How to conditionally replace text with replace-regexp
reddit / emacs

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sergio_101 · 2022-06-06 21:54

I am writing a script that looks at an org-mode buffer and replaces
strings with an org-mode hyperlink.

For instance, I want to replace every instance of "Link One" with
`[[LinkUrl][Link One]]`.

The problem is if I run my function again, that instance will now look
like `[[LinkUrl][[[LinkUrl][Link One]]]]`.

I need to replace the text only if it is not surrounded by brackets.

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MitchellMarquez42 · 2022-06-06 22:05

Include the spaces in both.

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artyhedgehog · 2022-06-06 22:22

I would try the following:

- `\bLink One\b`

- `\([^[]\)Link One\([^]]\)` -> `\1[[link-url][Link One]]\2`

There is probably a better way to specify "sequence before" and
"sequence after" without replacing them, but I'm not sure if that's
available in emacs regexp.

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FrozenOnPluto · 2022-06-07 00:33

If you’re not doing hundreds … query-replace can be handy in a pinch

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sergio_101 · 2022-06-07 01:53

There might be a TON of these, as the list will be growing every week.

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sergio_101 · 2022-06-07 01:54

okay, I think this is a good approach.. like, only match what SHOULD
be  there.. like "$%\^." or white space..

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7890yuiop · 2022-06-07 03:02

`\bLink One\b` is likely to match for `[Link One]`, but the second
approach certainly works.

Elisp regexps do not support arbitrary zero-width look-ahead/behind
assertions, but this is generally fine because elisp allows you
operate on specific groups of the matched text -- typically by calling
`replace-match` and specifying a SUBEXP argument (group number).

In general you do the broader matching in your main `(while (re-
search-forward...` loop and then you get to process each match however
you want to (which could involve further regexp matching/replacement
on that section of text).