This is Info file elisp, produced by Makeinfo version 1.68 from the input file elisp.texi. INFO-DIR-SECTION Editors START-INFO-DIR-ENTRY * Elisp: (elisp). The Emacs Lisp Reference Manual. END-INFO-DIR-ENTRY This version is the edition 2.5 of the GNU Emacs Lisp Reference Manual. It corresponds to Emacs Version 20.3 Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998 Free Software Foundation, Inc. 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 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 this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is 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 section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English.  File: elisp, Node: Skipping Characters, Prev: List Motion, Up: Motion Skipping Characters ------------------- The following two functions move point over a specified set of characters. For example, they are often used to skip whitespace. For related functions, see *Note Motion and Syntax::. - Function: skip-chars-forward CHARACTER-SET &optional LIMIT This function moves point in the current buffer forward, skipping over a given set of characters. It examines the character following point, then advances point if the character matches CHARACTER-SET. This continues until it reaches a character that does not match. The function returns the number of characters moved over. The argument CHARACTER-SET is like the inside of a `[...]' in a regular expression except that `]' is never special and `\' quotes `^', `-' or `\'. Thus, `"a-zA-Z"' skips over all letters, stopping before the first nonletter, and `"^a-zA-Z"' skips nonletters stopping before the first letter. *Note Regular Expressions::. If LIMIT is supplied (it must be a number or a marker), it specifies the maximum position in the buffer that point can be skipped to. Point will stop at or before LIMIT. In the following example, point is initially located directly before the `T'. After the form is evaluated, point is located at the end of that line (between the `t' of `hat' and the newline). The function skips all letters and spaces, but not newlines. ---------- Buffer: foo ---------- I read "-!-The cat in the hat comes back" twice. ---------- Buffer: foo ---------- (skip-chars-forward "a-zA-Z ") => nil ---------- Buffer: foo ---------- I read "The cat in the hat-!- comes back" twice. ---------- Buffer: foo ---------- - Function: skip-chars-backward CHARACTER-SET &optional LIMIT This function moves point backward, skipping characters that match CHARACTER-SET, until LIMIT. It is just like `skip-chars-forward' except for the direction of motion. The return value indicates the distance traveled. It is an integer that is zero or less.  File: elisp, Node: Excursions, Next: Narrowing, Prev: Motion, Up: Positions Excursions ========== It is often useful to move point "temporarily" within a localized portion of the program, or to switch buffers temporarily. This is called an "excursion", and it is done with the `save-excursion' special form. This construct saves the current buffer and its values of point and the mark so they can be restored after the completion of the excursion. The forms for saving and restoring the configuration of windows are described elsewhere (see *Note Window Configurations::, and *note Frame Configurations::.). - Special Form: save-excursion FORMS... The `save-excursion' special form saves the identity of the current buffer and the values of point and the mark in it, evaluates FORMS, and finally restores the buffer and its saved values of point and the mark. All three saved values are restored even in case of an abnormal exit via `throw' or error (*note Nonlocal Exits::.). The `save-excursion' special form is the standard way to switch buffers or move point within one part of a program and avoid affecting the rest of the program. It is used more than 4000 times in the Lisp sources of Emacs. `save-excursion' does not save the values of point and the mark for other buffers, so changes in other buffers remain in effect after `save-excursion' exits. Likewise, `save-excursion' does not restore window-buffer correspondences altered by functions such as `switch-to-buffer'. One way to restore these correspondences, and the selected window, is to use `save-window-excursion' inside `save-excursion' (*note Window Configurations::.). The value returned by `save-excursion' is the result of the last of FORMS, or `nil' if no FORMS are given. (save-excursion FORMS) == (let ((old-buf (current-buffer)) (old-pnt (point-marker)) (old-mark (copy-marker (mark-marker)))) (unwind-protect (progn FORMS) (set-buffer old-buf) (goto-char old-pnt) (set-marker (mark-marker) old-mark))) *Warning:* Ordinary insertion of text adjacent to the saved point value relocates the saved value, just as it relocates all markers. Therefore, when the saved point value is restored, it normally comes before the inserted text. Although `save-excursion' saves the location of the mark, it does not prevent functions which modify the buffer from setting `deactivate-mark', and thus causing the deactivation of the mark after the command finishes. *Note The Mark::.  