写主机和写输出的结果有什么区别? [英] What is the difference in result by write-host and write-output?

问题描述

我是 PowerShell 的新手，在编写一些代码时，我遇到了这件事.当我使用 Write-Host 和 Write-Output 来执行相同的查询时，我得到了不同的结果:

I am new to PowerShell and while doing some code I came through this thing. While I use Write-Host and Write-Output to perform the same query, I get different results:

PS> Write-Output $PSVersionTable                                                                                                                   

Name                           Value                                                                                                                                               
----                           -----                                                                                                                                               
PSVersion                      5.0.10586.117                                                                                                                                          
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}                                                                                                                             
BuildVersion                   10.0.10586.117
CLRVersion                     4.0.30319.17929
WSManStackVersion              3.0                                                                                                                                                 
PSRemotingProtocolVersion      2.3                                                                                                                                                 
SerializationVersion           1.1.0.1                                                                                                                                             

对比

PS> Write-Host $PSVersionTable                                                                                                                   
System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry System.Collections.DictionaryEntry

推荐答案

重要区别:

Write-output 将一个对象写入管道，因此下一个命令可以接受它作为输入.而Write-host只是直接写入控制台.

Write-output writes an object to the pipeline, so the next command can accept it as it's input. While Write-host just write directly to the console.

在你的例子中

Write-Output 将对象写入管道，Out-Default(隐藏在管道的末尾)将在表格或列表中显示对象值.

Write-Output will write the object to the pipeline, and Out-Default (Hidden at the end of the pipeline) will display the object values in either a table or a list.

Write-Host 直接写入控制台，而不是在管道末端使用默认的 cmdlet Out-default.换句话说，Write-Host 不会向管道写入任何内容，只会向控制台显示他看到的内容.这就是您可以将 -foregroundcolor 等参数添加到 Write-Host cmdlet 而不能添加到 Write-output cmdlet 的原因.

Write-Host writes directly to the console instead of using the default cmdlet Out-default in the end of the pipeline. In other words, Write-Host does not write anything to the pipeline, only displays what he sees to the console.. This is why you can add parameters like -foregroundcolor to the Write-Host cmdlet, but not to the Write-output cmdlet.

Write-Host 在调试时很有用，您需要以不同的颜色显示文本.

Write-Host is useful when debugging and you need to display text in diffrent colors.

你可以用

Write-Output "Hello World" | Get-Member

我们可以看出这是一个 System.String 对象.

We can se that this is a System.String Object.

如果我们运行:

Write-Host "Hello World" | Get-Member

我们得到一个错误:gm :您必须为 Get-Member cmdlet 指定一个对象...

We get an error: gm : You must specify an object for the Get-Member cmdlet ...

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