If it is the first character listed in the class, it can’t possibly indicate a range, so it is not considered a metacharacter. Along the same lines, the question mark and period at the end of the class are usually regular-expression metacharacters, but only when not within a class (...
Any printable character that is not white space or alphanumeric. [:cntrl:] Any nonprintable character. For example, regular expression[[:lower:]]matches any lower case alphabetic character. Character ranges are specified by a dash (–) between two characters or collation sequences. This indicates...
In this step, you translate the general formats derived in Step 1 into segments of a regular expression. You then add these segments together to form the entire expression. The table below shows the generalized format descriptions of each character pattern in the left-most column. (This was ca...
[[:upper:]] 任何大写字母。 [[:lower:]] 任何小写字母。 [[:punct:]] 任何标点符号。 [[:xdigit:]] 任何16进制的数字,相当于[0-9a-fA-F]。 各种操作符的运算优先级 / 转义符 (), (?, (?=), [] 圆括号和方括号 *, +, ?, {n}, {n,}, {n,m} 限定符 ^, $, /anymetacharacter ...
[[:space:]] 任何白字符。 [[:upper:]] 任何大写字母。 [[:lower:]] 任何小写字母。 [[:punct:]] 任何标点符号。 [[:xdigit:]] 任何16进制的数字,相当于[0-9a-fA-F]。 各种操作符的运算优先级 \ 转义符 (), (?, (?=), [] 圆括号和方括号 ...
For example, the terminology rule regular expression, "/a.b/", matches all text where there is an "a" followed by any single character, followed by a "b", as in, "a5b". * The asterisk matches the preceding pattern or character zero or more times. For example, "/fo*/" matches ...
正则表达式(regular expression)描述了一种字符串匹配的模式,可以用来检查一个串是否含有某种子串、将匹配的子串做替换或者从某个串中取出符合某个条件的子串等。 列目录时, dir *.txt或ls *.txt中的*.txt就不是一个正则表达式,因为这里*与正则式的*的含义是不同的。
By default, white space in a regular expression pattern is significant; it forces the regular expression engine to match a white-space character in the input string. Because of this, the regular expression "\b\w+\s" and "\b\w+ " are roughly equivalent regular expressions. In addition, ...
Any non–white space character. [^ \f\n\r\t\v] \t Tab character. \x09 and \cI \v Vertical tab character. \x0b and \cK Order of Precedence A regular expression is evaluated much like an arithmetic expression; that is, it is evaluated from left to right and follows an order of ...
Regex 正则表达式(Regular expression): outline: 1.常用re flag参数 2.常用re function 3.当匹配成功时返回一个对象 4. Quantifier 5.Character Classes 6.Negative Character Class 7. Word Boundary Anchor 8. Beginning Anchor & End Anchor 9. Capture Groups ...