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@shorttitlepage GNU Emacs Manual
GNU Emacs Manual
Thirteenth Edition, Updated for Emacs Version 20.3
Richard Stallman Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
Thirteenth Edition
Updated for Emacs Version 20.3,
August 1998
ISBN 1-882114-06-X
Published by the Free Software Foundation
59 Temple Place, Suite 330
Boston, MA 02111-1307 USA
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English.
Cover art by Etienne Suvasa.
This manual documents the use and simple customization of the Emacs editor. The reader is not expected to be a programmer; simple customizations do not require programming skill. But the user who is not interested in customizing can ignore the scattered customization hints.
This is primarily a reference manual, but can also be used as a primer. For complete beginners, it is a good idea to start with the on-line, learn-by-doing tutorial, before reading the manual. To run the tutorial, start Emacs and type C-h t. This way you can learn Emacs by using Emacs on a specially designed file which describes commands, tells you when to try them, and then explains the results you see.
On first reading, just skim chapters 1 and 2, which describe the notational conventions of the manual and the general appearance of the Emacs display screen. Note which questions are answered in these chapters, so you can refer back later. After reading chapter 4, you should practice the commands there. The next few chapters describe fundamental techniques and concepts that are used constantly. You need to understand them thoroughly, experimenting with them if necessary.
Chapters 14 through 19 describe intermediate-level features that are useful for all kinds of editing. Chapter 20 and following chapters describe features that you may or may not want to use; read those chapters when you need them.
Read the Trouble chapter if Emacs does not seem to be working properly. It explains how to cope with some common problems (see section Dealing with Emacs Trouble), as well as when and how to report Emacs bugs (see section Reporting Bugs). To find the documentation on a particular command, look in the index. Keys (character commands) and command names have separate indexes. There is also a glossary, with a cross reference for each term.
This manual is available as a printed book and also as an Info file. The Info file is for on-line perusal with the Info program, which will be the principal way of viewing documentation on-line in the GNU system. Both the Info file and the Info program itself are distributed along with GNU Emacs. The Info file and the printed book contain substantially the same text and are generated from the same source files, which are also distributed along with GNU Emacs.
GNU Emacs is a member of the Emacs editor family. There are many Emacs editors, all sharing common principles of organization. For information on the underlying philosophy of Emacs and the lessons learned from its development, write for a copy of AI memo 519a, "Emacs, the Extensible, Customizable Self-Documenting Display Editor," to Publications Department, Artificial Intelligence Lab, 545 Tech Square, Cambridge, MA 02139, USA. At last report they charge $2.25 per copy. Another useful publication is LCS TM-165, "A Cookbook for an Emacs," by Craig Finseth, available from Publications Department, Laboratory for Computer Science, 545 Tech Square, Cambridge, MA 02139, USA. The price today is $3.
This edition of the manual is intended for use with GNU Emacs installed on GNU and Unix systems. GNU Emacs can also be used on VMS, MS-DOS (also called MS-DOG), Windows NT, and Windows 95 systems. Those systems use different file name syntax; in addition, VMS and MS-DOS do not support all GNU Emacs features. We don't try to describe VMS usage in this manual. See section Emacs and MS-DOS, for information about using Emacs on MS-DOS.
GNU Emacs is free software; this means that everyone is free to use it and free to redistribute it on certain conditions. GNU Emacs is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of GNU Emacs that they might get from you. The precise conditions are found in the GNU General Public License that comes with Emacs and also appears following this section.
One way to get a copy of GNU Emacs is from someone else who has it. You need not ask for our permission to do so, or tell any one else; just copy it. If you have access to the Internet, you can get the latest distribution version of GNU Emacs by anonymous FTP; see the file `etc/FTP' in the Emacs distribution for more information.
You may also receive GNU Emacs when you buy a computer. Computer manufacturers are free to distribute copies on the same terms that apply to everyone else. These terms require them to give you the full sources, including whatever changes they may have made, and to permit you to redistribute the GNU Emacs received from them under the usual terms of the General Public License. In other words, the program must be free for you when you get it, not just free for the manufacturer.
You can also order copies of GNU Emacs from the Free Software Foundation on CD-ROM. This is a convenient and reliable way to get a copy; it is also a good way to help fund our work. (The Foundation has always received most of its funds in this way.) An order form is included in the file `etc/ORDERS' in the Emacs distribution, and on our web site in http://www.gnu.org/order/order.html. For further information, write to
Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA USA
The income from distribution fees goes to support the foundation's purpose: the development of new free software, and improvements to our existing programs including GNU Emacs.
If you find GNU Emacs useful, please send a donation to the Free Software Foundation to support our work. Donations to the Free Software Foundation are tax deductible in the US. If you use GNU Emacs at your workplace, please suggest that the company make a donation. If company policy is unsympathetic to the idea of donating to charity, you might instead suggest ordering a CD-ROM from the Foundation occasionally, or subscribing to periodic updates.
Contributors to GNU Emacs include Per Abrahamsen, Jay K. Adams, Joe Arceneaux, Boaz Ben-Zvi, Jim Blandy, Terrence Brannon, Frank Bresz, Peter Breton, Kevin Broadey, Vincent Broman, David M. Brown, Hans Chalupsky, Bob Chassell, James Clark, Mike Clarkson, Andrew Csillag, Doug Cutting, Michael DeCorte, Gary Delp, Matthieu Devin, Eri Ding, Carsten Dominik, Scott Draves, Viktor Dukhovni, John Eaton, Rolf Ebert, Stephen Eglen, Torbj@"orn Einarsson, Tsugumoto Enami, Hans Henrik Eriksen, Michael Ernst, Ata Etemadi, Frederick Farnback, Fred Fish, Karl Fogel, Gary Foster, Noah Friedman, Keith Gabryelski, Kevin Gallagher, Kevin Gallo, Howard Gayle, Stephen Gildea, David Gillespie, Boris Goldowsky, Michelangelo Grigni, Michael Gschwind, Henry Guillaume, Doug Gwyn, Ken'ichi Handa , Chris Hanson, K. Shane Hartman, John Heidemann, Markus Heritsch, Karl Heuer, Manabu Higashida, Anders Holst, Kurt Hornik, Tom Houlder, Lars Ingebrigtsen, Andrew Innes, Michael K. Johnson, Kyle Jones, Tomoji Kagatani, Brewster Kahle, David Kaufman, Henry Kautz, Howard Kaye, Michael Kifer, Richard King, Larry K. Kolodney, Robert Krawitz, Sebastian Kremer, Geoff Kuenning, David K@aa gedal, Daniel LaLiberte, Aaron Larson, James R. Larus, Frederic Lepied, Lars Lindberg, Neil M. Mager, Ken Manheimer, Bill Mann, Brian Marick, Simon Marshall, Bengt Martensson, Charlie Martin, Thomas May, Roland McGrath, David Megginson, Wayne Mesard, Richard Mlynarik, Keith Moore, Erik Naggum, Thomas Neumann, Mike Newton, Jurgen Nickelsen, Jeff Norden, Andrew Norman, Jeff Peck, Damon Anton Permezel, Tom Perrine, Daniel Pfeiffer, Fred Pierresteguy, Christian Plaunt, Francesco A. Potorti, Michael D. Prange, Ashwin Ram, Eric S. Raymond, Paul Reilly, Edward M. Reingold, Rob Riepel, Roland B. Roberts, John Robinson, Danny Roozendaal, William Rosenblatt, Guillermo J. Rozas, Ivar Rummelhoff, Wolfgang Rupprecht, James B. Salem, Masahiko Sato, William Schelter, Ralph Schleicher, Gregor Schmid, Michael Schmidt, Ronald S. Schnell, Philippe Schnoebelen, Stephen Schoef, Randal Schwartz, Stanislav Shalunov, Mark Shapiro, Olin Shivers, Sam Shteingold, Espen Skoglund, Rick Sladkey, Lynn Slater, Chris Smith, David Smith, William Sommerfeld, Michael Staats, Ake Stenhoff, Peter Stephenson, Jonathan Stigelman, Steve Strassman, Jens T. Berger Thielemann, Spencer Thomas, Jim Thompson, Masanobu Umeda, Neil W. Van Dyke, Ulrik Vieth, Geoffrey Voelker, Johan Vromans, Barry Warsaw, Morten Welinder, Joseph Brian Wells, Ed Wilkinson, Mike Williams, Steven A. Wood, Dale R. Worley, Felix S. T. Wu, Tom Wurgler, Eli Zaretskii, Jamie Zawinski, and Neal Ziring.
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.
We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.
Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.
Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.
The precise terms and conditions for copying, distribution and modification follow.
NO WARRANTY
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found.
one line to give the program's name and an idea of what it does. Copyright (C) 19yy name of author This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. signature of Ty Coon, 1 April 1989 Ty Coon, President of Vice
This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.
You are reading about GNU Emacs, the GNU incarnation of the advanced, self-documenting, customizable, extensible real-time display editor Emacs. (The `G' in `GNU' is not silent.)
We say that Emacs is a display editor because normally the text being edited is visible on the screen and is updated automatically as you type your commands. See section The Organization of the Screen.
We call it a real-time editor because the display is updated very frequently, usually after each character or pair of characters you type. This minimizes the amount of information you must keep in your head as you edit. See section Basic Editing Commands.
We call Emacs advanced because it provides facilities that go beyond simple insertion and deletion: controlling subprocesses; automatic indentation of programs; viewing two or more files at once; editing formatted text; and dealing in terms of characters, words, lines, sentences, paragraphs, and pages, as well as expressions and comments in several different programming languages.
Self-documenting means that at any time you can type a special character, Control-h, to find out what your options are. You can also use it to find out what any command does, or to find all the commands that pertain to a topic. See section Help.
Customizable means that you can change the definitions of Emacs commands in little ways. For example, if you use a programming language in which comments start with `<**' and end with `**>', you can tell the Emacs comment manipulation commands to use those strings (see section Manipulating Comments). Another sort of customization is rearrangement of the command set. For example, if you prefer the four basic cursor motion commands (up, down, left and right) on keys in a diamond pattern on the keyboard, you can rebind the keys that way. See section Customization.
Extensible means that you can go beyond simple customization and write entirely new commands, programs in the Lisp language to be run by Emacs's own Lisp interpreter. Emacs is an "on-line extensible" system, which means that it is divided into many functions that call each other, any of which can be redefined in the middle of an editing session. Almost any part of Emacs can be replaced without making a separate copy of all of Emacs. Most of the editing commands of Emacs are written in Lisp already; the few exceptions could have been written in Lisp but are written in C for efficiency. Although only a programmer can write an extension, anybody can use it afterward. If you want to learn Emacs Lisp programming, we recommend the Introduction to Emacs Lisp by Robert J. Chassell, also published by the Free Software Foundation.
When run under the X Window System, Emacs provides its own menus and convenient bindings to mouse buttons. But Emacs can provide many of the benefits of a window system on a text-only terminal. For instance, you can look at or edit several files at once, move text between files, and edit files while running shell commands.
On a text-only terminal, the Emacs display occupies the whole screen. On the X Window System, Emacs creates its own X windows to use. We use the term frame to mean an entire text-only screen or an entire X window used by Emacs. Emacs uses both kinds of frames in the same way to display your editing. Emacs normally starts out with just one frame, but you can create additional frames if you wish. See section Frames and X Windows.
When you start Emacs, the entire frame except for the first and last lines is devoted to the text you are editing. This area is called the window. The first line is a menu bar, and the last line is a special echo area or minibuffer window where prompts appear and where you can enter responses. See below for more information about these special lines.
You can subdivide the large text window horizontally or vertically into multiple text windows, each of which can be used for a different file (see section Multiple Windows). In this manual, the word "window" always refers to the subdivisions of a frame within Emacs.
The window that the cursor is in is the selected window, in which editing takes place. Most Emacs commands implicitly apply to the text in the selected window (though mouse commands generally operate on whatever window you click them in, whether selected or not). The other windows display text for reference only, unless/until you select them. If you use multiple frames under the X Window System, then giving the input focus to a particular frame selects a window in that frame.
Each window's last line is a mode line, which describes what is going on in that window. It appears in inverse video, if the terminal supports that, and its contents begin with `--:-- *scratch*' when Emacs starts. The mode line displays status information such as what buffer is being displayed above it in the window, what major and minor modes are in use, and whether the buffer contains unsaved changes.
Within Emacs, the terminal's cursor shows the location at which editing commands will take effect. This location is called point. Many Emacs commands move point through the text, so that you can edit at different places in it. You can also place point by clicking mouse button 1.
While the cursor appears to point at a character, you should think of point as between two characters; it points before the character that appears under the cursor. For example, if your text looks like `frob' with the cursor over the `b', then point is between the `o' and the `b'. If you insert the character `!' at that position, the result is `fro!b', with point between the `!' and the `b'. Thus, the cursor remains over the `b', as before.
Sometimes people speak of "the cursor" when they mean "point," or speak of commands that move point as "cursor motion" commands.
Terminals have only one cursor, and when output is in progress it must appear where the typing is being done. This does not mean that point is moving. It is only that Emacs has no way to show you the location of point except when the terminal is idle.
If you are editing several files in Emacs, each in its own buffer, each buffer has its own point location. A buffer that is not currently displayed remembers where point is in case you display it again later.
When there are multiple windows in a frame, each window has its own point location. The cursor shows the location of point in the selected window. This also is how you can tell which window is selected. If the same buffer appears in more than one window, each window has its own position for point in that buffer.
When there are multiple frames, each frame can display one cursor. The cursor in the selected frame is solid; the cursor in other frames is a hollow box, and appears in the window that would be selected if you give the input focus to that frame.
The term `point' comes from the character `.', which was the command in TECO (the language in which the original Emacs was written) for accessing the value now called `point'.
The line at the bottom of the frame (below the mode line) is the echo area. It is used to display small amounts of text for several purposes.
Echoing means displaying the characters that you type. Outside Emacs, the operating system normally echoes all your input. Emacs handles echoing differently.
Single-character commands do not echo in Emacs, and multi-character commands echo only if you pause while typing them. As soon as you pause for more than a second in the middle of a command, Emacs echoes all the characters of the command so far. This is to prompt you for the rest of the command. Once echoing has started, the rest of the command echoes immediately as you type it. This behavior is designed to give confident users fast response, while giving hesitant users maximum feedback. You can change this behavior by setting a variable (see section Variables Controlling Display).
If a command cannot be executed, it may print an error message in the echo area. Error messages are accompanied by a beep or by flashing the screen. Also, any input you have typed ahead is thrown away when an error happens.
Some commands print informative messages in the echo area. These messages look much like error messages, but they are not announced with a beep and do not throw away input. Sometimes the message tells you what the command has done, when this is not obvious from looking at the text being edited. Sometimes the sole purpose of a command is to print a message giving you specific information--for example, C-x = prints a message describing the character position of point in the text and its current column in the window. Commands that take a long time often display messages ending in `...' while they are working, and add `done' at the end when they are finished.
Echo-area informative messages are saved in an editor buffer named `*Messages*'. (We have not explained buffers yet; see section Using Multiple Buffers, for more information about them.) If you miss a message that appears briefly on the screen, you can switch to the `*Messages*' buffer to see it again. (Successive progress messages are often collapsed into one in that buffer.)
The size of `*Messages*' is limited to a certain number of lines.
The variable message-log-max specifies how many lines. Once the
buffer has that many lines, each line added at the end deletes one line
from the beginning. See section Variables, for how to set variables such as
message-log-max.
The echo area is also used to display the minibuffer, a window that is used for reading arguments to commands, such as the name of a file to be edited. When the minibuffer is in use, the echo area begins with a prompt string that usually ends with a colon; also, the cursor appears in that line because it is the selected window. You can always get out of the minibuffer by typing C-g. See section The Minibuffer.
Each text window's last line is a mode line, which describes what is going on in that window. When there is only one text window, the mode line appears right above the echo area; it is the next-to-last line on the frame. The mode line is in inverse video if the terminal supports that, and it starts and ends with dashes.
Normally, the mode line looks like this:
-cs:ch buf (major minor)--line--pos------
This gives information about the buffer being displayed in the window: the buffer's name, what major and minor modes are in use, whether the buffer's text has been changed, and how far down the buffer you are currently looking.
ch contains two stars `**' if the text in the buffer has been edited (the buffer is "modified"), or `--' if the buffer has not been edited. For a read-only buffer, it is `%*' if the buffer is modified, and `%%' otherwise.
buf is the name of the window's buffer. In most cases this is the same as the name of a file you are editing. See section Using Multiple Buffers.
The buffer displayed in the selected window (the window that the cursor is in) is also Emacs's selected buffer, the one that editing takes place in. When we speak of what some command does to "the buffer," we are talking about the currently selected buffer.
line is `L' followed by the current line number of point. This is present when Line Number mode is enabled (which it normally is). You can optionally display the current column number too, by turning on Column Number mode (which is not enabled by default because it is somewhat slower). See section Optional Mode Line Features.
pos tells you whether there is additional text above the top of the window, or below the bottom. If your buffer is small and it is all visible in the window, pos is `All'. Otherwise, it is `Top' if you are looking at the beginning of the buffer, `Bot' if you are looking at the end of the buffer, or `nn%', where nn is the percentage of the buffer above the top of the window.
major is the name of the major mode in effect in the buffer. At any time, each buffer is in one and only one of the possible major modes. The major modes available include Fundamental mode (the least specialized), Text mode, Lisp mode, C mode, Texinfo mode, and many others. See section Major Modes, for details of how the modes differ and how to select one.
Some major modes display additional information after the major mode name. For example, Rmail buffers display the current message number and the total number of messages. Compilation buffers and Shell buffers display the status of the subprocess.
minor is a list of some of the minor modes that are turned on at the moment in the window's chosen buffer. For example, `Fill' means that Auto Fill mode is on. `Abbrev' means that Word Abbrev mode is on. `Ovwrt' means that Overwrite mode is on. See section Minor Modes, for more information. `Narrow' means that the buffer being displayed has editing restricted to only a portion of its text. This is not really a minor mode, but is like one. See section Narrowing. `Def' means that a keyboard macro is being defined. See section Keyboard Macros.
In addition, if Emacs is currently inside a recursive editing level, square brackets (`[...]') appear around the parentheses that surround the modes. If Emacs is in one recursive editing level within another, double square brackets appear, and so on. Since recursive editing levels affect Emacs globally, not just one buffer, the square brackets appear in every window's mode line or not in any of them. See section Recursive Editing Levels.
cs states the coding system used for the file you are editing. A dash indicates the default state of affairs: no code conversion, except for end-of-line translation if the file contents call for that. `=' means no conversion whatsoever. Nontrivial code conversions are represented by various letters--for example, `1' refers to ISO Latin-1. See section Coding Systems, for more information. If you are using an input method, cs starts with a string such as `i>', where i identifies the input method. (Some input methods show `+' or `@' instead of `>'.) See section Input Methods.
When you are using a character-only terminal (not a window system), cs uses three characters to describe, respectively, the coding system for keyboard input, the coding system for terminal output, and the coding system used for the file you are editing.
When multibyte characters are not enabled, cs does not appear at all. See section Enabling Multibyte Characters.
The colon after cs can change to another character in certain circumstances. Emacs uses newline to separate lines in the buffer. Some files use different conventions for separating lines: either carriage-return linefeed (the MS-DOS convention) or just carriage-return (the Macintosh convention). If the buffer's file uses carriage-return linefeed, the colon changes to a backslash (`\'). If the file uses just carriage-return, the colon indicator changes to a forward slash (`/').
See section Optional Mode Line Features, for features that add other handy information to the mode line, such as the current column number of point, the current time, and whether new mail for you has arrived.
Each Emacs frame normally has a menu bar at the top which you can use to perform certain common operations. There's no need to list them here, as you can more easily see for yourself.
When you are using a window system, you can use the mouse to choose a command from the menu bar. An arrow pointing right, after the menu item, indicates that the item leads to a subsidiary menu; `...' at the end means that the command will read arguments from the keyboard before it actually does anything.
To view the full command name and documentation for a menu item, type C-h k, and then select the menu bar with the mouse in the usual way (see section Documentation for a Key).
On text-only terminals with no mouse, you can use the menu bar by
typing M-` or F10 (these run the command
tmm-menubar). This command enters a mode in which you can select
a menu item from the keyboard. A provisional choice appears in the echo
area. You can use the left and right arrow keys to move through the
menu to different choices. When you have found the choice you want,
type RET to select it.
Each menu item also has an assigned letter or digit which designates that item; it is usually the initial of some word in the item's name. This letter or digit is separated from the item name by `=>'. You can type the item's letter or digit to select the item.
Some of the commands in the menu bar have ordinary key bindings as well; if so, the menu lists one equivalent key binding in parentheses after the item itself.
This chapter explains the character sets used by Emacs for input commands and for the contents of files, and also explains the concepts of keys and commands, which are fundamental for understanding how Emacs interprets your keyboard and mouse input.
GNU Emacs uses an extension of the ASCII character set for keyboard input; it also accepts non-character input events including function keys and mouse button actions.
ASCII consists of 128 character codes. Some of these codes are assigned graphic symbols such as `a' and `='; the rest are control characters, such as Control-a (usually written C-a for short). C-a gets its name from the fact that you type it by holding down the CTRL key while pressing a.
Some ASCII control characters have special names, and most terminals have special keys you can type them with: for example, RET, TAB, DEL and ESC. The space character is usually referred to below as SPC, even though strictly speaking it is a graphic character whose graphic happens to be blank. Some keyboards have a key labeled "linefeed" which is an alias for C-j.
Emacs extends the ASCII character set with thousands more printing characters (see section International Character Set Support), additional control characters, and a few more modifiers that can be combined with any character.
On ASCII terminals, there are only 32 possible control characters. These are the control variants of letters and `@[]\^_'. In addition, the shift key is meaningless with control characters: C-a and C-A are the same character, and Emacs cannot distinguish them.
But the Emacs character set has room for control variants of all printing characters, and for distinguishing between C-a and C-A. X Windows makes it possible to enter all these characters. For example, C-- (that's Control-Minus) and C-5 are meaningful Emacs commands under X.
Another Emacs character-set extension is additional modifier bits. Only one modifier bit is commonly used; it is called Meta. Every character has a Meta variant; examples include Meta-a (normally written M-a, for short), M-A (not the same character as M-a, but those two characters normally have the same meaning in Emacs), M-RET, and M-C-a. For reasons of tradition, we usually write C-M-a rather than M-C-a; logically speaking, the order in which the modifier keys CTRL and META are mentioned does not matter.
Some terminals have a META key, and allow you to type Meta characters by holding this key down. Thus, Meta-a is typed by holding down META and pressing a. The META key works much like the SHIFT key. Such a key is not always labeled META, however, as this function is often a special option for a key with some other primary purpose.
If there is no META key, you can still type Meta characters using two-character sequences starting with ESC. Thus, to enter M-a, you could type ESC a. To enter C-M-a, you would type ESC C-a. ESC is allowed on terminals with META keys, too, in case you have formed a habit of using it. X Windows provides several other modifier keys that can be applied to any input character. These are called SUPER, HYPER and ALT. We write `s-', `H-' and `A-' to say that a character uses these modifiers. Thus, s-H-C-x is short for Super-Hyper-Control-x. Not all X terminals actually provide keys for these modifier flags--in fact, many terminals have a key labeled ALT which is really a META key. The standard key bindings of Emacs do not include any characters with these modifiers. But you can assign them meanings of your own by customizing Emacs.
Keyboard input includes keyboard keys that are not characters at all: for example function keys and arrow keys. Mouse buttons are also outside the gamut of characters. You can modify these events with the modifier keys CTRL, META, SUPER, HYPER and ALT, just like keyboard characters.
Input characters and non-character inputs are collectively called input events. See section `Input Events' in The Emacs Lisp Reference Manual, for more information. If you are not doing Lisp programming, but simply want to redefine the meaning of some characters or non-character events, see section Customization.
ASCII terminals cannot really send anything to the computer except ASCII characters. These terminals use a sequence of characters to represent each function key. But that is invisible to the Emacs user, because the keyboard input routines recognize these special sequences and convert them to function key events before any other part of Emacs gets to see them.
A key sequence (key, for short) is a sequence of input events that are meaningful as a unit--as "a single command." Some Emacs command sequences are just one character or one event; for example, just C-f is enough to move forward one character. But Emacs also has commands that take two or more events to invoke.
If a sequence of events is enough to invoke a command, it is a complete key. Examples of complete keys include C-a, X, RET, NEXT (a function key), DOWN (an arrow key), C-x C-f, and C-x 4 C-f. If it isn't long enough to be complete, we call it a prefix key. The above examples show that C-x and C-x 4 are prefix keys. Every key sequence is either a complete key or a prefix key.
Most single characters constitute complete keys in the standard Emacs command bindings. A few of them are prefix keys. A prefix key combines with the following input event to make a longer key sequence, which may itself be complete or a prefix. For example, C-x is a prefix key, so C-x and the next input event combine to make a two-character key sequence. Most of these key sequences are complete keys, including C-x C-f and C-x b. A few, such as C-x 4 and C-x r, are themselves prefix keys that lead to three-character key sequences. There's no limit to the length of a key sequence, but in practice people rarely use sequences longer than four events.
By contrast, you can't add more events onto a complete key. For example, the two-character sequence C-f C-k is not a key, because the C-f is a complete key in itself. It's impossible to give C-f C-k an independent meaning as a command. C-f C-k is two key sequences, not one.
All told, the prefix keys in Emacs are C-c, C-h, C-x, C-x RET, C-x @, C-x a, C-x n, C-x r, C-x v, C-x 4, C-x 5, C-x 6, ESC, M-g and M-j. But this list is not cast in concrete; it is just a matter of Emacs's standard key bindings. If you customize Emacs, you can make new prefix keys, or eliminate these. See section Customizing Key Bindings.
If you do make or eliminate prefix keys, that changes the set of possible key sequences. For example, if you redefine C-f as a prefix, C-f C-k automatically becomes a key (complete, unless you define it too as a prefix). Conversely, if you remove the prefix definition of C-x 4, then C-x 4 f (or C-x 4 anything) is no longer a key.
Typing the help character (C-h or F1) after a prefix character displays a list of the commands starting with that prefix. There are a few prefix characters for which C-h does not work--for historical reasons, they have other meanings for C-h which are not easy to change. But F1 should work for all prefix characters.
This manual is full of passages that tell you what particular keys do. But Emacs does not assign meanings to keys directly. Instead, Emacs assigns meanings to named commands, and then gives keys their meanings by binding them to commands.
Every command has a name chosen by a programmer. The name is usually
made of a few English words separated by dashes; for example,
next-line or forward-word. A command also has a
function definition which is a Lisp program; this is what makes
the command do what it does. In Emacs Lisp, a command is actually a
special kind of Lisp function; one which specifies how to read arguments
for it and call it interactively. For more information on commands and
functions, see section `What Is a Function' in The Emacs Lisp Reference Manual. (The definition we use in this manual is
simplified slightly.)
The bindings between keys and commands are recorded in various tables called keymaps. See section Keymaps.
When we say that "C-n moves down vertically one line" we are
glossing over a distinction that is irrelevant in ordinary use but is vital
in understanding how to customize Emacs. It is the command
next-line that is programmed to move down vertically. C-n has
this effect because it is bound to that command. If you rebind
C-n to the command forward-word then C-n will move
forward by words instead. Rebinding keys is a common method of
customization.
In the rest of this manual, we usually ignore this subtlety to keep
things simple. To give the information needed for customization, we
state the name of the command which really does the work in parentheses
after mentioning the key that runs it. For example, we will say that
"The command C-n (next-line) moves point vertically
down," meaning that next-line is a command that moves vertically
down and C-n is a key that is standardly bound to it.
While we are on the subject of information for customization only,
it's a good time to tell you about variables. Often the
description of a command will say, "To change this, set the variable
mumble-foo." A variable is a name used to remember a value.
Most of the variables documented in this manual exist just to facilitate
customization: some command or other part of Emacs examines the variable
and behaves differently according to the value that you set. Until you
are interested in customizing, you can ignore the information about
variables. When you are ready to be interested, read the basic
information on variables, and then the information on individual
variables will make sense. See section Variables.
Text in Emacs buffers is a sequence of 8-bit bytes. Each byte can hold a single ASCII character. Both ASCII control characters (octal codes 000 through 037, and 0177) and ASCII printing characters (codes 040 through 0176) are allowed; however, non-ASCII control characters cannot appear in a buffer. The other modifier flags used in keyboard input, such as Meta, are not allowed in buffers either.
Some ASCII control characters serve special purposes in text, and have special names. For example, the newline character (octal code 012) is used in the buffer to end a line, and the tab character (octal code 011) is used for indenting to the next tab stop column (normally every 8 columns). See section How Text Is Displayed.
Non-ASCII printing characters can also appear in buffers. When multibyte characters are enabled, you can use any of the non-ASCII printing characters that Emacs supports. They have character codes starting at 256, octal 0400, and each one is represented as a sequence of two or more bytes. See section International Character Set Support.
If you disable multibyte characters, then you can use only one alphabet of non-ASCII characters, but they all fit in one byte. They use codes 0200 through 0377. See section Single-byte European Character Support.
The usual way to invoke Emacs is with the shell command `emacs'. Emacs clears the screen and then displays an initial help message and copyright notice. Some operating systems discard all type-ahead when Emacs starts up; they give Emacs no way to prevent this. Therefore, it is advisable to wait until Emacs clears the screen before typing your first editing command.
If you run Emacs from a shell window under the X Window System, run it in the background with `emacs&'. This way, Emacs does not tie up the shell window, so you can use that to run other shell commands while Emacs operates its own X windows. You can begin typing Emacs commands as soon as you direct your keyboard input to the Emacs frame.
When Emacs starts up, it makes a buffer named `*scratch*'.
That's the buffer you start out in. The `*scratch*' buffer uses Lisp
Interaction mode; you can use it to type Lisp expressions and evaluate
them, or you can ignore that capability and simply doodle. (You can
specify a different major mode for this buffer by setting the variable
initial-major-mode in your init file. See section The Init File, `~/.emacs'.)
It is possible to specify files to be visited, Lisp files to be loaded, and functions to be called, by giving Emacs arguments in the shell command line. See section Command Line Arguments. But we don't recommend doing this. The feature exists mainly for compatibility with other editors.
Many other editors are designed to be started afresh each time you want to edit. You edit one file and then exit the editor. The next time you want to edit either another file or the same one, you must run the editor again. With these editors, it makes sense to use a command-line argument to say which file to edit.
