How to handle file paths with special characters?

Question

I\'ve got a PowerShell script that needs to be able to call another PS script from within the same directory with elevated credentials. Because the scripts need to be porta

Answer 1

As an aside: In PSv3+ you can use $PSScriptRoot to refer to the directory in which the script is located.
If you can modify the target script, you can place Set-Location -LiteralPath $PSScriptRoot at the top to change to that folder.

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To avoid quoting/escaping problems, pass arguments individually, as distinct elements of an array to -ArgumentList (-Args):

Start-Process powershell -Verb runas -ArgumentList '-ExecutionPolicy', 'Bypass', 
  '-File', "`"$dir\elevated.ps1`"", "`"$dir`""

Unfortunately, that alone is not enough:

• When you use -File, even though the arguments are passed individually, the script file path and the directory path still require embedded "..." quoting in order to pass values with embedded spaces correctly: "`"..."`" passes a value with embedded double-quoting (` is PowerShell's escape character, so `" escapes a double quote).^{Tip of the hat to Ansgar Wiechers.}
  This bug has been reported on GitHub.

  • ^{In case you ever need to pass an argument with embedded " characters (which filesystem paths by definition never contain), use something like:
    ('"{0}"' -f ($value -replace '"', '\"'))}

• Sadly, even that is not enough if your path contains [ characters that aren't each part of a syntactically valid wildcard-pattern range (e.g., [ab], [0-9]), because PowerShell - as of Windows PowerShell v5.1 / PowerShell Core v6.0.0-beta.6 - mistakenly interprets the path as a wildcard pattern and fails if it finds it malformed - see this GitHub issue.

  • In other words: your invocation may or may not work, depending on how [ and possibly ] are used in your path; e.g. foo[1] works, but foo[] doesn't.
  • There is currently no workaround that works in all cases.

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Alternative with -Command:

-Commmand allows you to pass a piece of PowerShell code - a mini-script, if you will - which you can use to pass a single, quoted string that is parsed by PowerShell rules by the new instance:

Start-Process powershell -Verb runas -ArgumentList '-ExecutionPolicy', 'Bypass', 
  '-Command', "& `"$dir\elevated.ps1`" `"$dir`""

Note the need to use & to invoke the script, because it is given as a quoted string, and that the expansion of $dir is performed by the current session.

Unfortunately, the problem with filenames that happen to look like malformed wildcard patterns (discussed above) applies to this invocation scenario too.

Answer 2

So, I was able to figure out a solution that works as long as the brackets aren't empty [].

Here's what I've got:

Start-Process Powershell -Verb runas -ArgumentList "-ExecutionPolicy","Bypass","-File","`"$(Get-Item -LiteralPath $PSScriptRoot\elevated.ps1)`""

Using this as the test path:

C:\Users\Administrator\Desktop\Test Folder\badname-!@#$%^_+-=.,{}`~[&]()

A path with empty brackets [] still doesn't work, but doesn't return an error. I'm assuming this means that it wasn't able to find a file in the expected path while interpreting the brackets as a wildcard still. Not sure if there's really anything that will fix that except maybe checking the path before running and throwing an error.