Extract Values From Raw JSON Using Powershell

Question

I have created a PowerShell script to return values from a web URL featuring JSON data.

My script is now returning HTML with some JSON data included.

Now, I want to retrieve a value from the JSON data contained within this HTML.

Specifically, the value for 'ID.ad_user' where the data variable is declared ("var data = ").

So, "345345-3453-gfdd-44334" is the value I need (exlcuing the "ad_user://" text).

Here's my PowerShell code:

$cred = "[my unique token]"
$headers = @{ Authorization = "Bearer $cred" }

$Output = Invoke-RestMethod `
  -Method Get `
  -Headers $headers `
  -ContentType: "application/json; charset=utf-8" `
  -Uri "[my URL]" 
$Output

Here's the HTML & JSON output:

<!DOCTYPE html>
<!-- If you are reading this, there is a good chance you would prefer sending an
"Accept: application/json" header and receiving actual JSON responses. -->
<link rel="stylesheet" type="text/css" href="/ui.min.css" />
<script src="/ui.min.js"></script>
<script>
var user = "admin";
var curlUser='[HIDDEN]';
var data = {"name": "Pat McKinnon","ID": ["ad_user://345345-3453-gfdd-44334","local://p-345dd455"],"state": "active",}
</script>

@Mathias R. Jessen - right you are. I should have said HTML output featuring JSON data contained within. Let me update that. — Kerbol
– Kerbol, Commented Nov 17, 2021 at 12:28
Have you seen the comment in the actual HTML? If you are reading this, there is a good chance you would prefer sending an "Accept: application/json" header and receiving actual JSON responses. So why not do that, receive not an HTML with embedded JSON, but just the JSON response you can use ConvertFrom-Json on. — Theo
– Theo, Commented Nov 17, 2021 at 12:57
thanks Theo. How would I implement ConvertFrom-Json my code? Can you share an example? — Kerbol
– Kerbol, Commented Nov 17, 2021 at 13:13
Probably by adding that to the headers Hashtable: $headers = @{ Authorization = "Bearer $cred"; Accept = "application/json" }. Then look at what $Output shows after Invoke-RestMethod. If this is indeed JSON, you can simply do $Output | ConvertFrom-Json and work your way from there — Theo
– Theo, Commented Nov 17, 2021 at 16:15

Stringfellow · Accepted Answer · 2021-11-17 13:03:01Z

1

Maybe this would work. Search for the part of the string containing the JSON data and then convert to an object.

$result = $Output | Select-String -Pattern "var data = {.+}`n"
$lineWithData = $result.Matches.Value
$lineWithData
$json = $lineWithData.Substring('var data = '.Length)
$json
$dataObject = $json | ConvertFrom-Json
$dataObject

Then you can get the ID property from the object.

$dataObject.ID
ad_user://345345-3453-gfdd-44334
local://p-345dd455```

answered Nov 17, 2021 at 13:03

Stringfellow

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2 Comments

Kerbol Over a year ago

I get the following error when I run that: ''' You cannot call a method on a null-valued expression. At line:12 char:1 + $json = $lineWithData.Substring('var data = '.Length) '''

Stringfellow Over a year ago

Sounds like the $Output variable does not contain a string with the expected pattern, resulting in zero matches and therefore the variable $lineWithData is null.

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