Power Tips

In the previous example we looked at how numeric HTTP response codes can automatically be converted to descriptive text, simply by converting them to the type System.Net.HttpStatusCode.

 
PS> [System.Net.HttpStatusCode]500
InternalServerError
 

This works because System.Net.HttpStatusCode is a so-called “enumeration” and acts like a “lookup table”. You can easily dump all members of an enumeration, and for example…

In the previous example we created a small PowerShell function that checks web site availability, and as part of the test results, a HTTP response code was returned. Let’s check out how this numeric code can be easily converted into a meaningful text message.

Here is the function again that tests web sites:

function Test-Url
{
  param
  (
    [Parameter(Mandatory,ValueFromPipeline)]
    [string]
    $Url
  )
  …

When a web site is unavailable, often the question is whether it’s you, or whether the web site is generally down for everyone else, too. PowerShell can ask a web service to check web site availability for you. Here is a simple wrapper function:

function Test-Url
{
  param
  (
    [Parameter(Mandatory,ValueFromPipeline)]
    [string]
    $Url
  )
  
  Add-Type -AssemblyName System.Web
  
  $check = "https://isitdown…

Accessing RESTful web services is trivial for PowerShell: simply send your input data to a public web service, and receive the results.

Here are three PowerShell functions designed to each do a numeric conversion:

function Convert-InchToCentimeter
{
  param
  (
    [Parameter(Mandatory)]
    [Double]
    $Inch
  )
  [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
  $url = 'https://ucum…

PowerShell can validate AD username and passwords against the Active Directory:

Add-Type -AssemblyName System.DirectoryServices.AccountManagement
$account = New-Object System.DirectoryServices.AccountManagement.PrincipalContext([DirectoryServices.AccountManagement.ContextType]::Domain, $env:userdomain)

$account.ValidateCredentials('user12', 'topSecret')

Note that this approach is for diagnostic purposes…

If you’d like to add an incrementing number to your output, here is a simple way:

Get-Process |
  Select-Object -Property '#', ProcessName, CPU -First 10 |
  ForEach-Object -begin { $i = 0} -process {
    $i++
    $_.'#' = $i
    $_
  } -end {}

Select-Object adds a new property called “#”, and ForEach-Object adds an auto-incrementing number to it. The result looks similar to this:

If you ever write PowerShell functions that need to accept sensitive input such as passwords, make sure you allow users to submit SecureString input. If you accept passwords via clear text, there is a substantial risk that others may see the password while being entered, or (even worse) that the password is logged and later can be found in dump files.

Here is a simple framework that illustrates how you can achieve safe…

The most widely known PowerShell hosts are certainly powershell.exe and powershell_ise.exe because they ship out-of-the-box. However, there can be many more (and hidden) PowerShell hosts running. Any software that instantiates the PowerShell engine is a PowerShell host. This could be Visual Studio Code (with the PowerShell extension installed), Visual Studio, or any other similar software.

To find out all currently running…

Most modern computers have more than one processor, either physical or logical. If you’d like to find out the number of processors, here is a chunk of PowerShell code:

Get-WmiObject -Class Win32_Processor | 
  Select-Object -Property Caption, NumberOfLogicalProcessors

The result may look similar to this:

 
Caption                              NumberOfLogicalProcessors
-------                              -----…

In the previous tip we illustrated how you can dump all passwords from your personal Windows Password Vault. The same is true for basically any password manager as these programs are designed to return the passwords they store for you.

Google Chrome browsers store your personal passwords (and website history) in a SQLLite database. PowerShell can easily access this database and dump the information for you. To be able…

Windows has a protected password vault where it can store your secret passwords so you don’t have to always enter them manually in Internet Explorer or Edge.

If you get used to automated password managers, you may occasionally forget the original passwords. Here is a super simple PowerShell way to dump all of your passwords stored in the Windows password vault:

# important: this is required to load the assembly…

To download and install the Google Chrome browser, simply combine a couple of generic PowerShell commands:

$Installer = "$env:temp\chrome_installer.exe"
$url = 'http://dl.google.com/chrome/install/375.126/chrome_installer.exe'
Invoke-WebRequest -Uri $url -OutFile $Installer -UseBasicParsing
Start-Process -FilePath $Installer -Args '/silent /install' -Wait
Remove-Item -Path $Installer

ReTweet…

In the previous tip we used an old COM technique to display a pop-up box with a built-in timeout. That worked pretty well except that the dialog box can be covered under your PowerShell window at times.

