The two PowerShell Cmdlets that are used are Invoke-RestMethodand Invoke-Expression. It is also important that these cmdlets are processed in this order, which I will touch on at the bottom of this page
Invoke-RestMethod
This cmdlet is used to return the contents of a provided URL in a structured, typically Raw format
Here are some examples of how to use Invoke-RestMethod to get the raw content from a Url
PS C:\> Invoke-RestMethod -Uri https://raw.githubusercontent.com/OSDeploy/PSCloudScript/main/ps-cmdlets.txt
This is a test to see if this raw content can be saved as a PowerShell string
PS C:\> irm https://raw.githubusercontent.com/OSDeploy/PSCloudScript/main/ps-cmdlets.txt
This is a test to see if this raw content can be saved as a PowerShell string
PS C:\> $String = irm raw.githubusercontent.com/OSDeploy/PSCloudScript/main/ps-cmdlets.txt
PS C:\> $String
This is a test to see if this raw content can be saved as a PowerShell string
Invoke-Expression
This cmdlet is used to execute a PowerShell Command. You can read Microsoft's documentation here
If you read the Microsoft Doc, you'll understand that iex commands can come from a String. This can be easily demonstrated in this example
PS D:\> $String = @'
Write-Host 'This is PowerShell String'
'@
PS D:\> Invoke-Expression -Command $String
This is PowerShell String
PS D:\> Invoke-Expression $String
This is PowerShell String
PS D:\> iex $String
This is PowerShell String
This method even works if there is a PowerShell function in the String. Keep in mind this function is only available in the current PowerShell session
PS D:\> $StringFunction = @'
function Test-PowerShell
{
[CmdletBinding()]
param()
Write-Host 'This is a PowerShell Function'
Write-Verbose 'And this is a Verbose PowerShell Function'
}
'@
PS D:\> Invoke-Expression -Command $StringFunction
PS D:\> Test-PowerShell
This is a PowerShell Function
PS D:\> Test-PowerShell -Verbose
This is a PowerShell Function
VERBOSE: And this is a Verbose PowerShell Function
Order
These commands have to follow a specific order. You need the content from Invoke-RestMethod before you can execute in Invoke-Expression
#Command in parenthesis is processed first in both of these examples
Invoke-Expression -Command (Invoke-RestMethod -Uri $Uri)
#Alternate using Alias
iex(irm $Uri)
#Pipeline can be used
Invoke-RestMethod -Uri $Uri | Invoke-Expression
#Alternate using Alias
irm $Uri | iex
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