating Domain-Specific Languages (DSLs). A DSL is handy when you’re writing a complex application because it cuts down dependencies, and allows you to develop scripts for complex workflows without recompiling .

What I describe here is a cut-down version of what I use, just to illustrate the way of creating and using stacks. I extend this basic algorithm, originally from Dijstra’s shunting algorithm, into a complete language interpreter. All it needs is a third stack to implement block iterations and ‘while’ loops. Why not use PowerShell itself as your DSL? I’ve tried that, but my experience is that it is pretty-well impossible to eliminate script-injection attacks, and I also find that there isn’t quite enough control.

For a more prosaic usage of the stack in Powershell (as well as bash), you can push your current location, move to a new directory, perform some action in that new directory, and pop your old location off the stack to go back to where you were before.  This is particularly useful for those Powershell modules and cmdlets which leave you in a different directory from where you started.