当我使用环境变量时，为什么Test-Path cmdlet错误地报告false? [英] Why does Test-Path cmdlet incorrectly report false when I use an environment variable?
问题描述
我在使用Powershell 4.0的Win 7计算机上
I'm on a Win 7 machine using Powershell 4.0
PS C:\> $psversiontable
Name Value
---- -----
PSVersion 4.0
WSManStackVersion 3.0
SerializationVersion 1.1.0.1
CLRVersion 4.0.30319.42000
BuildVersion 6.3.9600.18728
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0}
PSRemotingProtocolVersion 2.2
请参阅下面的命令行练习.该dll存在.环境变量存在并且具有正确的路径.当我将环境变量与Test-Path一起使用时，它错误地报告了$false.当我在Test-Path中使用字符串文字时，它会正确报告$true
See command line exercise below. The dll exists. The environment variable exists and has the correct path. When I use the the environment variable with Test-Path, it incorrectly reports $false. When I use a string literal with Test-Path, it correctly reports $true
为什么使用环境变量时Test-Path错误地报告false?
Why does Test-Path incorrectly report false when I use the environment variable?
PS C:\> dir "C:\Program Files (x86)\Gemalto\NET Smartcard Framework SDK\v2.3.0\bin\SmartCard.Runtime.dll"
Directory: C:\Program Files (x86)\Gemalto\NET Smartcard Framework SDK\v2.3.0\bin
Mode LastWriteTime Length Name
---- ------------- ------ ----
-a--- 1/13/2012 6:57 PM 131072 SmartCard.Runtime.dll
PS C:\> Write-Host $env:GEMALTO_SMARTCARD_DLL
"C:\Program Files (x86)\Gemalto\NET Smartcard Framework SDK\v2.3.0\bin\SmartCard.Runtime.dll"
PS C:\> Test-Path $env:GEMALTO_SMARTCARD_DLL
False
PS C:\> Test-Path "C:\Program Files (x86)\Gemalto\NET Smartcard Framework SDK\v2.3.0\bin\SmartCard.Runtime.dll"
True
推荐答案
在打印Write-Host $env:GEMALTO_SMARTCARD_DLL时，您可以看到环境变量GEMALTO_SMARTCARD_DLL包括文字"作为其值的一部分.那是不对的.例如，您应该先删除它们，然后再传递到Test-Path:$env:GEMALTO_SMARTCARD_DLL.Trim('"').
As you print Write-Host $env:GEMALTO_SMARTCARD_DLL, then you can see that environment variable GEMALTO_SMARTCARD_DLL includes literal " as part of its value. That is incorrect. You should remove them before passing to Test-Path: $env:GEMALTO_SMARTCARD_DLL.Trim('"'), for example.
注意:尽管"对于文件系统路径是无效字符，但对于PowerShell路径也不是无效字符，因为它不仅限于文件系统.
Note: although " is invalid character for file system path, it is not invalid character for PowerShell path, as it is not limited for file system only.
New-PSDrive -Name '"C' -PSProvider Variable -Root \
${Program Files (x86)\Gemalto\NET Smartcard Framework SDK\v2.3.0\bin\SmartCard.Runtime.dll"} = 'Value'
Test-Path $env:GEMALTO_SMARTCARD_DLL
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