GNU Emacs IntroductionIn short Emacs is an extensible, customizable, self-documenting real-time display editor, which says everything and nothing. At its core it is an interpreter for Emacs Lisp, an expression-oriented language. All functions are written in this language and a user can dive into that or not, just as he wishes. If he does he will find a well-documented structure of functions he can customise and extend, which makes Emacs a flexible tool for all editing tasks. But it is not limited to that: Reading news or mail, chatting over IRC, organising tasks and projects or using it as development environment with support for external debuggers and compilers in many different languages. The original version of Emacs is nowadays called GNU Emacs as it is maintained by the GNU project, unlike some forks that appeared in the long history and some are still existant today. The most prominent is XEmacs, which is not the X version but a totally independent project. GNU Emacs has support for X and text mode itself to clarify a popular misunderstanding. By the way, the name Emacs is derived from Editor MACroS despite other rumours and interpretations. And we should an initial warning: Emacs is really old in computer terms, but still a powerful tool, and there is nothing like it out there. So prepare yourself for a completely usability experience and a lot of functionality, which might seem overwhelming at first. Try to use the subset you need and extend your knowledge as you see fit. This guide describes the basic concepts of GNU Emacs itself and the specialties for a Gentoo installation to manage it and the possibly installed extensions packets. A complete documentation is not possible and better done by the official manual (which is not complete either) and various third-party documents, see further reading suggestions at the bottom. We are sure you can use every possible task and Emacs as a search term in your favourite search engine to find a solution in this powerful beast. Most intrinsic properties described here are also valid for XEmacs (to be found as app-editors/xemacs in the repository), but in-Gentoo managment differs in some details, so do not wonder if the described behaviour does not occur with XEmacs. Pre-installation considerations So you decided to install GNU Emacs on your system. There are several choices you can make, depending on your needs: All versions of app-editors/emacs can be installed in parallel, switching is achieved by the user through the emacs Eselect module. All are officially supported, although only version 21 and above are able to handle external extionsion packages or optional Emacs support activated with USE=emacs for some packages. Please note that some packages need version 22 or higher but those cases are rare and you will note on emerge (the process will stop very early with a meaningful message). As a new major version of GNU Emacs brings a lot of changes, an upgrade should not be done automatically by the package manager just because there is a new version. Emacs 23 for example can be emerged but the active version stays 22 until the user chooses otherwise. Apart from that it comes in handy to have a small and lean Emacs (18 for example) for quick editing sessions over a remote connection at hand. There are several editors which support Emacs key bindings (so called micro-Emacsen) but don't have the full power, a list is provided by the Emacs team. Some readers might have noticed already the app-editors/emacs-cvs package which is a live version of GNU Emacs. This means you get the tip of the current development, freshly served to your computer. We spare you the glory details as you should use it only if you are curious and willing to deal with the typical breakage that appears during development. First, you must install Emacs. TODO: Be more verbose
You could unpack the Emacs sources and run ./configure --help to see the optional support. If you don't use the X or gtk flags, you will rely on the keyboard to use Emacs. Otherwise, emacs -nw is the terminal mode. All Emacs versions can be installed alongside each other on the same system without collisions. Calling /usr/bin/emacs redirects (by a symbolic link) to the Emacs version you chose to be started. Switching the default Emacs is done through the emacs eselect module, which is presented in the following example.
Initially this tool was intended as a short-term migration tool for some internal changes, but is now a mean to handle up- and downgrades of Emacs cleanly. First you need to install it.