With a little-known trick, you can make sure the dialog box will always open on top of all other windows:

$shell = New-Object -ComObject WScript.Shell
$value = $shell.Popup("You can't cover me!", 5, '…

Maybe you stumbled across code like this in the past:

$shell = New-Object -ComObject WScript.Shell
$value = $shell.Popup('Restart Computer?', 5, 'Important', 36)

"Choice: $value"

This chunk of code opens a dialog box and asks the user whether it is OK to restart the computer. The pop-up dialog has a built-in timeout so the code will never stall, even if running unattended.

However, since PowerShell…

The PowerShell pipeline tends to be slow when it is processing a lot of elements. This can take a lot of time:

$result = 1..15000 | 
    ForEach-Object {
        "Line $_"
    } 

A much faster approach replaces ForeEach-Object with an anonymous script block and is up to 200x faster:

$result = 1..15000 | 
    & { process {
        "Line $_"
    }}

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It may be useful for PowerShell to know whether a given key is currently pressed. This way, your profile script could, for example, do things during PowerShell startup based on keys you hold. For example, when you hold the left CTRL key while launching PowerShell, your profile script could preload certain modules or connect you to servers.

Here is how PowerShell detects pressed keys:

# this could be part of your profile…

Advanced PowerShell users often find themselves doing one of three things:

• They run a previous command and add Get-Member to learn more about the objects emitted
• They run a previous command and add Select-Object * to see all properties
• They run a previous command and pipe it to Out-GridView to keep the results in reach

All three can now be accomplished much more easily, and works in any PowerShell, including the console…

When you override Out-Default to do something meaningful, you really want to make sure the old behavior isn’t lost, and instead just something new is added. Here is an example that uses the concept of “Proxy Functions”.

The original input is forwarded (proxied) to the original Out-Default cmdlet. In addition, the function opens its own private Out-GridView window and echoes the output to this window…

Out-Default is a hidden PowerShell cmdlet that gets called at the end of each command, and outputs results to the console. You can override this function with your own. If you overwrite it with an empty function, for example, all output is discarded – or results in a “SECRET!” message:

function Out-Default
{
    'SECRET!'
}

This is how you remove custom overrides:

 
PS C:\> del function:Out…

Typically, Out-GridView opens a window and displays whatever you pipe into the cmdlet:

 
PS C:\> Get-Service | Out-GridView 
 

However, with a little trick Out-GridView becomes even more versatile. You can pipe information to the same output window whenever you want to.

First, get yourself an instance of Out-GridView that thinks it is running in a pipeline:

$pipeline = { Out-GridView }.GetSteppablePipeline()
$pipe…

At psconf.eu there was recently a challenge for the shortest code to check for how often a password was previously pwnd (hacked). Here is the result (credits to Daniel Rothgänger):

[Net.ServicePointManager]::SecurityProtocol='Tls12'
'P@ssw0rd'|sc p -N;$a,$b=(FileHash p -A SHA1|% h*)-split'(?<=^.{5})';((irm api.pwnedpasswords.com/range/$a)-split"$b`:(\d+)")[1]  

You can either…

Some geocoding APIs provide sophisticated sentiment analysis like in the example below:

"Most important museums of Amsterdam are located on the Museumplein, located at the southwestern side of the Rijksmuseum." |
  ForEach-Object -Begin {$url='https://geocode.xyz'
    $null = Invoke-RestMethod $url -S session
  } -Process {
    Invoke-RestMethod $url -W $session -Method Post -Body @{scantext=$_;geoi…

Geocoding can automatically extract geolocations from text. This example also shows a new way of submitting information to a server: in the example below, data is posted to the server using the same mechanism that is used in HTML forms. This is typically done to avoid having to URL-encode large amounts of data because when POST is used, the data travels in the header of the request, not the URL. This also allows more…

Today, we’d like to do the opposite and translate latitude and longitude into an address:

'52.37799,9.75195' |
  ForEach-Object -Begin {$url='https://geocode.xyz'
    $null = Invoke-RestMethod $url -S session
  } -Process {
    $coord = $_
    Invoke-RestMethod "$url/${address}?geoit=json" -W $session
  }

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Let’s start with translating addresses into latitude and longitude coordinates. We assume you read the previous parts to fully understand the code sample.

Here is some sample code that takes any number of addresses, and returns their latitude and longitude for you:

'One Microsoft Way, Redmond',
'Bahnhofstrasse 12, Hannover, Germany' |
  ForEach-Object -Begin {$url = 'https://geocode.xyz'