But starting a new Emacs each time you want to edit a different file does not make sense. For one thing, this would be annoyingly slow. For another, this would fail to take advantage of Emacs's ability to visit more than one file in a single editing session. And it would lose the other accumulated context, such as registers, undo history, and the mark ring.
The recommended way to use GNU Emacs is to start it only once, just after you log in, and do all your editing in the same Emacs session. Each time you want to edit a different file, you visit it with the existing Emacs, which eventually comes to have many files in it ready for editing. Usually you do not kill the Emacs until you are about to log out. See section File Handling, for more information on visiting more than one file.
There are two commands for exiting Emacs because there are two kinds of exiting: suspending Emacs and killing Emacs.
Suspending means stopping Emacs temporarily and returning control to its parent process (usually a shell), allowing you to resume editing later in the same Emacs job, with the same buffers, same kill ring, same undo history, and so on. This is the usual way to exit.
Killing Emacs means destroying the Emacs job. You can run Emacs again later, but you will get a fresh Emacs; there is no way to resume the same editing session after it has been killed.
suspend-emacs) or iconify a frame
(iconify-or-deiconify-frame).
save-buffers-kill-emacs).
To suspend Emacs, type C-z (suspend-emacs). This takes
you back to the shell from which you invoked Emacs. You can resume
Emacs with the shell command `%emacs' in most common shells.
On systems that do not support suspending programs, C-z starts an inferior shell that communicates directly with the terminal. Emacs waits until you exit the subshell. (The way to do that is probably with C-d or `exit', but it depends on which shell you use.) The only way on these systems to get back to the shell from which Emacs was run (to log out, for example) is to kill Emacs.
Suspending also fails if you run Emacs under a shell that doesn't
support suspending programs, even if the system itself does support it.
In such a case, you can set the variable cannot-suspend to a
non-nil value to force C-z to start an inferior shell.
(One might also describe Emacs's parent shell as "inferior" for
failing to support job control properly, but that is a matter of taste.)
When Emacs communicates directly with an X server and creates its own
dedicated X windows, C-z has a different meaning. Suspending an
applications that uses its own X windows is not meaningful or useful.
Instead, C-z runs the command iconify-or-deiconify-frame,
which temporarily closes up the selected Emacs frame (see section Frames and X Windows).
The way to get back to a shell window is with the window manager.
To kill Emacs, type C-x C-c (save-buffers-kill-emacs). A
two-character key is used for this to make it harder to type. This
command first offers to save any modified file-visiting buffers. If you
do not save them all, it asks for reconfirmation with yes before
killing Emacs, since any changes not saved will be lost forever. Also,
if any subprocesses are still running, C-x C-c asks for
confirmation about them, since killing Emacs will kill the subprocesses
immediately.
There is no way to restart an Emacs session once you have killed it. You can, however, arrange for Emacs to record certain session information, such as which files are visited, when you kill it, so that the next time you restart Emacs it will try to visit the same files and so on. See section Saving Emacs Sessions.
The operating system usually listens for certain special characters whose meaning is to kill or suspend the program you are running. This operating system feature is turned off while you are in Emacs. The meanings of C-z and C-x C-c as keys in Emacs were inspired by the use of C-z and C-c on several operating systems as the characters for stopping or killing a program, but that is their only relationship with the operating system. You can customize these keys to run any commands of your choice (see section Keymaps).
We now give the basics of how to enter text, make corrections, and
save the text in a file. If this material is new to you, you might
learn it more easily by running the Emacs learn-by-doing tutorial. To
use the tutorial, run Emacs and type Control-h t
(help-with-tutorial).
To clear the screen and redisplay, type C-l (recenter).
To insert printing characters into the text you are editing, just type them. This inserts the characters you type into the buffer at the cursor (that is, at point; see section Point). The cursor moves forward, and any text after the cursor moves forward too. If the text in the buffer is `FOOBAR', with the cursor before the `B', then if you type XX, you get `FOOXXBAR', with the cursor still before the `B'.
To delete text you have just inserted, use DEL. DEL deletes the character before the cursor (not the one that the cursor is on top of or under; that is the character after the cursor). The cursor and all characters after it move backwards. Therefore, if you type a printing character and then type DEL, they cancel out.
To end a line and start typing a new one, type RET. This inserts a newline character in the buffer. If point is in the middle of a line, RET splits the line. Typing DEL when the cursor is at the beginning of a line deletes the preceding newline, thus joining the line with the preceding line.
Emacs can split lines automatically when they become too long, if you turn on a special minor mode called Auto Fill mode. See section Filling Text, for how to use Auto Fill mode.
If you prefer to have text characters replace (overwrite) existing text rather than shove it to the right, you can enable Overwrite mode, a minor mode. See section Minor Modes.
Direct insertion works for printing characters and SPC, but other
characters act as editing commands and do not insert themselves. If you
need to insert a control character or a character whose code is above 200
octal, you must quote it by typing the character Control-q
(quoted-insert) first. (This character's name is normally written
C-q for short.) There are two ways to use C-q:
When multibyte characters are enabled, octal codes 0200 through 0377 are not valid as characters; if you specify a code in this range, C-q assumes that you intend to use some ISO Latin-n character set, and converts the specified code to the corresponding Emacs character code. See section Enabling Multibyte Characters. You select which ISO Latin character set though your choice of language environment (see section Language Environments).
To use decimal or hexadecimal instead of octal, set the variable
read-quoted-char-radix to 10 or 16. If the radix is greater than
10, some letters starting with a serve as part of a character
code, just like digits.
A numeric argument to C-q specifies how many copies of the quoted character should be inserted (see section Numeric Arguments).
Customization information: DEL in most modes runs the command
delete-backward-char; RET runs the command newline, and
self-inserting printing characters run the command self-insert,
which inserts whatever character was typed to invoke it. Some major modes
rebind DEL to other commands.
To do more than insert characters, you have to know how to move point (see section Point). The simplest way to do this is with arrow keys, or by clicking the left mouse button where you want to move to.
There are also control and meta characters for cursor motion. Some are equivalent to the arrow keys (these date back to the days before terminals had arrow keys, and are usable on terminals which don't have them). Others do more sophisticated things.
beginning-of-line).
end-of-line).
forward-char).
backward-char).
forward-word).
backward-word).
next-line). This command
attempts to keep the horizontal position unchanged, so if you start in
the middle of one line, you end in the middle of the next. When on
the last line of text, C-n creates a new line and moves onto it.
previous-line).
move-to-window-line). Text does not move on the screen.
A numeric argument says which screen line to place point on. It counts
screen lines down from the top of the window (zero for the top line). A
negative argument counts lines from the bottom (-1 for the bottom
line).
beginning-of-buffer). With
numeric argument n, move to n/10 of the way from the top.
See section Numeric Arguments, for more information on numeric arguments.end-of-buffer).
set-goal-column). Henceforth, those
commands always move to this column in each line moved into, or as
close as possible given the contents of the line. This goal column remains
in effect until canceled.
If you set the variable track-eol to a non-nil value,
then C-n and C-p when at the end of the starting line move
to the end of another line. Normally, track-eol is nil.
See section Variables, for how to set variables such as track-eol.
Normally, C-n on the last line of a buffer appends a newline to
it. If the variable next-line-add-newlines is nil, then
C-n gets an error instead (like C-p on the first line).
delete-backward-char).
delete-char).
kill-line).
kill-word).
backward-kill-word).
You already know about the DEL key which deletes the character before point (that is, before the cursor). Another key, Control-d (C-d for short), deletes the character after point (that is, the character that the cursor is on). This shifts the rest of the text on the line to the left. If you type C-d at the end of a line, it joins together that line and the next line.
To erase a larger amount of text, use the C-k key, which kills a line at a time. If you type C-k at the beginning or middle of a line, it kills all the text up to the end of the line. If you type C-k at the end of a line, it joins that line and the next line.
See section Deletion and Killing, for more flexible ways of killing text.
You can undo all the recent changes in the buffer text, up to a
certain point. Each buffer records changes individually, and the undo
command always applies to the current buffer. Usually each editing
command makes a separate entry in the undo records, but some commands
such as query-replace make many entries, and very simple commands
such as self-inserting characters are often grouped to make undoing less
tedious.
undo).
The command C-x u or C-_ is how you undo. The first time you give this command, it undoes the last change. Point moves back to where it was before the command that made the change.
Consecutive repetitions of C-_ or C-x u undo earlier and earlier changes, back to the limit of the undo information available. If all recorded changes have already been undone, the undo command prints an error message and does nothing.
Any command other than an undo command breaks the sequence of undo commands. Starting from that moment, the previous undo commands become ordinary changes that you can undo. Thus, to redo changes you have undone, type C-f or any other command that will harmlessly break the sequence of undoing, then type more undo commands.
Ordinary undo applies to all changes made in the current buffer. You
can also perform selective undo, limited to the current region.
To do this, specify the region you want, then run the undo
command with a prefix argument (the value does not matter): C-u C-x
u or C-u C-_. This undoes the most recent change in the region.
To undo further changes in the same region, repeat the undo
command (no prefix argument is needed). In Transient Mark mode, any use
of undo when there is an active region performs selective undo;
you do not need a prefix argument.
If you notice that a buffer has been modified accidentally, the easiest way to recover is to type C-_ repeatedly until the stars disappear from the front of the mode line. At this time, all the modifications you made have been canceled. Whenever an undo command makes the stars disappear from the mode line, it means that the buffer contents are the same as they were when the file was last read in or saved.
If you do not remember whether you changed the buffer deliberately, type C-_ once. When you see the last change you made undone, you will see whether it was an intentional change. If it was an accident, leave it undone. If it was deliberate, redo the change as described above.
Not all buffers record undo information. Buffers whose names start with spaces don't; these buffers are used internally by Emacs and its extensions to hold text that users don't normally look at or edit.
You cannot undo mere cursor motion; only changes in the buffer contents save undo information. However, some cursor motion commands set the mark, so if you use these commands from time to time, you can move back to the neighborhoods you have moved through by popping the mark ring (see section The Mark Ring).
When the undo information for a buffer becomes too large, Emacs
discards the oldest undo information from time to time (during garbage
collection). You can specify how much undo information to keep by
setting two variables: undo-limit and undo-strong-limit.
Their values are expressed in units of bytes of space.
The variable undo-limit sets a soft limit: Emacs keeps undo
data for enough commands to reach this size, and perhaps exceed it, but
does not keep data for any earlier commands beyond that. Its default
value is 20000. The variable undo-strong-limit sets a stricter
limit: the command which pushes the size past this amount is itself
forgotten. Its default value is 30000.
Regardless of the values of those variables, the most recent change is never discarded, so there is no danger that garbage collection occurring right after an unintentional large change might prevent you from undoing it.
The reason the undo command has two keys, C-x u and
C-_, set up to run it is that it is worthy of a single-character
key, but on some keyboards it is not obvious how to type C-_.
C-x u is an alternative you can type straightforwardly on any
terminal.
The commands described above are sufficient for creating and altering text in an Emacs buffer; the more advanced Emacs commands just make things easier. But to keep any text permanently you must put it in a file. Files are named units of text which are stored by the operating system for you to retrieve later by name. To look at or use the contents of a file in any way, including editing the file with Emacs, you must specify the file name.
Consider a file named `/usr/rms/foo.c'. In Emacs, to begin editing this file, type
C-x C-f /usr/rms/foo.c RET
Here the file name is given as an argument to the command C-x
C-f (find-file). That command uses the minibuffer to
read the argument, and you type RET to terminate the argument
(see section The Minibuffer).
Emacs obeys the command by visiting the file: creating a buffer,
copying the contents of the file into the buffer, and then displaying
the buffer for you to edit. If you alter the text, you can save
the new text in the file by typing C-x C-s (save-buffer).
This makes the changes permanent by copying the altered buffer contents
back into the file `/usr/rms/foo.c'. Until you save, the changes
exist only inside Emacs, and the file `foo.c' is unaltered.
To create a file, just visit the file with C-x C-f as if it already existed. This creates an empty buffer in which you can insert the text you want to put in the file. The file is actually created when you save this buffer with C-x C-s.
Of course, there is a lot more to learn about using files. See section File Handling.
If you forget what a key does, you can find out with the Help
character, which is C-h (or F1, which is an alias for
C-h). Type C-h k followed by the key you want to know
about; for example, C-h k C-n tells you all about what C-n
does. C-h is a prefix key; C-h k is just one of its
subcommands (the command describe-key). The other subcommands of
C-h provide different kinds of help. Type C-h twice to get
a description of all the help facilities. See section Help.
Here are special commands and techniques for putting in and taking out blank lines.
open-line).
delete-blank-lines).
When you want to insert a new line of text before an existing line, you
can do it by typing the new line of text, followed by RET.
However, it may be easier to see what you are doing if you first make a
blank line and then insert the desired text into it. This is easy to do
using the key C-o (open-line), which inserts a newline
after point but leaves point in front of the newline. After C-o,
type the text for the new line. C-o F O O has the same effect as
F O O RET, except for the final location of point.
You can make several blank lines by typing C-o several times, or by giving it a numeric argument to tell it how many blank lines to make. See section Numeric Arguments, for how. If you have a fill prefix, then C-o command inserts the fill prefix on the new line, when you use it at the beginning of a line. See section The Fill Prefix.
The easy way to get rid of extra blank lines is with the command
C-x C-o (delete-blank-lines). C-x C-o in a run of
several blank lines deletes all but one of them. C-x C-o on a
solitary blank line deletes that blank line. When point is on a
nonblank line, C-x C-o deletes any blank lines following that
nonblank line.
If you add too many characters to one line without breaking it with RET, the line will grow to occupy two (or more) lines on the screen, with a `\' at the extreme right margin of all but the last of them. The `\' says that the following screen line is not really a distinct line in the text, but just the continuation of a line too long to fit the screen. Continuation is also called line wrapping.
Sometimes it is nice to have Emacs insert newlines automatically when a line gets too long. Continuation on the screen does not do that. Use Auto Fill mode (see section Filling Text) if that's what you want.
As an alternative to continuation, Emacs can display long lines by truncation. This means that all the characters that do not fit in the width of the screen or window do not appear at all. They remain in the buffer, temporarily invisible. `$' is used in the last column instead of `\' to inform you that truncation is in effect.
Truncation instead of continuation happens whenever horizontal
scrolling is in use, and optionally in all side-by-side windows
(see section Multiple Windows). You can enable truncation for a particular buffer by
setting the variable truncate-lines to non-nil in that
buffer. (See section Variables.) Altering the value of
truncate-lines makes it local to the current buffer; until that
time, the default value is in effect. The default is initially
nil. See section Local Variables.
See section Variables Controlling Display, for additional variables that affect how text is displayed.
Here are commands to get information about the size and position of parts of the buffer, and to count lines.
count-lines-region).
See section The Mark and the Region, for information about the region.
what-cursor-position).
There are two commands for working with line numbers. M-x what-line computes the current line number and displays it in the echo area. To go to a given line by number, use M-x goto-line; it prompts you for the number. These line numbers count from one at the beginning of the buffer.
You can also see the current line number in the mode line; See section The Mode Line. If you narrow the buffer, then the line number in the mode line
is relative to the accessible portion (see section Narrowing). By contrast,
what-line shows both the line number relative to the narrowed
region and the line number relative to the whole buffer.
By contrast, M-x what-page counts pages from the beginning of the file, and counts lines within the page, printing both numbers. See section Pages.
While on this subject, we might as well mention M-= (count-lines-region),
which prints the number of lines in the region (see section The Mark and the Region).
See section Pages, for the command C-x l which counts the lines in the
current page.
The command C-x = (what-cursor-position) can be used to find out
the column that the cursor is in, and other miscellaneous information about
point. It prints a line in the echo area that looks like this:
Char: c (0143, 99, 0x63) point=21044 of 26883(78%) column 53
(In fact, this is the output produced when point is before the `column' in the example.)
The four values after `Char:' describe the character that follows point, first by showing it and then by giving its character code in octal, decimal and hex.
`point=' is followed by the position of point expressed as a character count. The front of the buffer counts as position 1, one character later as 2, and so on. The next, larger, number is the total number of characters in the buffer. Afterward in parentheses comes the position expressed as a percentage of the total size.
`column' is followed by the horizontal position of point, in columns from the left edge of the window.
If the buffer has been narrowed, making some of the text at the beginning and the end temporarily inaccessible, C-x = prints additional text describing the currently accessible range. For example, it might display this:
Char: C (0103, 67, 0x43) point=252 of 889(28%) <231 - 599> column 0
where the two extra numbers give the smallest and largest character position that point is allowed to assume. The characters between those two positions are the accessible ones. See section Narrowing.
If point is at the end of the buffer (or the end of the accessible part), C-x = omits any description of the character after point. The output might look like this:
point=26957 of 26956(100%) column 0
In mathematics and computer usage, the word argument means "data provided to a function or operation." You can give any Emacs command a numeric argument (also called a prefix argument). Some commands interpret the argument as a repetition count. For example, C-f with an argument of ten moves forward ten characters instead of one. With these commands, no argument is equivalent to an argument of one. Negative arguments tell most such commands to move or act in the opposite direction.
If your terminal keyboard has a META key, the easiest way to specify a numeric argument is to type digits and/or a minus sign while holding down the META key. For example,
M-5 C-n
would move down five lines. The characters Meta-1, Meta-2,
and so on, as well as Meta--, do this because they are keys bound
to commands (digit-argument and negative-argument) that
are defined to contribute to an argument for the next command. Digits
and - modified with Control, or Control and Meta, also specify
numeric arguments.
Another way of specifying an argument is to use the C-u
(universal-argument) command followed by the digits of the
argument. With C-u, you can type the argument digits without
holding down modifier keys; C-u works on all terminals. To type a
negative argument, type a minus sign after C-u. Just a minus sign
without digits normally means -1.
C-u followed by a character which is neither a digit nor a minus sign has the special meaning of "multiply by four." It multiplies the argument for the next command by four. C-u twice multiplies it by sixteen. Thus, C-u C-u C-f moves forward sixteen characters. This is a good way to move forward "fast," since it moves about 1/5 of a line in the usual size screen. Other useful combinations are C-u C-n, C-u C-u C-n (move down a good fraction of a screen), C-u C-u C-o (make "a lot" of blank lines), and C-u C-k (kill four lines).
Some commands care only about whether there is an argument, and not about
its value. For example, the command M-q (fill-paragraph) with
no argument fills text; with an argument, it justifies the text as well.
(See section Filling Text, for more information on M-q.) Plain C-u is a
handy way of providing an argument for such commands.
Some commands use the value of the argument as a repeat count, but do
something peculiar when there is no argument. For example, the command
C-k (kill-line) with argument n kills n lines,
including their terminating newlines. But C-k with no argument is
special: it kills the text up to the next newline, or, if point is right at
the end of the line, it kills the newline itself. Thus, two C-k
commands with no arguments can kill a nonblank line, just like C-k
with an argument of one. (See section Deletion and Killing, for more information on
C-k.)
A few commands treat a plain C-u differently from an ordinary argument. A few others may treat an argument of just a minus sign differently from an argument of -1. These unusual cases are described when they come up; they are always for reasons of convenience of use of the individual command.
You can use a numeric argument to insert multiple copies of a character. This is straightforward unless the character is a digit; for example, C-u 6 4 a inserts 64 copies of the character `a'. But this does not work for inserting digits; C-u 6 4 1 specifies an argument of 641, rather than inserting anything. To separate the digit to insert from the argument, type another C-u; for example, C-u 6 4 C-u 1 does insert 64 copies of the character `1'.
We use the term "prefix argument" as well as "numeric argument" to emphasize that you type the argument before the command, and to distinguish these arguments from minibuffer arguments that come after the command.
The command C-x z (repeat) provides another way to repeat
an Emacs command many times. This command repeats the previous Emacs
command, whatever that was. Repeating a command uses the same arguments
that were used before; it does not read new arguments each time.
To repeat the command more than once, type additional z's: each z repeats the command one more time. Repetition ends when you type a character other than z, or press a mouse button.
For example, suppose you type C-u 2 0 C-d to delete 20 characters. You can repeat that command (including its argument) three additional times, to delete a total of 80 characters, by typing C-x z z z. The first C-x z repeats the command once, and each subsequent z repeats it once again.
The minibuffer is the facility used by Emacs commands to read arguments more complicated than a single number. Minibuffer arguments can be file names, buffer names, Lisp function names, Emacs command names, Lisp expressions, and many other things, depending on the command reading the argument. You can use the usual Emacs editing commands in the minibuffer to edit the argument text.
When the minibuffer is in use, it appears in the echo area, and the terminal's cursor moves there. The beginning of the minibuffer line displays a prompt which says what kind of input you should supply and how it will be used. Often this prompt is derived from the name of the command that the argument is for. The prompt normally ends with a colon.
Sometimes a default argument appears in parentheses after the colon; it too is part of the prompt. The default will be used as the argument value if you enter an empty argument (for example, just type RET). For example, commands that read buffer names always show a default, which is the name of the buffer that will be used if you type just RET.
The simplest way to enter a minibuffer argument is to type the text you want, terminated by RET which exits the minibuffer. You can cancel the command that wants the argument, and get out of the minibuffer, by typing C-g.
Since the minibuffer uses the screen space of the echo area, it can conflict with other ways Emacs customarily uses the echo area. Here is how Emacs handles such conflicts:
Sometimes the minibuffer starts out with text in it. For example, when you are supposed to give a file name, the minibuffer starts out containing the default directory, which ends with a slash. This is to inform you which directory the file will be found in if you do not specify a directory.
For example, the minibuffer might start out with these contents:
Find File: /u2/emacs/src/
where `Find File: ' is the prompt. Typing buffer.c specifies the file `/u2/emacs/src/buffer.c'. To find files in nearby directories, use ..; thus, if you type ../lisp/simple.el, you will get the file named `/u2/emacs/lisp/simple.el'. Alternatively, you can kill with M-DEL the directory names you don't want (see section Words).
If you don't want any of the default, you can kill it with C-a C-k. But you don't need to kill the default; you can simply ignore it. Insert an absolute file name, one starting with a slash or a tilde, after the default directory. For example, to specify the file `/etc/termcap', just insert that name, giving these minibuffer contents:
Find File: /u2/emacs/src//etc/termcap
Two slashes in a row are not normally meaningful in a file name, but they are allowed in GNU Emacs. They mean, "ignore everything before the second slash in the pair." Thus, `/u2/emacs/src/' is ignored in the example above, and you get the file `/etc/termcap'.
If you set insert-default-directory to nil, the default
directory is not inserted in the minibuffer. This way, the minibuffer
starts out empty. But the name you type, if relative, is still
interpreted with respect to the same default directory.
The minibuffer is an Emacs buffer (albeit a peculiar one), and the usual Emacs commands are available for editing the text of an argument you are entering.
Since RET in the minibuffer is defined to exit the minibuffer, you can't use it to insert a newline in the minibuffer. To do that, type C-o or C-q C-j. (Recall that a newline is really the character control-J.)
The minibuffer has its own window which always has space on the screen but acts as if it were not there when the minibuffer is not in use. When the minibuffer is in use, its window is just like the others; you can switch to another window with C-x o, edit text in other windows and perhaps even visit more files, before returning to the minibuffer to submit the argument. You can kill text in another window, return to the minibuffer window, and then yank the text to use it in the argument. See section Multiple Windows.
There are some restrictions on the use of the minibuffer window, however. You cannot switch buffers in it--the minibuffer and its window are permanently attached. Also, you cannot split or kill the minibuffer window. But you can make it taller in the normal fashion with C-x ^. If you enable Resize-Minibuffer mode, then the minibuffer window expands vertically as necessary to hold the text that you put in the minibuffer. Use M-x resize-minibuffer-mode to enable or disable this minor mode (see section Minor Modes).
Scrolling works specially in the minibuffer window. When the
minibuffer is just one line high, and it contains a long line of text
that won't fit on the screen, scrolling automatically maintains an
overlap of a certain number of characters from one continuation line to
the next. The variable minibuffer-scroll-overlap specifies how
many characters of overlap; the default is 20.
If while in the minibuffer you issue a command that displays help text of any sort in another window, you can use the C-M-v command while in the minibuffer to scroll the help text. This lasts until you exit the minibuffer. This feature is especially useful if a completing minibuffer gives you a list of possible completions. See section Using Other Windows.
Emacs normally disallows most commands that use the minibuffer while
the minibuffer is active. This rule is to prevent recursive minibuffers
from confusing novice users. If you want to be able to use such
commands in the minibuffer, set the variable
enable-recursive-minibuffers to a non-nil value.
For certain kinds of arguments, you can use completion to enter the argument value. Completion means that you type part of the argument, then Emacs visibly fills in the rest, or as much as can be determined from the part you have typed.
When completion is available, certain keys---TAB, RET, and SPC---are rebound to complete the text present in the minibuffer into a longer string that it stands for, by matching it against a set of completion alternatives provided by the command reading the argument. ? is defined to display a list of possible completions of what you have inserted.
For example, when M-x uses the minibuffer to read the name of a command, it provides a list of all available Emacs command names to complete against. The completion keys match the text in the minibuffer against all the command names, find any additional name characters implied by the ones already present in the minibuffer, and add those characters to the ones you have given. This is what makes it possible to type M-x ins SPC b RET instead of M-x insert-buffer RET (for example).
Case is normally significant in completion, because it is significant in most of the names that you can complete (buffer names, file names and command names). Thus, `fo' does not complete to `Foo'. Completion does ignore case distinctions for certain arguments in which case does not matter.
A concrete example may help here. If you type M-x au TAB,
the TAB looks for alternatives (in this case, command names) that
start with `au'. There are several, including
auto-fill-mode and auto-save-mode---but they are all the
same as far as auto-, so the `au' in the minibuffer changes
to `auto-'.
If you type TAB again immediately, there are multiple possibilities for the very next character--it could be any of `cfilrs'---so no more characters are added; instead, TAB displays a list of all possible completions in another window.
If you go on to type f TAB, this TAB sees
`auto-f'. The only command name starting this way is
auto-fill-mode, so completion fills in the rest of that. You now
have `auto-fill-mode' in the minibuffer after typing just au
TAB f TAB. Note that TAB has this effect because in
the minibuffer it is bound to the command minibuffer-complete
when completion is available.
Here is a list of the completion commands defined in the minibuffer when completion is available.
minibuffer-complete).
minibuffer-complete-word).
minibuffer-complete-and-exit).
minibuffer-list-completions).
SPC completes much like TAB, but never goes beyond the
next hyphen or space. If you have `auto-f' in the minibuffer and
type SPC, it finds that the completion is `auto-fill-mode',
but it stops completing after `fill-'. This gives
`auto-fill-'. Another SPC at this point completes all the
way to `auto-fill-mode'. SPC in the minibuffer when
completion is available runs the command
minibuffer-complete-word.
Here are some commands you can use to choose a completion from a window that displays a list of completions:
mouse-choose-completion).
You normally use this command while point is in the minibuffer; but you
must click in the list of completions, not in the minibuffer itself.
switch-to-completions). This paves the way for using the
commands below. (Selecting that window in the usual ways has the same
effect, but this way is more convenient.)
choose-completion). To
use this command, you must first switch windows to the window that shows
the list of completions.
next-completion).
previous-completion).
There are three different ways that RET can work in completing minibuffers, depending on how the argument will be used.
The completion commands display a list of all possible completions in a window whenever there is more than one possibility for the very next character. Also, typing ? explicitly requests such a list. If the list of completions is long, you can scroll it with C-M-v (see section Using Other Windows).
When completion is done on file names, certain file names are usually
ignored. The variable completion-ignored-extensions contains a
list of strings; a file whose name ends in any of those strings is
ignored as a possible completion. The standard value of this variable
has several elements including ".o", ".elc", ".dvi"
and "~". The effect is that, for example, `foo' can
complete to `foo.c' even though `foo.o' exists as well.
However, if all the possible completions end in "ignored"
strings, then they are not ignored. Ignored extensions do not apply to
lists of completions--those always mention all possible completions.
Normally, a completion command that finds the next character is undetermined
automatically displays a list of all possible completions. If the variable
completion-auto-help is set to nil, this does not happen,
and you must type ? to display the possible completions.
The complete library implements a more powerful kind of
completion that can complete multiple words at a time. For example, it
can complete the command name abbreviation p-b into
print-buffer, because no other command starts with two words
whose initials are `p' and `b'. To use this library, put
(load "complete") in your `~/.emacs' file (see section The Init File, `~/.emacs').
Icomplete mode presents a constantly-updated display that tells you what completions are available for the text you've entered so far. The command to enable or disable this minor mode is M-x icomplete-mode.
Every argument that you enter with the minibuffer is saved on a minibuffer history list so that you can use it again later in another argument. Special commands load the text of an earlier argument in the minibuffer. They discard the old minibuffer contents, so you can think of them as moving through the history of previous arguments.
previous-history-element).
next-history-element).
previous-matching-history-element).
next-matching-history-element).
The simplest way to reuse the saved arguments in the history list is
to move through the history list one element at a time. While in the
minibuffer, use M-p or up-arrow (previous-history-element)
to "move to" the next earlier minibuffer input, and use M-n or
down-arrow (next-history-element) to "move to" the next later
input.
The previous input that you fetch from the history entirely replaces the contents of the minibuffer. To use it as the argument, exit the minibuffer as usual with RET. You can also edit the text before you reuse it; this does not change the history element that you "moved" to, but your new argument does go at the end of the history list in its own right.
For many minibuffer arguments there is a "default" value. In some cases, the minibuffer history commands know the default value. Then you can insert the default value into the minibuffer as text by using M-n to move "into the future" in the history. Eventually we hope to make this feature available whenever the minibuffer has a default value.
There are also commands to search forward or backward through the
history; they search for history elements that match a regular
expression that you specify with the minibuffer. M-r
(previous-matching-history-element) searches older elements in
the history, while M-s (next-matching-history-element)
searches newer elements. By special dispensation, these commands can
use the minibuffer to read their arguments even though you are already
in the minibuffer when you issue them. As with incremental searching,
an uppercase letter in the regular expression makes the search
case-sensitive (see section Searching and Case).
All uses of the minibuffer record your input on a history list, but there are separate history lists for different kinds of arguments. For example, there is a list for file names, used by all the commands that read file names. (As a special feature, this history list records the absolute file name, no more and no less, even if that is not how you entered the file name.)
