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GNU Info File | 1994-10-06 | 44.4 KB | 1,065 lines

This is Info file ../info/emacs, produced by Makeinfo-1.54 from the input file emacs.texi. File: emacs, Node: Remote Host, Prev: Shell Options, Up: Shell Remote Host Shell ----------------- Emacs provides two commands for logging in to another computer and communicating with it through an Emacs buffer. `M-x telnet RET HOSTNAME RET' Set up a Telnet connection to the computer named HOSTNAME. `M-x rlogin RET HOSTNAME RET' Set up an Rlogin connection to the computer named HOSTNAME. Use `M-x telnet' to set up a Telnet connection to another computer. (Telnet is the standard Internet protocol for remote login.) It reads the host name of the other computer as an argument with the minibuffer. Once the connection is established, talking to the other computer works like talking to a subshell: you can edit input with the usual Emacs commands, and send it a line at a time by typing RET. The output is inserted in the Telnet buffer interspersed with the input. Use `M-x rlogin' to set up an Rlogin connection. Rlogin is another remote login communication protocol, essentially much like the Telnet protocol but incompatible with it, and supported only by certain systems. Rlogin's advantages are that you can arrange not to have to give your user name and password when communicating between two machines you frequently use, and that you can make an 8-bit-clean connection. (To do that in Emacs, set `rlogin-explicit-args' to `("-8")' before you run Rlogin.) `M-x rlogin' sets up the default file directory of the Emacs buffer to access the remote host via FTP (*note File Names::.), and it tracks the shell commands that change the current directory just like Shell mode. File: emacs, Node: Emacs Server, Next: Hardcopy, Prev: Shell, Up: Top Using Emacs as a Server ======================= Various programs such as `mail' can invoke your choice of editor to edit a particular piece of text, such as a message that you are sending. By convention, these programs use the environment variable `EDITOR' to specify which editor to run. If you set `EDITOR' to `emacs', they invoke Emacs--but in an inconvenient fashion, by starting a new, separate Emacs process. This is inconvenient because it takes time and because the new Emacs process doesn't share the buffers in the existing Emacs process. You can arrange to use your existing Emacs process as the editor for programs like `mail' by using the Emacs client and Emacs server programs. Here is how. First, the preparation. Within Emacs, call the function `server-start'. (Your `.emacs' file can do this automatically if you add the expression `(server-start)' to it.) Then, outside Emacs, set the `EDITOR' environment variable to `emacsclient'. Then, whenever any program invokes your specified `EDITOR' program, the effect is to send a message to your principal Emacs telling it to visit a file. (That's what the program `emacsclient' does.) Emacs obeys silently; it does not immediately switch to the new file's buffer. When you want to do that, type `C-x #' (`server-edit'). When you've finished editing that buffer, type `C-x #' again. This saves the file and sends a message back to the `emacsclient' program telling it to exit. The programs that use `EDITOR' wait for the "editor" (actually, `emacsclient') to exit. `C-x #' also checks to see if any other files are pending for you to edit, and selects the next one. You can switch to a server buffer manually if you wish; you don't have to arrive at it with `C-x #'. But `C-x #' is the only way to say that you are "finished" with one. If you set the variable `server-window' to a window or a frame, `C-x #' displays the server buffer in that window or in that frame. While `mail' or another application is waiting for `emacsclient' to finish, `emacsclient' does not read terminal input. So the terminal that `mail' was using is effectively blocked for the duration. In order to edit with your principal Emacs, you need to be able to use it without using that terminal. There are two ways to do this: * Using a window system, run `mail' and the principal Emacs in two separate windows. While `mail' is waiting for `emacsclient', the window where it was running is blocked, but you can use Emacs by switching windows. * Use Shell mode in Emacs to run the other program such as `mail'; then, `emacsclient' blocks only the subshell under Emacs, and you can still use Emacs to edit the file. Some programs write temporary files for you to edit. After you edit the temporary file, the program reads it back and deletes it. If the Emacs server is later asked to edit the same file name, it should assume this has nothing to do with the previous occasion for that file name. The server accomplishes this by killing the temporary file's buffer when you finish with the file. Use the variable `server-temp-file-regexp' to specify which files are temporary in this sense; its value should be a regular expression that matches file names that are temporary. File: emacs, Node: Hardcopy, Next: Sorting, Prev: Emacs Server, Up: Top Hardcopy Output =============== The Emacs commands for making hardcopy let you print either an entire buffer or just part of one, either with or without page headers. See also the hardcopy commands of Dired (*note Misc File Ops::.) and the diary (*note Diary Commands::.). `M-x print-buffer' Print hardcopy of current