Warning: this is an htmlized version!
The original is across this link,
and the conversion rules are here.
\def\myversion{2005jul25  2:05}

\documentclass[12pt]{article}
\usepackage{sbc2003}
% \def\address#1{\gdef\@address{#1}}
\usepackage{graphicx,url}
\usepackage[latin1]{inputenc}  
\sloppy

% «.abstract»			(to "abstract")
% «.note»			(to "note")
% «.three-kinds-of-interfaces»	(to "three-kinds-of-interfaces")
% «.one-thing-well»		(to "one-thing-well")
% «.making-progs-receive-cmds»	(to "making-progs-receive-cmds")
% «.sending-commands»		(to "sending-commands")
% «.hyperlinks»			(to "hyperlinks")
% «.shorter-hyperlinks»		(to "shorter-hyperlinks")
% «.forward-and-back»		(to "forward-and-back")
% «.dangerous-hyperlinks»	(to "dangerous-hyperlinks")
% «.generating-hyperlinks»	(to "generating-hyperlinks")
% «.returning»			(to "returning")
% «.local-copies»		(to "local-copies")
% «.glyphs»			(to "glyphs")
% «.compose-pairs»		(to "compose-pairs")
% «.delimited-regions»		(to "delimited-regions")
% «.channels»			(to "channels")
% «.channels-implementation»	(to "channels-implementation")
% «.anchors»			(to "anchors")
% «.e-scripts»			(to "e-scripts")
% «.splitting-eev.el»		(to "splitting-eev.el")
% «.eesteps»			(to "eesteps")
% «.big-modular-e-scripts»	(to "big-modular-e-scripts")
% «.iskidip»			(to "iskidip")
% «.availability»		(to "availability")

% (eek "C-a C-q 233 C-o")

\long\def\IGNORE#1\ENDIGNORE{}

\IGNORE
;;*
;; (ee-once (eeb-eval))
(defun mkto2 () (interactive)
  (mkto) (eek "<up> C-a C-SPC <down> C-w")
  (save-excursion (ee-goto-position "\233") (eek "C-a C-y")))
(defun c () (interactive)
  (eev "cd ~/eev-current/article/; rm eev.aux
    latex eev.tex && latex eev.tex && rexdvi eev.dvi"))
(defun c1 () (interactive)
  (eev "cd ~/eev-current/article/; rm eev.aux
    latex eev.tex && rexdvi eev.dvi"))
;;*
\ENDIGNORE

\title{Emacs and eev, or: How to Automate Almost Everything}
\author{Eduardo Ochs}
\address{\texttt{http://angg.twu.net/} \\
         \email{edrx@mat.puc-rio.br} \\
         Not currently affiliated to any institution. \\
         Snail-mail address: R.\ Jardim Botânico 622/103B, Jardim
         Botânico, Rio de Janeiro, RJ, Brazil, CEP 22461-000.
        }
\begin{document} 
\maketitle
\begin{abstract}
% «abstract»  (to ".abstract")
%
Interacting with programs with command-line interfaces always involves
a bit of line editing, and each CLI program tends to implement
independently its own minimalistic editing features. We show a way of
centralizing these editing tasks by making these programs receive
commands that are prepared, and sent from, Emacs. The resulting system
is a kind of Emacs- and Emacs Lisp-based ``universal scripting
language'' in which commands can be sent to both external programs and
to Emacs itself either in blocks or step-by-step under very fine
control from the user.
\end{abstract}

% (find-fline "~/FISL/eev.tex")
% (find-fline "~/tmp/fisl.txt")
% (eev "cd ~/FISL/; latex eev.tex && rexdvi eev.dvi &")

\def\myttbox#1{{\setbox0=\hbox{\texttt{a}}\hbox to \wd0{\hss#1\hss}}}
\catcode`*=13 \def*{\myttbox{$\bullet$}}
\catcode`«=13 \def«{\myttbox{$\langle\!\langle$}}
\catcode`»=13 \def»{\myttbox{$\rangle\!\rangle$}}
\catcode`×=13 \def×{\myttbox{$\times$}}                       % used only once
\catcode`ª=13 \defª{\myttbox{${}^{\underline{\mathtt{a}}}$}}  % used only once
\catcode`›=13 \def›{}
\def\lrang#1{\hbox{$\langle$#1$\rangle$}}

\IGNORE
(remove-from-keymap tex-mode-map ?\")
(defun m (s e str)
  (interactive "r\nsColor: ")
  (if (equal str "") (setq str "chocolate3"))
  (set-text-properties s e `(face (:foreground ,str))))
;;
;; (find-fline "~/FISL/README")
\ENDIGNORE

\bigskip

\fbox{\parbox{5in}{

% «note»  (to ".note")

{\bf Note:} this is a working draft that has many pieces missing and
needs urgent revision on the pieces it has. Current version:
\myversion. Newer versions are being uploaded to
\lrang{http://angg.twu.net/eev-current/article/}, and two animations
(in Flash) showing eev at work can be found at:

\par\noindent
\lrang{http://angg.twu.net/eev-current/anim/channels.anim.html} and
\par\noindent
\noindent \lrang{http://angg.twu.net/eev-current/anim/gdb.anim.html}.

}}





%%%%%
%  _   _                     _       _             __                     
% | |_| |__  _ __ ___  ___  (_)_ __ | |_ ___ _ __ / _| __ _  ___ ___  ___ 
% | __| '_ \| '__/ _ \/ _ \ | | '_ \| __/ _ \ '__| |_ / _` |/ __/ _ \/ __|
% | |_| | | | | |  __/  __/ | | | | | ||  __/ |  |  _| (_| | (_|  __/\__ \
%  \__|_| |_|_|  \___|\___| |_|_| |_|\__\___|_|  |_|  \__,_|\___\___||___/
% 
%%%%%

\section{Three kinds of interfaces}
% «three-kinds-of-interfaces»  (to ".three-kinds-of-interfaces")

Interactive programs in a Un*x system%
%
\footnote{Actually we are more interested in GNU systems than in
``real'' Unix systems; the reasons will become clear in the section
nnn. By the way: the term ``Unix'' is Copyright (C) Bell Labs).}
%
can have basically three kinds of interfaces: they can be
mouse-oriented, like most programs with graphical interfaces nowadays,
in which commands are given by clicking with the mouse; they can be
character-oriented, like most editors and mail readers, in which most
commands are single keys or short sequences of keys; and they can be
line-oriented, as, for example, shells are: in a shell commands are
given by editing a full line and then typing ``enter'' to process that
line.

It is commonplace to classify computer users in a spectrum where the
``users'' are in one extreme and the ``programmers'' are in the other;
the ``users'' tend to use only mouse-oriented and character-oriented
programs, and the ``programmers'' only character-oriented and
line-oriented programs.

In this paper we will show a way to ``automate'' interactions with
line-oriented programs, and, but not so well, to character-oriented
programs; more precisely, it is a way to edit commands for these
programs in a single central place --- Emacs --- and then send them to
the programs; re-sending the same commands afterwards, with or without
modifications, then becomes very easy.

This way (``e-scripts'') can not be used to send commands to
mouse-oriented programs --- at least not without introducing several
new tricks. But ``programmers'' using Un*x systems usually see most
mouse-oriented programs --- except for a few that are {\sl
intrinsically} mouse-oriented, like drawing programs --- as being just
wrappers around line-oriented programs than perform the same tasks
with different interfaces; and so, most mouse-oriented programs ``do
not matter'', and our method of automating interactions using
e-scripts can be used to automate ``almost everything''; hence the
title of the paper.


%%%%%                 _   _     _                            _ _ 
%   ___  _ __   ___  | |_| |__ (_)_ __   __ _  __      _____| | |
%  / _ \| '_ \ / _ \ | __| '_ \| | '_ \ / _` | \ \ /\ / / _ \ | |
% | (_) | | | |  __/ | |_| | | | | | | | (_| |  \ V  V /  __/ | |
%  \___/|_| |_|\___|  \__|_| |_|_|_| |_|\__, |   \_/\_/ \___|_|_|
%                                       |___/                    
%%%%%

\section{``Make each program do one thing well''}
% «one-thing-well»  (to ".one-thing-well")

One of the tenets of the Unix philosophy is that each program should
do one thing, and do it well; this is a good design rule for Unix
programs because the system makes it easy to invoke external programs
to perform tasks, and to connect programs.

Some of parts of a Unix system are more like ``meta-programs'' or
``sub-programs'' than like self-contained programs that do some
clearly useful task by themselves. Shells, for example, are
meta-programs: their main function is to allow users to invoke ``real
programs'' and to connect these programs using pipes, redirections,
control structures (if, for, etc) and Unix ``signals''. On the other
hand, libraries are sub-programs: for example, on GNU systems there's
a library called GNU readline that line-oriented programs can use to
get input; if a program, say, bc (a calculator) gets its input by
calling readline(...) instead of using the more basic function
fgets(...) then its line-oriented interface will have a little more
functionality: it will allow the user to do some minimal editing in
the current line, and also to recall, edit and issue again some of the
latest commands given.