File: elisp, Node: Narrowing, Prev: Excursions, Up: Positions Narrowing ========= "Narrowing" means limiting the text addressable by Emacs editing commands to a limited range of characters in a buffer. The text that remains addressable is called the "accessible portion" of the buffer. Narrowing is specified with two buffer positions which become the beginning and end of the accessible portion. For most editing commands and most Emacs primitives, these positions replace the values of the beginning and end of the buffer. While narrowing is in effect, no text outside the accessible portion is displayed, and point cannot move outside the accessible portion. Values such as positions or line numbers, which usually count from the beginning of the buffer, do so despite narrowing, but the functions which use them refuse to operate on text that is inaccessible. The commands for saving buffers are unaffected by narrowing; they save the entire buffer regardless of any narrowing. - Command: narrow-to-region START END This function sets the accessible portion of the current buffer to start at START and end at END. Both arguments should be character positions. In an interactive call, START and END are set to the bounds of the current region (point and the mark, with the smallest first). - Command: narrow-to-page MOVE-COUNT This function sets the accessible portion of the current buffer to include just the current page. An optional first argument MOVE-COUNT non-`nil' means to move forward or backward by MOVE-COUNT pages and then narrow to one page. The variable `page-delimiter' specifies where pages start and end (*note Standard Regexps::.). In an interactive call, MOVE-COUNT is set to the numeric prefix argument. - Command: widen This function cancels any narrowing in the current buffer, so that the entire contents are accessible. This is called "widening". It is equivalent to the following expression: (narrow-to-region 1 (1+ (buffer-size))) - Special Form: save-restriction BODY... This special form saves the current bounds of the accessible portion, evaluates the BODY forms, and finally restores the saved bounds, thus restoring the same state of narrowing (or absence thereof) formerly in effect. The state of narrowing is restored even in the event of an abnormal exit via `throw' or error (*note Nonlocal Exits::.). Therefore, this construct is a clean way to narrow a buffer temporarily. The value returned by `save-restriction' is that returned by the last form in BODY, or `nil' if no body forms were given. *Caution:* it is easy to make a mistake when using the `save-restriction' construct. Read the entire description here before you try it. If BODY changes the current buffer, `save-restriction' still restores the restrictions on the original buffer (the buffer whose restrictions it saved from), but it does not restore the identity of the current buffer. `save-restriction' does *not* restore point and the mark; use `save-excursion' for that. If you use both `save-restriction' and `save-excursion' together, `save-excursion' should come first (on the outside). Otherwise, the old point value would be restored with temporary narrowing still in effect. If the old point value were outside the limits of the temporary narrowing, this would fail to restore it accurately. The `save-restriction' special form records the values of the beginning and end of the accessible portion as distances from the beginning and end of the buffer. In other words, it records the amount of inaccessible text before and after the accessible portion. This method yields correct results if BODY does further narrowing. However, `save-restriction' can become confused if the body widens and then makes changes outside the range of the saved narrowing. When this is what you want to do, `save-restriction' is not the right tool for the job. Here is what you must use instead: (let ((beg (point-min-marker)) (end (point-max-marker))) (unwind-protect (progn BODY) (save-excursion (set-buffer (marker-buffer beg)) (narrow-to-region beg end)))) Here is a simple example of correct use of `save-restriction': ---------- Buffer: foo ---------- This is the contents of foo This is the contents of foo This is the contents of foo-!- ---------- Buffer: foo ---------- (save-excursion (save-restriction (goto-char 1) (forward-line 2) (narrow-to-region 1 (point)) (goto-char (point-min)) (replace-string "foo" "bar"))) ---------- Buffer: foo ---------- This is the contents of bar This is the contents of bar This is the contents of foo-!