PowerShell -Filter Command or Parameter

PowerShell -Filter Parameter

Information overload?  The ideal method when PowerShell delivers too much data is to append -Filter.  Incidentally, newbies refer to PowerShell's -Filter as a command rather than a parameter.

Topics for PowerShell's -Filter Parameter

• Example 1a: Filter for Executables
• Example 2a: Compare PowerShell -Filter with Where-Object
• Example 3: PowerShell Sifting on Multiple Parameters
• List of PowerShell Cmdlets Featuring -Filter

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Example 1a: Filter CommonProgramFiles for Executables

The scenario is that we want to find a particular type of file; in this instance executables amongst the Common Program Files.

Note 1: On my machine, $env:CommonProgramFiles translates to C:\Program Files\Common Files>.

Example 1b: Affects of -Filter
Let us tot-up the .exe files filtered using the .count method.

Note 2: These examples are purely to put the -Filter parameter though its paces; for a specific task there may be better methods that don't involve -Filter at all.

PowerShell's Explanation of the -Filter Parameter

To find out more about a cmdlet's parameters type:
Get-Help cmdlet-name -Full

Note 3: The default position for -Filter is 2, after -Path; all very logical.  My point is that if you don't explicitly declare your parameters, whatever is in the second position is assumed to be a filter.

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Example 2a: Compare PowerShell -Filter with Where-Object

Each time I use PowerShell's Where-Object cmdlet I ask myself, could I get better performance using -Filter instead?  To compare the two techniques I will employ Measure-Object

Example 2b: Comparative Slowness of Where-Object
Where-Object needs to do it's sifting once it receives the stream from the pipeline (|).  The -Filter parameter is quick because the provider applies the filter as it retrieves the objects. 

Note 3: There are situations where you need Where-Object, but it's always worth thinking, 'Would PowerShell's -Filter command be better here?

Note 4: Occasionally, you get different results with Where-Object and -Filter; for instance -Filter interprets *.exe as *.exe*

List of PowerShell Cmdlets Featuring -Filter

Let us research other which PowerShell cmdlets contain the -Filter parameter. The technique employs Get-Command to retrieve all the cmdlets; then it filters using the .parameter.keys property.

Note 5: Here is a useful task for Where-Object.  My installation of PowerShell shows 31 cmdlets containing the parameter "filter".

Note 6: I prefer to employ the conditional operator -Contains rather than -Match.

Selected Results: Cmdlets Containing -Filter

Most of the results for -Filter use either the noun 'Item' or 'Content'.

Note7: Observe how most of the results contain either the noun 'Item', or 'Content'.

However, I must give a special mention for Get-WmiObject as I have found many examples of -Filter speeding up scripts that formerly employed Where-Object.

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Example 3: PowerShell Sifting on Multiple Parameters

To date, I have not been able to persuade the -Filter parameter to accept multiple values.  There seems no way to introduce the concept 'or' to -Filter.  One work-around is to reconsider the Where-Object construction; now you have a rich source of comparison parameters (-Match -Contains), not to mention -Or itself.

Filter with -Include
Another Work-around is to employ Get-ChildItem's -Include parameter.

Note 8: Testing with Measure-Command reveals there is no difference in the time it takes to return the list of files.

Note 9: Measuring with the .count method reveals that Where-Object finds slightly more files than -Include.

See more on PowerShell WMI -Filter »

Summary: PowerShell -Filter Command

PowerShell has several methods for dealing with cmdlets producing too much data.  My first choice would be to append -Filter.  Alternative techniques would involve the Where-Object cmdlet, or else the -Include parameter.

See more examples of PowerShell Parameters

• PowerShell Parameters  • Syntax  • PowerShell functions  • PowerShell Wmi Filter

• PowerShell -confirm  • WhatIf  • -Match  • -Like  • Where  • Free WMI Monitor

• PowerShell -Filter Command  • PowerShell Filter   • -Replace  • Windows PowerShell

Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.