Compare-Object
Compares two sets of objects.
Syntax
Compare-Object
[-ReferenceObject] <PSObject[]>
[-DifferenceObject] <PSObject[]>
[-SyncWindow <Int32>]
[-Property <Object[]>]
[-ExcludeDifferent]
[-IncludeEqual]
[-PassThru]
[-Culture <String>]
[-CaseSensitive]
[<CommonParameters>]Description
The Compare-Object cmdlet compares two sets of objects. One set of objects is the reference,
and the other set of objects is the difference.
The result of the comparison indicates whether a property value appeared only in the reference
object (<=) or only in the difference object (=>). If the IncludeEqual parameter is
used, (==) indicates the value is in both objects.
If the reference or the difference objects are null ($null), Compare-Object generates a
terminating error.
Some examples use splatting to reduce the line length of the code samples. For more information, see
about_Splatting. And, the examples use two
text files, with each value on a separate line. Testfile1.txt contains the values: dog, squirrel,
and bird. Testfile2.txt contains the values: cat, bird, and racoon.
Examples
Example 1: Compare the content of two text files
This example compares the contents of two text files. The output displays only the lines that are
different between the files. Testfile1.txt is the reference object (<=) and
Testfile2.txtis the difference object (=>).
Lines with content that appear in both files aren't displayed.
Compare-Object -ReferenceObject $(Get-Content -Path C:\Test\Testfile1.txt) -DifferenceObject $(Get-Content -Path C:\Test\Testfile2.txt)
InputObject SideIndicator
----------- -------------
cat =>
racoon =>
dog <=
squirrel <=Example 2: Compare each line of content in two text files
This example uses the IncludeEqual to compare each line of content in two text files. All the lines of content from both files are displayed.
The SideIndicator specifies if the line appears in the Testfile1.txt reference object
(<=), Testfile2.txt difference object (=>), or both files (==).
$objects = @{
ReferenceObject = $(Get-Content -Path C:\Test\Testfile1.txt)
DifferenceObject = $(Get-Content -Path C:\Test\Testfile2.txt)
}
Compare-Object @objects -IncludeEqual
InputObject SideIndicator
----------- -------------
bird ==
cat =>
racoon =>
dog <=
squirrel <=Example 3: Compare each line of content and exclude the differences
This example uses the IncludeEqual and ExcludeDifferent parameters to compare each line of content in two text files.
Because the command uses the ExcludeDifferent parameter, the output only contains lines
contained in both files, as shown by the SideIndicator (==).
$objects = @{
ReferenceObject = $(Get-Content -Path C:\Test\Testfile1.txt)
DifferenceObject = $(Get-Content -Path C:\Test\Testfile2.txt)
}
Compare-Object @objects -IncludeEqual -ExcludeDifferent
InputObject SideIndicator
----------- -------------
bird ==Example 4: Compare two sets of process objects
This example compares two sets of objects that contain the computer's running processes.
$Processes_Before = Get-Process
notepad.exe
$Processes_After = Get-Process
Compare-Object -ReferenceObject $Processes_Before -DifferenceObject $Processes_After
InputObject SideIndicator
----------- -------------
System.Diagnostics.Process (notepad) =>The Get-Process cmdlet gets the computer's running processes and stores them in the
$Processes_Before variable.
The notepad.exe application is started.
Get-Process gets the computer's updated list of running processes and stores them in the
$Processes_After variable.
The Compare-Object compare the two sets of process objects stored in the $Processes_Before and
$Processes_After variables. The output displays the difference, notepad.exe, from the
$Processes_After object.
Parameters
-CaseSensitive
Indicates that comparisons should be case-sensitive.
| Type: | SwitchParameter |
| Position: | Named |
| Default value: | False |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-Culture
Specifies the culture to use for comparisons.
| Type: | String |
| Position: | Named |
| Default value: | None |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-DifferenceObject
Specifies the objects that are compared to the reference objects.
| Type: | PSObject[] |
| Position: | 1 |
| Default value: | None |
| Required: | True |
| Accept pipeline input: | True |
| Accept wildcard characters: | False |
-ExcludeDifferent
Indicates that this cmdlet displays only the characteristics of compared objects that are equal. The differences between the objects are discarded.
Use ExcludeDifferent with IncludeEqual to display only the lines that match between the reference and difference objects.
If ExcludeDifferent is specified without IncludeEqual, there's no output.
| Type: | SwitchParameter |
| Position: | Named |
| Default value: | False |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-IncludeEqual
IncludeEqual displays the matches between the reference and difference objects.
By default, the output also includes the differences between the reference and difference objects.
| Type: | SwitchParameter |
| Position: | Named |
| Default value: | False |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-PassThru
When you use the PassThru parameter, Compare-Object omits the PSCustomObject wrapper
around the compared objects and returns the differing objects, unchanged.
| Type: | SwitchParameter |
| Position: | Named |
| Default value: | False |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-Property
Specifies an array of properties of the reference and difference objects to compare.
| Type: | Object[] |
| Position: | Named |
| Default value: | None |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-ReferenceObject
Specifies an array of objects used as a reference for comparison.
| Type: | PSObject[] |
| Position: | 0 |
| Default value: | None |
| Required: | True |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
-SyncWindow
Specifies the number of adjacent objects that Compare-Object inspects while looking for a match in
a collection of objects. Compare-Object examines adjacent objects when it doesn't find the object
in the same position in a collection. The default value is [Int32]::MaxValue, which means that
Compare-Object examines the entire object collection.
| Type: | Int32 |
| Position: | Named |
| Default value: | [Int32]::MaxValue |
| Required: | False |
| Accept pipeline input: | False |
| Accept wildcard characters: | False |
Inputs
You can send an object down the pipeline to the DifferenceObject parameter.
Outputs
None
If the reference object and the difference object are the same, there's no output.
If the objects are different, Compare-Object wraps the differing objects in a PSCustomObject
wrapper with a SideIndicator property to reference the differences. When you use the
PassThru parameter, Compare-Object omits the PSCustomObject wrapper around the compared
objects and returns the differing objects, unchanged.