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Use Get-Unique to Remove Duplicates From PowerShell Array It compares each item in a sorted list to the next item, removes duplicates, and returns only one member of each item. This cmdlet only works if the list is sorted. You can use the Sort-Object cmdlet to sort objects by property values.
We can remove duplicate element in an array by 2 ways: using temporary array or using separate index. To remove the duplicate element from array, the array must be in sorted order. If array is not sorted, you can sort it by calling Arrays. sort(arr) method.
You can use this parameter to find the unique values of object properties, such as the file names. Specifies input for Get-Unique . Enter a variable that contains the objects or type a command or expression that gets the objects. This cmdlet treats the input submitted by using InputObject as a collection.
delete element It's not easy to delete array element in PowerShell. Array data structure is not designed to change size. Instead of delete, just replace the value with $null .
Use Select-Object (whose alias is select) with the -Unique switch; e.g.:
$a = @(1,2,3,4,5,5,6,7,8,9,0,0)
$a = $a | select -Unique
Another option is to use Sort-Object (whose alias is sort, but only on Windows) with the -Unique switch, which combines sorting with removal of duplicates:
$a | sort -unique
In case you want to be fully bomb proofed, this is what I would advise:
@('Apples', 'Apples ', 'APPLES', 'Banana') |
Sort-Object -Property @{Expression={$_.Trim()}} -Unique
Output:
Apples
Banana
This uses the Property parameter to first Trim() the strings, so extra spaces are removed and then selects only the -Unique values.
More info on Sort-Object:
Get-Help Sort-Object -ShowWindow
$a | sort -unique
This works with case-insensitive, therefore removing duplicates strings with differing cases. Solved my problem.
$ServerList = @(
"FS3",
"HQ2",
"hq2"
) | sort -Unique
$ServerList
The above outputs:
FS3
HQ2
This is how you get unique from an array with two or more properties. The sort is vital and the key to getting it to work correctly. Otherwise you just get one item returned.
PowerShell Script:
$objects = @(
[PSCustomObject] @{ Message = "1"; MachineName = "1" }
[PSCustomObject] @{ Message = "2"; MachineName = "1" }
[PSCustomObject] @{ Message = "3"; MachineName = "1" }
[PSCustomObject] @{ Message = "4"; MachineName = "1" }
[PSCustomObject] @{ Message = "5"; MachineName = "1" }
[PSCustomObject] @{ Message = "1"; MachineName = "2" }
[PSCustomObject] @{ Message = "2"; MachineName = "2" }
[PSCustomObject] @{ Message = "3"; MachineName = "2" }
[PSCustomObject] @{ Message = "4"; MachineName = "2" }
[PSCustomObject] @{ Message = "5"; MachineName = "2" }
[PSCustomObject] @{ Message = "1"; MachineName = "1" }
[PSCustomObject] @{ Message = "2"; MachineName = "1" }
[PSCustomObject] @{ Message = "3"; MachineName = "1" }
[PSCustomObject] @{ Message = "4"; MachineName = "1" }
[PSCustomObject] @{ Message = "5"; MachineName = "1" }
[PSCustomObject] @{ Message = "1"; MachineName = "2" }
[PSCustomObject] @{ Message = "2"; MachineName = "2" }
[PSCustomObject] @{ Message = "3"; MachineName = "2" }
[PSCustomObject] @{ Message = "4"; MachineName = "2" }
[PSCustomObject] @{ Message = "5"; MachineName = "2" }
)
Write-Host "Sorted on both properties with -Unique" -ForegroundColor Yellow
$objects | Sort-Object -Property Message,MachineName -Unique | Out-Host
Write-Host "Sorted on just Message with -Unique" -ForegroundColor Yellow
$objects | Sort-Object -Property Message -Unique | Out-Host
Write-Host "Sorted on just MachineName with -Unique" -ForegroundColor Yellow
$objects | Sort-Object -Property MachineName -Unique | Out-Host
Output:
Sorted on both properties with -Unique
Message MachineName
------- -----------
1 1
1 2
2 1
2 2
3 1
3 2
4 1
4 2
5 1
5 2
Sorted on just Message with -Unique
Message MachineName
------- -----------
1 1
2 1
3 1
4 1
5 2
Sorted on just MachineName with -Unique
Message MachineName
------- -----------
1 1
3 2
Source: https://powershell.org/forums/topic/need-to-unique-based-on-multiple-properties/
If the list is sorted, you can use the Get-Unique cmdlet:
$a | Get-Unique
With my method you can completely remove duplicate values, leaving you with values from the array that only had a count of 1. It was not clear if this is what the OP actually wanted however I was unable to find an example of this solution online so here it is.
$array=@'
Bananna
Apple
Carrot
Pear
Apricot
Pear
Bananna
'@ -split '\r\n'
($array | Group-Object -NoElement | ?{$_.count -eq 1}).Name
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