How can I sort an array so that the output is always an array, even when the input array is empty?

Question

I have a variable $try that contains an array, and I want $res to contain the sorted version of $try. This seems easy enough, but I can't get this to work when $try happens to contain an empty array.

When $try contains a non-empty array, no problem:

PS C:\data> $try = @("a", "c", "b")

PS C:\data> $res = $try | Sort-Object

PS C:\data> $res
a
b
c

PS C:\data> $res.GetType()

IsPublic IsSerial Name                                     BaseType                                                                                                                                                                                                                                                 
-------- -------- ----                                     --------                                                                                                                                                                                                                                                 
True     True     Object[]                                 System.Array

However, when the input array is empty, the output object is $null, not (as I would have expected) an empty array:

PS C:\data> $try = @()

PS C:\data> $res = $try | Sort-Object

PS C:\data> $res

PS C:\data> $null -eq $res
True

PS C:\data> $null -eq $try
False

I want $res to be the sorted version of $try, even if $try happens to contain an empty array. In that case, I want $res to also be an empty array.

Is there a way of doing this other than something like:

PS C:\data> $try = @()

PS C:\data> if ($try) {$res = $try | Sort-Object} else { $res = @() }

PS C:\data> $null -eq $try
False

PS C:\data> $null -eq $res
False

Theo · Accepted Answer · 2020-11-30 20:55:15Z

3

You can force $res to be an array like this, even when $try is $null or an empty array:

$try = $null  # or an empty array @()
$res = @($try | Sort-Object)

# $res is now an array with 0 elements
$res.GetType()

Result

IsPublic IsSerial Name      BaseType                                                                                   
-------- -------- ----      --------                                                                                   
True     True     Object[]  System.Array

answered Nov 30, 2020 at 20:55

Theo

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1 Comment

Jurjen Over a year ago

I think I'm still missing some basic PowerShell knowledge, because my initial reading of @($try | Sort-Object) leads me to think that this would result in an array that has a single member, namely the sorted array. But since your suggestion works, the result of $try | Sort-Object must not be an array itself, so I have some PowerShell learning to do it seems. :) (But it does surprise me a bit that a gazillion "How to sort an array in PowerShell" blog posts don't mention this, and just pipe the unsorted array to Sort-Object).

Esperento57 · Accepted Answer · 2020-12-01 03:07:02Z

1

You can initialise your res variable and append to res your result sort :

$try = @()
$res=@()
$res += $try | Sort-Object

answered Dec 1, 2020 at 3:07

Esperento57

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