powershell@字符串修改/替换字符串@抽取markdown中的各级标题大纲

文章目录

• powershell 处理字符串
• • demos
  • • 替换第一个空格为等号
    • 实例:替换掉第一个dall($)符号
    • 实例:调整数字序列字符串
    • 学习过程
• 字符串相关操作符
• • - split
  • • 将指定的多种字符作为分隔符
  • -contains@-match
  • • 通配符和正则表达式
  • Replacement
  • • -replace 操作符
  • 应用:抽取markdown中的各级标题
• refs

powershell 处理字符串

demos

替换第一个空格为等号

• 方法1:

  $string = "abc def gh"
  $index = $string.IndexOf(' ')
  if ($index -ge 0) {
      $string = $string.Remove($index, 1).Insert($index, '=')
  }

• 方法2:(使用正则替换,注意使用分组引用,使用单引号而不应该使用双引号)

  $string -replace "(^.*?) ", '$1='
  #或
  $string -replace "^(.*?)\s(.*)", '$1=$2'
  #或全部用单引号
  $string -replace '^(.*?)\s(.*)', '$1=$2'

实例:替换掉第一个dall($)符号

PS D:\repos\blogs> '$abc=$env;othercontent' -replace '(\$)(.*)','$global:$2'
#结果:
$global:abc=$env;othercontent
 

实例:调整数字序列字符串

• 本例中需要小心backreference 引用变量$1和字符2在书写模板的时候需要区分;通过${1}来避免$1字符2被解读为$12,这将造成意外的效果

PS D:\repos\blogs> "1 1 1 3 3 1 3 1 3" -replace '(.*?1.*?1.*?)1(.*)', '${1}2$2'
1 1 2 3 3 1 3 1 3
 
 
PS D:\repos\blogs> "1 1 1 3 3 1 3 1 3" -replace '(.*?1.*?1.*?)1(.*)', '$12$2'
$12 3 3 1 3 1 3

学习过程

PS C:\Users\cxxu> help "-replace"
 
Name                              Category  Module                    Synopsis
----                              --------  ------                    --------
Rename-Item                       Cmdlet    Microsoft.PowerShell.Man… Renames an item in a PowerShell provider namespa…
Set-Content                       Cmdlet    Microsoft.PowerShell.Man… Writes new content or replaces existing content …
Get-Date                          Cmdlet    Microsoft.PowerShell.Uti… Gets the current date and time.
about_Comparison_Operators        HelpFile
about_Operators                   HelpFile
about_Operator_Precedence         HelpFile
about_Regular_Expressions         HelpFile
about_Mocking                     HelpFile                            Pester provides a set of Mocking functions makin…
about_Pester                      HelpFile                            Pester is a BDD based test runner for PowerShell.
 
PS C:\Users\cxxu> help about_Operators| sls   -Pattern "replace"
InputStream:51:The comparison operators also include operators that find or replace
InputStream:52:patterns in text. The (-match, -notmatch, -replace) operators use regular
InputStream:473:You can use the ternary operator as a replacement for the if-else statement
 
PS C:\Users\cxxu> help about_Regular_Expressions |sls -Pattern "-replace"
InputStream:26:-   -match and -replace operators
InputStream:328:Using the regular expressions with the -replace operator allows you to
InputStream:331:<input> -replace <original>, <substitute>
InputStream:348:        'John D. Smith' -replace '(\w+) (\w+)\. (\w+)', '$1.$2.$3@contoso.com'
InputStream:354:        'CONTOSO\Administrator' -replace '\w+\\(?<user>\w+)', 'FABRIKAM\${user}'
InputStream:360:    'Gobble' -replace 'Gobble', '$& $&'
InputStream:368:      'Hello World' -replace '(\w+) \w+', '$1 Universe'
InputStream:369:      "Hello World" -replace "(\w+) \w+", "`$1 Universe"
InputStream:378:      '5.72' -replace '(.+)', '$$$1'
InputStream:379:      "5.72" -replace "(.+)", "`$`$`$1"
 

• 经过上述查找,我们可以到about_Regular_Expressions 中一探究竟.

