PowerShell相当于LINQ Any()? [英] PowerShell equivalent of LINQ Any()?

问题描述

我想从存储在Subversion中的脚本位置中找到所有顶级目录.

I would like to find all directories at the top level from the location of the script that are stored in subversion.

在C#中会是这样

Directory.GetDirectories(".")
  .Where(d=>Directories.GetDirectories(d)
     .Any(x => x == "_svn" || ".svn"));

在PowerShell中查找"Any()"的等效项时遇到了一些困难，并且我不想经历调用扩展方法的尴尬.

I'm having a bit of difficulty finding the equivalent of "Any()" in PowerShell, and I don't want to go through the awkwardness of calling the extension method.

到目前为止，我已经知道了:

So far I've got this:

 Get-ChildItem | ? {$_.PsIsContainer} | Get-ChildItem -force | ? {$_.PsIsContainer -and $_.Name -eq "_svn" -or $_.Name -eq ".svn"

这找到了我自己的svn目录，而不是它们的父目录-这就是我想要的.奖励积分，如果您能告诉我为什么添加

This finds me the svn directories themselves, but not their parent directories - which is what I want. Bonus points if you can tell me why adding

 | Select-Object {$_.Directory}

该命令列表的末尾仅显示一系列空行.

to the end of that command list simply displays a sequence of blank lines.

推荐答案

使用PowerShell v3 +解决方案回答立即问题:

To answer the immediate question with a PowerShell v3+ solution:

(Get-ChildItem -Force -Directory -Recurse -Depth 2 -Include '_svn', '.svn').Parent.FullName

-Directory将匹配限制为目录，-Recurse -Depth 2递归到三个级别(子代，孙代和曾孙代)，Include允许指定多个(文件名组成部分)过滤器，而.Parent.FullName返回 parent 目录的完整路径.使用成员枚举(隐式访问集合的 elements'属性)来匹配匹配的目录.

-Directory limits the matches to directories, -Recurse -Depth 2 recurses up to three levels (children, grandchildren, and great-grandchildren), Include allows specifying multiple (filename-component) filters, and .Parent.FullName returns the full path of the parent dirs. of the matching dirs., using member enumeration (implicitly accessing a collection's elements' properties).

^{至于奖励问题:select-object {$_.Directory}不起作用， 因为 \[System.IO.DirectoryInfo\] Get-ChildItem返回的a>实例没有.Directory属性，只有.Parent属性； Select-Object -ExpandProperty Parent应该已经被使用.}

^{As for the bonus question: select-object {$_.Directory} does not work, because the \[System.IO.DirectoryInfo\] instances returned by Get-ChildItem have no .Directory property, only a .Parent property; Select-Object -ExpandProperty Parent should have been used.}

^{除了仅返回感兴趣的属性 value 外，-ExpandProperty还强制执行了该属性的存在.相比之下，假定输入对象没有.Directory属性，Select-Object {$_.Directory}返回一个自定义对象，该对象的文字名称为$_.Directory，其值为$null.这些$null值在控制台中显示为空行.}

^{In addition to only returning the property value of interest, -ExpandProperty also enforces the existence of the property. By contrast, Select-Object {$_.Directory} returns a custom object with a property literally named $_.Directory, whose value is $null, given that the input objects have no .Directory property; these $null values print as empty lines in the console.}

关于与

As for the more general question about a PowerShell equivalent to LINQ's .Any() method, which indicates [with a Boolean result] whether a given enumerable (collection) has any elements at all / any elements satisfying a given condition:

从本质上讲， PowerShell提供了 no 此类等效功能，但是可以模拟这种行为:

Natively, PowerShell offers no such equivalent, but the behavior can be emulated:

注意事项:此首先需要在内存中收集整个输入集合，这对于大型集合和/或长时间运行的输入命令可能会造成问题.

Caveat: This requires collecting the entire input collection in memory first, which can be problematic with large collections and/or long-running input commands.

(...).Where({ $_ ... }, 'First').Count -gt 0

...表示关注的命令，$_ ...表示关注的条件，应用于每个输入对象，其中PowerShell的自动$_变量引用当前的输入对象；参数'First'确保一旦找到第一个匹配项，该方法就返回.

... represents the command of interest, and $_ ... the condition of interest, applied to each input object, where PowerShell's automatic $_ variable refers to the input object at hand; argument 'First' ensures that the method returns once the first match has been found.

