文章目录



powershell_ modify String_ 字符串修改/替换字符串

references

powershell 处理字符串的方法

  • 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

相关语法(-replace & regex)

Using the regular expressions with the -replace operator allows you to
dynamically replace text using captured text.

<input> -replace <original>, <substitute>

-   <input>: The string to be searched
-   <original>: A regular expression used to search the input string
-   <substitute>: A regular expression substitution expression to replace
    matches found in the input string.

  [!NOTE] The <original> and <substitute> operands are subject to rules of
  the regular expression engine such as character escaping.

Capturing groups can be referenced in the <substitute> string. The
substitution is done by using the $ character before the group identifier.

Two ways to reference capturing groups are by NUMBER and by NAME.

-   By NUMBER - Capturing Groups are numbered from left to right.

        'John D. Smith' -replace '(\w+) (\w+)\. (\w+)', '$1.$2.$3@contoso.com'

        John.D.Smith@contoso.com

-   By NAME - Capturing Groups can also be referenced by name.

        'CONTOSO\Administrator' -replace '\w+\\(?<user>\w+)', 'FABRIKAM\${user}'

        FABRIKAM\Administrator

The $& expression represents all the text matched.

    'Gobble' -replace 'Gobble', '$& $&'

    Gobble Gobble

  [!WARNING] Since the $ character is used in string expansion, you'll need
  to use literal strings with substitution, or escape the $ character when
  using double quotes.

      'Hello World' -replace '(\w+) \w+', '$1 Universe'
      "Hello World" -replace "(\w+) \w+", "`$1 Universe"

      Hello Universe
      Hello Universe

  Additionally, if you want to have the $ as a literal character, use $$
  instead of the normal escape characters. When using double quotes, still
  escape all instances of $ to avoid incorrect substitution.

      '5.72' -replace '(.+)', '$$$1'
      "5.72" -replace "(.+)", "`$`$`$1"

      $5.72
      $5.72

For more information, see Substitutions in Regular Expressions.

实例:替换掉第一个dallar($)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powershell_ modify String_ 字符串修改/替换字符串(基于正则表达式)_linux{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.