showing pop-ups

Updated: yes, it's %s, not %d Sometimes, it's nice when emacs can warn you when something is happening or should happen. For example, when a new e-mail has arrived, or when there's a meeting in 15 minutes you should attend.

As always, there are different way to do this, but here's what I've been using for while. Various versions of this have been circulating around mailing lists, so I don't know whom to credit with the original idea – anyway, this is the (modified) version that I'm using.

(defun djcb-popup (title msg &optional icon sound)
  "Show a popup if we're on X, or echo it otherwise; TITLE is the title
of the message, MSG is the context. Optionally, you can provide an ICON and
a sound to be played"

  (interactive)
  (when sound (shell-command
                (concat "mplayer -really-quiet " sound " 2> /dev/null")))
  (if (eq window-system 'x)
    (shell-command (concat "notify-send "

                     (if icon (concat "-i " icon) "")
                     " '" title "' '" msg "'"))
    ;; text only version

    (message (concat title ": " msg))))

A couple of notes:

• I'm using notify-send for sending notifications; this assumes you are using that system (it's part of the libnotify-bin package in Debian/Ubuntu). You can of course replace it with whatever is available on your system. Alternatives are zenity or kdialog or xmessage (for old-timers) and their equivalents (?) on Windows, MacOS.
• I'm now using mplayer for playing sounds. This is a bit heavy, but at least plays all kinds of audio files. If you only care about .wav-files, you could replace it with e.g. aplay;
• as always, please ignore my ego-centric function names :-)

Now, we can use this function by evaluation e.g.

(djcb-popup "Warning" "The end is near"
   "/usr/share/icons/test.png" "/usr/share/sounds/beep.ogg")

showing pop-ups from org-mode appointments

The above popup function is most useful when it's does its work based on some event. To be notified of appointments and the like, there is the emacs appt facility. Here, we set up this appt, and then hook it up with org-mode, so appt can warn us when there's something happening soon…

;; the appointment notification facility
(setq
  appt-message-warning-time 15 ;; warn 15 min in advance

  appt-display-mode-line t     ;; show in the modeline
  appt-display-format 'window) ;; use our func
(appt-activate 1)              ;; active appt (appointment notification)
(display-time)                 ;; time display is required for this...

 ;; update appt each time agenda opened

(add-hook 'org-finalize-agenda-hook 'org-agenda-to-appt)

;; our little façade-function for djcb-popup
 (defun djcb-appt-display (min-to-app new-time msg)
    (djcb-popup (format "Appointment in %s minute(s)" min-to-app) msg 
      "/usr/share/icons/gnome/32x32/status/appointment-soon.png"

      "/usr/share/sounds/ubuntu/stereo/phone-incoming-call.ogg"))
  (setq appt-disp-window-function (function djcb-appt-display))

Of course, you can freely choose a icon / sound to your liking.

showing pop-ups for new mail

Another event you might want to be warned about is new mail. There is something to be set for not letting yourself be disturbed for new mail, but if you sufficiently filter your mails before they enter your inbox, it can be a good way to periodically bring you back from your deep sl ^H^H thinking. For Wanderlust, I use something like this:

(add-hook 'wl-biff-notify-hook
    (lambda()
      (djcb-popup "Wanderlust" "You have new mail!"
        "/usr/share/icons/gnome/32x32/status/mail-unread.png"
        "/usr/share/sounds/ubuntu/stereo/phone-incoming-call.ogg")))

Exercise for the reader: adapt this for your chosen mail client.

copying lines without selecting them

When I'm programming, I often need to copy a line. Normally, this requires me to first select ('mark') the line I want to copy. That does not seem like a big deal, but when I'm in the 'flow' I want to avoid any little obstacle that can slow me down.

So, how can I copy the current line without selection? I found a nice trick by MacChan on EmacsWiki to accomplish this. It also adds ta function to kill (cut) the current line (similar to kill-line (C-k), but kills the whole line, not just from point (cursor) to the end.

The code below simply embellishes the normal functions with the functionality 'if nothing is selected, assume we mean the current line'. The key bindings stay the same (M-w, C-w).

