replace-regexp and numbering lines

I saw the Got Emacs? posting showing off the new emacs-24
rectangle-numbers-lines command, to number a bunch of lines in buffer,
i.e..:

foo
bar
cuux

becomes:

1 foo
2 bar
3 cuux

Very cool! An alternative is to use cua-mode, mark the column for the
numbers with cua-set-rectangle-mark (C-RET), and then use M-x cua-sequence-rectangle (which takes you throught the steps, and has a lot of
flexibility.

But let's look at yet another way: using replace-regexp. If we select (mark)
the list once more, we can do M-x replace-regexp RET ^ RET \#. RET Note that
the # is a special meta-character that represents the number of replacements already made. This has the somewhat clumsy side-effect that your
list be numbered, starting at 0 rather than 1, so you should add a
dummy-element at the beginning. Clearly, replace-regexp is inferior for
simply adding some line numbers – however, it has the flexibility to do some
smarter things.

Smarter things? Yes! replace-regexp allows you to use arbitrary
Lisp-expressions in the replace strings. So, let's suppose that we want to use
letters instead of numbers for our lines. Easy – again, select (mark) your
lines, M-x replace-regexp RET ^ RET \,(format "%c. " (+ ?a \#)) RET and we get:

a. foo
b. bar
c. cuux

Admittedly, not the most world-shattering thing, but it does show the powers
hidden in something as common as replace-regexp.

who holds this value?

Something from the category of useful things hiding in emacs… Suppose you
are looking for the variable that holds a certain value. How to find it?

Easy: M-x apropos-value

So, for example, finding all variables that hold your e-mail address:

M-x apropos-value RET me@example.com RET

and you'll get all the matches in the *Apropos*-buffer. HT: Stephen
Eglen.

Also check the various other M-x apropos-... commands, they all help you
find useful information if you can remember a word. Except for… M-x apropos-zippy… eh?

euro 2012 games in your org-mode agenda

Things have been rather quiet at emacs-fu - reason for this is that most of my
emacs hacking time has been spent on mu4e, the emacs e-mail client I
wrote. It's been shaping up pretty nicely, I should probably write some
emacs-fu posts about it :)

Another interesting pastime (esp. in Europe) is football/soccer, in particular
the Euro2012 games; long-time readers will remember the schedule for world cup games; I made a new one for Euro2012: https://github.com/djcb/org-euro2012.

In order to have the games show up in your agenda, make sure the file is in
your org-agenda-files. If needed, you could add it with something like this in
your org-mode settings (change the directory path to wherever you have put
euro2012.org):

(add-to-list 'org-agenda-files "~/org/euro2012.org")

One small issue with the schedule is that it uses the central-european summer
time (UTC+2), and there is no automatic way to adjust times for the local time
zone. As a work-around, Juan Pechiar provided the following function which makes
it easy to update all org-timestamps in a file:

(defun update-org-hours (n)
  "Change all org-mode timestamps in the current buffer by N hours."
  (interactive "nAdd hours: ")
  (save-excursion
    (goto-char (point-min))
    (while (re-search-forward "[[<]" nil t)
      (when (org-at-timestamp-p t)
        (org-timestamp-change n 'hour)))))

Evaluate this function. After that, you can go to the file with the schedule,
and give an M-x update-org-hours, provide the offset for your timezone, compared to
UTC+2.

Let the games begin!

social networking with bitlbee and erc

Instant messaging (IM) is one of the great time sinks of our age. Emacs-users,
social butterflies as we are, of course want to take part in that --
preferrably from the comfort of our own environment.

There are various ways to use services like MS Live Messenger, Facebook Chat, GTalk, Yahoo etc. from within emacs – the one I use is called
BitlBee. BitlBee is a program that presents all the various forms of IM as
IRC-channels. In other words, while BitlBee knows all the details about
communicating with these networks, all you need is an IRC-client to connect
to BitlBee. This IRC-client does not have to be Emacs-based - any client can
be used - but I am using ERC. Note, the below assumes you are somewhat
familiar with it.

So, let's see how we can set up BitlBee on our system; there are public
BitlBee-servers available online, but in the case of IM, I wouldn't
necessarily want to trust them with my account data… so I'm using my own.

Setting up Bitlbee

So, how can we set this up? First, install BitlBee – many distributions have
ready-made packages, otherwise you can build from source. In the examples
below, I am assuming you are using Bitlbee version 3 or higher; if you use
a different version, the details will vary a bit.

You can either run Bitlbee as a system-wide daemon, or just use it on your
own. I am doing the former (for the latter, bitlbee.el is useful).

To connect ERC to the Bitlbee daemon, you can use something like the
following:

(defun i-wanna-be-social ()
  "Connect to IM networks using bitlbee."
  (interactive)
  (erc :server "localhost" :port 6667 :nick "user"))

I'm sure you can come up with a better nick than user… Anyhow, with this
function in your ~/.emacs, we can connect to bitlbee with:

M-x i-wanna-be-social RET

This should connect us to BitlBee; when all goes well, this will look
something like this:

*** You have joined channel &bitlbee
*** mindcrime has changed mode for &bitlbee to +t
*** Users on &bitlbee: @user @root
*** Topic for &bitlbee: Welcome to the control channel. Type help for help
    information.
<root> Welcome to the BitlBee gateway!
<root>
<root> If you've never used BitlBee before, please do read the help
  information using the help command. Lots of FAQs are answered there.
<root> If you already have an account on this server, just use the identify
  command to identify yourself.
<root> The nick is (probably) not registered
*** &bitlbee modes: +t
<ERC>

Now, this first time, you will need to register yourself (this is only
needed once); use the same nick (user in the example) that you used before:

<user> register user secretpassword
<root> Account successfully created

We're registered! This means, that bitlbee knows about you, and will save your
settings.

Re-entering bitlbee

Just to complete the bitlbee-connecting part: the next time you want to use
bitlbee, use i-wanna-be-social as before. However, now you need to
identify yourself (rather than register):

<user> identify user secretpassword
<root> Password accepted, settings and accounts loaded

This can be automated by adding something like the following to your config:

(defun bitlbee-identify ()
  (when (and (string= "localhost" erc-session-server)
          (string= "&bitlbee" (buffer-name)))
    (erc-message "PRIVMSG" (format "%s identify user secretpassword"
                             (erc-default-target)
                             djcb-bitlbee-password))))

(add-hook 'erc-join-hook 'bitlbee-identify)

Modify user and secretpassword as desired. If you don't want write out
your passwords in your emacs config files, take a look at keeping your secrets secret.

Adding accounts

Now, let's add some IM-accounts (just some examples here; also see Bitlbee Quickstart. Note, add any point during this, you can see your accounts with
the command:

<user> account list

and using the numbers (or the accounts 'tag') you can switch an account on
(and off):

<user> account 0 on

There are many other commands – use help command the consult the built-in
documentation.

