用于允许字母数字、特殊字符且不以 @ 或 _ 或结尾的正则表达式

Question

I am new to regex , I created below regex which allows alpha numeric and 3 special characters @._ but string should not end with @ or . or *

^[a-zA-Z0-9._@]*[^_][^.][^@]$

it validates abc@ but fails for abc.

Answer 1

Your pattern allows at least 3 characters, where the last 3 are negated character classes matching any char other than the listed.

The pattern ^[a-zA-Z0-9._@]*[^_][^.][^@]$ will match 3 newlines , and adding all the chars to a single character class ^[a-zA-Z0-9._@]*[^@._]$ will also match a single newline only.

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If you want to allow all 3 "special" characters and match at least 3 characters in total you can repeat the character class 2 or more times using {2,} and match a single char at the end without the special characters.

^[a-zA-Z0-9._@]{2,}[a-zA-Z0-9]$

Regex demo

Matching as least a single char (and not end with . _ @ )

^[a-zA-Z0-9._@]*[a-zA-Z0-9]$

Regex demo

Answer 2

Leading ^ is the start of the paragraph
Trailing $ is the end of the paragraph
. is the everything {2,} means the more than 2 letters
[^@_] means one letter Not @ or _

^.{2,}[^@_]$

click here the answer

Answer 3

if you include all the characters in the one character set, that'll work.

^[a-zA-Z0-9._@]*[^@._]$

Screenshot shows how different text examples would work (try it out on http://regexr.com )