%%%%%                _       _                                        _     
%  _ __ ___  ___ ___(_)_   _(_)_ __   __ _    ___ _ __ ___  _ __   __| |___ 
% | '__/ _ \/ __/ _ \ \ \ / / | '_ \ / _` |  / __| '_ ` _ \| '_ \ / _` / __|
% | | |  __/ (_|  __/ |\ V /| | | | | (_| | | (__| | | | | | | | | (_| \__ \
% |_|  \___|\___\___|_| \_/ |_|_| |_|\__, |  \___|_| |_| |_|_| |_|\__,_|___/
%                                    |___/                                  
%%%%%

\section{Making programs receive commands}
% «making-progs-receive-cmds»  (to ".making-progs-receive-cmds")
\label{ee}

Many line-oriented programs allow ``scripting'', which means executing
commands from a file. For example, in most shells we can say ``source
\~{}/ee.sh'', and the shell will then execute the commands in the file
\~{}/ee.sh. There are other ways of executing commands from a file ---
like ``sh \~{}/ee.sh'' --- but the one with ``source'' is the one that
we'll be more interested in, because it is closer to running the
commands in \~{}/ee.sh one by one by hand: for example, with ``source
\~{}/ee.sh'' the commands that change parameters of the shell --- like
the current directory and the environment variables --- will work in
the obvious way, while with ``sh \~{}/ee.sh'' they would only change
the parameters of a temporary sub-shell; the current directory and the
environment variables of the present shell would be ``protected''.

So, it is possible to prepare commands for a shell (or for scriptable
line-oriented programs; for arbitrary line-oriented programs see the
section nnn) in several ways: by typing them at the shell's interface
--- and if the shell uses readline its interface can be reasonably
friendly --- or, alternatively, by using a text editor to edit a file,
say, \~{}/ee.sh, and by then ``executing'' that file with ``source
\~{}/ee.sh''. ``source \~{}/ee.sh'' is a lot of keystrokes, but that
can be shortened if we can define a shell function: by putting

\begin{verbatim}
  function ee () { source ~/ee.sh; }
\end{verbatim}
%
in the shell's initialization file (\~{}/.bashrc, \~{}/.zshrc, ...) we
can reduce ``source \~{}/ee.sh'' to just ``ee'': e, e, enter --- three
keystrokes.

We just saw how a shell --- or, by the way, any line-oriented program
in which we can define an `ee' function like we did for the shell ---
can receive commands prepared in an external editor and stored in a
certain file; let's refer to that file, \~{}/ee.sh, as a ``temporary
script file''. Now it remains to see how an external text editor can
``send commands to the shell'', i.e., how to make the editor save some
commands in a temporary script file in a convenient way, that is,
without using too many keystrokes...



%%%%%                 _ _                                        _
%  ___  ___ _ __   __| (_)_ __   __ _    ___ _ __ ___  _ __   __| |___ 
% / __|/ _ \ '_ \ / _` | | '_ \ / _` |  / __| '_ ` _ \| '_ \ / _` / __|
% \__ \  __/ | | | (_| | | | | | (_| | | (__| | | | | | | | | (_| \__ \
% |___/\___|_| |_|\__,_|_|_| |_|\__, |  \___|_| |_| |_|_| |_|\__,_|___/
%                               |___/                                  
%%%%%

\section{Sending commands}
% «sending-commands»  (to ".sending-commands")
\label{eev}

GNU Emacs, ``the extensible, self-documenting text-editor'' ([S79]),
does at least two things very well: one is to edit text, and so it can
be used to edit temporary scripts, and thus to send commands to shells
and to line-oriented programs with `ee' functions; and the other one
is to run Lisp. Lisp is a powerful programming language, and (at least
in principle!) any action or series of actions can be expressed as a
program in Lisp; the first thing that we want to do is a way to mark a
region of a text and ``send it as commands to a shell'', by saving it
in a temporary script file. We implement that in two ways:

\begin{verbatim}
   1: (defun ee (s e)
   2:   "Save the region in a temporary script"
   3:   (interactive "r")
   4:   (write-region s e "~/ee.sh"))
   5:
   6: (defun eev (s e)
   7:   "Like `ee', but the script executes in verbose mode"
   8:   (interactive "r")
   9:   (write-region
  10:    (concat "set -v\n" (buffer-substring s e)
  11:            "\nset+v")
  12:    nil "~/ee.sh"))
\end{verbatim}
%
`ee' (the name stands for something like `emacs-execute') just saves
the currently-marked region of text to \~{}/ee.sh; `eev' (for
something like `emacs-execute-verbose') does the same but adding to
the beginning of the temporary script a command to put the shell in
``verbose mode'', where each command is displayed before being
executed, and also adding at the end an command to leave verbose mode.

We can now use `ee' and `eev' to send a block of commands to a shell:
just select a region and then run `ee' or `eev'. More precisely: mark
a region, that is, put the cursor at one of the extremities of the
region, then type C-SPC to set Emacs's ``mark'' to that position, then
go to other extremity of the region and type M-x eev (C-SPC and M-x
are Emacs's notations for Control-Space and Alt-x, a.k.a. ``Meta-x'').
After doing that, go to a shell and make it ``receive these
commands'', by typing `ee'.


%%%%%
%  _                           _ _       _        
% | |__  _   _ _ __   ___ _ __| (_)_ __ | | _____ 
% | '_ \| | | | '_ \ / _ \ '__| | | '_ \| |/ / __|
% | | | | |_| | |_) |  __/ |  | | | | | |   <\__ \
% |_| |_|\__, | .__/ \___|_|  |_|_|_| |_|_|\_\___/
%        |___/|_|                                 
%%%%%

\section{Hyperlinks}
% «hyperlinks»  (to ".hyperlinks")
\label{hyperlinks}
\label{C-xC-e}

% When we are learning Un*x --- and until the point where we become a
% genius or an {\sl idiot savant} who knows all the documentation
% files by heart; but I've been using GNU systems for 10 years and I'm
% neither of these yet --- we spend a lot of the time when we are not
% issuing commands (which are mostly to shells) accessing and reading
% documentation files; and we can use Emacs Lisp ``one-liners'' to
% create ``hyperlinks'' to files:

When we are using a system like *NIX, in a part of the time we are
using programs with which we are perfectly familiar, and in the rest
of the time we are using things that we don't understand completely
and that make us have to access the documentation from time to time.
In a GNU system the documentation is all on-line, and the steps needed
to access any piece of documentation can be automated. We can use
Emacs Lisp ``one-liners'' to create ``hyperlinks'' to files:

\begin{verbatim}
  A: (info "(emacs)Lisp Eval")
  B: (find-file "~/usrc/busybox-1.00/shell/ash.c")
  C: (find-file "/usr/share/emacs/21.4/lisp/info.el")
\end{verbatim}

These expressions, when executed --- which is done by placing the
cursor after them and then typing C-x C-e, or, equivalently, M-x
eval-last-sexp --- will ($A$) open a page of Emacs manual (the manual
is a set of files in ``Info'' format), ($B$) open the source file
`shell/ash.c' of a program called busybox, and ($C$) open the file
`info.el' from the Emacs sources, respectively. As some of these files
and pages can be very big, these hyperlinks are not yet very
satisfactory: we want ways to not only open these files and pages but
also to ``point to specific positions'', i.e., to make the cursor go
to these positions automatically. We can do that by defining some new
hyperlink functions, that are invoked like this:

\begin{verbatim}
  A': (find-node "(emacs)Lisp Eval" "C-x C-e")
  B': (find-fline "~/usrc/busybox-1.00/shell/ash.c"
                  "void\nevalpipe")
  C': (find-fline "/usr/share/emacs/21.4/lisp/info.el"
                  "defun info")
\end{verbatim}

The convention is that these ``extended hyperlink functions'' have
names like `find-{\sl xxx}node', `find-{\sl xxx}file', or `find-{\sl
  xxxyyy}'; as the name `find-file' was already taken by a standard
Emacs function we had to use `find-fline' for ours.