Connecting to IM networks

To connect to IM networks, you have to add the accounts to BitlBee. It will
save them, so you only need to do that once. Let's do it - in each case,
replace user and password with whatever you use for those.

You can see your combined logged-in buddy list using M-x erc-channel-names
(or C-c C-n). Or use the blist command (see help blist).

After adding an account, it's a good idea to issue the save command, to
ensure that bitlbee saves it.

Jabber

<user> account add jabber foobar@jabber.org mypassword
<root> Account successfully added with tag jabber
<user> account jabber on
<root> jabber - Logging in: Connecting
<root> jabber - Logging in: Connected to server, logging in
<root> jabber - Logging in: Converting stream to TLS
<root> jabber - Logging in: Connected to server, logging in
<root> jabber - Logging in: Authentication finished
<root> jabber - Logging in: Authenticated, requesting buddy list
<root> jabber - Logging in: Logged in

(and of course, you can use other servers beside jabber.org)

GoogleTalk

GoogleTalk (gtalk) is implemented using XMPP (jabber), and it's
recommended to use oauth for authentication. Note, the foobar below is
just a placeholder (for a password); bitlbee wants us to put something
there, but since we'll be using oauth, it's not actually used.

<user> account add jabber myaccount@gmail.com foobar
<root> Account successfully added with tag gtalk
<user> account gtalk set oauth on
<root> oauth = `on'
<user> account gtalk set nick_source full_name
<root> nick_source = `full_name'
<user> account gtalk on
<root> gtalk - Logging in: Starting OAuth authentication

Now, a second window will open with a URL:

<jabber_oauth> Open this URL in your browser to authenticate:
https://accounts.google.com/o/oauth2/auth?scope=https://www.googleapis.\
com/auth/googletalk&response_type=code&redirect_uri=urn:ietf:wg:oauth:2.0:oob&client_i\
d=78312399893489.apps.googleusercontent.com

<jabber_oauth> Respond to this message with the returned authorization
token.

Follow this URL in your browser, and it will take you to some Google page
for authentication. When that is completed, you will receive some string
cookie, which you paste back into the newly opened window.

<user> 4/sIns904fdlkP5nudjCF4mBHF7Go_-E0g8
*** jabber_oauth is AWAY: Offline

Et voilà! We're connected to Gtalk (don't worry about the Offline-warning).

Facebook

Apart from being a social website, Facebook can also be used for IM. You can
do this through the website, or you can use its jabber interface. It works
very similar to gtalk; only important thing is that you get yourself a
Facebook username:

<user> account add jabber myusername0@chat.facebook.com
<root> Account successfully added with tag fb
<root> You can now use the /OPER command to enter the password
<root> Alternatively, enable OAuth if the account supports it: account
  fb set oauth on
<user> account fb set oauth on
<root> oauth = `on'
<user> account gtalk set nick_source full_name
<root> nick_source = `full_name'
<user> account fb on
<root> fb - Logging in: Starting OAuth authentication

Then, go through the oath-authentication steps (see the discussion about
adding Gtalk accounts above).

Once authenticated, you'll get something like this:

<root> fb - Logging in: Requesting OAuth access token
<root> fb - Logging in: Connecting
<root> fb - Logging in: Connected to server, logging in
<root> fb - Logging in: Converting stream to TLS
<root> fb - Logging in: Connected to server, logging in
<root> fb - Logging in: Authentication finished
<root> fb - Logging in: Server claims your JID is
  `-748234518@chat.facebook.com' instead of
  `myusername0@chat.facebook.com'. This mismatch may cause problems with
  groupchats and possibly other things.
<root> fb - Logging in: Authenticated, requesting buddy list
<root> fb - Logging in: Logged in

It's to now act upon the warning, so, we log out, change the user name and
long back in:

<user> account fb off
<root> fb - Signing off..
<user> account fb set username -748234518@chat.facebook.com
<root> username = `-748234518@chat.facebook.com'
<user> account fb on

MSN / Live Messenger

MSN uses its own protocol (although apparently they're also supporting XMPP
("jabber") now). Suppose you have an account there, user
partygirl89@hotmail.com with password iamcute:

<user> account add msn partygirl89@hotmail.com iamcute
<root> Account successfully added
<user> account msn on
<root> msn - Logging in: Connecting
<root> msn - Logging in: Connected to server, waiting for reply
<root> msn - Logging in: Transferring to other server
<root> msn - Logging in: Connected to server, waiting for reply
<root> msn - Logging in: Authenticated, getting buddy list
<root> msn - Login error: Error reported by MSN server: Invalid
       (non-existent) handle                                      [12:17]
<root> msn - Logging in: Logged in

The 'Error reported' does not seem to matter.

Other accounts

It's similarly easy to setup Twitter-accounts and Identi.ca-accounts; I've
stopped using those though, as it turned out to be a little too easy for
some typing in the wrong window to end op as a tweet… The risk is less
with twittering-mode and identica-mode.

For ICQ/Yahoo/AIM see below – replace the username/password with your
own.

• ICQ
  
  
  
  
  

  <user> account add oscar ICQ-ID PASSWORD login.icq.com
  <root> ...
  

  
  
  
  

• AIM
  
  
  
  
  

  <user> account add oscar AIM-NICK PASSWORD login.aol.oscar.com
  <root> ...
  

  
  
  
  

• Yahoo!
  
  
  
  
  

  <user> account add yahoo YAHOO-NICK PASSWORD
  <root> ...
  

  
  
  
  

  
  And I'm not even talking about combining bitlbee and Skype – yes, that is
  possible, too.
  

  
  

Chatting

Now, chatting is easy, following the normal ERC conventions (and
settings). When people talk to you, a window opens (or a frame – see
erc-auto-query. And you can initiate conversations with people by using
/msg nick, with nick of course being the nickname of the person you want
to talk to.

ERC/Bitlbee also work together nicely with Sauron, the emacs event tracker.

Have fun! I have only scratched the surface here - you now have the full
arsenal of Elisp and ERC power available for your chatting.

special characters

Special characters

Living in a post-ASCII world offers great opportunities, but brings some
problems, too. After all, it's nice to be able to write Ångström or
Καλημέρα or ☺☎☯, but it's not necessarily easy to enter those
characters.

input methods

So - what to do? First, you can set the input-method, as explained in the emacs manual. This is the best solution if you're writing a non-Latin
language – Russian, Thai, Japanese, …

If you only occasionally need some accented character, input methods like
latin-postfix (e" -> ë), latin-prefix ("e -> ë) or TeX (\"e -> ë) are
useful. They also tend to annoy me a bit, as they often assume I need an
accented character, when all I want is to put a word in quotation marks…

compose key

Another method is to use a special compose key; for example, under Gnome 3
it's in the the Region and Language applet, under Options..., in Gnome 2
it's in the Keyboard applet in Layouts/Options…. This works for all
programs, not just emacs (see this Ubuntu help page for some details). I've
set my Compose-key to Right-Alt, so Right-Alt "e -> ë.

