Powershell: resolve path that might not exist?

Question

I'm trying to process a list of files that may or may not be up to date and may or may not yet exist. In doing so, I need to resolve the full path of an item, even though the item may be specified with relative paths. However, Resolve-Path prints and error when used with a non-existant file.

For example, What's the simplest, cleanest way to resolve ".\newdir\newfile.txt" to "C:\Current\Working\Directory\newdir\newfile.txt" in Powershell?

Note that System.IO.Path's static method use with the process's working directory - which isn't the powershell current location.

Answer 1

You want:

c:\path\exists\> $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath(".\nonexist\foo.txt") 

returns:

c:\path\exists\nonexists\foo.txt 

This has the advantage of working with PSPaths, not native filesystem paths. A PSPath may not map 1-1 to a filesystem path, for example if you mount a psdrive with a multi-letter drive name.

What's a pspath?

ps c:\> new-psdrive temp filesystem c:\temp ... ps c:\> cd temp: ps temp:\>  

temp:\ is a drive-qualified pspath that maps to a win32 (native) path of c:\temp.

-Oisin

Answer 2

When Resolve-Path fails due to the file not existing, the fully resolved path is accessible from the thrown error object.

You can use a function like the following to fix Resolve-Path and make it work like you expect.

function Force-Resolve-Path {     <#     .SYNOPSIS         Calls Resolve-Path but works for files that don't exist.     .REMARKS         From http://devhawk.net/blog/2010/1/22/fixing-powershells-busted-resolve-path-cmdlet     #>     param (         [string] $FileName     )      $FileName = Resolve-Path $FileName -ErrorAction SilentlyContinue `                                        -ErrorVariable _frperror     if (-not($FileName)) {         $FileName = $_frperror[0].TargetObject     }      return $FileName }