Extract specific string using RegExp

Question

I have a string something like this,

Example 1 @abc@xy<a href="http://-example.com">-example.com</a> and @xyz@abc.com Example 2

Now, I want to remove the string occurring after the second @ encountered, i.e. @example.com @abc.com and preserve the rest of the data which should look like,

Example 1 @abc and @xyz Example 2

I have tried a lot of RegExp and saw many examples but have had no luck so far.

If anyone has tried something similar, it'd be great if you can help me out.

_the string occurring after the second @_ - do you have a clear definition of what belongs to that string and what not? In your example it seems to be `@xy-example.com` - why not `@xy` or `@xy-example.com and` — Sebastian Proske, Aug 10 '18 at 08:11
Hey, `@xy-example.com` This whole part needs to be replaced. `and` is to be preserved. — Shreya Shah, Aug 10 '18 at 08:17
@ShreyaShah I figgured as much, but it isn't clear to me, why you want exactly that part. What rules do you have to determine, that `@xy-example.com` is what you want - is it _any non space characters and the complete tag that follows if there is one_? Defining this for us should also help yourself build the regex, as clear cut borders is what one needs to build a well working regex. — Sebastian Proske, Aug 10 '18 at 08:37
@SebastianProske `and` is just another string, it could be anything. Alright we can just focus on `@xyz@abc.com Example 2` and remove the part followed by the second `@` and preserve Example 2. — Shreya Shah, Aug 10 '18 at 09:11
@ShreyaShah that would be `(@[^\s@]*)@[^\s@]*` and replace with `$1`. What's the language you use to implement this? — Sebastian Proske, Aug 10 '18 at 09:14
hey @SebastianProske thanks a ton, man! Works like a charm. :D — Shreya Shah, Aug 10 '18 at 09:20

score 1 · Accepted Answer · answered Aug 10 '18 at 09:28

For the second half of your sample you can simply match both @s and replace only the second on, by grouping and using them in the replace.

Pattern: /(@[^\s@]*)@[^\s@]*/g Replacement: '$1'

This matches an @ followed by anything but spaces and @ and stores it in group 1. It then matches the next @ and again anythihng but spaces and @.

If there might be other stuff between both @s, you could adjust your pattern to use (@[^@]*) for the capturing group.

Four the first part of your sample, you would have to find a better pattern to match what follows the second @, this could be something along @[^\s@<]*(?:<[^<>]*>[^<>]*<\/[^<>]*>) but I'm not quite sure about your requirements and matching along tags is always tricky.

Michał Turczyn · Answer 2 · 2018-08-10T08:39:18.440

0

Try this pattern: ^[^@]*@[^@]+(?=@). It will match everything before second @. It anchors at the beginning of a string, first it matches everything except @: [^@], then matches @, then again matches everything except @: [^@], until next @ is met: (?=@) (positive lookahead).

Demo

edited Aug 10 '18 at 08:39

answered Aug 10 '18 at 08:07

Michał Turczyn

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hey thanks, but it only works if my string starts with an `@` which is not the case. – Shreya Shah Aug 10 '18 at 08:09

score 0 · Answer 3 · answered Aug 10 '18 at 08:08

0

Capture the first @ followed by non-@ characters in a group, then match @ again followed by non-space characters, and replace with the first captured group:

(@[^@]+?)@[^ ]+?(?= )

Result:

Example 1 @abc and @xyz Example 2

https://regex101.com/r/mXRlsZ/1

Note that this will also replace any @s in a row, past the first - eg @abc@xy@foo will become @abc

answered Aug 10 '18 at 08:08

CertainPerformance

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You don't need all those non-greedy quantifiers and the positive lookahead: `(@[^@]+)@\S+` – revo Aug 10 '18 at 09:38

score 0 · Answer 4 · answered Aug 10 '18 at 08:54

string input = @"Example 1 @abc@xy<a href=""http://-example.com"">-example.com</a> and @xyz@abc.com Example 2";
string pattern = @"@.+?(?=@|$)";
int x = 0;
string s = Regex.Replace(
    input,
    pattern,
    m => ++x == 2 ? Regex.Match(m.Value, @">(\s+.+?\s+)$").Groups[1].Value : m.Value);

Explanation

First, start with searching for @ symbol. Variable x is tracking the number of occurrences of @. As soon as it hits 2, then we extract everything between the end and >. If x doesn't equal to 2, then we just return the match (m.Value);

Extract specific string using RegExp

4 Answers4

Explanation