Learning to Love RegEx: a Find and Replace example

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Someone in my blog publishing pipeline – Github, Jekyll, etc. – Changed how headings are formatted. Instead of #Heading, I had to specify # Heading. This makes sense, I just had converted this blog from elsewhere and it wasn’t high on my priorities at first. But all of a sudden things broke, so I had to change a lot of headings quickly.


I needed to find any instances of ##[Any Character] and add a space in-between, across all of my blog files.

This kind of thing always sets off a light bulb in my brain for regular expressions. I’ll be honest, I’m not a RegEx wiz in any sense of the word, but with some Googling I was able to figure it out.

Creating the RegEx

The requirements are to find two pound signs ## Followed by any letter (uppercase or lowercase).

The RegEx for this is ##[A-Za-z].

Adding the Capture Group

In order for Notepad++ to be able to replace the RegEx (rather than just find it), we have to create a capture group to capture that first letter (so that A becomes A[space], with a space)

To do this, we wrap the first character portion in parentheses, giving us ##([A-Za-z]). This will create a capture group note that Notepad++ can refer to using \1.

Replacing the text

  • In Notepad++, we open the Find & Replace window.
  • We Search for ##([A-Za-z])
  • We replace it with ## \1 (the original heading, plus a space, plus the first character)
  • We make sure that the search mode is RegEx
  • We perform the find and replace across all files.

This took care of a huge amount of changes for me and probably saved an hour or two of my life. Really makes one appreciate the value of RegEx.

Hope this is helpful!


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