Emacs

Table of contents

• Caps-lock vs. Ctrl
• IDL
• LaTeX
• Maxima
• Using RCS or SVN from Emacs
• Running make from Emacs
• Emacs shell
• Emacs RegExps
• Links

Emacs is a versatile text editor available for Unix/Linux. EMACS stands for Escape Meta Alt Control Shift.
It supports many things, including syntax highlighting (for C/C++, IDL, LaTeX, HTML and others) and an interface to RCS (the revision control system). My .emacs file with some customisations is attached to this wiki page.
I recently bought the book Learning GNU Emacs 3rd ed. by Cameron et al. It's a great book, easy to read and even though I've been using Emacs for more than five years now I still learned a lot from it. It's also great as a reference.

These are the basic commands for Emacs:

exit                    Ctrl-x Ctrl-c
save                    Ctrl-x Ctrl-s
save as                 Ctrl-x Ctrl-w
undo                    Ctrl-Shift-_
search                  Ctrl-s
search-replace          Alt-Shift-5

Caps-lock vs. Ctrl

Emacs relies heavily on shortcuts using the Ctrl key, which is quite awkwardly positioned on standard keyboards. You'll find yourself folding your pinky to reach it. On oldskool keyboards (like the one I have for Vitamientje), the Ctrl key was placed where Caps-lock resides these days. But who needs Caps-lock anyway? It usually only there to annoy you when you're logging in and you password doesn't seem to work. So let's just replace it with the control key. The easisest way to do that is to put the line Option "XkbOptions" "ctrl:nocaps" in the InputDevice section for your keyboad in the /etc/X11/xorg.conf file. Furthermore, when using Gnome go to the System menu -> Preferences -> Keyboard and in the Layout Options tab Change the Ctrl key position.

IDL

At http://www.idlwave.org you can find out all about the IDLWave mode for Emacs. This is a great mode to use when programming and running IDL.

LaTeX

Several shortcuts exist when using Emacs to edit LaTeX files. See the LaTeX page.

Maxima

Maxima is a Computer Algebra System, much like Mathematica. And, good thing, there's a maxima-mode in Emacs. Even better is the imaxima-mode available here. It formats maxima's output using LaTeX!
The maxima-mode is available in the UbuntuLinux repositories, but the imaxima-mode has to be installed by hand (pretty simple using configure, make, make install). The add these lines to your .emacs file:
;; Autoload the imaxima files from /usr/local/
(autoload 'imaxima "imaxima" "Image support for Maxima." t)
(autoload 'imath-mode "imath" "Interactive Math minor mode." t)
(setq imaxima-fnt-size "Large")
(setq imaxima-use-maxima-mode-flag t)

Using RCS or SVN from Emacs

If you use the emacs editor to edit a file registered with RCS, you can give emacs commands to perform the necessary co -l and ci -u operations and thus avoid using separate shell commands. The commands you give to emacs are nicely listed at http://www.credmp.org/2007/12/08/emacs-hidden-gems-version-control/. See also the EmacsWiki entry.

Running make from Emacs

When working on programming projects for example, Emacs can call the make utility (M-x compile) to build your project. It captures the output in an Emacs window and using C-x ` (Ctrl-X followed by the back tick you can parse through the errors while emacs tries to look up the line where the error was produced. In my personal .emacs file (the first of the links below) I bound the key C-x m to this command to save some typing.

Emacs shell

In order to make the emacs shell print the colored output of e.g. the ls command right (i.e. without showing the ANSI excape sequences) use the foloowing command: M-x ansi-color-for-comint-mode-on.
These are the sheel cusomisations I have in my .emacs:

;; Interpret and use ansi color codes in shell output windows
(ansi-color-for-comint-mode-on)
(setq comint-scroll-to-bottom-on-input t)  ; always insert at the bottom
(setq comint-scroll-to-bottom-on-output t) ; always add output at the bottom
(setq comint-scroll-show-maximum-output t) ; scroll to show max possible output
(setq comint-completion-autolist t)        ; show completion list when ambiguous
(setq comint-input-ignoredups t)           ; no duplicates in command history
(setq comint-completion-addsuffix t)       ; insert space/slash after file completion
;; Hide passwords in Emacs shell
(add-hook 'comint-output-filter-functions 'comint-watch-for-password-prompt)
;; make completion buffers disappear after 3 seconds.
(add-hook 'completion-setup-hook
  (lambda () (run-at-time 3 nil
    (lambda () (delete-windows-on "*Completions*")))))

Emacs RegExps

Regular expressions in Emacs are a bit different from the ones in e.g. Perl or grep. For example there are no POSIX compliant constructions like :digit: .
Stevey's blog on Emacs RegExps shows some examples.
To insert the newline character in RegExp searches use: C-q C-j.
A table of the special RegExp characters can be found here at 3monkeyweb.com's Emacs tutorial.

Links

• My personal .emacs file can be found here.
• The Emacs Reference Card at refcards.com.
• Emacs Reference Chart
• The Emacs Wiki at emacswiki.org.
• Sams Teach Yourself Emacs in 24 Hours, the full text of the book (1999).
• On-the-fly spell checking in Emacs
• Check out http://tulrich.com/geekstuff/emacs.html and this linux journal article for tips on using etags to navigate through source code.
• Minor emacs wizardry, a blog.
• M-x all-things-emacs, another blog.

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