To enable this, put the following in your .emacs:

(defadvice kill-ring-save (before slick-copy activate compile) "When called
  interactively with no active region, copy a single line instead."
  (interactive (if mark-active (list (region-beginning) (region-end)) (message
  "Copied line") (list (line-beginning-position) (line-beginning-position
  2)))))

(defadvice kill-region (before slick-cut activate compile)
  "When called interactively with no active region, kill a single line instead."
  (interactive
    (if mark-active (list (region-beginning) (region-end))
      (list (line-beginning-position)
        (line-beginning-position 2)))))

It also shows the power of Emacs-Lisp with the defadvice-macro – see the fine documentation. Using defadvice, you can 'decorate' any function with your own modifications. This great power should be used with caution, of course, as to not break other usage that assumes the undecorated versions. In this case, that seem unlikely. And note that the 'advise' only applies when the functions are called interactively.

bookmarks

Emacs has a very useful system for bookmarks – shortcuts to often-used files. It's also one of those features I only really started using after years of emacs – there seem to be many of such obvious features…

Bookmarks are especially handy if you have long file names, or for examples the special file names for editing root-owned files discussed here before.

To start using bookmarks effectively, there are only a few important key bindings to memorize: C-x r m ('make') will create a new bookmark, defaulting to the current file. Then, you can jump to an existing bookmark with C-x r b ('bookmark') Finally, you can see the list of your bookmarks with C-x r l ('list').

There are a few customizations you can put in your .emacs:

(setq 
  bookmark-default-file "~/.emacs.d/bookmarks" ;; keep my ~/ clean
  bookmark-save-flag 1)                        ;; autosave each change)

editing files owned by root with tramp

One of the times when many emacs-users still reach for vi is when editing system configuration files – the stuff in /etc/, etc. I think that is because of the now mostly false impression that emacs startup is slow, and because people don't want to run an open-ended program as emacs as root.

There is truth in that last point – but it applies just as well to, say, vim. Anyway, running emacs as root is not a good idea.

So how what can we do it? Easy! Using the tramp package (included with GNU/Emacs since version 22), you can run emacs as a normal user, but edit root-and-other-owned files. It does its magic using sudo, but you won't normally notice. It does require you to have sudo-rights of course.

How does this work? Well, instead of

C-x C-f /etc/hosts

to open a file as a normal user, you use:

C-x C-f /sudo:root@localhost:/etc/hosts

or even shorter, as noted by Alexander Kojevnikov (because Tramp defaults to root@localhost):

C-x C-f /sudo::/etc/hosts

It asks for a password - and you should use your user password for that (not the root password!). This usually works fine, but due to way Tramp works, it can get confused if root has some very weird command prompt. If so, you of course configure tramp. Also note that sudo usually remembers that you logged in, an does not require you to re-enter you password when opening ('visiting') another file for some time period – but you can change this. See the sudo(8).

This automatically invokes tramp which does all the magic for you. If you don't like the somewhat longer (pseudo)paths for files, you can of course use the emacs bookmarks facilty. After you load the file, you can use it like any other file.

Note, this is only of the many useful things you can do with Tramp. Tramp was actually written for editing files on remote machines (using ssh or other protocol), and I very happily used it to edit files on some European machine whilst in Australia. It caches the file locally, and only sends it over when you save it, so it very fast – it simply makes you forget your file is so far away.

writing presentations with org-mode and beamer

[Updated:fixed an error in the template] Things have been a bit quiet at Emacs-Fu lately; this is mostly because I have been very busy with work, traveling, traveling for work etc. Emacs-wise, this has been a very intensive time, and I have been able to move more and more task to emacs – both professionally and privately. This is mostly because thing become easier when I can do all my things in one place.

Anyhow, one of the tricks I picked up recently is to write presentations with the combination of org-mode and a LaTeX-package called beamer. The most common tool for doing presentations is Microsoft's Powerpoint program. It gets a lot of criticism, most famously from prof. Tufte in his Powerpoint is Evil essay. Of course, the problem is in misuse of the tool, not so much the tool itself.

Still, I didn't want to use Powerpoint (or Powerpoint-wannabees, like OpenOffice's Impress). For the technically-inclined, the knee-jerk reaction to this kind of problem is to shout 'LaTeX!'. Indeed - the LaTeX text-processing system offers a package called Beamer, which allows you to write presentations with LaTeX. It is quite powerful, and even allows for all kinds of fancy graphical bling (fade-in, fade out etc.); even better, it generates PDF-files, which can be viewed just about anywhere. The various themes and color settings it offers are quite nice, even though they tend to fill only a small corner of the design-universe…

beamer and org-mode

Now, while I am no stranger to LaTeX, especially for writing a quick presentation, it can be a painful to remember the various directives and options. I am not really a daily LaTeX-user, so I tend to forget these things. I am a daily org-mode user though, and org-mode can export to LaTeX (which then, in turn, are translated into PDFs). So why not use org-mode to generate presentations?

