OutVariable, Parameter

Building on the Perl motto; “There’s more than one way to do it”, PowerShell lovers will tell you that they can play too. Basically the -OutVariable parameter stores the output from a cmdlet to a variable and at the same time letting the cmdlet display all the output to the screen. For example looking at the Get-ChildItem cmdlet you can store the output in a variable by doing:

$myChildren = Get-ChildItem

Using the -OutVariable parameter you would instead type:

Get-ChildItem -OutVariable myChildren

This would also store the output in the myChildren variable (notice the lack of the $ sign), but unlike the first example the output would be printed to the screen.

This might sound a lot like the Tee-Object cmdlet. However you can also use OutVariable like this:

Get-ChildItem Directory1 -OutVariable myChildren
Get-ChildItem Directory2 -OutVariable +myChildren

This way the $myChildren variable would hold the contents of both Directory1 and Directory2. Another difference, if you’re in a hurry and want to juice out some performance, can be shown by the Measure-Command cmdlet.

Measure-Command {Get-ChildItem | Tee-Object -variable myTeeOutput}
TotalMilliseconds : 3,3151

Measure-Command {Get-ChildItem -OutVariable myOutVariableOutput}
TotalMilliseconds : 2,0668

Folks, we have a winner! But what will we do with all the extra free time?

If you just want to store the variable and not display the output you can use the Out-Null cmdlet:

Get-ChildItem -OutVariable myChildren | Out-Null