Regex-如何防止重复的特殊字符？

Question

I don't have an experience on Regular Expressions. I need to a regular expression which doesn't allow to repeat of special characters (+-*/& etc.) The string can contain digits, alphanumerics, and special characters.

This should be valid: abc,df

This should be invalid: abc-,df

i will be really appreciated if you can help me. Thanks for advance.

Answer 1

[\\,\\+\\-\\*\\/\\&]{2,} Add more characters in the square bracket if you want.
Demo https://regex101.com/r/CBrldL/2

Answer 2

Two solutions presented so far match a string that is not allowed.

But the tilte is How to prevent... , so I assume that the regex should match the allowed string. It means that the regex should:

• match the whole string if it does not contain 2 consecutive special characters,
• not match otherwise.

You can achieve this putting together the following parts:

• ^ - start of string anchor,
• (?!.*[...]{2}) - a negative lookahead for 2 consecutive special characters (marked here as ... ), in any place,
• a regex matching the whole (non-empty) string,
• $ - end of string anchor.

So the whole regex should be:

^(?!.*[!@#$%^&*()\-_+={}[\]|\\;:'",<.>\/?]{2}).+$

Note that within a char class (between [ and ] ) a backslash escaping the following char should be placed before - (if in the middle of the sequence), closing square bracket, a backslash itself and / (regex terminator).

Or if you want to apply the regex to individual words (not the whole string), then the regex should be:

\b(?!\S*[!@#$%^&*()\-_+={}[\]|\\;:'",<.>\/?]{2})\S+

Answer 3

使用以下正则表达式匹配无效的字符串。

[^A-Za-z0-9]{2,}

Answer 4

[^\w,\s]{2,} This would be a shortest version to match any two consecutive special characters (ignoring space)

If you want to consider space, please use [^\w]{2,}