例如:

# See if there's at least one value > 1
PS> (1, 2, 3).Where({ $_ -gt 1 }, 'First').Count -gt 0
True

---

使用管道:测试命令是否产生了至少一个[符合条件]的输出对象:

基于管道的解决方案的优点是，它可以在正在生成的命令输出上逐个执行，而无需执行 首先将整个输出收集到内存中.

---

Using the pipeline: Testing whether a command produced at least one output object [matching a condition]:

The advantage of a pipeline-based solution is that it can act on a command's output one by one, as it is being produced, without needing to collect the entire output in memory first.

• 如果您不介意所有对象被枚举，即使您只关心是否至少有一个 -使用 Paolo Tedesco的有用扩展来

• If you don't mind that all objects are enumerated - even if you only care if there is at least one - use Paolo Tedesco's helpful extension to JaredPar's helpful answer. The down-side of this approach is that you always have to wait for a (potentially long-running) command to finish producing all output objects, even though - logically - the determination whether there are any output objects can be made as soon as the first object is received.

如果您想在遇到一个 [matching]对象后立即退出管道 ，则有两个选择:

If you want to exit the pipeline as soon as one [matching] object has been encountered, you have two options:

• [即席:易于理解，但实施起来很麻烦] 用 dummy循环封闭管道，并使用break中断管道，然后该循环(...代表要测试其输出的命令，而符合条件):

• [Ad-hoc: Easy to understand, but cumbersome to implement] Enclose the pipeline in a dummy loop and use break to break out of the pipeline and that loop (... represents the command whose output to test, and $_ ... match the condition):

 # Exit on first input object.
 [bool] $haveAny = do { ... | % { $true; break } } while ($false)

 # Exit on first input object that matches a condition.
 [bool] $haveAny = do { ... | % { if ($_ ...) { $true ; break } } } while ($false)

[使用实现起来很简单的PowerShell v3 +自包含实用程序功能] 请参见下面的功能Test-Any 的实现. 可以将其添加到脚本中，或在交互式会话中使用，添加到您的$PROFILE文件中.

[Use a PowerShell v3+ self-contained utility function that is nontrivial to implement] See the implementation of function Test-Any below. It can be added to scripts or, for use in interactive sessions, to your $PROFILE file.

该功能非常重要，因为从Windows PowerShell v5.1，PowerShell Core v6开始，没有 direct 方法过早退出管道，因此基于变通办法在.NET反射上，目前需要私有类型.

The function is nontrivial, because as of Windows PowerShell v5.1, PowerShell Core v6, there is no direct way to exit a pipeline prematurely, so a workaround based on .NET reflection and a private type is currently necessary.

如果您同意应该有这样的功能，请参加GitHub上的对话 a>.

If you agree that there should be such a feature, take part in the conversation on GitHub.

#requires -version 3
Function Test-Any {

    [CmdletBinding()]
    param(
        [ScriptBlock] $Filter,
        [Parameter(ValueFromPipeline = $true)] $InputObject
    )

    process {
      if (-not $Filter -or (Foreach-Object $Filter -InputObject $InputObject)) {
          $true # Signal that at least 1 [matching] object was found
          # Now that we have our result, stop the upstream commands in the
          # pipeline so that they don't create more, no-longer-needed input.
          (Add-Type -Passthru -TypeDefinition '
            using System.Management.Automation;
            namespace net.same2u.PowerShell {
              public static class CustomPipelineStopper {
                public static void Stop(Cmdlet cmdlet) {
                  throw (System.Exception) System.Activator.CreateInstance(typeof(Cmdlet).Assembly.GetType("System.Management.Automation.StopUpstreamCommandsException"), cmdlet);
                }
              }
            }')::Stop($PSCmdlet)
      }
    }
    end { $false }
}

如果未指定$Filter，则

• if (-not $Filter -or (Foreach-Object $Filter -InputObject $InputObject))的默认值为true，否则将使用手边的对象评估过滤器(脚本块).

  • if (-not $Filter -or (Foreach-Object $Filter -InputObject $InputObject)) defaults to true if $Filter wasn't specified, and otherwise evaluates the filter (script block) with the object at hand.

    • 使用ForEach-Object评估过滤器脚本块可确保$_在 all 方案中绑定到当前管道对象，如此处.
    • The use of ForEach-Object to evaluate the filter script block ensures that $_ binds to the current pipeline object in all scenarios, as demonstrated in PetSerAl's helpful answer here.

