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/ **
* regular expression: also called regular expressions, an expression, this effect according to certain rules composed mainly of expression matching string
*
* regular expressions role: to match the string
* can be used in most programming languages
*
* regular expression: the oil or meta-character qualifier is a formula consisting of
*
* metacharacters:
* (1) except \. n is any character other than '1'
* (2) [] 1, range, any number between [0-9] 0-9 | [az] between any of a lowercase letter az | [AZ] AZ any of a capital letter between | between any of [a-zA-Z] az AZ a letter | [0-9a-zA-Z] any of a number or letter
* 2, the significance of the regular expression characters Ghost get rid of representation is a [.].
* (3) | or [0-9] | [az] is either a number or a lowercase letter
* (4) () a packet priority as lifting, [0-9] | ([az ]) | [AZ] Priority calculation inside the parentheses, such as lower case letters, ([0-9]) ([ az]) ( [AZ]) three groups counted from the leftmost such as (() (())) four groups (() ((
*
* the following both of these meta-characters can also be called qualifiers:
* (5) * indicates that: the preceding expression appears 0 times to several [az] [0-9] * will be a lowercase letter and any number will appear 0 times to
* 'svnazsjb230203023' [az] [0-9] * to true
* (6) when the front + means expressing one or more times
* [az] [9] + behind a minimum of one lowercase letter 9, or a plurality of 9 "jafmv9vadv"
* (. 7)? it is represented by the foregoing expression It appeared 0 times to 1 times, minimum 0, maximum of 1, another meaning: to stop greedy [4] [az] "142324ij"?
*
* qualifier: limit the number of times the preceding expression appears
*
* (8 )} {the number of times may be more clearly appears in front of the expression
* (1 {0,1} indicates that the expression appeared to multiple times 0 (*)
* (2, {1} represents the foregoing expression appears 1 to a multiple (+)
* (3, {0,1} indicates that expression appears 0 times to 1 times (?)
* (4, {3,4} denotes the previous table Expression appeared three times to four times
* (5, {4} indicates that the expression appears four times
* (6, {30} error
* (9) is represented by what began ^ (^ [0-9] with a digit; ^ [ az] with a lowercase letter), or is negated (inverted) ([^ 0-9] non-numeric; [^ 0-9a-zA-Z )] takes a special symbol (not the special symbol underscore _)
* (10 ) $ express what end [0-9] [az] $ must end with a lowercase letter (1a); ^ [0-9] [az] $ strict mode is equivalent to write "1234re" falus // "4f" to true
\ any * (11) d numbers in a
* (12) \ any D non-numeric one (letters + special symbols)
* (13) \ any s whitespace one
* (14) \ s whitespace any one of a
* (15) \ w non-special characters (_) is equivalent to [0-9a-zA-Z_]
* (16) \ W is equivalent to special symbols ^ [0-9a-zA-Z_]
* (17) \ b word boundary
* (18) \ f feed character
* (19) \ n newline
*
*
*
*
*
*
* /
/ * string element #### used
| metacharacters | instructions |
| ---- | --------------- |
| \ d | matching digits |
| \ D | matches any non-numeric characters |
| \ w | match letters or numbers or an underscore |
| \ W is | not match any of letters, numbers, underscores |
| \ S | match any whitespace |
| \ S | not match any whitespace characters |
|. | match any single character except newline |
| ^ | which matches the first line of text (to who started) |
| $ | representing the text matched end of the line (to who end) |
#### yuan commonly used strings
| metacharacters | Description |
| ---- | - ----------------------------- |
| \ d | matching digits |
| \ d | matches any non-numeric characters |
| \ W | matching letters or numbers or underscores |
| \ W is | match any instead of letters, numbers, underscores |
| \ S | match any whitespace |
| \ S | match any not whitespace characters |
|. | Match any single character except newline |
| ^ | which matches the first line of text (to who started) |
| $ | representing the text matched end of the line (to who end) |
#### qualifier
| qualifier | Description |
| ----- | ----------------- |
| * | repeated zero or more times |
| + | repeated one or more times |
|? | repeat ZeroOrOne |
|} n {| n times |
| {n,} | repeated n times or more |
| {n, m} | repeated n times to m |
#### other
[] characters string enclosed in square brackets, any of which represents a character matching, or equivalent means
[^] Matches the contents within the brackets in addition to
\ escape
| a or both, selection. Note that | divided into two parts left and right sides, regardless of how long the left and right sides of the multi disorder
() directly to the amount of two selected from a grouping
eg: gr (a | e) y and matching gray Gray
[\ u4e00- \ u9fa5 ] Chinese characters matching
* /
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