- ---------- Buffer: foo ----------  File: elisp, Node: Markers, Next: Text, Prev: Positions, Up: Top Markers ******* A "marker" is a Lisp object used to specify a position in a buffer relative to the surrounding text. A marker changes its offset from the beginning of the buffer automatically whenever text is inserted or deleted, so that it stays with the two characters on either side of it. * Menu: * Overview of Markers:: The components of a marker, and how it relocates. * Predicates on Markers:: Testing whether an object is a marker. * Creating Markers:: Making empty markers or markers at certain places. * Information from Markers:: Finding the marker's buffer or character position. * Marker Insertion Types:: Two ways a marker can relocate when you insert where it points. * Moving Markers:: Moving the marker to a new buffer or position. * The Mark:: How "the mark" is implemented with a marker. * The Region:: How to access "the region".  File: elisp, Node: Overview of Markers, Next: Predicates on Markers, Up: Markers Overview of Markers =================== A marker specifies a buffer and a position in that buffer. The marker can be used to represent a position in the functions that require one, just as an integer could be used. *Note Positions::, for a complete description of positions. A marker has two attributes: the marker position, and the marker buffer. The marker position is an integer that is equivalent (at a given time) to the marker as a position in that buffer. But the marker's position value can change often during the life of the marker. Insertion and deletion of text in the buffer relocate the marker. The idea is that a marker positioned between two characters remains between those two characters despite insertion and deletion elsewhere in the buffer. Relocation changes the integer equivalent of the marker. Deleting text around a marker's position leaves the marker between the characters immediately before and after the deleted text. Inserting text at the position of a marker normally leaves the marker either in front of or after the new text, depending on the marker's "insertion type" (*note Marker Insertion Types::.)--unless the insertion is done with `insert-before-markers' (*note Insertion::.). Insertion and deletion in a buffer must check all the markers and relocate them if necessary. This slows processing in a buffer with a large number of markers. For this reason, it is a good idea to make a marker point nowhere if you are sure you don't need it any more. Unreferenced markers are garbage collected eventually, but until then will continue to use time if they do point somewhere. Because it is common to perform arithmetic operations on a marker position, most of the arithmetic operations (including `+' and `-') accept markers as arguments. In such cases, the marker stands for its current position. Here are examples of creating markers, setting markers, and moving point to markers: ;; Make a new marker that initially does not point anywhere: (setq m1 (make-marker)) => # ;; Set `m1' to point between the 99th and 100th characters ;; in the current buffer: (set-marker m1 100) => # ;; Now insert one character at the beginning of the buffer: (goto-char (point-min)) => 1 (insert "Q") => nil ;; `m1' is updated appropriately. m1 => # ;; Two markers that point to the same position ;; are not `eq', but they are `equal'. (setq m2 (copy-marker m1)) => # (eq m1 m2) => nil (equal m1 m2) => t ;; When you are finished using a marker, make it point nowhere. (set-marker m1 nil) => #  File: elisp, Node: Predicates on Markers, Next: Creating Markers, Prev: Overview of Markers, Up: Markers Predicates on Markers ===================== You can test an object to see whether it is a marker, or whether it is either an integer or a marker. The latter test is useful in connection with the arithmetic functions that work with both markers and integers. - Function: markerp OBJECT This function returns `t' if OBJECT is a marker, `nil' otherwise. Note that integers are not markers, even though many functions will accept either a marker or an integer. - Function: integer-or-marker-p OBJECT This function returns `t' if OBJECT is an integer or a marker, `nil' otherwise. - Function: number-or-marker-p OBJECT This function returns `t' if OBJECT is a number (either integer or floating point) or a marker, `nil' otherwise.  File: elisp, Node: Creating Markers, Next: Information from Markers, Prev: Predicates on Markers, Up: Markers Functions That Create Markers ============================= When you create a new marker, you can make it point nowhere, or point to the present position of point, or to the beginning or end of the accessible portion of the buffer, or to the same place as another given marker. - Function: make-marker This function returns a newly created marker that does not point anywhere. (make-marker) => # - Function: point-marker This function returns a new marker that points to the present position of point in the current buffer. *Note Point::. For an example, see `copy-marker', below. - Function: point-min-marker This function returns a new marker that