当前位置：网站首页>regular expression

regular expression

2022-07-07 12:57:00 【LC181119】

1. Basic regular expression metacharacters

1.1 Character matching

. Match any single character , It can be a Chinese character
[] Match any single character in the specified range
[^] Matches any single character outside the specified range
[:alnum:] Represents any upper and lower case letters in English
[:lower:] Lowercase letters
[:upper:] Capital
[:blank:] Blank character （ Spaces and tabs ）
[:space:] Including Spaces 、 tabs （ Horizontal or vertical ）、 A newline 、 Various types of whitespace such as carriage return
[:cntrl:] Non printable control characters （ Backspace 、 Delete 、 Alarm bell ...）
[:digit:] Decimal number
[:xdigit:] Hexadecimal number
[:graph:] Printable non blank characters
[:print:] Printable characters
[:punct:] Punctuation
\w Components of matching words , Equivalent to [_[:alnum:]]
\W Match non word components , Equivalent to [^_[:alnum:]]
\S Matches any non-whitespace characters , Equivalent to [^ \f\n\r\t\v]
\s Matches any whitespace characters , Including Spaces 、 tabs 、 Page breaks and so on , amount to [ \f\n\r\t\v].

Be careful ：unicode Regular expressions match full space characters .

1.2 Number of matches

Used after the character to specify the number of times , Used to specify the number of times the preceding characters will appear

* Match preceding characters any number of times , Include 0 Time , Greedy mode , Match as long as possible
.* Any character of any length
\? Match the character before it to appear 0 Time or 1 Time , namely ： not essential
\+ Matches the least characters that precede it 1 Time , namely ： There must be and >=1 Time
\{n\} Match preceding characters n Time
\{m,n\} Match preceding characters at least m Time , at most n Time
\{,n\} Match preceding characters up to n Time ,<=n
\{n,\} Match preceding characters at least n Time

1.3 Position anchoring

^ Anchor anchoring , Leftmost rule for mode
$ Tail anchoring , For the far right side of the pattern
^PATTERN$ For pattern matching entire line
^$ Blank line
^[[:space:]]*$ Blank line
\< or \b Initial anchoring , For the left side of the word pattern
\> or \b Suffix anchor , For the right side of the word pattern
\<PATTERN> Match the whole word

1.4 grouping

grouping ：() Binding multiple characters together , Treat it as a whole , Such as ：$root$+

Backward reference ： The matching contents of the patterns in grouping brackets will be recorded in the internal variables by the regular expression engine , The names of these variables The way is : \1, \2, \3, ...

\1 Represents the character to which the pattern between the first open bracket from the left and the matching right bracket matches

1.5 perhaps

perhaps ：\|

2. Extended regular expression metacharacter

2.1 Character matching

. Match any single character , It can be a Chinese character
[] Match any single character in the specified range
[^] Matches any single character outside the specified range
[:alnum:] Represents any upper and lower case letters in English
[:lower:] Lowercase letters
[:upper:] Capital
[:blank:] Blank character （ Spaces and tabs ）
[:space:] Including Spaces 、 tabs （ Horizontal or vertical ）、 A newline 、 Various types of whitespace such as carriage return
[:cntrl:] Non printable control characters （ Backspace 、 Delete 、 Alarm bell ...）
[:digit:] Decimal number
[:xdigit:] Hexadecimal number
[:graph:] Printable non blank characters
[:print:] Printable characters
[:punct:] Punctuation