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diff --git a/chapter_13.xml b/chapter_13.xml index 021bcf8..2a0af86 100644 --- a/chapter_13.xml +++ b/chapter_13.xml @@ -5,8 +5,308 @@ <chapter> <title>Emacs</title> +<para> +While <application>vi</application> (with its clones) is without a +doubt the most ubiquitous +editor on Unix-like systems, <application>emacs</application>(1) comes +in a good second. Instead of +using different "modes", like <application>vi</application> does, it uses <keycap>CTRL</keycap> and <keycap>ALT</keycap> key +combinations to enter commands, in much the same way that you can use +<keycap>CTRL</keycap> and <keycap>ALT</keycap> key combinations in a word processor and indeed in +many other applications to execute certain functions. (Though it should +be noted that the commands rarely correspond; so while many modern +applications use Ctrl-C/ X/ V for copying, cutting and pasting, <application>emacs</application> +uses different keys and actually a somewhat different mechanism for +this.) +</para> + +<para> +Also unlike <application>vi</application>, which is an (excellent) editor and nothing more, <application>emacs</application> +is a program with near endless capabilities. <application>emacs</application> is (for the most +part) written in Lisp, which is a very powerful programming language +that has the peculiar property that every program written in it is +automatically a Lisp compiler of its own. This means that the user can +extend <application>emacs</application>, and in fact write completely new programs "in <application>emacs</application>". +</para> + +<para> +As a result, <application>emacs</application> is not just an editor anymore. There are many add-on +packages for <application>emacs</application> available (many come with the program's source) that +provide all sorts of functionality. Many of these are related to text +editing, which is after all <application>emacs</application>' basic task, but it doesn't stop +there. There are for example several spreadsheet programs for <application>emacs</application>, +there are databases, games, mail and news clients (the top one being +Gnus), etc. +</para> + +<para> +There are two main versions of <application>emacs</application>: GNU Emacs (which is the version +that comes with Slackware) and XEmacs. The latter is not a version for +Emacs running under X. In fact, both <application>emacs</application> and XEmacs run on the +console as well as under X. XEmacs was once started as a project to +tidy up the <application>emacs</application> code. Currently, both versions are being actively +developed, and there is in fact much interaction between the two +development teams. For the present chapter, it is immaterial whether +you use <application>emacs</application> or XEmacs, the differences between them are not relevant +to the normal user. +</para> + +<section> +<title>Starting Emacs</title> + +<para> +Emacs can be started from the shell by simply typing <application>emacs</application>. When you +are running X, <application>emacs</application> will (normally) come up with its own X window, +usually with a menu bar at the top, where you can find the most +important functions. On startup, <application>emacs</application> will first show a welcome +message, and then after a few seconds will drop you in the *scratch* +buffer. (See Section 17.2.) +</para> + +<para> +You can also start <application>emacs</application> on an existing file by typing + +% <application>emacs</application> /etc/resolv.conf + +This will cause <application>emacs</application> to load the specified file when it starts up, +skipping the welcome message. +</para> + +<section> +<title>Command Keys</title> + +As mentioned above, <application>emacs</application> uses <keycap>CTRL</keycap> and <keycap>ALT</keycap> combinations for +commands. The usual convention is to write these with <keycap>C</keycap>-letter and +<keycap>M</keycap>-letter, respectively. So <keycap>C</keycap>-x means <keycap>CTRL</keycap>+x, and <keycap>M</keycap>-x means <keycap>ALT</keycap>+x. +(The letter M is used instead of A because originally the key was not +the <keycap>ALT</keycap> key but the Meta key. The Meta key has all but disappeared from +computer keyboards, and in <application>emacs</application> the <keycap>ALT</keycap> key has taken over its +function.) + +Many <application>emacs</application> commands consist of sequences of keys and key combinations. +For example, <keycap>C</keycap>-x <keycap>C</keycap>-c (that is <keycap>CTRL</keycap>-x followed by <keycap>CTRL</keycap>-c ) quits +Emacs, <keycap>C</keycap>-x <keycap>C</keycap>-s saves the current file. Keep in mind that <keycap>C</keycap>-x <keycap>C</keycap>-b is not +the same as <keycap>C</keycap>-x b. The former means <keycap>CTRL</keycap>-x followed by <keycap>CTRL</keycap>-b, +while the latter means <keycap>CTRL</keycap>-x followed by just 'b'. + +</section> + +</section> + <section> -<title>No Idea</title> +<title>Buffers</title> + +In <application>emacs</application>, the concept of "buffers" is essential. Every file that you +open is loaded into its own buffer. Furthermore, <application>emacs</application> has several +special buffers, which do not contain a file but are used for other +things. Such special