Here are the definitions of `find-node' and `find-fline':

\begin{verbatim}
  14: (defun ee-goto-position (&optional pos-spec)
  15:   "If POS-SPEC is a string search for its first
  16:    occurrence in the file; if it is a number go to the
  17:    POS-SPECth line; if it is nil, don't move."
  18:   (cond ((null pos-spec))
  19:         ((numberp pos-spec)
  20:          (goto-char (point-min))
  21:          (forward-line (1- pos-spec)))
  22:         ((stringp pos-spec)
  23:          (goto-char (point-min))
  24:          (search-forward pos-spec))
  25:         (t (error "Invalid pos-spec: %S" pos-spec))))
  26:
  27: (defun find-fline (fname &optional pos-spec)
  28:   "Like (find-file FNAME), but accepts a POS-SPEC"
  29:   (find-file fname)
  20:   (ee-goto-position pos-spec))
  31:
  32: (defun find-node (node &optional pos-spec)
  33:   "Like (info NODE), but accepts a POS-SPEC"
  34:   (info node)
  35:   (ee-goto-position pos-spec)))
\end{verbatim}

Now consider what happens when we send to a shell a sequence of
commands like this one:

\begin{verbatim}
  # (find-node "(gawk)Fields")
  seq 4 9 | gawk '{print $1, $1*$1}'
\end{verbatim}
%
the shell ignores the first line because of the `\#', that makes the
shell treat that line as a comment; but when we are editing that in
Emacs we can execute the `(find-node ...)' with C-x C-e. Hyperlinks
can be mixed with shell code --- they just need to be marked as
comments.

Note: the actual definitions of `eev', `ee-goto-position',
`find-fline' and `find-node' in eev's source code are a bit more
complex than the code in the listings above (lines 6--12 in the
previous section and 14--35 in the current section). In all the (few)
occasions in this paper where we will present the source code of eev's
functions what will be shown are versions that implement only the
``essence'' of those functions, stripped down of all extra
functionality. The point that we wanted to stress with those listings
is how natural it is to use Emacs in a certain way, as an editor for
commands for external programs, and with these plain-text hyperlinks
that can be put almost anywhere: the essence of that idea can be
implemented in 30 lines of Lisp and one or two lines of shell code.

[See also: Section \ref{e-scripts}]





%%%%%
%      _                _              _ _       _        
%  ___| |__   ___  _ __| |_ ___ _ __  | (_)_ __ | | _____ 
% / __| '_ \ / _ \| '__| __/ _ \ '__| | | | '_ \| |/ / __|
% \__ \ | | | (_) | |  | ||  __/ |    | | | | | |   <\__ \
% |___/_| |_|\___/|_|   \__\___|_|    |_|_|_| |_|_|\_\___/
%                                                         
%%%%%

\section{Shorter Hyperlinks}
% «shorter-hyperlinks»  (to ".shorter-hyperlinks")

The hyperlinks in lines $A''$, $B''$ and $C''$, below,

\begin{verbatim}
  A'': (find-enode "Lisp Eval" "C-x C-e")
  B'': (find-busyboxfile "shell/ash.c" "void\nevalpipe")
  C'': (find-efile "info.el" "defun info")
\end{verbatim}
%
are equivalent to the ones labeled $A'$, $B'$, $C'$ in Section
\ref{hyperlinks}, but are a bit shorter, and they hide details like
Emacs's path and the version of BusyBox; if we switch to newer
versions of Emacs and BusyBox we only need to change the definitions
of `find-busyboxfile' and `find-efile' to update the hyperlinks.
Usually not many things change from one version of a package to
another, so most hyperlinks continue to work after the update.

Eev defines a function called `code-c-d' that makes defining functions
like `find-enode', `find-busyboxfile' and `find-efile' much easier:

\begin{verbatim}
  (code-c-d "busybox" "~/usrc/busybox-1.00/")
  (code-c-d "e" "/usr/share/emacs/21.4/lisp/" "emacs")
\end{verbatim}
%
The arguments for `code-c-d' are (1) a ``code'' (the ``{\sl xxx}'' in
a ``find-{\sl xxx}file''), (2) a directory, and optionally (3) the
name of a manual in Info format. The definition of code-c-d is not
very interesting, so we won't show it here.


%%%%%
%   __                                  _    ___     _                _    
%  / _| ___  _ ____      ____ _ _ __ __| |  ( _ )   | |__   __ _  ___| | __
% | |_ / _ \| '__\ \ /\ / / _` | '__/ _` |  / _ \/\ | '_ \ / _` |/ __| |/ /
% |  _| (_) | |   \ V  V / (_| | | | (_| | | (_>  < | |_) | (_| | (__|   < 
% |_|  \___/|_|    \_/\_/ \__,_|_|  \__,_|  \___/\/ |_.__/ \__,_|\___|_|\_\
%                                                                          
%%%%%

\section{Keys for following hyperlinks and for going back}
% «forward-and-back»  (to ".forward-and-back")
\label{M-e}

[Rewrite this; mention M-k, M-K, `to' and the (disabled) stubs to
  implement a `back' command]

It is so common to have Lisp hyperlinks that extend from some position
in a line --- usually after a comment sign --- to the end of the line
that eev implements a special key for executing these hyperlinks: the
effect of typing M-e (when eev is installed and ``eev mode'' is on) is
roughly the same of first going to the end of the line and then typing
C-x C-e; that is, M-e does the same as the key sequence C-e C-x
C-e\footnote{The main difference between M-e and C-e C-x C-e is how
  they behave when called with numeric ``prefix arguments'': for
  example, M-0 M-e highlights temporarily the Lisp expression instead
  of executing it and M-4 M-e executes it with some debugging flags
  turned on, while C-x C-e when called with any prefix argument
  inserts the result of the expression at the cursor instead of just
  showing it at the echo area.}.

[There are many other kinds of hyperlinks. Examples?]



%%%%%
%      _                                              _ _       _        
%   __| | __ _ _ __   __ _  ___ _ __ ___  _   _ ___  | (_)_ __ | | _____ 
%  / _` |/ _` | '_ \ / _` |/ _ \ '__/ _ \| | | / __| | | | '_ \| |/ / __|
% | (_| | (_| | | | | (_| |  __/ | | (_) | |_| \__ \ | | | | | |   <\__ \
%  \__,_|\__,_|_| |_|\__, |\___|_|  \___/ \__,_|___/ |_|_|_| |_|_|\_\___/
%                    |___/                                               
%%%%%

\section{Dangerous hyperlinks}
% «dangerous-hyperlinks»  (to ".dangerous-hyperlinks")

Note that these ``hyperlinks'' can do very dangerous things. If we
start to execute blindly every Lisp expression we see just because it
can do something interesting or take us to an interesting place then
we can end up running something like:

\begin{verbatim}
  (shell-command "r›m -Rf ~")
\end{verbatim}

which destroy all files in our home directory; not a good idea.
Hyperlinks should be a bit safer than that...

The modern approach to safety in hyperlinks --- the one found in web
browsers, for example --- is that following a hyperlink can execute
only a few kinds of actions, all known to be safe; the ``target'' of a
hyperlink is something of the form http://..., ftp://..., file://...,
info://..., mailto:... or at worst like javascript:...; none of these
kinds of actions can even erase our files. That approach limits a lot
what hyperlinks can do, but makes it harmless to hide the hyperlink
action and display only some descriptive text.

Eev's approach is the opposite of that. I wrote the first functions of
eev in my first weeks after installing GNU/Linux in my home machine
and starting using GNU Emacs, in 1994; before that I was using mostly
Forth (on MS-DOS), and I hadn't had a lot of exposure to *nix systems
by then --- in particular, I had tried to understand *nix's notions of
user IDs and file ownerships and permissions, and I felt that they
were a thick layer of complexity that I wasn't being able to get
through.

Forth's attitude is more like ``the user knows what he's doing''; the
system is kept very simple, so that understanding all the consequences
of an action is not very hard. If the user wants to change a byte in a
critical memory position and crash the machine he can do that, and
partly because of that simplicity bringing the machine up again didn't
use to take more than one minute (in the good old days, of course).
Forth people developed good backup strategies to cope with the
insecurities, and --- as strange as that might sound nowadays, where
all machines are connected and multi-user and crackers abound ---
using the system in the Forth way was productive and fun.

*NIX systems are not like Forth, but when I started using them I was
accustomed to this idea of achieving simplicity through the lack of
safeguards, and eev reflects that. The only thing that keeps eev's
hyperlinks reasonably safe is {\sl transparency}: the code that a
hyperlink executes is so visible that it is hard to mistake a
dangerous Lisp expression for a ``real'' hyperlink. Also, all the safe
hyperlink functions implemented by eev start with `find-', and all the
`find-' functions in eev are safe, except for those with names like
`find-{\sl xxx}sh' and `find-{\sl xxx}sh0: for example,

\begin{verbatim}
  (find-sh "wget --help" "recursive download")
\end{verbatim}
%
executes ``wget -{}-help'', puts the output of that in an Emacs buffer
and then jumps to the first occurrence of the string ``recursive
download'' there; other `find-{\sl xxx}sh' functions are variations on
that that execute some extra shell commands before executing the first
argument --- typically either switching to another directory or
loading an initialization file, like \~{}/.bashrc or \~{}/.zshrc. The
`find-{\sl xxx}sh0' functions are similar to their `find-{\sl xxx}sh'
counterparts, but instead of creating a buffer with their output they
just show it at Emacs's echo area and they use only the first argument
and ignore the others (the pos-spec).



