Regular Expressions-Basic Knowledge

Regular expressions are used to match strings.

I. Matching mode text:

The regular expression's matching mode text usually includes the following content:

Metacharacters: special characters;

Metacharacters	Description
.	Match any character except linefeed
\ W	Match letters, numbers; C # also supports Chinese characters; equivalent to [a-zA-Z0-9]
\ W	In contrast to the above, matching non-digit letters; equivalent to [^ a-zA-Z0-9]
\ S	Match blank characters
\ S	On the contrary, non-blank characters are matched.
\ D	Matching number
\ D	In contrast, match non-Numbers
\ B	Match the start or end of a wordLocation
\ B	In contrast to the above, matching non-word start or endLocation
^	Start position of matching string
$	End position of matching string

 

Indicates the number of repetitions:

Category	Description
?	Indicates that the left part is repeated 0 times or 1 time.
*	Indicates that the left part is repeated 0 times or multiple times.
+	Indicates that the left part is repeated once or multiple times.
{Min, max}	Indicates that the left part is repeated for min to Max times.
{Min ,}	Indicates that the left part is repeated for at least min.
{Num}	Indicates that the part on the left is repeated for num times.

Indicates the group:

Category	Syntax	Description
Capture	(ABC)	Match ABC and capture the text to the automatically named group. Or, it indicates the pattern text applicable to repeated times,
	(? <Name> ABC)	Match exp and capture the text to the group named name. You can also write (? 'Name' exp)
	(? : ABC)	Match exp, no group number is assigned to the group, and no matching text is captured. However, group 0 is not affected.
Assertions	(? = ABC)	Match ABC, But ABC is not matched. That is, ABC must be followed by the text, but ABC is not obtained for group 0.
	(? <ABC)	If ABC is matched but ABC is not matched, the text must be preceded by ABC, but the group 0 does not get ABC.
	(?! ABC)	If the text to be matched is not followed by ABC, But ABC is not matched, group 0 does not get ABC.
	(? <! ABC)	If the text is not ABC before the match, but ABC is not matched, the ABC is not obtained for group 0.
Note	(? # Comment)	Note

 

Others:

Category	Description
[ABC]	Match any one of the ABC characters in the brackets (one character must be matched)
[^ ABC]	Match a character other than the characters in parentheses (one character must be matched)
|	Expression or; match | the previous mode or the subsequent mode
\ Char	Match special characters, such as \ * match *;\? Matching?

 

\ Num

Reverse reference

Indicates the text captured by the num capturing parentheses (the bracket count is calculated based on the order in which left parentheses appear. Note that nested parentheses are used)

 

Regular Expressions-Basic Knowledge