[PowerShell每日技巧]测试UNC路径(20140402)

DAIC

Test-Path can test whether or not a given file or folder exists. This works fine for paths that use a drive letter, but can fail with pure UNC paths.

At its simplest, this should return $true, and it does (provided you did not disable your administrative shares):

$path = '\\127.0.0.1\c$$'

Test-Path -Path $path

Now, the very same code can also return $false:

1. Set-Location -Path HKCU:\
   
2. $path = '\\127.0.0.1\c$'
   
3. 
   
4. Test-Path -Path $path

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If a path does not use a drive letter, PowerShell falls back to the current path, and if that path happens to point to a non-file system location, Test-Path interprets the UNC path in the context of that provider. Since there is no such path in your Registry, Test-Path returns $false.

To make Test-Path work reliably with UNC paths, make sure you prepend the UNC path with the FileSystem provider. Now, the result is valid regardless of current drive location:

1. Set-Location -Path HKCU:\
   
2. $path = 'filesystem::\\127.0.0.1\c$'
   
3. 
   
4. Test-Path -Path $path

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http://powershell.com/cs/blogs/tips/archive/2014/04/02/testing-unc-paths.aspx