powershell - 重定向到 'NUL' 失败 : FileStream will not open Win32 devices

Question

我试图从 choco install 中删除一些冗长的内容AppVeyor 中的命令。这是我一直在尝试的(如建议的 here ):

if (Test-Path "C:/ProgramData/chocolatey/bin/swig.exe") {
    echo "using swig from cache"
} else {
    choco install swig > NUL
}

但是它失败了:

Redirection to 'NUL' failed: FileStream will not open Win32 devices such as
disk partitions and tape drives. Avoid use of "\\.\" in the path.
At line:4 char:5
+     choco install swig > NUL
+     ~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : RedirectionFailed

Command executed with exception: Redirection to 'NUL' failed: FileStream will not open Win32 devices such as disk partitions and tape drives. Avoid use of "\\.\" in the path.

所以我的问题是有没有办法抑制 choco install 的冗长AppVeyor 上 PowerShell 中的命令？

Answer 1

nul是批处理语法。在 PowerShell 中，您可以使用 $null相反，正如 Mathias R. Jessen 在评论中指出的那样:

choco install swig > $null

其他选项是管道进入 Out-Null cmdlet，将输出收集到变量中，或将其强制转换为 void :

choco install swig | Out-Null
$dummy = choco install swig
[void](choco install swig)