Loading a PowerShell hashtable from a file? - powershell

Question

I've got a file containing some data in PowerShell Object Notation:
#{ X = 'x'; Y = 'y' }
I'd like to load this into a variable from the file.

Answer 1

(I figured it out while putting together a repro)
PS> $content = ( Get-Content .\foo.pson | Out-String )
PS> $data = ( Invoke-Expression $content )
Get-Content returns an array with the lines in the file; the Out-String is used to join them together.
Invoke-Expression then runs the script, and the result is captured. This is open to injection attacks, but that's OK in my specific case.
Or, if you prefer your PowerShell terse:
PS> $data = gc .\foo.pson | Out-String | iex
(I can't find a shorter form of Out-String)

Answer 2

I've used ConvertFrom-StringData. If you want to use this approach you'll need to change the way you store key/value pairs with each on its own line and no quotes:
#Contents of test.txt
X = x
Y = y
get-content .\test.txt | ConvertFrom-StringData
Name Value
---- -----
X x
Y y
ConvertFrom-StringData is a built-in cmdlet. I created corresponding ConvertTo-StringData function available here http://poshcode.org/1986

Answer 3

I ran into trouble using ConvertFrom-StringData as #Chad suggested. If you do:
$hash = get-content .\test.txt | ConvertFrom-StringData
I found I had an object array rather than a hash table. In fact, it appears that I had an array of hash tables, each with one entry. I confirmed with a:
$hash.GetType()
It looks like you need to join each line of the slurped input file to ensure that it forms a single string for ConvertFrom..'s use:
$hash = ((get-content .\test.txt) -join '`n') | ConvertFrom-StringData

Answer 4

If you can give this file the extension .ps1, say, data.ps1 then it cannot be simpler than this code:
$data = <path>\data.ps1

Answer 5

Starting from PowerShell 5.0 you have
Import-PowerShellDataFile
Which imports values from a .psd1-file. So the only thing you have to do is rename your file to *.psd1
Official help is here.

Answer 6

This is an older post but, this is sort of a twist on your accepted solution and perhaps slightly more "safe", keep in mind un-trusted files.
From your notes, you have a file that contains a hashtable using Powershell syntax. Given that constraint, you can import it directly:
$HashPath = ".\foo.pson"
# input file contents
$filecontent = Get-Content -Path $HashPath -Raw -ErrorAction Stop
# put the file in a script block
$scriptBlock = [scriptblock]::Create( $filecontent )
#check that the file contains no other Powershell commands
$scriptBlock.CheckRestrictedLanguage( $allowedCommands, $allowedVariables, $true )
#execute it to create the hashtable
$hashtable = ( & $scriptBlock )
Note on the $scriptBlock.CheckRestrictedLanguage you could replace that with
$scriptBlock.CheckRestrictedLanguage([string[]]#(), [string[]]#(), $false)
Use an empty list of strings so we do not allow any Powershell commands. When importing a hashtable, this is exactly what we want. That last one is allowEnvironmentVariables so we restrict that in this example with $false.
Side note, a Powershell module (psd1 file) is just a hashtable so this concept may help you to also pull in script blocks or other things.
Reference: https://learn.microsoft.com/en-us/dotnet/api/system.management.automation.scriptblock.checkrestrictedlanguage?view=powershellsdk-1.1.0