Filtering in Powershell are one of the most expressions i’m use for drill down get-cmdlet results. There are so much situations we would like to have some simple and clear technique to see the results in different views.  

As an Example I will use get-process with three views:  

1. SlowMotion (More about here.) 
2. Startet Services 
3. Stopped Services who begins with “VW*”

The most scripts are using one view per File.

Get-ServicesByStopped.ps1 Get-ServicesInSlowMotion.ps1

The scripts above are displaying two different views. This will give you very fast a big collection of files. 

One other approach is display views over Parameters. Maybe you will use

.\Get-MyProcesses.ps1 –ReportByVMWareStopped

Example 1:

Param(
	[switch] $ReportBySlowMotion, 
	[switch] $ReportByStartet,
	[switch] $ReportByVMWareStopped
)
 
If($ReportBySlowMotion)
{
	foreach($process in @(Get-service))
	{$process; Start-Sleep -milliseconds 500}
}
 
if($ReportByStartet)
{Get-service | ?{$_.Status -eq "Startet"}}
 
if($ReportByVMWareStopped)
{Get-service | ?{$_.Status -eq "Stopped" -and $_.Name -ilike "VM*"}}

Using filters dynamic is getting scripting simple to extend , and flexible to use.  

Basicly I create a few lines that do the following:  

• First normaly create filters in the Syntax “filter Filter-xxx{…}”. This is the best Advantage because just define the filter und you will get the selection for the filter in your Script.
• Load the filters when its needed from the Function Provider
• Display the avaible filters so that the user can choose the right one.
• Load the definition and show the result as selected.
  

 

Example: Dynamic Filters

## Creating the Filters
filter Filter-VMWare-Stopped{if($_.Status -eq "Stopped" -and $_.Name -ilike "VM*"){$_}}
filter Filter-Startet{if($_.Status -eq "Startet"){$_}}
filter Filter-SlowMotion{$_; Start-Sleep -milliseconds 500}
 
## Get All Filters by Name (Scoped filters need some Cleanups)
$filterobjects = & get-childitem function: | ?{$_.CommandType -eq 'Filter'}
 
$filterobjects | ft name
 
$choosedFilter = read-host "`nChoose your Filter"
 
## Choose the filter Definition (For the Filter-Stopped it will contain if($_.Status -eq "Stopped"){$_})
$choosedFilterDefinition = (get-item function:$choosedFilter).Definition
 
## The Where-Object need's a Scriptblock.
$currentFilter = [scriptblock]::Create($choosedFilterDefinition)
 
get-service | where-object $currentFilter | ft -autosize Name, Status, DisplayName

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