如何查看文件，每当它发生变化时，采用新的附加行并使用 powershell 对其执行一些操作

如何解决如何查看文件，每当它发生变化时，采用新的附加行并使用 powershell 对其执行一些操作

如何查看日志文件，每次添加一行时，我想重新格式化该行并使用 Invoke-RestMethod（基本上使用 discord 作为日志文件）将其广播到 webhook，然后可能还输出一些/相同的信息到控制台。

这与其他人提出的类似问题类似。我一直在尝试这样做 2 周。在以下帖子中，他们回答了大部分问题：

Watch file for changes and run command with powershell

但是，它没有显示如何将添加的行添加到文件中并对它执行所有操作，同时它仍在等待日志文件使用下一个条目再次更新。日志文件可以连续快速更新，因此当程序对检测到的更改执行所述操作时，如果日志文件发生其他更改，则不确定这些方法是否会跟上更改。

到目前为止，我一直在循环中尝试这样的事情（这不是整个代码）：

get-content '<file-name>' -tail 1 -wait

但是看起来这可能会连续遗漏行，因为在处理附加操作时，可能会出现更多行。所以看起来我可能需要以更复杂的方式执行此操作（没关系）。只是想弄清楚该往哪个方向走。

非常感谢任何建议或方向。如果需要的话，甚至是一个链接。

解决方法

您所做的只是允许在屏幕上实时显示文件。你不能弄乱输出这样做。

您使用的命令不适用于交互式用例。

您可以通过使用 SystemFileWatcher 监控文件更新，而无需执行您正在执行的操作，它允许监控文件操作，然后您可以对其进行操作。

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'PowerShell filesystemwatcher 监控文件'

https://duckduckgo.com/?q=%27PowerShell+filesystemwatcher+monitor+file%27&t=h_&ia=web

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例如来自上述链接的点击之一。

https://powershell.one/tricks/filesystem/filesystemwatcher

监视文件夹的文件更改

使用 FileSystemWatcher，您可以监视文件夹中的文件更改和 当检测到变化时立即响应。这样，你可以 创建“drop”文件夹并响应日志文件更改。

具体来说，根据您的用例：

高级模式（异步）

如果您希望更改快速连续发生，甚至 同时，您可以异步使用 FileSystemWatcher 模式：FileSystemWatcher 现在在后台工作，不再 阻止 PowerShell。相反，每当发生变化时，事件就会发生 提高。所以用这种方法，你会得到一个队列，不会错过任何一个 改变。

在背面，这种方法有两个挑战：

• 处理事件：由于 PowerShell 本质上是单线程的，因此 响应事件不简单，调试起来更麻烦 事件处理程序代码。

  保持 PowerShell 运行：讽刺的是，因为 FileSystemWatcher 现在不再阻止 PowerShell，这会导致另一个问题。你 需要让 PowerShell 等待事件，但您不能使用 Start-Sleep 或无限循环，因为只要 PowerShell 很忙

  • 即使它处于睡眠状态也被认为是忙碌的 - 无法处理任何事件。

实施

下面的脚本和同步版本做的完全一样 从上面看，只有它是基于事件的，不会再错过任何事件：

# find the path to the desktop folder:
$desktop = [Environment]::GetFolderPath('Desktop')

# specify the path to the folder you want to monitor:
$Path = $desktop

# specify which files you want to monitor
$FileFilter = '*'  

# specify whether you want to monitor subfolders as well:
$IncludeSubfolders = $true

# specify the file or folder properties you want to monitor:
$AttributeFilter = [IO.NotifyFilters]::FileName,[IO.NotifyFilters]::LastWrite 

try
{
  $watcher = New-Object -TypeName System.IO.FileSystemWatcher -Property @{
    Path = $Path
    Filter = $FileFilter
    IncludeSubdirectories = $IncludeSubfolders
    NotifyFilter = $AttributeFilter
  }

  # define the code that should execute when a change occurs:
  $action = {
    # the code is receiving this to work with:
    
    # change type information:
    $details = $event.SourceEventArgs
    $Name = $details.Name
    $FullPath = $details.FullPath
    $OldFullPath = $details.OldFullPath
    $OldName = $details.OldName
    
    # type of change:
    $ChangeType = $details.ChangeType
    
    # when the change occured:
    $Timestamp = $event.TimeGenerated
    
    # save information to a global variable for testing purposes
    # so you can examine it later
    # MAKE SURE YOU REMOVE THIS IN PRODUCTION!
    $global:all = $details
    
    # now you can define some action to take based on the
    # details about the change event:
    
    # let's compose a message:
    $text = "{0} was {1} at {2}" -f $FullPath,$ChangeType,$Timestamp
    Write-Host ""
    Write-Host $text -ForegroundColor DarkYellow
    
    # you can also execute code based on change type here:
    switch ($ChangeType)
    {
      'Changed'  { "CHANGE" }
      'Created'  { "CREATED"}
      'Deleted'  { "DELETED"
        # to illustrate that ALL changes are picked up even if
        # handling an event takes a lot of time,we artifically
        # extend the time the handler needs whenever a file is deleted
        Write-Host "Deletion Handler Start" -ForegroundColor Gray
        Start-Sleep -Seconds 4    
        Write-Host "Deletion Handler End" -ForegroundColor Gray
      }
      'Renamed'  { 
        # this executes only when a file was renamed
        $text = "File {0} was renamed to {1}" -f $OldName,$Name
        Write-Host $text -ForegroundColor Yellow
      }
        
      # any unhandled change types surface here:
      default   { Write-Host $_ -ForegroundColor Red -BackgroundColor White }
    }
  }

  # subscribe your event handler to all event types that are
  # important to you. Do this as a scriptblock so all returned
  # event handlers can be easily stored in $handlers:
  $handlers = . {
    Register-ObjectEvent -InputObject $watcher -EventName Changed  -Action $action 
    Register-ObjectEvent -InputObject $watcher -EventName Created  -Action $action 
    Register-ObjectEvent -InputObject $watcher -EventName Deleted  -Action $action 
    Register-ObjectEvent -InputObject $watcher -EventName Renamed  -Action $action 
  }

  # monitoring starts now:
  $watcher.EnableRaisingEvents = $true

  Write-Host "Watching for changes to $Path"

  # since the FileSystemWatcher is no longer blocking PowerShell
  # we need a way to pause PowerShell while being responsive to
  # incoming events. Use an endless loop to keep PowerShell busy:
  do
  {
    # Wait-Event waits for a second and stays responsive to events
    # Start-Sleep in contrast would NOT work and ignore incoming events
    Wait-Event -Timeout 1

    # write a dot to indicate we are still monitoring:
    Write-Host "." -NoNewline
        
  } while ($true)
}
finally
{
  # this gets executed when user presses CTRL+C:
  
  # stop monitoring
  $watcher.EnableRaisingEvents = $false
  
  # remove the event handlers
  $handlers | ForEach-Object {
    Unregister-Event -SourceIdentifier $_.Name
  }
  
  # event handlers are technically implemented as a special kind
  # of background job,so remove the jobs now:
  $handlers | Remove-Job
  
  # properly dispose the FileSystemWatcher:
  $watcher.Dispose()
  
  Write-Warning "Event Handler disabled,monitoring ends."
}

因此，根据上述内容，您可以对其进行调整以查找更新/修改，然后使用

$CaptureLine = Get-Content -Path 'UNCToTheLogFile' | Select-Object -Last 1

或

$CaptureLine = Get-Content -Path  'D:\temp\book1.csv' -Tail 1

然后做你想做的事。