It turns out that that is quite easy.

First, we need to define some of the LaTeX-boilerplate, and tell org-mode about it, so we never need to think about it again. Put the following in your .emacs:

;; allow for export=>beamer by placing

;; #+LaTeX_CLASS: beamer in org files
(unless (boundp 'org-export-latex-classes)
  (setq org-export-latex-classes nil))
(add-to-list 'org-export-latex-classes
  ;; beamer class, for presentations
  '("beamer"
     "\\documentclass[11pt]{beamer}\n
      \\mode<{{{beamermode}}}>\n
      \\usetheme{{{{beamertheme}}}}\n
      \\usecolortheme{{{{beamercolortheme}}}}\n
      \\beamertemplateballitem\n
      \\setbeameroption{show notes}
      \\usepackage[utf8]{inputenc}\n
      \\usepackage[T1]{fontenc}\n
      \\usepackage{hyperref}\n
      \\usepackage{color}
      \\usepackage{listings}
      \\lstset{numbers=none,language=[ISO]C++,tabsize=4,
  frame=single,
  basicstyle=\\small,
  showspaces=false,showstringspaces=false,
  showtabs=false,
  keywordstyle=\\color{blue}\\bfseries,
  commentstyle=\\color{red},
  }\n
      \\usepackage{verbatim}\n
      \\institute{{{{beamerinstitute}}}}\n          
       \\subject{{{{beamersubject}}}}\n"

     ("\\section{%s}" . "\\section*{%s}")
     
     ("\\begin{frame}[fragile]\\frametitle{%s}"
       "\\end{frame}"
       "\\begin{frame}[fragile]\\frametitle{%s}"
       "\\end{frame}")))

  ;; letter class, for formal letters

  (add-to-list 'org-export-latex-classes

  '("letter"
     "\\documentclass[11pt]{letter}\n
      \\usepackage[utf8]{inputenc}\n
      \\usepackage[T1]{fontenc}\n
      \\usepackage{color}"
     
     ("\\section{%s}" . "\\section*{%s}")
     ("\\subsection{%s}" . "\\subsection*{%s}")
     ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
     ("\\paragraph{%s}" . "\\paragraph*{%s}")
     ("\\subparagraph{%s}" . "\\subparagraph*{%s}")))

This is based on the template by Thomas S. Dye on the org-mode mailing list. You can of course add other packages to it with \usepackage. In my version, I have add the Listings-package for including syntax-highlighted snippets of source code in my presentations. Importantly, I added the [fragile] options to the frame-settings, otherwise you cannot include such source code fragments without LaTeX complaining in various unhelpful ways.

Note, you can customize the way the Listings package works by changing the template above; or by setting the options in the org-file; this involves some 'raw LaTeX' though. It might make sense to define some macros for that.

Now, we can easily make a presentation in org-mode; simply start the file with something like:

#+LaTeX_CLASS: beamer
#+MACRO: BEAMERMODE presentation
#+MACRO: BEAMERTHEME Antibes
#+MACRO: BEAMERCOLORTHEME lily
#+MACRO: BEAMERSUBJECT RMRF
#+MACRO: BEAMERINSTITUTE Miskatonic University, Astrology Dept.
#+TITLE: Presentation with Org-Mode and Beamer
#+AUTHOR: Someone

Of course, you can change these parameters; for example, you might want to change the BEAMERTHEME into Madrid or Warsaw, or … – see the Beamer User Guide (PDF).

After having set up these things, you can write presentations in the familiar org-mode mark-up.

including source code

As mentioned before, you can use the listings-package to include source code snippets in your presentation. You'd write this something like:

#+BEGIN_LaTeX
\begin{lstlisting}[language=c]
for (int i = 1; i != 10; ++i) 
    std::cout << i << ": hello, world!"
              << std::endl;
\end{lstlisting}

#+END_LaTeX

In other words, we include some 'raw' LaTeX to do this. Now, the org-mode-way of doing this, would be to use something like

#+BEGIN_SRC c
  /* code */
#+END_SRC

as discussed before. This works well when exporting to HTML, but at this moment this will simply translate into a verbatim environment in LaTeX - so we use lstlisting to get some syntax-highlighting.

including pictures

Of course, the full arsenal of org-mode tools is available as well, for example Ditaa, as discussed before. Ditaa is now shipped as part of org-mode, and you can use it to create picture which are then included in your presentation. Very nice.

