May 21st, 2010 
ivolooser 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:
- SlowMotion (More about here.)
- Startet Services
- 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
