Kotesh Bandhamravuri

PowerShell - Referencing variable in current scope

koteshblog — Tue, 23 Feb 2010 15:53:00 GMT

PowerShell allows creating variables dynamically without declaring. During assignment, it also creates new variables in the inner scope (unlike programming languages, where there is only one instance of the variable).

The following examples will make it clear on scoping rule

Save the following script into a file ScopeTest1.ps1

$myvar = "Hello World"
function PrintHelloWorld 
{ 
  $myvar = "Hello Universe"
  Write-Host "$myvar"
} 
Write-Host "$myvar" 
PrintHelloWorld 
Write-Host "$myvar"

PS C:\PowerShellExamples> .\ScopeTest1.ps1
Hello World
Hello Universe
Hello World

Now save the following script into a file ScopeTest2.ps1

$myvar = "Hello World"
function PrintHelloWorld 
{ 
  ([ref]$myvar).Value = "Hello Universe"    Write-Host "$myvar" 
} 
Write-Host "$myvar" 
PrintHelloWorld 
Write-Host "$myvar"

PS C:\PowerShellExamples> .\ScopeTest2.ps1
Hello World
Hello Universe
Hello Universe

In ScopeTest2.ps1, a new $myvar is not created in function scope. Existing variable is referenced and updated

PowerShell - How to read a file

koteshblog — Fri, 12 Feb 2010 22:06:00 GMT

$contents = Get-Content C:\context.txt

PowerShell - How to create a PSCredential object

koteshblog — Fri, 12 Feb 2010 21:50:00 GMT

Several PowerShell commandlets take a PSCredential object to run using a particular user account. You can create the PSCredential object by using Get-Credential commandlet which opens a dialog to enter the username and password. This way of entering credentials can be used in an interactive mode.

$mycredentials = Get-Credential

When you have to provide credentials in non-interactive mode, you can create a PSCredential object in the following way.

$secpasswd = ConvertTo-SecureString "PlainTextPassword" -AsPlainText -Force
$mycreds = New-Object System.Management.Automation.PSCredential ("username", $secpasswd)

You can now pass $mycreds to any -PSCredential input parameter

* You may not want to reveal PlainTextPassword for your personal accounts as a general precaution. Use a common user account and password that everyone knows for your non-interactive PSCredential usage.

* Tested with PowerShell 2.0

PowerShell - How to find details of Operating System

koteshblog — Fri, 12 Feb 2010 21:21:00 GMT

There were several instances where I had to find details of the operating system using PowerShell. Here, I am providing several PowerShell snippets that return various details of the Operating System.

Name of the Operating System

PS C:\> (Get-WmiObject Win32_OperatingSystem).Name

Is Operating System 32-bit or 64-bit

PS C:\> (Get-WmiObject Win32_OperatingSystem).OSArchitecture

Name of the Machine

PS C:\> (Get-WmiObject Win32_OperatingSystem).CSName

There are many more properties of the Operating System that are exposed. To obtain more details, run the following

PS C:\> Get-WmiObject Win32_OperatingSystem | Get-Member

* Tested using PowerShell 2.0

First things first

koteshblog — Fri, 12 Feb 2010 21:07:00 GMT

The first programs that I wrote was

BK Logo

10 PRINT "HELLO WORLD" (BASIC)

main () { printf ("Hello World" } (C)

main () { cout << "Hello World"; } (C++)

main () { Console.WriteLine("Hello World" } (C#)

"Hello World" (PowerShell)