Using the compose key works pretty well for me; setting the input method may
be more convenient when you need to write a lot of accented characters.

Now, his may be good and well for the accented characters and other variants
of Latin characters, such as the German Ess-Zet ligature "ß" (note, you can
get that character with latin-prefix "s -> ß, latin-postfix s" -> ß or
<compose-key> ss -> ß). But what about Greek characters? Mathematical
symbols? Smileys?

ucs-insert

One way to add characters like α, ∞ or ☺ is to use ucs-insert, by
default bound to C-x 8 RET. If you know the official Unicode name for a
character, you can find it there; note that there's auto-completion and you
can use * wild-cards. For the mentioned characters, that would be GREEK SMALL LETTER ALPHA, INFINITY and WHITE SMILING FACE.

You can also use the Unicode code points; so C-x 8 RET 03b1 RET will insert
α as well, since its code point is U+03B1. In case you don't know the code
points of Unicode characters, a tool like the Character Map (gucharmap) in
Gnome may be useful.

abbrev

Since ucs-insert may not be convenient in all cases, you may want to add
shortcuts for oft-used special characters to you abbrev table. See the
entry on Abbrevs in the emacs manual. I usually edit the entries by hand with
M-x edit-abbrevs, and I have entries like:

(text-mode-abbrev-table)
"Delta0"       0    "Δ"
"^2"           0    "²"
"^3"           0    "³"
"almost0"      0    "≈"
"alpha0"       0    "α"
"any0"         0    "∀"
"beta0"        0    "β"
"c0"           0    "©"
"deg0"         0    "℃"
"delta0"       0    "δ"
"elm0"         0    "∈"
"epsilon0"     0    "ε"
"eta0"         0    "η"
"heart0"       0    "♥"
"inf0"         0    "∞"
"int0"         0    "∫"
"notis0"       0    "≠"

Now, alpha0 will be auto-replaced with α. I'm using the 0 suffix for
most entries so I can easily remember them, without making it hard to use
alpha as a normal word. Note, abbrevs are a bit picky when it comes to
the characters in the shortcut – for example, setting != -> ≠ won't
work.

inheriting abbrevs from other modes

If you have set up a nice set of abbreviations for text-mode, you may want
to use them in other modes as well; you can accomplish this by including the
text-mode abbreviations into the table for the current one, for example in
your ERC setup:

;; inherit abbrevs from text-mode
(abbrev-table-put erc-mode-abbrev-table :parents (list text-mode-abbrev-table))

update

Regular emacs-fu programming will resume shortly, but for now I'll provide a
brief update on some of my projects.

• Recently, I discussed sauron, and event-tracking tool for emacs. I added
  some new features, fixed some bugs, and got some contributions (yay!)
  
  
  
  
  • tweak/improve priority handling
    
  
  
  • add a backend for the emacs-24 notification system
    
  
  
  • add settings to make the sauron frame 'sticky', and to hide the mode-line
    
  
  
  • enable dbus-message source outside your session; useful for cron/procmail
    etc.
    
  
  
  • display events in a tabular fashion
    
  
  
  • add support for John Wiegley's event.el
    
  
  
  • much improved documentation
    
  
  
  • other things…
    
    
  
  
  
  
  

  Sauron version 0.2 is available through Marmalade (see Package Management Revisited)
  

  
  


• I released version 0.9.8 of mu (e-mail searcher/indexer, previously
  discussed in Searching e-mails with Wanderlust and mu). Now, for emacs-users
  I've added mu4e (manual), a new & experimental e-mail client. It won't be
  big and professional like gnus, but it's fun to hack on, and I've been
  using it for a few months.
  

sauron: keeping an eye on what's going on

I'm a fairly busy person, and need to keep track of a lot of things. That
includes following a bunch of internal IRC channels, attending meetings, meeting
deadlines and so on. But I don't want to stare at my org-mode calendar, or
flip through ERC buffers all the time.

Instead, I'd like to have one little emacs frame (window) that gathers these
('events'), and transfers me to wherever the event came from when I click it - some
IRC-channel in ERC, my org-calendar etc. and other inputs. Note, using
Bitlbee, you can include Facebook-contacts, GoogleTalk-buddies and
Twitter-tweets, … in ERC - so, you can track just about anything.

In addition, with so many inputs, I'd also like the possibility to filter out unwanted
events, and generate various light/sound effects and fireworks, proportional
to the priority of the event.

For all this, I wrote a little emacs-tool called Sauron that does just
that. M-x sauron-start pops up a frame that receives events, and M-x sauron-stop hides it and stops listening. It works with ERC, org, and
listens for D-Bus messages; so it's pretty easy to get events from all over
the place.

It's a bit of a balancing act to get all the important information while not
being swamped in noise, but Sauron allows you to fine-tune it to whatever
works the best for you. I've tried to have sane defaults though, so things
should mostly work without too much configuration - but if you need the power,
it's there. I also added some convenience functions to make it easy to get
sounds and other special effects.

So - it's brand new, it is of seems-to-work-for-me-quality, and I'd like to
invite others to try it out, hack it, give feedback, add new back-ends and so
on – what better Christmas present to ask for!

There's documentation, examples etc. to be found in Sauron's github repository.

system administration with emacs

When performing system administration tasks, one often needs to edit files
owned by root.

For both security and safety reasons, it's a good idea to do as little as
possible as root (or with root privileges). For that reason, you probably
don't want to run Emacs as 'root', because it's simply too powerful. I often
see people use vi (usually, vim) instead – but since it allows you to do
just about anything as well (like running shell commands), that's not much of
an improvement.

Now, a while back we discussed editing files owned by root with tramp – you
can use emacs with your normal user-account, and use sudo to write the
root-owned file. That makes it much harder to screw things up.

Another reason people use vi for little editing jobs is because its startup
time is significantly shorter than the startup time for a new emacs
instance. For that, however, we have emacs daemon.

Combining tramp and emacs daemon and a shell function:

# edit file with root privs
function E() {
         emacsclient -c -a emacs "/sudo:root@localhost:$1"
}               

Now, we can very quickly edit any file owned by root using 'E' --

$ E /etc/hosts

So, if you prefer emacs, there's little reason to use vi, even for editing
system files – although I have to admit that it takes time to evict 'sudo vi
<system file>' from my muscle memory.

