如何在 Powershell 中一次替换多个 .txt 文件中的数据？

Question

我在一个文件夹中有多个 .txt 文件，它们具有特定的数据格式，其中每一行都从 3 位数字开始，例如。

101,3333,35899,BufferC1,99,02,333
102,3344,30079,BufferD2,89,03,444
.... and so on.

现在，如果记录以“101”开头，那么我必须用一些文本替换同一行的第 3 和第 5 个索引元素。替换所有文件后，我必须将所有修改后的文件复制到同一台机器上的另一个目录/文件夹中。

我写了一些不工作的代码。请帮助我，因为我是 powershell 的新手。我的方法是否正确？

 $FileNamesList = @(Get-ChildItem C:\TestFiles\*.txt | Select-Object -ExpandProperty Name)
    
     for($i=0; $i -lt $FileNamesList.count; $i++)
        {      
            # original folder path
            $FilePath1 = 'C:\TestFiles\' + $FileNamesList[$i]
            
            #modified files after text is replaced will be copied in another folder
            $FilePath2 = 'C:\TestFilesModified\' + $FileNamesList[$i]   
    
            $OriginalFileData = Get-Content $FilePath1
    
        # Is this correct, can i assign foreach cmd result to a variable?
        $ModifiedFileData= ForEach($Row in $OriginalFileData ) 
                    {                 
                         If($Row.Split(",")[0] -eq "101") 
                         {
                            $Row -replace($Row.Split(",")[3]),"Test File"
                            $Row -replace($Row.Split(",")[5]),"Test Data"
                         } 

                     else{
                       $Row
                        }

             Out-File -FilePath $FilePath2 -InputObject $ModifiedFileData
            }

Answer 1

我喜欢@Theo's approach。我开始沿着同样的思路思考并编写类似的代码。但是，我对 CSV 的想法很感兴趣，最终找到了一些可供分享的替代方法。

CSV 方法存在一些问题：

1. 缺少标题
2. 难以重新导出，因为 Export-Csv 没有 -NoHeader 参数
3. 如 cmets 中所述处理可变数量的列

我的第一个方法是使用ConvertFrom-String cmdlet 从原始数据中获取正式对象。

$SourceFolder      = "C:\Temp\SourceFolder"
$DestinationFolder = "C:\Temp\destination"

ForEach( $File in Get-ChildItem $SourceFolder -Filter *.txt )
{
    $DestinationFile = Join-Path -Path $DestinationFolder -ChildPath $File.Name
    
    $File | 
    Get-Content | 
    ConvertFrom-String -Delimiter "," | 
    ForEach-Object{
        If( $_.P1 -eq 101 ) {
            $_.P3 = "P3 Replacement Value"
            $_.P5 = "P5 Replacement Value"
        }
        $_.PSObject.Properties.Value -join "," # Output from the loop
    } |
    Set-Content -Path $DestinationFile
}

这样做的好处是您不需要知道任何 1 个文件甚至给定文件的任何 1 行中有多少字段。 ConvertFrom-String 只会为给定的行添加额外的属性。使用 $_.PSObject.Properties.Value 展开值还允许使用有限代码的任意数量的属性。

第二种方法需要知道最大列数。出于示例的目的，假设我们有可变数量的列，但最多只能说 8 个。我们可以将 -Header 参数与 Import-Csv 命令一起使用。

$Header            = "P1","P2","P3","P4","P5","P6","P7","P8"
$SourceFolder      = "C:\Temp\SourceFolder"
$DestinationFolder = "C:\Temp\destination"

ForEach( $File in Get-ChildItem C:\temp\SourceFolder -filter *.txt )
{
    $DestinationFile = Join-Path -Path $DestinationFolder -ChildPath $File.Name
    
    Import-Csv -Path $File.FullName -Header $Header |
    ForEach-Object{
        If( $_.P1 -eq 101 ) {
            $_.P3 = "P3 Replacement Value"
            $_.P5 = "P5 Replacement Value"
        }
        ($_.PSObject.Properties.Value -join ",").TrimEnd(",") # Output from the loop
    } |
    Set-Content -Path $DestinationFile
}

