Prompt for user input in PowerShell

Question

I want to prompt the user for a series of inputs, including a password and a filename.

I have an example of using host.ui.prompt, which seems sensible, but I can't understand the return.

Is there a better way to get user input in PowerShell?

Answer 1

Place this at the top of your script. It will cause the script to prompt the user for a password. The resulting password can then be used elsewhere in your script via $pw.

   Param(
     [Parameter(Mandatory=$true, Position=0, HelpMessage="Password?")]
     [SecureString]$password
   )

   $pw = [Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR($password))

If you want to debug and see the value of the password you just read, use:

   write-host $pw

Answer 2

As an alternative, you could add it as a script parameter for input as part of script execution

 param(
      [Parameter(Mandatory = $True,valueFromPipeline=$true)][String] $value1,
      [Parameter(Mandatory = $True,valueFromPipeline=$true)][String] $value2
      )

Answer 3

Using parameter binding is definitely the way to go here. Not only is it very quick to write (just add [Parameter(Mandatory=$true)] above your mandatory parameters), but it's also the only option that you won't hate yourself for later.

More below:

[Console]::ReadLine is explicitly forbidden by the FxCop rules for PowerShell. Why? Because it only works in PowerShell.exe, not PowerShell ISE, PowerGUI, etc.

Read-Host is, quite simply, bad form. Read-Host uncontrollably stops the script to prompt the user, which means that you can never have another script that includes the script that uses Read-Host.

You're trying to ask for parameters.

You should use the [Parameter(Mandatory=$true)] attribute, and correct typing, to ask for the parameters.

If you use this on a [SecureString], it will prompt for a password field. If you use this on a Credential type, ([Management.Automation.PSCredential]), the credentials dialog will pop up, if the parameter isn't there. A string will just become a plain old text box. If you add a HelpMessage to the parameter attribute (that is, [Parameter(Mandatory = $true, HelpMessage = 'New User Credentials')]) then it will become help text for the prompt.

Answer 4

Read-Host is a simple option for getting string input from a user.

$name = Read-Host 'What is your username?'

To hide passwords you can use:

$pass = Read-Host 'What is your password?' -AsSecureString

To convert the password to plain text:

[Runtime.InteropServices.Marshal]::PtrToStringAuto(
    [Runtime.InteropServices.Marshal]::SecureStringToBSTR($pass))

As for the type returned by $host.UI.Prompt(), if you run the code at the link posted in @Christian's comment, you can find out the return type by piping it to Get-Member (for example, $results | gm). The result is a Dictionary where the key is the name of a FieldDescription object used in the prompt. To access the result for the first prompt in the linked example you would type: $results['String Field'].

To access information without invoking a method, leave the parentheses off:

PS> $Host.UI.Prompt

MemberType          : Method
OverloadDefinitions : {System.Collections.Generic.Dictionary[string,psobject] Pr
                    ompt(string caption, string message, System.Collections.Ob
                    jectModel.Collection[System.Management.Automation.Host.Fie
                    ldDescription] descriptions)}
TypeNameOfValue     : System.Management.Automation.PSMethod
Value               : System.Collections.Generic.Dictionary[string,psobject] Pro
                    mpt(string caption, string message, System.Collections.Obj
                    ectModel.Collection[System.Management.Automation.Host.Fiel
                    dDescription] descriptions)
Name                : Prompt
IsInstance          : True

$Host.UI.Prompt.OverloadDefinitions will give you the definition(s) of the method. Each definition displays as <Return Type> <Method Name>(<Parameters>).