For including existing images (PNGs, JPGs etc.), it's probably easiest to put use some raw LaTeX for that, e.g., something like

#+LaTeX:\includegraphics{/some/path/emacs.png}

putting it together

Now, let's put it all together. Below is an example presentation. Assuming you have everything installed (ie., LaTeX with the listings package, a fairly recent org-mode, ditaa), you create your presentation.org and then press C-c C-e d and your presentation (presentation.pdf) is generated and automatically shown in your PDF-viewer. Easy!

The intermediate files (such as presentation.tex) are there as well, so you can check them if something went wrong.

I have uploaded the resulting PDF to Slideshare, so you can see what it looks like. However, the Slideshare-converted version is extremely blurry, unlike the crisp PDF I actually created. I'd be happy to upload the file somewhere else if someone can point me to a good place, thanks!

So hopefully this shows that you can quite easily make presentations with org-mode, with some help from Beamer, LaTeX etc. Beamer actually provides a lot more, such as funky slide-transitions and other tricks – but the things here should give you a good starting point.

#+LaTeX_CLASS: beamer
#+MACRO: BEAMERMODE presentation
#+MACRO: BEAMERTHEME Antibes

#+MACRO: BEAMERCOLORTHEME lily
#+MACRO: BEAMERSUBJECT RMRF
#+MACRO: BEAMERINSTITUTE Miskatonic University, Astrology Dept.
#+TITLE: Presentation with Org-Mode and Beamer
#+AUTHOR: Someone

* My presentation

** Overview

   1. Introduction

   2. Main part

   3. Questions
    
    
** Some interesting stuff
    
*** an important point
    
    - subpoint a
      
    - subpoint b

** Graphics

*** a picture

#+begin_ditaa blue.png -r -S
+---------+
| cBLU    |
|    +----+
|    |cPNK|
+----+----+
#+end_ditaa

*** another picture
#+LaTeX:\includegraphics{emacs.png}

** More interesting stuff

*** some C++ code
#+begin_LaTeX
\begin{lstlisting}[language=c]
for (int i = 1; i != 10; ++i) 
    std::cout << i << ": hello, world!"
              << std::endl;
\end{lstlisting}
#+end_LaTeX

*** and some Python...

#+begin_LaTeX
\begin{lstlisting}[language=python]
for i in range(1,10):
        print i, "hello, world!"
\end{lstlisting}
#+end_LaTeX

wanderlust tips and tricks

Earlier, I spoke of the wonderful Wanderlust e-mail client. After years of using mutt, I am a quite happy Wanderlust-user now. Now, it's few months since my conversion, time to discuss some of the customizations I did. Not all the defaults are so well-chosen (in my opinion), but fortunately, the package is very configurable.

If you are interested in Wanderlust, this entry might save you some time in figuring out such customizations and some other tricks. If you haven't done so before, I'd recommend you to read the older entry first. Also, the entry about BBDB may be useful.

Before going into the customizations, let me first answer a question I got asked a couple of times: why I am using Wanderlust and not, say, VM, gnus, Mew or even mutt or some other client?

To start with the last part, an emacs-based client fits in very well with my workflow, which is (duh) revolves around emacs. Doing my email there as well makes a lot of sense - a little return-on-investment for the time spent taming emacs and its bag of tricks.

The reason I particularly like Wanderlust, is that it works very well with mail stored in maildirs - as you may know, maildir is a one-file-per-message way of storing your mail on disk. That's great for backing up things, and sync'ing different machines.

Unlike VM and gnus, Wanderlust keeps the mail in the maildir as-is, and does not use a separate spoolfile – thus, all changes are reflected in the maildir itself, making it possible to use different clients (ie., use mutt when needed). Even more important, the wonderful tool offlineimap does two-way synchronization with IMAP-servers, and downloads everything into a maildir. So, I can download all the mail on my laptop machine, go offline and work on the messages (delete, move, reply etc.) during a flight, and when I'm back online, I can synchronize things. All this 'cloud'-stuff is nice, but I like to have my mails on my side of the intertubes.

Ok, now let's take a look at some of the customizations and tricks. All of these are little snippets to add to your ~/.wl-file.

Forwarded mails should use 'Fwd:', not 'Forward:'

I wonder why this is not the default.

(setq
  wl-forward-subject-prefix "Fwd: " )    ;; use "Fwd: " not "Forward: "

Reply-to-all should not be the default

By default, Wanderlust uses Reply-to-All; that is usually not what we (well, I) want. The code below makes Reply-to-Sender the default, with Reply-to-All behind C-u; ie. A or a will reply to sender, C-u A and C-u a reply to all.