There are several other very specific history lists, including one for
command names read by M-x, one for buffer names, one for arguments
of commands like query-replace, and one for compilation commands
read by compile. Finally, there is one "miscellaneous" history
list that most minibuffer arguments use.
The variable history-length specifies the maximum length of a
minibuffer history list; once a list gets that long, the oldest element
is deleted each time an element is added. If the value of
history-length is t, though, there is no maximum length
and elements are never deleted.
Every command that uses the minibuffer at least once is recorded on a special history list, together with the values of its arguments, so that you can repeat the entire command. In particular, every use of M-x is recorded there, since M-x uses the minibuffer to read the command name.
repeat-complex-command).
C-x ESC ESC is used to re-execute a recent minibuffer-using command. With no argument, it repeats the last such command. A numeric argument specifies which command to repeat; one means the last one, and larger numbers specify earlier ones.
C-x ESC ESC works by turning the previous command into a Lisp expression and then entering a minibuffer initialized with the text for that expression. If you type just RET, the command is repeated as before. You can also change the command by editing the Lisp expression. Whatever expression you finally submit is what will be executed. The repeated command is added to the front of the command history unless it is identical to the most recently executed command already there.
Even if you don't understand Lisp syntax, it will probably be obvious which command is displayed for repetition. If you do not change the text, it will repeat exactly as before.
Once inside the minibuffer for C-x ESC ESC, you can use the minibuffer history commands (M-p, M-n, M-r, M-s; see section Minibuffer History) to move through the history list of saved entire commands. After finding the desired previous command, you can edit its expression as usual and then resubmit it by typing RET as usual.
The list of previous minibuffer-using commands is stored as a Lisp
list in the variable command-history. Each element is a Lisp
expression which describes one command and its arguments. Lisp programs
can re-execute a command by calling eval with the
command-history element.
The Emacs commands that are used often or that must be quick to type are bound to keys--short sequences of characters--for convenient use. Other Emacs commands that do not need to be brief are not bound to keys; to run them, you must refer to them by name.
A command name is, by convention, made up of one or more words,
separated by hyphens; for example, auto-fill-mode or
manual-entry. The use of English words makes the command name
easier to remember than a key made up of obscure characters, even though
it is more characters to type.
The way to run a command by name is to start with M-x, type the command name, and finish it with RET. M-x uses the minibuffer to read the command name. RET exits the minibuffer and runs the command. The string `M-x' appears at the beginning of the minibuffer as a prompt to remind you to enter the name of a command to be run. See section The Minibuffer, for full information on the features of the minibuffer.
You can use completion to enter the command name. For example, the
command forward-char can be invoked by name by typing
M-x forward-char RET
or
M-x forw TAB c RET
Note that forward-char is the same command that you invoke with
the key C-f. You can run any Emacs command by name using
M-x, whether or not any keys are bound to it.
If you type C-g while the command name is being read, you cancel the M-x command and get out of the minibuffer, ending up at top level.
To pass a numeric argument to the command you are invoking with M-x, specify the numeric argument before the M-x. M-x passes the argument along to the command it runs. The argument value appears in the prompt while the command name is being read.
If the command you type has a key binding of its own, Emacs mentions
this in the echo area, two seconds after the command finishes (if you
don't type anything else first). For example, if you type M-x
forward-word, the message says that you can run the same command more
easily by typing M-f. You can turn off these messages by setting
suggest-key-bindings to nil.
Normally, when describing in this manual a command that is run by name, we omit the RET that is needed to terminate the name. Thus we might speak of M-x auto-fill-mode rather than M-x auto-fill-mode RET. We mention the RET only when there is a need to emphasize its presence, such as when we show the command together with following arguments.
M-x works by running the command
execute-extended-command, which is responsible for reading the
name of another command and invoking it.
Emacs provides extensive help features accessible through a single character, C-h. C-h is a prefix key that is used only for documentation-printing commands. The characters that you can type after C-h are called help options. One help option is C-h; that is how you ask for help about using C-h. To cancel, type C-g. The function key F1 is equivalent to C-h.
C-h C-h (help-for-help) displays a list of the possible
help options, each with a brief description. Before you type a help
option, you can use SPC or DEL to scroll through the list.
C-h or F1 means "help" in various other contexts as
well. For example, in the middle of query-replace, it describes
the options available for how to operate on the current match. After a
prefix key, it displays a list of the alternatives that can follow the
prefix key. (A few prefix keys don't support C-h, because they
define other meanings for it, but they all support F1.)
Most help buffers use a special major mode, Help mode, which lets you scroll conveniently with SPC and DEL.
Here is a summary of the defined help commands.
apropos-command).
describe-bindings).
describe-key-briefly). Here c stands for `character'. For more
extensive information on key, use C-h k.
describe-function). Since commands are Lisp functions,
a command name may be used.
info).
The complete Emacs manual is available on-line in Info.
describe-key).
view-lossage).
describe-mode).
view-emacs-news).
finder-by-keyword).
describe-syntax). See section The Syntax Table.
help-with-tutorial).
describe-variable).
where-is).
describe-coding-system).
describe-input-method).
describe-language-support).
Info-goto-emacs-command-node).
Info-goto-emacs-key-command-node).
info-lookup-symbol).
The most basic C-h options are C-h c
(describe-key-briefly) and C-h k (describe-key).
C-h c key prints in the echo area the name of the command
that key is bound to. For example, C-h c C-f prints
`forward-char'. Since command names are chosen to describe what
the commands do, this is a good way to get a very brief description of
what key does.
C-h k key is similar but gives more information: it displays the documentation string of the command as well as its name. This is too big for the echo area, so a window is used for the display.
C-h c and C-h k work for any sort of key sequences, including function keys and mouse events.
C-h f (describe-function) reads the name of a Lisp function
using the minibuffer, then displays that function's documentation string
in a window. Since commands are Lisp functions, you can use this to get
the documentation of a command that you know by name. For example,
C-h f auto-fill-mode RET
displays the documentation of auto-fill-mode. This is the only
way to get the documentation of a command that is not bound to any key
(one which you would normally run using M-x).
C-h f is also useful for Lisp functions that you are planning to
use in a Lisp program. For example, if you have just written the
expression (make-vector len) and want to check that you are using
make-vector properly, type C-h f make-vector RET.
Because C-h f allows all function names, not just command names,
you may find that some of your favorite abbreviations that work in
M-x don't work in C-h f. An abbreviation may be unique
among command names yet fail to be unique when other function names are
allowed.
The function name for C-h f to describe has a default which is
used if you type RET leaving the minibuffer empty. The default is
the function called by the innermost Lisp expression in the buffer around
point, provided that is a valid, defined Lisp function name. For
example, if point is located following the text `(make-vector (car
x)', the innermost list containing point is the one that starts with
`(make-vector', so the default is to describe the function
make-vector.
C-h f is often useful just to verify that you have the right spelling for the function name. If C-h f mentions a name from the buffer as the default, that name must be defined as a Lisp function. If that is all you want to know, just type C-g to cancel the C-h f command, then go on editing.
C-h w command RET tells you what keys are bound to
command. It prints a list of the keys in the echo area. If it
says the command is not on any key, you must use M-x to run it.
C-h w runs the command where-is.
C-h v (describe-variable) is like C-h f but describes
Lisp variables instead of Lisp functions. Its default is the Lisp symbol
around or before point, but only if that is the name of a known Lisp
variable. See section Variables.
A more sophisticated sort of question to ask is, "What are the
commands for working with files?" To ask this question, type C-h
a file RET, which displays a list of all command names that
contain `file', including copy-file, find-file, and
so on. With each command name appears a brief description of how to use
the command, and what keys you can currently invoke it with. For
example, it would say that you can invoke find-file by typing
C-x C-f. The a in C-h a stands for `Apropos';
C-h a runs the command apropos-command. This command
normally checks only commands (interactive functions); if you specify a
prefix argument, it checks noninteractive functions as well.
Because C-h a looks only for functions whose names contain the string you specify, you must use ingenuity in choosing the string. If you are looking for commands for killing backwards and C-h a kill-backwards RET doesn't reveal any, don't give up. Try just kill, or just backwards, or just back. Be persistent. Also note that you can use a regular expression as the argument, for more flexibility (see section Syntax of Regular Expressions).
Here is a set of arguments to give to C-h a that covers many
classes of Emacs commands, since there are strong conventions for naming
the standard Emacs commands. By giving you a feel for the naming
conventions, this set should also serve to aid you in developing a
technique for picking apropos strings.
char, line, word, sentence, paragraph, region, page, sexp, list, defun, rect, buffer, frame, window, face, file, dir, register, mode, beginning, end, forward, backward, next, previous, up, down, search, goto, kill, delete, mark, insert, yank, fill, indent, case, change, set, what, list, find, view, describe, default.
To list all user variables that match a regexp, use the command M-x apropos-variable. This command shows only user variables and customization options by default; if you specify a prefix argument, it checks all variables.
To list all Lisp symbols that contain a match for a regexp, not just the ones that are defined as commands, use the command M-x apropos instead of C-h a. This command does not check key bindings by default; specify a numeric argument if you want it to check them.
The apropos-documentation command is like apropos except
that it searches documentation strings as well as symbol names for
matches for the specified regular expression.
The apropos-value command is like apropos except that it
searches symbols' values for matches for the specified regular
expression. This command does not check function definitions or
property lists by default; specify a numeric argument if you want it to
check them.
If the variable apropos-do-all is non-nil, the commands
above all behave as if they had been given a prefix argument.
If you want more information about a function definition, variable or symbol property listed in the Apropos buffer, you can click on it with Mouse-2 or move there and type RET.
The C-h p command lets you search the standard Emacs Lisp libraries by topic keywords. Here is a partial list of keywords you can use:
abbrev --- abbreviation handling, typing shortcuts, macros.
bib --- support for the bibliography processor bib.
c --- C and C++ language support.
calendar --- calendar and time management support.
comm --- communications, networking, remote access to files.
data --- support for editing files of data.
docs --- support for Emacs documentation.
emulations --- emulations of other editors.
extensions --- emacs Lisp language extensions.
faces --- support for using faces (fonts and colors; see section Using Multiple Typefaces).
frames --- support for Emacs frames and window systems.
games --- games, jokes and amusements.
hardware --- support for interfacing with exotic hardware.
help --- support for on-line help systems.
hypermedia --- support for links within text, or other media types.
i18n --- internationalization and alternate character-set support.
internal --- code for Emacs internals, build process, defaults.
languages --- specialized modes for editing programming languages.
lisp --- support for using Lisp (including Emacs Lisp).
local --- libraries local to your site.
maint --- maintenance aids for the Emacs development group.
mail --- modes for electronic-mail handling.
matching --- searching and matching.
news --- support for netnews reading and posting.
non-text --- support for editing files that are not ordinary text.
oop --- support for object-oriented programming.
outlines --- hierarchical outlining.
processes --- process, subshell, compilation, and job control support.
terminals --- support for terminal types.
tex --- support for the TeX formatter.
tools --- programming tools.
unix --- front-ends/assistants for, or emulators of, Unix features.
vms --- support code for VMS.
wp --- word processing.
You can use the command C-h L
(describe-language-environment) to find out the support for a
specific language environment. See section Language Environments. This
tells you which languages this language environment is useful for, and
lists the character sets, coding systems, and input methods that go with
it. It also shows some sample text to illustrate scripts.
The command C-h h (view-hello-file) displays the file
`etc/HELLO', which shows how to say "hello" in many languages.
The command C-h I (describe-input-method) describes
information about input methods--either a specified input method, or by
default the input method in use. See section Input Methods.
The command C-h C (describe-coding-system) describes
information about coding systems--either a specified coding system, or
the ones currently in use. See section Coding Systems.
Help buffers provide the commands of View mode (see section Miscellaneous File Operations), plus a few special commands of their own.
When a command name (see section Running Commands by Name) or variable name (see section Variables) appears in the documentation, it normally appears inside paired single-quotes. You can click on the name with Mouse-2, or move point there and type RET, to view the documentation of that command or variable. Use C-c C-b to retrace your steps.
There are convenient commands for moving point to cross references in
the help text. TAB (help-next-ref) moves point down to the
next cross reference. Use S-TAB to move point up to the
previous cross reference (help-previous-ref).
C-h i (info) runs the Info program, which is used for
browsing through structured documentation files. The entire Emacs manual
is available within Info. Eventually all the documentation of the GNU
system will be available. Type h after entering Info to run
a tutorial on using Info.
If you specify a numeric argument, C-h i prompts for the name of a documentation file. This way, you can browse a file which doesn't have an entry in the top-level Info menu. It is also handy when you need to get to the documentation quickly, and you know the exact name of the file.
There are two special help commands for accessing Emacs documentation
through Info. C-h C-f function RET enters Info and
goes straight to the documentation of the Emacs function
function. C-h C-k key enters Info and goes straight
to the documentation of the key key. These two keys run the
commands Info-goto-emacs-command-node and
Info-goto-emacs-key-command-node.
When editing a program, if you have an Info version of the manual for the programming language, you can use the command C-h C-i to refer to the manual documentation for a symbol (keyword, function or variable). The details of how this command works depend on the major mode.
If something surprising happens, and you are not sure what commands you
typed, use C-h l (view-lossage). C-h l prints the last
100 command characters you typed in. If you see commands that you don't
know, you can use C-h c to find out what they do.
Emacs has numerous major modes, each of which redefines a few keys and
makes a few other changes in how editing works. C-h m
(describe-mode) prints documentation on the current major mode,
which normally describes all the commands that are changed in this
mode.
C-h b (describe-bindings) and C-h s
(describe-syntax) present other information about the current
Emacs mode. C-h b displays a list of all the key bindings now in
effect; the local bindings defined by the current minor modes first,
then the local bindings defined by the current major mode, and finally
the global bindings (see section Customizing Key Bindings). C-h s displays the
contents of the syntax table, with explanations of each character's
syntax (see section The Syntax Table).
You can get a similar list for a particular prefix key by typing C-h after the prefix key. (There are a few prefix keys for which this does not work--those that provide their own bindings for C-h. One of these is ESC, because ESC C-h is actually C-M-h, which marks a defun.)
The other C-h options display various files of useful
information. C-h C-w displays the full details on the complete
absence of warranty for GNU Emacs. C-h n (view-emacs-news)
displays the file `emacs/etc/NEWS', which contains documentation on
Emacs changes arranged chronologically. C-h t
(help-with-tutorial) displays the learn-by-doing Emacs tutorial.
C-h C-c (describe-copying) displays the file
`emacs/etc/COPYING', which tells you the conditions you must obey
in distributing copies of Emacs. C-h C-d
(describe-distribution) displays the file
`emacs/etc/DISTRIB', which tells you how you can order a copy of
the latest version of Emacs. C-h C-p (describe-project)
displays general information about the GNU Project.
Many Emacs commands operate on an arbitrary contiguous part of the current buffer. To specify the text for such a command to operate on, you set the mark at one end of it, and move point to the other end. The text between point and the mark is called the region. Emacs highlights the region whenever there is one, if you enable Transient Mark mode (see section Transient Mark Mode).
You can move point or the mark to adjust the boundaries of the region. It doesn't matter which one is set first chronologically, or which one comes earlier in the text. Once the mark has been set, it remains where you put it until you set it again at another place. Each Emacs buffer has its own mark, so that when you return to a buffer that had been selected previously, it has the same mark it had before.
Many commands that insert text, such as C-y (yank) and
M-x insert-buffer, position point and the mark at opposite ends of
the inserted text, so that the region contains the text just inserted.
Aside from delimiting the region, the mark is also useful for remembering a spot that you may want to go back to. To make this feature more useful, each buffer remembers 16 previous locations of the mark in the mark ring.
Here are some commands for setting the mark:
set-mark-command).
exchange-point-and-mark).
mouse-save-then-kill).
For example, suppose you wish to convert part of the buffer to
upper case, using the C-x C-u (upcase-region) command,
which operates on the text in the region. You can first go to the
beginning of the text to be capitalized, type C-SPC to put
the mark there, move to the end, and then type C-x C-u. Or, you
can set the mark at the end of the text, move to the beginning, and then
type C-x C-u.
The most common way to set the mark is with the C-SPC command
(set-mark-command). This sets the mark where point is. Then you
can move point away, leaving the mark behind.
There are two ways to set the mark with the mouse. You can drag mouse button one across a range of text; that puts point where you release the mouse button, and sets the mark at the other end of that range. Or you can click mouse button three, which sets the mark at point (like C-SPC) and them moves point (like Mouse-1). Both of these methods copy the region into the kill ring in addition to setting the mark; that gives behavior consistent with other window-driven applications, but if you don't want to modify the kill ring, you must use keyboard commands to set the mark. See section Mouse Commands for Editing.
Ordinary terminals have only one cursor, so there is no way for Emacs
to show you where the mark is located. You have to remember. The usual
solution to this problem is to set the mark and then use it soon, before
you forget where it is. Alternatively, you can see where the mark is
with the command C-x C-x (exchange-point-and-mark) which
puts the mark where point was and point where the mark was. The extent
of the region is unchanged, but the cursor and point are now at the
previous position of the mark. In Transient Mark mode, this command
reactivates the mark.
C-x C-x is also useful when you are satisfied with the position of point but want to move the other end of the region (where the mark is); do C-x C-x to put point at that end of the region, and then move it. A second use of C-x C-x, if necessary, puts the mark at the new position with point back at its original position.
There is no such character as C-SPC in ASCII; when you
type SPC while holding down CTRL, what you get on most
ordinary terminals is the character C-@. This key is actually
bound to set-mark-command. But unless you are unlucky enough to
have a terminal where typing C-SPC does not produce
C-@, you might as well think of this character as
C-SPC. Under X, C-SPC is actually a distinct
character, but its binding is still set-mark-command.
Emacs can highlight the current region, using X Windows. But normally it does not. Why not?
Highlighting the region doesn't work well ordinarily in Emacs, because once you have set a mark, there is always a region (in that buffer). And highlighting the region all the time would be a nuisance.
You can turn on region highlighting by enabling Transient Mark mode. This is a more rigid mode of operation in which the region "lasts" only temporarily, so you must set up a region for each command that uses one. In Transient Mark mode, most of the time there is no region; therefore, highlighting the region when it exists is convenient.
To enable Transient Mark mode, type M-x transient-mark-mode. This command toggles the mode, so you can repeat the command to turn off the mode.
Here are the details of Transient Mark mode:
set-mark-command).
This makes the mark active; as you move point, you will see the region
highlighting grow and shrink.
exchange-point-and-mark).
Highlighting of the region uses the region face; you can
customize how the region is highlighted by changing this face.
See section Customizing Faces.
When multiple windows show the same buffer, they can have different
regions, because they can have different values of point (though they
all share one common mark position). Ordinarily, only the selected
window highlights its region (see section Multiple Windows). However, if the
variable highlight-nonselected-windows is non-nil, then
each window highlights its own region (provided that Transient Mark mode
is enabled and the window's buffer's mark is active).
When Transient Mark mode is not enabled, every command that sets the mark also activates it, and nothing ever deactivates it.
If the variable mark-even-if-inactive is non-nil in
Transient Mark mode, then commands can use the mark and the region
even when it is inactive. Region highlighting appears and disappears
just as it normally does in Transient Mark mode, but the mark doesn't
really go away when the highlighting disappears.
Transient Mark mode is also sometimes known as "Zmacs mode" because the Zmacs editor on the MIT Lisp Machine handled the mark in a similar way.
Once you have a region and the mark is active, here are some of the ways you can operate on the region:
Most commands that operate on the text in the
region have the word region in their names.
Here are the commands for placing point and the mark around a textual object such as a word, list, paragraph or page.
mark-word). This command and
the following one do not move point.
mark-sexp).
mark-paragraph).
mark-defun).
mark-whole-buffer).
mark-page).
M-@ (mark-word) puts the mark at the end of the next word,
while C-M-@ (mark-sexp) puts it at the end of the next Lisp
expression. These commands handle arguments just like M-f and
C-M-f.
Other commands set both point and mark, to delimit an object in the
buffer. For example, M-h (mark-paragraph) moves point to
the beginning of the paragraph that surrounds or follows point, and puts
the mark at the end of that paragraph (see section Paragraphs). It prepares
the region so you can indent, case-convert, or kill a whole paragraph.
C-M-h (mark-defun) similarly puts point before and the
mark after the current or following defun (see section Defuns). C-x
C-p (mark-page) puts point before the current page, and mark at
the end (see section Pages). The mark goes after the terminating page
delimiter (to include it), while point goes after the preceding page
delimiter (to exclude it). A numeric argument specifies a later page
(if positive) or an earlier page (if negative) instead of the current
page.
Finally, C-x h (mark-whole-buffer) sets up the entire
buffer as the region, by putting point at the beginning and the mark at
the end.
In Transient Mark mode, all of these commands activate the mark.
Aside from delimiting the region, the mark is also useful for
remembering a spot that you may want to go back to. To make this
feature more useful, each buffer remembers 16 previous locations of the
mark, in the mark ring. Commands that set the mark also push the
old mark onto this ring. To return to a marked location, use C-u
C-SPC (or C-u C-@); this is the command
set-mark-command given a numeric argument. It moves point to
where the mark was, and restores the mark from the ring of former
marks. Thus, repeated use of this command moves point to all of the old
marks on the ring, one by one. The mark positions you move through in
this way are not lost; they go to the end of the ring.
Each buffer has its own mark ring. All editing commands use the current buffer's mark ring. In particular, C-u C-SPC always stays in the same buffer.
Many commands that can move long distances, such as M-<
(beginning-of-buffer), start by setting the mark and saving the
old mark on the mark ring. This is to make it easier for you to move
back later. Searches set the mark if they move point. You can tell
when a command sets the mark because it displays `Mark Set' in the
echo area.
If you want to move back to the same place over and over, the mark ring may not be convenient enough. If so, you can record the position in a register for later retrieval (see section Saving Positions in Registers).
The variable mark-ring-max specifies the maximum number of
entries to keep in the mark ring. If that many entries exist and
another one is pushed, the last one in the list is discarded. Repeating
C-u C-SPC cycles through the positions currently in the
ring.
The variable mark-ring holds the mark ring itself, as a list of
marker objects, with the most recent first. This variable is local in
every buffer.
In addition to the ordinary mark ring that belongs to each buffer, Emacs has a single global mark ring. It records a sequence of buffers in which you have recently set the mark, so you can go back to those buffers.
Setting the mark always makes an entry on the current buffer's mark ring. If you have switched buffers since the previous mark setting, the new mark position makes an entry on the global mark ring also. The result is that the global mark ring records a sequence of buffers that you have been in, and, for each buffer, a place where you set the mark.
The command C-x C-SPC (pop-global-mark) jumps to
the buffer and position of the latest entry in the global ring. It also
rotates the ring, so that successive uses of C-x C-SPC take
you to earlier and earlier buffers.
Killing means erasing text and copying it into the kill ring, from which it can be retrieved by yanking it. Some systems use the terms "cutting" and "pasting" for these operations.
The commonest way of moving or copying text within Emacs is to kill it and later yank it elsewhere in one or more places. This is very safe because Emacs remembers several recent kills, not just the last one. It is versatile, because the many commands for killing syntactic units can also be used for moving those units. But there are other ways of copying text for special purposes.
Emacs has only one kill ring for all buffers, so you can kill text in one buffer and yank it in another buffer.
Most commands which erase text from the buffer save it in the kill
ring so that you can move or copy it to other parts of the buffer.
These commands are known as kill commands. The rest of the
commands that erase text do not save it in the kill ring; they are known
as delete commands. (This distinction is made only for erasure of
text in the buffer.) If you do a kill or delete command by mistake, you
can use the C-x u (undo) command to undo it
(see section Undoing Changes).
The delete commands include C-d (delete-char) and
DEL (delete-backward-char), which delete only one character at
a time, and those commands that delete only spaces or newlines. Commands
that can destroy significant amounts of nontrivial data generally kill.
The commands' names and individual descriptions use the words `kill'
and `delete' to say which they do.
delete-char).
delete-backward-char).
delete-horizontal-space).
just-one-space).
delete-blank-lines).
delete-indentation).
The most basic delete commands are C-d (delete-char) and
DEL (delete-backward-char). C-d deletes the
character after point, the one the cursor is "on top of." This
doesn't move point. DEL deletes the character before the cursor,
and moves point back. You can delete newlines like any other characters
in the buffer; deleting a newline joins two lines. Actually, C-d
and DEL aren't always delete commands; when given arguments, they
kill instead, since they can erase more than one character this way.
The other delete commands are those which delete only whitespace
characters: spaces, tabs and newlines. M-\
(delete-horizontal-space) deletes all the spaces and tab
characters before and after point. M-SPC
(just-one-space) does likewise but leaves a single space after
point, regardless of the number of spaces that existed previously (even
zero).
C-x C-o (delete-blank-lines) deletes all blank lines
after the current line. If the current line is blank, it deletes all
blank lines preceding the current line as well (leaving one blank line,
the current line).
M-^ (delete-indentation) joins the current line and the
previous line, by deleting a newline and all surrounding spaces, usually
leaving a single space. See section Indentation.
kill-line).
The simplest kill command is C-k. If given at the beginning of a line, it kills all the text on the line, leaving it blank. When used on a blank line, it kills the whole line including its newline. To kill an entire non-blank line, go to the beginning and type C-k twice.
More generally, C-k kills from point up to the end of the line, unless it is at the end of a line. In that case it kills the newline following point, thus merging the next line into the current one. Spaces and tabs that you can't see at the end of the line are ignored when deciding which case applies, so if point appears to be at the end of the line, you can be sure C-k will kill the newline.
When C-k is given a positive argument, it kills that many lines and the newlines that follow them (however, text on the current line before point is spared). With a negative argument -n, it kills n lines preceding the current line (together with the text on the current line before point). Thus, C-u - 2 C-k at the front of a line kills the two previous lines.
C-k with an argument of zero kills the text before point on the current line.
If the variable kill-whole-line is non-nil, C-k at
the very beginning of a line kills the entire line including the
following newline. This variable is normally nil.
kill-region).
kill-word). See section Words.
backward-kill-word).
backward-kill-sentence).
See section Sentences.
kill-sentence).
kill-sexp). See section Lists and Sexps.
zap-to-char).
A kill command which is very general is C-w
(kill-region), which kills everything between point and the
mark. With this command, you can kill any contiguous sequence of
characters, if you first set the region around them.
A convenient way of killing is combined with searching: M-z
(zap-to-char) reads a character and kills from point up to (and
including) the next occurrence of that character in the buffer. A
numeric argument acts as a repeat count. A negative argument means to
search backward and kill text before point.
Other syntactic units can be killed: words, with M-DEL and M-d (see section Words); sexps, with C-M-k (see section Lists and Sexps); and sentences, with C-x DEL and M-k (see section Sentences).
You can use kill commands in read-only buffers. They don't actually change the buffer, and they beep to warn you of that, but they do copy the text you tried to kill into the kill ring, so you can yank it into other buffers. Most of the kill commands move point across the text they copy in this way, so that successive kill commands build up a single kill ring entry as usual.
Yanking means reinserting text previously killed. This is what some systems call "pasting." The usual way to move or copy text is to kill it and then yank it elsewhere one or more times.
yank).
yank-pop).
kill-ring-save).
append-next-kill).
All killed text is recorded in the kill ring, a list of blocks of text that have been killed. There is only one kill ring, shared by all buffers, so you can kill text in one buffer and yank it in another buffer. This is the usual way to move text from one file to another. (See section Accumulating Text, for some other ways.)
The command C-y (yank) reinserts the text of the most recent
kill. It leaves the cursor at the end of the text. It sets the mark at
the beginning of the text. See section The Mark and the Region.
C-u C-y leaves the cursor in front of the text, and sets the mark after it. This happens only if the argument is specified with just a C-u, precisely. Any other sort of argument, including C-u and digits, specifies an earlier kill to yank (see section Yanking Earlier Kills).
To copy a block of text, you can use M-w
(kill-ring-save), which copies the region into the kill ring
without removing it from the buffer. This is approximately equivalent
to C-w followed by C-x u, except that M-w does not
alter the undo history and does not temporarily change the screen.
Normally, each kill command pushes a new entry onto the kill ring. However, two or more kill commands in a row combine their text into a single entry, so that a single C-y yanks all the text as a unit, just as it was before it was killed.
Thus, if you want to yank text as a unit, you need not kill all of it with one command; you can keep killing line after line, or word after word, until you have killed it all, and you can still get it all back at once.
Commands that kill forward from point add onto the end of the previous killed text. Commands that kill backward from point add text onto the beginning. This way, any sequence of mixed forward and backward kill commands puts all the killed text into one entry without rearrangement. Numeric arguments do not break the sequence of appending kills. For example, suppose the buffer contains this text:
This is a line -!-of sample text.
with point shown by -!-. If you type M-d M-DEL M-d M-DEL, killing alternately forward and backward, you end up with `a line of sample' as one entry in the kill ring, and `This is text.' in the buffer. (Note the double space, which you can clean up with M-SPC or M-q.)
Another way to kill the same text is to move back two words with M-b M-b, then kill all four words forward with C-u M-d. This produces exactly the same results in the buffer and in the kill ring. M-f M-f C-u M-DEL kills the same text, all going backward; once again, the result is the same. The text in the kill ring entry always has the same order that it had in the buffer before you killed it.
If a kill command is separated from the last kill command by other
commands (not just numeric arguments), it starts a new entry on the kill
ring. But you can force it to append by first typing the command
C-M-w (append-next-kill) right before it. The C-M-w
tells the following command, if it is a kill command, to append the text
it kills to the last killed text, instead of starting a new entry. With
C-M-w, you can kill several separated pieces of text and
accumulate them to be yanked back in one place.
A kill command following M-w does not append to the text that M-w copied into the kill ring.
To recover killed text that is no longer the most recent kill, use the
M-y command (yank-pop). It takes the text previously
yanked and replaces it with the text from an earlier kill. So, to
recover the text of the next-to-the-last kill, first use C-y to
yank the last kill, and then use M-y to replace it with the
previous kill. M-y is allowed only after a C-y or another
M-y.
You can understand M-y in terms of a "last yank" pointer which points at an entry in the kill ring. Each time you kill, the "last yank" pointer moves to the newly made entry at the front of the ring. C-y yanks the entry which the "last yank" pointer points to. M-y moves the "last yank" pointer to a different entry, and the text in the buffer changes to match. Enough M-y commands can move the pointer to any entry in the ring, so you can get any entry into the buffer. Eventually the pointer reaches the end of the ring; the next M-y moves it to the first entry again.
