Removing duplicate values ​​from a PowerShell array

Question

How to remove duplicates from a PowerShell array?

$a = @(1,2,3,4,5,5,6,7,8,9,0,0) 

Answer 1

Use Select-Object (whose alias is select ) with the -Unique switch; eg.:

 $a = @(1,2,3,4,5,5,6,7,8,9,0,0) $a = $a | select -Unique 

Answer 2

Another option is to use Sort-Object (whose alias is sort , but only on Windows) with
-Unique , which combines sorting with duplicate removal:

 $a | sort -unique 

Answer 3

 $a | sort -unique 

This works case-sensitive, so duplicate rows with different registers are deleted. Solved my problem.

 $ServerList = @( "FS3", "HQ2", "hq2" ) | sort -Unique $ServerList 

The above findings:

 FS3 HQ2 

Answer 4

If the list is sorted, you can use the Get-Unique cmdlet:

  $a | Get-Unique 

Answer 5

In case you want to be a fully proven bomb, this is what I would advise:

 @('Apples', 'Apples ', 'APPLES', 'Banana') | Sort-Object -Property @{Expression={$_.Trim()}} -Unique 

Output:

 Apples Banana 

This uses the Property parameter for the first line of Trim() , so extra whitespace is removed, and then only -Unique values ​​are selected.

Additional information about Sort-Object :

 Get-Help Sort-Object -ShowWindow 

Answer 6

Whether you use SORT -UNIQUE , SELECT -UNIQUE or GET-UNIQUE from Powershell 2.0 to 5.1, all of the above examples are for single-column arrays. I have yet to get this to work in arrays with multiple columns, to DELETE duplicate rows, to leave single occurrences of the row in the specified columns, or to develop an alternative script solution. Instead, these cmdlets only returned rows in an array that happened ONCE in the singular and flushed everything that had a duplicate. Usually I have to delete duplicates manually from the final CSV output in Excel to complete the report, but sometimes I would like to continue working with the specified data in Powershell after deleting the duplicates.

Answer 7

Using my method, you can completely remove duplicate values, leaving you with the values ​​from an array that only had the number 1. It’s not clear if this is really what the OP really wanted, but I couldn’t find an example of this solution on the Internet, so here .

 $array=@' Bananna Apple Carrot Pear Apricot Pear Bananna '@ -split '\r\n' ($array | Group-Object -NoElement | ?{$_.count -eq 1}).Name