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