buffer with page headings containing the file name and page number. `M-x lpr-buffer' Print hardcopy of current buffer without page headings. makes no page headings. `M-x print-region' Like `print-buffer' but print only the current region. `M-x lpr-region' Like `lpr-buffer' but print only the current region. All the hardcopy commands pass extra switches to the `lpr' program based on the value of the variable `lpr-switches'. Its value should be a list of strings, each string an option starting with `-'. For example, to use a printer named `nearme', set `lpr-switches' like this: (setq lpr-switches '("-Pnearme")) The variable `lpr-header-switches' similarly specifies the extra switches to use to make page headers. File: emacs, Node: Sorting, Next: Narrowing, Prev: Hardcopy, Up: Top Sorting Text ============ Emacs provides several commands for sorting text in the buffer. All operate on the contents of the region (the text between point and the mark). They divide the text of the region into many "sort records", identify a "sort key" for each record, and then reorder the records into the order determined by the sort keys. The records are ordered so that their keys are in alphabetical order, or, for numeric sorting, in numeric order. In alphabetic sorting, all upper case letters `A' through `Z' come before lower case `a', in accord with the ASCII character sequence. The various sort commands differ in how they divide the text into sort records and in which part of each record is used as the sort key. Most of the commands make each line a separate sort record, but some commands use paragraphs or pages as sort records. Most of the sort commands use each entire sort record as its own sort key, but some use only a portion of the record as the sort key. `M-x sort-lines' Divide the region into lines, and sort by comparing the entire text of a line. A numeric argument means sort into descending order. `M-x sort-paragraphs' Divide the region into paragraphs, and sort by comparing the entire text of a paragraph (except for leading blank lines). A numeric argument means sort into descending order. `M-x sort-pages' Divide the region into pages, and sort by comparing the entire text of a page (except for leading blank lines). A numeric argument means sort into descending order. `M-x sort-fields' Divide the region into lines, and sort by comparing the contents of one field in each line. Fields are defined as separated by whitespace, so the first run of consecutive non-whitespace characters in a line constitutes field 1, the second such run constitutes field 2, etc. Specify which field to sort by with a numeric argument: 1 to sort by field 1, etc. A negative argument means count fields from the right instead of from the left; thus, minus 1 means sort by the last field. If several lines have identical contents in the field being sorted, they keep same relative order that they had in the original buffer. A negative argument means count fields from the right (from the end of the line). `M-x sort-numeric-fields' Like `M-x sort-fields' except the specified field is converted to an integer for each line, and the numbers are compared. `10' comes before `2' when considered as text, but after it when considered as a number. `M-x sort-columns' Like `M-x sort-fields' except that the text within each line used for comparison comes from a fixed range of columns. See below for an explanation. `M-x reverse-region' Reverse the order of the lines in the region. This is useful for sorting into descending order by fields or columns, since those sort commands do not have a feature for doing that. For example, if the buffer contains this: On systems where clash detection (locking of files being edited) is implemented, Emacs also checks the first time you modify a buffer whether the file has changed on disk since it was last visited or saved. If it has, you are asked to confirm that you want to change the buffer. applying `M-x sort-lines' to the entire buffer produces this: On systems where clash detection (locking of files being edited) is implemented, Emacs also checks the first time you modify a buffer saved. If it has, you are asked to confirm that you want to change the buffer. whether the file has changed on disk since it was last visited or where the upper case `O' sorts before all lower case letters. If you use `C-u 2 M-x sort-fields' instead, you get this: implemented, Emacs also checks the first time you modify a buffer saved. If it has, you are asked to confirm that you want to change the buffer. On systems where clash detection (locking of files being edited) is whether the file has changed on disk since it was last visited or where the sort keys were `Emacs', `If', `buffer', `systems' and `the'. `M-x sort-columns' requires more explanation. You specify the columns by putting point at one of the columns and the mark at the other column. Because this means you cannot put point or the mark at the beginning of the first line to sort, this command uses an unusual definition of `region': all of the line point is in is considered part of the region, and so is all of the line the mark is in, as well as all the lines in between. For example, to sort a table by information found in columns 10 to 15, you could put the mark on column 10 in the first line of the table, and point on column 15 in the last line of the table, and then run `sort-columns'. Equivalently, you could run it with