How to Use -confirm in PowerShell

-Confirm is a switch in most PowerShell cmdlets that forces the cmdlet to ask for user confirmation. What you're actually looking for is the Read-Host cmdlet:

$confirmation = Read-Host "Are you Sure You Want To Proceed:"
if ($confirmation -eq 'y') {
    # proceed
}

or the PromptForChoice() method of the host user interface:

$title    = 'something'
$question = 'Are you sure you want to proceed?'

$choices = New-Object Collections.ObjectModel.Collection[Management.Automation.Host.ChoiceDescription]
$choices.Add((New-Object Management.Automation.Host.ChoiceDescription -ArgumentList '&Yes'))
$choices.Add((New-Object Management.Automation.Host.ChoiceDescription -ArgumentList '&No'))

$decision = $Host.UI.PromptForChoice($title, $question, $choices, 1)
if ($decision -eq 0) {
    Write-Host 'confirmed'
} else {
    Write-Host 'cancelled'
}

Edit:

As M-pixel pointed out in the comments the code could be simplified further, because the choices can be passed as a simple string array.

$title    = 'something'
$question = 'Are you sure you want to proceed?'
$choices  = '&Yes', '&No'

$decision = $Host.UI.PromptForChoice($title, $question, $choices, 1)
if ($decision -eq 0) {
    Write-Host 'confirmed'
} else {
    Write-Host 'cancelled'
}

This is a simple loop that keeps prompting unless the user selects 'y' or 'n'

$confirmation = Read-Host "Ready? [y/n]"
while($confirmation -ne "y")
{
    if ($confirmation -eq 'n') {exit}
    $confirmation = Read-Host "Ready? [y/n]"
}

Read-Host is one example of a cmdlet that -Confirm does not have an effect on.-Confirm is one of PowerShell's Common Parameters specifically a Risk-Mitigation Parameter which is used when a cmdlet is about to make a change to the system that is outside of the Windows PowerShell environment. Many but not all cmdlets support the -Confirm risk mitigation parameter.

As an alternative the following would be an example of using the Read-Host cmdlet and a regular expression test to get confirmation from a user:

$reply = Read-Host -Prompt "Continue?[y/n]"
if ( $reply -eq 'y' ) { 
    # Highway to the danger zone 
}

The Remove-Variable cmdlet is one example that illustrates the usage of the -confirm switch.

Remove-Variable 'reply' -Confirm

Additional References: CommonParameters, Write-Host, Read-Host, Comparison Operators, Regular Expressions, Remove-Variable

Here is the documentation from Microsoft on how to request confirmations in a cmdlet. The examples are in C#, but you can do everything shown in PowerShell as well.

First add the CmdletBinding attribute to your function and set SupportsShouldProcess to true. Then you can reference the ShouldProcess and ShouldContinue methods of the $PSCmdlet variable.

Here is an example:

function Start-Work {
    <#
    .SYNOPSIS Does some work
    .PARAMETER Force
        Perform the operation without prompting for confirmation
    #>
    [CmdletBinding(SupportsShouldProcess=$true)]
    param(
        # This switch allows the user to override the prompt for confirmation
        [switch]$Force
    )
    begin { }
    process {
        if ($PSCmdlet.ShouldProcess('Target')) {
            if (-not ($Force -or $PSCmdlet.ShouldContinue('Do you want to continue?', 'Caption'))) {
                return # user replied no
            }

            # Do work
        }

    }
    end { }
}

write-host does not have a -confirm parameter.

You can do it something like this instead:

    $caption = "Please Confirm"    
    $message = "Are you Sure You Want To Proceed:"
    [int]$defaultChoice = 0
    $yes = New-Object System.Management.Automation.Host.ChoiceDescription "&Yes", "Do the job."
    $no = New-Object System.Management.Automation.Host.ChoiceDescription "&No", "Do not do the job."
    $options = [System.Management.Automation.Host.ChoiceDescription[]]($yes, $no)
    $choiceRTN = $host.ui.PromptForChoice($caption,$message, $options,$defaultChoice)

if ( $choiceRTN -ne 1 )
{
   "Your Choice was Yes"
}
else
{
   "Your Choice was NO"
}

Write-Warning "This is only a test warning." -WarningAction Inquire

from: https://serverfault.com/a/1015583/584478

For when you want a 1-liner

while( -not ( ($choice= (Read-Host "May I continue?")) -match "^(y|n)$")){ "Y or N ?"}

Here's a solution I've used, similiar to Ansgar Wiechers' solution;

$title = "Lorem"
$message = "Ipsum"

$yes = New-Object System.Management.Automation.Host.ChoiceDescription "&Yes", "This means Yes"
$no = New-Object System.Management.Automation.Host.ChoiceDescription "&No", "This means No"

$options = [System.Management.Automation.Host.ChoiceDescription[]]($yes, $no)

$result = $host.ui.PromptForChoice($title, $message, $Options, 0)

Switch ($result)
     {
          0 { "You just said Yes" }
          1 { "You just said No" }
     }

A slightly prettier function based on Ansgar Wiechers's answer. Whether it's actually more useful is a matter of debate.

function Read-Choice(
   [Parameter(Mandatory)][string]$Message,
   [Parameter(Mandatory)][string[]]$Choices,
   [Parameter(Mandatory)][string]$DefaultChoice,
   [Parameter()][string]$Question='Are you sure you want to proceed?'
) {
    $defaultIndex = $Choices.IndexOf($DefaultChoice)
    if ($defaultIndex -lt 0) {
        throw "$DefaultChoice not found in choices"
    }

    $choiceObj = New-Object Collections.ObjectModel.Collection[Management.Automation.Host.ChoiceDescription]

    foreach($c in $Choices) {
        $choiceObj.Add((New-Object Management.Automation.Host.ChoiceDescription -ArgumentList $c))
    }

    $decision = $Host.UI.PromptForChoice($Message, $Question, $choiceObj, $defaultIndex)
    return $Choices[$decision]
}

Example usage:

PS> $r = Read-Choice 'DANGER!!!!!!' '&apple','&blah','&car' '&blah'

DANGER!!!!!!
Are you sure you want to proceed?
[A] apple  [B] blah  [C] car  [?] Help (default is "B"): c
PS> switch($r) { '&car' { Write-host 'caaaaars!!!!' } '&blah' { Write-Host "It's a blah day" } '&apple' { Write-Host "I'd like to eat some apples!" } }
caaaaars!!!!

This version asks if the user wants to perform an action before continuing with the rest of the script.

DO
{
    $confirmation = Read-Host "Do want Action before continue? [Y/N]"
    if ($confirmation -eq 'y') {
       write-Host "Doing the Action"
    }
} While (($confirmation -ne 'y') -and ($confirmation -ne 'n'))

I prefer a popup.

$shell = new-object -comobject "WScript.Shell"
$choice = $shell.popup("Insert question here",0,"Popup window title",4+32)

If $choice equals 6, the answer was Yes If $choice equals 7, the answer was No

I think this is what you are looking for.

To have a function or script behave as a cmdlet in this regard, you should use ConfirmImpact='High' in the CmdletBinding as well.

Then PowerShell will automatically prompt the user.

To improve on the answer somewhat above from Zack, use...

function Start-Work {
  [CmdletBinding(SupportsShouldProcess, ConfirmImpact='High')]
  param(
  )

  if (-not $PSCmdlet.ShouldProcess('')) {
     return
  }

  Write-Host 'Process did run'

}

Start-Work -Confirm:$false will still run the function without confirmation.

The prompting will depend on the preference variable $ConfirmPreference, that defaults to 'High'.
(See about_Preference_Variables)