points to the beginning of the accessible portion of the buffer. This will be the beginning of the buffer unless narrowing is in effect. *Note Narrowing::. - Function: point-max-marker This function returns a new marker that points to the end of the accessible portion of the buffer. This will be the end of the buffer unless narrowing is in effect. *Note Narrowing::. Here are examples of this function and `point-min-marker', shown in a buffer containing a version of the source file for the text of this chapter. (point-min-marker) => # (point-max-marker) => # (narrow-to-region 100 200) => nil (point-min-marker) => # (point-max-marker) => # - Function: copy-marker MARKER-OR-INTEGER INSERTION-TYPE If passed a marker as its argument, `copy-marker' returns a new marker that points to the same place and the same buffer as does MARKER-OR-INTEGER. If passed an integer as its argument, `copy-marker' returns a new marker that points to position MARKER-OR-INTEGER in the current buffer. The new marker's insertion type is specified by the argument INSERTION-TYPE. *Note Marker Insertion Types::. If passed an integer argument less than 1, `copy-marker' returns a new marker that points to the beginning of the current buffer. If passed an integer argument greater than the length of the buffer, `copy-marker' returns a new marker that points to the end of the buffer. (copy-marker 0) => # (copy-marker 20000) => # An error is signaled if MARKER is neither a marker nor an integer. Two distinct markers are considered `equal' (even though not `eq') to each other if they have the same position and buffer, or if they both point nowhere. (setq p (point-marker)) => # (setq q (copy-marker p)) => # (eq p q) => nil (equal p q) => t  File: elisp, Node: Information from Markers, Next: Marker Insertion Types, Prev: Creating Markers, Up: Markers Information from Markers ======================== This section describes the functions for accessing the components of a marker object. - Function: marker-position MARKER This function returns the position that MARKER points to, or `nil' if it points nowhere. - Function: marker-buffer MARKER This function returns the buffer that MARKER points into, or `nil' if it points nowhere. (setq m (make-marker)) => # (marker-position m) => nil (marker-buffer m) => nil (set-marker m 3770 (current-buffer)) => # (marker-buffer m) => # (marker-position m) => 3770  File: elisp, Node: Marker Insertion Types, Next: Moving Markers, Prev: Information from Markers, Up: Markers Marker Insertion Types ====================== When you insert text directly at the place where a marker points, there are two possible ways to relocate that marker: it can point before the inserted text, or point after it. You can specify which one a given marker should do by setting its "insertion type". Note that use of `insert-before-markers' ignores markers' insertion types, always relocating a marker to point after the inserted text. - Function: set-marker-insertion-type MARKER TYPE This function sets the insertion type of marker MARKER to TYPE. If TYPE is `t', MARKER will advance when text is inserted at its position. If TYPE is `nil', MARKER does not advance when text is inserted there. - Function: marker-insertion-type MARKER This function reports the current insertion type of MARKER.  File: elisp, Node: Moving Markers, Next: The Mark, Prev: Marker Insertion Types, Up: Markers Moving Marker Positions ======================= This section describes how to change the position of an existing marker. When you do this, be sure you know whether the marker is used outside of your program, and, if so, what effects will result from moving it--otherwise, confusing things may happen in other parts of Emacs. - Function: set-marker MARKER POSITION &optional BUFFER This function moves MARKER to POSITION in BUFFER. If BUFFER is not provided, it defaults to the current buffer. If POSITION is less than 1, `set-marker' moves MARKER to the beginning of the buffer. If POSITION is greater than the size of the buffer, `set-marker' moves marker to the end of the buffer. If POSITION is `nil' or a marker that points nowhere, then MARKER is set to point nowhere. The value returned is MARKER. (setq m (point-marker)) => # (set-marker m 55) => # (setq b (get-buffer "foo")) => # (set-marker m 0 b) => # - Function: move-marker MARKER POSITION &optional BUFFER This is another name for `set-marker'.  