Regular expression substitution isn't working.

[jharris1993]

Operating System and Version

Mint 22.3 Mate

Distribution

Appimage

Description

If I select a find-and-replace using regular expressions and define a string pattern:
Find = (\d\d.\d\d.\d\d\d\d)(\n)
Replace = $2

The "find" finds the appropriate representative string, however the replace simply substitutes "$2" instead of the content of the second part of the original expression "\n" - a new line.

Steps to Reproduce

1. Load a document.
2. Create a regular expression and verify it finds what you want.
3. Use regular expression substitution ($1, $2, etc.), to generate a replacement string
4. Attempt the replacement.

Debug Information

Notepad Next v0.13 (AppImage)
Build Date/Time: Jan 25 2026 20:13:34
Qt: 6.5.3
OS: Linux Mint 22.3
Locale: en_US
CPU: x86_64
File Path: /tmp/.mount_NotepaJfJbKJ/usr/bin/NotepadNext
Arguments: /home/jim/Downloads/NotepadNext-v0.13-x86_64.AppImage /home/jim/Desktop/2025 Tax Year/Bank Downloads/Sberbank James/James_Sberbank_ru.txt
Config File: /home/jim/.config/NotepadNext/NotepadNext.ini

Additional Details

The expected result, (and what happens in Notepad++), is that the second part of the expression, a newline character "(\n)", is substituted for the found string. The result should be that the redundant date line is replaced with a blank line.

[dail8859]

The regular expression engine is definitely lacking and buggy. Qt has its own implementation of a regular expression engine which is the current implementation but is not as powerful and flexible as it needs to be to match that of Notepad++. I would love to be able to reuse the N++ regular expression engine at some point.

[jharris1993]

Surely there are open source regex engines that actually know how to do substitution correctly?

[dail8859]

There are definitely libraries. The difficulty is:

• Making sure is cross platform (usually not a problem)
• Handling encodings correctly (from both the editor and the interface)
• Integrating with the Scintilla library
• Handling any other Qt specifics

[drfiemost]

You should use \2 and not $2
IIRC is the same on Notepad++

[jharris1993]

Nope.
It's $n for positional substitution.

I've been using Notepad++ on Win-10 for the last few days and have been using regex positional substitution almost continuously.

[drfiemost]

Oh right, N++ supports both \n and $n
What about the c++11 regex?

Besides being returned in the std::match_results, the captured submatches are accessible as backreferences (\1, \2, ...) and can be referenced in regular expressions. Note that std::regex_replace uses $ instead of \ for backreferences ($1, $2, ...) in the same manner as String.prototype.replace (ECMA-262, part 15.5.4.11).

https://en.cppreference.com/w/cpp/regex/ecmascript.html

[DidierLoiseau]

It also seems like escaped characters do not work in the replacement strings, e.g. \n, \r, \t etc.

It works in extended mode though.