Passing arguments with the Start-Process cmdlet

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Steps to reproduce

I am experiencing issues running external programs with the Start-Process cmdlet.

For example I think the following two commands should produce the same output but they do not:

PS> pwsh -Command 'Write-Host "`"Hello World!`""'
"Hello World!"

PS> Start-Process -FilePath 'pwsh' -ArgumentList @('-Command', 'Write-Host "`"Hello World!`""') -Wait -NoNewWindow
Hello World!`

There seems to be an issue with how parameters in the ArgumentList are passed to the external program.

Expected behavior

PS> Start-Process -FilePath 'pwsh' -ArgumentList @('-Command', 'Write-Host "`"Hello World!`""') -Wait -NoNewWindow
"Hello World!"

Actual behavior

PS> Start-Process -FilePath 'pwsh' -ArgumentList @('-Command', 'Write-Host "`"Hello World!`""') -Wait -NoNewWindow
Hello World!`

Error details

No response

Environment data

PS> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.3.1
PSEdition                      Core
GitCommitId                    7.3.1
OS                             Microsoft Windows 10.0.19045
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visuals

No response

[mklement0]

Glad to hear it helped, @lclutz.

Yes, I think it’s fine to close it, and perhaps someone from the team, perhaps @iSazonov, can tag it as a duplicate.

Your issue did highlight an aspect that #5576 doesn’t explicitly mention yet, however:

• When the original problem gets fixed, hopefully by introducing a new -ArgumentArray (-arga) parameter, as proposed here, that parameter should perform the same automatic escaping that direct invocation does in 7.3.+ - that is, not only do values with spaces need to be enclosed in "..." on the process command line, embedded " must also be automatically escaped as \"

• By contrast, the old behavior for -ArgumentList (-args) must remain in effect for backward compatibility (with an alias of -ArgumentString), which is then best used with a single -ArgumentList value encoding all arguments, which means the user must construct the raw process command line themselves, i.e. with explicit embedded " chars. and \-escaping.

  • Applied to your case, using a single string:

# Note: With #5576 fixed as proposed, -ArgumentString could be used in lieu of -ArgumentList
Start-Process -FilePath 'pwsh' -ArgumentList '-Command Write-Host "`\"Hello World!`\""' -Wait -NoNewWindow

[mklement0]

Yes, unlike the Windows PowerShell CLI, powershell.exe, the PowerShell Core CLI, pwsh.exe, now also supports "" as an escaped " on the command line, as an alternative to \" (the latter is usually preferable, because it is more universally recognized, and it is also what PowerShell itself uses when performing the escaping automatically in direct calls).

The point is the same, however: with Start-Process, you must perform the escaping yourself.