Register-ObjectEvent cmdlet 在 Powershell 上无法正常工作，但在 ISE 上工作

我正在开发一个 Powershell 脚本来监视文件夹，当创建新项目时，脚本需要将该文件复制到另一个文件夹。

我遇到的问题是，当我在 Powershell ISE 中执行它时，它工作得很好，但是当我在 Powershell 上执行它时，它仅在 Powershell 窗口打开的时间段内工作（> 1 秒）。

我尝试将 sleep 命令放在最后，发现只有当脚本结束时才会执行操作，在这种情况下，当我在 Powershell 中按 CTRL+C 停止脚本时，应该执行的操作创建的项目全部一起执行。

不知道我是否做错了什么或者只是误解了什么。

这是我用来测试它的脚本：

$Watcher = New-Object System.IO.FileSystemWatcher
$Watcher.path = "\\192.168.5.127\data\TestWatcher"
$Destination = "C:\TestWatcher"
$Watcher | Get-Member -MemberType Event
$Watcher.EnableRaisingEvents = $true

$action = {
    $path = $event.SourceEventArgs.FullPath
    $name = $event.SourceEventArgs.Name
    $changetype = $event.SourceEventArgs.ChangeType
    Write-Host "File $name at path $path was $changetype at $(get-date)"
    Copy-Item $Watcher.path $Destination
}

Register-ObjectEvent $Watcher 'Created' -Action $action

任何帮助或建议将不胜感激。

此致，

Gregor y在评论中提供了关键提示：

To 确保您的脚本无限期地继续处理事件， 你可以use a Wait-Event在脚本末尾调用无限期地等待永远不会到来的事件，这会让你的脚本保持运行，但是 - 不像Start-Sleep - does not通过传递给的脚本块块处理事件Register-ObjectEvent's -Action范围：

$Watcher = New-Object System.IO.FileSystemWatcher
$Watcher.path = "\\192.168.5.127\data\TestWatcher"
$Destination = "C:\TestWatcher"
$Watcher.EnableRaisingEvents = $true

$action = {
    $path = $event.SourceEventArgs.FullPath
    $name = $event.SourceEventArgs.Name
    $changetype = $event.SourceEventArgs.ChangeType
    Write-Host "File $name at path $path was $changetype at $(get-date)"
    Copy-Item $Watcher.path $Destination
}

# Register the event with a self-chosen name passed to -SourceIdentifier
# and an -Action script block.
$eventJob = 
  Register-ObjectEvent $Watcher Created -SourceIdentifier FileWatcher -Action $action

# Now wait indefinitely for an event with the same source identifier to arrive.
# NONE will ever arrive, because the events are handled via the -Action script block.
# However, the call will prevent your script from exiting, without
# blocking the processing of events in the -Action script block.
# Use Ctrl-C to exit the script; the `finally` clause ensures cleanup.
try {
  Wait-Event -SourceIdentifier FileWatcher
} 
finally {
  # Clean up: Remove the event job, which also unregisters the event.
  $eventJob | Remove-Job -Force 
}

或者，凑合一下without an -Action脚本块和进程事件Wait-Event loop:

$Watcher = New-Object System.IO.FileSystemWatcher
$Watcher.path = "\\192.168.5.127\data\TestWatcher"
$Destination = "C:\TestWatcher"
$Watcher.EnableRaisingEvents = $true

# Register the event with a self-chosen name passed to -SourceIdentifier
# but WITHOUT an -Action script block.
Register-ObjectEvent $Watcher 'Created' -SourceIdentifier FileWatcher

# Now use Wait-Event with the chosen source identifier to
# to indefinitely receive and then process the events as they 
# become available.
try {
  while ($event = Wait-Event -SourceIdentifier FileWatcher) {
    $path = $event.SourceEventArgs.FullPath
    $name = $event.SourceEventArgs.Name
    $changetype = $event.SourceEventArgs.ChangeType
    Write-Host "File $name at path $path was $changetype at $(Get-Date)"
    Copy-Item $Watcher.path $Destination
    $event | Remove-Event # Note: Events must be manually removed.
  }
}
finally {
  # Clean up.
  Unregister-Event -SourceIdentifier FileWatcher
}

替代方案事件轮询循环允许前台活动:

您可以调整以上内容以使用polling方法，通过使用无条件的无限循环，并替换Wait-Event with a Get-Event在循环体内调用，然后是短睡眠间隔（通过Start-Sleep），它允许您执行前台活动当没有收到任何事件时：

$Watcher = New-Object System.IO.FileSystemWatcher
$Watcher.path = "\\192.168.5.127\data\TestWatcher"
$Destination = "C:\TestWatcher"
$Watcher.EnableRaisingEvents = $true

# Register the event with a self-chosen name passed to -SourceIdentifier
# but WITHOUT an -Action script block.
Register-ObjectEvent $Watcher 'Created' -SourceIdentifier FileWatcher

# Now enter an infinite loop that uses Get-Event to poll for
# available events and processes them.
# If none are available, foreground activity can be performed
# (which should be short-lived, otherwise event retrieval is blocked).
try {
  while ($true) {
    if ($event = Get-Event | Where-Object SourceIdentifier -eq FileWatcher) {
      $path = $event.SourceEventArgs.FullPath
      $name = $event.SourceEventArgs.Name
      $changetype = $event.SourceEventArgs.ChangeType
      Write-Host "File $name at path $path was $changetype at $(Get-Date)"
      Copy-Item $Watcher.path $Destination
      $event | Remove-Event # Note: Events must be manually removed.
    } else { # No event available.
      # Perform (short-lived) foreground activities here.
      Write-Host -NoNewline .
      Start-Sleep -Milliseconds 500 # Sleep a little, to avoid a tight loop.
    }
  }
}
finally {
  # Clean up.
  Unregister-Event -SourceIdentifier FileWatcher
}

Note:

• Due to a bug present up to at least PowerShell v7.3.x, Get-Event doesn't work with the -SourceIdentifier parameter, hence the Get-Event | Where-Object SourceIdentifier -eq FileWatcher workaround above.
  • See GitHub 问题 #11705.