How to check if the user hits enter with no input in a powershell script?

Question

I have a powershell script where I want the user to input a value and the script returns a randomized string for a password. If they just hit enter when prompted for the length of the password, I want it to be a default of 9 characters.

How do I handle no input?

I tried something like this, but don't think it is quite right:

Write-Host Enter the password length requirement:

$length = Read-Host
IF ( $length -eq $NULL) 
    { Do continue on with the value of 9 for the length}
ELSE
    {Use $length for the rest of the script}

The else portion works just fine; however when generating passwords I keep finding myself typing 9 over and over again. I'd rather just hit enter.

Any help is greatly appreciated!

stej · Accepted Answer · 2011-03-29 20:01:25Z

19

PowerShell is great, because you can shorten code very often and it works :)

if (!$length) { 
  Do continue on with the value of 9 for the length
} ...

Why?

[bool]$null         # False
[bool]''            # False
[bool]'something'   # True

answered Mar 29, 2011 at 20:01

stej

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3 Comments

JasonMArcher Over a year ago

In the if block, set $Length to 9 and then you are good to go.

stej Over a year ago

@jason I wanted to show only the condition, I guess John is capable to do the rest :) Anyway, thx for reviewing.

JasonMArcher Over a year ago

John may not have realized that, I like to be explicit some times. :)

JPBlanc · Accepted Answer · 2011-03-29 19:45:57Z

5

I would say "works as designed". Because $lenght is not NULL. the right test is :

if ($length -eq [string]::empty)

So perhaps a conjunction of the two tests.

JP

answered Mar 29, 2011 at 19:45

JPBlanc

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Comments

Naraen · Accepted Answer · 2011-03-29 19:45:57Z

2

IF ( $length -eq "")

instead of IF ( $length -eq $NULL)

should do it.

answered Mar 29, 2011 at 19:45

Naraen

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Comments

Start-Automating · Accepted Answer · 2011-03-29 19:41:47Z

1

The absolute best way to do this would be to it a parameter to the script and use the V2 validation attributes. This will also prevent them putting in bad data, like strings

param( [Parameter(Mandatory=$true)] [ValidateRange(1,9)] [Int] $Length )

This will give you better validation and consistent and localized errors.

Hope this helps

answered Mar 29, 2011 at 19:41

Start-Automating

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