Update reader Yi Wang mentions that, in fact, we can make this a bit more
general using sudoedit; so, instead of using Tramp, we can use:

# edit file with root privs
alias E="SUDO_EDITOR=\"emacsclient -c -a emacs\" sudoedit"   

This works also without absolute paths.

quick note-taking with deft and org-mode

Emacs must be gathering a lot of enthusiasts lately; there's hardly a week
where I don't discover some new gem. Recently, I discovered deft. And
apparently, I wasn't the only one.

So what is it deft good for? Well, often I want to jot down some quick thing
during a meeting or a telephone-call. Of course, I don't want to think about
file names or anything else distracting me from my task, just get me that note
already! In addition, at some later time, I want to be able to quickly search
through the notes I made.

For MacOS, there's a program called Notational Velocity which does this. But
really - it sounds like a typical task for emacs - wouldn't it be nice to have
an emacs package that does roughly the same?

And that is what deft does - enable you to quickly write notes, and
retrieving them later. The author has an excellent introduction on his
website, so my job is very easy :) deft is not part of org-mode, but they
can work together seamlessly. Here's my set-up:

;; http://jblevins.org/projects/deft/
(when (require 'deft nil 'noerror) 
   (setq
      deft-extension "org"
      deft-directory "~/Org/deft/"
      deft-text-mode 'org-mode)
   (global-set-key (kbd "<f9>") 'deft))

This blob goes in my .emacs. Note, the first line ensures that emacs starts
without errors, even when I run on a system without deft. Apart from that, I
make deft use org files for note taking, which makes it all very familiar.

All notes are saved ~/Org/deft - you can set it to something else of
course. A Dropbox-folder seems to be a popular choice for synchronizing
between machines.

Finally, the last line binds F9 to deft-mode. So, when I need a quick
note, I can type F9 C-c C-n and start writing.

finding just about anything

Buffer-switching is one of those things I do all the time in Emacs. And it
should be quick and efficient, or it will break my 'flow'. There are many
ways to customize the buffer switching experience, and we already discussed
quite a few of those here: using Ctrl-Tab, iswitchb/ido, ibuffer, the lusty explorer and others.

Some of those packages - ido and lusty-explorer - do not solely focus on
buffer-switching - they also let you open files using the same user
interface. But why stop at files and buffers - wouldn't it be nice if we
could quickly find just about anything quickly?

Indeed that would be nice - and there's a way to do just that - using the
aptly named anything package. I was always a bit put off by this package due
to the screenshots (see link), but once I got over that, I've become a very
happy user.

Anyhow, what can anything find? I mentioned buffers and files, but it can
also find bookmarks, recently used files, any file on your system (using
locate), man-pages, info-pages, emacs-function/variables,
FIXME-comments, org-headlines, bbdb-contacts, google-suggests… and a
million other things. It can probably find your car keys, too.

Installation is pretty straightforward, using the git-repository:

git clone git://repo.or.cz/anything-config.git

Then, go into the just-cloned directory and execute make. After that, add
to your .emacs (or ~/.emacs.d/init.el):

;; path-to-anything is the path which has the 'anything' we just cloned
(add-to-list 'load-path "path-to-anything")
(require 'anything-config)

This will add a menu with various anything-commands, and a bunch of
key-bindings, starting with F5. Play around a bit with it, it's nice. The
results are shown in a little temporary buffer, and pressing Tab will let
you do (search-type dependent) actions on the matches - for example
ediff two buffers.

Of course, the real fun starts when we super-charge some of the normal
emacs functions with anything-based ones. Let's look at buffer
switching. Let's create an anything-based version, and assign it to C-x b, the good-old switch-to-buffer.

The thing to consider is that while anything can find just about
anything, you (well, I) usually only want to search for a certain set of
things; when I want to switch to another buffer, I don't want to match
man-pages. Luckily, anything allows for making nifty function which use
certain subsets of the search sources. So for buffer switching, I have:

(global-set-key (kbd "C-x b")
  (lambda() (interactive)
    (anything
     :prompt "Switch to: "
     :candidate-number-limit 10                 ;; up to 10 of each 
     :sources
     '( anything-c-source-buffers               ;; buffers 
        anything-c-source-recentf               ;; recent files 
        anything-c-source-bookmarks             ;; bookmarks
        anything-c-source-files-in-current-dir+ ;; current dir
        anything-c-source-locate))))            ;; use 'locate'

This will search in buffers, then in my recent-files, then in my bookmarks,
the files in the current directory, and finally check with the locate
tool. That last one is pretty neat, and finally gives me something back for
the countless times I've wondered why the hard disk is grinding – indeed,
it was locate, updating its database.

Then, I've defined another binding for searching general documentation on
my system; I've put it under C-c I. This looks look something like the
following:

(global-set-key (kbd "C-c I")  ;; i -> info
  (lambda () (interactive)
    (anything
      :prompt "Info about: "
      :candidate-number-limit 3
      :sources
      '( anything-c-source-info-libc             ;; glibc docs
         anything-c-source-man-pages             ;; man pages
         anything-c-source-info-emacs))))        ;; emacs 

These are sources I query quite regularly; there are many more to be
found - for most packages with info-pages there's a corresponding
anything-c-source-info-...; there's a list in anything-config.el.

Now, those are my general documentation sources; in specific modes, I
have specialized information sources; for example, for elisp-mode:

(add-hook 'emacs-lisp-mode-hook
  (lambda()
  ;; other stuff...
  ;; ...
  ;; put useful info under C-c i
    (local-set-key (kbd "C-c i")
      (lambda() (interactive)
        (anything
          :prompt "Info about: "
          :candidate-number-limit 5
          :sources
          '( anything-c-source-emacs-functions
             anything-c-source-emacs-variables
             anything-c-source-info-elisp
             anything-c-source-emacs-commands
             anything-c-source-emacs-source-defun
             anything-c-source-emacs-lisp-expectations
             anything-c-source-emacs-lisp-toplevels
             anything-c-source-emacs-functions-with-abbrevs
             anything-c-source-info-emacs))))

This post just scratches the surface of what is possible – so go and
experiment :) One interesting thing is to add your own sources; I played a
bit with that already,

There are many things in anything I did not cover yet. First, there are
many more sources to search - and it's pretty easy to write your own – see
the EmacsWiki-page.

customizing the mode-line

The mode-line is the emacs 'status bar', the bar just above the minibuffer
that shows various pieces of information, such as the buffer name, the major
mode, maybe the current line number, some indicators for active minor modes,
and so on. As I'm looking at it, it starts with 1<U:**- (which is:
input-method: latin-1-alt-postfix, buffer-coding-system: utf8-unix,
line-ending: unix-style, buffer is writable and buffer is modified – the
tooltips help).


