PS Cmdlets

22.1.16

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

Invoke-RestMethod (Microsoft.PowerShell.Utility) - PowerShellMicrosoftLearn

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

Invoke-Expression (Microsoft.PowerShell.Utility) - PowerShellMicrosoftLearn

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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