Using non-string as $env: variable

Question

I'd like to store a hashtable in an environmental variable--is that possible in Powershell?

Here's how I'm testing this:

$env:test = @{}
$env:test
$env:test|gm

And getting confused, because output is:

System.Collections.Hashtable

TypeName: System.String

Name MemberType Definition

---- ---------- ---------- Clone Method System.Object Clone()
CompareTo Method int CompareTo(System.Object value), int CompareTo(string strB) ...

... So when I return $env:test directly, I get 'Hashtable', but when I pipe it to get-member, system.string is returned. Can someone please explain this behaviour?

Cadwell

Why do you require doing this in an env variable? – Leipzig

Also, env variables are always strings. Period. – Leipzig

I have a hash of {[int]$id,[System.Management.Automation.PSCredential]$cred} which I want to be able to access from anywhere in the script. env vars being always strings makes sense, but why the odd behavior described in original question? – Cadwell

A variable with global or script scope would be accessible from anywhere in the script. At a prompt type: Get-Help about_scopes – Leipzig

No particular reason to need env var. I have a few vars I store in a custom env space (e.g.: $env:MYSPACE:foo) and was wondering if I can store objects or references in that space as well. – Cadwell

Answer 1

Environment variables ($env:stringVariable) are strings. However, it appears you want to make a non-string variable of type hashtable global. That can be done by using the global modifier ($global:hashtableVariable). This will allow you to access the variable from one script file in another as demostrated here

PowerShellScriptFile-1.ps1

$global:hashtableVariable = @{
   'key1' = 'value1'
   'key2' = 'value2'
}

PowerShellScriptFile-2.ps1

$global:hashTableVariable.GetEnumerator() | ForEach-Object {
       Write-Host "$($_.Key):$($_.Value)"
}

Aniakudo

Answer 2

Got it. "System.Collections.Hashtable" is the string value assigned to $env:test

Cadwell

Yes. Since an env variable can only ever be a string, when you assigned a hash to it, Pwershell attempted to coerce the hash into being a string. To do this, Powershell calls the .ToString() method on the hashtable object which returns System.Collections.Hashtable. This is thus stored in the env variable. – Leipzig

Answer 3

More than a bit late to the party, but now you can do this, though since environment variables are strictly strings, you'll need to assign it to something else in your code, and you will need to use the Microsoft.PowerShell.Utility module.

import-module Microsoft.PowerShell.Utility 
$hash = ConvertFrom-StringData -StringData $env:myvar

you will need to appropriately format your environment variable eg:

$env:myvar = "Fname = John ``n Lname= Smith ``n DOB = 01/01/1980"

Use only one backtick, I can't figure out how to get only one to display right.

see https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/convertfrom-stringdata?view=powershell-7

Kassala