Match linebreaks - n or r n

Question

While writing this answer  I had to match exclusively on linebreaks instead of using the s-flag  dotall - dot matches linebreaks      The sites usually used to test regular expressions behave differently when trying to match on  n or  r n   I noticed   Regex101 matches linebreaks only on  n  example - delete  r and it matches    RegExr matches linebreaks neither on  n nor on  r n and I can t find something to make it match a linebreak  except for the m-flag and  s  example  Debuggex behaves even more different  in this example it matches only on  r n  while here it only matches on  n  with the same flags and engine specified   I m fully aware of the m-flag  multiline - makes   match the start and   the end of a line   but sometimes this is not an option  Same with  s  as it matches tabs and spaces  too       My thought to use the unicode newline character   u0085  wasn t successful  so    Is there a failsafe way to integrate the match on a linebreak  preferably regardless of the language used  into a regular expression  Why do the above mentioned sites behave differently  especially Debuggex  matching once only on  n and once only on  r n

User · Answer

You have different line endings in the example texts in Debuggex. What is especially interesting is that Debuggex seems to have identified which line ending style you used first, and it converts all additional line endings entered to that style.

I used Notepad++ to paste sample text in Unix and Windows format into Debuggex, and whichever I pasted first is what that session of Debuggex stuck with.

So, you should wash your text through your text editor before pasting it into Debuggex. Ensure that you're pasting the style you want. Debuggex defaults to Unix style (\n).

Also, NEL (\u0085) is something different entirely: https://en.wikipedia.org/wiki/Newline#Unicode

(\r?\n) will cover Unix and Windows. You'll need something more complex, like (\r\n|\r|\n), if you want to match old Mac too.

User · Answer

This only applies to question 1   I have an app that runs on Windows and uses a multi-line MFC editor box  The editor box expects CRLF linebreaks  but I need to parse the text enterred with some really big nasty regexs      I didn t want to be stressing about this while writing the regex  so I ended up normalizing back and forth between the parser and editor so that the regexs  just use  n  I also trap paste operations and convert them for the boxes     This does not take much time  This is what I use    boost  regex  CRLFCRtoLF            r  n     r     n           MODx     boost  regex  CRLFCRtoCRLF            r  n       n          MODx         Convert  All style  linebreaks to linefeeds      ---------------------------------------  void ReplaceCRLFCRtoLF  string amp  strSrc  string amp  strDest          strDest    boost  regex replace   strSrc  CRLFCRtoLF     n             Convert linefeeds to linebreaks  Windows       ---------------------------------------  void ReplaceCRLFCRtoCRLF  string amp  strSrc  string amp  strDest          strDest    boost  regex replace   strSrc  CRLFCRtoCRLF     r  n

User · Answer

Gonna answer in opposite direction   2  For a full explanation about  r and  n I have to refer to this question  which is far more complete than I will post here  Difference between  n and  r   Long story short  Linux uses  n for a new-line  Windows  r n and old Macs  r  So there are multiple ways to write a newline  Your second tool  RegExr  does for example match on the single  r   1    r n   as Ilya suggested will work  but will also match multiple consecutive new-lines    r n  r  n  is more correct

User · Answer

In PCRE  R matches  n   r and  r n

User · Answer

In Python     as Peter van der Wal s answer re split r  r n  r  n   text  flags re M     or more rigorous     https   docs python org 3 library stdtypes html str splitlines str splitlines

[regex] Match linebreaks - \n or \r\n?

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