the mark on column 15 in the first line and point on column 10 in the last line. This can be thought of as sorting the rectangle specified by point and the mark, except that the text on each line to the left or right of the rectangle moves along with the text inside the rectangle. *Note Rectangles::. Many of the sort commands ignore case differences when comparing, if `sort-fold-case' is non-`nil'. File: emacs, Node: Narrowing, Next: Two-Column, Prev: Sorting, Up: Top Narrowing ========= "Narrowing" means focusing in on some portion of the buffer, making the rest temporarily inaccessible. The portion which you can still get to is called the "accessible portion". Canceling the narrowing, which makes the entire buffer once again accessible, is called "widening". The amount of narrowing in effect in a buffer at any time is called the buffer's "restriction". Narrowing can make it easier to concentrate on a single subroutine or paragraph by eliminating clutter. It can also be used to restrict the range of operation of a replace command or repeating keyboard macro. `C-x n n' Narrow down to between point and mark (`narrow-to-region'). `C-x n w' Widen to make the entire buffer accessible again (`widen'). `C-x n p' Narrow down to the current page (`narrow-to-page'). When you have narrowed down to a part of the buffer, that part appears to be all there is. You can't see the rest, you can't move into it (motion commands won't go outside the accessible part), you can't change it in any way. However, it is not gone, and if you save the file all the inaccessible text will be saved. The word `Narrow' appears in the mode line whenever narrowing is in effect. The primary narrowing command is `C-x n n' (`narrow-to-region'). It sets the current buffer's restrictions so that the text in the current region remains accessible but all text before the region or after the region is inaccessible. Point and mark do not change. Alternatively, use `C-x n p' (`narrow-to-page') to narrow down to the current page. *Note Pages::, for the definition of a page. The way to cancel narrowing is to widen with `C-x n w' (`widen'). This makes all text in the buffer accessible again. You can get information on what part of the buffer you are narrowed down to using the `C-x =' command. *Note Position Info::. Because narrowing can easily confuse users who do not understand it, `narrow-to-region' is normally a disabled command. Attempting to use this command asks for confirmation and gives you the option of enabling it; if you enable the command, confirmation will no longer be required for it. *Note Disabling::. File: emacs, Node: Two-Column, Next: Editing Binary Files, Prev: Narrowing, Up: Top Two-Column Editing ================== Two-column mode lets you conveniently edit two side-by-side columns of text. It uses two side-by-side windows, each showing its own buffer. There are three ways to enter two-column mode: `C-x 6 2' Enter two-column mode with the current buffer on the left, and on the right, a buffer whose name is based on the current buffer's name (`tc-two-columns'). If the right-hand buffer doesn't already exist, it starts out empty; the current buffer's contents are not changed. This command is appropriate when the current buffer contains just one column and you want to add another column. `C-x 6 s' Split the current buffer, which contains two-column text, into two buffers, and display them side by side (`tc-split'). The current buffer becomes the left-hand buffer, but the text in the right-hand column is moved into the right-hand buffer. The current column specifies the split point. Splitting starts with the current line and continues to the end of the buffer. This command is appropriate when you have a buffer that already contains two-column text, and you wish to separate the columns temporarily. `C-x 6 b BUFFER RET' Enter two-column mode using the current buffer as the left-hand buffer, and using buffer BUFFER as the right-hand buffer (`tc-associate-buffer'). `C-x 6 s' looks for a column separator which is a string that appears on each line between the two columns. You can specify the width of the separator with a numeric argument to `C-x 6 s'; that many characters, before point, constitute the separator string. By default, the width is 1, so the column separator is the character before point. When a line has the separator at the proper place, `C-x 6 s' puts the text after the separator into the right-hand buffer, and deletes the separator. Lines that don't have the column separator at the proper place remain unsplit; they stay in the left-hand buffer, and the right-hand buffer gets an empty line to correspond. (This is the way to write a line that spans both columns while in two-column mode: write it in the left-hand buffer, and put an empty line in the right-hand buffer.) It's not a good idea to use ordinary scrolling commands during two-column editing, because that separates the two parts of each split line. Instead, use these special scroll commands: `C-x 6 SPC' Scroll both buffers up, in lock step (`tc-scroll-up'). `C-x 6 DEL' Scroll both buffers down, in lock step (`tc-scroll-down'). `C-x 6 C-l' Recenter both buffers, in lock step (`tc-recenter'). When you have edited both buffers as you wish, merge them with `C-x 6 1' (`tc-merge'). This copies the text from the right-hand buffer as a second column in the other buffer. To go back to two-column editing, use `C-x 6 