M-y moves the "last yank" pointer around the ring, but it does not change the order of the entries in the ring, which always runs from the most recent kill at the front to the oldest one still remembered.
M-y can take a numeric argument, which tells it how many entries to advance the "last yank" pointer by. A negative argument moves the pointer toward the front of the ring; from the front of the ring, it moves "around" to the last entry and continues forward from there.
Once the text you are looking for is brought into the buffer, you can stop doing M-y commands and it will stay there. It's just a copy of the kill ring entry, so editing it in the buffer does not change what's in the ring. As long as no new killing is done, the "last yank" pointer remains at the same place in the kill ring, so repeating C-y will yank another copy of the same previous kill.
If you know how many M-y commands it would take to find the text you want, you can yank that text in one step using C-y with a numeric argument. C-y with an argument restores the text the specified number of entries back in the kill ring. Thus, C-u 2 C-y gets the next-to-the-last block of killed text. It is equivalent to C-y M-y. C-y with a numeric argument starts counting from the "last yank" pointer, and sets the "last yank" pointer to the entry that it yanks.
The length of the kill ring is controlled by the variable
kill-ring-max; no more than that many blocks of killed text are
saved.
The actual contents of the kill ring are stored in a variable named
kill-ring; you can view the entire contents of the kill ring with
the command C-h v kill-ring.
Usually we copy or move text by killing it and yanking it, but there are other methods convenient for copying one block of text in many places, or for copying many scattered blocks of text into one place. To copy one block to many places, store it in a register (see section Registers). Here we describe the commands to accumulate scattered pieces of text into a buffer or into a file.
To accumulate text into a buffer, use M-x append-to-buffer.
This reads a buffer name, then inserts a copy of the region into the
buffer specified. If you specify a nonexistent buffer,
append-to-buffer creates the buffer. The text is inserted
wherever point is in that buffer. If you have been using the buffer for
editing, the copied text goes into the middle of the text of the buffer,
wherever point happens to be in it.
Point in that buffer is left at the end of the copied text, so
successive uses of append-to-buffer accumulate the text in the
specified buffer in the same order as they were copied. Strictly
speaking, append-to-buffer does not always append to the text
already in the buffer--it appends only if point in that buffer is at the end.
However, if append-to-buffer is the only command you use to alter
a buffer, then point is always at the end.
M-x prepend-to-buffer is just like append-to-buffer
except that point in the other buffer is left before the copied text, so
successive prependings add text in reverse order. M-x
copy-to-buffer is similar except that any existing text in the other
buffer is deleted, so the buffer is left containing just the text newly
copied into it.
To retrieve the accumulated text from another buffer, use the command M-x insert-buffer; this too takes buffername as an argument. It inserts a copy of the text in buffer buffername into the selected buffer. You can alternatively select the other buffer for editing, then optionally move text from it by killing. See section Using Multiple Buffers, for background information on buffers.
Instead of accumulating text within Emacs, in a buffer, you can append text directly into a file with M-x append-to-file, which takes filename as an argument. It adds the text of the region to the end of the specified file. The file is changed immediately on disk.
You should use append-to-file only with files that are
not being visited in Emacs. Using it on a file that you are
editing in Emacs would change the file behind Emacs's back, which
can lead to losing some of your editing.
The rectangle commands operate on rectangular areas of the text: all the characters between a certain pair of columns, in a certain range of lines. Commands are provided to kill rectangles, yank killed rectangles, clear them out, fill them with blanks or text, or delete them. Rectangle commands are useful with text in multicolumn formats, and for changing text into or out of such formats.
When you must specify a rectangle for a command to work on, you do it by putting the mark at one corner and point at the opposite corner. The rectangle thus specified is called the region-rectangle because you control it in about the same way the region is controlled. But remember that a given combination of point and mark values can be interpreted either as a region or as a rectangle, depending on the command that uses them.
If point and the mark are in the same column, the rectangle they delimit is empty. If they are in the same line, the rectangle is one line high. This asymmetry between lines and columns comes about because point (and likewise the mark) is between two columns, but within a line.
kill-rectangle).
delete-rectangle).
yank-rectangle).
open-rectangle). This pushes the previous contents of the
region-rectangle rightward.
string-rectangle).
The rectangle operations fall into two classes: commands deleting and inserting rectangles, and commands for blank rectangles.
There are two ways to get rid of the text in a rectangle: you can
discard the text (delete it) or save it as the "last killed"
rectangle. The commands for these two ways are C-x r d
(delete-rectangle) and C-x r k (kill-rectangle). In
either case, the portion of each line that falls inside the rectangle's
boundaries is deleted, causing following text (if any) on the line to
move left into the gap.
Note that "killing" a rectangle is not killing in the usual sense; the rectangle is not stored in the kill ring, but in a special place that can only record the most recent rectangle killed. This is because yanking a rectangle is so different from yanking linear text that different yank commands have to be used and yank-popping is hard to make sense of.
To yank the last killed rectangle, type C-x r y
(yank-rectangle). Yanking a rectangle is the opposite of killing
one. Point specifies where to put the rectangle's upper left corner.
The rectangle's first line is inserted there, the rectangle's second
line is inserted at a position one line vertically down, and so on. The
number of lines affected is determined by the height of the saved
rectangle.
You can convert single-column lists into double-column lists using rectangle killing and yanking; kill the second half of the list as a rectangle and then yank it beside the first line of the list. See section Two-Column Editing, for another way to edit multi-column text.
You can also copy rectangles into and out of registers with C-x r r r and C-x r i r. See section Saving Rectangles in Registers.
There are two commands you can use for making blank rectangles:
M-x clear-rectangle which blanks out existing text, and C-x r
o (open-rectangle) which inserts a blank rectangle. Clearing a
rectangle is equivalent to deleting it and then inserting a blank
rectangle of the same size.
The command M-x delete-whitespace-rectangle deletes horizontal whitespace starting from a particular column. This applies to each of the lines in the rectangle, and the column is specified by the left edge of the rectangle. The right edge of the rectangle does not make any difference to this command.
The command C-x r t (M-x string-rectangle) replaces the
rectangle with a specified string (inserted once on each line). The
string's width need not be the same as the width of the rectangle. if
the string's width is less, the text after the rectangle shifts left; if
the stringis wider than the rectangle, the text after the rectangle
shifts right.
Emacs registers are places you can save text or positions for later use. Once you save text or a rectangle in a register, you can copy it into the buffer once or many times; you can move point to a position saved in a register once or many times.
Each register has a name which is a single character. A register can store a piece of text, a rectangle, a position, a window configuration, or a file name, but only one thing at any given time. Whatever you store in a register remains there until you store something else in that register. To see what a register r contains, use M-x view-register.
Saving a position records a place in a buffer so that you can move back there later. Moving to a saved position switches to that buffer and moves point to that place in it.
point-to-register).
jump-to-register).
To save the current position of point in a register, choose a name r and type C-x r SPC r. The register r retains the position thus saved until you store something else in that register.
The command C-x r j r moves point to the position recorded in register r. The register is not affected; it continues to record the same position. You can jump to the saved position any number of times.
If you use C-x r j to go to a saved position, but the buffer it was saved from has been killed, C-x r j tries to create the buffer again by visiting the same file. Of course, this works only for buffers that were visiting files.
When you want to insert a copy of the same piece of text several times, it may be inconvenient to yank it from the kill ring, since each subsequent kill moves that entry further down the ring. An alternative is to store the text in a register and later retrieve it.
copy-to-register).
insert-register).
C-x r s r stores a copy of the text of the region into the register named r. Given a numeric argument, C-x r s r deletes the text from the buffer as well.
C-x r i r inserts in the buffer the text from register r. Normally it leaves point before the text and places the mark after, but with a numeric argument (C-u) it puts point after the text and the mark before.
A register can contain a rectangle instead of linear text. The rectangle is represented as a list of strings. See section Rectangles, for basic information on how to specify a rectangle in the buffer.
copy-rectangle-to-register). With numeric argument, delete it as
well.
insert-register).
The C-x r i r command inserts a text string if the register contains one, and inserts a rectangle if the register contains one.
See also the command sort-columns, which you can think of
as sorting a rectangle. See section Sorting Text.
You can save the window configuration of the selected frame in a register, or even the configuration of all windows in all frames, and restore the configuration later.
window-configuration-to-register).
frame-configuration-to-register).
Use C-x r j r to restore a window or frame configuration. This is the same command used to restore a cursor position. When you restore a frame configuration, any existing frames not included in the configuration become invisible. If you wish to delete these frames instead, use C-u C-x r j r.
There are commands to store a number in a register, to insert the number in the buffer in decimal, and to increment it. These commands can be useful in keyboard macros (see section Keyboard Macros).
number-to-register).
increment-register).
C-x r g is the same command used to insert any other sort of register contents into the buffer.
If you visit certain file names frequently, you can visit them more conveniently if you put their names in registers. Here's the Lisp code used to put a file name in a register:
(set-register ?r '(file . name))
For example,
(set-register ?z '(file . "/gd/gnu/emacs/19.0/src/ChangeLog"))
puts the file name shown in register `z'.
To visit the file whose name is in register r, type C-x r j r. (This is the same command used to jump to a position or restore a frame configuration.)
Bookmarks are somewhat like registers in that they record positions you can jump to. Unlike registers, they have long names, and they persist automatically from one Emacs session to the next. The prototypical use of bookmarks is to record "where you were reading" in various files.
bookmark-set).
bookmark-jump).
list-bookmarks).
The prototypical use for bookmarks is to record one current position in each of several files. So the command C-x r m, which sets a bookmark, uses the visited file name as the default for the bookmark name. If you name each bookmark after the file it points to, then you can conveniently revisit any of those files with C-x r b, and move to the position of the bookmark at the same time.
To display a list of all your bookmarks in a separate buffer, type
C-x r l (list-bookmarks). If you switch to that buffer,
you can use it to edit your bookmark definitions or annotate the
bookmarks. Type C-h m in that buffer for more information about
its special editing commands.
When you kill Emacs, Emacs offers to save your bookmark values in your default bookmark file, `~/.emacs.bmk', if you have changed any bookmark values. You can also save the bookmarks at any time with the M-x bookmark-save command. The bookmark commands load your default bookmark file automatically. This saving and loading is how bookmarks persist from one Emacs session to the next.
If you set the variable bookmark-save-flag to 1, then each
command that sets a bookmark will also save your bookmarks; this way,
you don't lose any bookmark values even if Emacs crashes. (The value,
if a number, says how many bookmark modifications should go by between
saving.)
Bookmark position values are saved with surrounding context, so that
bookmark-jump can find the proper position even if the file is
modified slightly. The variable bookmark-search-size says how
many characters of context to record, on each side of the bookmark's
position.
Here are some additional commands for working with bookmarks:
bookmark-write, to
work with other files of bookmark values in addition to your default
bookmark file.
Since only part of a large buffer fits in the window, Emacs tries to show a part that is likely to be interesting. Display-control commands allow you to specify which part of the text you want to see, and how to display it.
If a buffer contains text that is too large to fit entirely within a window that is displaying the buffer, Emacs shows a contiguous portion of the text. The portion shown always contains point.
Scrolling means moving text up or down in the window so that different parts of the text are visible. Scrolling forward means that text moves up, and new text appears at the bottom. Scrolling backward moves text down and new text appears at the top.
Scrolling happens automatically if you move point past the bottom or top of the window. You can also explicitly request scrolling with the commands in this section.
recenter).
scroll-up).
scroll-down).
recenter).
reposition-window).
The most basic scrolling command is C-l (recenter) with
no argument. It clears the entire screen and redisplays all windows.
In addition, it scrolls the selected window so that point is halfway
down from the top of the window.
The scrolling commands C-v and M-v let you move all the text
in the window up or down a few lines. C-v (scroll-up) with an
argument shows you that many more lines at the bottom of the window, moving
the text and point up together as C-l might. C-v with a
negative argument shows you more lines at the top of the window.
M-v (scroll-down) is like C-v, but moves in the
opposite direction. The function keys NEXT and PRIOR are
equivalent to C-v and M-v.
The names of scroll commands are based on the direction that the text
moves in the window. Thus, the command to scroll forward is called
scroll-up because it moves the text upward on the screen.
To read the buffer a windowful at a time, use C-v with no argument.
It takes the last two lines at the bottom of the window and puts them at
the top, followed by nearly a whole windowful of lines not previously
visible. If point was in the text scrolled off the top, it moves to the
new top of the window. M-v with no argument moves backward with
overlap similarly. The number of lines of overlap across a C-v or
M-v is controlled by the variable next-screen-context-lines; by
default, it is 2.
Some users like the full-screen scroll commands to keep point at the
same screen position. To enable this behavior, set the variable
scroll-preserve-screen-position to a non-nil value. This
mode is convenient for browsing through a file by scrolling by
screenfuls; if you come back to the screen where you started, point goes
back to its starting value. However, this mode is inconvenient when you
move to the next screen in order to move point to the text there.
Another way to do scrolling is with C-l with a numeric argument. C-l does not clear the screen when given an argument; it only scrolls the selected window. With a positive argument n, it repositions text to put point n lines down from the top. An argument of zero puts point on the very top line. Point does not move with respect to the text; rather, the text and point move rigidly on the screen. C-l with a negative argument puts point that many lines from the bottom of the window. For example, C-u - 1 C-l puts point on the bottom line, and C-u - 5 C-l puts it five lines from the bottom. Just C-u as argument, as in C-u C-l, scrolls point to the center of the selected window.
The C-M-l command (reposition-window) scrolls the current
window heuristically in a way designed to get useful information onto
the screen. For example, in a Lisp file, this command tries to get the
entire current defun onto the screen if possible.
Scrolling happens automatically if point has moved out of the visible
portion of the text when it is time to display. Normally, automatic
scrolling centers point vertically within the window. However, if you
set scroll-conservatively to a small number n, then if you
move point just a little off the screen--less than n lines--then
Emacs scrolls the text just far enough to bring point back on screen.
By default, scroll-conservatively is 0.
The variable scroll-margin restricts how close point can come
to the top or bottom of a window. Its value is a number of screen
lines; if point comes within that many lines of the top or bottom of the
window, Emacs recenters the window. By default, scroll-margin is
0.
Horizontal scrolling means shifting all the lines sideways within a window--so that some of the text near the left margin is not displayed at all.
scroll-left).
scroll-right).
When a window has been scrolled horizontally, text lines are truncated rather than continued (see section Continuation Lines), with a `$' appearing in the first column when there is text truncated to the left, and in the last column when there is text truncated to the right.
The command C-x < (scroll-left) scrolls the selected
window to the left by n columns with argument n. This moves
part of the beginning of each line off the left edge of the window.
With no argument, it scrolls by almost the full width of the window (two
columns less, to be precise).
C-x > (scroll-right) scrolls similarly to the right. The
window cannot be scrolled any farther to the right once it is displayed
normally (with each line starting at the window's left margin);
attempting to do so has no effect. This means that you don't have to
calculate the argument precisely for C-x >; any sufficiently large
argument will restore the normal display.
You can request automatic horizontal scrolling by enabling Hscroll mode. When this mode is enabled, Emacs scrolls a window horizontally whenever that is necessary to keep point visible and not too far from the left or right edge. The command to enable or disable this mode is M-x hscroll-mode.
Follow mode is a minor mode that makes two windows showing the same buffer scroll as one tall "virtual window." To use Follow mode, go to a frame with just one window, split it into two side-by-side windows using C-x 3, and then type M-x follow-mode. From then on, you can edit the buffer in either of the two windows, or scroll either one; the other window follows it.
To turn off Follow mode, type M-x follow-mode a second time.
Emacs has the ability to hide lines indented more than a certain number of columns (you specify how many columns). You can use this to get an overview of a part of a program.
To hide lines, type C-x $ (set-selective-display) with a
numeric argument n. Then lines with at least n columns of
indentation disappear from the screen. The only indication of their
presence is that three dots (`...') appear at the end of each
visible line that is followed by one or more hidden ones.
The commands C-n and C-p move across the hidden lines as if they were not there.
The hidden lines are still present in the buffer, and most editing commands see them as usual, so you may find point in the middle of the hidden text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots.
To make all lines visible again, type C-x $ with no argument.
If you set the variable selective-display-ellipses to
nil, the three dots do not appear at the end of a line that
precedes hidden lines. Then there is no visible indication of the
hidden lines. This variable becomes local automatically when set.
The current line number of point appears in the mode line when Line Number mode is enabled. Use the command M-x line-number-mode to turn this mode on and off; normally it is on. The line number appears before the buffer percentage pos, with the letter `L' to indicate what it is. See section Minor Modes, for more information about minor modes and about how to use this command.
If the buffer is very large (larger than the value of
line-number-display-limit), then the line number doesn't appear.
Emacs doesn't compute the line number when the buffer is large, because
that would be too slow. If you have narrowed the buffer
(see section Narrowing), the displayed line number is relative to the
accessible portion of the buffer.
You can also display the current column number by turning on Column Number mode. It displays the current column number preceded by the letter `C'. Type M-x column-number-mode to toggle this mode.
Emacs can optionally display the time and system load in all mode lines. To enable this feature, type M-x display-time. The information added to the mode line usually appears after the buffer name, before the mode names and their parentheses. It looks like this:
hh:mmpm l.ll
Here hh and mm are the hour and minute, followed always by
`am' or `pm'. l.ll is the average number of running
processes in the whole system recently. (Some fields may be missing if
your operating system cannot support them.) If you prefer time display
in 24-hour format, set the variable display-time-24hr-format
to t.
The word `Mail' appears after the load level if there is mail for you that you have not read yet.
ASCII printing characters (octal codes 040 through 0176) in Emacs buffers are displayed with their graphics. So are non-ASCII multibyte printing characters (octal codes above 0400).
Some ASCII control characters are displayed in special ways. The newline character (octal code 012) is displayed by starting a new line. The tab character (octal code 011) is displayed by moving to the next tab stop column (normally every 8 columns).
Other ASCII control characters are normally displayed as a caret (`^') followed by the non-control version of the character; thus, control-A is displayed as `^A'.
Non-ASCII characters 0200 through 0377 are displayed with octal escape sequences; thus, character code 0243 (octal) is displayed as `\243'. However, if you enable European display, most of these characters become non-ASCII printing characters, and are displayed using their graphics (assuming your terminal supports them). See section Single-byte European Character Support.
This section contains information for customization only. Beginning users should skip it.
The variable mode-line-inverse-video controls whether the mode
line is displayed in inverse video (assuming the terminal supports it);
nil means don't do so. See section The Mode Line. If you specify the
foreground color for the modeline face, and
mode-line-inverse-video is non-nil, then the default
background color for that face is the usual foreground color.
See section Using Multiple Typefaces.
If the variable inverse-video is non-nil, Emacs attempts
to invert all the lines of the display from what they normally are.
If the variable visible-bell is non-nil, Emacs attempts
to make the whole screen blink when it would normally make an audible bell
sound. This variable has no effect if your terminal does not have a way
to make the screen blink.
When you reenter Emacs after suspending, Emacs normally clears the
screen and redraws the entire display. On some terminals with more than
one page of memory, it is possible to arrange the termcap entry so that
the `ti' and `te' strings (output to the terminal when Emacs
is entered and exited, respectively) switch between pages of memory so
as to use one page for Emacs and another page for other output. Then
you might want to set the variable no-redraw-on-reenter
non-nil; this tells Emacs to assume, when resumed, that the
screen page it is using still contains what Emacs last wrote there.
The variable echo-keystrokes controls the echoing of multi-character
keys; its value is the number of seconds of pause required to cause echoing
to start, or zero meaning don't echo at all. See section The Echo Area.
If the variable ctl-arrow is nil, control characters in
the buffer are displayed with octal escape sequences, except for newline
and tab. Altering the value of ctl-arrow makes it local to the
current buffer; until that time, the default value is in effect. The
default is initially t. See section `Display Tables' in The Emacs Lisp Reference Manual.
Normally, a tab character in the buffer is displayed as whitespace which
extends to the next display tab stop position, and display tab stops come
at intervals equal to eight spaces. The number of spaces per tab is
controlled by the variable tab-width, which is made local by
changing it, just like ctl-arrow. Note that how the tab character
in the buffer is displayed has nothing to do with the definition of
TAB as a command. The variable tab-width must have an
integer value between 1 and 1000, inclusive.
If the variable truncate-lines is non-nil, then each
line of text gets just one screen line for display; if the text line is
too long, display shows only the part that fits. If
truncate-lines is nil, then long text lines display as
more than one screen line, enough to show the whole text of the line.
See section Continuation Lines. Altering the value of truncate-lines
makes it local to the current buffer; until that time, the default value
is in effect. The default is initially nil.
If the variable truncate-partial-width-windows is
non-nil, it forces truncation rather than continuation in any
window less than the full width of the screen or frame, regardless of
the value of truncate-lines. For information about side-by-side
windows, see section Splitting Windows. See also section `Display' in The Emacs Lisp Reference Manual.
The variable baud-rate holds the output speed of the
terminal, as far as Emacs knows. Setting this variable does not change
the speed of actual data transmission, but the value is used for
calculations such as padding. It also affects decisions about whether
to scroll part of the screen or redraw it instead--even when using a
window system. (We designed it this way, despite the fact that a window
system has no true "output speed," to give you a way to tune these
decisions.)
You can customize the way any particular character code is displayed by means of a display table. See section `Display Tables' in The Emacs Lisp Reference Manual.
Like other editors, Emacs has commands for searching for occurrences of a string. The principal search command is unusual in that it is incremental; it begins to search before you have finished typing the search string. There are also nonincremental search commands more like those of other editors.
Besides the usual replace-string command that finds all
occurrences of one string and replaces them with another, Emacs has a fancy
replacement command called query-replace which asks interactively
which occurrences to replace.
An incremental search begins searching as soon as you type the first character of the search string. As you type in the search string, Emacs shows you where the string (as you have typed it so far) would be found. When you have typed enough characters to identify the place you want, you can stop. Depending on what you plan to do next, you may or may not need to terminate the search explicitly with RET.
isearch-forward).
isearch-backward).
C-s starts an incremental search. C-s reads characters from the keyboard and positions the cursor at the first occurrence of the characters that you have typed. If you type C-s and then F, the cursor moves right after the first `F'. Type an O, and see the cursor move to after the first `FO'. After another O, the cursor is after the first `FOO' after the place where you started the search. At each step, the buffer text that matches the search string is highlighted, if the terminal can do that; at each step, the current search string is updated in the echo area.
If you make a mistake in typing the search string, you can cancel characters with DEL. Each DEL cancels the last character of search string. This does not happen until Emacs is ready to read another input character; first it must either find, or fail to find, the character you want to erase. If you do not want to wait for this to happen, use C-g as described below.
When you are satisfied with the place you have reached, you can type RET, which stops searching, leaving the cursor where the search brought it. Also, any command not specially meaningful in searches stops the searching and is then executed. Thus, typing C-a would exit the search and then move to the beginning of the line. RET is necessary only if the next command you want to type is a printing character, DEL, RET, or another control character that is special within searches (C-q, C-w, C-r, C-s, C-y, M-y, M-r, or M-s).
Sometimes you search for `FOO' and find it, but not the one you expected to find. There was a second `FOO' that you forgot about, before the one you were aiming for. In this event, type another C-s to move to the next occurrence of the search string. This can be done any number of times. If you overshoot, you can cancel some C-s characters with DEL.
After you exit a search, you can search for the same string again by typing just C-s C-s: the first C-s is the key that invokes incremental search, and the second C-s means "search again."
To reuse earlier search strings, use the search ring. The commands M-p and M-n move through the ring to pick a search string to reuse. These commands leave the selected search ring element in the minibuffer, where you can edit it. Type C-s or C-r to terminate editing the string and search for it.
If your string is not found at all, the echo area says `Failing I-Search'. The cursor is after the place where Emacs found as much of your string as it could. Thus, if you search for `FOOT', and there is no `FOOT', you might see the cursor after the `FOO' in `FOOL'. At this point there are several things you can do. If your string was mistyped, you can rub some of it out and correct it. If you like the place you have found, you can type RET or some other Emacs command to "accept what the search offered." Or you can type C-g, which removes from the search string the characters that could not be found (the `T' in `FOOT'), leaving those that were found (the `FOO' in `FOOT'). A second C-g at that point cancels the search entirely, returning point to where it was when the search started.
An upper-case letter in the search string makes the search case-sensitive. If you delete the upper-case character from the search string, it ceases to have this effect. See section Searching and Case.
If a search is failing and you ask to repeat it by typing another C-s, it starts again from the beginning of the buffer. Repeating a failing reverse search with C-r starts again from the end. This is called wrapping around. `Wrapped' appears in the search prompt once this has happened. If you keep on going past the original starting point of the search, it changes to `Overwrapped', which means that you are revisiting matches that you have already seen.
The C-g "quit" character does special things during searches; just what it does depends on the status of the search. If the search has found what you specified and is waiting for input, C-g cancels the entire search. The cursor moves back to where you started the search. If C-g is typed when there are characters in the search string that have not been found--because Emacs is still searching for them, or because it has failed to find them--then the search string characters which have not been found are discarded from the search string. With them gone, the search is now successful and waiting for more input, so a second C-g will cancel the entire search.
To search for a newline, type C-j. To search for another control character, such as control-S or carriage return, you must quote it by typing C-q first. This function of C-q is analogous to its use for insertion (see section Inserting Text): it causes the following character to be treated the way any "ordinary" character is treated in the same context. You can also specify a character by its octal code: enter C-q followed by a sequence of octal digits.
You can change to searching backwards with C-r. If a search fails because the place you started was too late in the file, you should do this. Repeated C-r keeps looking for more occurrences backwards. A C-s starts going forwards again. C-r in a search can be canceled with DEL.
If you know initially that you want to search backwards, you can use
C-r instead of C-s to start the search, because C-r as
a key runs a command (isearch-backward) to search backward. A
backward search finds matches that are entirely before the starting
point, just as a forward search finds matches that begin after it.
The characters C-y and C-w can be used in incremental search to grab text from the buffer into the search string. This makes it convenient to search for another occurrence of text at point. C-w copies the word after point as part of the search string, advancing point over that word. Another C-s to repeat the search will then search for a string including that word. C-y is similar to C-w but copies all the rest of the current line into the search string. Both C-y and C-w convert the text they copy to lower case if the search is currently not case-sensitive; this is so the search remains case-insensitive.
The character M-y copies text from the kill ring into the search string. It uses the same text that C-y as a command would yank. See section Yanking.
When you exit the incremental search, it sets the mark to where point was, before the search. That is convenient for moving back there. In Transient Mark mode, incremental search sets the mark without activating it, and does so only if the mark is not already active.
To customize the special characters that incremental search understands,
alter their bindings in the keymap isearch-mode-map. For a list
of bindings, look at the documentation of isearch-mode with
C-h f isearch-mode RET.
Incremental search on a slow terminal uses a modified style of display that is designed to take less time. Instead of redisplaying the buffer at each place the search gets to, it creates a new single-line window and uses that to display the line that the search has found. The single-line window comes into play as soon as point gets outside of the text that is already on the screen.
When you terminate the search, the single-line window is removed. Then Emacs redisplays the window in which the search was done, to show its new position of point.
The slow terminal style of display is used when the terminal baud rate is
less than or equal to the value of the variable search-slow-speed,
initially 1200.
The number of lines to use in slow terminal search display is controlled
by the variable search-slow-window-lines. Its normal value is 1.
Emacs also has conventional nonincremental search commands, which require you to type the entire search string before searching begins.
To do a nonincremental search, first type C-s RET. This enters the minibuffer to read the search string; terminate the string with RET, and then the search takes place. If the string is not found, the search command gets an error.
The way C-s RET works is that the C-s invokes incremental search, which is specially programmed to invoke nonincremental search if the argument you give it is empty. (Such an empty argument would otherwise be useless.) C-r RET also works this way.
However, nonincremental searches performed using C-s RET do
not call search-forward right away. The first thing done is to see
if the next character is C-w, which requests a word search.
Forward and backward nonincremental searches are implemented by the
commands search-forward and search-backward. These
commands may be bound to keys in the usual manner. The feature that you
can get to them via the incremental search commands exists for
historical reasons, and to avoid the need to find suitable key sequences
for them.
Word search searches for a sequence of words without regard to how the words are separated. More precisely, you type a string of many words, using single spaces to separate them, and the string can be found even if there are multiple spaces, newlines or other punctuation between the words.
Word search is useful for editing a printed document made with a text formatter. If you edit while looking at the printed, formatted version, you can't tell where the line breaks are in the source file. With word search, you can search without having to know them.
Word search is a special case of nonincremental search and is invoked with C-s RET C-w. This is followed by the search string, which must always be terminated with RET. Being nonincremental, this search does not start until the argument is terminated. It works by constructing a regular expression and searching for that; see section Regular Expression Search.
Use C-r RET C-w to do backward word search.
Forward and backward word searches are implemented by the commands
word-search-forward and word-search-backward. These
commands may be bound to keys in the usual manner. The feature that you
can get to them via the incremental search commands exists for historical
reasons, and to avoid the need to find suitable key sequences for them.
A regular expression (regexp, for short) is a pattern that denotes a class of alternative strings to match, possibly infinitely many. In GNU Emacs, you can search for the next match for a regexp either incrementally or not.
Incremental search for a regexp is done by typing C-M-s
(isearch-forward-regexp). This command reads a search string
incrementally just like C-s, but it treats the search string as a
regexp rather than looking for an exact match against the text in the
buffer. Each time you add text to the search string, you make the
regexp longer, and the new regexp is searched for. Invoking C-s
with a prefix argument (its value does not matter) is another way to do
a forward incremental regexp search. To search backward for a regexp,
use C-M-r (isearch-backward-regexp), or C-r with a
prefix argument.
All of the control characters that do special things within an ordinary incremental search have the same function in incremental regexp search. Typing C-s or C-r immediately after starting the search retrieves the last incremental search regexp used; that is to say, incremental regexp and non-regexp searches have independent defaults. They also have separate search rings that you can access with M-p and M-n.
If you type SPC in incremental regexp search, it matches any sequence of whitespace characters, including newlines. If you want to match just a space, type C-q SPC.
Note that adding characters to the regexp in an incremental regexp search can make the cursor move back and start again. For example, if you have searched for `foo' and you add `\|bar', the cursor backs up in case the first `bar' precedes the first `foo'.