字符串相关操作符

• 这些操作符大多支持对字符串元素和字符串构成的数组进行操作(后者相当于自动遍历)

- split

• about Split - PowerShell | Microsoft Learn

将指定的多种字符作为分隔符

• PS D:\repos\scripts> $s='test_b test b'
  PS D:\repos\scripts> $s -split {$_ -eq " " -or $_ -eq "="},2
  test_b
  test b

-contains@-match

• containment-operators|about Comparison Operators - PowerShell | Microsoft Learn

• matching-operators|about Comparison Operators - PowerShell | Microsoft Learn

• PS D:\repos\scripts> $s='test_b test b' 
  PS D:\repos\scripts> $s -contains ' ' 
  False
  PS D:\repos\scripts> $s -match '\s'
  True
  PS D:\repos\scripts> $s.contains(' ')
  True

• The -contains operator in PowerShell checks if a collection of objects contains a specified object.

• In the example you provided, $s is a string, not a collection of objects. Therefore, the -contains operator will not work as expected. Instead, you can use the -match operator with a regular expression to check if the string contains a space.

• For example, if you want to check if the string “test_b test b” contains a space, you can use the following code: "test_b test b" -match '\s'. This will return True if the string contains a space and False otherwise.

通配符和正则表达式

• about Comparison Operators - PowerShell | Microsoft Learn

• The matching operators (-like, -notlike, -match, and -notmatch) find elements that match or don’t match a specified pattern.

  • The pattern for -like and -notlike is a wildcard expression (containing *, ?, and [ ]),
  • while -match and -notmatch accept a regular expression (Regex).

• 语法

  • <string[]> -like    <wildcard-expression>
    <string[]> -notlike <wildcard-expression>
    <string[]> -match    <regular-expression>
    <string[]> -notmatch <regular-expression>

Replacement

• -replace, -ireplace, -creplace - replaces strings matching a regex pattern
• about Comparison Operators - PowerShell | Microsoft Learn

-replace 操作符

• powershell 提供了不少处理字符串的方法,其中我认为最为通用,也最为强大的是 -replace操作符

• -replace 配合正则表达式可以对字符串做丰富的处理

• String.replace()函数不如 -replace灵活

• 尤其是分组捕获的部分,利用了模板操作的思想,在调整字符串方面表现的十分出色

应用:抽取markdown中的各级标题

• 这个powershell函数可以作为模块调用,通常用不到,相关软件多有目录和大纲功能

• 但是在命令行终端中抽取文章摘要比较有用

  function extract_markdown_titiles
  {
      <# 
      .synopsis
      extract markdown titles,configs like 
          1.level
          2.indent char
          3.show title text only 
      are available to specifiy.
   
      .example
      PS D:\> extract_markdown_titiles .\01_导数和微分.md -level 2 -indent_with_chr '*'
      * 一元函数微分
      ** 函数在$x=x_0$导数的定义
      ** 导函数的定义
      ** 导数与微分@微商
      ** 对数函数的导函数
      ** 函数间四则运算组合函数的求导法则
      ** 反函数求导法则
      ** 对数求导法
      ** 微积分和深度学习
      * 导数表示法&导数记号系统
      ** 莱布尼兹记号法@Leibniz's notation
      ** 拉格朗日记号法@Lagrange's notation
      ** 欧拉记号法@Euler's notation
      ** 牛顿记号Newton's notation
   
      #>
      param(
          $file,
          $level = 3,
          $indent_with_chr = '#',
          # copy result to clipborad
          $scb = $true,
          [switch]$title_only 
      )
      # Write-Output $level
      
      # $pattern = '^(#+)(\s+)(\S+)'
      $pattern = '^(#+)(\s+)(.*)'
      $titles_with_level = Get-Content $file | Where-Object { $_ -match $pattern } 
      # Remove potential excess spaces as they can affect aesthetics 
      # in titles "##[ ]<title content>",the '[]' indicate the space character width
      $titles_with_level = $titles_with_level -replace $pattern, '$1 $3'
   
      $titles_leveled = $titles_with_level | ForEach-Object {
          $titles_sharps = $_ -replace $pattern, '$1' 
          # Write-Output "'$titles_sharps'"
          $title_level = $titles_sharps.Length
   
