關於這四個正則表達式之間的細微差別

學習正則表達式時，我曾經看到以下四個例子。我如何理解他們的差異？關於這四個正則表達式之間的細微差別

/ABC (?i:s) XYZ/ 
/ABC (?x: [A-Z] \.? \s)?XYZ/ 
/ABC (?ix: [A-Z] \.? \s)?XYZ/ 
/ABC (?x-i: [A-Z] \.? \s)?XYZ/i

什麼的i和x標誌是什麼意思？

來源

2012-02-07 user785099

哪部分你不明白？ – ikegami 2012-02-07 22:06:27

這些都很簡單。快速瀏覽documentation會回答你的問題。您可能還會發現YAPE::Regex::Explain有用。

$ perl -MYAPE::Regex::Explain -e' 
    print YAPE::Regex::Explain->new($_)->explain 
     for 
     qr/ABC (?i:s) XYZ/, 
     qr/ABC (?x: [A-Z] \.? \s)?XYZ/, 
     qr/ABC (?ix: [A-Z] \.? \s)?XYZ/, 
     qr/ABC (?x-i: [A-Z] \.? \s)?XYZ/i; 
'

The regular expression: 

(?-imsx:ABC (?i:s) XYZ) 

matches as follows: 

NODE      EXPLANATION 
---------------------------------------------------------------------- 
(?-imsx:     group, but do not capture (case-sensitive) 
         (with^and $ matching normally) (with . not 
         matching \n) (matching whitespace and # 
         normally): 
---------------------------------------------------------------------- 
    ABC      'ABC ' 
---------------------------------------------------------------------- 
    (?i:      group, but do not capture (case- 
          insensitive) (with^and $ matching 
          normally) (with . not matching \n) 
          (matching whitespace and # normally): 
---------------------------------------------------------------------- 
    s      's' 
---------------------------------------------------------------------- 
)      end of grouping 
---------------------------------------------------------------------- 
    XYZ      ' XYZ' 
---------------------------------------------------------------------- 
)      end of grouping 
----------------------------------------------------------------------

The regular expression: 

(?-imsx:ABC (?x: [A-Z] \.? \s)?XYZ) 

matches as follows: 

NODE      EXPLANATION 
---------------------------------------------------------------------- 
(?-imsx:     group, but do not capture (case-sensitive) 
         (with^and $ matching normally) (with . not 
         matching \n) (matching whitespace and # 
         normally): 
---------------------------------------------------------------------- 
    ABC      'ABC ' 
---------------------------------------------------------------------- 
    (?x:      group, but do not capture (disregarding 
          whitespace and comments) (case-sensitive) 
          (with^and $ matching normally) (with . 
          not matching \n) (optional (matching the 
          most amount possible)): 
---------------------------------------------------------------------- 
    [A-Z]     any character of: 'A' to 'Z' 
---------------------------------------------------------------------- 
    \.?      '.' (optional (matching the most amount 
          possible)) 
---------------------------------------------------------------------- 
    \s      whitespace (\n, \r, \t, \f, and " ") 
---------------------------------------------------------------------- 
)?      end of grouping 
---------------------------------------------------------------------- 
    XYZ      'XYZ' 
---------------------------------------------------------------------- 
)      end of grouping 
----------------------------------------------------------------------

The regular expression: 

(?-imsx:ABC (?ix: [A-Z] \.? \s)?XYZ) 

matches as follows: 

NODE      EXPLANATION 
---------------------------------------------------------------------- 
(?-imsx:     group, but do not capture (case-sensitive) 
         (with^and $ matching normally) (with . not 
         matching \n) (matching whitespace and # 
         normally): 
---------------------------------------------------------------------- 
    ABC      'ABC ' 
---------------------------------------------------------------------- 
    (?ix:     group, but do not capture (case- 
          insensitive) (disregarding whitespace and 
          comments) (with^and $ matching normally) 
          (with . not matching \n) (optional 
          (matching the most amount possible)): 
---------------------------------------------------------------------- 
    [A-Z]     any character of: 'A' to 'Z' 
---------------------------------------------------------------------- 
    \.?      '.' (optional (matching the most amount 
          possible)) 
---------------------------------------------------------------------- 
    \s      whitespace (\n, \r, \t, \f, and " ") 
---------------------------------------------------------------------- 
)?      end of grouping 
---------------------------------------------------------------------- 
    XYZ      'XYZ' 
---------------------------------------------------------------------- 
)      end of grouping 
----------------------------------------------------------------------

The regular expression: 

(?i-msx:ABC (?x-i: [A-Z] \.? \s)?XYZ) 

matches as follows: 

NODE      EXPLANATION 
---------------------------------------------------------------------- 
(?i-msx:     group, but do not capture (case-insensitive) 
         (with^and $ matching normally) (with . not 
         matching \n) (matching whitespace and # 
         normally): 
---------------------------------------------------------------------- 
    ABC      'ABC ' 
---------------------------------------------------------------------- 
    (?x-i:     group, but do not capture (disregarding 
          whitespace and comments) (case-sensitive) 
          (with^and $ matching normally) (with . 
          not matching \n) (optional (matching the 
          most amount possible)): 
---------------------------------------------------------------------- 
    [A-Z]     any character of: 'A' to 'Z' 
---------------------------------------------------------------------- 
    \.?      '.' (optional (matching the most amount 
          possible)) 
---------------------------------------------------------------------- 
    \s      whitespace (\n, \r, \t, \f, and " ") 
---------------------------------------------------------------------- 
)?      end of grouping 
---------------------------------------------------------------------- 
    XYZ      'XYZ' 
---------------------------------------------------------------------- 
)      end of grouping 
----------------------------------------------------------------------

來源

2012-02-07 22:14:38 ikegami

-1

/EXPR/標誌適用標誌到EXPR。

(?標誌:的Subexpr )適用標誌到的Subexpr。

i設置爲忽略大小寫，x設置爲忽略正則表達式主體中的空白。

更多詳細信息請登錄www.regular-expressions.info。

來源

2012-02-07 22:03:57 yarek

噢，'*（？：flags）*中的'-i'會打開區分大小寫的匹配項（禁用'/ i'）。 – tripleee 2012-02-07 22:11:44

@yarek，我們試圖在SO這裏保持一定的文明程度，更不用說樂於助人。 Terse，極簡主義的回答是不鼓勵的，並且像RTFM和LMGTFY這樣公然無禮的言論是被禁止的。 – 2012-02-08 00:07:18

關於這四個正則表達式之間的細微差別

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