正则表达式查找不以点开头和结尾，只允许一些特殊字符而不是全部 [英] Regex to find not start and end with dot and allow some special character only not all

问题描述

我正在尝试匹配一个不是以 (.)dot 开头的字符串，并允许在字符串中使用一些特殊字符，例如下划线 (_)我发现点匹配正则表达式但无法匹配我所做的特殊字符

I am trying to match a string which is not start and and with (.)dot and allow some special char like underscore(_) in string i found dot match regex but not able to match special character what i have done

preg_match('/^(?![.])(?!.*[.]$).*$/', $str)

不允许

.example
example.
example?ghh. (or some more special char not allowed in string)

允许

 exam.pl56e
    exmple_
    _example_
    exam_ple

所以字符串将是

1. Not start with dot but in the middle can be a dot(.)
2. String Not allow special char (&%$#@) etc. But allow alpha numeric, underscore
3. Not end with dot(.)

它正确匹配开始和结束点，但我需要改进它以不允许所有特殊字符，如 (!&%) 等.只允许给定的特殊字符.谢谢

It's matching start and end dot correctly but i need to improve it to not allow all special character like (!&%) etc. Just allow given special character. Thanks

推荐答案

您可以使用

'~^(?!\.)[\w.]*$(?<!\.)~'

查看正则表达式演示

详情:

• ^ - 字符串的开始
• (?!\.) - . 不能是第一个字符
• [\w.]* - 0 个或多个字母、数字、_ 或 . 字符(替换 *code> 与 + 匹配字符串中至少 1 个字符以禁止空字符串匹配)
• $ - 字符串结束
• (?<!\.) - 最后一个字符不能是 .

• ^ - start of string
• (?!\.) - a . cannot be the first char
• [\w.]* - 0 or more letters, digits, _ or . chars (replace * with + to match at least 1 char in the string to disallow an empty string match)
• $ - end of string
• (?<!\.) - last char cannot be .

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