创建时复制文件(一次完成)

问题描述

我有以下代码来检测新文件的创建并获取其副本.

I have the below code to detect the creation of a new file and grab a copy of it.

$folder = '\\server\share\monitor_me\'
$filter = '*.*'
$copyToFolder = 'C:\temp\capture\'

$fsw = New-Object IO.FileSystemWatcher $folder, $filter -Property @{IncludeSubdirectories = $true;NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite'}

#protection from previous runs
unregister-event -SourceIdentifier FileCreated -ErrorAction SilentlyContinue

Register-ObjectEvent $fsw Created -SourceIdentifier FileCreated -Action {
    $name = $Event.SourceEventArgs.Name
    $changeType = $Event.SourceEventArgs.ChangeType
    $timeStamp = $Event.TimeGenerated
    Write-Host "The file '$name' was $changeType at $timeStamp" -fore green
    Copy-Item -Path $Event.SourceEventArgs.FullPath -Destination $copyToFolder
}

在并行会话中使用此代码对其进行测试:

Testing it with this code in a parallel session:

1..1000 `
| %{new-object -TypeName pscustomobject -Property @{Id=$_;Name="hi"} } `
| export-csv '\\server\share\monitor_me\test.csv'

...表明代码确实起作用；但是会在文件出现时立即捕获文件，而不是等待文件完全填充，因此我只得到了部分结果文件的内容.

...shows that the code does work; but captures the file the moment it appears rather than waiting for it to be fully populated, so I only get some of the resulting file's content.

我可以添加一个start-sleep语句；但这会导致比赛条件.

I could add a start-sleep statement; but that would lead to race conditions.

我假设文件在写入时有一个锁(即防止其他进程更新同一文件；但不影响文件的读取/复制)，因此理想情况下希望有某种方法可以等到该锁已被删除.

I assume that there's a lock on the file whilst it's being written to (i.e. preventing other processes from updating the same file; but not affecting reading/copying of the file), so would ideally like to have some way to wait until that lock's removed.

• 我是否认为对export-csv进程有文件锁定是正确的?
• 有没有一种方法可以检测到何时删除了锁?

• Is my assumption about there being a file lock for the export-csv process correct?
• Is there a way to detect when the lock's removed?

预先感谢

推荐答案

通过将监视的事件更改为CHANGED来解决.初始创建后似乎发生了2个更改事件.为简单起见，我只监视任何更改事件(从而确保始终拥有最新副本)，并包含-Force参数以允许覆盖目标文件.

Resolved by changing the monitored event to CHANGED. It seems 2 change events occur after the initial create. For simplicity I just monitor for any change event (thus ensuring I'll always have the latest copy) and include the -Force parameter to allow the destination file to be overwritten.

Register-ObjectEvent $fsw Changed -SourceIdentifier FileUpdated -Action {
    $name = $Event.SourceEventArgs.Name
    $changeType = $Event.SourceEventArgs.ChangeType
    $timeStamp = $Event.TimeGenerated
    Write-Host "The file '$name' was $changeType at $timeStamp" -fore green
    Copy-Item -Path $Event.SourceEventArgs.FullPath -Destination  $copyToFolder -Force
}

注意:我不确定100％是否会立即捕获所有新文件.因为可能有某种方法可以创建文件而不触发变更事件(即我还没有找到任何文档说明这种情况不存在)；但对于我当前的目的来说似乎已经足够了.

NB: I'm not 100% sure whether this will now capture all new files; as potentially there's some way to create a file without also triggering a change event (i.e. I've not found any documentation to say this scenario doesn't exist); but seems good enough for my current purposes.

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