s'. Use `C-x 6 d' to disassociate the two buffers, leaving each as it stands (`tc-dissociate'). If the other buffer, the one not current when you type `C-x 6 d', is empty, `C-x 6 d' kills it. File: emacs, Node: Editing Binary Files, Next: Saving Emacs Sessions, Prev: Two-Column, Up: Top Editing Binary Files ==================== There is a special major mode for editing binary files: Hexl mode. To use it, use `M-x hexl-find-file' instead of `C-x C-f' to visit the file. This command converts the file's contents to hexadecimal and lets you edit the translation. When you save the file, it is converted automatically back to binary. You can also use `M-x hexl-mode' to translate an existing buffer into hex. This is useful if you visit a file normally and then discover it is a binary file. Ordinary text characters overwrite in Hexl mode. This is to reduce the risk of accidentally spoiling the alignment of data in the file. There are special commands for insertion. Here is a list of the commands of Hexl mode: `C-M-d' Insert a byte with a code typed in decimal. `C-M-o' Insert a byte with a code typed in octal. `C-M-x' Insert a byte with a code typed in hex. `C-x [' Move to the beginning of a 1k-byte "page". `C-x ]' Move to the end of a 1k-byte "page". `M-g' Move to an address specified in hex. `M-j' Move to an address specified in decimal. `C-c C-c' Leave Hexl mode, going back to the major mode this buffer had before you invoked `hexl-mode'. File: emacs, Node: Saving Emacs Sessions, Next: Recursive Edit, Prev: Editing Binary Files, Up: Top Saving Emacs Sessions ===================== You can use the Desktop library to save the state of Emacs from one session to another. Saving the state means that Emacs starts up with the same set of buffers, major modes, buffer positions, and so on that the previous Emacs session had. To use Desktop, you should first add these lines to your `.emacs' file, preferably at or near the end: (load "desktop") (desktop-load-default) (desktop-read) Then, to enable state saving in a particular Emacs session, use the command `M-x desktop-save'. Once you have done this, the state of this Emacs session will be saved when you exit Emacs. In order for Emacs to recover the state from a previous session, you must start it with the same current directory as you used when you started the previous session. File: emacs, Node: Recursive Edit, Next: Emulation, Prev: Saving Emacs Sessions, Up: Top Recursive Editing Levels ======================== A "recursive edit" is a situation in which you are using Emacs commands to perform arbitrary editing while in the middle of another Emacs command. For example, when you type `C-r' inside of a `query-replace', you enter a recursive edit in which you can change the current buffer. On exiting from the recursive edit, you go back to the `query-replace'. "Exiting" the recursive edit means returning to the unfinished command, which continues execution. The command to exit is `C-M-c' (`exit-recursive-edit'). You can also "abort" the recursive edit. This is like exiting, but also quits the unfinished command immediately. Use the command `C-]' (`abort-recursive-edit') to do this. *Note Quitting::. The mode line shows you when you are in a recursive edit by displaying square brackets around the parentheses that always surround the major and minor mode names. Every window's mode line shows this, in the same way, since being in a recursive edit is true of Emacs as a whole rather than any particular window or buffer. It is possible to be in recursive edits within recursive edits. For example, after typing `C-r' in a `query-replace', you may type a command that enters the debugger. This begins a recursive editing level for the debugger, within the recursive editing level for `C-r'. Mode lines display a pair of square brackets for each recursive editing level currently in progress. Exiting the inner recursive edit (such as, with the debugger `c' command) resumes the command running in the next level up. When that command finishes, you can then use `C-M-c' to exit another recursive editing level, and so on. Exiting applies to the innermost level only. Aborting also gets out of only one level of recursive edit; it returns immediately to the command level of the previous recursive edit. If you wish, you can then abort the next recursive editing level. Alternatively, the command `M-x top-level' aborts all levels of recursive edits, returning immediately to the top level command reader. The text being edited inside the recursive edit need not be the same text that you were editing at top level. It depends on what the recursive edit is for. If the command that invokes the recursive edit selects a different buffer first, that is the buffer you will edit recursively. In any case, you can switch buffers within the recursive edit in the normal manner (as long as the buffer-switching keys have not been rebound). You could probably do all the rest of your editing inside the recursive edit, visiting files and all. But this could have surprising effects (such as stack overflow) from time to time. So remember to exit or abort the recursive edit when you no longer need it. In general, we try to minimize the use of recursive editing levels in GNU Emacs. This is because they constrain you to "go back" in a particular order-from the innermost level toward the top level. When possible, we present different activities in separate buffers