PSDefaultParameterValues and PSBoundParameters

Two very little-known or little-used built-in variables are the PSDefaultParameterValues and PSBoundParameters dictionaries. Both serve a distinct purpose in scripting, and will make your life easier.

PSDefaultParameterValues

Let's examine the first dictionary, PSDefaultParameterValues, in the following code sample:

# The automatic variable is great to set defaults
$labFolder = mkdir .\StagingDirectory -Force
$PSDefaultParameterValues = @{
    '*:Path' = $labFolder.FullName # Extremely generic. Set all Path parameters for all Cmdlets
    'New-Item:ItemType' = 'File'
}

# Notice how all cmdlets use Path
# New-Item uses ItemType File now
New-Item ...