I'm developing an app in python which sends commands to a running emacs instance. Currently, I start an emacs server and send the commands through the command line, like this:
subprocess.call(['emacsclient', '-e', '(with-current-buffer ' + '(window-buffer (selected-window)) (save-buffer))']) Is there another way to control to emacs externally, like an API? Because this solution I came up with doesn't seem very elegant to me.
I used the TCP approach suggested by @wvxvw in the comments. I'm starting a TCP server inside emacs, which, when receiving a package, will eval it as elisp code. I found a piece of code for the TCP server somewhere in the internet (I can't seem to find it again, if anybody knows please leave a comment and I'll add to the answer), and made a few changes for the code evaluation:
;;; echo-server.el --- -*- lexical-binding: t -*- ;; ;; Copyright (C) 2016-2017 York Zhao <[email protected]> ;; Author: York Zhao <[email protected]> ;; Created: June 1, 2016 ;; Version: 0.1 ;; Keywords: TCP, Server, Network, Socket ;; ;; This file is NOT part of GNU Emacs. ;; ;; This program is free software; you can redistribute it and/or modify it under ;; the terms of the GNU General Public License as published by the Free Software ;; Foundation; either version 3 of the License, or (at your option) any later ;; version. ;; ;; This program is distributed in the hope that it will be useful, but WITHOUT ;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS ;; FOR A PARTICULAR PURPOSE. See the GNU General Public License for more ;; details. ;; ;; You should have received a copy of the GNU General Public License along with ;; this program. If not, see <http://www.gnu.org/licenses/>. ;; ;;; Commentary: ;; ;; Running "M-x tcp-server-start" will prompt user to enter a port number to ;; listen to. ;; ;;; Code: (require 'cl-lib) (defvar tcp-server-clients '() "Alist where KEY is a client process and VALUE is the string") (defvar tcp-server-servers '() "Alist where KEY is the port number the server is listening at") (defvar tcp-server-display-buffer-on-update nil "If non-nil, force the process buffer to be visible whenever new text arrives") (make-variable-buffer-local 'tcp-server-display-buffer-on-update) (defun tcp-server-make-process-name (port) "Return server name of the process listening on PORT" (format "tcp-server:%d" port)) (defun tcp-server-get-process (port) "Return the server process that is listening on PORT" (get-process (tcp-server-make-process-name port))) (defun tcp-server-process-buffer (port) "Return buffer of the server process that is listening on PORT" (process-contact (tcp-server-get-process port) :buffer)) (defun tcp-server-delete-clients (server-proc) (let ((server-proc-name (process-contact server-proc :name))) (cl-loop for client in tcp-server-clients if (string= server-proc-name (process-contact client :name)) do (delete-process client) (message "Deleted client process %s" client)) (setq tcp-server-clients (cl-delete-if (lambda (client) (string= (process-contact server-proc :name) (process-contact client :name))) tcp-server-clients)))) (cl-defun tcp-server-start (port &optional (display-buffer-on-update nil) (buffer-major-mode 'text-mode)) "Start a TCP server listening at PORT" (interactive (list (read-number "Enter the port number to listen to: " 9999))) (let* ((proc-name (tcp-server-make-process-name port)) (buffer-name (format "*%s*" proc-name))) (unless (process-status proc-name) (make-network-process :name proc-name :buffer buffer-name :family 'ipv4 :service port :sentinel 'tcp-server-sentinel :filter 'tcp-server-filter :server 't) (with-current-buffer buffer-name (funcall buffer-major-mode) (setq tcp-server-display-buffer-on-update display-buffer-on-update)) (setq tcp-server-clients '())) ;; (display-buffer buffer-name) )) (defun tcp-server-stop (port) "Stop an emacs TCP server at PORT" (interactive (list (read-number "Enter the port number the server is listening to: " 9999))) (let ((server-proc (tcp-server-get-process port))) (tcp-server-delete-clients server-proc) (delete-process server-proc))) (defun tcp-server-append-to-proc-buffer (proc string) (let ((buffer (process-contact proc :buffer)) (inhibit-read-only t)) (and buffer (get-buffer buffer) (with-current-buffer buffer (when tcp-server-display-buffer-on-update (display-buffer buffer)) (let ((moving (= (point) (point-max)))) (save-excursion (goto-char (point-max)) (insert string) ) (if moving (goto-char (point-max)))))))) (defun tcp-server-filter (proc string) (tcp-eval string)) (defun tcp-eval (string) (eval (car (read-from-string (format "(progn %s)" string))))) (defun tcp-server-sentinel (proc msg) (cond ((string-match "open from .*\n" msg) (push proc tcp-server-clients) (tcp-server-log proc "client connected\n") ) ((string= msg "connection broken by remote peer\n") (setq tcp-server-clients (cl-delete proc tcp-server-clients)) (tcp-server-log proc "client has quit\n") ) ((eq (process-status proc) 'closed) (tcp-server-delete-clients proc)))) (defun tcp-server-log (client string) "If a server buffer exists, write STRING to it for logging purposes." (tcp-server-append-to-proc-buffer client (format "%s %s: %s" (current-time-string) client string))) (provide 'tcp-server) ;;; tcp-server.el ends here Then you can call the tcp-server-start command, informing the port you want it to run, and your server should be ready. Here's a python client example:
import socket def connect(): conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM) conn.connect(('127.0.0.1', 9999)) # ip and port running emacs return conn if __name__ == '__main__': conn = connect() # now you send your desired elisps commands like this: conn.send(b'(next-line)') conn.send(b'(insert "foo bar")') Keep in mind that this code doesn't have any type of firewall, so you should be vulnerable to external attacks.
tcp-server-stop should be used when you're done with the server.
emacsclient, maybe creating a simple TCP socket in on Emacs side which will simply evaluate the code you send it will be more efficient.