%%%%%                              _   _               _ _       _        
%   __ _  ___ _ __   ___ _ __ __ _| |_(_)_ __   __ _  | (_)_ __ | | _____ 
%  / _` |/ _ \ '_ \ / _ \ '__/ _` | __| | '_ \ / _` | | | | '_ \| |/ / __|
% | (_| |  __/ | | |  __/ | | (_| | |_| | | | | (_| | | | | | | |   <\__ \
%  \__, |\___|_| |_|\___|_|  \__,_|\__|_|_| |_|\__, | |_|_|_| |_|_|\_\___/
%  |___/                                       |___/                      
%
%%%%%

\section{Generating Hyperlinks}
% «generating-hyperlinks»  (to ".generating-hyperlinks")

Do we need to remember the names of all hyperlinks functions, like
find-fline and find-node? Do we need to type the code for each
hyperlink in full by hand? The answers are ``no'' and ``no''.

Eev implements several functions that create temporary buffers
containing hyperlinks, that can then be cut and pasted to other
buffers. For example, `M-h M-f' creates links about an Emacs Lisp
function: typing `M-h M-f' displays a prompt in a minibuffer asking
for the name of an Elisp function; if we type, say, `find-file' there
(note: name completion with the TAB key works in that prompt) we get a
buffer like the one in figure~\ref{fig:M-h}.

% (find-eevex "screenshots.e" "fisl-screenshots-M-h")
% (find-fline "README" "ss-lua")
% (find-fline "")
% (find-eimage0 "./ss-lua.png")
%
\begin{figure}[tb]
% \includegraphics[scale=0.72]{ss-m-h.eps}
% \centerline{\includegraphics[scale=1.44]{ss-m-h.eps}}
\centerline{\includegraphics[scale=1.80]{ss-m-h.eps}}
\caption{\label{fig:M-h}the result of typing M-h M-f find-file}
\end{figure}

The first line of that buffer is a hyperlink to that
dynamically-generated page of hyperlinks. Its function ---
`find-efunction-links' --- has a long name that is hard to remember,
but there's a shorter link that will do the same job:

\begin{verbatim}
  (eek "M-h M-f find-file")
\end{verbatim}

The argument to `eek' is a string describing a sequence of keys in a
certain verbose format, and the effect of running, say,
\verb|(eek "M-h M-f find-file")| is the same as of typing `M-h M-f
find-file'.


[M-h is a prefix; \verb|(eek "M-h C-h")| shows all the sequences with
the same prefix.]

[Exceptions: M-h M-c, M-h M-2, M-h M-y. Show examples of how to edit
hyperlinks with M-h M-2 and M-h M-y.]

[Mention hyperlinks about a key sequence?
\verb|(eek "M-h M-k C-x C-f")|]
 
[Mention hyperlinks about a Debian package?]





%%%%%       _                    _             
%  _ __ ___| |_ _   _ _ __ _ __ (_)_ __   __ _ 
% | '__/ _ \ __| | | | '__| '_ \| | '_ \ / _` |
% | | |  __/ |_| |_| | |  | | | | | | | | (_| |
% |_|  \___|\__|\__,_|_|  |_| |_|_|_| |_|\__, |
%                                        |___/ 
%%%%%

\section{Returning from Hyperlinks}
% «returning»  (to ".returning")

[Mention M-k to kill the current buffer, and how Emacs asks for
  confirmation when it's a file and it's modified]

[Mention M-K for burying the current buffer]

[Mention what to do in the cases where a hyperlink points to the
  current buffer (section \ref{anchors}); there used to be an
  ``ee-back'' function bound to M-B, but to reactivate it I would have
  to add back some ugly code to `to'... (by the way, that included
  Rubikitch's contributions)]

[web browsers have a way to ``return'' from hyperlinks: the ``back''
button... In eev we have many kinds of hyperlinks, including some that
are unsafe and irreversible, but we have a few kinds of ``back''s that
work... 1) if the hyperlink opened a new file or buffer, then to kill
the file or buffer, use M-k (an eev binding for kill-this-buffer);
note that it asks for a confirmation when the buffer is associated to
a file and it has been modified --- or we can use bury-buffer; M-K is
an eev binding for bury-buffer. [explain how emacs keeps a list of
buffers?] Note: if the buffer contains, say, a manpage, or an html
page rendered by w3m, which take a significant time to generate, then
M-K is better is than M-k. 2) if the hyperlink was a `to' then it
jumped to another position in the same file... it is possible to keep
a list of previous positions in a buffer and to create an `ee-back'
function (suggestion: bind it to M-B) but I haver never been satisfied
with the implementations that I did so we're only keeping a hook in
`to' for a function that saves the current position before the jump]

[dto recommended winner-undo]



%%%%%
%  _                 _                   _           
% | | ___   ___ __ _| |   ___ ___  _ __ (_) ___  ___ 
% | |/ _ \ / __/ _` | |  / __/ _ \| '_ \| |/ _ \/ __|
% | | (_) | (_| (_| | | | (_| (_) | |_) | |  __/\__ \
% |_|\___/ \___\__,_|_|  \___\___/| .__/|_|\___||___/
%                                 |_|                
%%%%%

\section{Local copies of files from the internet}
% «local-copies»  (to ".local-copies")

Emacs knows how to fetch files from the internet, but for most
purposes it is better to use local copies. Suppose that the
environment variable $S$ is set to \~{}/snarf/; then running this on a
shell

\begin{verbatim}
  mkdir -p $S/http/www.gnu.org/software/emacs/
  cd       $S/http/www.gnu.org/software/emacs/
  wget http://www.gnu.org/software/emacs/emacs-paper.html

  # (find-fline "$S/http/www.gnu.org/software/emacs/emacs-paper.html")
  # (find-w3m   "$S/http/www.gnu.org/software/emacs/emacs-paper.html")
\end{verbatim}
%
creates a local copy of emacs-paper.html inside \~{}/snarf/http/. The
two last lines are hyperlinks to the local copy; `find-w3m' opens it
``as HTML'', using a web browser called w3m that can be run either in
standalone mode or inside Emacs; `find-w3m' uses w3m's Emacs
interface, and it accepts extra arguments, which are treated as a
pos-spec-list.

Instead of running the `mkdir', `cd' and `wget' lines above we can run
a single command that does everything:

\begin{verbatim}
  psne http://www.gnu.org/software/emacs/emacs-paper.html
\end{verbatim}
%
which also adds a line with that URL to a log file (usually
\~{}/.psne.log). It is more convenient to have a `psne' that changes the
current directory of the shell than one that doesn't, and for that it
must be defined as a shell function.

Eev comes with an installer script, called eev-rctool, that can help
in adding the definitions for eev (like the ``function ee () { source
~/ee.sh; }'' of section \ref{ee}) to initialization files like
~/.bashrc (such initialization files are termed ``rcfiles'').
Eev-rctool does {\sl not} add by default the definitions for `psne'
and for $S$ to rcfiles; however, it adds commented-out lines with
instructions, which might be something like:

\begin{verbatim}
  # To define $S and psne uncomment this:
  #   . $EEVTMPDIR/psne.sh
  # (find-eevtmpfile "psne.sh")
\end{verbatim}





%%%%%    _             _         
%   __ _| |_   _ _ __ | |__  ___ 
%  / _` | | | | | '_ \| '_ \/ __|
% | (_| | | |_| | |_) | | | \__ \
%  \__, |_|\__, | .__/|_| |_|___/
%  |___/   |___/|_|              
%
%%%%%
 
\section{Glyphs}
% «glyphs»  (to ".glyphs")

Emacs allows redefining how characters are displayed, and one of the
modules of eev --- eev-glyphs --- uses that to make some characters
stand out. Character 15, for example, is displayed on the screen by
default as '\verb|^O|' (two characters, suggesting ``control-O''),
sometimes in a different color from normal text\footnote{Determined by
the ``face'' escape-glyph-face, introduced in GNU Emacs in late
2004.}.

Eev changes the appearance of char 15 to make it be displayed as a red
star. Here is how: Emacs has some structures called ``faces'' that
store font and color information, and `eeglyphs-face-red' is a face
that says ``use the default font and the default background color, but
a red foreground''; eev's initialization code runs this,

\begin{verbatim}
  (eev-set-glyph 15 ?* 'eev-glyph-face-red)
\end{verbatim}
%
which sets the representation of char 15 to the ``glyph'' made of a
star in the face eeglyphs-face-red. 

For this article, as red doesn't print well in black and white, we
used this instead:

\begin{verbatim}
  (eev-set-glyph 15 342434)
\end{verbatim}
%
this made occurrences of char 15 appear as the character 342434, `*'
(note that this is outside of the ascii range), using the default
face, i.e., the default font and color.