As with just about anything in emacs, the mode-line can be customized just
the way you like. I give some example below, not because I think it is
necessarily the best way, but just to give you a bit of an example to
start with when making your own best-mode-line-ever.


I'm not going through all the details of the example, but let me highlight a
few things that make it a bit easier to understand.


First of all, the mode-line can be customized by setting the variable
mode-line-format; this variable becomes buffer-local automatically when
changed, so if you want to set it for all buffers, you'll need to use
setq-default in your .emacs (or equivalent). The format is quite similar
to the one for frame-title-format, which we discussed in setting the frame title a while back.


mode-line-format is a list of items which are evaluated, and put
together as a string which then ends up as the mode-line contents. These
properties can be any string. The following types of items can be used:

• First, normal strings are just shown as-is;
  
  


• Then, there are some special format parameters which will be replaced with
  their value in the mode-line, from the Emacs-documentation:
  

  %b -- print buffer name.      %f -- print visited file name.
  %F -- print frame name.
  %* -- print %, * or hyphen.   %+ -- print *, % or hyphen.
        %& is like %*, but ignore read-only-ness.
        % means buffer is read-only and * means it is modified.
        For a modified read-only buffer, %* gives % and %+ gives *.
  %s -- print process status.   %l -- print the current line number.
  %c -- print the current column number (this makes editing slower).
        To make the column number update correctly in all cases,
        `column-number-mode' must be non-nil.
  %i -- print the size of the buffer.
  %I -- like %i, but use k, M, G, etc., to abbreviate.
  %p -- print percent of buffer above top of window, or Top, Bot or All.
  %P -- print percent of buffer above bottom of window, perhaps plus Top,
        or print Bottom or All.
  %n -- print Narrow if appropriate.
  %t -- visited file is text or binary (if OS supports this distinction).
  %z -- print mnemonics of keyboard, terminal, and buffer coding systems.
  %Z -- like %z, but including the end-of-line format.
  %e -- print error message about full memory.
  %@ -- print @ or hyphen.  @ means that default-directory is on a
        remote machine.
  %[ -- print one [ for each recursive editing level.  %] similar.
  %% -- print %.   %- -- print infinitely many dashes.
Decimal digits after the % specify field width to which to pad.

• Forms of the type (:eval ...) are evaluated each time the mode-line is
  drawn (just like the '%'-parameters) ; so, if you have a value that
  changes of the course your emacs session, you should use (:eval ...).
  
  For example, for your emacs-uptime you could use (:eval (emacs-uptime "%hh")); while the emacs-PID does not change, so simply you could simply
  use (format "PID:%d").
  
  
  
  The format parameter mentioned above are of evaluated each time as
  well. Note that you have to be a bit careful with evaluations - don't do
  too heavy operations there, and be careful the updates don't recurse.
  
  
  
  


• There are many others which I won't go into now - please check the Elisp
  reference. It's a rather baroque format…
  

Now, let's put this all together in an example (tested with emacs 23 and
24). As I said, this is for demonstration purposes only; but hopefully it
gives you some inspiration. A lot of the 'magic' (colors, tooltips, faces)
happens with the propertize function; again, the Elisp documentation can
tell you a lot more about that. I'm (ab)using the various font-lock-faces to
have colors that blend in nicely with your current theme.


And it has a limitation still, namely that it does not react to mouse clicks;
how to that, I will discuss in some future article.

;; use setq-default to set it for /all/ modes
(setq mode-line-format
  (list
    ;; the buffer name; the file name as a tool tip
    '(:eval (propertize "%b " 'face 'font-lock-keyword-face
        'help-echo (buffer-file-name)))

    ;; line and column
    "(" ;; '%02' to set to 2 chars at least; prevents flickering
      (propertize "%02l" 'face 'font-lock-type-face) ","
      (propertize "%02c" 'face 'font-lock-type-face) 
    ") "

    ;; relative position, size of file
    "["
    (propertize "%p" 'face 'font-lock-constant-face) ;; % above top
    "/"
    (propertize "%I" 'face 'font-lock-constant-face) ;; size
    "] "

    ;; the current major mode for the buffer.
    "["

    '(:eval (propertize "%m" 'face 'font-lock-string-face
              'help-echo buffer-file-coding-system))
    "] "


    "[" ;; insert vs overwrite mode, input-method in a tooltip
    '(:eval (propertize (if overwrite-mode "Ovr" "Ins")
              'face 'font-lock-preprocessor-face
              'help-echo (concat "Buffer is in "
                           (if overwrite-mode "overwrite" "insert") " mode")))

    ;; was this buffer modified since the last save?
    '(:eval (when (buffer-modified-p)
              (concat ","  (propertize "Mod"
                             'face 'font-lock-warning-face
                             'help-echo "Buffer has been modified"))))

    ;; is this buffer read-only?
    '(:eval (when buffer-read-only
              (concat ","  (propertize "RO"
                             'face 'font-lock-type-face
                             'help-echo "Buffer is read-only"))))  
    "] "

    ;; add the time, with the date and the emacs uptime in the tooltip
    '(:eval (propertize (format-time-string "%H:%M")
              'help-echo
              (concat (format-time-string "%c; ")
                      (emacs-uptime "Uptime:%hh"))))
    " --"
    ;; i don't want to see minor-modes; but if you want, uncomment this:
    ;; minor-mode-alist  ;; list of minor modes
    "%-" ;; fill with '-'
    ))

Have fun playing with this!

porting the zenburn theme to emacs 24

Just a small note: I already mentioned the zenburn color theme a couple of
times. I have now ported the full (big) set of customizations to the emacs-24 format
– find it at github; so if you run emacs 24 (the development version) and
enjoy zenburn like me, you can give it try. Suggestions, additions are
welcome.

Note, there seems to be a limitation with the :inherit-attribute for themes
– in practice it means that some aspects of the theme may not work if a
package sets the face before the theme does. Therefore, best to load the theme
early from your .emacs or init.el; or alternatively visit the theme file
(zenburn-theme.el in this case) and evaluate the buffer.

nice-looking pdfs with org-mode and xetex

I've discussed the wonderful org-mode here a number of times already. It has
become a pretty important part of my overall workflow. One thing I am using
org-mode for, is to produce all kinds of PDF-documents that I can share with
other people.

org-mode & LaTeX

In the past, I often used straight LaTeX for such things; I wrote my thesis
with it, but also many other documents. There are many things I like about
LaTeX, one of them being that I can use emacs for writing. Still, there are
also a few things I do not particularly like. First, I think LaTeX is quite
heavy with formatting directives, which hinder my writing flow (e.g., when I
want to include an image, a table or a source code snippet). Another thing is
that I find the default LaTeX styles a bit boring. Nothing wrong with it,
but there just too many documents with the exact same lay-out.