so that you can switch between them as you please. Some commands switch to a new major mode which provides a command to switch back. These approaches give you more flexibility to go back to unfinished tasks in the order you choose. File: emacs, Node: Emulation, Next: Dissociated Press, Prev: Recursive Edit, Up: Top Emulation ========= GNU Emacs can be programmed to emulate (more or less) most other editors. Standard facilities can emulate these: EDT (DEC VMS editor) Turn on EDT emulation with `M-x edt-emulation-on'. `M-x edt-emulation-off' restores normal Emacs command bindings. Most of the EDT emulation commands are keypad keys, and most standard Emacs key bindings are still available. The EDT emulation rebindings are done in the global keymap, so there is no problem switching buffers or major modes while in EDT emulation. vi (Berkeley editor) Turn on vi emulation with `M-x vi-mode'. This is a major mode that replaces the previously established major mode. All of the vi commands that, in real vi, enter "input" mode are programmed in the Emacs emulator to return to the previous major mode. Thus, ordinary Emacs serves as vi's "input" mode. Because vi emulation works through major modes, it does not work to switch buffers during emulation. Return to normal Emacs first. If you plan to use vi emulation much, you probably want to bind a key to the `vi-mode' command. vi (alternate emulator) Another vi emulator said to resemble real vi more thoroughly is invoked by `M-x vip-mode'. "Input" mode in this emulator is changed from ordinary Emacs so you can use ESC to go back to emulated vi command mode. To get from emulated vi command mode back to ordinary Emacs, type `C-z'. This emulation does not work through major modes, and it is possible to switch buffers in various ways within the emulator. It is not so necessary to assign a key to the command `vip-mode' as it is with `vi-mode' because terminating insert mode does not use it. For full information, see the long comment at the beginning of the source file, which is `lisp/vip.el' in the Emacs distribution. I am interested in hearing which vi emulator users prefer, as well as in receiving more complete user documentation for either or both emulators. Warning: loading both vi emulators at once may cause name conflicts; no one has checked. File: emacs, Node: Dissociated Press, Next: Amusements, Prev: Emulation, Up: Top Dissociated Press ================= `M-x dissociated-press' is a command for scrambling a file of text either word by word or character by character. Starting from a buffer of straight English, it produces extremely amusing output. The input comes from the current Emacs buffer. Dissociated Press writes its output in a buffer named `*Dissociation*', and redisplays that buffer after every couple of lines (approximately) so you can read the output as it comes out. Dissociated Press asks every so often whether to continue generating output. Answer `n' to stop it. You can also stop at any time by typing `C-g'. The dissociation output remains in the `*Dissociation*' buffer for you to copy elsewhere if you wish. Dissociated Press operates by jumping at random from one point in the buffer to another. In order to produce plausible output rather than gibberish, it insists on a certain amount of overlap between the end of one run of consecutive words or characters and the start of the next. That is, if it has just printed out `president' and then decides to jump to a different point in the file, it might spot the `ent' in `pentagon' and continue from there, producing `presidentagon'.(1) Long sample texts produce the best results. A positive argument to `M-x dissociated-press' tells it to operate character by character, and specifies the number of overlap characters. A negative argument tells it to operate word by word and specifies the number of overlap words. In this mode, whole words are treated as the elements to be permuted, rather than characters. No argument is equivalent to an argument of two. For your againformation, the output goes only into the buffer `*Dissociation*'. The buffer you start with is not changed. Dissociated Press produces nearly the same results as a Markov chain based on a frequency table constructed from the sample text. It is, however, an independent, ignoriginal invention. Dissociated Press techniquitously copies several consecutive characters from the sample between random choices, whereas a Markov chain would choose randomly for each word or character. This makes for more plausible sounding results, and runs faster. It is a mustatement that too much use of Dissociated Press can be a developediment to your real work. Sometimes to the point of outragedy. And keep dissociwords out of your documentation, if you want it to be well userenced and properbose. Have fun. Your buggestions are welcome. ---------- Footnotes ---------- (1) This dissociword actually appeared during the Vietnam War, when it was very appropriate. File: emacs, Node: Amusements, Next: Customization, Prev: Dissociated Press, Up: Top Other Amusements ================ If you are a little bit bored, you can try `M-x hanoi'. If you are considerably bored, give it a numeric argument. If you are very very bored, try an argument of 9. Sit back and watch. If you want a little more personal involvement, try `M-x gomoku', which plays the game Go Moku with you. `M-x blackbox' and `M-x mpuz' are two kinds of