注意：我想即使您不知道可以将大数组分配给 $Header 变量的最大字段数。

注意：.TrimEnd(",") 方法。由于给定行上的字段可能少于$Header 数组中的元素，Import-Csv 将添加一个属性并为其分配一个空值。反过来，这可能会导致-join 产生的字符串中出现额外的逗号。

警告：如果有合法的空尾随字段，这也可能会造成问题。

最后，我确实找到了一种进一步利用 *-Csv cmdlet 的方法，但它仅适用于 ConvertFrom-String 示例：

$SourceFolder      = "C:\Temp\SourceFolder"
$DestinationFolder = "C:\Temp\destination"

ForEach( $File in Get-ChildItem $SourceFolder -Filter *.txt )
{
    $DestinationFile = Join-Path -Path $DestinationFolder -ChildPath $File.Name
    
    $File | 
    Get-Content | 
    ConvertFrom-String -Delimiter "," | 
    ForEach-Object{
        If( $_.P1 -eq 101 ) {
            $_.P3 = "P3 Replacement Value"
            $_.P5 = "P5 Replacement Value"
        }
        $_
    } |
    ConvertTo-Csv -NoTypeInformation |
    Select-Object -Skip 1 |
    Set-Content -Path $DestinationFile
}

这不需要-join 表达式，但是它以额外的Select-Object 管道为代价。

Answer 2

很遗憾，这些文件没有标题，这将使它们成为正确的 Csv 文件，并且使用起来更加可靠..

您现在可以做的是逐行遍历这些文件并在分隔符 , 处拆分。

编辑

代码现在使用正则表达式来分割逗号上的每个字符串，除非这个逗号在带引号的字段内。

# create a regex string to split on the delimiter character ',' unless it isinside quotes
$commaUnlessQuoted = ',(?=(?:[^"]*"[^"]*")*[^"]*$)'
Get-ChildItem -Path 'D:\Test'-Filter '*.txt' -File | ForEach-Object {
    $file = $_.FullName
    $data = switch -Regex -File $file {
        '^101,' {
            # first field is '101', replace element index 3 with "Test File" and element index 5 with "Test Data"
            $fields = $_ -split $commaUnlessQuoted
            $fields[3] = "Test File"
            $fields[5] = "Test Data"
            # rejoin the fields with a comma
            $fields -join ','
        }
        '^002,' {
            # first field is '002', replace element index 3 with the current date
            $fields = $_ -split $commaUnlessQuoted
            $fields[3] = (Get-Date).ToLongDateString()
            $fields -join ','
        }
        # you can add as many regex conditions here as you like.
        # default means no conditions above matched, so return te line as-is
        default {$_}
    }
    $data | Set-Content -Path $file -Force
    # copy the modified file to somewhere else
    Copy-Item -Path $file -Destination 'C:\TestFilesModified'
}

$commaUnlessQuoted 的正则表达式详细信息：

,               Match the character “,” literally
(?=             Assert that the regex below can be matched, starting at this position (positive lookahead)
   (?:          Match the regular expression below
      [^"]      Match any character that is NOT a “"”
         *      Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
      "         Match the character “"” literally
      [^"]      Match any character that is NOT a “"”
         *      Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
      "         Match the character “"” literally
   )*           Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
   [^"]         Match any character that is NOT a “"”
      *         Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
   $            Assert position at the end of the string (or before the line break at the end of the string, if any)
)

---

根据您对this question 的评论，如果您还需要抛出非终止异常，只需更改以下几行：

$data | Set-Content -Path $file -Force
# copy the modified file to somewhere else
Copy-Item -Path $file -Destination 'C:\TestFilesModified'

进入

try {
    $data | Set-Content -Path $file -Force -ErrorAction Stop
    # copy the modified file to somewhere else
    Copy-Item -Path $file -Destination 'C:\TestFilesModified' -ErrorAction Stop
}
catch { throw }  # just rethrow the exception so it 'bubbles up' to the calling script