In the PowerShell programming language, a script block is a collection of statements or expressions that can be used as a single unit. A script block can accept arguments and return values.

Syntax

 {<statement list>}
 
 #or
 
 {
 Param([type]$Parameter1 [,[type]$Parameter2])
 <statement list>
 }

A script block is an instance of a Microsoft .NET Framework type System.Management.Automation.ScriptBlock. Commands can have script block parameter values. For example, the Invoke-Command cmdlet has a ScriptBlock parameter that takes a script block value,

Invoke-Command -ScriptBlock { Get-Process }

Handles  NPM(K)    PM(K)     WS(K) VM(M)   CPU(s)     Id ProcessName
-------  ------    -----     ----- -----   ------     -- -----------
999          28    39100     45020   262    15.88   1844 communicator
721          28    32696     36536   222    20.84   4028 explorer
...

Invoke-Command can also execute script blocks that have parameter blocks. Parameters are assigned by position using the ArgumentList parameter.

Invoke-Command -ScriptBlock { param($p1, $p2)
"p1: $p1"
"p2: $p2"
} -ArgumentList "First", "Second"

p1: First
p2: Second

You can use variables to store and execute script blocks.

$a = { Get-Service BITS }
Invoke-Command -ScriptBlock $a

Status   Name        DisplayName
------   ----        -----------
Running  BITS        Background Intelligent Transfer Ser...

Like Invoke-Command, the call operator executes the script block in a child scope. The call operator can make it easier for you to use parameters with your script blocks.

$a ={ param($p1, $p2)
"p1: $p1"
"p2: $p2"
}

&$a -p2 "First" -p1 "Second"

You can store the output from your script blocks in a variable using assignment.

PS>  $a = { 1 + 1}
PS>  $b = &$a
PS>  $b
2

PS>  $a = { 1 + 1}
PS>  $b = Invoke-Command $a
PS>  $b
2

Install exe on Remote Server

Invoke-Command -ComputerName server01 -ScriptBlock { 
    Start-Process c:\windows\temp\installer.exe -ArgumentList '/silent' -Wait
}

Change File Extension

#Rename File Extension
param($Folder)

Write-Host "Before Renaming files...`n`n"
Get-ChildItem $Folder

Get-ChildItem "$Folder\*.txt" | 
Rename-Item -NewName { $_.name -Replace '.txt','.bak' }

Write-Host "`n`nAfter Renaming files...`n`n"
Get-ChildItem $Folder