正则表达式——以字母开头和结尾，只接受字母、数字和_

问题描述

我正在尝试编写一个正则表达式，指定文本应以字母开头，每个字符应为字母、数字或下划线，一行中不应有 2 个下划线，并且应以字母或数字.目前，我唯一拥有的是 ^[a-zA-Z]\w[a-zA-Z1-9_] 但这似乎不能正常工作，因为它只匹配3 个字符，并允许重复下划线.我也不知道如何指定最后一个字符的要求.

I'm trying to write a regular expression which specifies that text should start with a letter, every character should be a letter, number or underscore, there should not be 2 underscores in a row and it should end with a letter or number. At the moment, the only thing I have is ^[a-zA-Z]\w[a-zA-Z1-9_] but this doesn't seem to work properly since it only ever matches 3 characters, and allows repeated underscores. I also don't know how to specify requirements for the last character.

推荐答案

^[A-Za-z][A-Za-z0-9]*(?:_[A-Za-z0-9]+)*$

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