# Combining Empty Arrays
**URL:** https://forums.powershell.org/t/combining-empty-arrays/9754
**Category:** PowerShell Help
**Created:** [November 22, 2017, 10:26am UTC](https://forums.powershell.org/t/combining-empty-arrays/9754 "2017-11-22T10:26:30Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@stackexchangeuser4](https://forums.powershell.org/u/stackexchangeuser4)
#### Post date: [November 22, 2017, 10:26am UTC](https://forums.powershell.org/t/combining-empty-arrays/9754/1 "2017-11-22T10:26:30Z")
I’ve been pulling my hair out at this one for the last few hours, seems to be down to an obscure quirk.
(EDITED)
Import this function:
```
Function Test-Filter
{
[cmdletbinding()]
Param
(
[Parameter(Mandatory = $true,
ValueFromPipeline,
Position = 0)]
$Items
)
Process
{
$Items | Foreach-Object {
if ($_ -eq "A")
{
$output += $_
}
}
}
End
{
if ($output.Count -gt 0)
{ Write-Output (,$output) }
}
}
```
Now run this:
```
[Array]$arr1 = "A", "B", "C", "D" | Test-Filter | Sort
[Array]$arr2 = "E", "F", "G", "H" | Test-Filter | Sort | Select -First 1
[Array]$arr3 = 1, 2 | Test-Filter
[Array]$arr4 = "Jolly Cooperation" | Test-Filter
[Array]$combined = $arr1 + $arr2 + $arr3 + $arr4
$combined.count
```
Count is 1, as expected, $arr1 contains “A” and the rest are empty. Now run this:
```
Invoke-Command {
[Array]$arr1 = "A", "B", "C", "D" | Test-Filter | Sort
[Array]$arr2 = "E", "F", "G", "H" | Test-Filter | Sort | Select -First 1
[Array]$arr3 = 1, 2 | Test-Filter
[Array]$arr4 = "Jolly Cooperation" | Test-Filter
[Array]$combined = $arr1 + $arr2 + $arr3 + $arr4
$combined.count
}
```
Count is now 4.
This is part of a process to list patch files awaiting installation, there are four types of files but not all may be present in each patch type. Invoke-Command is required to format and log the output of the (lengthy) script but it seems to be messing with arrays somehow?
---
### Author:  [@sam-boutros](https://forums.powershell.org/u/sam-boutros)
#### Post date: [November 22, 2017, 10:32am UTC](https://forums.powershell.org/t/combining-empty-arrays/9754/2 "2017-11-22T10:32:13Z")
Answer is 4 not 1 in PS 5:
```
PS D:\Sandbox> [Array]$arr1 = "A"
[Array]$arr2 = $null
[Array]$arr3 = $null
[Array]$arr4 = $null
[Array]$combined = $arr1 + $arr2 + $arr3 + $arr4
$combined.Count
4
PS D:\Sandbox> $PSVersionTable
Name Value
---- -----
PSVersion 5.1.15063.726
PSEdition Desktop
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0...}
BuildVersion 10.0.15063.726
CLRVersion 4.0.30319.42000
WSManStackVersion 3.0
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
```
To lose the null arrays replace the line
```
[Array]$combined = $arr1 + $arr2 + $arr3 + $arr4
```
with something like
```
[Array]$combined = @($arr1,$arr2,$arr3,$arr4) | % { if ($_) {$_} }
```
---
### Author:  [@stackexchangeuser4](https://forums.powershell.org/u/stackexchangeuser4)
#### Post date: [November 22, 2017, 10:37am UTC](https://forums.powershell.org/t/combining-empty-arrays/9754/3 "2017-11-22T10:37:47Z")
Edited OP with working example, I thought that one did work but as something (I think my AV) tried to shut my computer down without warning I can’t be sure.
---
### Author:  [@stackexchangeuser4](https://forums.powershell.org/u/stackexchangeuser4)
#### Post date: [November 22, 2017, 10:47am UTC](https://forums.powershell.org/t/combining-empty-arrays/9754/4 "2017-11-22T10:47:08Z")
Oh, and just to further confuse things, with the above Test-Filter function:
```
Invoke-Command {
[Array]$arr1 = "A", "B", "C", "D" | Test-Filter | Sort
[Array]$arr2 = "E", "F", "G", "H" | Test-Filter | Sort | Select -First 1
[Array]$arr3 = 1, 2 | Test-Filter
[Array]$arr4 = "Jolly Cooperation" | Test-Filter
[Array]$combined = $arr1 + $arr2 + $arr3 + $arr4
Set-Variable -Name "DebugTest" -Value $combined -Scope Global
$combined.Count
}
1
```
That one caused me some grief trying to debug it =/
I’ve used a Where { $\_ } which seems a bit tidier but still really weird.
---
### Author:  [@dotnVo](https://forums.powershell.org/u/dotnVo)
#### Post date: [May 16, 2024, 8:37pm UTC](https://forums.powershell.org/t/combining-empty-arrays/9754/5 "2024-05-16T20:37:10Z")