(Note, the uppercase A is for replying with quoting the original message, while the lowercase version starts the reply with an empty message)

;; from a WL-mailinglist post by David Bremner

;; Invert behaviour of with and without argument replies.
;; just the author
(setq wl-draft-reply-without-argument-list
  '(("Reply-To" ("Reply-To") nil nil)
     ("Mail-Reply-To" ("Mail-Reply-To") nil nil)
     ("From" ("From") nil nil)))


;; bombard the world
(setq wl-draft-reply-with-argument-list
  '(("Followup-To" nil nil ("Followup-To"))
     ("Mail-Followup-To" ("Mail-Followup-To") nil ("Newsgroups"))
     ("Reply-To" ("Reply-To") ("To" "Cc" "From") ("Newsgroups"))
     ("From" ("From") ("To" "Cc") ("Newsgroups"))))

Setting up spam-handling

If you're using spamassassin for spamfiltering, you can quite easily integrate it with Wanderlust:

(require 'wl-spam)
(wl-spam-setup)
(setq elmo-spam-scheme 'sa)   ;; sa for spamassassin, see the elmo-spam-scheme
                              ;; docs for alternatives
(setq wl-spam-folder ".spam") ;; maildir to store spam

After this, you quite easily handle spam in the 'Summary' with some keybindings:

• k C : check whether spamassassin considers this message 'spam'
• k m : mark message(s) as spam (move to spam folder)
• k n : learn this message is 'ham'
• k s : learn this message is 'spam'

Note, there are some hooks for other spamfiltering solutions as well.

How to easily refile messages

I receive all my messages in only two mailboxes: one for personal mail, and one for mailing lists. If, after reading, I want to keep the message, I'll refile it to some other folder (after all, it's good to empty your mailboxes quite often. Wanderlust makes this refiling quite easy; the first way is to do it semi-automatic, i.e., let Wanderlust 'guess' the folder for you, based on the contents of the message. Then, when pressing 'o' in the summary, it will suggest this folder, and you can refile (move) the message. You can set up this 'guessing' something like this:

(setq
  ;; refile rules determine the default where mails are put

  ;; when you mark them for refiling ('o'); cfg. save-hooks in mutt
   wl-refile-rule-alist  
  '(
     ("Subject" ;; put more specific rules before more general ones.
       ("emacs"   . ".emacs")   ;; emacs-related mail

       ("running" . ".running") ;; running-related mail
       )
     
     (("To" "Cc" "Delivered-To") 
       ("myself@company.com"      . ".workmail") 
       ("myself@home.com"         . ".privatemail"))
     
     (("Precedence" "Priority")
       ("bulk\|1\|2\|list"       . ".bulkmail"))))

Explicit refiling

Semi-automatic refiling works fairly well, but you might also want to have some explicit shortcuts to move messages to specific folders. For example, to move message from your inbox to your Project X-folder, or your Project Y-folder.

(defun djcb-wl-summary-refile (&optional folder)
  "refile the current message to FOLDER; if FOLDER is nil, use the default"
  (interactive)
  (wl-summary-refile (wl-summary-message-number) folder)
  (wl-summary-next)
  (message (concat "refiled to " folder)))

(define-key wl-summary-mode-map (kbd "b x") ;; => Project X

  '(lambda()(interactive)(djcb-wl-summary-refile ".project-x"))) 
(define-key wl-summary-mode-map (kbd "b y") ;; => Project Y
  '(lambda()(interactive)(djcb-wl-summary-refile ".project-y")))

Assuming you have (Maildir) folders project-x and project-y.

Check outgoing mail

It's not uncommon to forget to add a subject or an attachment when you send a mail (or at least, when I send a mail…). However, using wl-mail-send-pre-hook we can let Wanderlust warn us when something like that happens.

;; suggested by Masaru Nomiya on the WL mailing list

(defun djcb-wl-draft-subject-check ()
  "check whether the message has a subject before sending"
  (if (and (< (length (std11-field-body "Subject")) 1)
        (null (y-or-n-p "No subject! Send current draft?")))
      (error "Abort.")))


;; note, this check could cause some false positives; anyway, better
;; safe than sorry...
(defun djcb-wl-draft-attachment-check ()
  "if attachment is mention but none included, warn the the user"
  (save-excursion
    (goto-char 0)
    (unless ;; don't we have an attachment?

      (re-search-forward "^Content-Disposition: attachment" nil t) 
     (when ;; no attachment; did we mention an attachment?
        (re-search-forward "attach" nil t)
        (unless (y-or-n-p "Possibly missing an attachment. Send current draft?")
          (error "Abort."))))))

