Get-Unique
SYNOPSIS
Returns unique items from a sorted list.
SYNTAX
AsString (Default)
Get-Unique [-InputObject <PSObject>] [-AsString] [<CommonParameters>]
UniqueByType
Get-Unique [-InputObject <PSObject>] [-OnType] [<CommonParameters>]
DESCRIPTION
The `Get-Unique` cmdlet compares each item in a sorted list to the next item, eliminates duplicates, and returns only one instance of each item. The list must be sorted for the cmdlet to work properly.
`Get-Unique` is case-sensitive. As a result, strings that differ only in character casing are considered to be unique.
EXAMPLES
Example 1: Get unique words in a text file
$A = $( foreach ($line in Get-Content C:\Test1\File1.txt) {
$line.tolower().split(" ")
}) | Sort-Object | Get-Unique
$A.count
The first command gets the content of the File.txt file. It converts each line of text to lowercase letters and then splits each word onto a separate line at the space (" "). Then, it sorts the resulting list alphabetically (the default) and uses the `Get-Unique` cmdlet to eliminate any duplicate words. The results are stored in the `$A` variable.
The second command uses the Count property of the collection of strings in `$A` to determine how many items are in `$A`.
Example 2: Get unique integers in an array
1,1,1,1,12,23,4,5,4643,5,3,3,3,3,3,3,3 | Sort-Object | Get-Unique
1
3
4
5
12
23
4643
The first command takes an array of integers typed at the command line, pipes them to the `Sort-Object` cmdlet to be sorted, and then pipes them to `Get-Unique`, which eliminates duplicate entries.
Example 3: Get unique object types in a directory
Get-ChildItem | Sort-Object {$_.GetType()} | Get-Unique -OnType
The pipeline operator (|) sends the results to the `Sort-Object` cmdlet. The `$_.GetType()` statement applies the GetType method to each file or directory. Then, `Sort-Object` sorts the items by type. Another pipeline operator sends the results to `Get-Unique`. The OnType parameter directs `Get-Unique` to return only one object of each type.
Example 4: Get unique processes
Get-Process | Sort-Object | Select-Object processname | Get-Unique -AsString
The `Get-Process` command gets all of the processes on the computer. The pipeline operator (|) passes the result to `Sort-Object`, which, by default, sorts the processes alphabetically by ProcessName. The results are piped to the `Select-Object` cmdlet, which selects only the values of the ProcessName property of each object. The results are then piped to `Get-Unique` to eliminate duplicates.
The AsString parameter tells `Get-Unique` to treat the ProcessName values as strings. Without this parameter, `Get-Unique` treats the ProcessName values as objects and returns only one instance of the object, that is, the first process name in the list.
PARAMETERS
-AsString
Indicates that this cmdlet uses the data as a string. Without this parameter, data is treated as an object, so when you submit a collection of objects of the same type to `Get-Unique`, such as a collection of files, it returns just one (the first). You can use this parameter to find the unique values of object properties, such as the file names.
Type: System.Management.Automation.SwitchParameter
Parameter Sets: AsString
Aliases:
Required: False
Position: Named
Default value: False
Accept pipeline input: False
Accept wildcard characters: False
-InputObject
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. it does not enumerate individual items in the collection. Because the collection is a single item, input submitted by using InputObject is always returned unchanged.
Type: System.Management.Automation.PSObject
Parameter Sets: (All)
Aliases:
Required: False
Position: Named
Default value: None
Accept pipeline input: True (ByValue)
Accept wildcard characters: False
-OnType
Indicates that this cmdlet returns only one object of each type.
Type: System.Management.Automation.SwitchParameter
Parameter Sets: UniqueByType
Aliases:
Required: False
Position: Named
Default value: False
Accept pipeline input: False
Accept wildcard characters: False
CommonParameters
This cmdlet supports the common parameters: -Debug, -ErrorAction, -ErrorVariable, -InformationAction, -InformationVariable, -OutVariable, -OutBuffer, -PipelineVariable, -Verbose, -WarningAction, and -WarningVariable. For more information, see about_CommonParameters.
INPUTS
System.Management.Automation.PSObject
You can pipe any type of object to `Get-Unique`.
OUTPUTS
System.Management.Automation.PSObject
The type of object that `Get-Unique` returns is determined by the input.
NOTES
You can also refer to `Get-Unique` by its built-in alias, `gu`. For more information, see about_Aliases (../Microsoft.PowerShell.Core/About/about_Aliases.md).
To sort a list, use Sort-Object. You can also use the Unique parameter of `Sort-Object` to find the unique items in a list.