Passing named parameters from one powershell script to another

Question

I have a situation in which I have script_1.ps1 that gets called directly by a user. Script_1.ps1 is really just an entry point (at minimum providing just a hard coded config value) to script_2.ps1, which contains shared, factored out logic. I want the user to be able to pass any or all required arguments to script_1, which in turn must pass to script_2. If not all the required parameters are passed by the user, there's logic in script_2 that will prompt the user for the information.

In my ideal setup, I'd have script_1 accept named parameters from the user, and then script_2 accept the named parameters from script_1. For example, my script_1.ps1 would look something like this:

param (
    [switch] $Help = $false,
    [switch] $Quiet,
    [string] $Param1,
    [string] $Param2,
    [Parameter(Position=0, ValueFromRemainingArguments=$true)] $args
)

if (!$Help) {
    .\script_2.ps1 -ServiceName "Service name here" #also pass any other args that were set by user (may be none, several, or all)
}

Then my script_2.ps1 would look something like this:

param (    
    [switch] $Quiet,
    [Alias("l")]
    [string] $ServiceName,
    [string] $Param1,
    [string] $Param2,
    [Parameter(Position=0, ValueFromRemainingArguments=$true)] $args
)

# do things with arguments here

Is it possible to achieve this without enumerating all arguments when I call script_2.ps1 from script_1.ps1? My script_1 has about 20 different possible parameters, so something like this would get messy pretty fast:

.\script_2.ps1 -ServiceName "Service name here" -Quiet $Quiet -Param1 $Param1 -Param2 $Param2

The closest I've gotten to making this work is with the following, but then it cuts off arguments with spaces by the time they get to script_2. Putting escaped quotes around $args results in no arguments getting passed.

param (
    [switch] $Help = $false,
    [Parameter(Position=0, ValueFromRemainingArguments=$true)] $args
)

if (!$Help) {
    Start-Process -FilePath powershell.exe -ArgumentList "-file `".\script_2.ps1`" -ServiceName `"Service name here`" $args"
}

I'm sure I'm missing a trick to do this as a relative newcomer to powershell... TIA for any help!

You can have the first script output an custom object with properties that match some of your second script parameter names. Then in the second script, use the valuefrompipelinebypropertyname parameter attribute. — AdminOfThings
– AdminOfThings, Commented Nov 4, 2019 at 21:31
[1] the $args variable is an automatic $Var. you ought not to use it as a parameter name. [2] have you looked at $PSBoundParamters yet? — Lee_Dailey
– Lee_Dailey, Commented Nov 4, 2019 at 21:39
@Lee_Dailey $PSBoundParameters is exactly what I was after! Really surprised that didn't come up when I was googling around this problem. Thanks a bunch — allison
– allison, Commented Nov 4, 2019 at 22:15
@allison - you are most welcome! glad to have helped a bit ... [grin] — Lee_Dailey
– Lee_Dailey, Commented Nov 4, 2019 at 23:33

mclayton · Accepted Answer · 2019-11-04 22:33:38Z

You can use splatting to pass the collection of parameters from the first script into the second script. All this means is that instead of writing out the parameters to script2.ps1 longhand, you pass in a hashtable of key-value pairs.

Fortunately, there's a built-in hashtable which already contains the parameters passed in to a script or a function - $PSBoundParameters - so you can just splat that straight down from script1.ps1 into script2.ps1...

Note that you invoke a "splat" with the @ symbol, not $ - i.e. @PSBoundParameters in this case.

script.ps1

param (
    [switch] $Help = $false,
    [switch] $Quiet,
    [string] $Param1,
    [string] $Param2,
    [Parameter(Position=0, ValueFromRemainingArguments=$true)] $args
)

if (!$Help) {
    write-host "script1.ps1"
    write-host ($PSBoundParameters | ft | out-string);
    . .\script2.ps1 @PSBoundParameters
}

script2.ps1

param (    
    [switch] $Quiet,
    [Alias("l")]
    [string] $ServiceName,
    [string] $Param1,
    [string] $Param2,
    [Parameter(Position=0, ValueFromRemainingArguments=$true)] $args
)

# do things with arguments here
write-host "script2.ps1"
write-host ($PSBoundParameters | ft * | out-string)

If you then call:

C:\> powershell .\script1.ps1 -Param1 "aaa" -Quiet:$true

you get this output:

script1.ps1

Key    Value
---    -----
Param1 aaa
Quiet  True

script2.ps1

Key    Value
---    -----
Param1 aaa
Quiet  True

and if you don't like the built-in $PSBoundParameters hashtable, you can build your own and splat that instead:

$mySplat = @{
    "Quiet" = $true
    "Param1" = "myParam1"
}
$mySplat.Add("Param2", "myParam2")
$mySplat.Remove("Quiet");
. .\script2.ps1 @mySplat

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