          # Write-Output "$title_level;$_"
   
          if ($title_level -gt $level)
          {
              return
          }
          else
          {
              # 在管道符中通过write的方式将被遍历的元素添加到数组中
              Write-Output $_
   
          }
      }
   
      # Write-Output $titles_leveled
      
      $titles_with_level = $titles_leveled
   
      $titles = $titles_with_level | ForEach-Object { $_ -replace $pattern, '$3' }
      $res = ""
      if ($title_only)
      {
          $res = $titles
      }
      elseif ($indent_with_chr -eq "#")
      {
          
          $res = $titles_with_level
      }
      else
      {
          $res = $titles_with_level | ForEach-Object {
              $title_level = ( $_ -replace $pattern, '$1' ).Length
              $_ -replace "^(#+)", ($indent_with_chr * $title_level)
          }
      }
      # 根据需要将内容自动复制到剪切板
      if ($scb)
      {
          $res | Set-Clipboard
   
      }
      return $res 
      
  }

• 用例

      .example
      PS D:\> extract_markdown_titiles .\01_导数和微分.md -level 2 -indent_with_chr '='
      = 一元函数微分
      == 函数在$x=x_0$导数的定义
      == 导函数的定义
      == 导数与微分@微商
      == 对数函数的导函数
      == 函数间四则运算组合函数的求导法则
      == 反函数求导法则
      == 对数求导法
      == 微积分和深度学习
      = 导数表示法&导数记号系统
      == 莱布尼兹记号法@Leibniz's notation
      == 拉格朗日记号法@Lagrange's notation
      == 欧拉记号法@Euler's notation
      == 牛顿记号Newton's notation
   
      .example
      PS D:\> extract_markdown_titiles .\01_导数和微分.md -level 2 -indent_with_chr '=='
      == 一元函数微分
      ==== 函数在$x=x_0$导数的定义
      ==== 导函数的定义
      ==== 导数与微分@微商
      ==== 对数函数的导函数
      ==== 函数间四则运算组合函数的求导法则
      ==== 反函数求导法则
      ==== 对数求导法
      ==== 微积分和深度学习
      == 导数表示法&导数记号系统
      ==== 莱布尼兹记号法@Leibniz's notation
      ==== 拉格朗日记号法@Lagrange's notation
      ==== 欧拉记号法@Euler's notation
      ==== 牛顿记号Newton's notation
   
      .example
      PS D:\> extract_markdown_titiles .\01_导数和微分.md -level 2 -indent_with_chr '===='
      ==== 一元函数微分
      ======== 函数在$x=x_0$导数的定义
      ======== 导函数的定义
      ======== 导数与微分@微商
      ======== 对数函数的导函数
      ======== 函数间四则运算组合函数的求导法则
      ======== 反函数求导法则
      ======== 对数求导法
      ======== 微积分和深度学习
      ==== 导数表示法&导数记号系统
      ======== 莱布尼兹记号法@Leibniz's notation
      ======== 拉格朗日记号法@Lagrange's notation
      ======== 欧拉记号法@Euler's notation
      ======== 牛顿记号Newton's notation
   
      .example
      PS D:\> extract_markdown_titiles .\01_导数和微分.md -level 2 -indent_with_chr '====' -title_only
      一元函数微分
      函数在$x=x_0$导数的定义
      导函数的定义
      导数与微分@微商
      对数函数的导函数
      函数间四则运算组合函数的求导法则
      反函数求导法则
      对数求导法
      微积分和深度学习
      导数表示法&导数记号系统
      莱布尼兹记号法@Leibniz's notation
      拉格朗日记号法@Lagrange's notation
      欧拉记号法@Euler's notation
      牛顿记号Newton's notation

refs

• replacement-with-regular-expressions|about Comparison Operators - PowerShell | Microsoft Learn
• about Regular Expressions - PowerShell | Microsoft Learn
• about Comparison Operators - PowerShell | Microsoft Learn
• How to Use PowerShell Replace to Replace Text [Examples] (adamtheautomator.com)
• Powershell - Replace first occurrences of String - Stack Overflow