由于 Filesystemwatcher，Powershell 挂起

Question

我们有一些复杂的解决方案来解决一些打印问题(由 citrix 和远程服务器引起)。基本上从主服务器，我们强制将 pdf 文件推送到远程 pc，然后有一个 powershell 脚本不断在远程 pc 上运行以“捕获”文件并将其推送到本地打印机

这工作“很好”

然而，我们得到随机辍学。 powershell 脚本似乎没有崩溃，因为它仍在 windows 中运行，但实际操作似乎不是在处理新文件

我今天读了很多书，其中提到在完成后必须命名和取消注册事件，否则它会导致缓冲区溢出问题并使 powershell 停止处理操作。但我不确定它应该在代码中的实际位置。这个想法是这个脚本将永久运行，所以我们是在操作本身还是其他地方取消注册或删除事件？

我之前在操作中进行了很多虚拟日志记录以试图找到它失败的地方，但它似乎在没有任何正当理由的情况下停止在不同的点(即，它会在命令查找文件时失败，其他命令移动等的时间等)

### SET FOLDER TO WATCH + FILES TO WATCH + SUBFOLDERS YES/NO
$watcher = New-Object System.IO.FileSystemWatcher
$watcher.Path = "l:\files\cut"
$watcher.Filter = "*.pdf"
$watcher.IncludeSubdirectories = $false
$watcher.EnableRaisingEvents = $true  

### DEFINE ACTIONS AFTER AN EVENT IS DETECTED
$action = { $path = $Event.SourceEventArgs.FullPath
            $changeType = $Event.SourceEventArgs.ChangeType
            $scandir="l:\files\cut" 
            $scanbackdir="l:\files\cut\back"   
            $scanlogdir="l:\files\cut\log" 
            $sumatra="l:\SumatraPDF.exe"      
            $pdftoprint=""
            $printername= "MainLBL"

### Get the List of files in the Directory, print file, wait and then move file
Get-ChildItem -Path $scandir -filter "*.pdf" -Name | % { 
$pdftoprint=$_ 
& $sumatra -silent $scandir\$pdftoprint -print-to $printername

sleep 3 

Move-Item -force $scandir\$pdftoprint $scanbackdir
 }
 } 

### Define what happens when script fails
$erroraction = {echo $(get-date) the process crashed | Out-File -Append l:\files\cut\log\errorlog.txt}    

### DECIDE WHICH EVENTS SHOULD BE WATCHED 
Register-ObjectEvent $watcher "Error" -Action $erroraction
Register-ObjectEvent $watcher "Created" -Action $action
while ($true) {sleep 5}

Answer 1

如果您希望脚本在后台运行，请查看 PowerShell 后台作业。

如果你想让一个脚本永久运行，那么你想让它成为一个服务......

查看这些:

How to Create a User-Defined Service

How to run a PowerShell script as a Windows service

...或将其附加到计划任务，这将在重新启动时重新启动它。

有两种方法可以实现 FileSystemWatcher。

• 同步
• 异步

同步 FileSystemWatcher，就其本质而言，当检测到更改时，控制权将返回给您的脚本，以便它可以处理更改。如果在您的脚本不再等待事件时发生另一个文件更改，它就会丢失。因此导致意想不到的结果。

异步使用 FileSystemWatcher，它将继续记录新的文件系统更改，并在 PowerShell 处理完之前的更改后处理它们。

* 示例 - 示例异步 FileSystemWatcher*

### New-FileSystemWatcherAsynchronous

# Set the folder target
$PathToMonitor = Read-Host -Prompt 'Enter a folder path'

$FileSystemWatcher = New-Object System.IO.FileSystemWatcher
$FileSystemWatcher.Path  = $PathToMonitor
$FileSystemWatcher.IncludeSubdirectories = $true

# Set emits events
$FileSystemWatcher.EnableRaisingEvents = $true

# Define change actions
$Action = {
    $details = $event.SourceEventArgs
    $Name = $details.Name
    $FullPath = $details.FullPath
    $OldFullPath = $details.OldFullPath
    $OldName = $details.OldName
    $ChangeType = $details.ChangeType
    $Timestamp = $event.TimeGenerated
    $text = "{0} was {1} at {2}" -f $FullPath, $ChangeType, $Timestamp

    Write-Host $text -ForegroundColor Green

    # Define change types
    switch ($ChangeType)
    {
        'Changed' { "CHANGE" }
        'Created' { "CREATED"}
        'Deleted' { "DELETED"
                    # Set time intensive handler
                    Write-Host "Deletion Started" -ForegroundColor Gray
                    Start-Sleep -Seconds 3    
                    Write-Warning -Message 'Deletion complete'
                  }
        'Renamed' { 
                    $text = "File {0} was renamed to {1}" -f $OldName, $Name
                    Write-Host $text -ForegroundColor Yellow
                  }
        default { Write-Host $_ -ForegroundColor Red -BackgroundColor White }
    }
}

# Set event handlers
$handlers = . {
    Register-ObjectEvent -InputObject $FileSystemWatcher -EventName Changed -Action $Action -SourceIdentifier FSChange
    Register-ObjectEvent -InputObject $FileSystemWatcher -EventName Created -Action $Action -SourceIdentifier FSCreate
    Register-ObjectEvent -InputObject $FileSystemWatcher -EventName Deleted -Action $Action -SourceIdentifier FSDelete
    Register-ObjectEvent -InputObject $FileSystemWatcher -EventName Renamed -Action $Action -SourceIdentifier FSRename
}

Write-Host "Watching for changes to $PathToMonitor" -ForegroundColor Cyan

try
{
    do
    {
        Wait-Event -Timeout 1
        Write-Host '.' -NoNewline

    } while ($true)
}
finally
{
    # End script actions + CTRL+C executes the remove event handlers
    Unregister-Event -SourceIdentifier FSChange
    Unregister-Event -SourceIdentifier FSCreate
    Unregister-Event -SourceIdentifier FSDelete
    Unregister-Event -SourceIdentifier FSRename

    # Remaining cleanup
    $handlers | 
    Remove-Job

    $FileSystemWatcher.EnableRaisingEvents = $false
    $FileSystemWatcher.Dispose()

    Write-Warning -Message 'Event Handler completed and disabled.'
}