Without any arguments /usr/sbin/emacs-updater will look for site-files (we will come of that to the exact definition later) in a obsolete location and recompile all Emacs support files of additional packages that were not built with the current active Emacs version. That way a up- or downgrade of Emacs is easily possible if the format of the compiled files is differing (which is the case between 21 and anything up). After switching the active version with the Eselect module you can run emacs-updater afterwards and will not experience strange run-time errors. An unconditional rebuild of all Emacs support files is also possible with
After installing Emacs itself we will describe some basics in editing which is quite different from anything you might know. TODO: What's a mode? Describe some concepts TODO: Describe emacs-daemon Emacs can work as a server for emacsclient. To use this type M-x server-start in a running Emacs session. Then it's emacsclient file1 file2 file3 to edit your files or mail. There is a tutorial for Emacs available.
That is Meta then x. The Meta key is escape or possibly Alt. Next you need to type help and use tab twice to see the completions. Separate package or USE=emacs?
Some types of files have modes created for them. If you edit Python or PHP code, this piece of information is for you. This is a convenient way to install elisp files (.el and byte-compiled .elc) thanks to the Emacs team! This is done as root. Note the # prompt. TODO: Describe canonical site-init loading
An introduction to Emacs would not be complete without a section on macros. This is "Editor MACroS". In a buffer, type control-x, ( to begin. Then type what you want in the macro. You are recording keystrokes. Now type control-x, ) to finish the macro. Naming the macro is next with M-x name-last-kbd-macro. You could insert-kbd-macro into a .emacs file if you find it very useful. Perhaps you want to use that macro 10 times in a row. This is awkward, but control-u, 10, M-x mymacro. You could use the lisp interpreter to make lists or do some simple math. Type these in and then type control-x, control-e with the cursor at the end of them. Watch the minibuffer at the bottom of the screen.
Understanding how to navigate the cursor over lists is quite useful. With the cursor pointed on a [, (, or {, use M-C-f to go to the end. Use M-C-b to go to the beginning of the list. That is escape, control-f and escape, control-b respectively. You could load your elisp.
Now, you may want to clean up your code or make replacements in a function. Click and drag or use control-space to set a mark.
That will toggle the highlighting of selected text. Now, M-% will prompt you to search and replace or query-replace. Also, global-font-lock-mode will toggle the syntax highlighting; indent-region will nicely indent nested code blocks or HTML. A quick comment comes from M-; or escape-semicolon. Emacs can start subprocesses, like a shell or a debugger or even find and grep.
Bash has some keystrokes in common with Emacs. You can search your shell history with control-r but not control-s. If you try control-s in bash, it will hide your typing. You can type control-q to see input to bash again. To cancel a search, type control-g. Just like Emacs, you can kill text several times with control-k and get it back with control-y. You can then use escape-y repetitions. You can suspend Emacs with control-z. Try the jobs command to see what is suspended. Then type fg or fg 1 to get back to Emacs. Delete a whole word with escape-backspace or escape-d. Undo with control-/ and transpose two mistyped characters with control-t. Now is where some completion becomes useful. There is M-/ to complete a string and also some elisp that does much more.
This has try-expand-list, try-expand-line, try-complete-file-name and many other things. It will cycle through trying to match what is immediately on the left of the cursor. It is much nicer to bind this to a key.
This could be persistent in a .emacs file.
One common thing for Gentoo users is to strip comments from configuration files. This is convenient in Emacs with flush-lines
5. Useful functions in GNU Emacs Lets start by looking at some files.
Now you have dired, the directory editor. When you press enter on directories, you traverse the file structure. It is possible to quickly back up the tree with ^, shift-6. Over the course of editing, you may open many files.
Now you may wish to do replacements in many files.
Now you see what is available. Here is one strategy.
That will split your screen and show the buffers that are open. When you want to split the screen, use control-x followed by a number.
Speedbar for Debugging and Navigation If you're coding C, and you use gcc -g for debugging symbols, Emacs can split your screen and follow the current line of source code. If you use Emacs with X try speedbar.
Now watch variables change just like any other development environment. You could also browse directories in speedbar or do other things by right-clicking. Since Gentoo respects your /etc/ configuration files, you may like ediff for file foo and ._cfg0000_foo.
TODO: Describe the settings and add the canonical loading
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