buffers usually have a name that starts and ends +with an asterisk. For example, the buffer that <application>emacs</application> shows when it is +first started, is the so-called *scratch* buffer. In the *scratch* +buffer, you can type text in the normal way, but text that is typed +there is not saved when <application>emacs</application> is closed. + +There is one other special buffer you need to know about, and that is +the minibuffer. This buffer consists of only one line, and is always on +the screen: it is the very last line of the <application>emacs</application> window, below the +status bar for the current buffer. The minibuffer is where <application>emacs</application> shows +messages for the user, and it is also the place where commands that +require some user input are executed. For example, when you open a +file, <application>emacs</application> will ask for its name in the minibuffer. + +Switching from one buffer to another can be done with the command <keycap>C</keycap>-x +b. This will prompt you for the name of a buffer (a buffer's name is +usually the name of the file you are editing in it), and it gives a +default choice, which is normally the buffer that you were in before +you switched to or created the current buffer. Just hitting Enter will +switch to that default buffer. + +If you want to switch to another buffer than the default offered by +Emacs, just type its name. Note that you can use so-called +Tab-completion here: type the first few letters of the buffer's name +and hit Tab; <application>emacs</application> will then complete the name of the buffer. Tab +completion works everywhere in <application>emacs</application> where it makes sense. + +You can get a list of open buffers by hitting <keycap>C</keycap>-x <keycap>C</keycap>-b. This command +will usually split the screen in two, displaying the buffer you were +working in in the top half, and a new buffer called *Buffer List* in +the bottom half. This buffer contains a list of all the buffers, their +sizes and modes, and the files, if any, that those buffers are visiting +(as it is called in <application>emacs</application>). You can get rid of this split screen by +typing <keycap>C</keycap>-x 1. + +</section> + +<section> +<title>Modes</title> + +Every buffer in <application>emacs</application> has an associated mode. This mode is very +different from the idea of modes in vi: a mode tells you what kind of +buffer you are in. For example, there is text-mode for normal text +files, but there are also modes such as c-mode for editing C programs, +sh-mode for editing shell scripts, latex-mode for editing LaTeX files, +mail-mode for editing email and news messages, etc. A mode provides +special customizations and functionality that is useful for the kind of +file you are editing. It is even possible for a mode to redefine keys +and key commands. For example, in Text mode, the Tab key simply jumps +to the next tab stop, but in many programming language modes, the Tab +key indents the current line according to the depth of the block that +line is in. + +The modes mentioned above are called major modes. Each buffer has +exactly one major mode. Additionally, a buffer can have one or more +minor modes. A minor mode provides additional features that may be +useful for certain editing tasks. For example, if you hit the INSERT +key, you invoke overwrite-mode, which does what you'd expect. There is +also an auto-fill-mode, which is handy in combination with text-mode or +latex-mode: it causes each line that you type to be automatically +wrapped once the line reaches a certain number of characters. Without +auto-fill-mode, you have to type <keycap>M</keycap>-q to fill out a paragraph. (Which +you can also use to reformat a paragraph after you've edited some text +in it and it is no longer nicely filled out.) + +<section> +<title>Opening Files</title> + +To open a file in <application>emacs</application>, type + +<keycap>C</keycap>-x <keycap>C</keycap>-f + +Emacs will ask you for the name of the file, filling in some default +path for you (which is usually ~/ ). After you type the filename (you +can use Tab completion) and hit ENTER , <application>emacs</application> will open the file in a +new buffer and display that buffer on the screen. +Note + +Emacs will automatically create a new buffer, it will not load the file +into the current buffer. + +In order to create a new file in <application>emacs</application>, you cannot just go typing right +away. You first have to create a buffer for it, and come up with a +filename. You do this by typing <keycap>C</keycap>-x <keycap>C</keycap>-f and typing a filename, just as +if you were opening an existing file. <application>emacs</application> will notice that the file +you typed doesn't exist, and will create a new buffer and report "(New +file)" in the minibuffer. + +When you type <keycap>C</keycap>-x <keycap>C</keycap>-f and then enter a directory name instead of a +filename, <application>emacs</application> will create a new buffer in which you will find a list +of all the files in that directory. You can move the cursor to the file +that you are looking for and type , and <application>emacs</application> will open it. (There are +in fact a lot more actions you can perform here, such as