Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm learning PowerShell, so I'm doing stuff like this a lot:

Get-Command | Out-String -Stream | ss child 

(ss is an alias for select-string).

I'm getting tired of typing Out-string -Stream all the time, so in Unix I'd just create an alias for it. However this doesn't work in Powershell.

  • I created it as an alias, and it errored out (I think I understand that).
  • I created it as a function, but it swallows all my output
  • I created it as a filter, and that also produced no output.

How can I do this?

Using *child* as the argument is probably the best way to do this particular task, but I'm really using this as an example to learn how to write PS functions.

I just want the function to replace the 'Out-string -Stream' part, so that instead of:

Get-Command | Out-String -Stream | ss child   

I'll be able to write:

Get-Command | oss | ss child 

I'm guessing I need to use ValueFromPipeline, or the $input variable, like Matt shows.

Okay, I got it. I guess I need to explicitly say to read from the pipeline. Instead of:

function oss { Out-String -Stream } 

I need to say:

function oss { $input | Out-String -Stream } 

I wonder how I missed that in the documentation?

share|improve this question
I will poke around and see if I can find an answer to your question. In the meantime however, I suspect that there is a better way to get the same result: Get-Command *child* – EBGreen Jul 23 '11 at 7:39
In PowerShell 3, oss is pre-defined for you. – jeatsy Mar 3 '13 at 1:05
up vote 1 down vote accepted

What do you mean a function swallows all your output?

I tried this and get the same outputs:

function MySS {
    param (
        [string] $SearchString
    Process {
        Get-Command | Out-String -Stream | Select-String -Pattern $SearchString

Running Get-Member and GetType on the output return the same form the function and piped command.

EDIT: If you wanted to us other originating functions

function MySS2 {
    param (
                    Mandatory = $True,
                    ValueFromPipeline = $true)]
                    Mandatory = $True,
                    ValueFromPipeline = $false,
            Position = 0)]
        [string] $SearchString
    Process {
        $input | Out-String -Stream | Select-String -Pattern $SearchString


Get-Command | MySS2 "Get"
get-help get-alias | MySS2 "Get"

EDIT: simplest form (select string commented out):

function MyOSS {
    param ($input)
    $input | Out-String -Stream #| Select-String "Get"

EDIT: final edit i think! :-)

I see you figured it out yourself Jonathan - glad to have helped and I didn't know you could use $input without declaring it as a parameter. That's cool.

share|improve this answer
'Swallow my output' means that when I run Get-Command I get screens of output written to my screen, but when I run Get-Command | oss, I get no output written to screen. (I'm using ISE, if that matters). – jonathan Jul 23 '11 at 13:53
I should add that my function looks like function oss { Out-String -Stream} and then filter oss { Out-String -Stream} – jonathan Jul 23 '11 at 13:55
Do I really need to resort to cmdletbinding just to read from and write to the pipeline? – jonathan Jul 23 '11 at 14:07
No, it'll work without - I always add cmdletbinding when doing a function though - mainly for write-verbose. – Matt Jul 25 '11 at 12:00
the function function oss { Out-String -Stream} doesn't do anything - there's no variable processing etc... – Matt Jul 25 '11 at 12:01

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.