(add-hook 'wl-mail-send-pre-hook 'djcb-wl-draft-subject-check)
(add-hook 'wl-mail-send-pre-hook 'djcb-wl-draft-attachment-check)

Ok, that's all for now… I'll get back to Wanderlust in the future; of course, feel free to add your own tricks in the comments-section.

managing e-mail addresses with bbdb

BBDB, the Insidious Big Brother Database is an Emacs addressbook application that works particularly well with e-mail. It's one of the classic emacs packages, written in 1991 by Jamie Zawinski.

Personally, I do not use BBDB as a general address book. Instead, I use it to harvest the e-mail addresses of the people that send me mail, so that the next time I'd like to send e-mail, I can auto-complete the names / e-mail addresses. If you're not using some emacs-based email client, BBDB might not be that useful in practice.

Note that other people are using BBDB for much more, see the Emacswiki-entry for some examples of that. Here, I just give some basics to get you started; please refer to the fine manual for all the details.

configuration

So, after you've installed bbdb (just follow the instructions; alternatively Ubuntu/Debian users can simply install the bbdb package), we can add the following to .emacs to set it up:

(setq bbdb-file "~/.emacs.d/bbdb")           ;; keep ~/ clean; set before loading
(require 'bbdb) 
(bbdb-initialize)
(setq 
    bbdb-offer-save 1                        ;; 1 means save-without-asking

    
    bbdb-use-pop-up t                        ;; allow popups for addresses
    bbdb-electric-p t                        ;; be disposable with SPC
    bbdb-popup-target-lines  1               ;; very small
    
    bbdb-dwim-net-address-allow-redundancy t ;; always use full name
    bbdb-quiet-about-name-mismatches 2       ;; show name-mismatches 2 secs

    bbdb-always-add-address t                ;; add new addresses to existing...
                                             ;; ...contacts automatically
    bbdb-canonicalize-redundant-nets-p t     ;; x@foo.bar.cx => x@bar.cx

    bbdb-completion-type nil                 ;; complete on anything

    bbdb-complete-name-allow-cycling t       ;; cycle through matches
                                             ;; this only works partially

    bbbd-message-caching-enabled t           ;; be fast
    bbdb-use-alternate-names t               ;; use AKA


    bbdb-elided-display t                    ;; single-line addresses

    ;; auto-create addresses from mail
    bbdb/mail-auto-create-p 'bbdb-ignore-some-messages-hook   
    bbdb-ignore-some-messages-alist ;; don't ask about fake addresses
    ;; NOTE: there can be only one entry per header (such as To, From)
    ;; http://flex.ee.uec.ac.jp/texi/bbdb/bbdb_11.html

    '(( "From" . "no.?reply\\|DAEMON\\|daemon\\|facebookmail\\|twitter")))
)

This will set up BBDB for you. I have commented the various settings; you can of course get more information for each of them by putting your cursor on them (in emacs) and issuing C-h v.

integration with e-mail clients

Another important part is the integration with e-mail - which is why I am using BBDB in the first place.

As I mentioned before, I am using the wonderful Wanderlust e-mail client for emacs, and you can easily integrate it with BBDB by putting the following in your .wl-file:

(require 'bbdb-wl)
(bbdb-wl-setup)

;; i don't want to store addresses from my mailing folders
(setq 
  bbdb-wl-folder-regexp    ;; get addresses only from these folders
  "^\.inbox$\\|^.sent")    ;; 


(define-key wl-draft-mode-map (kbd "<C-tab>") 'bbdb-complete-name)

For gnus, you'd use something like:

(add-hook 'gnus-startup-hook 'bbdb-insinuate-gnus)

(I am not using gnus myself, feel free to add you setup in the comments)

The BBDB-manual has the details for some other mail clients as well.

Use

So, we have everything set up now – but how does it work? Well, whenever you read e-mails, BBDB stores the various e-mail addresses. Whenever you write an e-mail, you can complete the names with M-x bbdb-complete-name, by default bound to M-TAB. This keybinding conflicts with many window managers, which already use M-TAB (Alt-TAB) for window switching. So, it's useful to rebind it to something else, for example C-TAB (I already did that for Wanderlust, in the example above).

I don't use BBDB too much directly, but you can manipulate the address; first display one with M-x bbdb-display-address, they you can edit a field by pressing 'e', 'd' for deleting the field or record, C-o for adding a new field and so on – see the whole list.