how to get region start and region end from the whole buffer as variables to call another func

Question

(defun buffer-to-shell()
  (let (buffer mark-whole-buffer)))
  (shell-command-on-region start end "sed s/foo/bar/") ;; start, end not defined
  )

As you might see there are undefined variables start and end in the function call for shell-command-on-region.

I would like the function buffer-to-shell to just mark the whole active buffer and pass it's region fields to the shell command function. I do not know how to get those to fields out of the result of mark-whole-buffer which I am assigning to the local variable buffer (which also may be redundant.

Solution

(defun buffer-to-shell()
  "push the whole buffer to shell command sed"
  (interactive)
  (shell-command-on-region (point-min) (point-max) "sed s/foo/bar/")
  )

yields Wrong type argument: commandp, buffer-to-shell

Answer 1

You don't need a region when you're calling this function from code. You only need positions in buffer, and you can get these with (point-min) and (point-max).