powershellconsole-output

PowerShell output is crossing between functions


I am writing a PowerShell script in version 5.1 on Windows 10 that gets certain pieces of information about a local system ( and eventually its subnets ) and outputs them into a text file. At first, I had all of the aspects in a single function. I ran into output issues when outputting getUsersAndGroups and getRunningProcesses functions, where output from getUsersAndGroups would be injected into the output of getRunningProcesses.

The two functions are:

    # Powershell script to get various properties and output to a text file

    Function getRunningProcesses()
    {
        # Running processes
        Write-Host "Running Processes:
    ------------ START PROCESS LIST ------------
        "
        Get-Process | Select-Object name,fileversion,productversion,company
        Write-Host "
    ------------- END PROCESS LIST -------------
    "
    }

    Function getUsersAndGroups()
    {
        # Get Users and Groups
        Write-Host "Users and Groups:"
        $adsi = [ADSI]"WinNT://$env:COMPUTERNAME"
        $adsi.Children | where {$_.SchemaClassName -eq 'user'} | Foreach-Object {
            $groups = $_.Groups() | Foreach-Object {$_.GetType().InvokeMember("Name", 'GetProperty', $null, $_, $null)}
            $_ | Select-Object @{n='Username';e={$_.Name}},@{n='Group';e={$groups -join ';'}}
        }
    }

    getRunningProcesses
    getUsersAndGroups

When I call getUsersAndGroups after getRunningProcesses, the output looks like this ( does not output getUsersAndGroups at all ):

Running Processes:
        ------------ START PROCESS LIST ------------


Name                FileVersion                                       ProductVersion Company                    
----                -----------                                       -------------- -------                    
armsvc                                                                                                          
aswidsagenta                                                                                                    
audiodg                                                                                                         
AVGSvc                                                                                                          
avgsvca                                                                                                         
avguix              1.182.2.64574                                     1.182.2.64574  AVG Technologies CZ, s.r.o.               
conhost             10.0.14393.0 (rs1_release.160715-1616)            10.0.14393.0   Microsoft Corporation      
csrss                                                                                                           
csrss                                                                                                           
dasHost                                                                                                         
dwm                                                                                                             
explorer            10.0.14393.0 (rs1_release.160715-1616)            10.0.14393.0   Microsoft Corporation      
hkcmd               8.15.10.2900                                      8.15.10.2900   Intel Corporation          
Idle                                                                                                            
igfxpers            8.15.10.2900                                      8.15.10.2900   Intel Corporation          
lsass                                                                                                           
MBAMService                                                                                                     
mDNSResponder                                                                                                   
Memory Compression                                                                                              
powershell_ise      10.0.14393.103 (rs1_release_inmarket.160819-1924) 10.0.14393.103 Microsoft Corporation      
RuntimeBroker       10.0.14393.0 (rs1_release.160715-1616)            10.0.14393.0   Microsoft Corporation      
SearchFilterHost                                                                                                
SearchIndexer                                                                                                   
SearchProtocolHost                                                                                              
SearchUI            10.0.14393.953 (rs1_release_inmarket.170303-1614) 10.0.14393.953 Microsoft Corporation      
services                                                                                                        
ShellExperienceHost 10.0.14393.447 (rs1_release_inmarket.161102-0100) 10.0.14393.447 Microsoft Corporation      
sihost              10.0.14393.0 (rs1_release.160715-1616)            10.0.14393.0   Microsoft Corporation           
smss                                                                                                            
spoolsv                                                                                                         
sqlwriter                                                                                                       
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost                                                                                                         
svchost             10.0.14393.0 (rs1_release.160715-1616)            10.0.14393.0   Microsoft Corporation      
System                                                                                                          
taskhostw           10.0.14393.0 (rs1_release.160715-1616)            10.0.14393.0   Microsoft Corporation      
ToolbarUpdater                                                                                                  
wininit                                                                                                         
winlogon                                                                                                        
WtuSystemSupport                                                                                                
WUDFHost                                                                                                        

        ------------ END PROCESS LIST ------------

Users and Groups:

When I call getUsersAndGroups before getRunningProcesses the output of getUsersAndGroups is injected in getRunningProcesses and worse, no running processes are listed at all, but rather a lot of blank lines.

How can I separate or control the output of getUsersAndGroups so that it outputs before the output of getRunningProcesses?

The output of the injected output looks like this:

Running Processes:
        ------------ START PROCESS LIST ------------

Username       Group                                                      
--------       -----                                                      
Administrator  Administrators                                             
debug255       Administrators;Hyper-V Administrators;Performance Log Users
DefaultAccount System Managed Accounts Group                              
Guest          Guests                                                     




































































        ------------ END PROCESS LIST ------------

Thank you so much for your help!


Solution

  • tl; dr:

    The underlying problem affects both Windows PowerShell and PowerShell (Core) 7+, up to at least v7.4.x (current as of this writing), and, since it is a(n unfortunate) side effect of by-design behavior, may or may not get fixed.

    To prevent output from appearing out of order, force synchronous display output, by explicitly calling Format-Table or Out-Host:[1]

    getUsersAndGroups | Format-Table
    getRunningProcesses | Format-Table
    

    Both Format-Table and Out-Host fix what is primarily a display problem, but they are suboptimal solutions in that they both interfere with providing the output as data:

    Relevant GitHub issues:


    Background information:

    Inside a PowerShell session:

    From the outside, when calling the PowerShell CLI (powershell -file ... or powershell -command ...):

    Note: All of the above equally applies to PowerShell (Core) 7+ and its pwsh CLI, up to at least v7.4.x.


    The explanation of PowerShell's problematic behavior in this case:

    It may helpful to demonstrate the problem with an MCVE (Minimal, Complete, and Verifiable Example):

    Write-Host "-- before"
    [pscustomobject] @{ one = 1; two = 2; three = 3 }
    Write-Host "-- after"
    

    In PSv5+, this yields:

    -- before
    
    -- after
    one two three
    --- --- -----
      1   2     3
    

    What happened?

    This helpful answer explains why that happens; in short:

    The problematic behavior is discussed in GitHub issue #4594; while there's still hope for a solution, there has been no activity in a long time.


    Note: This answer originally incorrectly "blamed" the PSv5+ 300 msec. delay for potentially surprising standard output formatting behavior (namely that the first object sent to a pipeline determines the display format for all objects in the pipeline, if table formatting is applied - see this answer).


    [1] Since the problem only occurs with direct output that is implicitly table-formatted, using Out-Host (which uses the same implicit formatting) has the same (display) effect as Format-Table in this case.

    [2] The CLI allows you to request output in a structured text format, namely the XML-based serialization format known as CLIXML, with -OutputFormat Xml. PowerShell uses this format behind the scenes for serializing data across processes, and it is not usually known to outside programs, which is why -OutputFormat Xml is rarely used in practice. Note that when you do use it, the Format-Table / Out-Host workarounds would again not be effective, given that the original output objects are lost.