PowerShell Confirmation =======================

PowerShell provides a $PSCmdlet.ShouldProcess($target, $action) method (and some variants) that are enabled when a function enables SupportsShouldProcess. The behavior is affected by the $ConfirmPreference preference variable, the declared ConfirmImpact level of the function, and the -WhatIf and -Confirm parameters. A $PSCmdlet.ShouldContinue($target, $action) method is provided for greater control. See Everything you wanted to know about ShouldProcess.

 function Invoke-Action
 {
     [CmdletBinding(SupportsShouldProcess=$true,ConfirmImpact='Medium')] Param(
     [psobject] $Target
     )
     if($PSCmdlet.ShouldProcess("$Target", 'invoke action')) { <# perform action #> }
 }
 
 $ConfirmPreference = 'High'
 
 Invoke-Action
 # (ShouldProcess returns true)
 
 Invoke-Action -WhatIf
 # What if: Performing the operation "invoke action" on target "Target".
 # (ShouldProcess returns false)
 
 Invoke-Action -Confirm
 # Confirm
 # Are you sure you want to perform this action?
 # Performing the operation "show" on target "prompt".
 # [Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"):

ShouldProcess() return value ——————————

1. If -WhatIf is enabled, ShouldProcess() will write the intended action to the host and return false.
2. If -Confirm is enabled, ShouldProcess() will prompt.
3. If $ConfirmPreference or ConfirmImpact is None, ShouldProcess() will return true.
4. If the function ConfirmImpact is High, ShouldProcess() will always prompt.
5. If $ConfirmPreference is higher than ConfirmImpact, ShouldProcess() will return true.
6. ShouldProcess() will prompt otherwise.

level $ConfirmPreference → ConfirmImpact ↓	Low	Medium	High	None
None	True	True	True	True
Low	prompt	True	True	True
Medium	prompt	prompt	True	True
High	prompt	prompt	prompt	True