regex search replace \1 not working

David Klippel

I am trying to search for a string followed by any number then replace the found string and number with two line feeds in front of it. The search works but the replace drops the found string. I have tried \0, \1, \2. This with NP++ 8.1.6. What am y

Regular Expression
Search: 3.[0-9]
Replace: \n\n\1

Neil Schipper

@David-Klippel said in regex search replace \1 not working:

3.[0-9]

You are omitting the encoding of the capture operation.

Try (3.[0-9])

David Klippel

@Neil-Schipper I knew I was missing something simple but was finding any clear examples. Thank you.

PeterJones

@David-Klippel

It’s hard to tell, because you did not follow the Formatting Forum Posts link from the Please Read Before Posting. You also didn’t give any examples of before and after data, so that makes it hard to know if we’re correctly interpreting your question. The best-asked question follows the formatting advice, and gives both before and after data.

Please note the expression as we can see it, 3.[0-9] searches for a literal 3, then any character (as indicated by regex .) and then any digit from 0-9. So it will match 3.0 but also 3p2 or 3 3 – I am not sure if that’s really what you’re trying to match.

In your replacement, the \n will replace with just the LF character. If you are editing a file with Unix/Linux-style end-of-lines (EOL), that is correct; if you are editing a file with Windows EOL, then it’s only the LF half of the CRLF pair. In a windows file, a single EOF is indicated by \r\n in the replacement; so to get two newlines, you will want \r\n\r\n.

The replacement \1 will insert the contents of the first match-group. Since you do not have any parentheses in your FIND expression, there are no matched groups, so nothing to replace. And, as documented in the regex substitutions section of the online user manual, \0 is not the right way to indicate the contents of the whole match; the correct syntax for that is $0 (or $& or $MATCH or …).

With all of that, \r\n\r\n$0 is likely what you were intending for the replacement.

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Neil Schipper

@PeterJones said in regex search replace \1 not working:

the \n will replace with just the LF character

I wasn’t aware of that, and it’s good to know. I guess I assumed replace behaved like in some HLLs (printf in ‘C’, IIRC) which automagically terminate lines according to the conventions of the O/S.