regex - search and replace - "remember"?

[Adam Yik]

I don’t know where in the document mentions where you can take what ever it has been found, and copies text and is pasted in the “replace with”. For example:

abcd/1234/efgh
ijkl/5678/mnop

becomes:

abcd/efgh/1234
ijkl/mnop/5678

(it’s swapped, by being replaced with [abcd/<memory 2>/<memory 1>]).

[Alan Kilborn]

@Adam-Yik

Open the Replace dialog by pressing Ctrl+h and then set up the following search parameters:

Find what box: (?-s)(.{4})/(.{4})$
Replace with box: \2/\1
Search mode radiobutton: Regular expression
Wrap around checkbox: ticked
. matches newline checkbox: doesn’t matter (because the (?-s) leading off the Find what box contains an s variant)

Then press the Replace All button

[Ekopalypse]

Hmm … question is quite similar to this one, strange.

[Adam Yik]

@Alan-Kilborn So, it’s something to do with a backreference. Is this caused by the parenthesis? Because the . means to match any character and {ℕ} is the number of characters. Also, do backreferences’s numbering:

-Starts at 0?
-Is numbered from left to right (example, the first parenthesis group is numbered 0 and the last is numbered 2)?

[Alan Kilborn]

@Adam-Yik said in regex - search and replace - "remember"?:

Is this caused by the parenthesis?

Yes.

do backreferences’s numbering: Starts at 0?

No, they start at 1, and they aren’t called backreferences, they’re called “capture groups”.

A pseudo-group #0 is for the overall match and is accessed at replace time as $0 rather than \0.

Is numbered from left to right

Yes.

he first parenthesis group is numbered 0 and the last is numbered 2)?

No, but close. The first is numbered 1 and the second/last is 2.

[Adam Yik]

@Alan-Kilborn thanks! sadly, up to 9 can be remembered within parent group at a time. But I think you can get around this by doing this multiple times.

[Adam Yik]

@Alan-Kilborn To fully understand the subgroup, it is very similar to Directory-based system such as windows 10. However, up to 9 files and folders can exist in a directory, and to refer them on a path, you place each digit and without the path separator /

[PeterJones]

@Adam-Yik said in regex - search and replace - "remember"?:

thanks! sadly, up to 9 can be remembered within parent group at a time

Actually, there is no such limitation. The substitutions section of the official docs says,

$ℕ, ${ℕ}, \ℕ ⇒ Returns what matched the ℕth subexpression, where ℕ is a positive integer (1 or larger).

By using the ${ℕ} notation, you can reference any capture group, not just the first 9. So the fifteenth group would be ${15} in the replacement expression.

[Alan Kilborn]

@Adam-Yik said in regex - search and replace - "remember"?:

it is very similar to Directory-based system such as windows 10. However, up to 9 files and folders can exist in a directory, and

There is no such limitation in Windows, and it doesn’t have anything to do with regular expression processing. Please don’t spread misinformation.