Now, back to org-mode. One way to use org-mode is as a friendly way to
generate LaTeX (and, consequently, PDFs). This is a big improvement! Much
more than LaTeX itself, org-mode allows to focus on the contents of the
document, rather than instructing LaTeX what to do. This comes at the price
of small bit of flexibility, but, if needed org-mode allows you include
straight LaTeX when needed – so while keeping easy things easy, hard things
are still possible. The latter does require a bit of experience with LaTeX a
though.

setting up XeTeX

Now, for the second issue, the way documents look, there are other
solutions, and they live on the LaTeX side of things. I'm sure many have seen
The Beauty of LaTeX. Using the XeTeX implementation of LaTeX and the
fontspec package, you can create LaTeX documents with a bit 'refreshed'
look.

So, the steps to get this working with org-mode:

• install the texlive-xetex packages on Ubuntu and Debian (this installs a
  huge set of packages)
  


• install the SIL fonts (I'm using ttf-sil-gentium and ttf-sil-charis, but
  there are more)
  


• I'm also using DejaVu Mono (ttf-dejavu)
  

teaching org-mode about the new XeTeX stuff

We now need to define some LaTeX document class for org-mode that uses
XeTeX and some of these new fonts. Let's call the document class
djcb-org-article (as I often use the djcb- prefix for my own stuff), it
could be something like the following (add to your org-setup – e.g., in
your .emacs, make sure there is a (require 'org) before this:

;; 'djcb-org-article' for export org documents to the LaTex 'article', using
;; XeTeX and some fancy fonts; requires XeTeX (see org-latex-to-pdf-process)
(add-to-list 'org-export-latex-classes
  '("djcb-org-article"
"\\documentclass[11pt,a4paper]{article}
\\usepackage[T1]{fontenc}
\\usepackage{fontspec}
\\usepackage{graphicx} 
\\defaultfontfeatures{Mapping=tex-text}
\\setromanfont{Gentium}
\\setromanfont [BoldFont={Gentium Basic Bold},
                ItalicFont={Gentium Basic Italic}]{Gentium Basic}
\\setsansfont{Charis SIL}
\\setmonofont[Scale=0.8]{DejaVu Sans Mono}
\\usepackage{geometry}
\\geometry{a4paper, textwidth=6.5in, textheight=10in,
            marginparsep=7pt, marginparwidth=.6in}
\\pagestyle{empty}
\\title{}
      [NO-DEFAULT-PACKAGES]
      [NO-PACKAGES]"
     ("\\section{%s}" . "\\section*{%s}")
     ("\\subsection{%s}" . "\\subsection*{%s}")
     ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
     ("\\paragraph{%s}" . "\\paragraph*{%s}")
     ("\\subparagraph{%s}" . "\\subparagraph*{%s}")))

Of course, this can be customized to your own preference; e.g.,
North-Americans may not be using A4-paper.

org-mode takes care of the export from its own format to LaTeX, but we need
to tell it to use xelatex to process the LaTeX to PDF:

(setq org-latex-to-pdf-process 
  '("xelatex -interaction nonstopmode %f"
     "xelatex -interaction nonstopmode %f")) ;; for multiple passes

That's all that's needed on the setup-side.

creating a document

Now, let's create a little test document, test.org, to show how it works:

#+LaTeX_CLASS: djcb-org-article
#+TITLE: My little document

* Introduction
  
  This is my document. There are many like it, but this is mine. It's easy to
  write without *too* _many_ /distractions/.
  
** Normal distribution

   Probability density of the normal distribution, using familiar TeX notation
   for formulae:
 
   $$\frac{1}{\sqrt{2\pi\sigma^2}}e^{ -\frac{(x-\mu)^2}{2\sigma^2} }$$

** Some table

| *Greek God* | *Roman God* | *Element*      |
|-------------+-------------+----------------|
| Zeus        | Jupiter     | Sky and clouds |
| Hera        | Juno        | Family         |
| Poseidon    | Neptune     | Sea            |
| Hades       | Pluto       | Underworld     |

We can export this to a PDF using C-c C-e p (or C-c C-e d to
automatically open the PDF in a PDF-viewer). This should all work nicely; if
it doesn't, note that when exporting, say, test.org, org-mode will create
a file called test.tex, and visit in a buffer. There's also a buffer with
the output from various commands, but sometimes it can be useful to run LaTeX
(xelatex in this case) on the file by hand, to find any problems. The
wonderful org-documentation about exporting to LaTeX has more information.

I think the result is pretty nice – it stays true to the class LaTeX article
class, but freshens it up a bit with some news font. If you can make
something better – which is not unlikely – you are of course invited to
contribute your own!

Concluding

org-mode is a pretty convenient way to write nice-looking PDFs. Combined
with xelatex, they don't have to look too plain :). However, I'm aware of
my limitations when it comes to the coolness/aesthetic aspects, but I hope
others can show the way here.

Maybe org-mode could ship with a number of ready-made templates to make
it easy to make nice-looking documents, resumes, reference cards, reports,
meeting notes and so on.

searching e-mails with wanderlust and mu

I have discussed the Wanderlust e-mail client a couple of times already. I'm
still using it, so I keep on learning new tricks. Even though there has been
quite a bit of action in the competing gnus e-mail client, for my particular
use-case, Wanderlust is still the best option.

'My particular use-case' consists of storing my mail in Maildirs, which I fill
with either offlineimap (which has fortunately found a new maintainer) or
fetchmail.

mu

When dealing with e-mail, one particularly important feature for me is the
ability to search my messages. In fact, it's so important for me that I
wrote some software to do this for me; the software is called mu; it indexes
the messages in my Maildirs, and then allows for searching them using
queries, based on message contents, headers, or other message properties.

mu works through a command-line interface, although there is an
experimental GUI available as well. The command-line interface makes it
possible to hook mu up with various mail-clients, such as mutt, or
Wanderlust. Some Linux distributions ship mu, but since the versions they
ship are often a bit outdated, I recommend building it yourself from the
sources linked on the mu website. The process is fairly straightforward;
and there is plenty of documentation in the form of man pages.

mu and wanderlust

I've been combining mu and wanderlust for a while (see mu and wanderlust - the old way, below), but this week Sam B. on the mu mailing
list showed a way to do so in a much more elegant way - using virtual or
query folders.

How does this work? Well, after installing mu, add the following to your
Wanderlust setup file (~/.wl or it's moral equivalent – see the older
Wanderlust posts for the details):

(require 'elmo-search)
(elmo-search-register-engine
    'mu 'local-file
    :prog "/usr/local/bin/mu" ;; or wherever you've installed it
    :args '("find" pattern "--fields" "l") :charset 'utf-8)

(setq elmo-search-default-engine 'mu)
;; for when you type "g" in folder or summary.
(setq wl-default-spec "[")

So, to start with the last part, whenever you type g in folder or summary,
in the mode-line you will get something like Folder name (.inbox): [. Now
simply type your mu search expression and press Enter, and wanderlust
opens a (temporary) folder with the search results. Brilliant!

