How do I delete the line above and below the matching line using regex?

Question

I have a document where the matching line is []

For above:

Whenever the matching line is found, the line above that should be deleted. In this case ## mentions should be deleted.

## mentions
[]

For below:

Whenever the matching line is found, the line below that should be deleted. In this case ## mentions should be deleted.

[]
## mentions

How to achieve this using regex?

Edit: I am using VSCode regex.

What if there is a line above and below? Or are you asking two questions? — trincot, Feb 17 '21 at 19:57
Above = just the single line above the matching line. If there are multiple lines above the matching line, only select the first line above the matching one. — dsf, Feb 17 '21 at 20:13

Yassin Hajaj · Accepted Answer · 2021-02-17T20:20:58.590

1

Replace .*\n(?=\[\]) by nothing for above. See this demo

Replace (?<=(\[\]))\n.* by nothing for below. See this demo

Explanation for above

.*       Match all characters appearing 0 to N times
\n       Match a newline character
(?=\[\]) Make sure that [] is found just after the newline character

Explanation for below

(?<=(\[\])) Make sure our target is on the line before
\n          Match a newline character
.*          Match all characters appearing 0 to N times

Matching `[]` as group

To match [] as a group, simply enclose it with paranthesis like hereunder

.*\n(?=(\[\]))

edited Feb 17 '21 at 20:20

answered Feb 17 '21 at 19:55

Yassin Hajaj

21,337
9
51
89

This works! Can you also please make an edit to include the regex for selecting line "below" the matching line? I am accepting it as soon as SO allows. – dsf Feb 17 '21 at 19:58
@JiayounoKim you mean to match it as group? – Yassin Hajaj Feb 17 '21 at 19:59
For example, if the text is: [] ## mentions then ## mentions should be selected as its the line below. And yes, if it's not much trouble please show group as well. That would be all. Thank you! – dsf Feb 17 '21 at 20:02
OK I understand it – Yassin Hajaj Feb 17 '21 at 20:02
@JiayounoKim should be OK now? – Yassin Hajaj Feb 17 '21 at 20:06
1

This "below" regex you did works on regex101 website but on VSCode, it shows error: Lone qualifier bracket!? – dsf Feb 17 '21 at 20:12
I'll test @JiayounoKim and I'll let you know – Yassin Hajaj Feb 17 '21 at 20:19
@JiayounoKim Ok I corrected it for VSCode, they don't like when you don't escape brackets – Yassin Hajaj Feb 17 '21 at 20:21
Thank you so much. It works. – dsf Feb 17 '21 at 20:43

How do I delete the line above and below the matching line using regex?

1 Answers1

Explanation for above

Explanation for below

Matching [] as group

Matching `[]` as group