Nonincremental search for a regexp is done by the functions
re-search-forward and re-search-backward. You can invoke
these with M-x, or bind them to keys, or invoke them by way of
incremental regexp search with C-M-s RET and C-M-r
RET.
If you use the incremental regexp search commands with a prefix
argument, they perform ordinary string search, like
isearch-forward and isearch-backward. See section Incremental Search.
Regular expressions have a syntax in which a few characters are special constructs and the rest are ordinary. An ordinary character is a simple regular expression which matches that same character and nothing else. The special characters are `$', `^', `.', `*', `+', `?', `[', `]' and `\'. Any other character appearing in a regular expression is ordinary, unless a `\' precedes it.
For example, `f' is not a special character, so it is ordinary, and therefore `f' is a regular expression that matches the string `f' and no other string. (It does not match the string `ff'.) Likewise, `o' is a regular expression that matches only `o'. (When case distinctions are being ignored, these regexps also match `F' and `O', but we consider this a generalization of "the same string," rather than an exception.)
Any two regular expressions a and b can be concatenated. The result is a regular expression which matches a string if a matches some amount of the beginning of that string and b matches the rest of the string.
As a simple example, we can concatenate the regular expressions `f' and `o' to get the regular expression `fo', which matches only the string `fo'. Still trivial. To do something nontrivial, you need to use one of the special characters. Here is a list of them.
grep.
Note: for historical compatibility, special characters are treated as ordinary ones if they are in contexts where their special meanings make no sense. For example, `*foo' treats `*' as ordinary since there is no preceding expression on which the `*' can act. It is poor practice to depend on this behavior; it is better to quote the special character anyway, regardless of where it appears.
For the most part, `\' followed by any character matches only that character. However, there are several exceptions: two-character sequences starting with `\' that have special meanings. The second character in the sequence is always an ordinary character when used on its own. Here is a table of `\' constructs.
The constructs that pertain to words and syntax are controlled by the setting of the syntax table (see section The Syntax Table).
Here is a complicated regexp, used by Emacs to recognize the end of a sentence together with any whitespace that follows. It is given in Lisp syntax to enable you to distinguish the spaces from the tab characters. In Lisp syntax, the string constant begins and ends with a double-quote. `\"' stands for a double-quote as part of the regexp, `\\' for a backslash as part of the regexp, `\t' for a tab and `\n' for a newline.
"[.?!][]\"')]*\\($\\|\t\\| \\)[ \t\n]*"
This contains four parts in succession: a character set matching period, `?', or `!'; a character set matching close-brackets, quotes, or parentheses, repeated any number of times; an alternative in backslash-parentheses that matches end-of-line, a tab, or two spaces; and a character set matching whitespace characters, repeated any number of times.
To enter the same regexp interactively, you would type TAB to enter a tab, and C-j to enter a newline. You would also type single backslashes as themselves, instead of doubling them for Lisp syntax.
Incremental searches in Emacs normally ignore the case of the text they are searching through, if you specify the text in lower case. Thus, if you specify searching for `foo', then `Foo' and `foo' are also considered a match. Regexps, and in particular character sets, are included: `[ab]' would match `a' or `A' or `b' or `B'.
An upper-case letter anywhere in the incremental search string makes the search case-sensitive. Thus, searching for `Foo' does not find `foo' or `FOO'. This applies to regular expression search as well as to string search. The effect ceases if you delete the upper-case letter from the search string.
If you set the variable case-fold-search to nil, then
all letters must match exactly, including case. This is a per-buffer
variable; altering the variable affects only the current buffer, but
there is a default value which you can change as well. See section Local Variables.
This variable applies to nonincremental searches also, including those
performed by the replace commands (see section Replacement Commands) and the minibuffer
history matching commands (see section Minibuffer History).
Global search-and-replace operations are not needed as often in Emacs as they are in other editors(1), but they are available. In addition to the simple M-x replace-string command which is like that found in most editors, there is a M-x query-replace command which asks you, for each occurrence of the pattern, whether to replace it.
The replace commands normally operate on the text from point to the
end of the buffer; however, in Transient Mark mode, when the mark is
active, they operate on the region. The replace commands all replace
one string (or regexp) with one replacement string. It is possible to
perform several replacements in parallel using the command
expand-region-abbrevs (see section Controlling Abbrev Expansion).
To replace every instance of `foo' after point with `bar', use the command M-x replace-string with the two arguments `foo' and `bar'. Replacement happens only in the text after point, so if you want to cover the whole buffer you must go to the beginning first. All occurrences up to the end of the buffer are replaced; to limit replacement to part of the buffer, narrow to that part of the buffer before doing the replacement (see section Narrowing). In Transient Mark mode, when the region is active, replacement is limited to the region (see section Transient Mark Mode).
When replace-string exits, it leaves point at the last
occurrence replaced. It sets the mark to the prior position of point
(where the replace-string command was issued); use C-u
C-SPC to move back there.
A numeric argument restricts replacement to matches that are surrounded by word boundaries. The argument's value doesn't matter.
The M-x replace-string command replaces exact matches for a single string. The similar command M-x replace-regexp replaces any match for a specified pattern.
In replace-regexp, the newstring need not be constant: it
can refer to all or part of what is matched by the regexp.
`\&' in newstring stands for the entire match being replaced.
`\d' in newstring, where d is a digit, stands for
whatever matched the dth parenthesized grouping in regexp.
To include a `\' in the text to replace with, you must enter
`\\'. For example,
M-x replace-regexp RET c[ad]+r RET \&-safe RET
replaces (for example) `cadr' with `cadr-safe' and `cddr' with `cddr-safe'.
M-x replace-regexp RET \(c[ad]+r\)-safe RET \1 RET
performs the inverse transformation.
If the arguments to a replace command are in lower case, it preserves case when it makes a replacement. Thus, the command
M-x replace-string RET foo RET bar RET
replaces a lower case `foo' with a lower case `bar', an
all-caps `FOO' with `BAR', and a capitalized `Foo' with
`Bar'. (These three alternatives--lower case, all caps, and
capitalized, are the only ones that replace-string can
distinguish.)
If upper-case letters are used in the second argument, they remain
upper case every time that argument is inserted. If upper-case letters
are used in the first argument, the second argument is always
substituted exactly as given, with no case conversion. Likewise, if the
variable case-replace is set to nil, replacement is done
without case conversion. If case-fold-search is set to
nil, case is significant in matching occurrences of `foo' to
replace; this also inhibits case conversion of the replacement string.
If you want to change only some of the occurrences of `foo' to
`bar', not all of them, then you cannot use an ordinary
replace-string. Instead, use M-% (query-replace).
This command finds occurrences of `foo' one by one, displays each
occurrence and asks you whether to replace it. A numeric argument to
query-replace tells it to consider only occurrences that are
bounded by word-delimiter characters. This preserves case, just like
replace-string, provided case-replace is non-nil,
as it normally is.
Aside from querying, query-replace works just like
replace-string, and query-replace-regexp works just like
replace-regexp. This command is run by C-M-%.
The things you can type when you are shown an occurrence of string or a match for regexp are:
query-replace, so if you want to do further replacement you
must use C-x ESC ESC RET to restart
(see section Repeating Minibuffer Commands).
query-replace.
Some other characters are aliases for the ones listed above: y, n and q are equivalent to SPC, DEL and RET.
Aside from this, any other character exits the query-replace,
and is then reread as part of a key sequence. Thus, if you type
C-k, it exits the query-replace and then kills to end of
line.
To restart a query-replace once it is exited, use C-x
ESC ESC, which repeats the query-replace because it
used the minibuffer to read its arguments. See section Repeating Minibuffer Commands.
See also section Transforming File Names in Dired, for Dired commands to rename, copy, or link files by replacing regexp matches in file names.
Here are some other commands that find matches for a regular expression. They all operate from point to the end of the buffer.
case-fold-search controls
whether case is ignored.
The buffer `*Occur*' containing the output serves as a menu for
finding the occurrences in their original context. Click Mouse-2
on an occurrence listed in `*Occur*', or position point there and
type RET; this switches to the buffer that was searched and
moves point to the original of the chosen occurrence.
In addition, you can use grep from Emacs to search a collection
of files for matches for a regular expression, then visit the matches
either sequentially or in arbitrary order. See section Searching with Grep under Emacs.
In this chapter we describe the commands that are especially useful for the times when you catch a mistake in your text just after you have made it, or change your mind while composing text on the fly.
The most fundamental command for correcting erroneous editing is the
undo command, C-x u or C-_. This command undoes a single
command (usually), a part of a command (in the case of
query-replace), or several consecutive self-inserting characters.
Consecutive repetitions of C-_ or C-x u undo earlier and
earlier changes, back to the limit of the undo information available.
See section Undoing Changes, for for more information.
delete-backward-char).
backward-kill-word).
backward-kill-sentence).
The DEL character (delete-backward-char) is the most
important correction command. It deletes the character before point.
When DEL follows a self-inserting character command, you can think
of it as canceling that command. However, avoid the mistake of thinking
of DEL as a general way to cancel a command!
When your mistake is longer than a couple of characters, it might be more convenient to use M-DEL or C-x DEL. M-DEL kills back to the start of the last word, and C-x DEL kills back to the start of the last sentence. C-x DEL is particularly useful when you change your mind about the phrasing of the text you are writing. M-DEL and C-x DEL save the killed text for C-y and M-y to retrieve. See section Yanking.
M-DEL is often useful even when you have typed only a few characters wrong, if you know you are confused in your typing and aren't sure exactly what you typed. At such a time, you cannot correct with DEL except by looking at the screen to see what you did. Often it requires less thought to kill the whole word and start again.
transpose-chars).
transpose-words).
transpose-sexps).
transpose-lines).
The common error of transposing two characters can be fixed, when they
are adjacent, with the C-t command (transpose-chars). Normally,
C-t transposes the two characters on either side of point. When
given at the end of a line, rather than transposing the last character of
the line with the newline, which would be useless, C-t transposes the
last two characters on the line. So, if you catch your transposition error
right away, you can fix it with just a C-t. If you don't catch it so
fast, you must move the cursor back to between the two transposed
characters. If you transposed a space with the last character of the word
before it, the word motion commands are a good way of getting there.
Otherwise, a reverse search (C-r) is often the best way.
See section Searching and Replacement.
M-t (transpose-words) transposes the word before point
with the word after point. It moves point forward over a word, dragging
the word preceding or containing point forward as well. The punctuation
characters between the words do not move. For example, `FOO, BAR'
transposes into `BAR, FOO' rather than `BAR FOO,'.
C-M-t (transpose-sexps) is a similar command for transposing
two expressions (see section Lists and Sexps), and C-x C-t (transpose-lines)
exchanges lines. They work like M-t except in determining the
division of the text into syntactic units.
A numeric argument to a transpose command serves as a repeat count: it tells the transpose command to move the character (word, sexp, line) before or containing point across several other characters (words, sexps, lines). For example, C-u 3 C-t moves the character before point forward across three other characters. It would change `f-!-oobar' into `oobf-!-ar'. This is equivalent to repeating C-t three times. C-u - 4 M-t moves the word before point backward across four words. C-u - C-M-t would cancel the effect of plain C-M-t.
A numeric argument of zero is assigned a special meaning (because otherwise a command with a repeat count of zero would do nothing): to transpose the character (word, sexp, line) ending after point with the one ending after the mark.
A very common error is to type words in the wrong case. Because of this, the word case-conversion commands M-l, M-u and M-c have a special feature when used with a negative argument: they do not move the cursor. As soon as you see you have mistyped the last word, you can simply case-convert it and go on typing. See section Case Conversion Commands.
This section describes the commands to check the spelling of a single word or of a portion of a buffer. These commands work with the spelling checker program Ispell, which is not part of Emacs.
ispell-word).
ispell-complete-word).
Flyspell mode is a fully-automatic way to check spelling as you edit in Emacs. It operates by checking words as you change or insert them. When it finds a word that it does not recognize, it highlights that word. This does not interfere with your editing, but when you see the highlighted word, you can move to it and fix it. Type M-x flyspell-mode to enable or disable this mode in the current buffer.
When Flyspell mode highlights a word as misspelled, you can click on it with Mouse-2 to display a menu of possible corrections and actions. You can also correct the word by editing it manually in any way you like.
The other Emacs spell-checking features check or look up words when you give an explicit command to do so. Checking all or part of the buffer is useful when you have text that was written outside of this Emacs session and might contain any number of misspellings.
To check the spelling of the word around or next to point, and
optionally correct it as well, use the command M-$
(ispell-word). If the word is not correct, the command offers
you various alternatives for what to do about it.
To check the entire current buffer, use M-x ispell-buffer. Use M-x ispell-region to check just the current region. To check spelling in an email message you are writing, use M-x ispell-message; that checks the whole buffer, but does not check material that is indented or appears to be cited from other messages.
Each time these commands encounter an incorrect word, they ask you what to do. They display a list of alternatives, usually including several "near-misses"---words that are close to the word being checked. Then you must type a character. Here are the valid responses:
query-replace so you
can replace it elsewhere in the buffer if you wish.
The command ispell-complete-word, which is bound to the key
M-TAB in Text mode and related modes, shows a list of
completions based on spelling correction. Insert the beginning of a
word, and then type M-TAB; the command displays a completion
list window. To choose one of the completions listed, click
Mouse-2 on it, or move the cursor there in the completions window
and type RET. See section Text Mode.
Once started, the Ispell subprocess continues to run (waiting for something to do), so that subsequent spell checking commands complete more quickly. If you want to get rid of the Ispell process, use M-x ispell-kill-ispell. This is not usually necessary, since the process uses no time except when you do spelling correction.
Ispell uses two dictionaries: the standard dictionary and your private
dictionary. The variable ispell-dictionary specifies the file
name of the standard dictionary to use. A value of nil says to
use the default dictionary. The command M-x
ispell-change-dictionary sets this variable and then restarts the
Ispell subprocess, so that it will use a different dictionary.
The operating system stores data permanently in named files. So most of the text you edit with Emacs comes from a file and is ultimately stored in a file.
To edit a file, you must tell Emacs to read the file and prepare a buffer containing a copy of the file's text. This is called visiting the file. Editing commands apply directly to text in the buffer; that is, to the copy inside Emacs. Your changes appear in the file itself only when you save the buffer back into the file.
In addition to visiting and saving files, Emacs can delete, copy, rename, and append to files, keep multiple versions of them, and operate on file directories.
Most Emacs commands that operate on a file require you to specify the file name. (Saving and reverting are exceptions; the buffer knows which file name to use for them.) You enter the file name using the minibuffer (see section The Minibuffer). Completion is available, to make it easier to specify long file names. See section Completion.
For most operations, there is a default file name which is used if you type just RET to enter an empty argument. Normally the default file name is the name of the file visited in the current buffer; this makes it easy to operate on that file with any of the Emacs file commands.
Each buffer has a default directory, normally the same as the
directory of the file visited in that buffer. When you enter a file
name without a directory, the default directory is used. If you specify
a directory in a relative fashion, with a name that does not start with
a slash, it is interpreted with respect to the default directory. The
default directory is kept in the variable default-directory,
which has a separate value in every buffer.
For example, if the default file name is `/u/rms/gnu/gnu.tasks' then the default directory is `/u/rms/gnu/'. If you type just `foo', which does not specify a directory, it is short for `/u/rms/gnu/foo'. `../.login' would stand for `/u/rms/.login'. `new/foo' would stand for the file name `/u/rms/gnu/new/foo'.
The command M-x pwd prints the current buffer's default
directory, and the command M-x cd sets it (to a value read using
the minibuffer). A buffer's default directory changes only when the
cd command is used. A file-visiting buffer's default directory
is initialized to the directory of the file that is visited there. If
you create a buffer with C-x b, its default directory is copied
from that of the buffer that was current at the time.
The default directory actually appears in the minibuffer when the
minibuffer becomes active to read a file name. This serves two
purposes: it shows you what the default is, so that you can type
a relative file name and know with certainty what it will mean, and it
allows you to edit the default to specify a different directory.
This insertion of the default directory is inhibited if the variable
insert-default-directory is set to nil.
Note that it is legitimate to type an absolute file name after you enter the minibuffer, ignoring the presence of the default directory name as part of the text. The final minibuffer contents may look invalid, but that is not so. For example, if the minibuffer starts out with `/usr/tmp/' and you add `/x1/rms/foo', you get `/usr/tmp//x1/rms/foo'; but Emacs ignores everything through the first slash in the double slash; the result is `/x1/rms/foo'. See section Minibuffers for File Names.
`$' in a file name is used to substitute environment variables.
For example, if you have used the shell command `export
FOO=rms/hacks' to set up an environment variable named FOO, then
you can use `/u/$FOO/test.c' or `/u/${FOO}/test.c' as an
abbreviation for `/u/rms/hacks/test.c'. The environment variable
name consists of all the alphanumeric characters after the `$';
alternatively, it may be enclosed in braces after the `$'. Note
that shell commands to set environment variables affect Emacs only if
done before Emacs is started.
To access a file with `$' in its name, type `$$'. This pair is converted to a single `$' at the same time as variable substitution is performed for single `$'. Alternatively, quote the whole file name with `/:' (see section Quoted File Names).
The Lisp function that performs the substitution is called
substitute-in-file-name. The substitution is performed only on
file names read as such using the minibuffer.
You can include non-ASCII characters in file names if you set the
variable file-name-coding-system to a non-nil value.
See section Specifying a Coding System.
find-file).
find-file-read-only).
find-alternate-file).
find-file-other-window). Don't
alter what is displayed in the selected window.
find-file-other-frame). Don't
alter what is displayed in the selected frame.
Visiting a file means copying its contents into an Emacs buffer so you can edit them. Emacs makes a new buffer for each file that you visit. We say that this buffer is visiting the file that it was created to hold. Emacs constructs the buffer name from the file name by throwing away the directory, keeping just the name proper. For example, a file named `/usr/rms/emacs.tex' would get a buffer named `emacs.tex'. If there is already a buffer with that name, a unique name is constructed by appending `<2>', `<3>', or so on, using the lowest number that makes a name that is not already in use.
Each window's mode line shows the name of the buffer that is being displayed in that window, so you can always tell what buffer you are editing.
The changes you make with editing commands are made in the Emacs buffer. They do not take effect in the file that you visited, or any place permanent, until you save the buffer. Saving the buffer means that Emacs writes the current contents of the buffer into its visited file. See section Saving Files.
If a buffer contains changes that have not been saved, we say the buffer is modified. This is important because it implies that some changes will be lost if the buffer is not saved. The mode line displays two stars near the left margin to indicate that the buffer is modified.
To visit a file, use the command C-x C-f (find-file). Follow
the command with the name of the file you wish to visit, terminated by a
RET.
The file name is read using the minibuffer (see section The Minibuffer), with defaulting and completion in the standard manner (see section File Names). While in the minibuffer, you can abort C-x C-f by typing C-g.
Your confirmation that C-x C-f has completed successfully is the appearance of new text on the screen and a new buffer name in the mode line. If the specified file does not exist and could not be created, or cannot be read, then you get an error, with an error message displayed in the echo area.
If you visit a file that is already in Emacs, C-x C-f does not make another copy. It selects the existing buffer containing that file. However, before doing so, it checks that the file itself has not changed since you visited or saved it last. If the file has changed, a warning message is printed. See section Protection against Simultaneous Editing.
What if you want to create a new file? Just visit it. Emacs prints `(New File)' in the echo area, but in other respects behaves as if you had visited an existing empty file. If you make any changes and save them, the file is created.
If the file you specify is actually a directory, C-x C-f invokes
Dired, the Emacs directory browser, so that you can "edit" the contents
of the directory (see section Dired, the Directory Editor). Dired is a convenient way to delete,
look at, or operate on the files in the directory. However, if the
variable find-file-run-dired is nil, then it is an error
to try to visit a directory.
If you visit a file that the operating system won't let you modify,
Emacs makes the buffer read-only, so that you won't go ahead and make
changes that you'll have trouble saving afterward. You can make the
buffer writable with C-x C-q (vc-toggle-read-only).
See section Miscellaneous Buffer Operations.
Occasionally you might want to visit a file as read-only in order to
protect yourself from entering changes accidentally; do so by visiting
the file with the command C-x C-r (find-file-read-only).
If you visit a nonexistent file unintentionally (because you typed the
wrong file name), use the C-x C-v command
(find-alternate-file) to visit the file you really wanted.
C-x C-v is similar to C-x C-f, but it kills the current
buffer (after first offering to save it if it is modified). When it
reads the file name to visit, it inserts the entire default file name in
the buffer, with point just after the directory part; this is convenient
if you made a slight error in typing the name.
If you find a file which exists but cannot be read, C-x C-f signals an error.
C-x 4 f (find-file-other-window) is like C-x C-f
except that the buffer containing the specified file is selected in another
window. The window that was selected before C-x 4 f continues to
show the same buffer it was already showing. If this command is used when
only one window is being displayed, that window is split in two, with one
window showing the same buffer as before, and the other one showing the
newly requested file. See section Multiple Windows.
C-x 5 f (find-file-other-frame) is similar, but opens a
new frame, or makes visible any existing frame showing the file you
seek. This feature is available only when you are using a window
system. See section Frames and X Windows.
If you wish to edit a file as a sequence of characters with no special encoding or conversion, use the M-x find-file-literally command. It visits a file, like C-x C-f, but does not do format conversion (see section Editing Formatted Text), character code conversion (see section Coding Systems), or automatic uncompression (see section Accessing Compressed Files). If you already have visited the same file in the usual (non-literal) manner, this command asks you whether to visit it literally instead.
Two special hook variables allow extensions to modify the operation of
visiting files. Visiting a file that does not exist runs the functions
in the list find-file-not-found-hooks; this variable holds a list
of functions, and the functions are called one by one until one of them
returns non-nil. Any visiting of a file, whether extant or not,
expects find-file-hooks to contain a list of functions and calls
them all, one by one. In both cases the functions receive no
arguments. Of these two variables, find-file-not-found-hooks
takes effect first. These variables are not normal hooks, and
their names end in `-hooks' rather than `-hook' to indicate
that fact. See section Hooks.
There are several ways to specify automatically the major mode for editing the file (see section How Major Modes are Chosen), and to specify local variables defined for that file (see section Local Variables in Files).
Saving a buffer in Emacs means writing its contents back into the file that was visited in the buffer.
save-buffer).
save-some-buffers).
not-modified).
write-file).
When you wish to save the file and make your changes permanent, type
C-x C-s (save-buffer). After saving is finished, C-x C-s
displays a message like this:
Wrote /u/rms/gnu/gnu.tasks
If the selected buffer is not modified (no changes have been made in it since the buffer was created or last saved), saving is not really done, because it would have no effect. Instead, C-x C-s displays a message like this in the echo area:
(No changes need to be saved)
The command C-x s (save-some-buffers) offers to save any
or all modified buffers. It asks you what to do with each buffer. The
possible responses are analogous to those of query-replace:
save-some-buffers without any more saving.
save-some-buffers without even asking
about other buffers.
save-some-buffers, which asks the
question again.
C-x C-c, the key sequence to exit Emacs, invokes
save-some-buffers and therefore asks the same questions.
If you have changed a buffer but you do not want to save the changes,
you should take some action to prevent it. Otherwise, each time you use
C-x s or C-x C-c, you are liable to save this buffer by
mistake. One thing you can do is type M-~ (not-modified),
which clears out the indication that the buffer is modified. If you do
this, none of the save commands will believe that the buffer needs to be
saved. (`~' is often used as a mathematical symbol for `not'; thus
M-~ is `not', metafied.) You could also use
set-visited-file-name (see below) to mark the buffer as visiting
a different file name, one which is not in use for anything important.
Alternatively, you can cancel all the changes made since the file was
visited or saved, by reading the text from the file again. This is
called reverting. See section Reverting a Buffer. You could also undo all the
changes by repeating the undo command C-x u until you have undone
all the changes; but reverting is easier.
M-x set-visited-file-name alters the name of the file that the
current buffer is visiting. It reads the new file name using the
minibuffer. Then it specifies the visited file name and changes the
buffer name correspondingly (as long as the new name is not in use).
set-visited-file-name does not save the buffer in the newly
visited file; it just alters the records inside Emacs in case you do
save later. It also marks the buffer as "modified" so that C-x
C-s in that buffer will save.
If you wish to mark the buffer as visiting a different file and save it
right away, use C-x C-w (write-file). It is precisely
equivalent to set-visited-file-name followed by C-x C-s.
C-x C-s used on a buffer that is not visiting a file has the
same effect as C-x C-w; that is, it reads a file name, marks the
buffer as visiting that file, and saves it there. The default file name in
a buffer that is not visiting a file is made by combining the buffer name
with the buffer's default directory.
If the new file name implies a major mode, then C-x C-w switches
to that major mode, in most cases. The command
set-visited-file-name also does this. See section How Major Modes are Chosen.
If Emacs is about to save a file and sees that the date of the latest version on disk does not match what Emacs last read or wrote, Emacs notifies you of this fact, because it probably indicates a problem caused by simultaneous editing and requires your immediate attention. See section Protection against Simultaneous Editing.
If the variable require-final-newline is non-nil, Emacs
puts a newline at the end of any file that doesn't already end in one,
every time a file is saved or written. The default is nil.
On most operating systems, rewriting a file automatically destroys all
record of what the file used to contain. Thus, saving a file from Emacs
throws away the old contents of the file--or it would, except that
Emacs carefully copies the old contents to another file, called the
backup file, before actually saving. (This assumes that the
variable make-backup-files is non-nil. Backup files are
not written if this variable is nil.) Emacs does not normally
make backup files for files in `/tmp'.
At your option, Emacs can keep either a single backup file or a series of numbered backup files for each file that you edit.
Emacs makes a backup for a file only the first time the file is saved from one buffer. No matter how many times you save a file, its backup file continues to contain the contents from before the file was visited. Normally this means that the backup file contains the contents from before the current editing session; however, if you kill the buffer and then visit the file again, a new backup file will be made by the next save.
You can also explicitly request making another backup file from a buffer even though it has already been saved at least once. If you save the buffer with C-u C-x C-s, the version thus saved will be made into a backup file if you save the buffer again. C-u C-u C-x C-s saves the buffer, but first makes the previous file contents into a new backup file. C-u C-u C-u C-x C-s does both things: it makes a backup from the previous contents, and arranges to make another from the newly saved contents, if you save again.
If you choose to have a single backup file (this is the default), the backup file's name is constructed by appending `~' to the file name being edited; thus, the backup file for `eval.c' would be `eval.c~'.
If you choose to have a series of numbered backup files, backup file names are made by appending `.~', the number, and another `~' to the original file name. Thus, the backup files of `eval.c' would be called `eval.c.~1~', `eval.c.~2~', and so on, through names like `eval.c.~259~' and beyond.
If protection stops you from writing backup files under the usual names, the backup file is written as `%backup%~' in your home directory. Only one such file can exist, so only the most recently made such backup is available.
The choice of single backup or numbered backups is controlled by the
variable version-control. Its possible values are
t
nil
never
You can set version-control locally in an individual buffer to
control the making of backups for that buffer's file. For example,
Rmail mode locally sets version-control to never to make sure
that there is only one backup for an Rmail file. See section Local Variables.
If you set the environment variable VERSION_CONTROL, to tell
various GNU utilities what to do with backup files, Emacs also obeys the
environment variable by setting the Lisp variable version-control
accordingly at startup. If the environment variable's value is `t'
or `numbered', then version-control becomes t; if the
value is `nil' or `existing', then version-control
becomes nil; if it is `never' or `simple', then
version-control becomes never.
For files managed by a version control system (see section Version Control), the variable vc-make-backup-files determines whether
to make backup files. By default, it is nil, since backup files
are redundant when you store all the previous versions in a version
control system. See section VC Workfile Handling.
To prevent unlimited consumption of disk space, Emacs can delete numbered backup versions automatically. Generally Emacs keeps the first few backups and the latest few backups, deleting any in between. This happens every time a new backup is made.
The two variables kept-old-versions and
kept-new-versions control this deletion. Their values are,
respectively the number of oldest (lowest-numbered) backups to keep and
the number of newest (highest-numbered) ones to keep, each time a new
backup is made. Recall that these values are used just after a new
backup version is made; that newly made backup is included in the count
in kept-new-versions. By default, both variables are 2.
If delete-old-versions is non-nil, the excess
middle versions are deleted without a murmur. If it is nil, the
default, then you are asked whether the excess middle versions should
really be deleted.
Dired's . (Period) command can also be used to delete old versions. See section Deleting Files with Dired.
Backup files can be made by copying the old file or by renaming it. This makes a difference when the old file has multiple names. If the old file is renamed into the backup file, then the alternate names become names for the backup file. If the old file is copied instead, then the alternate names remain names for the file that you are editing, and the contents accessed by those names will be the new contents.
The method of making a backup file may also affect the file's owner and group. If copying is used, these do not change. If renaming is used, you become the file's owner, and the file's group becomes the default (different operating systems have different defaults for the group).
Having the owner change is usually a good idea, because then the owner
always shows who last edited the file. Also, the owners of the backups
show who produced those versions. Occasionally there is a file whose
owner should not change; it is a good idea for such files to contain
local variable lists to set backup-by-copying-when-mismatch
locally (see section Local Variables in Files).
The choice of renaming or copying is controlled by three variables.
Renaming is the default choice. If the variable
backup-by-copying is non-nil, copying is used. Otherwise,
if the variable backup-by-copying-when-linked is non-nil,
then copying is used for files that have multiple names, but renaming
may still be used when the file being edited has only one name. If the
variable backup-by-copying-when-mismatch is non-nil, then
copying is used if renaming would cause the file's owner or group to
change. backup-by-copying-when-mismatch is t by default
if you start Emacs as the superuser.
When a file is managed with a version control system (see section Version Control), Emacs does not normally make backups in the usual way for that file. But check-in and check-out are similar in some ways to making backups. One unfortunate similarity is that these operations typically break hard links, disconnecting the file name you visited from any alternate names for the same file. This has nothing to do with Emacs--the version control system does it.
Simultaneous editing occurs when two users visit the same file, both make changes, and then both save them. If nobody were informed that this was happening, whichever user saved first would later find that his changes were lost.
On some systems, Emacs notices immediately when the second user starts to change the file, and issues an immediate warning. On all systems, Emacs checks when you save the file, and warns if you are about to overwrite another user's changes. You can prevent loss of the other user's work by taking the proper corrective action instead of saving the file.