Eev also sets a few other glyphs with non-standard faces. The most
important of those are `«' and '»', which are set to appear in green
against the default background, with:

\begin{verbatim}
  (eev-set-glyph 171 171 'eev-glyph-face-green)
  (eev-set-glyph 187 187 'eev-glyph-face-green)
\end{verbatim}
%
There's a technical point to be raised here. Emacs can use several
``encodings'' for files and buffers, and `«' and `»' only have
character codes 171 and 187 in a few cases, mainly in the `raw-text'
encoding and in ``unibyte'' buffers; in most other encodings they have
other char codes, usually above 255, and when they have these other
codes Emacs considers that they are other characters for which no
special glyphs were set and shows them in the default face. This
visual distinction between the below-255 `«' and `»' and the other `«'
and `»'s is deliberate --- it helps preventing some subtle bugs
involving the anchor functions of section \ref{anchors}.



%%%%%
%   ___ ___  _ __ ___  _ __   ___  ___  ___ 
%  / __/ _ \| '_ ` _ \| '_ \ / _ \/ __|/ _ \
% | (_| (_) | | | | | | |_) | (_) \__ \  __/
%  \___\___/|_| |_| |_| .__/ \___/|___/\___|
%                     |_|                   
%%%%%

\section{Compose Pairs}
% «compose-pairs»  (to ".compose-pairs")

To insert a `*' in a text we type `C-q C-o' --- C-q ``quotes'' the
next key that Emacs receives, and `C-q C-o' inserts a ``literal C-o'',
which is a char 15. Typing `«' and `»'s --- and other non-standard
glyphs, if we decide to define our own --- involves using another
module of eev: eev-compose.

Eev-compose defines a few variables that hold tables of ``compose
pairs'', which map pairs of characters that are easy to type into
other, weirder characters; for example, `eev-composes-otheriso' says
that the pair \verb|"<<"| is mapped to \verb|"«"| and that \verb|">>"|
is mapped to \verb|"»"|, among others. When we are in ``eev mode'' the
prefix `\verb|M-,|' can be used to perform the translation: typing
`\verb|M-, < <|' enters `\verb|«|', and typing `\verb|M-, > >|' enters
`\verb|»|'.

The variable `eev-composes-accents' holds mappings for accented chars,
like \verb|"'a"| to \verb|"á"| and \verb|"cc"| to \verb|"ç"|;
`eev-composes-otheriso' takes care of the other mappings that still
concern characters found in the ISO8859-1 character set, like `«' and
'»' as above, \verb|"_a"| to \verb|"ª"|, \verb|"xx"| to \verb|"×"|,
and a few others; `eev-composes-globalmath' and
`eev-composes-localmath' are initially empty and are meant to be used
for used-defined glyphs. The suffix `math' in their names is a relic:
Emacs implements its own ways to enter special characters, which
support several languages and character encodings, but their code is
quite complex and they are difficult to extend; the code that
implements eev's `\verb|M-,|', on the other hand, takes about just 10
lines of Lisp (excluding the tables of compose pairs) and it is
trivial to understand and to change its tables of pairs. `\verb|M-,|'
was created originally to enter special glyphs for editing
mathematical texts in \TeX, but it turned out to be a convenient hack,
and it stuck.




%%%%%  _      _ _           _ _           _                  _                 
%   __| | ___| (_)_ __ ___ (_) |_ ___  __| |  _ __ ___  __ _(_) ___  _ __  ___ 
%  / _` |/ _ \ | | '_ ` _ \| | __/ _ \/ _` | | '__/ _ \/ _` | |/ _ \| '_ \/ __|
% | (_| |  __/ | | | | | | | | ||  __/ (_| | | | |  __/ (_| | | (_) | | | \__ \
%  \__,_|\___|_|_|_| |_| |_|_|\__\___|\__,_| |_|  \___|\__, |_|\___/|_| |_|___/
%                                                      |___/                   
%%%%%

\section{Delimited regions}
\label{bounded}
% «delimited-regions»  (to ".delimited-regions")

Sometimes it happens that we need to run a certain (long) series of
commands over and over again, maybe with some changes from one run to
the next; then having to mark the block all the time becomes a hassle.

One alternative to that is using a variaton on `M-x eev': `M-x
eev-bounded'. It saves the region around the cursor up to certain
delimiters instead of saving what's between Emacs's ``point'' and
``mark''.

The original definition of eev-bounded was something like this:

\begin{verbatim}
  (defun eev-bounded ()
    (interactive)
    (eev (ee-search-backwards "\n#*\n")
         (ee-search-forward   "\n#*\n")))
\end{verbatim}
%
the call to `ee-search-backwards' searches for the first occurrence of
the string \verb|"\n#*\n"| (newline, hash sign, control-O, newline)
before the cursor and returns the position after the \verb|"\n#*\n"|,
without moving the cursor; the call to ee-search-forward does
something similar with a forward search. As the arguments to `eev'
indicate the extremities of the region to be saved into the temporary
script, this saves the region between the first \verb|"\n#*\n"|
backwards from the cursor to the first \verb|"\n#*\n"| after the
cursor.

The actual definition of `eev-bounded' includes some extra code to
highlight temporarily the region that was used; see Figure
\ref{fig:F3}. Normally the highlighting lasts for less than one
second, but here we have set its duration to several seconds to
produce a more interesting screenshot.

% (find-eevex "screenshots.e" "fisl-screenshots")
% (find-es "tex" "png_screenshots")
% (find-fline "README" "ss-lua")
% (find-eimage0 "./ss-lua.png")
%
\begin{figure}[tb]
\includegraphics[scale=0.72]{ss-lua.eps}
\caption{\label{fig:F3}sending a delimited block with F3}
\end{figure}

Eev binds the key F3 to the function `eeb-default', which runs the
current ``default bounded function'' (which is set initially to `eev',
{\sl not} `eev-bounded') on the region between the current default
delimiters, using the current default ``highlight-spec''; so, instead
of typing `M-x eev-bounded' inside the region to save it we can just
type F3.

All these defaults values come from a single list, which is stored in
the variable `eeb-defaults'. The real definition of `eev-bounded' is
something like:

\begin{verbatim}
  (setq eev-bounded
    '(eev ee-delimiter-hash nil t t))

  (defun eev-bounded ()
    (interactive)
    (setq eeb-defaults eev-bounded)
    (eeb-default))
\end{verbatim}

Note that in Emacs Lisp (and in most other Lisps) each symbol has a
value as a variable that is independent from its ``value as a
function'': actually a symbol is a structure containg a name, a
``value cell'', a ``function cell'' and a few other fields. Our
definition of `eev-bounded', above, includes both a definition of the
function `eev-bounded' and a value for the variable `eev-bounded'.

Eev has an auxiliary function for defining these ``bounded
functions''; running

\begin{verbatim}
  (eeb-define 'eev-bounded 'eev 'ee-delimiter-hash nil t t)
\end{verbatim}
%
has the same effect as doing the `setq' and the `defun' above.

As for the meaning of the entries of the list `eeb-defaults', the
first one (`eev') says which function to run; the second one
(`ee-delimiter-hash') says which initial delimiter to use --- in this
case it is a symbol instead of a string, and so `eeb-default' takes
the value of the variable `ee-delimiter-hash'; the third one (nil) is
like the second one, but for the final delimiter, and when it is nil
`eeb-default' considers that the final delimiter is equal to the
initial delimiter; the fourth entry (t) means to use the standard
highlight-spec, and the fifth one (t, again) tells `eeb-default' to
make an adjustment to the highlighted region for purely aestethical
reasons: the saved region does not include the initial \verb|"\n"| in
the final delimiter, \verb|"\n#*\n"|, but the highlighting looks nicer
if it is included; without it the last highlighted line in Figure
\ref{fig:F3} would have only its first character --- an apostrophe ---
highlighted.

Eev also implements other of these ``bounded'' functions. For example,
running `M-x eelatex' on a region saves it in a temporary \LaTeX{}
file, and also saves into the temporary script file the commands to
process it with \LaTeX{}; `eelatex-bounded' is defined by

\begin{verbatim}
  (eeb-define 'eelatex-bounded 'eelatex
    'ee-delimiter-percent nil t t)
\end{verbatim}
%
where the variable `ee-delimiter-percent' holds the string
\verb|"\n%*\n"|; comments in \LaTeX{} start with percent signs, not
hash signs, and it is convenient to use delimiters that are treated as
comments.

[The block below ... tricky ... blah. How to typeset `*' in \LaTeX.
  Running eelatex-bounded changed the defaults stored in eeb-defaults,
  but ee-once blah doesn't.]

% (find-lsrcfile "base/ltmiscen.dtx" "subsection{Verbatim}")
%
\begin{verbatim}
  %*
  % (eelatex-bounded)
  % (ee-once (eelatex-bounded))
  \def\myttbox#1{%
    \setbox0=\hbox{\texttt{a}}%
    \hbox to \wd0{\hss#1\hss}%
  }
  \catcode`*=13 \def*{\myttbox{$\bullet$}}
  \begin{verb›atim}
  abcdefg
     d*fg
  \end{verb›atim}
  %*
\end{verbatim}


...for example eelatex, that saves the region (plus certain standard
header and footer lines) to a ``temporary \LaTeX{} file'' and saves
into the temporary script file the commands to make `ee' run \LaTeX{}
on that and display the result. The block below is an example of (...)