    (Add-Type ...语句使用通过C#代码创建的即席类型，该类型使用反射引发与Select-Object -First(PowerShell v3 +)在内部用于停止管道的相同异常，即[System.Management.Automation.StopUpstreamCommandsException]，该异常从PowerShell v5开始，仍然是 private 类型. 这里的背景: http://powershell.com/cs /blogs/tobias/archive/2010/01/01/cancelling-a-pipeline.aspx 非常感谢 PetSerAl 在评论中提供了此代码.

    The (Add-Type ... statement uses an ad-hoc type created with C# code that uses reflection to throw the same exception that Select-Object -First (PowerShell v3+) uses internally to stop the pipeline, namely [System.Management.Automation.StopUpstreamCommandsException], which as of PowerShell v5 is still a private type. Background here: http://powershell.com/cs/blogs/tobias/archive/2010/01/01/cancelling-a-pipeline.aspx A big thank-you to PetSerAl for contributing this code in the comments.

    示例:

    • PS> @() | Test-Any false

    • PS> @() | Test-Any false

    PS> Get-EventLog Application | Test-Any # should return *right away* true

    PS> Get-EventLog Application | Test-Any # should return *right away* true

    PS> 1, 2, 3 | Test-Any { $_ -gt 1 } # see if any object is > 1 true

    PS> 1, 2, 3 | Test-Any { $_ -gt 1 } # see if any object is > 1 true

    JaredPar的有用答案和Paolo Tedesco的有用扩展功能在一个方面是不足的:一旦有比赛，他们就不会退出管道被发现，这可能是一个重要的优化.

    JaredPar's helpful answer and Paolo Tedesco's helpful extension fall short in one respect: they don't exit the pipeline once a match has been found, which can be an important optimization.

    遗憾的是，即使从PowerShell v5开始，也没有直接方法过早退出管道. 如果您同意应该有这样的功能，请参加GitHub上的对话 .

    Sadly, even as of PowerShell v5, there is no direct way to exit a pipeline prematurely. If you agree that there should be such a feature, take part in the conversation on GitHub.

    JaredPar的答案的天真优化实际上缩短了代码:

    A naïve optimization of JaredPar's answer actually shortens the code:

    # IMPORTANT: ONLY EVER USE THIS INSIDE A PURPOSE-BUILT DUMMY LOOP (see below)
    function Test-Any() { process { $true; break } end { $false } }
    

    • 仅在管道中至少有一个元素的情况下才输入process块.
      • 小警告:根据设计，如果完全没有管道，则仍会输入process块，并且$_设置为$null ，因此调用Test-Any 管道外部无助地返回$true.要区分$null | Test-Any和Test-Any，请检查$MyInvocation.ExpectingInput(仅在管道中为$true):谢谢，
        • The process block is only entered if there's at least one element in the pipeline.
          • Small caveat: By design, if there's no pipeline at all, the process block is still entered, with $_ set to $null, so calling Test-Any outside of a pipeline unhelpfully returns $true. To distinguish between between $null | Test-Any and Test-Any, check $MyInvocation.ExpectingInput, which is $true only in a pipeline: ^{Thanks, PetSerAl} function Test-Any() { process { $MyInvocation.ExpectingInput; break } end { $false } }

          break终止管道，因此可以避免多余处理其他对象. 但是，它也退出了任何封闭的循环-break并非旨在退出管道 ^感谢， PetSerAl

          break then terminates the pipeline and thus prevents superfluous processing of additional objects. HOWEVER, IT ALSO EXITS ANY ENCLOSING LOOP - break is NOT designed to exit a PIPELINE^{Thanks, PetSerAl} .

          • 如果有 命令退出管道，这就是它的去向.
          • 请注意，return会简单地移至 next 输入对象.
          • If there were a command to exit the pipeline, this is where it would go.
          • Note that return would simply move on to the next input object.

          由于process块无条件执行break，因此只有在从未输入过process块的情况下才到达end块，这意味着流水线为空，因此将$false写入到输出流来发出信号.

          Since the process block unconditionally executes break, the end block is only reached if the process block was never entered, which implies an empty pipeline, so $false is written to the output stream to signal that.

          这篇关于PowerShell相当于LINQ Any()?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！