When you make the first modification in an Emacs buffer that is visiting a file, Emacs records that the file is locked by you. (It does this by creating a symbolic link in the same directory with a different name.) Emacs removes the lock when you save the changes. The idea is that the file is locked whenever an Emacs buffer visiting it has unsaved changes.
If you begin to modify the buffer while the visited file is locked by
someone else, this constitutes a collision. When Emacs detects a
collision, it asks you what to do, by calling the Lisp function
ask-user-about-lock. You can redefine this function for the sake
of customization. The standard definition of this function asks you a
question and accepts three possible answers:
file-locked) and the modification you
were trying to make in the buffer does not actually take place.
Note that locking works on the basis of a file name; if a file has multiple names, Emacs does not realize that the two names are the same file and cannot prevent two users from editing it simultaneously under different names. However, basing locking on names means that Emacs can interlock the editing of new files that will not really exist until they are saved.
Some systems are not configured to allow Emacs to make locks, and there are cases where lock files cannot be written. In these cases, Emacs cannot detect trouble in advance, but it still can detect the collision when you try to save a file and overwrite someone else's changes.
If Emacs or the operating system crashes, this may leave behind lock files which are stale. So you may occasionally get warnings about spurious collisions. When you determine that the collision is spurious, just use p to tell Emacs to go ahead anyway.
Every time Emacs saves a buffer, it first checks the last-modification date of the existing file on disk to verify that it has not changed since the file was last visited or saved. If the date does not match, it implies that changes were made in the file in some other way, and these changes are about to be lost if Emacs actually does save. To prevent this, Emacs prints a warning message and asks for confirmation before saving. Occasionally you will know why the file was changed and know that it does not matter; then you can answer yes and proceed. Otherwise, you should cancel the save with C-g and investigate the situation.
The first thing you should do when notified that simultaneous editing
has already taken place is to list the directory with C-u C-x C-d
(see section File Directories). This shows the file's current author. You
should attempt to contact him to warn him not to continue editing.
Often the next step is to save the contents of your Emacs buffer under a
different name, and use diff to compare the two files.
If you have made extensive changes to a file and then change your mind about them, you can get rid of them by reading in the previous version of the file. To do this, use M-x revert-buffer, which operates on the current buffer. Since reverting a buffer unintentionally could lose a lot of work, you must confirm this command with yes.
revert-buffer keeps point at the same distance (measured in
characters) from the beginning of the file. If the file was edited only
slightly, you will be at approximately the same piece of text after
reverting as before. If you have made drastic changes, the same value of
point in the old file may address a totally different piece of text.
Reverting marks the buffer as "not modified" until another change is made.
Some kinds of buffers whose contents reflect data bases other than files,
such as Dired buffers, can also be reverted. For them, reverting means
recalculating their contents from the appropriate data base. Buffers
created explicitly with C-x b cannot be reverted; revert-buffer
reports an error when asked to do so.
When you edit a file that changes automatically and frequently--for example, a log of output from a process that continues to run--it may be useful for Emacs to revert the file without querying you, whenever you visit the file again with C-x C-f.
To request this behavior, set the variable revert-without-query
to a list of regular expressions. When a file name matches one of these
regular expressions, find-file and revert-buffer will
revert it automatically if it has changed--provided the buffer itself
is not modified. (If you have edited the text, it would be wrong to
discard your changes.)
Emacs saves all the visited files from time to time (based on counting your keystrokes) without being asked. This is called auto-saving. It prevents you from losing more than a limited amount of work if the system crashes.
When Emacs determines that it is time for auto-saving, each buffer is considered, and is auto-saved if auto-saving is turned on for it and it has been changed since the last time it was auto-saved. The message `Auto-saving...' is displayed in the echo area during auto-saving, if any files are actually auto-saved. Errors occurring during auto-saving are caught so that they do not interfere with the execution of commands you have been typing.
Auto-saving does not normally save in the files that you visited, because it can be very undesirable to save a program that is in an inconsistent state when you have made half of a planned change. Instead, auto-saving is done in a different file called the auto-save file, and the visited file is changed only when you request saving explicitly (such as with C-x C-s).
Normally, the auto-save file name is made by appending `#' to the
front and rear of the visited file name. Thus, a buffer visiting file
`foo.c' is auto-saved in a file `#foo.c#'. Most buffers that
are not visiting files are auto-saved only if you request it explicitly;
when they are auto-saved, the auto-save file name is made by appending
`#%' to the front and `#' to the rear of buffer name. For
example, the `*mail*' buffer in which you compose messages to be
sent is auto-saved in a file named `#%*mail*#'. Auto-save file
names are made this way unless you reprogram parts of Emacs to do
something different (the functions make-auto-save-file-name and
auto-save-file-name-p). The file name to be used for auto-saving
in a buffer is calculated when auto-saving is turned on in that buffer.
When you delete a substantial part of the text in a large buffer, auto save turns off temporarily in that buffer. This is because if you deleted the text unintentionally, you might find the auto-save file more useful if it contains the deleted text. To reenable auto-saving after this happens, save the buffer with C-x C-s, or use C-u 1 M-x auto-save.
If you want auto-saving to be done in the visited file, set the variable
auto-save-visited-file-name to be non-nil. In this mode,
there is really no difference between auto-saving and explicit saving.
A buffer's auto-save file is deleted when you save the buffer in its
visited file. To inhibit this, set the variable delete-auto-save-files
to nil. Changing the visited file name with C-x C-w or
set-visited-file-name renames any auto-save file to go with
the new visited name.
Each time you visit a file, auto-saving is turned on for that file's
buffer if the variable auto-save-default is non-nil (but not
in batch mode; see section Entering and Exiting Emacs). The default for this variable is
t, so auto-saving is the usual practice for file-visiting buffers.
Auto-saving can be turned on or off for any existing buffer with the
command M-x auto-save-mode. Like other minor mode commands, M-x
auto-save-mode turns auto-saving on with a positive argument, off with a
zero or negative argument; with no argument, it toggles.
Emacs does auto-saving periodically based on counting how many characters
you have typed since the last time auto-saving was done. The variable
auto-save-interval specifies how many characters there are between
auto-saves. By default, it is 300.
Auto-saving also takes place when you stop typing for a while. The
variable auto-save-timeout says how many seconds Emacs should
wait before it does an auto save (and perhaps also a garbage
collection). (The actual time period is longer if the current buffer is
long; this is a heuristic which aims to keep out of your way when you
are editing long buffers, in which auto-save takes an appreciable amount
of time.) Auto-saving during idle periods accomplishes two things:
first, it makes sure all your work is saved if you go away from the
terminal for a while; second, it may avoid some auto-saving while you
are actually typing.
Emacs also does auto-saving whenever it gets a fatal error. This includes killing the Emacs job with a shell command such as `kill %emacs', or disconnecting a phone line or network connection.
You can request an auto-save explicitly with the command M-x do-auto-save.
You can use the contents of an auto-save file to recover from a loss of data with the command M-x recover-file RET file RET. This visits file and then (after your confirmation) restores the contents from its auto-save file `#file#'. You can then save with C-x C-s to put the recovered text into file itself. For example, to recover file `foo.c' from its auto-save file `#foo.c#', do:
M-x recover-file RET foo.c RET yes RET C-x C-s
Before asking for confirmation, M-x recover-file displays a directory listing describing the specified file and the auto-save file, so you can compare their sizes and dates. If the auto-save file is older, M-x recover-file does not offer to read it.
If Emacs or the computer crashes, you can recover all the files you were editing from their auto save files with the command M-x recover-session. This first shows you a list of recorded interrupted sessions. Move point to the one you choose, and type C-c C-c.
Then recover-session asks about each of the files that were
being edited during that session, asking whether to recover that file.
If you answer y, it calls recover-file, which works in its
normal fashion. It shows the dates of the original file and its
auto-save file, and asks once again whether to recover that file.
When recover-session is done, the files you've chosen to
recover are present in Emacs buffers. You should then save them. Only
this--saving them--updates the files themselves.
Interrupted sessions are recorded for later recovery in files named
`~/.saves-pid-hostname'. The `~/.saves' portion of
these names comes from the value of auto-save-list-file-prefix.
You can arrange to record sessions in a different place by setting that
variable in your `.emacs' file, but you'll have to redefine
recover-session as well to make it look in the new place. If you
set auto-save-list-file-prefix to nil in your
`.emacs' file, sessions are not recorded for recovery.
Symbolic links and hard links both make it possible for several file names to refer to the same file. Hard links are alternate names that refer directly to the file; all the names are equally valid, and no one of them is preferred. By contrast, a symbolic link is a kind of defined alias: when `foo' is a symbolic link to `bar', you can use either name to refer to the file, but `bar' is the real name, while `foo' is just an alias. More complex cases occur when symbolic links point to directories.
If you visit two names for the same file, normally Emacs makes two different buffers, but it warns you about the situation.
If you wish to avoid visiting the same file in two buffers under
different names, set the variable find-file-existing-other-name
to a non-nil value. Then find-file uses the existing
buffer visiting the file, no matter which of the file's names you
specify.
If the variable find-file-visit-truename is non-nil,
then the file name recorded for a buffer is the file's truename
(made by replacing all symbolic links with their target names), rather
than the name you specify. Setting find-file-visit-truename also
implies the effect of find-file-existing-other-name.
Version control systems are packages that can record multiple versions of a source file, usually storing the unchanged parts of the file just once. Version control systems also record history information such as the creation time of each version, who created it, and a description of what was changed in that version.
The Emacs version control interface is called VC. Its commands work with three version control systems--RCS, CVS and SCCS. The GNU project recommends RCS and CVS, which are free software and available from the Free Software Foundation.
VC allows you to use a version control system from within Emacs, integrating the version control operations smoothly with editing. VC provides a uniform interface to version control, so that regardless of which version control system is in use, you can use it the same way.
This section provides a general overview of version control, and describes the version control systems that VC supports. You can skip this section if you are already familiar with the version control system you want to use.
VC currently works with three different version control systems or "back ends": RCS, CVS, and SCCS.
RCS is a free version control system that is available from the Free Software Foundation. It is perhaps the most mature of the supported back ends, and the VC commands are conceptually closest to RCS. Almost everything you can do with RCS can be done through VC.
CVS is built on top of RCS, and extends the features of RCS, allowing for more sophisticated release management, and concurrent multi-user development. VC supports basic editing operations under CVS, but for some less common tasks you still need to call CVS from the command line. Note also that before using CVS you must set up a repository, which is a subject too complex to treat here.
SCCS is a proprietary but widely used version control system. In terms of capabilities, it is the weakest of the three that VC supports. VC compensates for certain features missing in SCCS (snapshots, for example) by implementing them itself, but some other VC features, such as multiple branches, are not available with SCCS. You should use SCCS only if for some reason you cannot use RCS.
When a file is under version control, we also say that it is registered in the version control system. Each registered file has a corresponding master file which represents the file's present state plus its change history--enough to reconstruct the current version or any earlier version. Usually the master file also records a log entry for each version, describing in words what was changed in that version.
The file that is maintained under version control is sometimes called the work file corresponding to its master file. You edit the work file and make changes in it, as you would with an ordinary file. (With SCCS and RCS, you must lock the file before you start to edit it.) After you are done with a set of changes, you check the file in, which records the changes in the master file, along with a log entry for them.
With CVS, there are usually multiple work files corresponding to a single master file--often each user has his own copy. It is also possible to use RCS in this way, but this is not the usual way to use RCS.
A version control system typically has some mechanism to coordinate between users who want to change the same file. One method is locking (analogous to the locking that Emacs uses to detect simultaneous editing of a file, but distinct from it). The other method is to merge your changes with other people's changes when you check them in.
With version control locking, work files are normally read-only so that you cannot change them. You ask the version control system to make a work file writable for you by locking it; only one user can do this at any given time. When you check in your changes, that unlocks the file, making the work file read-only again. This allows other users to lock the file to make further changes. SCCS always uses locking, and RCS normally does.
The other alternative for RCS is to let each user modify the work file at any time. In this mode, locking is not required, but it is permitted; check-in is still the way to record a new version.
CVS normally allows each user to modify his own copy of the work file at any time, but requires merging with changes from other users at check-in time. However, CVS can also be set up to require locking. (see section Options for VC Backends).
When you visit a file that is under version control, Emacs indicates this on the mode line. For example, `RCS-1.3' says that RCS is used for that file, and the current version is 1.3.
The character between the back-end name and the version number indicates the version control status of the file. `-' means that the work file is not locked (if locking is in use), or not modified (if locking is not in use). `:' indicates that the file is locked, or that it is modified. If the file is locked by some other user (for instance, `jim'), that is displayed as `RCS:jim:1.3'.
The principal VC command is an all-purpose command that performs either locking or check-in, depending on the situation.
Strictly speaking, the command for this job is vc-next-action,
bound to C-x v v. However, the normal meaning of C-x C-q is
to make a read-only buffer writable, or vice versa; we have extended it
to do the same job properly for files managed by version control, by
performing the appropriate version control operations. When you type
C-x C-q on a registered file, it acts like C-x v v.
The precise action of this command depends on the state of the file, and whether the version control system uses locking or not. SCCS and RCS normally use locking; CVS normally does not use locking.
If locking is used for the file (as with SCCS, and RCS in its default mode), C-x C-q can either lock a file or check it in:
These rules also apply when you use CVS in locking mode, except that there is no such thing as stealing a lock.
When there is no locking--the default for CVS--work files are always writable; you do not need to do anything before you begin to edit a file. The status indicator on the mode line is `-' if the file is unmodified; it flips to `:' as soon as you save any changes in the work file.
Here is what C-x C-q does when using CVS:
These rules also apply when you use RCS in the mode that does not require locking, except that automatic merging of changes from the master file is not implemented. Unfortunately, this means that nothing informs you if another user has checked in changes in the same file since you began editing it, and when this happens, his changes will be effectively removed when you check in your version (though they will remain in the master file, so they will not be entirely lost). You must therefore verify the current version is unchanged, before you check in your changes. We hope to eliminate this risk and provide automatic merging with RCS in a future Emacs version.
In addition, locking is possible with RCS even in this mode, although it is not required; C-x C-q with an unmodified file locks the file, just as it does with RCS in its normal (locking) mode.
When you check in changes, C-x C-q first reads a log entry. It pops up a buffer called `*VC-Log*' for you to enter the log entry. When you are finished, type C-c C-c in the `*VC-Log*' buffer. That is when check-in really happens.
To abort check-in, just don't type C-c C-c in that buffer. You can switch buffers and do other editing. As long as you don't try to check in another file, the entry you were editing remains in the `*VC-Log*' buffer, and you can go back to that buffer at any time to complete the check-in.
If you change several source files for the same reason, it is often convenient to specify the same log entry for many of the files. To do this, use the history of previous log entries. The commands M-n, M-p, M-s and M-r for doing this work just like the minibuffer history commands (except that these versions are used outside the minibuffer).
Each time you check in a file, the log entry buffer is put into VC Log
mode, which involves running two hooks: text-mode-hook and
vc-log-mode-hook. See section Hooks.
One of the convenient features of version control is the ability to examine any version of a file, or compare two versions.
To examine an old version in toto, visit the file and then type
C-x v ~ version RET (vc-version-other-window).
This puts the text of version version in a file named
`filename.~version~', and visits it in its own buffer
in a separate window. (In RCS, you can also select an old version
and create a branch from it. See section Multiple Branches of a File.)
But usually it is more convenient to compare two versions of the file,
with the command C-x v = (vc-diff). Plain C-x v =
compares the current buffer contents (saving them in the file if
necessary) with the last checked-in version of the file. C-u C-x v
=, with a numeric argument, reads a file name and two version numbers,
then compares those versions of the specified file.
If you supply a directory name instead of the name of a registered file, this command compares the two specified versions of all registered files in that directory and its subdirectories.
You can specify a checked-in version by its number; an empty input specifies the current contents of the work file (which may be different from all the checked-in versions). You can also specify a snapshot name (see section Snapshots) instead of one or both version numbers.
This command works by running the diff utility, getting the
options from the variable diff-switches. It displays the output
in a special buffer in another window. Unlike the M-x diff
command, C-x v = does not try to locate the changes in the old and
new versions. This is because normally one or both versions do not
exist as files when you compare them; they exist only in the records of
the master file. See section Comparing Files, for more information about
M-x diff.
For CVS-controlled files, you can display the result of the CVS annotate command, using colors to enhance the visual appearance. Use the command M-x vc-annotate to do this. Red means new, blue means old, and intermediate colors indicate intermediate ages. A prefix argument n specifies a stretch factor for the time scale; it makes each color cover a period n times as long.
This section explains the secondary commands of VC; those that you might use once a day.
You can put any file under version control by simply visiting it, and
then typing C-x v i (vc-register).
To register the file, Emacs must choose which version control system
to use for it. You can specify your choice explicitly by setting
vc-default-back-end to RCS, CVS or SCCS.
Otherwise, if there is a subdirectory named `RCS', `SCCS', or
`CVS', Emacs uses the corresponding version control system. In the
absence of any specification, the default choice is RCS if RCS is
installed, otherwise SCCS.
If locking is in use,C-x v i leaves the file unlocked and read-only. Type C-x C-q if you wish to start editing it. After registering a file with CVS, you must subsequently commit the initial version by typing C-x C-q.
The initial version number for a newly registered file is 1.1, by
default. You can specify a different default by setting the variable
vc-default-init-version, or you can give C-x v i a numeric
argument; then it reads the initial version number for this particular
file using the minibuffer.
If vc-initial-comment is non-nil, C-x v i reads an
initial comment to describe the purpose of this source file. Reading
the initial comment works like reading a log entry (see section Features of the Log Entry Buffer).
To view the detailed version control status and history of a file,
type C-x v l (vc-print-log). It displays the history of
changes to the current file, including the text of the log entries. The
output appears in a separate window.
If you want to discard your current set of changes and revert to the
last version checked in, use C-x v u (vc-revert-buffer).
This leaves the file unlocked; if locking is in use, you must first lock
the file again before you change it again. C-x v u requires
confirmation, unless it sees that you haven't made any changes since the
last checked-in version.
C-x v u is also the command to unlock a file if you lock it and then decide not to change it.
To cancel a change that you already checked in, use C-x v c
(vc-cancel-version). This command discards all record of the
most recent checked-in version. C-x v c also offers to revert
your work file and buffer to the previous version (the one that precedes
the version that is deleted).
If you answer no, VC keeps your changes in the buffer, and locks the file. The no-revert option is useful when you have checked in a change and then discover a trivial error in it; you can cancel the erroneous check-in, fix the error, and check the file in again.
When C-x v c does not revert the buffer, it unexpands all version control headers in the buffer instead (see section Inserting Version Control Headers). This is because the buffer no longer corresponds to any existing version. If you check it in again, the check-in process will expand the headers properly for the new version number.
However, it is impossible to unexpand the RCS `$Log: GNU_Emacs_Documentation.html,v $ However, it is impossible to unexpand the RCS `Revision 1.1.1.1 2001/04/25 01:10:05 dgraver However, it is impossible to unexpand the RCS `HELP DOCS However, it is impossible to unexpand the RCS ` However, it is impossible to unexpand the RCS `Revision 1.1 2001/04/17 22:16:11 dgraver However, it is impossible to unexpand the RCS `added real sports table and edited fantasy table However, it is impossible to unexpand the RCS ` However, it is impossible to unexpand the RCS `Revision 1.1.1.1 2001/03/12 20:02:47 dgraver However, it is impossible to unexpand the RCS `public_html cvs start However, it is impossible to unexpand the RCS `' header automatically. If you use that header feature, you have to unexpand it by hand--by deleting the entry for the version that you just canceled.
Be careful when invoking C-x v c, as it is easy to lose a lot of work with it. To help you be careful, this command always requires confirmation with yes. Note also that this command is disabled under CVS, because canceling versions is very dangerous and discouraged with CVS.
When you are working on a large program, it is often useful to find
out which files have changed within an entire directory tree, or to view
the status of all files under version control at once, and to perform
version control operations on collections of files. You can use the
command C-x v d (vc-directory) to make a directory listing
that includes only files relevant for version control.
C-x v d creates a buffer which uses VC Dired Mode. This looks
much like an ordinary Dired buffer (see section Dired, the Directory Editor); however, normally it
shows only the noteworthy files (those locked or not up-to-date). This
is called terse display. If you set the variable
vc-dired-terse-display to nil, then VC Dired shows all
relevant files--those managed under version control, plus all
subdirectories (full display). The command v t in a VC
Dired buffer toggles between terse display and full display (see section VC Dired Commands).
By default, VC Dired produces a recursive listing of noteworthy or
relevant files at or below the given directory. You can change this by
setting the variable vc-dired-recurse to nil; then VC
Dired shows only the files in the given directory.
The line for an individual file shows the version control state in the place of the hard link count, owner, group, and size of the file. If the file is unmodified, in sync with the master file, the version control state shown is blank. Otherwise it consists of text in parentheses. Under RCS and SCCS, the name of the user locking the file is shown; under CVS, an abbreviated version of the `cvs status' output is used. Here is an example using RCS:
/home/jim/project: -rw-r--r-- (jim) Apr 2 23:39 file1 -r--r--r-- Apr 5 20:21 file2
The files `file1' and `file2' are under version control, `file1' is locked by user jim, and `file2' is unlocked.
Here is an example using CVS:
/home/joe/develop: -rw-r--r-- (modified) Aug 2 1997 file1.c -rw-r--r-- Apr 4 20:09 file2.c -rw-r--r-- (merge) Sep 13 1996 file3.c
Here `file1.c' is modified with respect to the repository, and `file2.c' is not. `file3.c' is modified, but other changes have also been checked in to the repository--you need to merge them with the work file before you can check it in.
When VC Dired displays subdirectories (in the "full" display mode),
it omits some that should never contain any files under version control.
By default, this includes Version Control subdirectories such as
`RCS' and `CVS'; you can customize this by setting the
variable vc-directory-exclusion-list.
You can fine-tune VC Dired's format by typing C-u x v d---as in ordinary Dired, that allows you to specify additional switches for the `ls' command.
All the usual Dired commands work normally in VC Dired mode, except
for v, which is redefined as the version control prefix. You can
invoke VC commands such as vc-diff and vc-print-log by
typing v =, or v l, and so on. Most of these commands apply
to the file name on the current line.
The command v v (vc-next-action) operates on all the
marked files, so that you can lock or check in several files at once.
If it operates on more than one file, it handles each file according to
its current state; thus, it might lock one file, but check in another
file. This could be confusing; it is up to you to avoid confusing
behavior by marking a set of files that are in a similar state.
If any files call for check-in, v v reads a single log entry, then uses it for all the files being checked in. This is convenient for registering or checking in several files at once, as part of the same change.
You can toggle between terse display (only locked files, or files not
up-to-date) and full display at any time by typing v t
vc-dired-toggle-terse-mode. There is also a special command
* l (vc-dired-mark-locked), which marks all files currently
locked (or, with CVS, all files not up-to-date). Thus, typing * l
t k is another way to delete from the buffer all files except those
currently locked.
One use of version control is to maintain multiple "current" versions of a file. For example, you might have different versions of a program in which you are gradually adding various unfinished new features. Each such independent line of development is called a branch. VC allows you to create branches, switch between different branches, and merge changes from one branch to another. Please note, however, that branches are only supported for RCS at the moment.
A file's main line of development is usually called the trunk. The versions on the trunk are normally numbered 1.1, 1.2, 1.3, etc. At any such version, you can start an independent branch. A branch starting at version 1.2 would have version number 1.2.1.1, and consecutive versions on this branch would have numbers 1.2.1.2, 1.2.1.3, 1.2.1.4, and so on. If there is a second branch also starting at version 1.2, it would consist of versions 1.2.2.1, 1.2.2.2, 1.2.2.3, etc.
If you omit the final component of a version number, that is called a branch number. It refers to the highest existing version on that branch--the head version of that branch. The branches in the example above have branch numbers 1.2.1 and 1.2.2.
To switch between branches, type C-u C-x C-q and specify the version number you want to select. This version is then visited unlocked (write-protected), so you can examine it before locking it. Switching branches in this way is allowed only when the file is not locked.
You can omit the minor version number, thus giving only the branch number; this takes you to the head version on the chosen branch. If you only type RET, Emacs goes to the highest version on the trunk.
After you have switched to any branch (including the main branch), you stay on it for subsequent VC commands, until you explicitly select some other branch.
To create a new branch from a head version (one that is the latest in the branch that contains it), first select that version if necessary, lock it with C-x C-q, and make whatever changes you want. Then, when you check in the changes, use C-u C-x C-q. This lets you specify the version number for the new version. You should specify a suitable branch number for a branch starting at the current version. For example, if the current version is 2.5, the branch number should be 2.5.1, 2.5.2, and so on, depending on the number of existing branches at that point.
To create a new branch at an older version (one that is no longer the head of a branch), first select that version, then lock it with C-x C-q. You'll be asked to confirm, when you lock the old version, that you really mean to create a new branch--if you say no, you'll be offered a chance to lock the latest version instead.
Then make your changes and type C-x C-q again to check in a new version. This automatically creates a new branch starting from the selected version. You need not specially request a new branch, because that's the only way to add a new version at a point that is not the head of a branch.
After the branch is created, you "stay" on it. That means that subsequent check-ins create new versions on that branch. To leave the branch, you must explicitly select a different version with C-u C-x C-q. To transfer changes from one branch to another, use the merge command, described in the next section.
When you have finished the changes on a certain branch, you will
often want to incorporate them into the file's main line of development
(the trunk). This is not a trivial operation, because development might
also have proceeded on the trunk, so that you must merge the
changes into a file that has already been changed otherwise. VC allows
you to do this (and other things) with the vc-merge command.
C-x v m (vc-merge) takes a set of changes and merges it
into the current version of the work file. It first asks you for a
branch number or a pair of version numbers in the minibuffer. Then it
finds the changes from that branch, or between the two versions you
specified, and merges them into the current version of the current file.
As an example, suppose that you have finished a certain feature on branch 1.3.1. In the meantime, development on the trunk has proceeded to version 1.5. To merge the changes from the branch to the trunk, first go to the head version of the trunk, by typing C-u C-x C-q RET. Version 1.5 is now current. If locking is used for the file, type C-x C-q to lock version 1.5 so that you can change it. Next, type C-x v m 1.3.1 RET. This takes the entire set of changes on branch 1.3.1 (relative to version 1.3, where the branch started, up to the last version on the branch) and merges it into the current version of the work file. You can now check in the changed file, thus creating version 1.6 containing the changes from the branch.
It is possible to do further editing after merging the branch, before the next check-in. But it is usually wiser to check in the merged version, then lock it and make the further changes. This will keep a better record of the history of changes.
When you merge changes into a file that has itself been modified, the changes might overlap. We call this situation a conflict, and reconciling the conflicting changes is called resolving a conflict.
Whenever conflicts occur during merging, VC detects them, tells you about them in the echo area, and asks whether you want help in merging. If you say yes, it starts an Ediff session (see section `Ediff' in The Ediff Manual).
If you say no, the conflicting changes are both inserted into the file, surrounded by conflict markers. The example below shows how a conflict region looks; the file is called `name' and the current master file version with user B's changes in it is 1.11.
<<<<<<< name User A's version ======= User B's version >>>>>>> 1.11
Then you can resolve the conflicts by editing the file manually. Or
you can type M-x vc-resolve-conflicts after visiting the file.
This starts an Ediff session, as described above.
It is often useful for multiple developers to work simultaneously on different branches of a file. CVS allows this by default; for RCS, it is possible if you create multiple source directories. Each source directory should have a link named `RCS' which points to a common directory of RCS master files. Then each source directory can have its own choice of selected versions, but all share the same common RCS records.
This technique works reliably and automatically, provided that the source files contain RCS version headers (see section Inserting Version Control Headers). The headers enable Emacs to be sure, at all times, which version number is present in the work file.
If the files do not have version headers, you must instead tell Emacs explicitly in each session which branch you are working on. To do this, first find the file, then type C-u C-x C-q and specify the correct branch number. This ensures that Emacs knows which branch it is using during this particular editing session.
A snapshot is a named set of file versions (one for each registered file) that you can treat as a unit. One important kind of snapshot is a release, a (theoretically) stable version of the system that is ready for distribution to users.
There are two basic commands for snapshots; one makes a snapshot with a given name, the other retrieves a named snapshot.
C-x v s name RET
vc-create-snapshot).
C-x v r name RET
vc-retrieve-snapshot).
This command reports an error if any files are locked at or below the
current directory, without changing anything; this is to avoid
overwriting work in progress.
A snapshot uses a very small amount of resources--just enough to record the list of file names and which version belongs to the snapshot. Thus, you need not hesitate to create snapshots whenever they are useful.
You can give a snapshot name as an argument to C-x v = or C-x v ~ (see section Examining And Comparing Old Versions). Thus, you can use it to compare a snapshot against the current files, or two snapshots against each other, or a snapshot against a named version.
VC's snapshot facilities are modeled on RCS's named-configuration support. They use RCS's native facilities for this, so under VC snapshots made using RCS are visible even when you bypass VC.
For SCCS, VC implements snapshots itself. The files it uses contain name/file/version-number triples. These snapshots are visible only through VC.
A snapshot is a set of checked-in versions. So make sure that all the files are checked in and not locked when you make a snapshot.
File renaming and deletion can create some difficulties with snapshots. This is not a VC-specific problem, but a general design issue in version control systems that no one has solved very well yet.
If you rename a registered file, you need to rename its master along
with it (the command vc-rename-file does this automatically). If
you are using SCCS, you must also update the records of the snapshot, to
mention the file by its new name (vc-rename-file does this,
too). An old snapshot that refers to a master file that no longer
exists under the recorded name is invalid; VC can no longer retrieve
it. It would be beyond the scope of this manual to explain enough about
RCS and SCCS to explain how to update the snapshots by hand.
Using vc-rename-file makes the snapshot remain valid for
retrieval, but it does not solve all problems. For example, some of the
files in the program probably refer to others by name. At the very
least, the makefile probably mentions the file that you renamed. If you
retrieve an old snapshot, the renamed file is retrieved under its new
name, which is not the name that the makefile expects. So the program
won't really work as retrieved.
This section explains the less-frequently-used features of VC.
If you use RCS or CVS for a program and also maintain a change log file for it (see section Change Logs), you can generate change log entries automatically from the version control log entries:
vc-update-change-log).
This command works with RCS or CVS only, not with SCCS.