Next, to add virtual folders for searches you do often, simply add some
folder specifications like the following to your .folders file (again,
check the older Wanderlust posts if you're not familiar with folders-file):

VFolders {
# message I received today
  [date:today..now]!mu  "Today"

# messages bigger than 1Mb  
  [size:1m..100m]!mu    "Big"

# signed messages i got in 2010 related to emacs
  [date:2010..2011 flag:signed emacs]!mu "Signed-Emacs2010"

# unread messages
  [not flag:seen]!mu    "Unread"
# or (for mu  >= 0.9.4):
# [flag:unread]! mu      "Unread"
}

After this, restart Wanderlust, and there you go! Wanderlust will display
your brand new virtual folders with an icon that looks like a little whale.

You can put arbitrary mu search expressions between the [], matching
whatever is useful in a certain case. Check the mu documentation to see how
to do this.

Note, the messages you get in these virtual folders are links to the
original messages. In practice, this means that changes you make to the links
do no affect the originals – if you delete a link you're not deleting the
message.

mu and wanderlust - the old way

This discussion would not complete without a description of the old way I
used search. This method may still be useful for integrating mu with other
clients such as mutt.

What I've been using for a while is a (in retrospect) rather clumsy way to
integrate message searches with Wanderlust: based on the results of a query,
I would create some special Maildir and fill it with symbolic links to the
matched messages, and the visit this special Maildir with Wanderlust. I'll
include the code here to contrast it with the more elegant solution that we
saw before, but also because the approach taken might be easily adapted for
other mail-clients.

;; search using mutt
(defvar mu-wl-mu-program     "/usr/local/bin/mu")
(defvar mu-wl-search-folder  "search")

(defun mu-wl-search ()
  "search for messages with `mu', and jump to the results"
   (let* ((muexpr (read-string "Find messages matching: "))
          (sfldr  (concat elmo-maildir-folder-path "/"
                    mu-wl-search-folder))
          (cmdline (concat mu-wl-mu-program " find "
                      "--clearlinks --format=links --linksdir='" sfldr "' "
                     muexpr))    
          (rv (shell-command cmdline)))
    (cond
      ((= rv 0)  (message "Query succeeded"))
      ((= rv 2)  (message "No matches found"))
      (t (message "Error running query")))
  (= rv 0)))

(defun mu-wl-search-and-goto ()
  "search and jump to the folder with the results"
  (interactive)
  (when (mu-wl-search)
    (wl-summary-goto-folder-subr
      (concat "." mu-wl-search-folder)
      'force-update nil nil t)
    (wl-summary-sort-by-date)))

;; search by pressing 'Q'
(define-key wl-summary-mode-map (kbd "Q") ;; => query
  '(lambda()(interactive)(mu-wl-search-and-goto))) 
(define-key wl-folder-mode-map (kbd "Q") ;; => query
  '(lambda()(interactive)(mu-wl-search-and-goto))) 

After installing mu and putting the above in your wanderlust startup
file, you should be able to search by pressing Q. The mu documentation
has an example for mutt as well.

conclusion

It's straightforward to integrate advanced searching capabilities to
Wanderlust using mu, and thanks to Sam B., it's gotten a lot easier! The
second (old) approach may be useful as 'inspiration' for use in other e-mail
clients as well, if they do not provide the kind of hooks that the first
solution needs.

IELM: a REPL for emacs

Emacs-lisp (elisp) is a nice language to play around with code and try things as
you develop them – explorative programming. I often use the *scratch*
buffer for that, but sometimes it's nice to use a so-called 'REPL' (
Read-Eval-Print-Loop) instead. A REPL is a sort-of command-line interface
where your expressions are evaluated as soon as they are considered 'complete'
and you press Enter.

So, enter Emacs's built-in repl: IELM. You can activate it with M-x ielm,
and the interaction looks something like the following:

*** Welcome to IELM ***  Type (describe-mode) for help.
ELISP> 123 
123
ELISP> (+ 1 2)
3
ELISP> ;; comment
ELISP> (defun fac (n)
         (if (= 0 n)
           1
           (* n (fac (- n 1)))))
fac
ELISP> (fac 5)
120
ELISP> 

By default, IELM evaluates complete expressions automatically as soon you as
you press Enter. So one thing to remember is that if you want to have
multi-line expression (like above), you must make sure that after each line
the expression is not complete (i.e., the brackets are not balanced) --
otherwise the expression will be evaluated too early. That makes modes like
autopair or paredit a bit inconvenient for this.

If you don't like that behavior, you can do:

(setq ielm-dynamic-return nil)

which will allow you to Enter as much as you want and only evaluate things when
you press C-j. But then you might as well use *scratch* I
suppose. Personally, I use IELM mostly as a calculator.

executable source code blocks with org-babel

org-babel is the mechanism that org-mode offers for evaluating (executing)
blocks of source code embedded in your org-mode-documents. This is useful
for so-called reproducible research, i.e., where you allow your readers to go
through the steps that led to your results.

Here, I'm just scratching the surface with some simple examples.

source code blocks

Let's first look at how it all began: source code blocks. I guess most
org-mode-users will be familiar with those: the ability to include
syntax-highlighted ('font-locked') snippets of source code in
org-documents. We discussed source blocks before, they look like this:

#+begin_src perl
sub my_func {
        print "Hello, world!\n";
}
#+end_src

And note that code blocks can be edited in their 'native mode' using C-c'= (or, =org-edit-src-code).

When code block like this are exported to, say, HTML, they'll look like the
following fully highlighted snippet (assuming you're reading Emacs-fu in
it's full-color version):

sub my_func {
        print "Hello, world!\n";
}

evaluating source code

org-babel takes this a few steps further: instead of just looking at
source code, we can actually evaluate (execute) it, using the
org-mode-based system called org-babel.

If you have a recent version of org-mode (7.x or later), add the
following to your .emacs (or equivalent):

(org-babel-do-load-languages
 'org-babel-load-languages
  '( (perl . t)         
     (ruby . t)
     (sh . t)
     (python . t)
     (emacs-lisp . t)   
   ))

This enables org-babel for the mentioned languages; there are many
other languages available as well.

Now, suppose we have a snippet of python in an org-mode-buffer:

#+begin_src python
def hello(str):
        return "Hello, " + str + "!"
return hello ("dude")
#+end_src

You can move the cursor (point) inside the src-block and press C-c C-c (or,
org-confirm-babel-evaluate). This causes the block of code to be evaluated
(executed), after asking you for confirmation. The result will inserted below
the block, like:

#+results:
: Hello, dude!

