CODEWITHSUNDEEP
emacsregion
Yu Shen
Yu Shen

Reputation: 2910

Get the content as string of a region in a buffer by elisp program

Here is the problem that I'm solving: Convert a region of text into a string data structure for subsequent processing by elisp program. The challenge is that

  1. I want to execute an elisp program interactively without affecting the selection of a region
  2. store the string value into a variable so that I can further manipulate it.

By my understanding, a region is defined by a mark and the subsequent cursor position. And I usually execute elisp program in *scratch* buffer. Furthermore, the region is also in the *scratch* buffer.

But to write the function call and execute it in the buffer, I need to move the cursor away from the end of the text selection (region) in order to write the program of

(setq grabbed (buffer-substring-no-properties (region-beginning) (region-end)))

but then the region of selection would change due to the cursor movement.

So I wonder how I could execute the elisp program while keeping the selection intact and still can access the return value.

Upvotes: 0

Views: 1577

Answers (2)

Yu Shen
Yu Shen

Reputation: 2910

Finally, I found a desirable solution! It's using ielm buffer, the real repl of elisp. In the ielm buffer, I can set working buffer (by C-c C-b) to be a buffer where I have the text to be manipulated, for example, *scratch*.

I can then select a region of the working buffer to be processed, and in the ielm buffer then I can type and execute elisp code to extract the text in the selected region in the working buffer, for example,

ELISP> (setq grabbed (buffer-substring-no-properties (region-beginning) (region-end)))
"One\nTwo\nThre"
ELISP> grabbed
"One\nTwo\nThre"
ELISP> (split-string grabbed)
("One" "Two" "Thre")

I can then work with the value held by the set variable, grabbed.

Here is a very helpful description of ielm: https://www.masteringemacs.org/article/evaluating-elisp-emacs

Upvotes: 0

Stefan
Stefan

Reputation: 28531

If you want to run the function from some Elisp code but as if the user had invoked it via a keybinding, you can use call-interactively:

(setq variable-to-keep-the-value (call-interactively 'lines-to-list))

But in most cases, what you want instead is to take yourself the responsibility to choose to which part of text the function should apply:

(setq variable-to-keep-the-value 
      (lines-to-list (region-beginning) (region-end)))

Notice that the region's boundaries are nothing magical, regardless if they've been set by the mouse or what.

Upvotes: 2

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