基本知识

 

（1）Matching any character：.

. matches any character(任何字符，包含 space与 _), alphabetic characters(文字字符), digits(数字字符), and even . itself （.本身） 

 

The (?s) flag turns on "dot all" mode, allowing the dot character to match anything, including end-of-line characters. It is useful if you are matching patterns that span multiple lines. The s stands for "single-line mode," a somewhat confusing name derived from Perl.

 

 

如果不是使用(?s) 模式

 

 

.是不匹配 end-of-line characters 字符的！

 

 

（2）Matching Whitespace or nonwhitespace character: /s, /S

Table 4.4. Whitespace Metacharacters

Metacharacter	Description
/s	Any whitespace character (same as [/f/n/r/t/v])
/S	Any nonwhitespace character (same as [^/f/n/r/t/v])

Note：[/b], the backspace metacharacter, is not included in /s or excluded by /S.

 

（3）Matching  Digits

Digit Metacharacters

Metacharacter	Description
/d	Any digit (same as [0-9])
/D	Any nondigit (same as [^0-9])

（4）Matching  Alphanumeric characters

Table 4.3. Alphanumeric Metacharacters

Metacharacter	Description
/w	Any alphanumeric character in upper- or lower-case and underscore (same as [a-zA-Z0-9_])
/W	Any nonalphanumeric or underscore character (same as [^a-zA-Z0-9_])

 

Note：Whitespace Metacharacters

Table 4.1. Whitespace Metacharacters

Metacharacter	Description
[/b]	Backspace
/f	Form feed
/n	Line feed
/r	Carriage return
/t	Tab
/v	Vertical tab