Search for string ignoring new lines

Question

I am used to writing files where paragraphs are split into several lines, e.g. with fill-column. When I search for a string (C-s) such as this is a long text, the search results would not return the locations where the string appears with a line break between two of the words (like this\nis a long text).

Is there a command that would also return these results?

Answer 1

Take a look at the variables isearch-lax-whitespace, isearch-regexp-lax-whitespace, and search-whitespace-regexp.

If the first two variables are set to something non-nil (e.g. t) any space character in your search string will match any sequence matched by the regular expression defined by the search-whitespace-regexp variable.

To match words across line breaks do this:

;; Make Isearch work across spaces, tabs, and newlines.
(setq isearch-lax-whitespace t
      isearch-regexp-lax-whitespace t
      search-whitespace-regexp "[ \t\r\n]+")

A space character in your query will now match any space, tab, or linebreak any number of times.