From 286c073eec3ec0672719f628865523af803d5063 Mon Sep 17 00:00:00 2001 From: Alan Hicks Date: Sat, 15 Sep 2012 13:28:48 -0400 Subject: All new Chapter 13 courtesy of Andrew Psaltis. This chapter needs some work proofreading and editing. --- chapter_13.xml | 865 +++++++++++++++++++++++++++------------------------------ 1 file changed, 409 insertions(+), 456 deletions(-) diff --git a/chapter_13.xml b/chapter_13.xml index 771cb85..fe3305f 100644 --- a/chapter_13.xml +++ b/chapter_13.xml @@ -2,460 +2,413 @@ - -Emacs - - -While vi (with its clones) is without a -doubt the most ubiquitous -editor on Unix-like systems, emacs(1) comes -in a good second. Instead of -using different "modes", like vi does, it uses CTRL and ALT key -combinations to enter commands, in much the same way that you can use -CTRL and ALT 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, emacs -uses different keys and actually a somewhat different mechanism for -this.) - - - -Also unlike vi, which is an (excellent) editor and nothing more, emacs -is a program with near endless capabilities. emacs 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 emacs, and in fact write completely new programs "in emacs". - - - -As a result, emacs is not just an editor anymore. There are many add-on -packages for emacs 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 emacs' basic task, but it doesn't stop -there. There are for example several spreadsheet programs for emacs, -there are databases, games, mail and news clients (the top one being -Gnus), etc. - - - -There are two main versions of emacs: 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 emacs and XEmacs run on the -console as well as under X. XEmacs was once started as a project to -tidy up the emacs 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 emacs or XEmacs, the differences between them are not relevant -to the normal user. - - -
-Starting Emacs - - -Emacs can be started from the shell by simply typing emacs. When you -are running X, emacs 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, emacs will first show a welcome -message, and then after a few seconds will drop you in the *scratch* -buffer. (See Section 17.2.) - - - -You can also start emacs on an existing file by typing - - - - % emacs - /etc/resolv.conf - - - - -This will cause emacs to load the specified file when it starts up, -skipping the welcome message. - - -
-Command Keys - -As mentioned above, emacs uses CTRL and ALT combinations for -commands. The usual convention is to write these with C-letter and -M-letter, respectively. So C-x means CTRL+x, and M-x means ALT+x. - - - - - The letter M is used instead of A because originally the key was not -the ALT key but the Meta key. The Meta key has all but disappeared from -computer keyboards, and in emacs the ALT key has taken over its -function. - - - - -Many emacs commands consist of sequences of keys and key combinations. -For example, C-x C-c (that is CTRL-x followed by CTRL-c) quits -Emacs, C-x C-s saves the current file. Keep in mind that C-x C-b is not -the same as C-x b. The former means CTRL-x followed by CTRL-b, -while the latter means CTRL-x followed by just 'b'. - - -
- -
- -
-Buffers - -In emacs, the concept of 'buffers' is essential. Every file that you -open is loaded into its own buffer. Furthermore, emacs 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 emacs 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 emacs 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 emacs window, below the -status bar for the current buffer. The minibuffer is where emacs 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, emacs will ask for its name in the minibuffer. - - -Switching from one buffer to another can be done with the command C-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; emacs will then complete the name of the buffer. Tab -completion works everywhere in emacs where it makes sense. - - -You can get a list of open buffers by hitting C-x C-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 emacs). You can get rid of this split screen by -typing C-x 1. - -
- -
-Modes - -Every buffer in emacs 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 M-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.) - - -
-Opening Files - - -To open a file in emacs, type C-x C-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, emacs will open the file in a -new buffer and display that buffer on the screen. - - - - - 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 emacs, - 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 - C-x C-f and typing a filename, - just as if you were opening an existing - file. Emacs 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 C-x C-f and then enter a directory name instead of a -filename, emacs 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 -emacs will open it. - - - - - There are in fact a lot more actions you can perform here, such as - deleting, renaming and moving files, - and so on. This is the dired-mode of emacs, which - is basically a simple file manager. - - - - -When you have typed C-x C-f and suddenly change your mind, you can type -C-g to cancel the action. C-g works almost everywhere where you want to -cancel an action or command that you've started but don't want to -finish. - -
- -
- -
