Matching end of line position using m flag with different line ending styles

Question

I\'m trying to wrap each line that starts with \"## \" with tags. Trying to achieve a GitHub/Stackoverflow-like syntax for text formatting.

This is what I got:

Answer 1

It seems that in your current PCRE settings, a dot matches all chars other than LF (\n, line feed), and thus, it matches CR (\r, carriage return), and that is also a line break char.

PCRE supports overriding of the default newline (and therefore the behavior of the $ anchor). To make the . match all characters but CR and LF, turn on the corresponding flag:

'/(*ANYCRLF)^## (.*)$/m'
  ^^^^^^^^^^

$ will assert the end of line before \r\n.

See more about this and other verbs at rexegg.com:

By default, when PCRE is compiled, you tell it what to consider to be a line break when encountering a . (as the dot it doesn't match line breaks unless in dotall mode), as well the ^ and $ anchors' behavior in multiline mode. You can override this default with the following modifiers:

✽ (*CR) Only a carriage return is considered to be a line break
✽ (*LF) Only a line feed is considered to be a line break (as on Unix)
✽ (*CRLF) Only a carriage return followed by a line feed is considered to be a line break (as on Windows)
✽ (*ANYCRLF) Any of the above three is considered to be a line break
✽ (*ANY) Any Unicode newline sequence is considered to be a line break

For instance, (*CR)\w+.\w+ matches Line1\nLine2 because the dot is able to match the \n, which is not considered to be a line break. See demo.