Process files dragged to BAT file in PowerShell - powershell

Question

I trying to create a script that will convert Markdown files that are dropped on a processing script.
To accomplish this, I created a (process.bat) that would pass the names of the dropped files to a PowerShell script:
powershell.exe -NoProfile -File "./process.ps1" -Document %*
#pause
The PowerShell file (process.ps1) would process each file individually:
[parameter(Mandatory=$true)]
[String[]]$Document
Write-Host $args[1]
$Document | ForEach-Object {
Write-Host "Document: $_"
# convert Markdown to Html
pandoc -o ($_ -Replace '.md', '.html') -f markdown -t html $_
}
When I drop two files on the batch file:
C:\Users\XXX\Documents\WindowsPowerShell\Scripts\Markdown>powershell.exe -NoProfile -File "./process.ps1" -Document "C:\Users\XXX\Documents\WindowsPowerShell\Scripts\Markdown\FOO.md"
"C:\Users\XXX\Documents\WindowsPowerShell\Scripts\Markdown\BAR.md"
C:\Users\XXX\Documents\WindowsPowerShell\Scripts\Markdown\BAR.md
Document:
Press any key to continue . . .
The documents are not being processed.
What's the recommended approach to passing the batch file's file list %* to PowerShell?

Answer 1

When powershell.exe, the PowerShell CLI, is called from the outside with the -File parameter, it doesn't support arrays - only individual arguments.[1]
(Additionally, you neglected to wrap your parameter definition in a param(...) block, which effectively caused it be ignored.)
The simplest solution is to define your parameter with the ValueFromRemainingArguments option so that it automatically collects all positional arguments in the parameter variable:
param(
[Parameter(Mandatory, ValueFromRemainingArguments)]
[String[]] $Document
)
Then invoke your script via the PowerShell CLI without -Document:
powershell.exe -NoProfile -File "./process.ps1" %*
As an alternative to using a helper batch file, you can:
define a shortcut file (*.lnk) that explicitly invokes your PowerShell script as powershell.exe -File \path\to\your\script.ps1 (without additional arguments)
and then use that as the drop target.
Note: The reason that you cannot use a PowerShell script (*.ps1) directly as a drop target is that PowerShell script files aren't directly executable - instead, opening (double-clicking) a *.ps1 file opens it for editing.
You'd then need to add pause (or something similar, such as Read-Host -Prompt 'Press Enter to exit.') to your PowerShell script, to prevent it from closing the window instantly on finishing.
Alternatively, leave the script as-is and use -NoExit (placed before -File) to keep the PowerShell session open.
[1] The same applies to the PowerShell Core CLI, pwsh.