...The block below shows a typical application of eev-bounded:

% (find-es "lua5" "install-5.0.2")
% (find-es "lua5" "install-5.0.2" "Edrx's changes")
%
\begin{verbatim}
  # (code-c-d "lua5" "/tmp/usrc/lua-5.0.2/")
  # (find-lua5file "INSTALL")
  # (find-lua5file "config" "support for dynamic loading")
  # (find-lua5file "config")
  # (find-lua5file "")
  #*
  rm   -Rv ~/usrc/lua-5.0.2/
  mkdir -p ~/usrc/lua-5.0.2/
  tar   -C ~/usrc/ \
     -xvzf $S/http/www.lua.org/ftp/lua-5.0.2.tar.gz
  cd       ~/usrc/lua-5.0.2/
  cat >> config <<'---'
  LOADLIB= -DUSE_DLOPEN=1
  DLLIB= -ldl
  MYLDFLAGS= -Wl,-E
  EXTRA_LIBS= -lm -ldl
  ---
  make test  2>&1 | tee omt
  ./bin/lua -e 'print(loadlib)'
  #*
\end{verbatim}
%
in unpacks a program (the interpreter for Lua), changes its default
configuration slightly, then compiles and tests it.

[about the size: the above code is ``too small for being a script'',
and the hyperlinks are important]

\par gdb (here-documents, gcc, ee-once)
\par (alternative: here-documents, gcc, gdb, screenshot(s) for gdb)





%%%%%   _                            _     
%   ___| |__   __ _ _ __  _ __   ___| |___ 
%  / __| '_ \ / _` | '_ \| '_ \ / _ \ / __|
% | (__| | | | (_| | | | | | | |  __/ \__ \
%  \___|_| |_|\__,_|_| |_|_| |_|\___|_|___/
%                                          
%%%%%

\section{Communication channels}
\label{channels}
% «channels»  (to ".channels")

The way that we saw to send commands to a shell is in two steps: first
we use M-x eev in Emacs to ``send'' a block of commands, and then we
run `ee' at the shell to make it ``receive'' these commands. But there
is also a way to create shells that ``listen'' not only to the
keyboard for their input, but also to certain ``communication
channels''; by making Emacs send commands through these communication
channels we can skip the step of going to the shell and typing `ee'
--- the commands are received immediately.

% (find-eevex "screenshots.e" "fisl-screenshots")
% (find-eimage0 "~/FISL/ss-f9.png")
% (find-fline "ss-f9.png")
% (find-es "tex" "png_screenshots")
% (find-fline "README" "ss-f9")

\begin{figure}[tb]
\includegraphics[scale=0.72]{ss-f9.eps}
\caption{\label{fig:F9}sending commands to two xterms using F9}
\end{figure}

The screenshot at Figure \ref{fig:F9}{} shows this at work. The user
has started with the cursor at the second line from the top of the
screen in the Emacs window and then has typed F9 several times. Eev
binds F9 to a command that operates on the current line and then moves
down to the next line; if the current line starts with `*' then what
comes after the `*' is considered as Lisp code and executed
immediately, and the current line doesn't start with `*' then its
contents are sent through the default communication channel, or though
a dummy communication channel if no default was set.

The first F9 executed \texttt{(eechannel-xterm "A")}, which created an
xterm with title ``channel A'', running a shell listening on the
communication channel ``A'', and set the default channel to A; the
second F9 created another xterm, now listening to channel B, and set
the default channel to B.

The next two `F9's sent each one one line to channel B. The first line
was a shell comment (``\texttt{\#{} Listen}...''); the second one
started the program netcat, with options to make netcat ``listen to
the internet port 1234'' and dump to standard output what it receives.

The next line had just `*'; executing the rest of it as Lisp did
nothing. The following line changed the default channel to A.

In the following lines there is a small shell program that outputs
``hi'', then waits one second, then outputs ``bye'', then waits for
another second, then finishes; due to the ``\texttt{| netcat }...''
its output is redirected to the internet port 1234, and so we see it
appearing as the output of the netcat running on channel B, with all
the expected delays: one second between ``hi'' and ``bye'', and one
second after ``bye''; after that last one-second delay the netcat at
channel A finishes receiving input (because the program between
`\texttt{\{}' and `\texttt{\}}' ends) and it finishes its execution,
closing the port 1234; the netcat at B notices that the port was
closed and finishes its execution too, and both shells return to the
shell prompt.

There are also ways to send whole blocks of lines at once through
communication channels; see Section \ref{bigmodular}.



%%%%%   _                            _        ___               __  
%   ___| |__   __ _ _ __  _ __   ___| |___   / (_)_ __ ___  _ __\ \ 
%  / __| '_ \ / _` | '_ \| '_ \ / _ \ / __| | || | '_ ` _ \| '_ \| |
% | (__| | | | (_| | | | | | | |  __/ \__ \ | || | | | | | | |_) | |
%  \___|_| |_|\__,_|_| |_|_| |_|\___|_|___/ | ||_|_| |_| |_| .__/| |
%                                            \_\           |_|  /_/ 
%%%%%

\subsection{The Implementation of Communication Channels}
% «channels-implementation»  (to ".channels-implementation")

Communication channels are implemented using an auxiliary script
called `eegchannel', which is written in Expect ([L90] and [L95]). If
we start an xterm in the default way it starts a shell (say,
/bin/bash) and interacts with it: the xterm sends to the shell as
characters the keystrokes that it receives from the window manager and
treats the characters that the shell sends back as being instructions
to draw characters, numbers and symbols on the screen. But when we run
\texttt{(eechannel-xterm "A")} Emacs creates an xterm that interacts
with another program --- eegchannel --- instead of with a shell, and
eegchannel in its turn runs a shell and interacts with it.

Eegchannel passes characters back and forth between the xterm and the
shell without changing them in any way; it mostly tries to pretend
that it is not there and that the xterm is communicating directly with
the shell. However, when eegchannel receives a certain signal it sends
to the shell a certain sequence of characters that were not sent by
the xterm; it ``fakes a sequence of keystrokes''.

Let's see a concrete example. Suppose than Emacs was running with
process id (``pid'') 1000, and running \texttt{(eechannel-xterm "A")}
in it made it create an xterm, which got pid 1001; that xterm ran
eegchannel (pid 1002), which ran /bin/bash (pid 1003). Actually Emacs
invoked xterm using this command line:

\begin{verbatim}
  xterm -n "channel A" -e eegchannel A /bin/bash
\end{verbatim}
%
and xterm invoked eegchannel with \texttt{eegchannel A /bin/bash};
eegchannel saw the `A', saved its pid (1002) to the file
\~{}/.eev/eeg.A.pid, and watched for SIGUSR1 signals; every time that
it (the eegchannel) receives a SIGUSR1 it reads the contents of
\~{}/.eev/eeg.A.str and sends that as fake input to the shell that it
is controlling. So, running

\begin{verbatim}
  echo 'echo $[1+2]' > ~/.eev/eeg.A.str
  kill -USR1 $(cat ~/.eev/eeg.A.pid)
\end{verbatim}
%
in a shell sends the string ``\texttt{echo \$[1+2]}'' (plus a newline)
``through the channel A''; what Emacs does when we type F9 on a line
that does not start with `*' corresponds exactly to that.

% (find-lsrcfile "moreverb/")


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%   __ _ _ __   ___| |__   ___  _ __ ___ 
%  / _` | '_ \ / __| '_ \ / _ \| '__/ __|
% | (_| | | | | (__| | | | (_) | |  \__ \
%  \__,_|_| |_|\___|_| |_|\___/|_|  |___/
%
%%%%%

\section{Anchors}
% «anchors»  (to ".anchors")
\label{anchors}

The function `to' can be used to create hyperlink to certain positions
--- called ``anchors'' --- in the current file. For example,

\begin{verbatim}
  # Index:
  # «.first_block»        (to "first_block")
  # «.second_block»       (to "second_block")

  #*
  # «first_block»  (to ".first_block")
  echo blah
  #*
  # «second_block»  (to ".second_block")
  echo blah blah
  #*
\end{verbatim}
%
What `to' does is simply to wrap its argument inside `\texttt{«}' and
`\texttt{»}' characters and then jump to the first occurrence of the
resulting string in the current file. In the (toy) example above, the
line that starts with ``\verb|# «.first_block»|'' has a link that
jumps to the line that starts with ``\verb|# «first_block»|'', which
has a link that jumps back --- the anchors and ``(to ...)''s act like
an index for that file.

