Pass selected text as argument to a script and replace selected text with output from the script

Question

I'd like to pass some selected text in a buffer to a python script. The python script will process the string and print the result to stdout. This output should replace the original string that was selected. Can this be done?

To tackle this, I first pass a selected buffer to my python script. Below is the elisp function that I wrote, following a similar function to implement the command wc

(defun it ()
  (interactive)
  (shell-command (concat "echo "
                         (buffer-substring (mark) (point))
                         " | /Users/john/bin/t ")))

This command succeeds and prints the output in the mini-buffer. Is there an elisp-way to overwrite the selected text with this output?

Answer 1

Would shell-command-on-region, using a prefix argument fit your requirements? shell-command-on-region is by default bound to M-| (Meta key with '|' key) and the prefix argument is by default bound to C-u (Control 'u').

Combining those you can use the key sequence C-u M-| (Control 'u' followed by Meta '|') to pipe a region of text to a command and replace the region with the output of the command.

It asks for the command to pipe the selected text to, in your example that would be /Users/john/bin/t, and runs that command with the selected text on standard input.

Answer 2

This is perfectly possible and you are almost there. For example to replace e.g. the command/selected text ls in a buffer you can use:

(defun replace-region-from-shell-output ()
  (interactive)
  (let ((command-output (shell-command-to-string (buffer-substring (mark) (point)))))
    (kill-region (mark) (point))
    (insert command-output)))