Powershell - json File - select only first value

Question

I've got this json file:

[
  {
      "group": [313, 312, 313, 311], 
      "group_name": ["example", "example", "example1"], 
      "status": ["not_available_time", "no_time"]
  }
]

And in Powershell I want the output to be: 313, example, not_available_time

So I always need just the first value.

I've tried this:

$responseJson = ConvertFrom-Json $response.Content

$group = $responseJson.group[0]
$name = $responseJson.group_name[0]
$status = $responseJson.status[0]

That works. But only if there is always more than one value. For example: if "group_name" in the JSON file would only hold the value "example" (and not ["example", "example", "example1"]) => the output would only be "e" instead of "example". It takes not the first value, but only the first letter if there is only one value.

How can I select the first value?

BR and thanks!

Answer 1

There are 2 safe methods to ensure you're always selecting the first Value, be it an array, a scalar or null:

• You can use the array subexpression operator @(), which will ensure that even if the value is $null or [System.Management.Automation.Internal.AutomationNull]::Value the result will always be an array (object[]):

@([System.Management.Automation.Internal.AutomationNull]::Value).GetType().Name # => Object[]
@($null).GetType().Name # => Object[] 

• As an alternative, Select-Object with the -First 1 argument, the difference is the returned object's Type remains the same:

(1 | Select-Object -First 1).GetType().Name        # => Int32
('a', 'b' | Select-Object -First 1).GetType().Name # => String
$null -eq ($null, $null | Select-Object -First 1)  # => True

---

Both alternatives are valid and depends on your use case which one fits your need better:

$json = @'
[
  {
      "group": [313, 312, 313, 311],
      "group_name": "single_element",
      "status": null
  }
]
'@ | ConvertFrom-Json

$json.PSObject.Properties | ForEach-Object {
    $arr = @($_.Value)[0]
    $slo = $_.Value | Select-Object -First 1

    [pscustomobject]@{
        'ArraySubExpression' = "[ {0}: $arr ]" -f $_.Name
        'Select-Object'      = "[ {0}: $slo ]" -f $_.Name
    }
}


ArraySubExpression             Select-Object
------------------             -------------
[ group: 313 ]                 [ group: 313 ]
[ group_name: single_element ] [ group_name: single_element ]
[ status:  ]                   [ status:  ]