Topic: $PSDefaultParameterValues II

Notice: This post is a part of the PowerShell Monday series — a group of quick and easy to read mini lessons that briefly cover beginning and intermediate PowerShell topics. As a PowerShell enthusiast, this seemed like a beneficial way to ensure those around me at work were consistently learning new things about Windows PowerShell. At some point, I decided I would share these posts here, as well. Here’s the PowerShell Monday Table of Contents.

To recap last week, the $PSDefaultParameterValues preference variable stores default parameter names and corresponding values for cmdlets and functions. This means we can use cmdlets and functions with modified parameters, without the need to type in the names and values each time.

Last week we used the Add and Remove methods. This week, we’ll use standard hash table syntax, since that’s all this variable holds. Hash tables were first introduced back on May 30, 2016 when we first discussed creating and splatting a parameter hash table. A hash table contains key-value pairs.

Let’s add a new entry to our empty $PSDefaultParameterValues variable.

$PSDefaultParameterValues = @{'Get-Help:ShowWindow'=$true}
$PSDefaultParameterValues

Name                           Value
----                           -----
Get-Help:ShowWindow            True

Just as we did last, when we enter the variable name after it’s populated, it’ll return the results in the standard, hash table output to include the Name and Value properties.

With the ShowWindow parameter name set to a value of True, Get-Help will always show the full help inside a GUI window and not pollute the ConsoleHost or ISE (PowerShell 3.0 and greater only), without the need to actually type the switch parameter -ShowWindow.

If your variable is already holding a value, be sure to use the += assignment operator instead of the = assignment operator, or you’ll overwrite what was already being stored in the variable.

On an entry after the first one, use this:

$PSDefaultParameterValues += @{'Get*:Verbose'=$true}

Not this:

$PSDefaultParameterValues = @{'Get*:Verbose'=$true}

Notice that in the above examples we’ve used a wildcard character. If this is added to your $PSDefaultParameterValues, then all Get-* cmdlets and functions will include the Verbose parameter.