-Basic Editing - - -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 CTRL and Meta (ALT) 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. - - - -Basic <application>emacs</application> Editing Commands - - - - Command - Result - - - - - C-b - go one character back - - - C-f - go one character forward - - - C-n - go one line down - - - C-p - go one line up - - - C-a - go to the beginning of the line - - - C-e - go to the end of the line - - - M-b - go one word back - - - M-f - go one word forward - - - M-} - go one paragraph forward - - - M-{ - go one paragraph backward - - - M-a - go one sentence backward - - - M-e - go one sentence forward - - - C-d - delete the character under the cursor - - - M-d - delete until the end of the current word - - - C-v - go down one screen (i.e., - PgDn) - - - M-v - go up one screen (i.e., - PgUp) - - - M-< - go to the beginning of the buffer - - - M-> - go to the end of the buffer - - - C-_ - undo the last change (can be repeated); note - that you actually have to type - SHIFT+CTRL+hyphen for this. - - - - C-k - delete to end of line - - - C-s - forward search - - - C-r - reverse search - - - -
- - -Note that many Meta commands are parallel to the CTRL commands -except that they operate on larger units: while C-f goes forward one -character, M-f goes forward an entire word, etc. - - - -Also note that M-< and M-> require you to type SHIFT+ALT+comma and -SHIFT+ALT+dot respectively, since -< and > are on SHIFT+comma and -SHIFT+dot. (Unless of course you have a different keyboard layout from -the standard US layout.) - - - -Note that C-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 C-k twice: once to delete the text on the line, -and once to delete the line itself. - - -
- -
-Saving Files - - -In order to save a file, you type C-x C-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 - -C-x C-w - - - -When you save the file for the first time in this session, emacs 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, emacs will create a backup cars.txt~. - - - -This backup file is a copy of the file that you opened. While you are -working, emacs 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 C-x C-s. - - - -When you are done editing a file, you can kill the buffer that holds it -by typing C-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, emacs will ask you if you really want to -kill the buffer. - - - - If you'd prefer to save the file with a new name so that you - don't overwrite the original version, use C-x - C-w instead. You may then give a new name for the - file, and the buffer will be updated to reflect the contents of this - new file, leaving the old file unchanged. - - -
- -
-Quitting Emacs - - -When you are done with emacs altogether, -you can type C-x C-c - - - -This quits emacs. If you have any unsaved files, emacs will tell you -so, and ask if you want to save them each in turn. If you answer no to -any of these, emacs will ask for one final confirmation and then quit. - - -
- + + <application>Emacs</application> + +
+ What is <application>Emacs</application>? + + + vi and its clones are very functional + and powerful editors. However, they are often considered not + particularly extensible. vim is a + successful and powerful + vi variant that shrugs this trend, + being both extremely extensible and lightweight. However, many + users prefer a more "heavy" and extensible editor. This is why + many people (including the author of this chapter) prefer + Emacs. + + + + Emacs takes extensibility up to eleven. Outside of a core of C, + the rest of Emacs is written in a + Lisp variant, nearly all of which is exposed to you, so that you + may configure it or even extend it at will (many good Emacs Lisp + tutorials can be found on the Internet). People have written + all sorts of extensions in Emacs Lisp, from syntax highlighting + for an obscure language, to a built-in terminal. In fact, + there's even a vi emulation mode + within Emacs (called viper), so you + can still get the modal editing that comes with vi, while having + access to the power of the Emacs + core. + + + + Like vi, there are many variants of + Emacs (termed "emacsen"). However, + the one most commonly used (and the only one in Slackware) is + GNU Emacs. When people reference "Emacs" directly, they almost + always mean GNU Emacs. + + + + Unlike vi, + Emacs operates more like a + traditional editor by default. This means that most keyboard + shortcuts can be performed without repeatedly changing modes. + You can open up a file and start typing away without having to + learn what the modes do, or forgetting which one you are + currently using. + +
+ +
+ Starting Out + + Emacs can be started simply by + running the emacs command in your + terminal. When + you first start it in a console without arguments, you will see + something that resembles this: + + + + + + If you are in X windows, Emacs may + start a GUI instead of running in your console. If this is the + case and you don't want a GUI, you can invoke it with the flag + '-nw'. + + + + While here, you can browse around using the + keyboard arrow keys. + Underlined elements are links, and you can activate them by + moving over them and pressing 'enter'. The documentation + mentioned is very good, and can help you get your bearings + should you have any problems. Also note how they describe key + sequences such as C-h, meaning press the + h + key while holding down the CTRL key. Same deal + with M-`, meaning to hold the the + Meta key (usually "Alt") and + press the backtick "`" key. When they say (e.g.) C-x + C-c, this means to press the "x" key while holding down + the CTRL key, then press the "x" key while also + holding down the CTRL key. Conveniently, this + is also one of the more important commands in + Emacs: to close it. + + + + Alternatively, if you call emacs with a + file name as an argument, it will open that file, just like + vi. Upon doing this, you will be + presented with the contents of the file in question. Here, you can + navigate the document using traditional arrow keys and type in + information at will without any issues. + + + + Say you make some edits, and you now want to save your file. + The following key sequence will do that: C-x C-s. + If you made a new file, you will be prompted for this in what is + called the "minibuffer", the blank line below the gray line at + the bottom of the screen. Type in the file name of your choice, + then hit Enter. If you don't want to + save the file, you can press C-g, which aborts + operations that ask for input. Do note that tab-completion is + usually available for operations that use the minibuffer. + + + + Should you want to open a new file within your same + Emacs session, type in C-x + C-f. You will be prompted for a file name in the + minibuffer. Emacs doesn't care + whether it exists or not. If it doesn't exist, a new buffer + will be created for it (the file will be created upon saving + with C-x C-s), or it will be opened as + expected. However, the old file will still be open! You can + switch back to it using C-x C-b, entering in + the file's name (or more technically, the buffer's name), then + hitting Enter. + + +
