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Showing posts from May, 2013

PowerShell 3.0 Workflow Secret Sauce

I was poking around in workflows and stumbled across this when I looked at a workflows definition and saw a large PowerShell scriptblock. I'm sure some of you will find this as interesting as I did. Actually, this explains a lot about workflows and how and why they behave the way they do. Enjoy!

Note: fu was the actual workflow name I used just to look at an empty defined workflow, e.g. workflow fu {}; then use this to see the properties of the workflow: gci function:fu | fl *

Below is what is in the ScriptBlock property.
[CmdletBinding()]                  param (                      [hashtable[]] $PSParameterCollection,                      [string[]] $PSComputerName,                      [ValidateNotNullOrEmpty()] $PSCredential,                      [uint32] $PSConnectionRetryCount,                      [uint32] $PSConnectionRetryIntervalSec,                      [ValidateRange(1, 2147483)][uint32] $PSRunningTimeoutSec,                      [ValidateRange(1, 2147483)][uint32] $PSE…

PowerShell Error Handling Behavior Debunked

Note: I am using simple error messages as an example, please reference the best practices and guidelines I outlined on when to use custom error messages.

I have been churning in my mind for the last few days all the entries in the 2013 Scripting Games and how they handle errors, or lack thereof.

I am coming to the conclusion through some testing that the simple fact of seeing a try..catch or throw statements does not mean there is proper error handling.

I've been testing several variations and forms of error handling, so lets start with the basics.
function Test-WriteError {      [CmdletBinding()] param()  "Test-WriteError::ErrorActionPreference = $ErrorActionPreference"Move-Item -Path 'C:\Does\Not\Exists.log' -Destination 'C:\No\Where'"Test-WriteError::End"}   Test-WriteError::ErrorActionPreference = Continue
Move-Item : Cannot find path 'C:\Does\Not\Exists.log' because it does not exist.
At line:6 char:5
+     Move-Item -Path 'C:\Does\N…

PowerShell - 2013 Scripting Games Advanced Event 1 - Error Handling

One more suggestion I received on my entry was better error handling. If you didn't get this already, but I am a naturalist when it comes to PowerShell, e.g. let PowerShell do the heavy lifting and what it does naturally best.

Though, thinking through possible error conditions in my script, I do have opportunities for improvement. Namely around the scenario where the target directory could not be created by New-Item, the script continues on when that really is a terminating error and should stop.

I've been reading peoples feedback and other blog posts about how to handle errors with this event. I saw a few people very passionately advocate for Write-Warning as a better solution than Write-Error. Write-Warning is not a suitable replacement for Write-Error, they have two very specific meanings for the user.

While I agree, the implied usage of each could leave this error gray, I think it is easy to set a few best practices I think everyone could agree with.

Write-Warning should be…

PowerShell SupportsShouldProcess Worst & Best Practices

This has been a very big discussion within the Scripting Games 2013 community and I want to add my two cents in an official blog post.

I've left several people comments on how they might be misunderstanding how SupportsShouldProcess works, but I also realize, everyone of these individuals has given me more insight into its use and perhaps, how it should best be utilized.

For those of you that don't know, SupportsShouldProcess is a parameter on the CmdletBinding attribute you can place on your cmdlets that automatically adds the -WhatIf and -Confirm parameters. These will naturally flow into other cmdlets you use that also SupportsShouldProcess, e.g. New-Item, Move-Item.

The major discussion has been around, should you just let the other cmdlets handle the $PSCmdlet.ShouldProcess feature, and if not how should you implement it. ShouldProcess has the following definitions.