Note, in the hello example, the result of the block is the value of the
evaluation - that is, the value of the last expression evaluated. This is
the also the default, so we don't need to (but could) write:

#+begin_src python :results value

The alternative is to use the (standard) output of the function, which is
activated with :results output, e.g.:

#+begin_src sh :results output
   echo "Hello $USER! Today is `date`"
#+end_src

Moving to this block and pressing C-c C=c would get you something like
the following – probably with a different username and time:

˜#+results:
: Hello djcb! Today is Sun Feb 27 13:51:50 EET 2011

almost like functions

org-babel also allows you to refer to the code blocks from elsewhere in
your document, by labeling your code-blocks with srcname. Let's say we
have some Ruby code to revert a string:

#+begin_src ruby
def revert(s)
  if s == "" then 
    return ""
  else
    return s[-1].chr + revert(s.slice(0, s.length()-1))
  end
end
revert(str)
#+end_src

We can now 'call' this block; note that we get the result of evaluating the block. So if you want to use the result of a function in the block, you also
need to add the call to that function (see the last line).

Now, we can use:

#+call: revert(str="VeryCoolStuff")

And we get:

: ffutSlooCyreV

Note, due to some limitation/bug in my version of org-babel, the strings
should not contain spaces or other special characters, so the following
will give result in an error note:

˜#+call: revert(str="Very Cool Stuff")

Whenever you try to evaluate a code block, emacs will ask for confirmation --
this is important, because of the obvious security implications of executing
unknown code. Anyway, if you do trust the code, you can use the following
to skip the confirmation:

(setq org-confirm-babel-evaluate nil)

These simple examples do not really capture the power that org-babel
brings, but it's a start. There is quite a bit of documentation for
org-babel to help you further. Finally, if you are already using
org-babel, feel free to share your experiences in the comments!

keeping your secrets secret

If you want to keep your secrets secret, it is a good idea to encrypt your
data; I usually do that for files with passwords for various services, banking
data, and so on. Since version 23, Emacs includes a package called EasyPG (an
interface to GnuPG) which makes this seamless – just make sure that you have
GnuPG installed.

It's easy to use EasyPG – the only thing you need to do is adding the .gpg
-extension to your files, and EasyPG will automatically encrypt/decrypt them
when writing/reading. So, for example, to create an encrypted org-mode-file,
simply visit (C-x C-f) a file with a name like myfile.org.gpg; emacs opens
this in Org-Mode (just like any .org-file). When you want to save the file,
emacs will ask you for a password, and with this same password, you can open
it again. Don't forget that password!

account data

You can store any kind of secret data in your encrypted files. One type I
find particularly useful is to store account data (user names, passwords)
for various services there. For example, I use the emacs identi.ca-mode client, which gets its account data through variables identica-username and
identica-password.

I do not want to put this information in my main .emacs file for safety
reasons, but instead, put it an encrypted file, together with the account data
for other services (mail, twitter etc.). Emacs' require does not understand
encrypted files, but load-library does. To deal with that, I have two files,
secrets.el and secrets.el.gpg (in my load-path):

;; secrets.el
(load-library "secrets.el.gpg")
(provide 'secrets)

and

;; secrets.el.gpg
(setq identica-username "djcb"
      identica-password "$ekr3t")
;; ... other passwords ...

Now, in my .emacs I have a function for various services, like:

(defun start-identica ()
  (interactive)
  (require 'secrets)
  (identica-friends-timeline))

This will prompt me for the password, but only if I use anything that requires
the secret data, and only once per session.

Update: as Richard notes in the comments, you can also use require by
explicitly specifying the filename (parameter two). That might actually be easier --
thanks Richard!

using public keys

By default, EasyPG performs symmetric encryption; if you want to use public key encryption instead (useful when you want to share the encrypted files with
others), you can use:

;; 'silent to use symmetric encryption
;; nil to ask for users unless specified
;; t to always ask for a user
(setq epa-file-select-keys t) 

The 'users' in this snippet are the people in your GnuPG-keyring – EasyPG
lists your keyring inhabitants, allowing for easy selection. You can also
specify the people who can decrypt your file by putting something like the
following at the beginning of the file you want to encrypt.

# -*- epa-file-encrypt-to: ("foo@bar.org") -*-

so

EasyPG brings more functionality for encryption, decryption, signing, managing
your keyring and so on, but I haven't used that much yet. Anyhow, the
automatic support for reading/writing file is really nice.

extending ERC with your own commands

ERC is the leading Emacs-based IRC-client; I already discussed ERC before. I
have been using ERC a lot in recent times, as it's an essential way to
communicate at work with team members in remote locations. There are other
IRC-clients – most people around me seem to use either irssi or xchat,
but these don't integrate so well with my emacs-based workflow, the easy with
which it can be extended to do exactly what I want; in this although they have
their own strenghts. One of the great strengths of ERC is article I give some
examples.

Apart from chatting, you can send commands (long list) to the IRC-server,
for example to request information about other users, change your 'nick',
leave the channel, and so on. As in most IRC-clients, you can send these
commands with ERC by prefixing them with /, so you'd type:

/nick ninjaturtle

to change your nickname.

The nice thing about ERC is how easy it to add your own commands to this. In
your .emacs (after loading ERC), you can add something like:

(defun erc-cmd-MYSYSTEM ()
  "show some information about my system"
  (let ((str (shell-command-to-string "uname -a")))
    (when str (erc-send-message str))))

Or, add add a function called erc-cmd-XXXX (with the XXXX being the
command name in capitals, will add command XXXX, which you can invoke with
/XXXX or /xxxx). So, with the above function, I can now do something like:

ERC> /mysystem
<djcb> Linux cthulhu 2.6.35-25-generic #44 SMP Fri Jan 21 17:40:48 UTC
       2011 i686 GNU/Linux

Let's look at some other (somewhat) useful command: /calc; again, just a
small example, I'm sure something can come up with something a bit more
elegant - perhaps using emacs' built-in calc.

(defun erc-cmd-CALC (&rest args)
  "calculate value of some expression using bc"
  (let ((expr (mapconcat 'identity args " ")))
    (when (length expr)
      (let ((result (shell-command-to-string (concat "echo '" expr "' | bc "))))
        (when result (erc-send-message (concat expr " = " result)))))))

ERC> /calc 2 * (3 + 4) / 7
<djcb> 2 * (3 + 4) / 7  = 2

Now, a small warning, just because it's easy to dump the output of, say,
cowsay in an IRC-channel using your own /cowsay command, does not mean it is
a good idea – in fact, using something like that is guaranteed to get you
kicked out fairly quickly from many channels.

That being said, I'm sure many people have come up with much more clever
things than the examples here; feel free to share your inventions in the
comments!