How to execute external commands from an Eshell script

Question

I would like to create an elisp function such as

(defun script()
 (run "bash" "-c" "echo 1; sleep 3; echo 2")
 (eshell-print "Done")) 

From an Eshell, its execution should look like:

eshell $ script
1
2
Done
eshell $

With the following requirements:

• the stdout of the bash process has to be "streamed" in the eshell buffer.

• it must be possible to C-c the script

Any idea on how to do that?

Answer 1

You can copy the following Elisp code to your init files.

It contains a modified version of function eshell-source-file. Essentially I changed (insert-file-contents file) to (insert string). Furthermore I needed a minor modification of 'eshell-command-name.

It also contains the function define-eshell-script defining an Eshell command with a doc string and an Eshell script given by a string. The script takes care of the formalities for the script required by Eshell internals (e.g., correctly registering in the list variable eshell-complex-commands). Those formalities make the newly defined command interruptible.

(require 'cl-lib) ;; for macro `cl-pushnew' (not autoloaded ?!)
(require 'esh-cmd) ;; for variable `eshell-complex-commands'

(defun eshell-source-string (string &optional args subcommand-p)
  "Execute a series of Eshell commands in STRING, passing ARGS.
Comments begin with `#'."
  (interactive "sString to be evaluated as eshell script: ")
  (let ((orig (point))
    (here (point-max))
    (inhibit-point-motion-hooks t))
    (goto-char (point-max))
    (with-silent-modifications
      ;; FIXME: Why not use a temporary buffer and avoid this
      ;; "insert&delete" business?  --Stef
      (insert string)
      (goto-char (point-max))
      (throw 'eshell-replace-command
             (prog1
                 (list 'let
                       (list (list 'eshell-command-name (list 'quote "source-string"))
                             (list 'eshell-command-arguments
                                   (list 'quote args)))
                       (let ((cmd (eshell-parse-command (cons here (point)))))
                         (if subcommand-p
                             (setq cmd (list 'eshell-as-subcommand cmd)))
                         cmd))
               (delete-region here (point))
               (goto-char orig))))))

(defun define-eshell-script (cmd doc string)
  "Define CMD as eshell script STRING with documentation DOC.
CMD can be a string or a symbol."
  (let ((fun (intern (concat "eshell/" cmd))))
    (fset fun
      `(lambda (&rest args)
        ,doc
        (eshell-source-string ,string args)))
    (cl-pushnew cmd (default-value 'eshell-complex-commands) :test #'equal)
    (dolist (buffer (buffer-list))
      (with-current-buffer buffer
    (when (derived-mode-p 'eshell-mode)
      (cl-pushnew cmd eshell-complex-commands :test #'equal))))
    (put fun 'eshell-no-numeric-conversions t)))

If the above functions are available you can define your actual script with the help of define-eshell-script as follows.

(define-eshell-script "script" "The doc-string: Output 1, sleep, and output 2."
   "bash -c \"echo 1; sleep 3; echo 2;\"
echo DONE")

The usage example in Eshell looks like you want it:

/Path/to/current/dir $ script
1
2
DONE
/Path/to/current/dir $

Answer 2

I am having a blast using eshell on MS Windows, even forgetting sometimes I am not on GNU/Linux, and I think I have two nice examples that some of you can relate to.

For console applications (your case):

(defun eshell/vbox-startvm-headless (name)
  "VBoxManage.exe startvm <vmname> --type headless"
  (let* ((cmdlist (list (shell-quote-argument (vboxmgr-path)) "startvm" name "--type" "headless")))
    (message (format "%S" cmdlist))
    (throw 'eshell-replace-command (eshell-parse-command (car cmdlist) (cdr cmdlist)))))

(add-to-list 'eshell-complex-commands "vbox-startvm-headless")

For GUI applications:

(defun eshell/virtualbox (&optional args)
  "VirtualBox.exe [args...]"
  (start-process "virtualbox" nil (virtualbox-path)))

The snippets above are from my init.el and they rely on vboxmgr-path and virtualbox-path to point to VBoxManage.exe and VirtualBox.exe, respectively.