在 Windows 命令提示符/PowerShell 中下载大文件

Question

我现在已经没有办法了……

尝试 1

在 Powershell 中使用 iwr。它可以工作，显示进度，但速度慢 10 倍，并且直到文件在内存中时才会刷新:(。

 powershell -command "& { iwr https://github.com/mitchellspryn/AirsimHighPolySuv/releases/download/V1.0.0/SUV.zip -OutFile SUV.zip }"

尝试 2

在 Powershell 中使用 .Net 网络客户端。它可以工作，但没有任何进展，你不能通过 Ctrl+C 终止:(。最后一个问题是一个很大的挫折。

powershell -command "& { (New-Object System.Net.WebClient).DownloadFile('https://github.com/mitchellspryn/AirsimHighPolySuv/releases/download/V1.0.0/SUV.zip', 'SUV.zip') }"

尝试 3

在 Powershell 中使用 BITS 传输。它可以工作，显示进度并且几乎完美...直到您发现它mysteriously doesn't work on GitHub（禁止出现 403 错误）！！

powershell -command "& { Start-BitsTransfer -Source https://github.com/mitchellspryn/AirsimHighPolySuv/releases/download/V1.0.0/SUV.zip -Destination SUV.zip }"

Answer 1

经过一番研究，我发现@MichaelS 的方法最简单，但我添加了一些你可能会觉得有用的修改，例如：

1. 添加了Try/Finally 块，因此我们可以处理用户中断（Ctrl+C）和清理（参见Gracefully stopping in Powershell）
2. 利用Write-Progress功能，感觉更像Start-BitsTransfer
3. 缓冲区大小优化，至少针对我的特定连接/机器（参见https://www.microsoft.com/en-us/research/wp-content/uploads/2004/12/tr-2004-136.pdf，参见https://stackoverflow.com/a/3034155/10504393）

实际上它看起来像that gif。

function Get-FileFromURL {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory, Position = 0)]
        [System.Uri]$URL,
        [Parameter(Mandatory, Position = 1)]
        [string]$Filename
    )

    process {
        try {
            $request = [System.Net.HttpWebRequest]::Create($URL)
            $request.set_Timeout(5000) # 5 second timeout
            $response = $request.GetResponse()
            $total_bytes = $response.ContentLength
            $response_stream = $response.GetResponseStream()

            try {
                # 256KB works better on my machine for 1GB and 10GB files
                # See https://www.microsoft.com/en-us/research/wp-content/uploads/2004/12/tr-2004-136.pdf
                # Cf. https://stackoverflow.com/a/3034155/10504393
                $buffer = New-Object -TypeName byte[] -ArgumentList 256KB
                $target_stream = [System.IO.File]::Create($Filename)

                $timer = New-Object -TypeName timers.timer
                $timer.Interval = 1000 # Update progress every second
                $timer_event = Register-ObjectEvent -InputObject $timer -EventName Elapsed -Action {
                    $Global:update_progress = $true
                }
                $timer.Start()

                do {
                    $count = $response_stream.Read($buffer, 0, $buffer.length)
                    $target_stream.Write($buffer, 0, $count)
                    $downloaded_bytes = $downloaded_bytes + $count

                    if ($Global:update_progress) {
                        $percent = $downloaded_bytes / $total_bytes
                        $status = @{
                            completed  = "{0,6:p2} Completed" -f $percent
                            downloaded = "{0:n0} MB of {1:n0} MB" -f ($downloaded_bytes / 1MB), ($total_bytes / 1MB)
                            speed      = "{0,7:n0} KB/s" -f (($downloaded_bytes - $prev_downloaded_bytes) / 1KB)
                            eta        = "eta {0:hh\:mm\:ss}" -f (New-TimeSpan -Seconds (($total_bytes - $downloaded_bytes) / ($downloaded_bytes - $prev_downloaded_bytes)))
                        }
                        $progress_args = @{
                            Activity        = "Downloading $URL"
                            Status          = "$($status.completed) ($($status.downloaded)) $($status.speed) $($status.eta)"
                            PercentComplete = $percent * 100
                        }
                        Write-Progress @progress_args

                        $prev_downloaded_bytes = $downloaded_bytes
                        $Global:update_progress = $false
                    }
                } while ($count -gt 0)
            }
            finally {
                if ($timer) { $timer.Stop() }
                if ($timer_event) { Unregister-Event -SubscriptionId $timer_event.Id }
                if ($target_stream) { $target_stream.Dispose() }
                # If file exists and $count is not zero or $null, than script was interrupted by user
                if ((Test-Path $Filename) -and $count) { Remove-Item -Path $Filename }
            }
        }
        finally {
            if ($response) { $response.Dispose() }
            if ($response_stream) { $response_stream.Dispose() }
        }
    }
}

Answer 2

不知道我最初是从哪里得到这段代码的，但我已经修改了好几次。希望这会对你有所帮助。

function downloadFile($url, $targetFile)
{
    "Downloading $url"
    $uri = New-Object "System.Uri" "$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)
    {
        [System.Console]::CursorLeft = 0
        [System.Console]::Write("Downloaded {0}K of {1}K", [System.Math]::Floor($downloadedBytes/1024), $totalLength)
        $targetStream.Write($buffer, 0, $count)
        $count = $responseStream.Read($buffer,0,$buffer.length)
        $downloadedBytes = $downloadedBytes + $count
    }
    "Finished Download"
    $targetStream.Flush()
    $targetStream.Close()
    $targetStream.Dispose()
    $responseStream.Dispose()
}

downloadFile "http://URL_to_your_file" "C:\Path\to\destination.file"