正则表达式，仅当某个字符出现在特定数量的字符之后时才删除该特定字符之后的所有内容

Question

I'm looking for a simple regular expression for this,

Example 1:

n = 5

Input: abcde@varun@gmail.com

Output: abcde@varun

Example 2:

n = 5

Input: abcd@varun@gmail.com

Output: abcd@varun@gmail.com 

This means that if n = 5 and if the symbol @ is NOT occuring on or before the 5th index(Assuming the string starts at index 1) then remove all everything(including the @ symbol) after the second occurance of @ .

Leave the string as it is if the above rule is not satisfied.

Thanks Varun.

Answer 1

You can use this regex to capture the part that you wish to keep into the first group:

(^[^@]{5,}@[^@]*)@

The expression matches a string that has at least two @ signs, with the first @ not occurring within the initial five characters.

This would capture abcde@varun , but not abcd@varun , because @ occurs within the initial five characters.

Demo.

Replace 5 with n to change the length of the prefix as needed.

Answer 2

^(?!(?:@|.@|.{2}@|.{3}@|.{4}@))(.*?@.*?)@.*$

Try this.Replace by $1 .See demo.

https://regex101.com/r/uC8uO6/7