The function `find-anchor' works like a `to' that first opens another
file:

\begin{verbatim}
  (find-anchor "~/.zshrc" "update-homepage")
\end{verbatim}
%
does roughly the same as:

\begin{verbatim}
  (find-fline "~/.zshrc" "«update-homepage»")
\end{verbatim}

Actually `find-anchor' consults a variable, `ee-anchor-format', to see
in which strings to wrap the argument. Some functions modify
`ee-anchor-format' temporarily to obtain special effects; for example,
a lot of information about the packages installed in a Debian GNU
system is kept in a text file called /var/lib/dpkg/info/status;
\verb|(find-status "emacs21")| opens this file and searches for the
string \verb|"\nPackage: emacs21\n"| there --- that string is the
header for the block with information about the package emacs21, and
it tells the size of the package, description, version, whether it is
installed or not, etc, in a format that is both machine-readable and
human-readable.





%%%%%                       _       _       
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%  / _ \_____/ __|/ __| '__| | '_ \| __/ __|
% |  __/_____\__ \ (__| |  | | |_) | |_\__ \
%  \___|     |___/\___|_|  |_| .__/ \__|___/
%                            |_|            
%%%%%

\section{E-scripts}
% «e-scripts»  (to ".e-scripts")
\label{e-scripts}

The best short definition for eev that I've found involves some
cheating, as it is a circular definition: ``eev is a library that adds
support for e-scripts to Emacs'' --- and e-scripts are files that
contain chunks meant to be processed by eev's functions. Almost any
file can contain parts ``meant for eev'': for example, a HOWTO or
README file about some program will usually contain some example shell
commands, and we can mark these commands and execute them with M-x
eev; and if we have the habit of using eev and we are writing code in,
say, C or Lua we will often put elisp hyperlinks inside comment blocks
in our code. These two specific languages (and a few others) have a
feature that is quite convenient for eev: they have syntactical
constructs that allow comment blocks spanning several lines --- for
example, in Lua, where these comment blocks are delimited by
``\texttt{--[[}'' and ``\texttt{--]]}''s, we can have a block like

\begin{verbatim}
  --[[
  #*
  # This file: (find-fline "~/LUA/lstoindexhtml.lua")
  # A test:
  cd /tmp/
  ls -laF | col -x \
    | lua50 ~/LUA/lstoindexhtml.lua tmp/ \
    | lua50 -e 'writefile("index.html", io.read("*a"))'
  #*
  --]]
\end{verbatim}
%
in a Lua script, and the script will be at the same time a Lua script
and an e-script.

When I started using GNU and Emacs the notion of an e-script was
something quite precise to me: I was keeping notes on what I was
learning and on all that I was trying to do, and I was keeping those
notes in a format that was partly English (or Portuguese), partly
executable things --- not all of them finished, or working --- after
all, it was much more practical to write

\begin{verbatim}
  rm -Rv ~/usrc/busybox-1.00/
  tar -C ~/usrc/ -xvzf \
    $S/http/www.busybox.net/downloads/busybox-1.00.tar.gz
  cd ~/usrc/busybox-1.00/
  cp -iv ~/BUSYBOX/myconfig .config
  make menuconfig
  make       2>&1 | tee om
\end{verbatim}
%
than to write

\begin{verbatim}
  Unpack BusyBox's source, then run "make menuconfig"
  and "make" on its main directory
\end{verbatim}
%
and then have to translate that from English into machine commands
every time... So, those files where I was keeping my notes contained
``executable notes'', or were ``scripts for Emacs'', and I was quite
sure that everyone else around were also keeping notes in executable
formats, possibly using other editors and environments (vi, maybe?)
and that if I showed these people my notes and they were about some
task that they were also struggling with then they would also show me
{\sl their} notes... I ended up making a system that uploaded
regularly all my e-scripts (no matter how messy they were) to my home
page, and writing a text --- ``The Eev Manifesto'' ([O99]) --- about
sharing these executable notes.

Actually trying to define an e-script as being ``a file containing
executable parts, that are picked up and executed interactively''
makes the concept of an e-script {\sl very} loose.

% (...) Thus e-scriptness lies in the eye of the beholder: most
% languages have a syntax that allows inclusion of Lisp one-liners in
% comments --- SmallTalk is an example of a language that does {\sl
% not} allow that, as it uses `\texttt{"}'s to mark the beginning and
% the end of comments --- and many languages have a syntax for
% ``comment blocks'': the following code

Note that we {\sl can} execute the Lua parts in the code above by
running the Lua interpreter on it, we {\sl can} execute the elisp
one-liner with M-e in Emacs, and we {\sl can} execute the shell
commands using F3 or M-x eev; but the code will do nothing by itself
--- it is passive.

A piece of code containing instructions in English on how to use it is
also an e-script, in a sense; but to execute these instructions we
need to invoke an external entity --- a human, usually ourselves ---
to interpret them. This is much more flexible, but also much more
error-prone and slow, than just pressing a simple sequence of keys
like M-e, or F9, or F3, alt-tab, e, e, enter.




%%%%%        _ _ _                     
%  ___ _ __ | (_) |_    ___  _____   __
% / __| '_ \| | | __|  / _ \/ _ \ \ / /
% \__ \ |_) | | | |_  |  __/  __/\ V / 
% |___/ .__/|_|_|\__|  \___|\___| \_/  
%     |_|                              
%%%%%

\section{Splitting eev.el}
% «splitting-eev.el»  (to ".splitting-eev.el")

When I first submittted eev for inclusion in GNU Emacs, in 1999, the
people at the FSF requested some changes. One of them was to split
eev.el --- the code at that point was all in a single Emacs Lisp file,
called eev.el --- into several separate source files according to
functionality; at least the code for saving temporary scripts and the
code for hyperlinks should be kept separate.

It turned out that that was the wrong way of splitting eev. The
frontier between what is a hyperlink and what is a block of commands
is blurry:

\begin{verbatim}
  man foo
  man -P 'less +/bar' foo
  # (eev "man foo")
  # (eev "man -P 'less +/bar' foo")
  # (find-man "foo" "bar")
\end{verbatim}

The two `man' commands above can be considered as hyperlinks to a
manpage, but we need to send those commands to a shell to actually
open the manpage; the option -P 'less +/bar' instructs `man' to use
the program `less' to display the manpage, and it tells `less' to jump
to the first occurrence of the string ``bar'' in the text, and so it
is a hyperlink to a specific position in a manpage. Each of the two
`eev' lines, when executed, saves one of these `man' commands to the
temporary script file; because they contain Lisp expressions they look
much more like hyperlinks than the `man' lines. The last line,
`find-man', behaves much more like a ``real'' hyperlink: it opens the
manpage {\sl inside Emacs} and searches for the first occurrence of
`bar' there; but Emacs's code for displaying manpages was tricky, and
it took me a few years to figure out how to add support for
pos-spec-lists to it...

So, what happens is that often a new kind of hyperlink will begin its
life as a series of shell commands (another example: using `gv --page
14 file.ps' to open a PostScript file and then jump to a certain page)
and then it takes some time to make a nice hyperlink function that
does the same thing; and often these functions are implemented by
executing commands in external programs.

There's a much better way to split conceptually what eev does, though.
Most functions in eev take a region of text (for example Emacs's own
``selected region'', or the extent of Lisp expression coming before
the cursor) and ``execute'' that in some way; the kinds of regions are

\begin{tabular}{|p{12em}|p{12em}|}
\hline
Emacs's (selected) region   & M-x eev, M-x eelatex \hfill (sec.\ \ref{eev})\\
\hline
last-sexp (Lisp expression at the left of the cursor)
                            & C-x C-e, M-E \hfill (sec.\ \ref{C-xC-e}) \\
\hline
sexp-eol (go to end of line, then last-sexp)
                            & C-e C-x C-e, M-e \hfill (sec.\ \ref{M-e}) \\
\hline
bounded region & F3, M-x eev-bounded,
                 M-x eelatex-bounded \hfill (sec.\ \ref{bounded}) \\
\hline
bounded region around {\sl anchor} &  (ee-at ``{\sl anchor}'' ...)
                                      \hfill (sec.\ \ref{ee-at}) \\
\hline
current line  & F9 \hfill (sec.\ \ref{channels}) \\
\hline
no text (instead use the next item in a list)
              & F12 \hfill (sec.\ \ref{steps}) \\
\hline
\end{tabular}

Actions (can be composed):

\begin{itemize}
\item Saving a region or a string into a file
\item Sending a signal to a process
\item Executing as Lisp
\item Executing immediately in a shell
\item Start a debugger
\end{itemize}

[Emacs terminology: commands]



%%%%%             _                 
%   ___  ___  ___| |_ ___ _ __  ___ 
%  / _ \/ _ \/ __| __/ _ \ '_ \/ __|
% |  __/  __/\__ \ ||  __/ |_) \__ \
%  \___|\___||___/\__\___| .__/|___/
%                        |_|        
%%%%%