+ +
+ How to Move Around + + Like vi, + Emacs is also older than the arrow + keys on your keyboard. Also, like in + vi, using the arrow keys to navigate + files is also supported. While the + vi movement keys are more ergonomic, + emacs's are more "mnemonic". + However, it is still very possible to operate using the main + Emacs keybindings quickly and + efficiently. Here is a table of the basic movement keybindings: + + + + Emacs Cursor Movement + + + + Command + Result + + + + + C-f + Move the cursor one character to the right (forward) + + + C-b + Move the cursor one character to the left (backward) + + + C-n + Move the cursor one line down (next) + + + C-p + Move the cursor one line up (previous) + + + +
+ + + Of course, like with vi it is also + possible to repeat these commands with a numeric argument. If you + type in M-1 M-0 C-p, or C-u 10 + C-p, the cursor will move ten lines up. If you type in + M-5 C-f or C-u 5 C-f, the cursor + will move five characters to the right. + +
+ +
+ Getting Help + + + Emacs contains a great deal of + documentation, to the point that it is often called a + "self-documenting" editor. This is because it provides + mechanisms for providing users with documentation while you are + using it. + + Here are some useful functions that display documentation (they + all start with C-h): + + + + Accessing <application>Emacs</application> Documentation + + + + Command + Result + + + + + C-h f FUNCTION-NAME Enter + Show documentation for function FUNCTION-NAME + + + C-h k C-x C-c + Show documentation for the function bound to the keys + C-x C-c + + + C-h t + Show the Emacs tutorial + + + C-h ? + Show all help-related functions + + + +
+ + C-h t is especially useful if + you want or need practice using Emacs. + + +
+ + +
+ Calling Functions + + As noted earlier, Emacs exports a + large number of functions to for interactive use. Some of + these, like those opening and saving files, are mapped to keys. + Others (like the ones for moving to the beginning and end of + lines) are not. To call them, you have to invoke them. Say we + want to call the function "end-of-line". We would do + this: + + + + M-x end-of-line Enter + + + + And the cursor would move to the end of the line, as the function name + suggests. + +
+ +
+ Emacs Cheat Sheet + + + While Emacs can be simple to use, its scope can easily be + overwhelming. Below are some useful Emacs commands. Some + aspects have been simplified, most notably regarding text + selection. These concepts, and more, are described the + Emacs manual, and various on-line + tutorials. Decent summaries can also be gleaned from web + searches. + + + + Emacs Cheat Sheet + + + + Command + Result + + + + + C-f + Move the cursor one character to the right (forward) + + + C-b + Move the cursor one character to the left (backward) + + + C-n + Move the cursor one line down (next) + + + C-p + Move the cursor one line up (previous) + + + C-h f FUNCTION-NAME Enter + Show documentation for function FUNCTION-NAME + + + C-h k C-x C-c + Show documentation for the function bound to the keys C-x C-c + + + C-h t + Show the Emacs tutorial + + + C-h ? + Show all help-related functions + + + M-` + Access the Menu Bar + + + C-g + Cancel the current operation. This is most useful when in the minibuffer. + + + M-x FUNCTION-NAME Enter + Call the interactive function FUNCTION-NAME + + + M-1 M-0 C-n + Move the cursor ten lines down + + + C-u 10 C-n + Move the cursor ten lines down (same as above) + + + M-x beginning-of-line + Move the cursor to the beginning of the current line + + + M-x end-of-line + Move the cursor to the end of the current line + + + M-> + Move the cursor to the end of the buffer + + + M-< + Move the cursor to the beginning of the buffer + + + C-k + Remove text from the cursor to the end of the line and + place it into the kill ring + + + C-space + Enter selection mode (use normal motion keys to move around). Press C-space again to leave it. + + + C-w + While in selection mode, delete the selected region, and store the result into the kill ring + + + M-w + While in selection mode, store the selected region into the kill ring. + + + C-y + "Yanks" the contents of the kill ring and places them at the cursor's location + + + + C-/ + Undo the previous action. Unlike most other editors, this includes previous undo actions. + + + insert + Enable or disable overwriting characters + + + C-s asdf Enter + Forward incremental search for the string "asdf". Repeat C-s as needed to search for future items, or C-r (below) to search backwards. + + + C-r asdf Enter + Backward incremental search for the string "asdf". Repeat C-r as needed to search for future items, or C-s (above) to search forwards. + + + M-% old Enter new Enter + Search for each instance of "old" and prompt you to replace it with "new". You can force replacement of all items by typing "!" at the replacement prompt. + + + C-x C-c + Exit Emacs, prompting you to save each unsaved buffer before doing so + + + C-x C-s + Save the currrent buffer to its file + + + C-x C-w new-file.txt Enter + Save the current buffer to a file "new-file.txt" + + + +
+
-- cgit v1.2.3