How to redirect output from eshell to any open buffer in Emacs?

Question

I have my eshell opened in a window and in another window I have *Scratch* as a open buffer. I want to redirect the output of a command like say ls to *Scratch*. Is it possible? If yes, then how can I do it? Thanks.

Answer 1

Yes:

ls >(get-buffer "*scratch*")

Or even

ls > #<buffer *scratch*>

See this question for more details.

Answer 2

The following answer uses a different approach than was suggested by the original poster. In this example, we use shell-command-to-string: https://www.gnu.org/software/emacs/manual/html_node/elisp/Synchronous-Processes.html

The default-directory in this example is hard-coded to "~/", which may or may not be the default-directory of the *scratch* buffer. We use let* (instead of just plain old let) so that shell-command-to-string respects the hard-coded default-directory that was let*-bound on the preceding line. If the *scratch* buffer did not already exist, then a new one will be created and its default-directory will be "~/". We go to the bottom of the *scratch* buffer just in case point was somewhere else. If the buffer is not already visible, then display it in another window.

To try out this example, type M-x eval-expression and paste the snippet into the mini-buffer when prompted and press the return key.

(let* ((default-directory "~/")
       (string (shell-command-to-string "ls"))
       (buffer (get-buffer-create "*scratch*")))
  (with-current-buffer buffer
    (goto-char (point-max))
    (insert string))
  (unless (get-buffer-window "*scratch*")
    (display-buffer buffer t)))