File: elisp, Node: The Mark, Next: The Region, Prev: Moving Markers, Up: Markers The Mark ======== One special marker in each buffer is designated "the mark". It records a position for the user for the sake of commands such as `kill-region' and `indent-rigidly'. Lisp programs should set the mark only to values that have a potential use to the user, and never for their own internal purposes. For example, the `replace-regexp' command sets the mark to the value of point before doing any replacements, because this enables the user to move back there conveniently after the replace is finished. Many commands are designed so that when called interactively they operate on the text between point and the mark. If you are writing such a command, don't examine the mark directly; instead, use `interactive' with the `r' specification. This provides the values of point and the mark as arguments to the command in an interactive call, but permits other Lisp programs to specify arguments explicitly. *Note Interactive Codes::. Each buffer has its own value of the mark that is independent of the value of the mark in other buffers. When a buffer is created, the mark exists but does not point anywhere. We consider this state as "the absence of a mark in that buffer." Once the mark "exists" in a buffer, it normally never ceases to exist. However, it may become "inactive", if Transient Mark mode is enabled. The variable `mark-active', which is always buffer-local in all buffers, indicates whether the mark is active: non-`nil' means yes. A command can request deactivation of the mark upon return to the editor command loop by setting `deactivate-mark' to a non-`nil' value (but this causes deactivation only if Transient Mark mode is enabled). The main motivation for using Transient Mark mode is that this mode also enables highlighting of the region when the mark is active. *Note Display::. In addition to the mark, each buffer has a "mark ring" which is a list of markers containing previous values of the mark. When editing commands change the mark, they should normally save the old value of the mark on the mark ring. The variable `mark-ring-max' specifies the maximum number of entries in the mark ring; once the list becomes this long, adding a new element deletes the last element. - Function: mark &optional FORCE This function returns the current buffer's mark position as an integer. If the mark is inactive, `mark' normally signals an error. However, if FORCE is non-`nil', then `mark' returns the mark position anyway--or `nil', if the mark is not yet set for this buffer. - Function: mark-marker This function returns the current buffer's mark. This is the very marker that records the mark location inside Emacs, not a copy. Therefore, changing this marker's position will directly affect the position of the mark. Don't do it unless that is the effect you want. (setq m (mark-marker)) => # (set-marker m 100) => # (mark-marker) => # Like any marker, this marker can be set to point at any buffer you like. We don't recommend that you make it point at any buffer other than the one of which it is the mark. If you do, it will yield perfectly consistent, but rather odd, results. - Function: set-mark POSITION This function sets the mark to POSITION, and activates the mark. The old value of the mark is *not* pushed onto the mark ring. *Please note:* Use this function only if you want the user to see that the mark has moved, and you want the previous mark position to be lost. Normally, when a new mark is set, the old one should go on the `mark-ring'. For this reason, most applications should use `push-mark' and `pop-mark', not `set-mark'. Novice Emacs Lisp programmers often try to use the mark for the wrong purposes. The mark saves a location for the user's convenience. An editing command should not alter the mark unless altering the mark is part of the user-level functionality of the command. (And, in that case, this effect should be documented.) To remember a location for internal use in the Lisp program, store it in a Lisp variable. For example: (let ((beg (point))) (forward-line 1) (delete-region beg (point))). - Function: push-mark &optional POSITION NOMSG ACTIVATE This function sets the current buffer's mark to POSITION, and pushes a copy of the previous mark onto `mark-ring'. If POSITION is `nil', then the value of point is used. `push-mark' returns `nil'. The function `push-mark' normally *does not* activate the mark. To do that, specify `t' for the argument ACTIVATE. A `Mark set' message is displayed unless NOMSG is non-`nil'. - Function: pop-mark This function pops off the top element of `mark-ring' and makes that mark become the buffer's actual mark. This does not move point in the buffer, and it does nothing if `mark-ring' is empty. It deactivates the mark. The return value is not meaningful. - User Option: transient-mark-mode This variable if non-`nil' enables Transient Mark mode, in which every buffer-modifying primitive sets `deactivate-mark'. The consequence of this is that commands that modify the buffer normally make the mark inactive. - User Option: mark-even-if-inactive If this is non-`nil', Lisp programs and the Emacs user can use the mark even when it is inactive. This option affects the behavior of Transient Mark mode. When the option is non-`nil', deactivation of the mark turns off region highlighting, but commands that use the mark behave as if the mark were still active. - Variable: deactivate-mark