有没有办法在 powershell 中使用 WebClient 对象监控下载进度？

Question

我正在使用这样的简单行下载文件：

$webclient = New-Object -TypeName System.Net.WebClient
$webclient.DownloadFile("https://www.example.com/file", "C:/Local/Path/file")

问题是我想在下载时使用弹出窗口或使用外壳中的进度条向用户显示一条消息。是否可以制作一个下载完成后消失的弹出框，或者一个监控下载进度的进度条？

Answer 1

要显示下载文件的进度条，请查看 Jason Niver 的博客文章：

Downloading files from the internet in Power Shell (with progress)

基本上，您可以创建一个仍使用 Web 客户端功能但包含捕获状态的方法的函数。然后，您可以使用 写入进度 Power shell 功能。

function DownloadFile($url, $targetFile)

{

   $uri = New-Object "System.Uri" "$url"

   $request = [System.Net.HttpWebRequest]::Create($uri)

   $request.set_Timeout(15000) #15 second timeout

   $response = $request.GetResponse()

   $totalLength = [System.Math]::Floor($response.get_ContentLength()/1024)

   $responseStream = $response.GetResponseStream()

   $targetStream = New-Object -TypeName System.IO.FileStream -ArgumentList $targetFile, Create

   $buffer = new-object byte[] 10KB

   $count = $responseStream.Read($buffer,0,$buffer.length)

   $downloadedBytes = $count

   while ($count -gt 0)

   {

       $targetStream.Write($buffer, 0, $count)

       $count = $responseStream.Read($buffer,0,$buffer.length)

       $downloadedBytes = $downloadedBytes + $count

       Write-Progress -activity "Downloading file '$($url.split('/') | Select -Last 1)'" -status "Downloaded ($([System.Math]::Floor($downloadedBytes/1024))K of $($totalLength)K): " -PercentComplete ((([System.Math]::Floor($downloadedBytes/1024)) / $totalLength)  * 100)

   }

   Write-Progress -activity "Finished downloading file '$($url.split('/') | Select -Last 1)'"

   $targetStream.Flush()

   $targetStream.Close()

   $targetStream.Dispose()

   $responseStream.Dispose()

}

---

然后你只需调用函数：

downloadFile "http://example.com/largefile.zip" "c:\temp\largefile.zip"

---

此外，还有一些来自 docs.microsoft 的其他 Write-Progress 示例，用于 powrshell 7。

Write-Progress

Answer 2

在 V2 中，您可以只使用 BitsTransfer 模块，例如：

Import-Module BitsTransfer
Start-BitsTransfer https://www.example.com/file C:/Local/Path/file

Answer 3

在我重写一些安装脚本时，我遇到了这个问题。这些方法都不是理想的。第一种方法在 Windows PowerShell 上存在性能问题，第二种方法需要最新的系统，我们都知道它在现实生活中是如何工作的。 ??‍♀️

为了获得最佳性能，我将这两种方法结合到一个智能方法中，使其更加通用，遵循 PowerShell 最佳实践。

可以在here找到一些基准。

function Get-File
{
    param (
        [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [System.Uri]
        $Uri,
        [Parameter(Mandatory, ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [System.IO.FileInfo]
        $TargetFile,
        [Parameter(ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [Int32]
        $BufferSize = 1,
        [Parameter(ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [ValidateSet('KB, MB')]
        [String]
        $BufferUnit = 'MB',
        [Parameter(ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [ValidateSet('KB, MB')]
        [Int32]
        $Timeout = 10000
    )

    $useBitTransfer = $null -ne (Get-Module -Name BitsTransfer -ListAvailable) -and ($PSVersionTable.PSVersion.Major -le 5)

    if ($useBitTransfer)
    {
        Write-Information -MessageData 'Using a fallback BitTransfer method since you are running Windows PowerShell'
        Start-BitsTransfer -Source $Uri -Destination "$($TargetFile.FullName)"
    }
    else
    {
        $request = [System.Net.HttpWebRequest]::Create($Uri)
        $request.set_Timeout($Timeout) #15 second timeout
        $response = $request.GetResponse()
        $totalLength = [System.Math]::Floor($response.get_ContentLength() / 1024)
        $responseStream = $response.GetResponseStream()
        $targetStream = New-Object -TypeName ([System.IO.FileStream]) -ArgumentList "$($TargetFile.FullName)", Create
        switch ($BufferUnit)
        {
            'KB' { $BufferSize = $BufferSize * 1024 }
            'MB' { $BufferSize = $BufferSize * 1024 * 1024 }
            Default { $BufferSize = 1024 * 1024 }
        }
        Write-Verbose -Message "Buffer size: $BufferSize B ($($BufferSize/("1$BufferUnit")) $BufferUnit)"
        $buffer = New-Object byte[] $BufferSize
        $count = $responseStream.Read($buffer, 0, $buffer.length)
        $downloadedBytes = $count
        $downloadedFileName = $Uri -split '/' | Select-Object -Last 1
        while ($count -gt 0)
        {
            $targetStream.Write($buffer, 0, $count)
            $count = $responseStream.Read($buffer, 0, $buffer.length)
            $downloadedBytes = $downloadedBytes + $count
            Write-Progress -Activity "Downloading file '$downloadedFileName'" -Status "Downloaded ($([System.Math]::Floor($downloadedBytes/1024))K of $($totalLength)K): " -PercentComplete ((([System.Math]::Floor($downloadedBytes / 1024)) / $totalLength) * 100)
        }

        Write-Progress -Activity "Finished downloading file '$downloadedFileName'"

        $targetStream.Flush()
        $targetStream.Close()
        $targetStream.Dispose()
        $responseStream.Dispose()
    }
}