For example, suppose the first line of `ChangeLog' is dated 10 April 1992, and that the only check-in since then was by Nathaniel Bowditch to `rcs2log' on 8 May 1992 with log text `Ignore log messages that start with `#'.'. Then C-x v a visits `ChangeLog' and inserts text like this:
@medbreak
Fri May 8 21:45:00 1992 Nathaniel Bowditch <nat@apn.org>
* rcs2log: Ignore log messages that start with `#'.
@medbreak
You can then edit the new change log entry further as you wish.
Normally, the log entry for file `foo' is displayed as `* foo: text of log entry'. The `:' after `foo' is omitted if the text of the log entry starts with `(functionname): '. For example, if the log entry for `vc.el' is `(vc-do-command): Check call-process status.', then the text in `ChangeLog' looks like this:
@medbreak
Wed May 6 10:53:00 1992 Nathaniel Bowditch <nat@apn.org>
* vc.el (vc-do-command): Check call-process status.
@medbreak
When C-x v a adds several change log entries at once, it groups related log entries together if they all are checked in by the same author at nearly the same time. If the log entries for several such files all have the same text, it coalesces them into a single entry. For example, suppose the most recent check-ins have the following log entries:
* For `vc.texinfo': `Fix expansion typos.' * For `vc.el': `Don't call expand-file-name.' * For `vc-hooks.el': `Don't call expand-file-name.'
They appear like this in `ChangeLog':
@medbreak
Wed Apr 1 08:57:59 1992 Nathaniel Bowditch <nat@apn.org>
* vc.texinfo: Fix expansion typos.
* vc.el, vc-hooks.el: Don't call expand-file-name.
@medbreak
Normally, C-x v a separates log entries by a blank line, but you can mark several related log entries to be clumped together (without an intervening blank line) by starting the text of each related log entry with a label of the form `{clumpname} '. The label itself is not copied to `ChangeLog'. For example, suppose the log entries are:
* For `vc.texinfo': `{expand} Fix expansion typos.'
* For `vc.el': `{expand} Don't call expand-file-name.'
* For `vc-hooks.el': `{expand} Don't call expand-file-name.'
Then the text in `ChangeLog' looks like this:
@medbreak
Wed Apr 1 08:57:59 1992 Nathaniel Bowditch <nat@apn.org>
* vc.texinfo: Fix expansion typos.
* vc.el, vc-hooks.el: Don't call expand-file-name.
@medbreak
A log entry whose text begins with `#' is not copied to `ChangeLog'. For example, if you merely fix some misspellings in comments, you can log the change with an entry beginning with `#' to avoid putting such trivia into `ChangeLog'.
When you rename a registered file, you must also rename its master
file correspondingly to get proper results. Use vc-rename-file
to rename the source file as you specify, and rename its master file
accordingly. It also updates any snapshots (see section Snapshots) that
mention the file, so that they use the new name; despite this, the
snapshot thus modified may not completely work (see section Snapshot Caveats).
You cannot use vc-rename-file on a file that is locked by
someone else.
Sometimes it is convenient to put version identification strings directly into working files. Certain special strings called version headers are replaced in each successive version by the number of that version.
If you are using RCS, and version headers are present in your working files, Emacs can use them to determine the current version and the locking state of the files. This is more reliable than referring to the master files, which is done when there are no version headers. Note that in a multi-branch environment, version headers are necessary to make VC behave correctly (see section Multi-User Branching).
Searching for version headers is controlled by the variable
vc-consult-headers. If it is non-nil, Emacs searches for
headers to determine the version number you are editing. Setting it to
nil disables this feature.
You can use the C-x v h command (vc-insert-headers) to
insert a suitable header string.
The default header string is `$Id: GNU_Emacs_Documentation.html,v 1.1.1.1 2001/04/25 01:10:05 dgraver Exp $' for RCS and
`%W%' for SCCS. You can specify other headers to insert by
setting the variable vc-header-alist. Its value is a list of
elements of the form (program . string) where
program is RCS or SCCS and string is the
string to use.
Instead of a single string, you can specify a list of strings; then each string in the list is inserted as a separate header on a line of its own.
It is often necessary to use "superfluous" backslashes when writing the strings that you put in this variable. This is to prevent the string in the constant from being interpreted as a header itself if the Emacs Lisp file containing it is maintained with version control.
Each header is inserted surrounded by tabs, inside comment delimiters,
on a new line at the start of the buffer. Normally the ordinary comment
start and comment end strings of the current mode are used, but for
certain modes, there are special comment delimiters for this purpose;
the variable vc-comment-alist specifies them. Each element of
this list has the form (mode starter ender).
The variable vc-static-header-alist specifies further strings
to add based on the name of the buffer. Its value should be a list of
elements of the form (regexp . format). Whenever
regexp matches the buffer name, format is inserted as part
of the header. A header line is inserted for each element that matches
the buffer name, and for each string specified by
vc-header-alist. The header line is made by processing the
string from vc-header-alist with the format taken from the
element. The default value for vc-static-header-alist is as follows:
(("\\.c$" .
"\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n\
#endif /* lint */\n"))
It specifies insertion of text of this form:
#ifndef lint static char vcid[] = "string"; #endif /* lint */
Note that the text above starts with a blank line.
If you use more than one version header in a file, put them close
together in the file. The mechanism in revert-buffer that
preserves markers may not handle markers positioned between two version
headers.
There are many ways of customizing VC. The options you can set fall into four categories, described in the following sections.
You can tell RCS and CVS whether to use locking for a file or not (see section Concepts of Version Control, for a description of locking). VC automatically recognizes what you have chosen, and behaves accordingly.
For RCS, the default is to use locking, but there is a mode called non-strict locking in which you can check-in changes without locking the file first. Use `rcs -U' to switch to non-strict locking for a particular file, see the `rcs' manpage for details.
Under CVS, the default is not to use locking; anyone can change a work file at any time. However, there are ways to restrict this, resulting in behavior that resembles locking.
For one thing, you can set the CVSREAD environment variable to
an arbitrary value. If this variable is defined, CVS makes your work
files read-only by default. In Emacs, you must type C-x C-q to
make the file writeable, so that editing works in fact similar as if
locking was used. Note however, that no actual locking is performed, so
several users can make their files writeable at the same time. When
setting CVSREAD for the first time, make sure to check out all
your modules anew, so that the file protections are set correctly.
Another way to achieve something similar to locking is to use the
watch feature of CVS. If a file is being watched, CVS makes it
read-only by default, and you must also use C-x C-q in Emacs to
make it writable. VC calls cvs edit to make the file writeable,
and CVS takes care to notify other developers of the fact that you
intend to change the file. See the CVS documentation for details on
using the watch feature.
You can turn off use of VC for CVS-managed files by setting the
variable vc-handle-cvs to nil. If you do this, Emacs
treats these files as if they were not registered, and the VC commands
are not available for them. You must do all CVS operations manually.
Emacs normally does not save backup files for source files that are
maintained with version control. If you want to make backup files even
for files that use version control, set the variable
vc-make-backup-files to a non-nil value.
Normally the work file exists all the time, whether it is locked or
not. If you set vc-keep-workfiles to nil, then checking
in a new version with C-x C-q deletes the work file; but any
attempt to visit the file with Emacs creates it again. (With CVS, work
files are always kept.)
Editing a version-controlled file through a symbolic link can be dangerous. It bypasses the version control system--you can edit the file without locking it, and fail to check your changes in. Also, your changes might overwrite those of another user. To protect against this, VC checks each symbolic link that you visit, to see if it points to a file under version control.
The variable vc-follow-symlinks controls what to do when a
symbolic link points to a version-controlled file. If it is nil,
VC only displays a warning message. If it is t, VC automatically
follows the link, and visits the real file instead, telling you about
this in the echo area. If the value is ask (the default), VC
asks you each time whether to follow the link.
When deducing the locked/unlocked state of a file, VC first looks for an RCS version header string in the file (see section Inserting Version Control Headers). If there is no header string, or if you are using SCCS, VC normally looks at the file permissions of the work file; this is fast. But there might be situations when the file permissions cannot be trusted. In this case the master file has to be consulted, which is rather expensive. Also the master file can only tell you if there's any lock on the file, but not whether your work file really contains that locked version.
You can tell VC not to use version headers to determine lock status by
setting vc-consult-headers to nil. VC then always uses
the file permissions (if it can trust them), or else checks the master
file.
You can specify the criterion for whether to trust the file
permissions by setting the variable vc-mistrust-permissions. Its
value can be t (always mistrust the file permissions and check
the master file), nil (always trust the file permissions), or a
function of one argument which makes the decision. The argument is the
directory name of the `RCS', `CVS' or `SCCS'
subdirectory. A non-nil value from the function says to mistrust
the file permissions. If you find that the file permissions of work
files are changed erroneously, set vc-mistrust-permissions to
t. Then VC always checks the master file to determine the file's
status.
If vc-suppress-confirm is non-nil, then C-x C-q
and C-x v i can save the current buffer without asking, and
C-x v u also operates without asking for confirmation. (This
variable does not affect C-x v c; that operation is so drastic
that it should always ask for confirmation.)
VC mode does much of its work by running the shell commands for RCS,
CVS and SCCS. If vc-command-messages is non-nil, VC
displays messages to indicate which shell commands it runs, and
additional messages when the commands finish.
You can specify additional directories to search for version control
programs by setting the variable vc-path. These directories are
searched before the usual search path. But the proper files are usually
found automatically.
The file system groups files into directories. A directory listing is a list of all the files in a directory. Emacs provides commands to create and delete directories, and to make directory listings in brief format (file names only) and verbose format (sizes, dates, and authors included). There is also a directory browser called Dired; see section Dired, the Directory Editor.
list-directory).
The command to display a directory listing is C-x C-d
(list-directory). It reads using the minibuffer a file name
which is either a directory to be listed or a wildcard-containing
pattern for the files to be listed. For example,
C-x C-d /u2/emacs/etc RET
lists all the files in directory `/u2/emacs/etc'. Here is an example of specifying a file name pattern:
C-x C-d /u2/emacs/src/*.c RET
Normally, C-x C-d prints a brief directory listing containing just file names. A numeric argument (regardless of value) tells it to make a verbose listing including sizes, dates, and authors (like `ls -l').
The text of a directory listing is obtained by running ls in an
inferior process. Two Emacs variables control the switches passed to
ls: list-directory-brief-switches is a string giving the
switches to use in brief listings ("-CF" by default), and
list-directory-verbose-switches is a string giving the switches to
use in a verbose listing ("-l" by default).
The command M-x diff compares two files, displaying the
differences in an Emacs buffer named `*Diff*'. It works by running
the diff program, using options taken from the variable
diff-switches, whose value should be a string.
The buffer `*Diff*' has Compilation mode as its major mode, so you can use C-x ` to visit successive changed locations in the two source files. You can also move to a particular hunk of changes and type RET or C-c C-c, or click Mouse-2 on it, to move to the corresponding source location. You can also use the other special commands of Compilation mode: SPC and DEL for scrolling, and M-p and M-n for cursor motion. See section Running Compilations under Emacs.
The command M-x diff-backup compares a specified file with its most
recent backup. If you specify the name of a backup file,
diff-backup compares it with the source file that it is a backup
of.
The command M-x compare-windows compares the text in the current window with that in the next window. Comparison starts at point in each window, and each starting position is pushed on the mark ring in its respective buffer. Then point moves forward in each window, a character at a time, until a mismatch between the two windows is reached. Then the command is finished. For more information about windows in Emacs, section Multiple Windows.
With a numeric argument, compare-windows ignores changes in
whitespace. If the variable compare-ignore-case is
non-nil, it ignores differences in case as well.
See also section Merging Files with Emerge, for convenient facilities for merging two similar files.
Emacs has commands for performing many other operations on files. All operate on one file; they do not accept wildcard file names.
M-x view-file allows you to scan or read a file by sequential
screenfuls. It reads a file name argument using the minibuffer. After
reading the file into an Emacs buffer, view-file displays the
beginning. You can then type SPC to scroll forward one windowful,
or DEL to scroll backward. Various other commands are provided
for moving around in the file, but none for changing it; type ?
while viewing for a list of them. They are mostly the same as normal
Emacs cursor motion commands. To exit from viewing, type q.
The commands for viewing are defined by a special major mode called View
mode.
A related command, M-x view-buffer, views a buffer already present in Emacs. See section Miscellaneous Buffer Operations.
M-x insert-file inserts a copy of the contents of the specified file into the current buffer at point, leaving point unchanged before the contents and the mark after them.
M-x write-region is the inverse of M-x insert-file; it copies the contents of the region into the specified file. M-x append-to-file adds the text of the region to the end of the specified file. See section Accumulating Text.
M-x delete-file deletes the specified file, like the rm
command in the shell. If you are deleting many files in one directory, it
may be more convenient to use Dired (see section Dired, the Directory Editor).
M-x rename-file reads two file names old and new using the minibuffer, then renames file old as new. If a file named new already exists, you must confirm with yes or renaming is not done; this is because renaming causes the old meaning of the name new to be lost. If old and new are on different file systems, the file old is copied and deleted.
The similar command M-x add-name-to-file is used to add an additional name to an existing file without removing its old name. The new name must belong on the same file system that the file is on.
M-x copy-file reads the file old and writes a new file named new with the same contents. Confirmation is required if a file named new already exists, because copying has the consequence of overwriting the old contents of the file new.
M-x make-symbolic-link reads two file names target and linkname, then creates a symbolic link named linkname and pointing at target. The effect is that future attempts to open file linkname will refer to whatever file is named target at the time the opening is done, or will get an error if the name target is not in use at that time. This command does not expand the argument target, so that it allows you to specify a relative name as the target of the link.
Confirmation is required when creating the link if linkname is in use. Note that not all systems support symbolic links.
Emacs comes with a library that can automatically uncompress compressed files when you visit them, and automatically recompress them if you alter them and save them. To enable this feature, type the command M-x auto-compression-mode.
When automatic compression (which implies automatic uncompression as
well) is enabled, Emacs recognizes compressed files by their file names.
File names ending in `.gz' indicate a file compressed with
gzip. Other endings indicate other compression programs.
Automatic uncompression and compression apply to all the operations in which Emacs uses the contents of a file. This includes visiting it, saving it, inserting its contents into a buffer, loading it, and byte compiling it.
You can refer to files on other machines using a special file name syntax:
/host:filename /user@host:filename
When you do this, Emacs uses the FTP program to read and write files on the specified host. It logs in through FTP using your user name or the name user. It may ask you for a password from time to time; this is used for logging in on host.
Normally, if you do not specify a user name in a remote file name,
that means to use your own user name. But if you set the variable
ange-ftp-default-user to a string, that string is used instead.
(The Emacs package that implements FTP file access is called
ange-ftp.)
You can entirely turn off the FTP file name feature by setting the
variable file-name-handler-alist to nil.
You can quote an absolute file name to prevent special characters and syntax in it from having their special effects. The way to do this is to add `/:' at the beginning.
For example, you can quote a local file name which appears remote, to prevent it from being treated as a remote file name. Thus, if you have a directory named `/foo:' and a file named `bar' in it, you can refer to that file in Emacs as `/:/foo:/bar'.
`/:' can also prevent `~' from being treated as a special character for a user's home directory. For example, `/:/tmp/~hack' refers to a file whose name is `~hack' in directory `/tmp'.
Likewise, quoting with `/:' is one way to enter in the minibuffer a file name that contains `$'. However, the `/:' must be at the beginning of the buffer in order to quote `$'.
The text you are editing in Emacs resides in an object called a buffer. Each time you visit a file, a buffer is created to hold the file's text. Each time you invoke Dired, a buffer is created to hold the directory listing. If you send a message with C-x m, a buffer named `*mail*' is used to hold the text of the message. When you ask for a command's documentation, that appears in a buffer called `*Help*'.
At any time, one and only one buffer is selected. It is also called the current buffer. Often we say that a command operates on "the buffer" as if there were only one; but really this means that the command operates on the selected buffer (most commands do).
When Emacs has multiple windows, each window has a chosen buffer which is displayed there, but at any time only one of the windows is selected and its chosen buffer is the selected buffer. Each window's mode line displays the name of the buffer that the window is displaying (see section Multiple Windows).
Each buffer has a name, which can be of any length, and you can select any buffer by giving its name. Most buffers are made by visiting files, and their names are derived from the files' names. But you can also create an empty buffer with any name you want. A newly started Emacs has a buffer named `*scratch*' which can be used for evaluating Lisp expressions in Emacs. The distinction between upper and lower case matters in buffer names.
Each buffer records individually what file it is visiting, whether it is modified, and what major mode and minor modes are in effect in it (see section Major Modes). Any Emacs variable can be made local to a particular buffer, meaning its value in that buffer can be different from the value in other buffers. See section Local Variables.
switch-to-buffer).
switch-to-buffer-other-window).
switch-to-buffer-other-frame).
To select the buffer named bufname, type C-x b bufname
RET. This runs the command switch-to-buffer with argument
bufname. You can use completion on an abbreviation for the buffer
name you want (see section Completion). An empty argument to C-x b
specifies the most recently selected buffer that is not displayed in any
window.
Most buffers are created by visiting files, or by Emacs commands that
want to display some text, but you can also create a buffer explicitly
by typing C-x b bufname RET. This makes a new, empty
buffer that is not visiting any file, and selects it for editing. Such
buffers are used for making notes to yourself. If you try to save one,
you are asked for the file name to use. The new buffer's major mode is
determined by the value of default-major-mode (see section Major Modes).
Note that C-x C-f, and any other command for visiting a file, can also be used to switch to an existing file-visiting buffer. See section Visiting Files.
Emacs uses buffer names that start with a space for internal purposes. It treats these buffers specially in minor ways--for example, by default they do not record undo information. It is best to avoid using such buffer names yourself.
list-buffers).
To display a list of all the buffers that exist, type C-x C-b. Each line in the list shows one buffer's name, major mode and visited file. The buffers are listed in the order that they were current; the buffers that were current most recently come first.
`*' at the beginning of a line indicates the buffer is "modified." If several buffers are modified, it may be time to save some with C-x s (see section Saving Files). `%' indicates a read-only buffer. `.' marks the selected buffer. Here is an example of a buffer list:
MR Buffer Size Mode File
-- ------ ---- ---- ----
.* emacs.tex 383402 Texinfo /u2/emacs/man/emacs.tex
*Help* 1287 Fundamental
files.el 23076 Emacs-Lisp /u2/emacs/lisp/files.el
% RMAIL 64042 RMAIL /u/rms/RMAIL
*% man 747 Dired /u2/emacs/man/
net.emacs 343885 Fundamental /u/rms/net.emacs
fileio.c 27691 C /u2/emacs/src/fileio.c
NEWS 67340 Text /u2/emacs/etc/NEWS
*scratch* 0 Lisp Interaction
Note that the buffer `*Help*' was made by a help request; it is not
visiting any file. The buffer man was made by Dired on the
directory `/u2/emacs/man/'.
vc-toggle-read-only).
A buffer can be read-only, which means that commands to change its contents are not allowed. The mode line indicates read-only buffers with `%%' or `%*' near the left margin. Read-only buffers are usually made by subsystems such as Dired and Rmail that have special commands to operate on the text; also by visiting a file whose access control says you cannot write it.
If you wish to make changes in a read-only buffer, use the command
C-x C-q (vc-toggle-read-only). It makes a read-only buffer
writable, and makes a writable buffer read-only. In most cases, this
works by setting the variable buffer-read-only, which has a local
value in each buffer and makes the buffer read-only if its value is
non-nil. If the file is maintained with version control,
C-x C-q works through the version control system to change the
read-only status of the file as well as the buffer. See section Version Control.
M-x rename-buffer changes the name of the current buffer. Specify the new name as a minibuffer argument. There is no default. If you specify a name that is in use for some other buffer, an error happens and no renaming is done.
M-x rename-uniquely renames the current buffer to a similar name with a numeric suffix added to make it both different and unique. This command does not need an argument. It is useful for creating multiple shell buffers: if you rename the `*Shell*' buffer, then do M-x shell again, it makes a new shell buffer named `*Shell*'; meanwhile, the old shell buffer continues to exist under its new name. This method is also good for mail buffers, compilation buffers, and most Emacs features that create special buffers with particular names.
M-x view-buffer is much like M-x view-file (see section Miscellaneous File Operations) except that it examines an already existing Emacs buffer. View mode provides commands for scrolling through the buffer conveniently but not for changing it. When you exit View mode with q, that switches back to the buffer (and the position) which was previously displayed in the window. Alternatively, if you exit View mode with e, the buffer and the value of point that resulted from your perusal remain in effect.
The commands M-x append-to-buffer and M-x insert-buffer can be used to copy text from one buffer to another. See section Accumulating Text.
If you continue an Emacs session for a while, you may accumulate a large number of buffers. You may then find it convenient to kill the buffers you no longer need. On most operating systems, killing a buffer releases its space back to the operating system so that other programs can use it. Here are some commands for killing buffers:
kill-buffer).
C-x k (kill-buffer) kills one buffer, whose name you
specify in the minibuffer. The default, used if you type just RET
in the minibuffer, is to kill the current buffer. If you kill the
current buffer, another buffer is selected; one that has been selected
recently but does not appear in any window now. If you ask to kill a
file-visiting buffer that is modified (has unsaved editing), then you
must confirm with yes before the buffer is killed.
The command M-x kill-some-buffers asks about each buffer, one by
one. An answer of y means to kill the buffer. Killing the current
buffer or a buffer containing unsaved changes selects a new buffer or asks
for confirmation just like kill-buffer.
The buffer menu feature (see section Operating on Several Buffers) is also convenient for killing various buffers.
If you want to do something special every time a buffer is killed, you
can add hook functions to the hook kill-buffer-hook (see section Hooks).
If you run one Emacs session for a period of days, as many people do, it can fill up with buffers that you used several days ago. The command M-x clean-buffer-list is a convenient way to purge them; it kills all the unmodified buffers that you have not used for a long time. An ordinary buffer is killed if it has not been displayed for three days; however, you can specify certain buffers that should never be killed automatically, and others that should be killed if they have been unused for a mere hour.
You can also have this buffer purging done for you, every day at
midnight, by enabling Midnight mode. Midnight mode operates each day at
midnight; at that time, it runs clean-buffer-list, or whichever
functions you have placed in the normal hook midnight-hook
(see section Hooks).
To enable Midnight mode, use the Customization buffer to set the
variable midnight-mode to t. See section Easy Customization Interface.
The buffer-menu facility is like a "Dired for buffers"; it allows you to request operations on various Emacs buffers by editing an Emacs buffer containing a list of them. You can save buffers, kill them (here called deleting them, for consistency with Dired), or display them.
The command buffer-menu writes a list of all Emacs buffers into
the buffer `*Buffer List*', and selects that buffer in Buffer Menu
mode. The buffer is read-only, and can be changed only through the
special commands described in this section. The usual Emacs cursor
motion commands can be used in the `*Buffer List*' buffer. The
following commands apply to the buffer described on the current line.
The d, C-d, s and u commands to add or remove flags also move down (or up) one line. They accept a numeric argument as a repeat count.
These commands operate immediately on the buffer listed on the current line:
There are also commands to select another buffer or buffers:
All that buffer-menu does directly is create and switch to a
suitable buffer, and turn on Buffer Menu mode. Everything else
described above is implemented by the special commands provided in
Buffer Menu mode. One consequence of this is that you can switch from
the `*Buffer List*' buffer to another Emacs buffer, and edit there.
You can reselect the `*Buffer List*' buffer later, to perform the
operations already requested, or you can kill it, or pay no further
attention to it.
The only difference between buffer-menu and list-buffers
is that buffer-menu switches to the `*Buffer List*' buffer
in the selected window; list-buffers displays it in another
window. If you run list-buffers (that is, type C-x C-b)
and select the buffer list manually, you can use all of the commands
described here.
The buffer `*Buffer List*' is not updated automatically when
buffers are created and killed; its contents are just text. If you have
created, deleted or renamed buffers, the way to update `*Buffer
List*' to show what you have done is to type g
(revert-buffer) or repeat the buffer-menu command.
An indirect buffer shares the text of some other buffer, which is called the base buffer of the indirect buffer. In some ways it is the analogue, for buffers, of a symbolic link between files.
The text of the indirect buffer is always identical to the text of its base buffer; changes made by editing either one are visible immediately in the other. But in all other respects, the indirect buffer and its base buffer are completely separate. They have different names, different values of point, different narrowing, different markers, different major modes, and different local variables.
An indirect buffer cannot visit a file, but its base buffer can. If you try to save the indirect buffer, that actually works by saving the base buffer. Killing the base buffer effectively kills the indirect buffer, but killing an indirect buffer has no effect on its base buffer.
One way to use indirect buffers is to display multiple views of an outline. See section Viewing One Outline in Multiple Views.
Emacs can split a frame into two or many windows. Multiple windows can display parts of different buffers, or different parts of one buffer. Multiple frames always imply multiple windows, because each frame has its own set of windows. Each window belongs to one and only one frame.
Each Emacs window displays one Emacs buffer at any time. A single buffer may appear in more than one window; if it does, any changes in its text are displayed in all the windows where it appears. But the windows showing the same buffer can show different parts of it, because each window has its own value of point.
At any time, one of the windows is the selected window; the buffer this window is displaying is the current buffer. The terminal's cursor shows the location of point in this window. Each other window has a location of point as well, but since the terminal has only one cursor there is no way to show where those locations are. When multiple frames are visible in X Windows, each frame has a cursor which appears in the frame's selected window. The cursor in the selected frame is solid; the cursor in other frames is a hollow box.
Commands to move point affect the value of point for the selected Emacs
window only. They do not change the value of point in any other Emacs
window, even one showing the same buffer. The same is true for commands
such as C-x b to change the selected buffer in the selected window;
they do not affect other windows at all. However, there are other commands
such as C-x 4 b that select a different window and switch buffers in
it. Also, all commands that display information in a window, including
(for example) C-h f (describe-function) and C-x C-b
(list-buffers), work by switching buffers in a nonselected window
without affecting the selected window.
When multiple windows show the same buffer, they can have different regions, because they can have different values of point. However, they all have the same value for the mark, because each buffer has only one mark position.
Each window has its own mode line, which displays the buffer name, modification status and major and minor modes of the buffer that is displayed in the window. See section The Mode Line, for full details on the mode line.
@break
split-window-vertically).
split-window-horizontally).
The command C-x 2 (split-window-vertically) breaks the
selected window into two windows, one above the other. Both windows start
out displaying the same buffer, with the same value of point. By default
the two windows each get half the height of the window that was split; a
numeric argument specifies how many lines to give to the top window.
C-x 3 (split-window-horizontally) breaks the selected
window into two side-by-side windows. A numeric argument specifies how
many columns to give the one on the left. A line of vertical bars
separates the two windows. Windows that are not the full width of the
screen have mode lines, but they are truncated. On terminals where
Emacs does not support highlighting, truncated mode lines sometimes do
not appear in inverse video.
You can split a window horizontally or vertically by clicking C-Mouse-2 in the mode line or the scroll bar. The line of splitting goes through the place where you click: if you click on the mode line, the new scroll bar goes above the spot; if you click in the scroll bar, the mode line of the split window is side by side with your click.
When a window is less than the full width, text lines too long to fit are
frequent. Continuing all those lines might be confusing. The variable
truncate-partial-width-windows can be set non-nil to force
truncation in all windows less than the full width of the screen,
independent of the buffer being displayed and its value for
truncate-lines. See section Continuation Lines.
Horizontal scrolling is often used in side-by-side windows. See section Controlling the Display.
If split-window-keep-point is non-nil, the default, both
of the windows resulting from C-x 2 inherit the value of point
from the window that was split. This means that scrolling is
inevitable. If this variable is nil, then C-x 2 tries to
avoid shifting any text the screen, by putting point in each window at a
position already visible in the window. It also selects whichever
window contain the screen line that the cursor was previously on. Some
users prefer the latter mode slow terminals.
other-window). That is o, not zero.
scroll-other-window).
mouse-select-window).
To select a different window, click with Mouse-1 on its mode
line. With the keyboard, you can switch windows by typing C-x o
(other-window). That is an o, for `other', not a zero.
When there are more than two windows, this command moves through all the
windows in a cyclic order, generally top to bottom and left to right.
After the rightmost and bottommost window, it goes back to the one at
the upper left corner. A numeric argument means to move several steps
in the cyclic order of windows. A negative argument moves around the
cycle in the opposite order. When the minibuffer is active, the
minibuffer is the last window in the cycle; you can switch from the
minibuffer window to one of the other windows, and later switch back and
finish supplying the minibuffer argument that is requested.
See section Editing in the Minibuffer.
The usual scrolling commands (see section Controlling the Display) apply to the selected
window only, but there is one command to scroll the next window.
C-M-v (scroll-other-window) scrolls the window that
C-x o would select. It takes arguments, positive and negative,
like C-v. (In the minibuffer, C-M-v scrolls the window
that contains the minibuffer help display, if any, rather than the
next window in the standard cyclic order.)
The command M-x compare-windows lets you compare two files or
buffers visible in two windows, by moving through them to the next
mismatch. See section Comparing Files, for details.
C-x 4 is a prefix key for commands that select another window (splitting the window if there is only one) and select a buffer in that window. Different C-x 4 commands have different ways of finding the buffer to select.
switch-to-buffer-other-window.
display-buffer.
find-file-other-window. See section Visiting Files.
dired-other-window. See section Dired, the Directory Editor.
mail-other-window; its same-window analogue is C-x m
(see section Sending Mail).
find-tag-other-window, the multiple-window variant of M-.
(see section Tags Tables).
find-file-read-only-other-window.
See section Visiting Files.
Certain Emacs commands switch to a specific buffer with special contents. For example, M-x shell switches to a buffer named `*Shell*'. By convention, all these commands are written to pop up the buffer in a separate window. But you can specify that certain of these buffers should appear in the selected window.
If you add a buffer name to the list same-window-buffer-names,
the effect is that such commands display that particular buffer by
switching to it in the selected window. For example, if you add the
element "*grep*" to the list, the grep command will
display its output buffer in the selected window.
The default value of same-window-buffer-names is not
nil: it specifies buffer names `*info*', `*mail*' and
`*shell*' (as well as others used by more obscure Emacs packages).
This is why M-x shell normally switches to the `*shell*'
buffer in the selected window. If you delete this element from the
value of same-window-buffer-names, the behavior of M-x
shell will change--it will pop up the buffer in another window
instead.
