Powershell: passing parameters to functions stored in variables

Question

I'm trying to get a simple working example of using functions inside of jobs. I've managed to pass my function into the scriptblock used for my job, but I can't seem to get parameters to the function.

# concurrency
$Logx = 
{
    param(
    [parameter(ValueFromPipeline=$true)]
    $msg
    )    
    Write-Host ("OUT:"+$msg)
}

# Execution starts here
cls
$colors = @("red","blue","green")
$colors | %{
    $scriptBlock = 
    {   
        Invoke-Expression -Command $args[1]
        Start-Sleep 3        
    } 

    Write-Host "Processing: " $_
    Start-Job -scriptblock $scriptBlock -args $_, $Logx
}

Get-Job

while(Get-Job -State "Running")
{
    write-host "Running..."
    Start-Sleep 2
}

# Output
Get-Job | Receive-Job

# Cleanup jobs
Remove-Job * 

Here's the output:

Processing:  red

Id              Name            State      HasMoreData     Location             Command  
--              ----            -----      -----------     --------             -------  
175             Job175          Running    True            localhost               ...   
Processing:  blue
177             Job177          Running    True            localhost               ...   
Processing:  green
179             Job179          Running    True            localhost               ...   
179             Job179          Running    True            localhost               ...   
177             Job177          Running    True            localhost               ...   
175             Job175          Running    True            localhost               ...   
Running...
Running...
OUT:
OUT:
OUT:

So as evidenced by the OUT: x3 in the output my function is getting called, but I haven't found any syntax that allows me to get the parameter to the function. Thoughts?

EDIT:

Note in Shawn's observation below and my response I tried using functions as variables because using a traditional function does not seem to work. If there is a way to get that working I'd be more than happy to not have to pass my functions around as variables.

Answer 1

The answer is to use the initializationscript parameter of Start-Job. If you define all your functions in a block and pass the block they become available.

Solution was found in this post:

How do I Start a job of a function i just defined?

Here is my example from before, now working:

# concurrency
$func = {
    function Logx 
    {
        param(
        [parameter(ValueFromPipeline=$true)]
        $msg
        )    
        Write-Host ("OUT:"+$msg)
    }
}

# Execution starts here
cls
$colors = @("red","blue","green")
$colors | %{
    $scriptBlock = 
    {   
        Logx $args[0]
        Start-Sleep 9        
    } 

    Write-Host "Processing: " $_
    Start-Job -InitializationScript $func -scriptblock $scriptBlock -args $_
}

Get-Job

while(Get-Job -State "Running")
{
    write-host "Running..."
    Start-Sleep 2
}

# Output
Get-Job | Receive-Job

# Cleanup jobs
Remove-Job * 

Answer 2

If you do not prefix your function name with keyword function, PowerShell does not know to treat it as such. As you have written your script it is basically a variable with some special text in it. Which as your output shows it is only executing the commands it recognizes within that variable's content: Write-Host "OUT:".

Using the correct syntax will tell PowerShell it is a function and that you have variables to pass into it that you need executed:

function Logx
{
    param(
    [parameter(ValueFromPipeline=$true)]
    $msg
    )    
    Write-Host ("OUT:"+$msg)
}

Then when you call it within your script you will just use Logx

Answer 3

Got this far. Have to run out, will try back later. PS: What is getting passed at args[1], I am getting a lot of red,

 CategoryInfo          : InvalidData: (:) [Invoke-Expression], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Microsoft.PowerShell.Commands.InvokeExpressionCommand

here is what I've managed so far.

# concurrency
$Logx =
{
    param(
    [parameter(ValueFromPipeline=$true)]
    $msg
    )    
    Write-Host ("OUT:"+$msg)
}

# Execution starts here
cls
$colors = @("red","blue","green")
$colors | %{
    & $scriptBlock = 
    {   Invoke-Expression -Command $args[1]
        Start-Sleep 3  
    } 

    Write-Host "Processing: " $_
    Start-Job -scriptblock $scriptBlock -ArgumentList @($_, $Logx)
}

# Get-Job

while(Get-Job -State "Running")
{
    write-host "Running..."
    Start-Sleep 2
}

# Output
Get-Job | Receive-Job

# Cleanup jobs
Remove-Job *