powershell 取文件末尾行（ascill)

最新推荐文章于 2025-06-27 11:09:34 发布

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最新推荐文章于 2025-06-27 11:09:34 发布

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原文链接：http://www.cnblogs.com/zhaojun20002003/archive/2010/12/16/1908324.html

这是一个PowerShell函数，用于获取文件的最后几行。它遍历文件从后向前，仅适用于ASCII编码的文件。文章展示了如何使用该函数并提供了示例。

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powershell 取文件末尾行（ascill)

function Tail-Content([string[]] $Path,[int] $Last = 10,[string]$Newline=[Environment]::NewLine)
{

$fs = $null
$resolvedPaths = $Path
foreach ($rpath in $resolvedPaths)
{
     $numLines = $Last
     $seekOffset = -1;
     $PathIntrinsics = $ExecutionContext.SessionState.Path
     if ($PathIntrinsics.IsProviderQualified($rpath))
     {
        $rpath = $PathIntrinsics.GetUnresolvedProviderPathFromPSPath($rpath)
     }
     Write-Verbose "Tail-Content processing $rpath"
     $lines = New-Object 'System.Collections.Generic.List`1[System.String]'
     $line = New-Object "System.Text.StringBuilder"
     $newlineIndex = $Newline.Length - 1
     $fs = New-Object "System.IO.FileStream" $rpath,"Open","Read"
     while ($numLines -gt 0 -and ($fs.Length + $seekOffset -ge 0))
     {
           [void]$fs.Seek($seekOffset--, "End")
           $ch = $fs.ReadByte()
           if ($ch -eq 0 -or $ch -gt 127)
           {
               #throw "Tail-Content only works on ASCII encoded files"
           }
           # Chew up line termination characters
           if ($ch -eq $Newline[$newlineIndex])
           {
               if (--$newlineIndex -lt 0)
                {
                    $newlineIndex = $Newline.Length - 1
                    # Ignore the newline at the end of the file
                    if ($seekOffset -lt -($Newline.Length + 1))
                    {
                            $lines.Insert(0, $line.ToString())
                            $line = New-Object "System.Text.StringBuilder"
                            $numLines--
                     }
                 }
                    continue
            }
            [void]$line.Insert(0, [char]$ch)
      }
      if ($line.Length -gt 0)
      {
          $lines.Insert(0, $line.ToString())
      }
      $lines
      if ($fs) { $fs.Close() }
}
}

cls
cd "FileSystem::C:\archived\self\task\powershell\test"
$file ="FileSystem::C:\archived\self\task\powershell\test\OtherEnconding.txt"
#$file ="984MB.txt"
Tail-Content $file