Suppressing Output

#powershell

Simple Methods

| Out-Null

> $NULL

Using Streams (BASH like)

Stream	Cmdlet	Id
Debug	Write-Debug	5
Error	Write-Error	2
Informatin	Write-Information	6
Verbose	Write-Verbose	4
Warning	Write-Warning	3
Output	Write-Output	1
Host	Write-Host	6
https://powershell.one/code/9.html

Redirecting Streams

By default, only the Output stream is assigned to variables. All other streams either are emitted directly to the console, or are hidden (controlled by your preference variables).

To include the information from other streams in your variables, use redirection: take the stream id to redirect the stream to the output stream (&1).

This line redirects errors and warnings to the output stream and assigns them to a variable:

# include errors and warnings in variable results: 
$all = Get-Process -FileVersionInfo 2>&1 3>&1`

After you run it, $all contains the results plus all errors and warnings.

Hiding standard output (STDOUT)

Here is a proof of concept illustrating how you can hide messages emitted by Write-Host:

& { 
Write-Warning "A Warning" 
"Regular Output" 
Write-Host "This will dissappear!" 
} 6>$null

By redirecting stream 6 to null, all outputs from Write-Host and Write-Information are discarded. You can append 6>$null to any command or script call.

Destroy it all

*>&1

Silencing All Output

To silence direct console output and discard all output, you can temporarily disable the internal PowerShell command Out-Default. This command is used privately to write directly to the console.

Read more about Out-Default if you like.

While you really can’t disable the command (it is hard-coded to PowerShell), you can replace it with your own functions, effectively overwriting it. So here is some example code that runs Get-WindowsUpdateLog without showing all the status messages:

# temporarily overwrite Out-Default
function Out-Default {}

# run your code (guaranteed no output)
Get-WindowsUpdateLog

# test any other direct console write
[Console]::WriteLine("Hello")

# restore Out-Default
Remove-Item -Path function:Out-Default

As long as Out-Default is replaced by your own empty function, PowerShell emits no output whatsoever. This applies to scripts as well as interactive commands you may invoke. So make sure you remove your function Out-Default once you are ready to see output again.

This Out-Default trick isn’t as edge-casy as you may think. When you browse user groups you’ll discover plenty of threads that deal with this issue.

PowerShell users have resorted to all kinds of creative and complex workarounds to discard direct console output, i.e. running code as a job or in another PowerShell instance with a hidden window.

You know now: that’s a bit of overkill. Simply shadow Out-Default for as long as you want to silence PowerShell.