If an editor command sets this variable non-`nil', then the editor command loop deactivates the mark after the command returns (if Transient Mark mode is enabled). All the primitives that change the buffer set `deactivate-mark', to deactivate the mark when the command is finished. - Function: deactivate-mark This function deactivates the mark, if Transient Mark mode is enabled. Otherwise it does nothing. - Variable: mark-active The mark is active when this variable is non-`nil'. This variable is always buffer-local in each buffer. - Variable: activate-mark-hook - Variable: deactivate-mark-hook These normal hooks are run, respectively, when the mark becomes active and when it becomes inactive. The hook `activate-mark-hook' is also run at the end of a command if the mark is active and it is possible that the region may have changed. - Variable: mark-ring The value of this buffer-local variable is the list of saved former marks of the current buffer, most recent first. mark-ring => (# # ...) - User Option: mark-ring-max The value of this variable is the maximum size of `mark-ring'. If more marks than this are pushed onto the `mark-ring', `push-mark' discards an old mark when it adds a new one.  File: elisp, Node: The Region, Prev: The Mark, Up: Markers The Region ========== The text between point and the mark is known as "the region". Various functions operate on text delimited by point and the mark, but only those functions specifically related to the region itself are described here. - Function: region-beginning This function returns the position of the beginning of the region (as an integer). This is the position of either point or the mark, whichever is smaller. If the mark does not point anywhere, an error is signaled. - Function: region-end This function returns the position of the end of the region (as an integer). This is the position of either point or the mark, whichever is larger. If the mark does not point anywhere, an error is signaled. Few programs need to use the `region-beginning' and `region-end' functions. A command designed to operate on a region should normally use `interactive' with the `r' specification to find the beginning and end of the region. This lets other Lisp programs specify the bounds explicitly as arguments. (*Note Interactive Codes::.)  File: elisp, Node: Text, Next: Non-ASCII Characters, Prev: Markers, Up: Top Text **** This chapter describes the functions that deal with the text in a buffer. Most examine, insert, or delete text in the current buffer, often in the vicinity of point. Many are interactive. All the functions that change the text provide for undoing the changes (*note Undo::.). Many text-related functions operate on a region of text defined by two buffer positions passed in arguments named START and END. These arguments should be either markers (*note Markers::.) or numeric character positions (*note Positions::.). The order of these arguments does not matter; it is all right for START to be the end of the region and END the beginning. For example, `(delete-region 1 10)' and `(delete-region 10 1)' are equivalent. An `args-out-of-range' error is signaled if either START or END is outside the accessible portion of the buffer. In an interactive call, point and the mark are used for these arguments. Throughout this chapter, "text" refers to the characters in the buffer, together with their properties (when relevant). * Menu: * Near Point:: Examining text in the vicinity of point. * Buffer Contents:: Examining text in a general fashion. * Comparing Text:: Comparing substrings of buffers. * Insertion:: Adding new text to a buffer. * Commands for Insertion:: User-level commands to insert text. * Deletion:: Removing text from a buffer. * User-Level Deletion:: User-level commands to delete text. * The Kill Ring:: Where removed text sometimes is saved for later use. * Undo:: Undoing changes to the text of a buffer. * Maintaining Undo:: How to enable and disable undo information. How to control how much information is kept. * Filling:: Functions for explicit filling. * Margins:: How to specify margins for filling commands. * Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context. * Auto Filling:: How auto-fill mode is implemented to break lines. * Sorting:: Functions for sorting parts of the buffer. * Columns:: Computing horizontal positions, and using them. * Indentation:: Functions to insert or adjust indentation. * Case Changes:: Case conversion of parts of the buffer. * Text Properties:: Assigning Lisp property lists to text characters. * Substitution:: Replacing a given character wherever it appears. * Transposition:: Swapping two portions of a buffer. * Registers:: How registers are implemented. Accessing the text or position stored in a register. * Change Hooks:: Supplying functions to be run when text is changed.  