The pipeline is a feature that allows the output of one command to be automatically transferred into another command. You can string any number of commands together and they will execute sequentially left to right. when it reaches the last command the results of this will be displayed on the screen or passed to a variable.
The simplest use of the pipleine is to format the output as a list or table
Get-Service | Format-List Get-Service | Format-Table
You may see these shorterned to their alias fl or ft
Get-Service | ft Get-Service | fl
What this series of commands is doing is getting all services on the local machine and then formatting them into either a list or table. From left to right get-service then take the output and format-list
Using the pipeline
We can use the pipeline to automate tasks without knowing the list of items we need to change
Let’s consider a list of processes, we can find all running processes with a get command but which one? Lets use Get-Command to find it
Get-Command *process* returns a list of cmdlets we can use against processes, we can find them with Get-Process, stop them with Stop-Process and start them with Start-Process
We have a number of Notepad instances open on our machine and we want to stop the processes, how can we do that in one command? Lets start by finding all the running processes. I’ll start by looking at the syntax of the cmdlet using the help
we can see in the output of the Get-Process cmdlet that there is a column called processName so lets start with that can we list only the ones named ‘Notepad’
Get-Process -ProcessName 'Notepad'
It appears we can
now using the pipeline we can send this output to the stop-process command
Get-Process -ProcessName ‘Notepad’ | stop-process
This stops all running processes with the ProcessName ‘notepad’ – we can confirm this has worked by re-runnign the Get-Process command and checking their are none running
Other Uses
Other common commands we will pipe into frequently that we will look at in other posts
Sort-Object(aliassort)Where-Object(aliaswhere)Filter-Object(aliasfilter)Group-Object(aliasgroup)Format-Table(aliasft)Format-List(aliasfl)Select-Object(aliasselect)