题目

正则表达式,要匹配任意数字为什么要 [[:digit:]] 两个括号才行,一个括号就不对
[:digit:]就不对

提问时间：2021-04-01

答案

具体官网的解释是：These are always used inside square brackets in the form [[:alnum:]] or combined as [[:digit:]a-d]即：对于[:digit:] Only the digits 0 to 9 [:alnum:] Any alphanumeric character 0 to 9...