puzzles. `blackbox' challenges you to determine the location of objects inside a box by tomography. `mpuz' displays a multiplication puzzle with letters standing for digits in a code that you must guess--to guess a value, type a letter and then the digit you think it stands for. `M-x dunnet' runs an adventure-style exploration game, which is a bigger sort of puzzle. When you are frustrated, try the famous Eliza program. Just do `M-x doctor'. End each input by typing `RET' twice. When you are feeling strange, type `M-x yow'. File: emacs, Node: Customization, Next: Quitting, Prev: Amusements, Up: Top Customization ************* This chapter talks about various topics relevant to adapting the behavior of Emacs in minor ways. See `The Emacs Lisp Reference Manual' for how to make more far-reaching changes. All kinds of customization affect only the particular Emacs session that you do them in. They are completely lost when you kill the Emacs session, and have no effect on other Emacs sessions you may run at the same time or later. The only way an Emacs session can affect anything outside of it is by writing a file; in particular, the only way to make a customization `permanent' is to put something in your `.emacs' file or other appropriate file to do the customization in each session. *Note Init File::. * Menu: * Minor Modes:: Each minor mode is one feature you can turn on independently of any others. * Variables:: Many Emacs commands examine Emacs variables to decide what to do; by setting variables, you can control their functioning. * Keyboard Macros:: A keyboard macro records a sequence of keystrokes to be replayed with a single command. * Key Bindings:: The keymaps say what command each key runs. By changing them, you can "redefine keys". * Keyboard Translations:: If your keyboard passes an undesired code for a key, you can tell Emacs to substitute another code. * Syntax:: The syntax table controls how words and expressions are parsed. * Init File:: How to write common customizations in the `.emacs' file. File: emacs, Node: Minor Modes, Next: Variables, Up: Customization Minor Modes =========== Minor modes are optional features which you can turn on or off. For example, Auto Fill mode is a minor mode in which SPC breaks lines between words as you type. All the minor modes are independent of each other and of the selected major mode. Most minor modes say in the mode line when they are on; for example, `Fill' in the mode line means that Auto Fill mode is on. Append `-mode' to the name of a minor mode to get the name of a command function that turns the mode on or off. Thus, the command to enable or disable Auto Fill mode is called `M-x auto-fill-mode'. These commands are usually invoked with `M-x', but you can bind keys to them if you wish. With no argument, the function turns the mode on if it was off and off if it was on. This is known as "toggling". A positive argument always turns the mode on, and an explicit zero argument or a negative argument always turns it off. Enabling or disabling some minor modes applies only to the current buffer; each buffer is independent of the other buffers. Therefore, you can enable the mode in particular buffers and disable it in others. The per-buffer minor modes include Auto Fill mode, Outline minor mode, Auto Save mode, Font-Lock mode, and ISO Accents mode. Auto Fill mode allows you to enter filled text without breaking lines explicitly. Emacs inserts newlines as necessary to prevent lines from becoming too long. *Note Filling::. Outline minor mode provides the same facilities as the major mode called Outline mode; but since it is a minor mode instead, you can combine it with any major mode. *Note Outline Mode::. Overwrite mode causes ordinary printing characters to replace existing text instead of shoving it to the right. For example, if point is in front of the `B' in `FOOBAR', then in Overwrite mode typing a `G' changes it to `FOOGAR', instead of producing it `FOOGBAR' as usual. Auto Save mode causes the contents of a buffer to be saved periodically to reduce the amount of work you can lose in case of a system crash. *Note Auto Save::. Font-Lock mode automatically highlights certain textual units found in programs, such as comments, strings, and function names being defined. This requires a window system that can display multiple fonts. *Note Faces::. ISO Accents mode makes the characters ``', `'', `"', `^', `/' and `~' combine with the following letter, to produce an accented letter in the ISO Latin-1 character set. *Note European Display::. The following minor modes normally apply to all buffers at once. Since each is enabled or disabled by the value of a variable, you *can* set them differently for particular buffers, by explicitly making the corresponding variables local in those buffers. *Note Locals::. Abbrev mode allows you to define abbreviations that automatically expand as you type them. For example, `amd' might expand to `abbrev mode'. *Note Abbrevs::, for full information. Line Number mode enables continuous display in the mode line of the line number of point. *Note Mode Line::. Resize-Minibuffer mode makes the minibuffer expand as necessary to hold the text that you put in it. *Note Minibuffer Edit::. Scroll Bar mode gives each window a scroll bar (*note Scroll Bars::.). Menu Bar mode gives each frame a menu bar (*note Menu Bars::.). Both of these modes are enabled by default when you use the X Window