\section{Steps}
\label{steps}
% «eesteps»  (to ".eesteps")

[Simple examples]

[writing demos]

[hyperlinks for which no short form is known]

[producing animations and screenshots]


%%%%%
%  _     _                                  _       _       
% | |__ (_) __ _    ___       ___  ___ _ __(_)_ __ | |_ ___ 
% | '_ \| |/ _` |  / _ \_____/ __|/ __| '__| | '_ \| __/ __|
% | |_) | | (_| | |  __/_____\__ \ (__| |  | | |_) | |_\__ \
% |_.__/|_|\__, |  \___|     |___/\___|_|  |_| .__/ \__|___/
%          |___/                             |_|            
%%%%%

\section{Big Modular E-scripts}
\label{bigmodular}
\label{ee-at}
% «big-modular-e-scripts»  (to ".big-modular-e-scripts")

% (find-eevex "screenshots.e" "fisl-screenshots-modular")
% (find-eimage0 "./ss-modular.png")
% (find-fline     "ss-modular.png")
% (find-es "tex" "png_screenshots")
% (find-fline "README" "ss-modular")


A shell can be run in two modes: either interactively, by
expecting lines from the user and executing them as soon as they
are received\footnote{except for multi-line commands.}, or by
scripts: in the later case the shell already has access to the
commands, and executes them in sequence as fast as possible, with
no pause between one command and the next.

When we are sending lines to a shell with F9 we are telling it not
only {\sl what} to execute but also {\sl when} to execute it; this is
somewhat similar to running a program step-by-step inside a debugger
--- but note that most shells provide no single-stepping facilities.

We will start with a toy example --- actually the example from Section
\ref{anchors} with five new lines added at the end --- and then in the
next section we will see a real-world example that uses these ideas.

\begin{figure}[tb]
\includegraphics[scale=0.72]{ss-modular.eps}
\caption{\label{fig:modular}sending a block at once
  with eevnow-at}
\bigskip
\includegraphics[scale=1.80]{ss-gdbwide.eps}
\caption{\label{fig:gdb}single-stepping through a C program}
\end{figure}

[Somewhere between a script and direct user interaction]

[No loops, no conditionals]

[Several xterms]



%%%%%
%  _     _    _     _ _       
% (_)___| | _(_) __| (_)_ __  
% | / __| |/ / |/ _` | | '_ \ 
% | \__ \   <| | (_| | | |_) |
% |_|___/_|\_\_|\__,_|_| .__/ 
%                      |_|    
%%%%%

\section{Internet Skills for Disconnected People}
\label{iskidip}
% «iskidip»  (to ".iskidip")

Suppose that we have a person $P$ who has learned how to use a
computer and now wants to learn how the internet works. That person
$P$ knows a bit of programming and can use Emacs, and sure she can use
e-mail clients and web browsers by clicking around with the mouse, but
she has grown tired of just using those things as black boxes; now she
wants to experiment with setting up HTTP and mail servers, to
understand how data packets are driven around, how firewalls can block
some connections, such things.

The problem is that $P$ has never had access to any machine besides
her own, which is connected to the internet only through a modem; and
also, she doesn't have any friends who are computer technicians or
sysadmins, because from the little contact that she's had with these
people she's got the impression that they live lifes that are almost
as grey as the ones of factory workers, and she's afraid of them. To
add up to all that, $P$ has some hippie job that makes her happy but
poor, so she's not going to buy a second computer, and the books she
can borrow, for example, Richard Stevens' series on TCP/IP
programming, just don't cut.

One of eev's intents isto make life easier for autodidacts. Can it be
used to rescue people in positions like $P$'s\footnote{by the way, I
  created $P$ inspired on myself; my hippie job is being a
  mathematician.}? It was thinking on that that I created a
side-project to eev called ``Internet Skills for Disconnected
People'': it consists of e-scripts about running a second machine,
called the ``guest'', emulated inside the ``host'', and making the two
talk to each other via standard internet protocols, via emulated
ethernet cards. Those e-scripts make heavy use of the concepts in the
last section [...]

% (find-fline "")
% (find-eimage0 "./iskidip.png")
%
\begin{figure}[tb]
\centerline{\includegraphics[scale=1.00]{iskidip.eps}}
\caption{\label{fig:callmap}A call map}
\end{figure}

% (find-eevex "busybox.e" "bb_chroot_main")
% (find-eevex "busybox.e" "bbinitrd-qemu-main")
% (find-eevex "busybox.e" "iso-qemu-main")
% (find-eevex "busybox.e" "iso-qemu-main-2")




%%%%%%              _ _       _     _ _ _ _         
%   __ ___   ____ _(_) | __ _| |__ (_) (_) |_ _   _ 
%  / _` \ \ / / _` | | |/ _` | '_ \| | | | __| | | |
% | (_| |\ V / (_| | | | (_| | |_) | | | | |_| |_| |
%  \__,_| \_/ \__,_|_|_|\__,_|_.__/|_|_|_|\__|\__, |
%                                             |___/ 
%%%%%

\section{Availability and Resources}
% «availability»  (to ".availability")

Eev can be downloaded from the author's homepage,
http://angg.twu.net/. That page also contains lots of examples, some
animations showing some of eev's features at work, a mailing list,
etc.

Eev is in the middle of the process of becoming a standard part of GNU
Emacs; I expect it to be integrated just after the release of GNU
Emacs 22.1 in mid-2005. Eev's copyright has already been transferred
to the FSF; it is distributed under the GPL license.




% \section{Conceptual issues}

% \subsection{Actions and code}
%   actions in a shell are easy to record
%   actions in Emacs: view-lossage, tracing lisp
%   if we want to automate actions in a GUI...
%   actions in GUIs need a lot of hacking:
%     recompiling, tracing, patching.

% \subsection{The Scientific Method}
% \par Reproducibility
% \par Modifiability
% \par   Experiments
% \par Permanence
% \par   versions change
% \par   single-stepping
% \par   examining the commands: man, finding progs, updating options

% \subsection{Sharing e-scripts}
% \par   "I do not want to share my e-scripts"
% \par   That's fair enough, but I'm sharing mine.
% \par   It took me a while to realize that that wasn't so dangerous.
% \par   It required a bit of discipline, though.
% \par   I would have liked to see the scripts of my favourite hackers.
% \par   Think the other way: it can become easier to learn things if
% \par   other people share their e-scripts...
% \par   Use other people's e-scripts. Convince other people to share.
% \par   Maybe some programs or (maga)zines can come with bundled e-scripts.

% \subsection{Point to the primary sources}
% \par   Documents, source code
% \par   no time wasted rephrasing
% \par   things are in their own context
% \par   very well written, we can learn a lot from that
% \par   point to strcpy
% \par   point to pipe

% \subsection{Relevance to Free Software}
% \par   people mistify programmers
% \par   people think that code is to be read like a book
% \par   it was hard to get something that runs
% \par   dialogs involve snippets (impact on the lurkers)
% \par   a car whose hood is not locked
% \par   the best things in life are free
% \par   programming is not for geniuses: if a problem is hard, simplify it!
% \par   this is how we think, this is how we structure our ideas.
% \par   oral culture for lurkers
% \par   do it yourself (like us)

% in an interview someone said "it was very hard, it took us 20 of the
% best programmers in the world working for one month, and it costed
% us one million dollars." this is very frustrating, and it's winners
% stuff. compare with messages in a mailing list.



%%%%%
%  _   _                 _
% | |_| |__   __ _ _ __ | | _____
% | __| '_ \ / _` | '_ \| |/ / __|
% | |_| | | | (_| | | | |   <\__ \
%  \__|_| |_|\__,_|_| |_|_|\_\___/
%
%%%%%

\section{Acknowledgments}

I'd like to thank David O'Toole, Diogo Leal and Leslie Watter for our
countless hours of discussions about eev; many of the recent features
of eev --- almost half of this article --- were conceived at our
talks.

[Thank also the people at \#emacs, for help with the code and for
  small revision tips]




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% | '__/ _ \ |_ / _ \ '__/ _ \ '_ \ / __/ _ \/ __|
% | | |  __/  _|  __/ | |  __/ | | | (_|  __/\__ \
% |_|  \___|_|  \___|_|  \___|_| |_|\___\___||___/
% 
%%%%%

\section{References}

[L90] - Libes, D. {\sl Expect: Curing Those Uncontrollable Fits of
Interaction}. 1990. Available online from http://expect.nist.gov/ .

[L95] - Libes, D. {\sl Exploring Expect}. O'Reilly, 1995.

[O99] - Ochs, E. {\sl The Eev Manifesto}.
http://angg.twu.net/eev-manifesto.html

[S79] - Stallman, R. {\sl EMACS: The Extensible, Customizable Display
  Editor.} http://www.gnu.org/software/emacs/emacs-paper.html

\end{document}


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