powershell：错误的符号 link 分辨率

Question

我想我在 PS 中发现了一个错误。

我创建了一个新的替代盘符：

C:\> subst k: c:\test
C:\> subst
K:\: => c:\test

但 PS 告诉：

PS C:\> get-item 'K:\' | Format-list | Out-String

Directory:
Name           : K:\
Mode           : d-----
LinkType       :
Target         : {K:\test}

如您所见，target中的盘符是错误的。怎么来的？

我的windows版本：

Windows 10 Enterprise
Version 1809
OS Build 17763.1457

我的PS版本：

PS C:\> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      5.1.17763.1432
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17763.1432
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

如何使用 ps 获得正确的目标？

非常感谢

Answer 1

我同意这是一个错误，但是：

无符号link或其他NTFS重解析点（例如junction) 涉及您的代码。
因此，.Target 属性 - 报告 重新分析点 的目标 - 甚至不应该是填写;这是实际的错误，它在 PowerShell [Core] v6+.
中不再存在

因此，为了清除此类错误的 .Target 值，您可以按文件的 .LinkType 属性过滤文件：

Get-ChildItem | Where-Object LinkType -eq SymbolicLink # now, .Targets are valid

另外，如果您正在寻找一种方法来将基于替代驱动器的路径转换为其基础物理路径：

不幸的是，Convert-Path nor Get-PSDrive 似乎都没有意识到 替代的 驱动器（使用 subst.exe 创建） -甚至在 PowerShell 7.0 中也不行 - 所以你必须 滚动你自己的翻译命令:

& {
  $fullName = Convert-Path -LiteralPath $args[0]
  $drive = Split-Path -Qualifier $fullName
  if ($drive.Length -eq 2 -and ($substDef = @(subst.exe) -match "^$drive")) {
    Join-Path ($substDef -split ' ', 3)[-1] $fullName.Substring($drive.Length)
  } else {
    $fullName
  }
} 'K:\'

以上应该 return C:\test\ 你的情况。

注意：由于使用了Convert-Path，以上仅适用于现有路径；让它支持不存在的路径需要更多的工作（见下文）。
请注意，长期存在的 GitHub feature request #2993 要求增强 Convert-Path 以处理不存在的路径。

在此期间，这里有高级功能Convert-PathEx来填补空白。

定义后，您可以改为执行以下操作：

PS> Convert-PathEx K:\
C:\test\

function Convert-PathEx {
  <#
.SYNOPSIS
Converts file-system paths to absolute, native paths.

.DESCRIPTION
An enhanced version of Convert-Path, which, however only supports *literal* paths.
For wildcard expansion, pipe from Get-ChildItem or Get-Item.

The enhancements are:

* Support for non-existent paths.
* On Windows, support for translating paths based on substituted drives
  (created with subst.exe) to physical paths.

#>
  [CmdletBinding(PositionalBinding = $false)]
  param(
    [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline, ValueFromPipelineByPropertyName)]
    [Alias('PSPath', 'LP')]
    [string[]] $LiteralPath
  )

  begin {

    $isWin = $env:OS -eq 'Windows_NT'

    # Helper function for ignoring .Substring() exceptions.
    function fromPos ($str, $ndx) {
      try { return $str.Substring($ndx) } catch { return '' }
    }

  }

  process {

    foreach ($path in $LiteralPath) {

      $path = $path -replace '^.+::' # strip any PS provider prefix, such as 'FileSystem::' or 'Microsoft.PowerShell.Core\FileSystem::'

      # Analyze drive information.
      $driveSpec = Split-Path -ErrorAction Ignore -Qualifier $path
      $driveObj = if ($driveSpec) { (Get-PSDrive -ErrorAction Ignore -PSProvider FileSystem -Name $driveSpec.Substring(0, $driveSpec.Length - 1)) | Select-Object -First 1 } # !! Get-PSDrive can report *case-sensitive variations* of the same drive, so we ensure we only get *one* object back.
      if ($driveSpec -and -not $driveObj) {
        Write-Error "Path has unknown file-system drive: $path" -Category InvalidArgument
        continue
      }

      $rest = if ($driveObj) { fromPos $path $driveSpec.Length } else { $path }
      $startsFromRoot = $rest -match '^[\/]'
      if ($startsFromRoot) { $rest = fromPos $rest 1 } # Strip the initial separator, so that [IO.Path]::Combine() works correctly (with an initial "\" or "/", it ignores attempts to prepend a drive).
      $isAbsolute = $startsFromRoot -and ($driveObj -or -not $isWin) # /... paths on Unix are absolute paths.

      $fullName =
      if ($isAbsolute) {
        if ($driveObj) {
          # Prepend the path underlying the drive.
          [IO.Path]::Combine($driveObj.Root, $rest)
        } else {
          # Unix: Already a full, native path - pass it through.
          $path
        }
      } else {
        # Non-absolute path, which can have one three forms:
        #  relative: "foo", "./foo"
        #  drive-qualified relative (rare): "c:foo"
        #  Windows drive-qualified relative (rare): "c:foo"
        if ($startsFromRoot) {
          [IO.Path]::Combine($PWD.Drive.Root, $rest)
        } elseif ($driveObj) {
          # drive-qualified relative path: prepend the current dir *on the targeted drive*.
          # Note: .CurrentLocation is the location relative to the drive root, *wihtout* an initial "\" or "/"
          [IO.Path]::Combine($driveObj.Root, $driveObj.CurrentLocation, $rest)
        } else {
          # relative path, prepend the provider-native $PWD path.
          [IO.Path]::Combine($PWD.ProviderPath, $rest)
        }
      }

      # On Windows: Also check if the path is defined in terms of a
      #             *substituted* drive (created with `subst.exe`) and translate
      #             it to the underlying path.
      if ($isWin) {
        # Note: [IO.Path]::GetPathRoot() only works with single-letter drives, which is all we're interested in here.
        #       Also, it *includes a trailing separator*, so skipping the length of $diveSpec.Length works correctly with [IO.Path]::Combine().
        $driveSpec = [IO.Path]::GetPathRoot($fullName)
        if ($driveSpec -and ($substDef = @(subst.exe) -like "$driveSpec*")) {
          $fullName = [IO.Path]::Combine(($substDef -split ' ', 3)[-1], (fromPos $fullName $driveSpec.Length))
        }
      }

      # Finally, now that we have a native path, we can use [IO.Path]::GetFullPath() in order
      # to *normalize*  paths with components such as "./" and ".."
      [IO.Path]::GetFullPath($fullName)

    } # foreach

  }

}

powershell：错误的符号 link 分辨率

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