How to use capture groups with the `\K` reset match?-CodePudding

I found

However, when adding a capture group (i.e., $1) using the regex (a\Kb), group $1 returns ab and not a:

Given the following string:

ab
cd

Using the regex (a\Kb)|(c\Kd) I would hope group $1 to contain b and group $2 to contain d, but that is not the case as it can be seen below:

I tried

However, now the matches are both part of group $0, whereas I require them to be part of group $1 and $2, respectively. Do you have any ideas on how this can be achieved? I am using

However, when applied to another example it fails. Therefore, for clarity, I am extending this question to cover the more complicated scenario discussed in the comments.

Suppose I have the following text in a markdown file:

- [x] Example task. | Task ends. [x] Another task.
- [x] ! Example task. | This ends. [x] ! Another task.

This is a sentence. [x] Task is here.
Other text. Another [x] ! Task is here.

|       | Task name     |    Plan     |   Actual    |      File      |
| :---- | :-------------| :---------: | :---------: | :------------: |
| [x]   | Task example. | 08:00-08:45 | 08:00-09:00 |  [[task-one]]  |
| [x] ! | Task example. | 08:00-08:45 | 08:00-09:00 |  [[task-one]]  |

I am interested in a single regex expression with two capture groups as follows:

group $1 (i.e., see selection below):
- outside the table: capture everything after [x] (i.e., not followed by !) until a |
- inside the table: capture everything after [x] (i.e., not followed by !) excluding the | symbols
group $2 (i.e., see selection below):
- outside the table: capture everything after [x] ! until a |
- inside the table: capture everything after [x] ! excluding the | symbols

I have the following regex (i.e.,

The regex for the matches inside the table is based on Wiktor Stribiżew's answer and explained here.

CodePudding user response：

If I understand what you are trying to match, use as a regex:

(?:[^|\s]\s*\[x\](?!\s*!)\s*\K([^!|\n]*))|(?:[^|\s]\s*\[x\]\s*!\s*\K([^|\n]*))

See Regex Demo

I removed some unnecessary escaping. But moreover:

For Group 1 matches (first alternative) before the |, note that I have after we have matched '[x]` the following negative lookahead assertion:

(?!\s*!)

This ensures that the [x] is not followed by 0 or more spaces followed by an exclamation mark. Only then do you want to match everything up to the next exclamation mark or newline as Group 1.

CodePudding user response：

Instead of \K, try to use control verbs (*SKIP)(*F):

(a(*SKIP)(*F)|b)|(c(*SKIP)(*F)|d)

Check the test case.