Using replace-regexp with a shell command

Question

I'm trying to format some text that matches a regexp using an external shell command. I've been able to use C-u M-| successfully on a region, but I can't figure out how to do that within replace-regexp.

I've tried using \,(shell-command-on-region point-min point-max "python -m json.tool") as the second argument to replace-regexp, but I get Error evaluating replacement expression: (void-variable point-min).

Is there a way to use replace-regexp with shell-command-on-region?

Answer 1

point-min and point-max are functions not variables. So try this instead:

(shell-command-on-region (point-min) (point-max) "python -m json.tool")

Is there a way to use replace-regexp with shell-command-on-region?

Yes, but not combining them properly is not what the error message is about. But I can see where your confusion is coming from: "Error evaluating replacement expression:". That's additional information intended to help you figure out in what context the void-variable error occurred. Unfortunately it did the opposite.

Edit: as pointed out in the comments there are a few more issues. I won't walk you though all of them; I suggest you read the documentation about the involved functions instead. But here is some code that should do the trick.

(let ((buf (generate-new-buffer " *temp*")))
  (shell-command-on-region (point-min) (point-max)
                           "python -m json.tool" buf)
  (with-current-buffer buf
    (goto-char (point-min))
    (replace-regexp "regexp" "replacement")
    (buffer-string))
  (kill-buffer buf))