The knowledge carding of regular expressions

First put a URL: https://regexper.com/

This tool is used to help understand regular expressions and is useful when you are reading regular expressions.

Metacharacters

Non-alphabetic characters that have special meanings. Includes: * +? ^ $ . | \ () [] {} , if you can say the meaning of these symbols at once, it means that the basis of the regular expression is mastered.

[]: Used to match a class of Word character;

[^]:[^ indicates that this type of character is not included. The ^ in brackets indicates the meaning of inversion;

[-]: Inside the brackets - meaning of the range.

. : matches all characters.

\d: Match all the numbers;

\d: Matches all non-numbers;

\s: Matches all whitespace characters (space carriage return line)

\s: Matches all non-whitespace characters;

\w: Match alphanumeric underline;

\w: Matches a character other than a non-alphanumeric underscore.

\b: Match word boundaries;

\b: Matches the non-word boundary;

^: match the beginning;

$: Match end;

?: The preceding character is modified to indicate a maximum of 1 occurrences;

+: Modifies the preceding character to indicate a minimum occurrence of 1 occurrences;

*: Modify the preceding character, indicating that it can appear any time;

{n}: Modifies the preceding character, indicating that n times occurs;

{N,}: Indicates at least n occurrences;

{n,m}: Indicates the occurrence of N to M times; The default is greedy mode, as many matches as possible;

{n,m?} : Non-greedy mode, once the match succeeds can no longer match backwards:

(): Grouping to enable quantifiers to act on a set ofcharacters; \ n: Represents the contents of the captured packet (reverse reference);

An expression or meaning; Example:red| Blue matches Red or blue; Example:bl (ue|ack) matches Blue or black;

(? =\d): Assert, modify the preceding character, indicating not only to match the preceding regular content, but also to match the content of the assertion, the assertion part is only verified, not calculated;

The knowledge carding of regular expressions