You can specify these buffers more generally with the variable
same-window-regexps. Set it to a list of regular expressions;
then any buffer whose name matches one of those regular expressions is
displayed by switching to it in the selected window. (Once again, this
applies only to buffers that normally get displayed for you in a
separate window.) The default value of this variable specifies Telnet
and rlogin buffers.
An analogous feature lets you specify buffers which should be displayed in their own individual frames. See section Special Buffer Frames.
delete-window). The last character
in this key sequence is a zero.
delete-other-windows).
kill-buffer-and-window). The last character in this key
sequence is a zero.
enlarge-window).
enlarge-window-horizontally).
shrink-window-horizontally).
shrink-window-if-larger-than-buffer).
balance-windows).
mouse-delete-other-windows).
mouse-delete-window).
To delete a window, type C-x 0 (delete-window). (That is
a zero.) The space occupied by the deleted window is given to an
adjacent window (but not the minibuffer window, even if that is active
at the time). Once a window is deleted, its attributes are forgotten;
only restoring a window configuration can bring it back. Deleting the
window has no effect on the buffer it used to display; the buffer
continues to exist, and you can select it in any window with C-x
b.
C-x 4 0 (kill-buffer-and-window) is a stronger command
than C-x 0; it kills the current buffer and then deletes the
selected window.
C-x 1 (delete-other-windows) is more powerful in a
different way; it deletes all the windows except the selected one (and
the minibuffer); the selected window expands to use the whole frame
except for the echo area.
You can also delete a window by clicking on its mode line with Mouse-2, and delete all the windows in a frame except one window by clicking on that window's mode line with Mouse-3.
The easiest way to adjust window heights is with a mouse. If you press Mouse-1 on a mode line, you can drag that mode line up or down, changing the heights of the windows above and below it.
To readjust the division of space among vertically adjacent windows,
use C-x ^ (enlarge-window). It makes the currently
selected window get one line bigger, or as many lines as is specified
with a numeric argument. With a negative argument, it makes the
selected window smaller. C-x }
(enlarge-window-horizontally) makes the selected window wider by
the specified number of columns. C-x {
(shrink-window-horizontally) makes the selected window narrower
by the specified number of columns.
When you make a window bigger, the space comes from one of its
neighbors. If this makes any window too small, it is deleted and its
space is given to an adjacent window. The minimum size is specified by
the variables window-min-height and window-min-width.
The command C-x - (shrink-window-if-larger-than-buffer)
reduces the height of the selected window, if it is taller than
necessary to show the whole text of the buffer it is displaying. It
gives the extra lines to other windows in the frame.
You can also use C-x + (balance-windows) to even out the
heights of all the windows in the selected frame.
See section Editing in the Minibuffer, for information about the Resize-Minibuffer mode, which automatically changes the size of the minibuffer window to fit the text in the minibuffer.
When using the X Window System, you can create multiple windows at the X level in a single Emacs session. Each X window that belongs to Emacs displays a frame which can contain one or several Emacs windows. A frame initially contains a single general-purpose Emacs window which you can subdivide vertically or horizontally into smaller windows. A frame normally contains its own echo area and minibuffer, but you can make frames that don't have these--they use the echo area and minibuffer of another frame.
Editing you do in one frame also affects the other frames. For instance, if you put text in the kill ring in one frame, you can yank it in another frame. If you exit Emacs through C-x C-c in one frame, it terminates all the frames. To delete just one frame, use C-x 5 0.
To avoid confusion, we reserve the word "window" for the subdivisions that Emacs implements, and never use it to refer to a frame.
Emacs compiled for MS-DOS emulates some aspects of the window system so that you can use many of the features described in this chapter. See section Keyboard and Mouse on MS-DOS, for more information.
The mouse commands for selecting and copying a region are mostly
compatible with the xterm program. You can use the same mouse
commands for copying between Emacs and other X client programs.
If you select a region with any of these mouse commands, and then immediately afterward type the DELETE function key, it deletes the region that you selected. The BACKSPACE function key and the ASCII character DEL do not do this; if you type any other key in between the mouse command and DELETE, it does not do this.
mouse-set-point).
This is normally the left button.
mouse-set-region). You can specify both ends of the
region with this single command.
If you move the mouse off the top or bottom of the window while
dragging, the window scrolls at a steady rate until you move the mouse
back into the window. This way, you can select regions that don't fit
entirely on the screen. The number of lines scrolled per step depends
on how far away from the window edge the mouse has gone; the variable
mouse-scroll-min-lines specifies a minimum step size.
mouse-yank-at-click).
This is normally the middle button.
mouse-save-then-kill, has several functions
depending on where you click and the status of the region.
The most basic case is when you click Mouse-1 in one place and
then Mouse-3 in another. This selects the text between those two
positions as the region. It also copies the new region to the kill
ring, so that you can copy it to someplace else.
If you click Mouse-1 in the text, scroll with the scroll bar, and
then click Mouse-3, it remembers where point was before scrolling
(where you put it with Mouse-1), and uses that position as the
other end of the region. This is so that you can select a region that
doesn't fit entirely on the screen.
More generally, if you do not have a highlighted region, Mouse-3
selects the text between point and the click position as the region. It
does this by setting the mark where point was, and moving point to where
you click.
If you have a highlighted region, or if the region was set just before
by dragging button 1, Mouse-3 adjusts the nearer end of the region
by moving it to where you click. The adjusted region's text also
replaces the old region's text in the kill ring.
If you originally specified the region using a double or triple
Mouse-1, so that the region is defined to consist of entire words
or lines, then adjusting the region with Mouse-3 also proceeds by
entire words or lines.
If you use Mouse-3 a second time consecutively, at the same place,
that kills the region already selected.
The simplest way to kill text with the mouse is to press Mouse-1 at one end, then press Mouse-3 twice at the other end. See section Deletion and Killing. To copy the text into the kill ring without deleting it from the buffer, press Mouse-3 just once--or just drag across the text with Mouse-1. Then you can copy it elsewhere by yanking it.
To yank the killed or copied text somewhere else, move the mouse there
and press Mouse-2. See section Yanking. However, if
mouse-yank-at-point is non-nil, Mouse-2 yanks at
point. Then it does not matter where you click, or even which of the
frame's windows you click on. The default value is nil. This
variable also affects yanking the secondary selection.
To copy text to another X window, kill it or save it in the kill ring. Under X, this also sets the primary selection. Then use the "paste" or "yank" command of the program operating the other window to insert the text from the selection.
To copy text from another X window, use the "cut" or "copy" command of the program operating the other window, to select the text you want. Then yank it in Emacs with C-y or Mouse-2.
These cutting and pasting commands also work on MS-Windows.
When Emacs puts text into the kill ring, or rotates text to the front
of the kill ring, it sets the primary selection in the X server.
This is how other X clients can access the text. Emacs also stores the
text in the cut buffer, but only if the text is short enough
(x-cut-buffer-max specifies the maximum number of characters);
putting long strings in the cut buffer can be slow.
The commands to yank the first entry in the kill ring actually check first for a primary selection in another program; after that, they check for text in the cut buffer. If neither of those sources provides text to yank, the kill ring contents are used.
The secondary selection is another way of selecting text using X. It does not use point or the mark, so you can use it to kill text without setting point or the mark.
mouse-set-secondary). The highlighting appears and changes as
you drag.
If you move the mouse off the top or bottom of the window while
dragging, the window scrolls at a steady rate until you move the mouse
back into the window. This way, you can mark regions that don't fit
entirely on the screen.
mouse-start-secondary).
mouse-secondary-save-then-kill). A second click
at the same place kills the secondary selection just made.
mouse-yank-secondary). This places point at the end of the
yanked text.
Double or triple clicking of M-Mouse-1 operates on words and lines, much like Mouse-1.
If mouse-yank-at-point is non-nil, M-Mouse-2
yanks at point. Then it does not matter precisely where you click; all
that matters is which window you click on. See section Mouse Commands for Editing.
Some Emacs buffers display lists of various sorts. These include lists of files, of buffers, of possible completions, of matches for a pattern, and so on.
Since yanking text into these buffers is not very useful, most of them define Mouse-2 specially, as a command to use or view the item you click on.
For example, if you click Mouse-2 on a file name in a Dired buffer, you visit that file. If you click Mouse-2 on an error message in the `*Compilation*' buffer, you go to the source code for that error message. If you click Mouse-2 on a completion in the `*Completions*' buffer, you choose that completion.
You can usually tell when Mouse-2 has this special sort of meaning because the sensitive text highlights when you move the mouse over it.
Mouse clicks modified with the CTRL and SHIFT keys bring up menus.
You can use mouse clicks on window mode lines to select and manipulate windows.
C-Mouse-2 on a scroll bar splits the corresponding window vertically. See section Splitting Windows.
The prefix key C-x 5 is analogous to C-x 4, with parallel subcommands. The difference is that C-x 5 commands create a new frame rather than just a new window in the selected frame (See section Displaying in Another Window). If an existing visible or iconified frame already displays the requested material, these commands use the existing frame, after raising or deiconifying as necessary.
The various C-x 5 commands differ in how they find or create the buffer to select:
make-frame).
switch-to-buffer-other-frame.
find-file-other-frame. See section Visiting Files.
dired-other-frame. See section Dired, the Directory Editor.
mail-other-frame. It is the other-frame variant of C-x m.
See section Sending Mail.
find-tag-other-frame, the multiple-frame variant of M-..
See section Tags Tables.
find-file-read-only-other-frame.
See section Visiting Files.
You can control the appearance of new frames you create by setting the
frame parameters in default-frame-alist. You can use the
variable initial-frame-alist to specify parameters that affect
only the initial frame. See section `Initial Parameters' in The Emacs Lisp Reference Manual, for more information.
An Emacs frame can have a speedbar, which is a vertical window that serves as a scrollable menu of files you could visit and tags within those files. To create a speedbar, type M-x speedbar; this creates a speedbar window for the selected frame. From then on, you can click on a file name in the speedbar to visit that file in the corresponding Emacs frame, or click on a tag name to jump to that tag in the Emacs frame.
Initially the speedbar lists the immediate contents of the current directory, one file per line. Each line also has a box, `[+]' or `<+>', that you can click on with Mouse-2 to "open up" the contents of that item. If the line names a directory, opening it adds the contents of that directory to the speedbar display, underneath the directory's own line. If the line lists an ordinary file, opening it up adds a list of the tags in that file to the speedbar display. When a file is opened up, the `[+]' changes to `[-]'; you can click on that box to "close up" that file (hide its contents).
Some major modes, including Rmail mode, Info, and GUD, have specialized ways of putting useful items into the speedbar for you to select. For example, in Rmail mode, the speedbar shows a list of Rmail files, and lets you move the current message to another Rmail file by clicking on its `<M>' box.
A speedbar belongs to one Emacs frame, and always operates on that frame. If you use multiple frames, you can make a speedbar for some or all of the frames; type M-x speedbar in any given frame to make a speedbar for it.
A single Emacs can talk to more than one X Windows display.
Initially, Emacs uses just one display--the one specified with the
DISPLAY environment variable or with the `--display' option
(see section Initial Options). To connect to another display, use the
command make-frame-on-display:
A single X server can handle more than one screen. When you open frames on two screens belonging to one server, Emacs knows they share a single keyboard, and it treats all the commands arriving from these screens as a single stream of input.
When you open frames on different X servers, Emacs makes a separate input stream for each server. This way, two users can type simultaneously on the two displays, and Emacs will not garble their input. Each server also has its own selected frame. The commands you enter with a particular X server apply to that server's selected frame.
Despite these features, people using the same Emacs job from different displays can still interfere with each other if they are not careful. For example, if any one types C-x C-c, that exits the Emacs job for all of them!
You can make certain chosen buffers, for which Emacs normally creates
a second window when you have just one window, appear in special frames
of their own. To do this, set the variable
special-display-buffer-names to a list of buffer names; any
buffer whose name is in that list automatically gets a special frame,
when an Emacs command wants to display it "in another window."
For example, if you set the variable this way,
(setq special-display-buffer-names
'("*Completions*" "*grep*" "*tex-shell*"))
then completion lists, grep output and the TeX mode shell
buffer get individual frames of their own. These frames, and the
windows in them, are never automatically split or reused for any other
buffers. They continue to show the buffers they were created for,
unless you alter them by hand. Killing the special buffer deletes its
frame automatically.
More generally, you can set special-display-regexps to a list
of regular expressions; then a buffer gets its own frame if its name
matches any of those regular expressions. (Once again, this applies only
to buffers that normally get displayed for you in a separate window.)
The variable special-display-frame-alist specifies the frame
parameters for these frames. It has a default value, so you don't need
to set it.
For those who know Lisp, an element of
special-display-buffer-names or special-display-regexps
can also be a list. Then the first element is the buffer name or
regular expression; the rest of the list specifies how to create the
frame. It can be an association list specifying frame parameter values;
these values take precedence over parameter values specified in
special-display-frame-alist. Alternatively, it can have this
form:
(function args...)
where function is a symbol. Then the frame is constructed by calling function; its first argument is the buffer, and its remaining arguments are args.
An analogous feature lets you specify buffers which should be
displayed in the selected window. See section Forcing Display in the Same Window. The
same-window feature takes precedence over the special-frame feature;
therefore, if you add a buffer name to
special-display-buffer-names and it has no effect, check to see
whether that feature is also in use for the same buffer name.
This section describes commands for altering the display style and window management behavior of the selected frame.
modeline face also, so
that it remains in inverse video compared with the default.
auto-raise-mode has no effect on
it.
auto-lower-mode has no effect on auto-lower
implemented by the X window manager. To control that, you must use
the appropriate window manager features.
In Emacs versions that use an X toolkit, the color-setting and font-setting functions don't affect menus and the menu bar, since they are displayed by their own widget classes. To change the appearance of the menus and menu bar, you must use X resources (see section X Resources). See section Window Color Options, regarding colors. See section Font Specification Options, regarding choice of font.
For information on frame parameters and customization, see section `Frame Parameters' in The Emacs Lisp Reference Manual.
When using X, Emacs normally makes a scroll bar at the left of each Emacs window. The scroll bar runs the height of the window, and shows a moving rectangular inner box which represents the portion of the buffer currently displayed. The entire height of the scroll bar represents the entire length of the buffer.
You can use Mouse-2 (normally, the middle button) in the scroll bar to move or drag the inner box up and down. If you move it to the top of the scroll bar, you see the top of the buffer. If you move it to the bottom of the scroll bar, you see the bottom of the buffer.
The left and right buttons in the scroll bar scroll by controlled increments. Mouse-1 (normally, the left button) moves the line at the level where you click up to the top of the window. Mouse-3 (normally, the right button) moves the line at the top of the window down to the level where you click. By clicking repeatedly in the same place, you can scroll by the same distance over and over.
Aside from scrolling, you can also click C-Mouse-2 in the scroll bar to split a window vertically. The split occurs on the line where you click.
You can enable or disable Scroll Bar mode with the command M-x scroll-bar-mode. With no argument, it toggles the use of scroll bars. With an argument, it turns use of scroll bars on if and only if the argument is positive. This command applies to all frames, including frames yet to be created. You can use the X resource `verticalScrollBars' to control the initial setting of Scroll Bar mode. See section X Resources.
To enable or disable scroll bars for just the selected frame, use the M-x toggle-scroll-bar command.
You can turn display of menu bars on or off with M-x menu-bar-mode. With no argument, this command toggles Menu Bar mode, a minor mode. With an argument, the command turns Menu Bar mode on if the argument is positive, off if the argument is not positive. You can use the X resource `menuBarLines' to control the initial setting of Menu Bar mode. See section X Resources. Expert users often turn off the menu bar, especially on text-only terminals, where this makes one additional line available for text.
See section The Menu Bar for information on how to invoke commands with the menu bar.
When using Emacs with X, you can set up multiple styles of displaying characters. The aspects of style that you can control are the type font, the foreground color, the background color, and whether to underline. Emacs on MS-DOS supports faces partially by letting you control the foreground and background colors of each face (see section Emacs and MS-DOS).
The way you control display style is by defining named faces. Each face can specify a type font, a foreground color, a background color, and an underline flag; but it does not have to specify all of them.
The style of display used for a given character in the text is determined by combining several faces. Any aspect of the display style that isn't specified by overlays or text properties comes from the frame itself.
Enriched mode, the mode for editing formatted text, includes several commands and menus for specifying faces. See section Faces in Formatted Text, for how to specify the font for text in the buffer. See section Colors in Formatted Text, for how to specify the foreground and background color.
To alter the appearance of a face, use the customization buffer. See section Customizing Faces. You can also use X resources to specify attributes of particular faces (see section X Resources).
To see what faces are currently defined, and what they look like, type M-x list-faces-display. It's possible for a given face to look different in different frames; this command shows the appearance in the frame in which you type it. Here's a list of the standardly defined faces:
default
modeline
highlight
region
secondary-selection
bold
italic
bold-italic
underline
When Transient Mark mode is enabled, the text of the region is
highlighted when the mark is active. This uses the face named
region; you can control the style of highlighting by changing the
style of this face (see section Customizing Faces). See section Transient Mark Mode,
for more information about Transient Mark mode and activation and
deactivation of the mark.
One easy way to use faces is to turn on Font Lock mode. This minor mode, which is always local to a particular buffer, arranges to choose faces according to the syntax of the text you are editing. It can recognize comments and strings in most languages; in several languages, it can also recognize and properly highlight various other important constructs. See section Font Lock mode, for more information about Font Lock mode and syntactic highlighting.
You can print out the buffer with the highlighting that appears
on your screen using the command ps-print-buffer-with-faces.
See section Postscript Hardcopy.
Font Lock mode is a minor mode, always local to a particular buffer, which highlights (or "fontifies") using various faces according to the syntax of the text you are editing. It can recognize comments and strings in most languages; in several languages, it can also recognize and properly highlight various other important constructs--for example, names of functions being defined or reserved keywords.
The command M-x font-lock-mode turns Font Lock mode on or off
according to the argument, and toggles the mode when it has no argument.
The function turn-on-font-lock unconditionally enables Font Lock
mode. This is useful in mode-hook functions. For example, to enable
Font Lock mode whenever you edit a C file, you can do this:
(add-hook 'c-mode-hook 'turn-on-font-lock)
To turn on Font Lock mode automatically in all modes which support it,
use the function global-font-lock-mode, like this:
(global-font-lock-mode t)
In Font Lock mode, when you edit the text, the highlighting updates
automatically in the line that you changed. Most changes don't affect
the highlighting of subsequent lines, but occasionally they do. To
rehighlight a range of lines, use the command M-g M-g
(font-lock-fontify-block).
In certain major modes, M-g M-g refontifies the entire current
function. (The variable font-lock-mark-block-function controls
how to find the current function.) In other major modes, M-g M-g
refontifies 16 lines above and below point.
With a prefix argument n, M-g M-g refontifies n lines above and below point, regardless of the mode.
To get the full benefit of Font Lock mode, you need to choose a default font which has bold, italic, and bold-italic variants; or else you need to have a color or gray-scale screen.
The variable font-lock-maximum-decoration specifies the
preferred level of fontification, for modes that provide multiple
levels. Level 1 is the least amount of fontification; some modes
support levels as high as 3. The normal default is "as high as
possible." You can specify an integer, which applies to all modes, or
you can specify different numbers for particular major modes; for
example, to use level 1 for C/C++ modes, and the default level
otherwise, use this:
(setq font-lock-maximum-decoration
'((c-mode . 1) (c++-mode . 1)))
Fontification can be too slow for large buffers, so you can suppress
it. The variable font-lock-maximum-size specifies a buffer size,
beyond which buffer fontification is suppressed.
Comment and string fontification (or "syntactic" fontification) relies on analysis of the syntactic structure of the buffer text. For the purposes of speed, some modes including C mode and Lisp mode rely on a special convention: an open-parenthesis in the leftmost column always defines the beginning of a defun, and is thus always outside any string or comment. (See section Defuns.) If you don't follow this convention, then Font Lock mode can misfontify the text after an open-parenthesis in the leftmost column that is inside a string or comment.
The variable font-lock-beginning-of-syntax-function (always
buffer-local) specifies how Font Lock mode can find a position
guaranteed to be outside any comment or string. In modes which use the
leftmost column parenthesis convention, the default value of the variable
is beginning-of-defun---that tells Font Lock mode to use the
convention. If you set this variable to nil, Font Lock no longer
relies on the convention. This avoids incorrect results, but the price
is that, in some cases, fontification for a changed text must rescan
buffer text from the beginning of the buffer.
Font Lock highlighting patterns already exist for many modes, but you
may want to fontify additional patterns. You can use the function
font-lock-add-keywords, to add your own highlighting patterns for
a particular mode. For example, to highlight `FIXME:' words in C
comments, use this:
(font-lock-add-keywords
'c-mode
'(("\\<\\(FIXME\\):" 1 font-lock-warning-face t)))
Font Lock support modes make Font Lock mode faster for large buffers. There are two support modes: Fast Lock mode and Lazy Lock mode. They use two different methods of speeding up Font Lock mode.
To make Font Lock mode faster for buffers visiting large files, you can use Fast Lock mode. Fast Lock mode saves the font information for each file in a separate cache file; each time you visit the file, it rereads the font information from the cache file instead of refontifying the text from scratch.
The command M-x fast-lock-mode turns Fast Lock mode on or off, according to the argument (with no argument, it toggles). You can also arrange to enable Fast Lock mode whenever you use Font Lock mode, like this:
(setq font-lock-support-mode 'fast-lock-mode)
It is not worth writing a cache file for small buffers. Therefore,
the variable fast-lock-minimum-size specifies a minimum file size
for caching font information.
The variable fast-lock-cache-directories specifies where to put
the cache files. Its value is a list of directories to try; "."
means the same directory as the file being edited. The default value is
("." "~/.emacs-flc"), which means to use the same directory if
possible, and otherwise the directory `~/.emacs-flc'.
The variable fast-lock-save-others specifies whether Fast Lock
mode should save cache files for files that you do not own. A
non-nil value means yes (and that is the default).
To make Font Lock mode faster for large buffers, you can use Lazy Lock mode to reduce the amount of text that is fontified. In Lazy Lock mode, buffer fontification is demand-driven; it happens to portions of the buffer that are about to be displayed. And fontification of your changes is deferred; it happens only when Emacs has been idle for a certain short period of time.
The command M-x lazy-lock-mode turns Lazy Lock mode on or off, according to the argument (with no argument, it toggles). You can also arrange to enable Lazy Lock mode whenever you use Font Lock mode, like this:
(setq font-lock-support-mode 'lazy-lock-mode)
It is not worth avoiding buffer fontification for small buffers.
Therefore, the variable lazy-lock-minimum-size specifies a
minimum buffer size for demand-driven buffer fontification. Buffers
smaller than that are fontified all at once, as in plain Font Lock mode.
When you alter the buffer, Lazy Lock mode defers fontification of the
text you changed. The variable lazy-lock-defer-time specifies
how many seconds Emacs must be idle before it starts fontifying your
changes. If the value is 0, then changes are fontified immediately, as
in plain Font Lock mode.
Lazy Lock mode normally fontifies newly visible portions of the buffer
before they are first displayed. However, if the value of
lazy-lock-defer-on-scrolling is non-nil, newly visible
text is fontified only when Emacs is idle for
lazy-lock-defer-time seconds.
In some modes, including C mode and Emacs Lisp mode, changes in one
line's contents can alter the context for subsequent lines, and thus
change how they ought to be fontified. Ordinarily, you must type
M-g M-g to refontify the subsequent lines. However, if you set
the variable lazy-lock-defer-contextually to non-nil, Lazy
Lock mode does this automatically, after lazy-lock-defer-time
seconds.
When Emacs is idle for a long time, Lazy Lock fontifies additional portions of the buffer, not yet displayed, in case you will display them later. This is called stealth fontification.
The variable lazy-lock-stealth-time specifies how many seconds
Emacs has to be idle before stealth fontification starts. A value of
nil means no stealth fontification. The variables
lazy-lock-stealth-lines and lazy-lock-stealth-verbose
specify the granularity and verbosity of stealth fontification.
Here is a simple guide to help you choose one of the Font Lock support modes.
The variable font-lock-support-mode specifies which of these
support modes to use; for example, to specify that Fast Lock mode is
used for C/C++ modes, and Lazy Lock mode otherwise, set the variable
like this:
(setq font-lock-support-mode
'((c-mode . fast-lock-mode) (c++-mode . fast-lock-mode)
(t . lazy-lock-mode)))
Use M-x highlight-changes-mode to enable a minor mode that uses faces (colors, typically) to indicate which parts of the buffer were changed most recently.
The following commands let you create, delete and operate on frames:
iconify-or-deiconify-frame).
The normal meaning of C-z, to suspend Emacs, is not useful under a
window system, so it has a different binding in that case.
If you type this command on an Emacs frame's icon, it deiconifies the frame.
delete-frame). This is not allowed if
there is only one frame.
If your terminal does not have a window system that Emacs supports, then it can display only one Emacs frame at a time. However, you can still create multiple Emacs frames, and switch between them. Switching frames on these terminals is much like switching between different window configurations.
Use C-x 5 2 to create a new frame and switch to it; use C-x 5 o to cycle through the existing frames; use C-x 5 0 to delete the current frame.
Each frame has a number to distinguish it. If your terminal can display only one frame at a time, the selected frame's number n appears near the beginning of the mode line, in the form `Fn'.
`Fn' is actually the frame's name. You can also specify a different name if you wish, and you can select a frame by its name. Use the command M-x set-frame-name RET name RET to specify a new name for the selected frame, and use M-x select-frame-by-name RET name RET to select a frame according to its name. The name you specify appears in the mode line when the frame is selected.
Emacs supports a wide variety of international character sets, including European variants of the Latin alphabet, as well as Chinese, Devanagari (Hindi and Marathi), Ethiopian, Greek, IPA, Japanese, Korean, Lao, Russian, Thai, Tibetan, and Vietnamese scripts. These features have been merged from the modified version of Emacs known as MULE (for "MULti-lingual Enhancement to GNU Emacs")
The users of these scripts have established many more-or-less standard coding systems for storing files. Emacs internally uses a single multibyte character encoding, so that it can intermix characters from all these scripts in a single buffer or string. This encoding represents each non-ASCII character as a sequence of bytes in the range 0200 through 0377. Emacs translates between the multibyte character encoding and various other coding systems when reading and writing files, when exchanging data with subprocesses, and (in some cases) in the C-q command (see below).
The command C-h h (view-hello-file) displays the file
`etc/HELLO', which shows how to say "hello" in many languages.
This illustrates various scripts.
Keyboards, even in the countries where these character sets are used, generally don't have keys for all the characters in them. So Emacs supports various input methods, typically one for each script or language, to make it convenient to type them.
The prefix key C-x RET is used for commands that pertain to multibyte characters, coding systems, and input methods.
You can enable or disable multibyte character support, either for Emacs as a whole, or for a single buffer. When multibyte characters are disabled in a buffer, then each byte in that buffer represents a character, even codes 0200 through 0377. The old features for supporting the European character sets, ISO Latin-1 and ISO Latin-2, work as they did in Emacs 19.
However, there is no need to turn off multibyte character support to use ISO Latin-1 or ISO Latin-2; the Emacs multibyte character set includes all the characters in these character sets, and Emacs can translate automatically to and from either of these ISO codes.
To edit a particular file in unibyte representation, visit it using
find-file-literally. See section Visiting Files. To convert a buffer in
multibyte representation into a single-byte representation of the same
characters, the easiest way is to save the contents in a file, kill the
buffer, and find the file again with find-file-literally.
To turn off multibyte character support by default, start Emacs with the `--unibyte' option (see section Initial Options), or set the environment variable `EMACS_UNIBYTE'.
The mode line indicates whether multibyte character support is enabled in the current buffer. If it is, there are two or more characters (most often two dashes) before the colon near the beginning of the mode line. When multibyte characters are not enabled, just one dash precedes the colon.
When multibyte characters are enabled, character codes 0240 (octal) through 0377 (octal) are not really legitimate in the buffer. The valid non-ASCII printing characters have codes that start from 0400.
If you type a self-inserting character in the invalid range 0240 through 0377, Emacs assumes you intended to use one of the ISO Latin-n character sets, and converts it to the Emacs code representing that Latin-n character. You select which ISO Latin character set to use though your choice of language environment (see below). If you do not specify a choice, the default is Latin-1.
The same thing happens when you use C-q to enter an octal code in this range.
All supported character sets are supported in Emacs buffers whenever multibyte characters are enabled; there is no need to select a particular language in order to display its characters in an Emacs buffer. However, it is important to select a language environment in order to set various defaults. The language environment really represents a choice of preferred script (more or less) rather that a choice of language.
The language environment controls which coding systems to recognize when reading text (see section Recognizing Coding Systems). This applies to files, incoming mail, netnews, and any other text you read into Emacs. It may also specify the default coding system to use when you create a file. Each language environment also specifies a default input method.
The way to select a language environment is with the command M-x set-language-environment. It makes no difference which buffer is current when you use this command, because the effects apply globally to the Emacs session. The supported language environments include:
Chinese-BIG5, Chinese-CNS, Chinese-GB, Cyrillic-Alternativnyj, Cyrillic-ISO, Cyrillic-KOI8, Devanagari, English, Ethiopic, Greek, Hebrew, Japanese, Korean, Lao, Latin-1, Latin-2, Latin-3, Latin-4, Latin-5, Thai, Tibetan, and Vietnamese.
Some operating systems let you specify the language you are using by setting locale environment variables. Emacs handles one common special case of this: if your locale name for character types contains the string `8859-n', Emacs automatically selects the corresponding language environment.
To display information about the effects of a certain language
environment lang-env, use the command C-h L lang-env
RET (describe-language-environment). This tells you which
languages this language environment is useful for, and lists the
character sets, coding systems, and input methods that go with it. It
also shows some sample text to illustrate scripts used in this language
environment. By default, this command describes the chosen language
environment.
You can customize any language environment with the normal hook
set-language-environment-hook. The command
set-language-environment runs that hook after setting up the new
language environment. The hook functions can test for a specific
language environment by checking the variable
current-language-environment.
Before it starts to set up the new language environment,
set-language-environment first runs the hook
exit-language-environment-hook. This hook is useful for undoing
customizations that were made with set-language-environment-hook.
For instance, if you set up a special key binding in a specific language
environment using set-language-environment-hook, you should set
up exit-language-environment-hook to restore the normal binding
for that key.
An input method is a kind of character conversion designed specifically for interactive input. In Emacs, typi