System. In Transient Mark mode, every change in the buffer contents "deactivates" the mark, so that commands that operate on the region will get an error. This means you must either set the mark, or explicitly "reactivate" it, before each command that uses the region. The advantage of Transient Mark mode is that Emacs can display the region highlighted (currently only when using X). *Note Setting Mark::. File: emacs, Node: Variables, Next: Keyboard Macros, Prev: Minor Modes, Up: Customization Variables ========= A "variable" is a Lisp symbol which has a value. The symbol's name is also called the name of the variable. A variable name can contain any characters that can appear in a file, but conventionally variable names consist of words separated by hyphens. A variable can have a documentation string which describes what kind of value it should have and how the value will be used. Lisp allows any variable to have any kind of value, but most variables that Emacs uses require a value of a certain type. Often the value should always be a string, or should always be a number. Sometimes we say that a certain feature is turned on if a variable is "non-`nil'," meaning that if the variable's value is `nil', the feature is off, but the feature is on for *any* other value. The conventional value to use to turn on the feature--since you have to pick one particular value when you set the variable--is `t'. Emacs uses many Lisp variables for internal record keeping, as any Lisp program must, but the most interesting variables for you are the ones that exist for the sake of customization. Emacs does not (usually) change the values of these variables; instead, you set the values, and thereby alter and control the behavior of certain Emacs commands. These variables are called "options". Most options are documented in this manual, and appear in the Variable Index (*note Variable Index::.). One example of a variable which is an option is `fill-column', which specifies the position of the right margin (as a number of characters from the left margin) to be used by the fill commands (*note Filling::.). * Menu: * Examining:: Examining or setting one variable's value. * Edit Options:: Examining or editing list of all variables' values. * Hooks:: Hook variables let you specify programs for parts of Emacs to run on particular occasions. * Locals:: Per-buffer values of variables. * File Variables:: How files can specify variable values. File: emacs, Node: Examining, Next: Edit Options, Up: Variables Examining and Setting Variables ------------------------------- `C-h v VAR RET' Display the value and documentation of variable VAR (`describe-variable'). `M-x set-variable RET VAR RET VALUE RET' Change the value of variable VAR to VALUE. To examine the value of a single variable, use `C-h v' (`describe-variable'), which reads a variable name using the minibuffer, with completion. It displays both the value and the documentation of the variable. For example, C-h v fill-column RET displays something like this: fill-column's value is 75 Documentation: *Column beyond which automatic line-wrapping should happen. Automatically becomes buffer-local when set in any fashion. The star at the beginning of the documentation indicates that this variable is an option. `C-h v' is not restricted to options; it allows any variable name. The most convenient way to set a specific option is with `M-x set-variable'. This reads the variable name with the minibuffer (with completion), and then reads a Lisp expression for the new value using the minibuffer a second time. For example, M-x set-variable RET fill-column RET 75 RET sets `fill-column' to 75. You can set any variable with a Lisp expression using the function `setq'. Here's how to use it to set `fill-column': (setq fill-column 75) Setting variables, like all means of customizing Emacs except where otherwise stated, affects only the current Emacs session. File: emacs, Node: Edit Options, Next: Hooks, Prev: Examining, Up: Variables Editing Variable Values ----------------------- These two functions make it easy to display all the Emacs option variables, and to change some of them if you wish. `M-x list-options' Display a buffer listing names, values and documentation of all options. `M-x edit-options' Change option values by editing a list of options. `M-x list-options' displays a list of all Emacs option variables, in an Emacs buffer named `*List Options*'. Each option is shown with its documentation and its current value. Here is what a portion of it might look like: ;; exec-path: ("." "/usr/local/bin" "/usr/ucb" "/bin" "/usr/bin" "/u2/emacs/etc") *List of directories to search programs to run in subprocesses. Each element is a string (directory name) or nil (try the default directory). ;; ;; fill-column: 75 *Column beyond which automatic line-wrapping should happen. Automatically becomes buffer-local when set in any fashion. ;; `M-x edit-options' goes one step further and immediately selects the `*List Options*' buffer; this buffer uses the major mode Options mode, which provides commands that allow you to point at an option and change its value: `s' Set the variable point is in or near to a new value read using the minibuffer. `x' Toggle the variable point is in or near: if the value was `nil', it becomes `t'; otherwise it becomes `nil'. `1' Set the variable point is in or near to `t'. `0' Set the variable point is in or near to `nil'. `n' `p' Move to the next or previous variable. Any changes take effect immediately, and last until you exit from Emacs. File: emacs, Node: Hooks, Next: Locals, Prev: Edit Options, Up: Variables Hooks ----- A "hook" is a variable where you can store a function or functions to be called on a particular occasion by an existing program. Emacs provides a number of hooks for the sake of customization. Most of the hooks in Emacs are "normal hooks". These variables contain lists of functions to be called with no arguments. The reason most hooks are normal hooks is so that you can use them in a uniform way. Every variable in Emacs whose name ends in `-hook' is a normal hook. Most major modes run hooks as the last step of initialization. This makes it easy for a user to customize the behavior of the mode, by overriding the local variable assignments already made by the mode. But hooks may also be used in other contexts. For example, the hook `suspend-hook' runs just before Emacs suspends itself (*note Exiting::.). The recommended way to add a hook function to a normal hook is by calling `add-hook'. You can use any valid Lisp function as the hook function. For example, here's how to set up a hook to turn on Auto Fill mode when entering Text mode and other modes based on Text mode: (add-hook 'text-mode-hook 'turn-on-auto-fill) The next example shows how to use a hook to customize the indentation of C code. (People often have strong personal preferences for one format compared to another.) Here the hook function is an anonymous lambda expression. (add-hook 'c-mode-hook (function (lambda () (setq c-indent-level 4 c-argdecl-indent 0 c-label-offset -4 c-continued-statement-indent 0 c-brace-offset 0 comment-column 40)))) (setq c++-mode-hook c-mode-hook) It is best to design your hook functions so that the order in which they are executed does not matter. Any dependence on the order is "asking for trouble." However, the order is predictable: the most recently added hook functions are executed first. File: emacs, Node: Locals, Next: File Variables, Prev: Hooks, Up: Variables Local Variables --------------- `M-x make-local-variable RET VAR RET' Make variable VAR have a local value in the current buffer. `M-x kill-local-variable RET VAR RET' Make variable VAR use its global value in the current buffer. `M-x make-variable-buffer-local RET VAR RET' Mark variable VAR so that setting it will make it local to the buffer that is current at that time. Any variable can be made "local" to a specific Emacs buffer. This means that its value in that buffer is independent of its value in other buffers. A few variables are always local in every buffer. Every other Emacs variable has a "global" value which is in effect in all buffers that have not made the variable local. `M-x make-local-variable' reads the name of a variable and makes it local to the current buffer. Further changes in this buffer will not affect others, and further changes in the global value will not affect this buffer. `M-x make-variable-buffer-local' reads the name of a variable and changes the future behavior of the variable so that it will become local automatically when it is set. More precisely, once a variable has been marked in this way, the usual ways of setting the variable automatically do `make-local-variable' first. We call such variables "per-buffer" variables. Major modes (*note Major Modes::.) always make variables local to the buffer before setting the variables. This is why changing major modes in one buffer has no effect on other buffers. Minor modes also work by setting variables--normally, each minor mode has one controlling variable which is non-`nil' when the mode is enabled (*note Minor Modes::.). For most minor modes, the controlling variable is per buffer. Emacs contains a number of variables that are always per-buffer. These include `abbrev-mode', `auto-fill-function', `case-fold-search', `comment-column', `ctl-arrow', `fill-column', `fill-prefix', `indent-tabs-mode', `left-margin', `mode-line-format', `overwrite-mode', `selective-display-ellipses', `selective-display', `tab-width', and `truncate-lines'. Some other variables are always local in every buffer, but they are used for internal purposes. `M-x kill-local-variable' reads the name of a variable and makes it cease to be local to the current buffer. The global value of the variable henceforth is in effect in this buffer. Setting the major mode kills all the local variables of the buffer except for a few variables specially marked as "permanent locals". To set the global value of a variable, regardless of whether the variable has a local value in the current buffer, you can use the Lisp construct `setq-default'. This construct is used just like `setq', but it sets variables' global values instead of their local values (if any). When the current buffer does have a local value, the new global value may not be visible until you switch to another buffer. Here is an example: (setq-default fill-column 75) `setq-default' is the only way to set the global value of a variable that has been marked with `make-variable-buffer-local'. Lisp programs can use `default-value' to look at a variable's default value. This function takes a symbol as argument and returns its default value. The argument is evaluated; usually you must quote it explicitly. For example, here's how to obtain the default value of `fill-column': (default-value 'fill-column)