Passing arguments to job initialization script - powershell

Question

I have multiple jobs and for every job I want to have the same initialization script that sets some things up. I'd like to pass some arguments to the initialization script, but unfortunately the arguments passed using -ArgumentList seem to be only accessible in the actual job script.
Here's an example that demonstrates the argument only being accessible in the actual script:
function StartJob([ScriptBlock] $script, [string] $name, [ScriptBlock] $initialization_script = $null, $argument = $null)
{
Start-Job -ScriptBlock $script -Name $name -InitializationScript $initialization_script -ArgumentList $argument | Out-Null
}
[ScriptBlock] $initialization_script =
{
# The argument given to StartJob should be accessible here
param($test)
echo "Test: $test"
}
[ScriptBlock] $actual_script =
{
param($test)
echo "Test: $test"
}
StartJob $actual_script "Test job" $initialization_script "Have this string in the `$initialization_script"
#(Get-Job).ForEach({
# Wait for the job to finish, remove it and output its results
Write-Host "$($_.Name) results:"
Receive-Job -Job $_ -Wait -AutoRemoveJob | Write-Host
})
How would I be able to be access the arguments passed in the $initialization_script?

Answer 1

AFAIK it's not possible to pass parameters to initialization scripts. Init scripts are designed to be reusable scripblocks to load known resources. If something can't be defined once, then it's unique to that job's scriptblock and doesn't belong in a init. script. You have a few alternatives:
If you have a module (.psm1 and maybe a .psd1), then place it in one of the module-folders (see $env:PSModulePath for paths) so you could simply write Import-Module MyImportantModule in your initialization script.
If you can't use the solution above, I would add a paramter to the actual script and pass in the path as a regular argument.
[ScriptBlock] $actual_script =
{
# The argument given to StartJob should be accessible here
param($test, $ModulePath)
#Import-Module $ModulePath
echo "Test: $test"
}
Start-Job -ScriptBlock $actual_script -Name "Test job" -ArgumentList "First argument", "c:\mymodule.ps1"
Or you could generate the initialization scriptblock in your script so it's dynamic:
$ModulePath = "c:\mymodule.ps1"
$init = #"
#Import-Module "$ModulePath"
#Something-Else
"#
$initsb = [scriptblock]::Create($init)