Example Analysis of regular expression
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-^ and $are used to match the beginning and end of a string, respectively. Example 1 ^ must start with a "" string Example 2$ must end with a string of "". Example 3 ^ abc$ begins with abc and ends with abc. In fact, only abc matches example 4 abc unsigned matches the string containing abc-* + and? Used to indicate the number or order in which a character can appear. They say-{0,} = * example 1 ab {0,} matching starts with an and then B appears Omurn times ("a", "ab", "abb", "abbbbbbbbbbbbbbbbb") Infinite.) {1,} = + example 2 ab {1,} matching starts with an and then B appears 1 ab N times ("ab", "abb", "abbbbbbbbbbbbbbbbb", infinity) {0meme1} =? Example 3 ab {0 ab 1} matching begins with an and then B appears once ("a", "Omer") example 4 a {0jue 1} b matches a string ending with 0 or 1 a plus a b. ("b", "ab") Note (two ways of writing) ab {0,} can also be written as ab*ab {1,} can also be written as ab+ab {0jue 1}, as ab?a {0pm 1} baud $, or as'*'+', and'?' Just control the number of times the character in front of it appears. 2 {Nab N} several to several times {0} O times 3 {} this cannot be negative (2) the number of times can be modified example 5 ab {2} requires that a be followed by two b (not less than one) such as ("abb"); example 6 ab {2,} requires that a be followed by two or more b ("abb", "abbbb", etc.) Example 7 ab {3 abbbbb 5} requires that there can be 5 b ("abbb", "abbbb", or "abbbbb") after a. (3) follow multiple characters with () example 8 a (bc) * match a followed by 0 or a "bc" Of course, you can also write "a (bc) {0" Example 9 a (bc) {1 bc 5} matches one to five "bc."-│ is equivalent to OR to represent one or more or -example 1 A │ B matches a string containing "A" or "B" Example 2 (A │ B) C matches a string containing "AC" or "BC" Example 3 (A │ B) * C match contains (including 0-1) an or b, followed by a c -. It can represent all the single characters. Do not include "\ n" spaces if there are spaces, but add a character to the space [\ n.] Multiple spaces + 1 characters [\ n\ n.] Example 1 a. [0-9] An a plus a character plus a number from 0 to 9 example 2 ^. {3} $three arbitrary characters end- The parentheses in'[ab] 'match only a single character-example 1 [ab] matches a single an or b (same as "a │ b") Example 2 [an abcd] matches a single character from'a'to'd'(the same effect as "a │ b │ c │ d" and "[abcd]") We usually use [a-zA-Z] to specify a character as an uppercase and lowercase English example 3 ^ [a-zA-Z] matches a string that begins with uppercase and lowercase letters 4 [0-9]% matches a string with a shape such as x% [a-zA-Z0-9] $matches a string ending with a comma plus a number or letter 6% [^ a-zA-Z]% matches a string containing two percent signs with a (non) letter in it. You can also list the characters you don't want in square brackets. You just need to use'^ 'point 1: ^ [content] ^ in the closing brackets to start with []. It means that the content begins with point 2: [^ content] ^ begins in []. It means excluding the content (^ non) point 3: match the string containing these characters. In square brackets [*\ +? {}.] Or the symbol will fail parentheses match only a single character point 4: [] contains'] 'preferably as the first character in the list (probably followed by' ^') point 5: [] contains'-'it's best to put it first or last, or or the'-'in the middle of the second end of a range [a-d-0-9] will be valid. -\ b and\ B 1 match a word right boundary 2 match a non-word boundary- -you can match the ve in love but not the ve in very: you can match the ov in love but not the ov- in ovry. -\ d and\ D- -example 1\ d matches a numeric character. Equivalent to [0-9]. Example 2\ D matches a non-numeric character. Equivalent to [^ 0-9]. -\ w and\ W- Example 1\ w matches any word character including an underscore. Equivalent to'[A-Za-z0-9 _] 'example 2\ W matches any non-word character including an underscore. Equivalent to'[^ A-Za-z0-9]'. -match non-print characters- -- character meaning\ cx matches the control character indicated by x. For example,\ cM matches a Control-M or carriage return. The value of x must be one of Amurz or aMuz. Otherwise, c is treated as a literal'c 'character. \ f matches a feed character. Equivalent to\ x0c and\ cL. \ nmatches a newline character. Equivalent to\ x0a and\ cJ. \ r matches a carriage return. Equivalent to\ x0d and\ cM. \ s matches any white space characters, including spaces, tabs, page breaks, and so on. Equivalent to [\ f\ n\ r\ t\ v]. \ s matches any non-white space character. Equivalent to [^\ f\ n\ r\ t\ v]. \ t matches a tab. Equivalent to\ x09 and\ cI. \ v matches a vertical tab. Equivalent to\ x0b and\ cK. -example- -- regular expression that matches the leading and trailing white space characters: ^ s * | matches the regular expression of the Email address: W + ([- +.] w +) * @ w + ([-.] w +) * .w + ([-.] w +) * matches the regular expression of the URL URL: [a-zA-z] +: / / [^ s] * matches whether the account is legal (beginning with the letter) Allow 5-16 bytes, alphanumeric underscore): ^ [a-zA-Z] [a-zA-Z0-9] {4G15} $match domestic phone number: d {3}-d {8} | d {4}-d {7} matching forms such as 0511-4405222 or 021-87888822 920-209642-964 match Tencent QQ number: [1-9] [0-9] {4,} 1 + That is, 10000 matches China Postal Code: [1-9] d {5} (?! d) China Postal Code matches 6 digits ID card: d {15} | d {18} commentary: Chinese ID card matches ip address for 15 or 18 digits: dong.dan.d + comment: useful when extracting ip address-- -^ $/ / from the beginning to the end + / / 1 consecutive (connected) (that is,-{1 }) -? / indicates negative and non-negative (that is,-{0ret 1}) [0-9] * / / indicates the preceding digit 0murn (i.e. [09] {0) }). / / indicates a bit or no dot [^ / / the content inside [Amurz] / / matches all lowercase letters [Amurz] / / matches all uppercase letters [a-zA-Z] / / matches all letters [0-9] / / matches all digits 0-9 integers [0-9 -] / / matches all numbers Full stop and minus sign-^ [a-zA-Z0-9 _] + $/ / all contain more than one letter, Numeric or underlined string / / example concatenated aA0_A001a_ ^ [0-9] + $/ / all positive numbers (non-negative integers) / / example 3455006870080999009999 ^ -? [0-9] + $/ / all integers (including negative and integer) / / example-43443 or 43443 ^ -? [0-9] *. [0-9] * $/ all integers Decimal (including the infinite length of the number of decimal places before and after the decimal point) / / for example-100000.0000 or 10.00 if there is no decimal point, there must be no number after the decimal point. So add a..? To judge whether there is a decimal point, it is reasonable not to need. It's superfluous because this is used to judge decimals, if there is no decimal point. All characters except lowercase [^ / ^] / all characters except "/" and "^" characters [^ "] / / all characters except double quotation marks (") and single quotes (') are all the contents of the article "sample Analysis of regular expressions". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!
