PowerShell is object-oriented so there’s not much text filtering and regex magic required compared to Linux and grep. Yet occasionally, it would be efficient and comfortable to filter command object by simple text patterns.
And it works -kinda. PowerShell does come with a grep-like command, the cmdlet Select-String. While it excels at filtering file content, it isn’t useful at first when trying to filter command output.
Let’s assume you’re interested in running services only. Filtering for “running” yields nothing:
PS> Get-Service | Select-String Running
That’s not the fault of Select-String, though. Select-String needs text input, and cmdlets typically return rich objects, not text. By converting command output to string, all works fine:
PS> Get-Service | Out-String -Stream | Select-String Running Running AdobeARMservice Adobe Acrobat Update Service Running AgentShellService Spiceworks Agent Shell Service Running Appinfo Application Information Running AppMgmt Application Management Running AppXSvc AppX Deployment Service (AppXSVC) ...
That’s awesome if you don’t mind that the end result is now plain text. That seems to be the price for simple text filtering.
No, it isn’t. You can create your own filter command that *temporarily* converts incoming objects to text, does the text pattern match, and then returns the unchanged rich objects. Sounds simple, and it really is. Here is PowerShell’s grep:
filter grep ([string]$Pattern) { if ((Out-String -InputObject $_) -match $Pattern) { $_ } }
Run the code, then try it:
PS> Get-Service | grep running Status Name DisplayName ------ ---- ----------- Running AdobeARMservice Adobe Acrobat Update Service Running AgentShellService Spiceworks Agent Shell Service Running Appinfo Application Information Running AppMgmt Application Management ...
It’s beautifully simple to use and, best of all, outputs rich objects so you can still access its properties
PS> Get-Service | grep running | Select-Object Name, StartType, Status Name StartType Status ---- --------- ------ AdobeARMservice Automatic Running AgentShellService Automatic Running Appinfo Manual Running AppMgmt Manual Running AppXSvc Manual Running AudioEndpointBuilder Automatic Running
