PowerShell 捕获写入主机输出 [英] PowerShell Capture Write-Host output

问题描述

我必须运行 Microsoft cmdlet，并且使用 cmdlet 中的 Write-Host 行将重要信息写入控制台.

I am having to run a Microsoft cmdlet, and the important bit of information is written to console using a Write-Host line within the cmdlet.

它没有返回，所以我不能做 $result = Commandlet ...返回了一个对我没有用的不同值，我实际需要的是在命令行开关中打印到控制台，无论如何我可以嗅探"或抓取"控制台以获取我想要的信息吗?

It is NOT returned, so I cannot do $result = Commandlet ... A different value is returned that is not of use to me, what I actually need is printed to console within the commandlet is there anyway I can 'sniff' or 'scrape' the console to get the information I want?

$result = Test-Cluser

Test-Cluster 将打印如下内容:'HadUnselectedTests'、'ClusterConditionallyApproved' 等.但是它在 .htm 报告文件的路径中返回的值.不幸的是，.htm 报告文件不包含这些状态代码之一，所以我也不能只为它解析 .htm 文件.

Test-Cluster will print stuff like: 'HadUnselectedTests', 'ClusterConditionallyApproved', etc. But the value it returns in the path to the .htm report file. And the .htm report file does not contain one of those status codes unfortunately so I cannot just parse the .htm file for it either.

有什么建议吗?

推荐答案

注意:至于 为什么永远不应该使用 Write-Host 输出数据，见这个答案.

在PSv5+中:

$result = Test-Cluster 6>&1

从版本 5 开始，Write-Host 写入新引入的信息流，其编号为 6.

Since version 5, Write-Host writes to the newly introduced information stream, whose number is 6.

6>&1 将该流重定向到成功输出流(编号 1)，以便它也可以在 $result.

6>&1 redirects that stream to the success output stream (number 1), so that it too can be captured in $result.

在PSv4-:

没有方法可以捕获Write-Host输出会话中.

There is no way to capture Write-Host output in-session.

唯一的解决方法是启动另一个 Powershell 实例，并将目标命令指定为字符串.
注意事项:

The only workaround is to launch another instance of Powershell with the target command specified as a string.
Caveats:

• 这样的调用很慢，
• 防止传递具有原始数据类型的参数
• 总是只返回字符串数据(文本行)
• 从所有输出流返回输出，包括错误输出
  • 有关所有输出流的列表，请参阅获取关于_重定向的帮助
  • Such an invocation is slow,
  • prevents passing of arguments with their original data type
  • invariably only returns string data (lines of text)
  • returns output from all output streams, including error output
    • for a list of all output streams, see Get-Help about_Redirection

    $result = powershell -noprofile -command 'Test-Cluster'
    

    ^{请注意，使用 脚本块 来传递命令 (-command { Test-Cluster }) 将 行不通，因为 PowerShell 然后使用序列化和反序列化来模拟会话中的行为.}

    ^{Note that using a script block to pass the command (-command { Test-Cluster }) would not work, because PowerShell then uses serialization and deserialization to emulate the in-session behavior.}

    获取帮助 about_Redirection 讨论了所有输出流的列表，可以通过它们的编号来定位；从 PSv5 开始，这些是:

    Get-Help about_Redirection discusses a list of all output streams, which can be targeted by their numbers; since PSv5, these are:

    1 ... success output stream (implicit output and Write-Output output)
    2 ... error output stream (Write-Error and unhandled errors)
    3 ... warnings (Write-Warning)
    4 ... verbose output (Write-Verbose)
    5 ... debug output (Write-Debug)
    6 ... (v5+) Write-Information and Write-Host output
    

    请注意，某些流默认情况下是静默的，需要选择加入以通过首选项变量(例如 $VerbosePreference)或公共参数(例如 -Verbose)

    Note that some streams are silent by default and require opt-in to produce output, either via a preference variable (e.g., $VerbosePreference) or a common parameter (e.g., -Verbose)

    • {n}> 允许重定向数字 {n} 流；如果省略 {n}，则隐含 1:

    • {n}> allows redirecting the number {n} stream; if {n} is omitted, 1 is implied:

    • 到一个文件(例如，3> c:/tmp/warnings.txt
    • 到无处"，即抑制输出(例如，3> $null)
    • 到成功输出流(例如，3>&1)；注意:只有流 1 可以通过这种方式定位.
    • to a file (e.g., 3> c:/tmp/warnings.txt
    • to "nowhere", i.e suppressing the output (e.g., 3> $null)
    • to the success output stream (e.g., 3>&1); note: only stream 1 can be targeted this way.

    *> 目标 所有 输出流.

    注意:与 POSIX 类 shell(例如，bash)不同，multiple 重定向表达式的 order 不 很重要.

    Note: Unlike in POSIX-like shells (e.g., bash), the order of multiple redirection expression does not matter.

    因此，以下类似 POSIX 的 shell 习惯用法 - 将错误输出重定向到成功流并仅使 原始 成功输出静音 - 不起作用:

    Therefore, the following POSIX-like shell idiom - which redirects error output to the success stream and silences only the original success output - does NOT work:

    ... 2>&1 1>$null # !! NO output in PowerShell
    

    要在 PowerShell 中实现这一点，您不能重定向 1，而是通过源流过滤成功的对象.

    To achieve this in PowerShell, you mustn't redirect 1 and instead filter the objects in the success by their stream of origin.

    举个例子:最后，OP 想要以下内容:只捕获警告输出，没有常规(成功)输出:

    Case in point: In the end, the OP wanted the following: capture only warning output, without the regular (success) output:

    Test-Cluster 3>&1 | Where-Object { $_ -is [System.Management.Automation.WarningRecord] }
    

    来自警告流的对象具有 [System.Management.Automation.WarningRecord] 类型，这是启用上述过滤的原因.

    Objects that came from the warning stream have type [System.Management.Automation.WarningRecord], which is what enables the filtering above.

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