Pass arguments to a scriptblock in powershell

Question

I guess you can't just do this:

  $servicePath = $args[0]

  if(Test-Path -path $servicePath) <-- does not throw in here

  $block = {

        write-host $servicePath -foreground "magenta"

        if((Test-Path -path $servicePath)) { <-- throws here.

              dowork 
        }
  }

So how can I pass my variables to the scriptblock $block?

Answer 1

Keith's answer also works for Invoke-Command, with the limit that you can't use named parameters. The arguments should be set using the -ArgumentList parameter and should be comma separated.

$sb = {param($p1,$p2) $OFS=','; "p1 is $p1, p2 is $p2, rest of args: $args"}
Invoke-Command $sb -ArgumentList 1,2,3,4

Also see here and here.

Answer 2

A scriptblock is just an anonymous function. You can use $args inside the scriptblock as well as declare a param block, for example

$sb = {
  param($p1, $p2)
  $OFS = ','
  "p1 is $p1, p2 is $p2, rest of args: $args"
}
& $sb 1 2 3 4
& $sb -p2 2 -p1 1 3 4

Answer 3

BTW, if using the script block to run in a separate thread (multi threaded):

$ScriptBlock = {
    param($AAA,$BBB) 
    return "AAA is $($AAA) and BBB is $($BBB)"
}

$AAA = "AAA"
$BBB = "BBB1234"    
$null = Start-Job $ScriptBlock -ArgumentList $AAA,$BBB

then yields:

$null = Start-Job $ScriptBlock -ArgumentList $AAA,$BBB    
Get-Job | Receive-Job
AAA is AAA and BBB is BBB1234

Answer 4

I know this article is a bit dated, but I wanted to throw this out as a possible alternative. Just a slight variation of the previous answers.

$foo = {
    param($arg)

    Write-Host "Hello $arg from Foo ScriptBlock" -ForegroundColor Yellow
}

$foo2 = {
    param($arg)

    Write-Host "Hello $arg from Foo2 ScriptBlock" -ForegroundColor Red
}


function Run-Foo([ScriptBlock] $cb, $fooArg){

    #fake getting the args to pass into callback... or it could be passed in...
    if(-not $fooArg) {
        $fooArg = "World" 
    }
    #invoke the callback function
    $cb.Invoke($fooArg);

    #rest of function code....
}

Clear-Host

Run-Foo -cb $foo 
Run-Foo -cb $foo 

Run-Foo -cb $foo2
Run-Foo -cb $foo2 -fooArg "Tim"

Answer 5

By default PowerShell won't capture variables for a ScriptBlock. You can explicitly capture by calling GetNewClosure() on it, however:

$servicePath = $args[0]

if(Test-Path -path $servicePath) <-- does not throw in here

$block = {

    write-host $servicePath -foreground "magenta"

    if((Test-Path -path $servicePath)) { <-- no longer throws here.

          dowork 
    }
}.GetNewClosure() <-- this makes it work