Irreal

I was reading some of the old posts from the excellent emacs-fu when I came across this post describing how to access root-owned files as a regular user. It was a nice post and cleared up an arcane piece of syntax that I never understood. In order to edit a root-owned file on the local host you enter something like:【Ctrl+x Ctrl+f】/sudo::<path-to-root-owned-file>. The double colon seemed different from other similar constructs but all that’s happening is that /sudo:: is really just a shortcut for sudo‘s default, which is /sudo:root@localhost:.

That’s interesting and cleared up something that never made sense to me but the interesting lesson from the post occurred in the comments. One of the commenters complained that this still didn’t help with the common case of wanting to edit root files on a remote machine. If you try to do this, Emacs (Tramp, really) complains that sudo can only be used on the local host. However, it turns out that you can use the Tramp multihop facility to enable this functionality. This is explained in detail in the info page at Tramp > Configuration > Multi-hops, but the TL;DR is to add the three commands

(require 'tramp)
(add-to-list 'tramp-default-proxies-alist
             '(nil "\\`root\\'" "/ssh:%h:"))
(add-to-list 'tramp-default-proxies-alist
             '((regexp-quote (system-name)) nil nil))

to your .emacs or init.el file. Then you can edit remote root files with 【Ctrl+x ctrl+f】 /sudo:root@remote-host:<path-to-root-owned-file>.

In my ELPA With Emacs 24 post, I documented some of the problems I was having getting ELPA to work with Emacs 24 and showed some Elisp to work around the problem. Fortunately, my readers are a lot smarter than I am and suggested better ways of getting things to work.

The answer turns out to be pretty simple. I replaced all my special code for setting paths and requiring package with:

(package-initialize)
(add-to-list 'package-archives
             '("marmalade" . "http://marmalade-repo.org/packages/"))

and left everything else the same. So far that seems to be working perfectly. The documentation isn’t really clear on this and, in fact, hints that putting

(package-initialize)

in your .emacs or init.el file can cause problems with other packages. I haven’t seen that and neither have any of my commenters so unless I run into problems later, my recommendation is to simply add the package-initialize near the top of your .emacs or init.el.

None of this means, of course, that you won’t have to configure some of the packages you load with ELPA but at least Emacs won’t throw an error during startup because of missing packages. Thanks to Seth, Philipp, and Foo for their helpful comments.

DJCB, over at Emacs-Fu, takes note of the new line number command in Emacs 24 that Sivaram wrote about in Got Emacs? and offers up a few suggestions of his own. He shows a very nice trick for accomplishing the same thing and more using replace-regexp. It’s a little more complicated than rectange-number-lines so you probably won’t want to use it except for those cases where rectangle-number-lines (along with its optional FORMAT argument) can’t give you the desired result. Of course, if you’re still using an older version of Emacs it’s a nice way of getting the same functionality that rectangle-number-lines provides.

Many (many) years ago when I was a freshman at RPI, we called the weekly Physics mass lecture “The Magic Show” because the lectures were spectacular demonstrations that illustrated whatever principle we were studying that week. This week I had the same feeling as I watched Magnar Sveen (of Emacs Rocks! fame) deliver a talk at Web Rebels in Oslo. The sound quality was a little substandard and the pace was rapid but like those old physics lectures it was a spectacular demonstration. In this case, a demonstration of the power of Emacs and its extensibility.

Sveen started by saying that unfortunately Emacs doesn’t have a slide show capability and then put one together right before our eyes. Then he spent the rest of the 18 minutes showing off some of the micro-optimizations he’s developed to speed up his editing. One of these, his multicursor enhancement, was startling and has to be seen to be believed.

This is a really great video, sort of like Emacs Rocks! on steroids. You won’t learn how to program these enhancements or even how to use them, just what’s possible with Emacs. Fortunately, all of Sveen’s code is available on GitHub so you can download the code and try it yourself. The multiple cursor stuff is still very young but worth playing with. I’m looking forward to seeing it on Marmalade when it gets a little more mature.

If you’re an Emacs user and especially if you enjoy the Emacs Rocks! videos you should definitely spend 18 minutes on this talk. You won’t be sorry.

I just installed Emacs 24 and, as expected, everything went very well except for the package system, ELPA. I don’t have very many packages that I load with ELPA so at least the number of problems were limited.

First, following Xah Lee’s Guide on Emacs 24 Package System page, I moved the old ~/.emacs.d/elpa directory out of the way and then reloaded my packages. The first problem is that you need to replace the

(when
    (load
     (expand-file-name "~/.emacs.d/elpa/package.el"))
  (package-initialize))

with

(require 'package)

After that change I was able to add Marmalade to the list of package sites.

The next problem was that when I restarted Emacs, I got an error saying it couldn’t load smex, one of the packages that I load with ELPA. Everything seemed OK: smex was loaded onto my machine and seemed fine. The bit of Elisp in init.el was what the documentation said it should be but I couldn’t get it to load from init.el. I went searching on the Web and after a few useless links I found this page on Emacs 24 Package System Problems, again from Xah Lee. In order to get things to work you have to add an explicit load path for some of the packages (smex, magit, dired+, and key-chord for me). My first pass at this was to add commands to explicitly add the load paths:

(add-to-list 'load-path "~/.emacs.d/elpa/smex-1.1.2/") ; XXX Emacs bug
(require 'smex)
(smex-initialize)
(global-set-key (kbd "M-x") 'smex)
...

This is annoying because the path will have to be changed when I upgrade. It’s doubly annoying because ELPA worked just fine without having to do this in Emacs 23. Rather than keep dealing with this every time I upgrade one of the problem packages, I added

(defconst elpa-loads '("smex" "magit" "dired" "key-chord"))
(mapc (lambda (p) (if (file-directory-p p) (add-to-list 'load-path p)))
      (directory-files "~/.emacs.d/elpa" t
                       (concat "^\\("
                               (mapconcat 'identity elpa-loads "\\|")
                               "\\).*")))

to my init.el. With that change, the only maintenance required is to add any new problem packages to elpa-loads.

The Emacs 24 ELPA problem appears, from some of the other links I looked at, to be that Emacs 24 deals with the ELPA packages after it has finished processing the .emacs or init.el file and, therefore the .emacs or init.el file knows nothing about the packages. That means you can’t set package variables because they haven’t been loaded yet. As far as I could find out, the only solution is to load the files with require and that requires that there be a path to the .el or .elc files.

Doubtless, this will all be resolved soon so I’m not overly exercised about it. Now that I have things working again, it’s time to explore the new Emacs 24 and see how it improves my life.

Update: Added explicit check for directory when setting paths.

Back in March, I blogged about installing ELPA in Emacs 23. At the time I pointed to a page by Xah Lee on how to do this. Now that Emacs 24 is out it’s worthwhile revisiting the Emacs package system. In Emacs 24, ELPA is built in so all that’s necessary is to set the repositories that you want to get packages from.

Again, Xah Lee has us covered with an updated page. If you’ve recently updated to Emacs 24 and don’t know about ELPA, you should take a look at Lee’s page about it. He’s got all the information on how to use it and how to upgrade from ELPA for Emacs 23 to ELPA for Emacs 24. Once you get ELPA set up, everything is much easier. You can download packages and have them available without having to worry about setting up paths or special directories. It’s easy to update and delete packages so there’s no need to worry about checking in with a package’s home page to see if there’s an update—ELPA will tell you.

If you’re an Emacs user and aren’t using ELPA you’re making your life more difficult than it has to be. Seriously, check out Lee’s page and get ELPA up and running. It will make your life a lot better.