Table of contents
Just wrote some basic
1. Metacharacters
Metacharacters: characters with specific meanings, common metacharacters are as follows
Common Metacharacters
| the code | illustrate | example |
| . | matches any character except newline |
1，n,*+ |
| \w | Match letters or numbers or underscores or Chinese characters | \w:a,1,_ |
| \s | matches any whitespace | |
| \d | matches any number | ^\d\d\d$:123,456,753 |
| \b | start and end of any word | |
| ^ | match the beginning of the string | |
| $ | matches the end of the string |
Two, antonyms
Antonym characters: mostly used to find any character except a certain character
Commonly used antonyms are as follows:
| the code | illustrate | example |
| \W | Match any character other than letters, numbers, underscores, and Chinese characters | +，- |
| \S | matches any character that is not a whitespace character | |
| \D | matches any character that is not a number | s,. |
| \B | Matches a position that is not the beginning or end of a word | |
| [^x] | matches any character except x | [a]:b,s,c........ |
Three, limited characters
Limit characters are mostly used for repeated matching times
Commonly used limit characters are as follows
| the code | illustrate | example |
| * | Repeat zero or more times | \d*: 0 or more times of numbers, such as 2, 3, 44, 555,, 4.... |
| + | repeat one or more times | \d+：1，11，222，333... |
| ？ | Repeat zero or one time | \d?:1，，3 |
| {n} | repeat n times | \d{2}:11,22,33,44 |
| {n.} | Repeat n or more times | \d{3}:333,111,1111,55555 |
| {n,m} | Repeat nm times | \d{3,4}111,1111,222,2222 |
4. Escape characters
In actual development, you may encounter a situation where you need to match metacharacters. At this time, you need to perform character escaping, such as metacharacters. * \ needs to be converted to \. \* \\
5. Character branches
Character branches are mostly used to meet the selection of different situations, use "|" to separate different conditions
The qq number is ten or eleven digits:
\d{10}|\d{11}
Six, character grouping
Character grouping is mostly used to repeat multiple characters, mainly by using parentheses () to group
(\d\w){3} repeat match 3 times (\d\w)