How to pass a string array to powershell through vbscript?

Question

I'm trying to pass a string array to powershell through vbscript. I got the params in the file.ps1 script:

param (
    [string[]]$target
)

I'm trying to call file.ps1 through vbscript.

I want $target = @('c:\dev','d:\lib') to be passed in.

I currently have in my vbscript :-

target1 = """c:\dev"", ""d:\lib"""
Set objShell = CreateObject("Wscript.Shell") 
objShell.run("powershell.exe -noexit -ExecutionPolicy Unrestricted -file .\file.ps1 -target1 """ & target & """")

which returns: c:\dev, d:\lib and which isn't the powershell string array format "c:\dev", "d:\lib"

Update - Thanks mklement0 and alex-dl for your answers!

Remove the "" on each side - otherwise you're passing the literal string value "c:\dev, d:\lib" — Mathias R. Jessen
– Mathias R. Jessen, Commented Feb 5, 2021 at 12:37
removing "" would cause a syntax error. In vbscript " is used as the escape character. so if i was to print """c:\dev"", ""d:\lib""" into vb console it would return "c:\dev", "d:\lib" — Mango99
– Mango99, Commented Feb 5, 2021 at 12:43
No it would not, "... -target " & target & "" is a perfectly valid expression — Mathias R. Jessen
– Mathias R. Jessen, Commented Feb 5, 2021 at 15:03
@Mathias, true, though the & "" is then unnecessary. The fundamental problem here, however, is the use of the -File CLI parameter, which fundamentally doesn't support passing arrays; -Command (-c) must be used. — mklement0
– mklement0, Commented Feb 5, 2021 at 17:05

mklement0 · Accepted Answer · 2021-02-05 16:42:13Z

alex-dl's helpful answer contains an effective solution, as long as the array's elements don't need quoting, but let me try to break it down conceptually in more detail:

The -File parameter of PowerShell's CLI, powershell.exe (pwsh in PowerShell (Core) 7+) fundamentally does not support passing arrays to PowerShell code, because all arguments are interpreted strictly as whitespace-separated, with verbatim content.
- E.g., "c:\dev", "d:\lib" on the command line is parsed as two arguments:
  - c:\dev, (note the trailing ,, syntactic " quotes stripped)
  - d:\lib
You must use the -Command (-c) option in order to pass arrays.
- -Command fundamentally changes how the arguments are parsed:
  - All arguments are stripped of syntactic (non \"-escaped) " quotes.
  - The resulting tokens are space-concatenated to form a single string.
  - The resulting string is then interpreted as PowerShell code, i.e. as if you had submitted it from inside a PowerShell session.
- This therefore enables all of PowerShell's features, such as passing arrays with ,, '...' (single-quoting), ..., and notably also means that references to PowerShell variables (e.g. $HOME) are recognized (unlike with -File).

See this answer for more guidance on when to use -File vs. -Command (-c).

Therefore, the best approach in your case is:

target = "'c:\dev', 'd:\lib'" ' Note the embedded '...'-quoting
Set objShell = CreateObject("Wscript.Shell") 
' Note the use of -c (-command) instead of -file
objShell.Run("powershell.exe -noexit -ExecutionPolicy Unrestricted -c .\file.ps1 -target " & target)

Using embedded '...'-quoting simplifies passing the array elements in a way that PowerShell sees them as individually quoted (with the values at hand, this isn't strictly necessary, but it may be in other cases).

Doing this with embedded "..."-quoting gets unwieldy, because each embedded " must then be escaped as \"" (sic):

"" to escape the " inside the VBScript string,
and \ to ensure that \" is ultimately passed on the command line, which PowerShell requires for escaping " on the command line^[1] (whereas PowerShell-internally, it is `" or (alternatively, inside a double-quoted string) "").

target = "\""c:\dev\"", \""d:\lib\"""
Set objShell = CreateObject("Wscript.Shell") 
objShell.Run("powershell.exe -noexit -ExecutionPolicy Unrestricted -c .\file.ps1 -target " & target)

^{[1] While in Windows PowerShell you can situationally get away with "" instead of \", it can break, especially if the overall -c argument is enclosed in "...".
This problem has been fixed in PowerShell (Core) 7+, where you can now use "" and \" interchangeably.

E.g., when invoked from cmd.exe,

powershell -c " ""ab c"".length " breaks, whereas

pwsh -c " ""ab c"".length " works.}

alex-dl · Accepted Answer · 2021-02-05 14:11:24Z

1

You could use the following vbscript:

target1 = """c:\dev, d:\lib"""
Set objShell = CreateObject("Wscript.Shell") 
objShell.run("powershell.exe -Command .\file.ps1 -target " & target1)

And this powershell script:

param (
    [string[]]$target
)
foreach ($t in $target) {
    write-output $t
}
Read-Host -Prompt "Press Enter to exit"

Without -Command the argument is always interpreted as a single string.

answered Feb 5, 2021 at 14:11

alex-dl

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1 Comment

mklement0 Over a year ago

Good point about the need for -Command if arrays are to be passed. Note that the escaped embedded double quotes ("" inside """c:\dev, d:\lib""") ultimately have no effect here and PowerShell ultimately sees the array elements as unquoted (which works fine in this case); additional work is needed if the array elements need quoting individually (which Mango99 (ineffectively) attempted), such as for elements containing spaces.

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