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Group-Object

  • Reference
Module:
Microsoft.PowerShell.Utility

Groups objects that contain the same value for specified properties.

Syntax

Group-Object
     [[-Property] <Object[]>]
     [-NoElement]
     [-AsHashTable]
     [-AsString]
     [-InputObject <PSObject>]
     [-Culture <String>]
     [-CaseSensitive]
     [<CommonParameters>]

Description

The Group-Object cmdlet displays objects in groups based on the value of a specified property. Group-Object returns a table with one row for each property value and a column that displays the number of items with that value.

If you specify more than one property, Group-Object first groups them by the values of the first property, and then, within each property group, it groups by the value of the next property.

Examples

Example 1: Group files by extension

This example recursively gets the files under $PSHOME and groups them by file name extension. The output is sent to the Sort-Object cmdlet which sorts them by the count files found for the given extension. The empty Name represents directories.

This example uses the NoElement parameter to omit the members of the group.

$files = Get-ChildItem -Path $PSHOME -Recurse
$files | Group-Object -Property extension -NoElement | Sort-Object -Property Count -Descending

Count Name
----- ----
  365 .xml
  231 .cdxml
  197
  169 .ps1xml
  142 .txt
  114 .psd1
   63 .psm1
   49 .xsd
   36 .dll
   15 .mfl
   15 .mof
...

Example 2: Group integers by odds and evens

This example shows how to use script blocks as the value of the Property parameter.

This command displays the integers from 1 to 20, grouped by odds and even.

1..20 | Group-Object -Property {$_ % 2}

Count Name                      Group
----- ----                      -----
   10 1                         {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}
   10 0                         {2, 4, 6, 8, 10, 12, 14, 16, 18, 20}

Example 3: Group event log events by EntryType

These commands display the 1,000 most recent entries in the System event log, grouped by EntryType.

In the output, the Count column represents the number of entries in each group, the Name column represents the EventType values that define a group, and the Group column represents the objects in each group.

Get-WinEvent -LogName System -MaxEvents 1000 | Group-Object -Property LevelDisplayName

Count Name          Group
----- ----          -----
  153 Error         {System.Diagnostics.Eventing.Reader.EventLogRecord, System.Diagnostics.�
  722 Information   {System.Diagnostics.Eventing.Reader.EventLogRecord, System.Diagnostics.�
  125 Warning       {System.Diagnostics.Eventing.Reader.EventLogRecord, System.Diagnostics.�

Example 4: Group processes by priority class

This example demonstrates the effect of the NoElement parameter. These commands group the processes on the computer by priority class.

The first command uses the Get-Process cmdlet to get the processes on the computer. It uses a pipeline operator | to send the results to Group-Object, which groups the objects by the value of the PriorityClass property of the process.

The second command is identical to the first, except that it uses the NoElement parameter to eliminate the members of the group from the output. The result is a table with only the count and property value name.

The results are shown in the following sample output.

Get-Process | Group-Object -Property PriorityClass

Count Name         Group
----- ----         -----
   55 Normal       {System.Diagnostics.Process (AdtAgent), System.Diagnosti...
    1              {System.Diagnostics.Process (Idle)}
    3 High         {System.Diagnostics.Process (Newproc), System.Diagnostic...
    2 BelowNormal  {System.Diagnostics.Process (winperf),

Get-Process | Group-Object -Property PriorityClass -NoElement

Count Name
----- ----
   55 Normal
    1
    3 High
    2 BelowNormal

Example 5: Group processes by name

The following example uses Group-Object to multiple instances of processes running on the local computer.

Get-Process | Group-Object -Property Name -NoElement | Where {$_.count -gt 1}

Count Name
----- ----
2     csrss
5     svchost
2     winlogon
2     wmiprvse

Example 8: Group objects in a hash table

This example uses the AsHashTable and AsString parameters to return the groups in a hash table, that is, as a collection of key-value pairs.

In the resulting hash table, each property value is a key, and the group elements are the values. Because each key is a property of the hash table object, you can use dot notation to display the values.

The first command gets the Get and Set cmdlets in the session, groups them by verb, returns the groups as a hash table, and saves the hash table in the $A variable.

The second command displays the hash table in $A. There are two key-value pairs, one for the Get cmdlets and one for the Set cmdlets.

