regex - 跳过高性能 Powershell 正则表达式脚本 block 中的标题行

Question

我从 Stack Overflow 那里得到了一些惊人的帮助……但是……太神奇了，我需要更多的帮助才能更接近终点线。我每月 2 次解析多个巨大的 4GB 文件。我需要能够跳过标题、计算总行数、匹配行和不匹配行。我确信这对于 PowerShell super 巨星来说非常简单，但在我的新手 PS 水平上，我的技能还不强。也许你的一点帮助可以节省一周的时间。 :)

数据样本:

ID         FIRST_NAME              LAST_NAME          COLUMN_NM_TOO_LON5THCOLUMN
 10000000001MINNIE                 MOUSE              COLUMN VALUE LONGSTARTS 
 10000000002MICKLE ROONEY          MOUSE              COLUMN VALUE LONGSTARTS 

代码块(基于 this answer ):

#$match_regex matches each fixed length field by length; the () specifies that each matched field be stored in a capture group:
[regex]$match_regex = '^(.{10})(.{50})(.{50})(.{50})(.{50})(.{3})(.{8})(.{4})(.{50})(.{2})(.{30})(.{6})(.{3})(.{4})(.{25})(.{2})(.{10})(.{3})(.{8})(.{4})(.{50})(.{2})(.{30})(.{6})(.{3})(.{2})(.{25})(.{2})(.{10})(.{3})(.{10})(.{10})(.{10})(.{2})(.{10})(.{50})(.{50})(.{50})(.{50})(.{8})(.{4})(.{50})(.{2})(.{30})(.{6})(.{3})(.{2})(.{25})(.{2})(.{10})(.{3})(.{4})(.{2})(.{4})(.{10})(.{38})(.{38})(.{15})(.{1})(.{10})(.{2})(.{10})(.{10})(.{10})(.{10})(.{38})(.{38})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})(.{10})$'

Measure-Command {
        & { 
          switch -File $infile -Regex  {
            $match_regex {
               # Join what all the capture groups matched with a tab char.
               $Matches[1..($Matches.Count-1)].Trim() -join "`t"
            }
          }
        } | Out-File $outFile
}

Answer 1

您只需要跟踪两个计数 - 匹配的行和不匹配的行 - 然后是一个 bool 值来指示您是否跳过了第一行

$first = $false
$matched = 0
$unmatched = 0
. {
    switch -File $infile -Regex  {
        $match_regex {
            if($first){
                # Join what all the capture groups matched with a tab char.
                $Matches[1..($Matches.Count-1)].Trim() -join "`t"
                $matched++
            }
            $first = $true
        }
        default{
            $unmatched++
            # you can remove this, if the pattern always matches the header
            $first = $true
        }
    }
} | Out-File $outFile

$total = $matched + $unmatched