不允许连续点的正则表达式 [英] Regex that does not allow consecutive dots

问题描述

我有一个正则表达式允许字母数字、下划线和点，但不允许连续的点:

I have a Regex to allow alphanumeric, underscore and dots but not consecutive dots:

^(?!.*?[.]{2})[a-zA-Z0-9_.]+$

我现在还需要允许在字符串的第一个和最后一个字符中使用点.

I also need to now allow dots in the first and last character of the string.

我该怎么做?

推荐答案

您可以像这样使用它并附加前瞻:

You can use it like this with additional lookaheads:

^(?!\.)(?!.*\.$)(?!.*?\.\.)[a-zA-Z0-9_.]+$

• (?!\.) - 开始时不允许 .
• (?!.*?\.\.) - 不允许有 2 个连续的点
• (?!.*\.$) - 不允许 . 在末尾
  • (?!\.) - don't allow . at start
  • (?!.*?\.\.) - don't allow 2 consecutive dots
  • (?!.*\.$) - don't allow . at end

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