deleting, +renaming and moving files, etc. <application>emacs</application> is now in dired-mode, which is +basically a simple file manager.) + +When you have typed <keycap>C</keycap>-x <keycap>C</keycap>-f and suddenly change your mind, you can type +<keycap>C</keycap>-g to cancel the action. <keycap>C</keycap>-g works almost everywhere where you want to +cancel an action or command that you've started but don't want to +finish. + +</section> + +</section> + +<section> +<title>Basic Editing</title> + +When you have opened a file, you can of course move around in it with +the cursor. The cursor keys and PgUp, PgDn do what you'd expect. Home +and End jump to the beginning and end of the line. (In older versions, +they would actually jump to the beginning and end of the buffer.) +However, there are also <keycap>CTRL</keycap> and Meta (<keycap>ALT</keycap>) key combos that move the +cursor around. Because you do not need to move your hands to another +part of the keyboard for these, they are much quicker once you get used +to them. The most important such commands are listed in Table 17-1. + +Table 17-1. Basic <application>emacs</application> Editing Commands +Command Result +<keycap>C</keycap>-b go one character back +<keycap>C</keycap>-f go one character forward +<keycap>C</keycap>-n go one line down +<keycap>C</keycap>-p go one line up +<keycap>C</keycap>-a go to the beginning of the line +<keycap>C</keycap>-e go to the end of the line +<keycap>M</keycap>-b go one word back +<keycap>M</keycap>-f go one word forward +<keycap>M</keycap>-} go one paragraph forward +<keycap>M</keycap>-{ go one paragraph backward +<keycap>M</keycap>-a go one sentence backward +<keycap>M</keycap>-e go one sentence forward +<keycap>C</keycap>-d delete the character under the cursor +<keycap>M</keycap>-d delete until the end of the current word +<keycap>C</keycap>-v go down one screen (i.e., PgDn) +<keycap>M</keycap>-v go up one screen (i.e., PgUp) +<keycap>M</keycap>-< go to the beginning of the buffer +<keycap>M</keycap>-> go to the end of the buffer +<keycap>C</keycap>-_ undo the last change (can be repeated); note that you actually +have to type <keycap>SHIFT</keycap>+<keycap>CTRL</keycap>+hyphen for this. +<keycap>C</keycap>-k delete to end of line +<keycap>C</keycap>-s forward search +<keycap>C</keycap>-r backward search + +Note that many Meta commands are parallel to the <keycap>CTRL</keycap> commands +except that they operate on larger units: while <keycap>C</keycap>-f goes forward one +character, <keycap>M</keycap>-f goes forward an entire word, etc. + +Also note that <keycap>M</keycap>-< and <keycap>M</keycap>-> require you to type <keycap>SHIFT</keycap>+<keycap>ALT</keycap>+comma and +<keycap>SHIFT</keycap>+<keycap>ALT</keycap>+dot respectively, since +< and > are on <keycap>SHIFT</keycap>+comma and +<keycap>SHIFT</keycap>+dot. (Unless of course you have a different keyboard layout from +the standard US layout.) + +Note that <keycap>C</keycap>-k deletes (kills, as it is commonly called) all the text +after the cursor to the end of the line, but doesn't delete the line +itself (i.e., it doesn't delete the final newline). It only deletes the +line if there was no text after the cursor. In other words, in order to +delete a complete line, you have to put the cursor at the beginning of +the line, and then hit <keycap>C</keycap>-k twice: once to delete the text on the line, +once to delete the line itself. + +</section> + +<section> +<title>Saving Files</title> + +In order to save a file, you type + +<keycap>C</keycap>-x <keycap>C</keycap>-s + +Emacs will not ask you for a filename, the buffer will just be saved to +the file it was loaded from. If you want to save your text to another +file, type + +<keycap>C</keycap>-x <keycap>C</keycap>-w + +When you save the file for the first time in this session, <application>emacs</application> will +normally save the old version of your file to a backup file, which has +the same name appended with a tilde: so if you're editing a file +"cars.txt", <application>emacs</application> will create a backup "cars.txt~". + +This backup file is a copy of the file that you opened. While you are +working, <application>emacs</application> will also regularly create an auto-save copy of the work +you are doing, to a file named with hash signs: #cars.txt#. This backup +is deleted when you save the file with <keycap>C</keycap>-x <keycap>C</keycap>-s. + +When you are done editing a file, you can kill the buffer that holds it +by typing + +<keycap>C</keycap>-x k + +Emacs will then ask you which buffer you want to kill, with the current +buffer as default, which you can select by hitting ENTER. If you +haven't saved your file yet, <application>emacs</application> will ask you if you really want to +kill the buffer. + +</section> + +<section> +<title>Quitting Emacs</title> + +When you are done with <application>emacs</application> altogether, you can type + +<keycap>C</keycap>-x <keycap>C</keycap>-c + +This quits <application>emacs</application>. If you have any unsaved files, <application>emacs</application> will tell you +so, and ask if you want to save them each in turn. If you answer no to +any of these, <application>emacs</application> will ask for one final confirmation and then quit. </section> |