The third command uses dot notation to display the values of the Get key in $A. The values are CmdletInfo object. The AsString parameter does not convert the objects in the groups to strings.

$A = Get-Command get-*, set-* -CommandType cmdlet | Group-Object -Property verb -AsHashTable -AsString
$A

Name    Value
----    -----
Get     {Get-PSCallStack, Get-PSBreakpoint, Get-PSDrive, Get-PSSession...}
Set     {Set-Service, Set-StrictMode, Set-PSDebug, Set-PSSessionConfiguration...}

$A.get

CommandType     Name                 Definition
-----------     ----                 ----------
Cmdlet          Get-PSCallStack      Get-PSCallStack [-Verbose] [-Debug] [-ErrorAction <ActionPrefer...
Cmdlet          Get-PSBreakpoint     Get-PSBreakpoint [[-Id] <Int32[]>] [-Verbose] [-Debug] [-ErrorA...
Cmdlet          Get-PSDrive          Get-PSDrive [[-Name] <String[]>] [-Scope <String>] [-PSProvider...
...

Parameters

-AsHashTable

Indicates that this cmdlet returns the group as a hash table. The keys of the hash table are the property values by which the objects are grouped. The values of the hash table are the objects that have that property value.

By itself, the AsHashTable parameter returns each hash table in which each key is an instance of the grouped object. When used with the AsString parameter, the keys in the hash table are strings.

Type:SwitchParameter
Aliases:AHT
Position:Named
Default value:GroupInfo object
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-AsString

Indicates that this cmdlet converts the hash table keys to strings. By default, the hash table keys are instances of the grouped object. This parameter is valid only when used with the AsHashTable parameter.

Type:SwitchParameter
Position:Named
Default value:GroupInfo objects
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-CaseSensitive

Indicates that this cmdlet makes the grouping case-sensitive. Without this parameter, the property values of objects in a group might have different cases.

Type:SwitchParameter
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-Culture

Specifies the culture to use when comparing strings.

Type:String
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-InputObject

Specifies the objects to group. Enter a variable that contains the objects, or type a command or expression that gets the objects.

When you use the InputObject parameter to submit a collection of objects to Group-Object, Group-Object receives one object that represents the collection. As a result, it creates a single group with that object as its member.

To group the objects in a collection, pipe the objects to Group-Object.

Type:PSObject
Position:Named
Default value:None
Required:False
Accept pipeline input:True
Accept wildcard characters:False

-NoElement

Indicates that this cmdlet omits the members of a group from the results.

Type:SwitchParameter
Position:Named
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

-Property

Specifies the properties for grouping. The objects are arranged into groups based on the value of the specified property.

The value of the Property parameter can be a new calculated property. To create a calculated, property, create a hash table with an Expression key that specifies a string or script block value.

Type:Object[]
Position:0
Default value:None
Required:False
Accept pipeline input:False
Accept wildcard characters:False

Inputs

PSObject

You can pipe any object to Group-Object.

Outputs

Microsoft.PowerShell.Commands.GroupInfo or System.Collections.Hashtable

When you use the AsHashTable parameter, Group-Object returns a hash table. Otherwise, it returns a GroupInfo object.

Notes

  • You can also use the GroupBy parameter of the formatting cmdlets (such as Format-Table and Format-List) to group objects. Unlike Group-Object, which creates a single table with a row for each property value, the GroupBy parameters create a table for each property value with a row for each item that has the property value.

    Group-Object does not require that the objects being grouped be of the same Microsoft .NET Framework type. When grouping objects of different .NET Framework types, Group-Object uses the following rules:

    • Same Property Names and Types. If the objects have a property with the specified name, and the property values have the same .NET Framework type, the property values are grouped by using the same rules that would be used for objects of the same type.

    • Same Property Names, Different Types. If the objects have a property with the specified name, but the property values have a different .NET Framework type in different objects, Group-Object uses the .NET Framework type of the first occurrence of the property as the .NET Framework type for that property group. When an object has a property with a different type, the property value is converted to the type for that group. If the type conversion fails, the object is not included in the group.

    • Missing Properties. Objects that do not have a specified property are considered ungroupable. Ungroupable objects appear in the final GroupInfo object output in a group named AutomationNull.Value.