将Write-Host语句重定向到文件

Question

我有一个正在调试的PowerShell脚本，希望将所有Write-Host语句重定向到一个文件。有什么简单的方法可以做到这一点吗？

Answer 1

直到PowerShell 4.0，Write-Host都会将对象发送到主机。它不返回任何对象。

从PowerShell 5.0和更高版本开始，Write-Host是Write-Information的包装器，它允许输出到信息流并使用6>> file_name重定向它。

http://technet.microsoft.com/en-us/library/hh849877.aspx

但是，如果您有很多Write-Host语句，请将它们全部替换为Write-Log，它允许您决定是输出到控制台、文件还是事件日志，还是全部输出到这三个。

另请检查：

像>, >>, 2>, 2>, 2>&1

• Write-Log

• Tee-Object

• Start-Transcript.

一样的

• Add-Content
• redirection operators

Answer 2

您可以为Write-Host创建一个代理函数，该函数将对象发送到标准输出流，而不仅仅是打印它们。我写了下面的cmdlet就是为了这个目的。它将在运行中创建一个代理，该代理仅在当前管道的持续时间内持续。

完整的文章在我的博客here上，但我已经包含了下面的代码。使用-Quiet开关抑制控制台写入。

用法：

PS> .\SomeScriptWithWriteHost.ps1 | Select-WriteHost | out-file .\data.log  # Pipeline usage
PS> Select-WriteHost { .\SomeScriptWithWriteHost.ps1 } | out-file .\data.log  # Scriptblock usage (safer)

function Select-WriteHost
{
   [CmdletBinding(DefaultParameterSetName = 'FromPipeline')]
   param(
     [Parameter(ValueFromPipeline = $true, ParameterSetName = 'FromPipeline')]
     [object] $InputObject,

     [Parameter(Mandatory = $true, ParameterSetName = 'FromScriptblock', Position = 0)]
     [ScriptBlock] $ScriptBlock,

     [switch] $Quiet
   )

   begin
   {
     function Cleanup
     {
       # Clear out our proxy version of write-host
       remove-item function:\write-host -ea 0
     }

     function ReplaceWriteHost([switch] $Quiet, [string] $Scope)
     {
         # Create a proxy for write-host
         $metaData = New-Object System.Management.Automation.CommandMetaData (Get-Command 'Microsoft.PowerShell.Utility\Write-Host')
         $proxy = [System.Management.Automation.ProxyCommand]::create($metaData)

         # Change its behavior
         $content = if($quiet)
                    {
                       # In quiet mode, whack the entire function body,
                       # simply pass input directly to the pipeline
                       $proxy -replace '(?s)\bbegin\b.+', '$Object'
                    }
                    else
                    {
                       # In noisy mode, pass input to the pipeline, but allow
                       # real Write-Host to process as well
                       $proxy -replace '(\$steppablePipeline\.Process)', '$Object; $1'
                    }

         # Load our version into the specified scope
         Invoke-Expression "function ${scope}:Write-Host { $content }"
     }

     Cleanup

     # If we are running at the end of a pipeline, we need
     #    to immediately inject our version into global
     #    scope, so that everybody else in the pipeline
     #    uses it. This works great, but it is dangerous
     #    if we don't clean up properly.
     if($pscmdlet.ParameterSetName -eq 'FromPipeline')
     {
        ReplaceWriteHost -Quiet:$quiet -Scope 'global'
     }
   }

   process
   {
      # If a scriptblock was passed to us, then we can declare
      #   our version as local scope and let the runtime take
      #   it out of scope for us. It is much safer, but it
      #   won't work in the pipeline scenario.
      #
      #   The scriptblock will inherit our version automatically
      #   as it's in a child scope.
      if($pscmdlet.ParameterSetName -eq 'FromScriptBlock')
      {
        . ReplaceWriteHost -Quiet:$quiet -Scope 'local'
        & $scriptblock
      }
      else
      {
         # In a pipeline scenario, just pass input along
         $InputObject
      }
   }

   end
   {
      Cleanup
   }
}

Answer 3

使用重定向将导致Write-Host挂起。这是因为Write-Host处理特定于当前使用的终端的各种格式化问题。如果你只想让你的脚本能够像平常一样灵活地输出(默认是shell，支持>、2>等)，那么可以使用Write-Output。

否则，如果您真的想要捕捉当前终端的特性，那么Start-Transcript是一个很好的起点。否则，您将不得不手动测试或编写一些复杂的测试套件。