Change "ls" from emacs dired to other app - linux

Question

I wrote some script in elisp, it merges ls -l and du (showing real folder size instead of what is written in ls). I named it lsd. Here is screenshot:
http://i.imgur.com/PfSq6.png
Now i'll list implementation. I am not a good coder, so I will appreciate any information about bugs and things that can be made better.
lsd.el
#!/usr/bin/emacs --script
(progn
(setq argz command-line-args-left)
(setq folder "./")
(while argz
;; (message (car argz))
(if (/= ?- (aref (car argz) 0))
(setq folder (car argz)))
(setq argz (cdr argz)))
(if (/= ?/ (aref folder (1- (length folder)))) (setq folder (concat folder "/")))
(switch-to-buffer " *lsd*")
(erase-buffer)
(shell-command (concat "ls -l -h --color=always " " " (apply 'concat (mapcar '(lambda(arg) (concat arg " ")) command-line-args-left))) (current-buffer))
(switch-to-buffer " *du*")
(erase-buffer)
(shell-command (concat "du -h -d 1 " folder) (current-buffer))
(goto-char 1)
(while (search-forward "Permission denied" (point-max) t nil)
(goto-char (point-at-bol))
(let ((beg (point)))
(forward-line)
(delete-region beg (point)))) ; Remove all permission denied lines, thus show only permitted size.
(goto-char 1)
(while (and (search-forward folder (point-max) t nil) (/= (point-max) (1+ (point-at-eol)))) ; we do not need last line(the folder itself), so this line is something complex.
(setq DIR (buffer-substring (point) (point-at-eol)))
(goto-char (point-at-bol))
(setq SIZE (buffer-substring (point) (1- (search-forward " " (point-at-eol) nil nil))))
(goto-char (point-at-eol))
(switch-to-buffer " *lsd*")
(goto-char 1)
(if (search-forward DIR (point-max) t nil)
(progn
(goto-char (point-at-bol))
(search-forward-regexp "[0-9]+" (point-at-eol) nil nil)
(search-forward-regexp " *[0-9]+[^ \n]*[ \n]*" (point-at-eol) nil nil)
;; If ls have options, that makes some numbers before size column - we are doomed. (-s, for example)
(setq SIZE (concat SIZE " "))
(while (< (length SIZE) (length (match-string 0))) (setq SIZE (concat " " SIZE)))
(replace-match SIZE)))
(switch-to-buffer " *du*"))
(switch-to-buffer " *lsd*")
(message "%s" (buffer-substring (point-min) (point-max)))
(defun error(&rest args) args)
(defun message(&rest args) args)) ; Do not show any messages.
lsd
(I made this script to start emacs without loading anything but script. If it can be done easier, please point this)
#/bin/bash
emacs -Q --script /usr/local/bin/lsd.el $#
And here is the problem: how to use this lsd in dired?
Can I change something in dired to use lsd instead of ls?
Can I rename ls in oldls, and make some ls bash script that passes all arguments to ls if there no --lsd flag, and passing all arguments to lsd if --lsd is here?
Is it good idea at all?

Answer 1

In Emacs24 there is also `insert-directory-program' to set the ls executable. Put
(setq insert-directory-program "/usr/local/bin/lsd")
(adjust the path accordingly) in your .emacs or init.el and dired takes your lsd script.

Answer 2

I don't know if this the most efficient way to do things, I'm still a bit of an Emacs beginner. But here's how I would do it.
Since you're on Linux you should start by telling emacs to use its built-in ls emulation. A simple (require 'ls-lisp) in your init file should suffice.
Set the variable ls-lisp-use-insert-directory-program to true. This tells emacs to use an external program for ls.
The actual program it uses can be customized by setting the variable insert-directory-program to point to your lsd script.
Here's an example of how to do this:
;; Put this in your init file
(require 'ls-lisp)
(setq ls-lisp-use-insert-directory-program T)
(setq insert-directory-program "~/path/to/lsd")
Let me know if this works for you. I use emacs on Windows so I'm not sure how well this ports over to linux (the ls emulation part that is).