File: elisp, Node: Near Point, Next: Buffer Contents, Up: Text Examining Text Near Point ========================= Many functions are provided to look at the characters around point. Several simple functions are described here. See also `looking-at' in *Note Regexp Search::. - Function: char-after &optional POSITION This function returns the character in the current buffer at (i.e., immediately after) position POSITION. If POSITION is out of range for this purpose, either before the beginning of the buffer, or at or beyond the end, then the value is `nil'. The default for POSITION is point. In the following example, assume that the first character in the buffer is `@': (char-to-string (char-after 1)) => "@" - Function: char-before &optional POSITION This function returns the character in the current buffer immediately before position POSITION. If POSITION is out of range for this purpose, either before the beginning of the buffer, or at or beyond the end, then the value is `nil'. The default for POSITION is point. - Function: following-char This function returns the character following point in the current buffer. This is similar to `(char-after (point))'. However, if point is at the end of the buffer, then `following-char' returns 0. Remember that point is always between characters, and the terminal cursor normally appears over the character following point. Therefore, the character returned by `following-char' is the character the cursor is over. In this example, point is between the `a' and the `c'. ---------- Buffer: foo ---------- Gentlemen may cry ``Pea-!-ce! Peace!,'' but there is no peace. ---------- Buffer: foo ---------- (char-to-string (preceding-char)) => "a" (char-to-string (following-char)) => "c" - Function: preceding-char This function returns the character preceding point in the current buffer. See above, under `following-char', for an example. If point is at the beginning of the buffer, `preceding-char' returns 0. - Function: bobp This function returns `t' if point is at the beginning of the buffer. If narrowing is in effect, this means the beginning of the accessible portion of the text. See also `point-min' in *Note Point::. - Function: eobp This function returns `t' if point is at the end of the buffer. If narrowing is in effect, this means the end of accessible portion of the text. See also `point-max' in *Note Point::. - Function: bolp This function returns `t' if point is at the beginning of a line. *Note Text Lines::. The beginning of the buffer (or of its accessible portion) always counts as the beginning of a line. - Function: eolp This function returns `t' if point is at the end of a line. The end of the buffer (or of its accessible portion) is always considered the end of a line.  File: elisp, Node: Buffer Contents, Next: Comparing Text, Prev: Near Point, Up: Text Examining Buffer Contents ========================= This section describes two functions that allow a Lisp program to convert any portion of the text in the buffer into a string. - Function: buffer-substring START END This function returns a string containing a copy of the text of the region defined by positions START and END in the current buffer. If the arguments are not positions in the accessible portion of the buffer, `buffer-substring' signals an `args-out-of-range' error. It is not necessary for START to be less than END; the arguments can be given in either order. But most often the smaller argument is written first. If the text being copied has any text properties, these are copied into the string along with the characters they belong to. *Note Text Properties::. However, overlays (*note Overlays::.) in the buffer and their properties are ignored, not copied. ---------- Buffer: foo ---------- This is the contents of buffer foo ---------- Buffer: foo ---------- (buffer-substring 1 10) => "This is t" (buffer-substring (point-max) 10) => "he contents of buffer foo " - Function: buffer-substring-no-properties START END This is like `buffer-substring', except that it does not copy text properties, just the characters themselves. *Note Text Properties::. - Function: buffer-string This function returns the contents of the entire accessible portion of the current buffer as a string. It is equivalent to (buffer-substring (point-min) (point-max)) ---------- Buffer: foo ---------- This is the contents of buffer foo ---------- Buffer: foo ---------- (buffer-string) => "This is the contents of buffer foo " - Function: thing-at-point THING Return the THING around or next to point, as a string. The argument THING is a symbol which specifies a kind of syntactic entity. Possibilities include `symbol', `list', `sexp', `defun', `filename', `url', `word', `sentence', `whitespace', `line', `page', and others. ---------- Buffer: foo ---------- Gentlemen may cry ``Pea-!-ce! Peace!,'' but there is no peace. ---------- Buffer: foo ---------- (thing-at-point 'word) => "Peace" (thing-at-point 'line) => "Gentlemen may cry ``Peace! Peace!,''\n" (thing-at-point 'whitespace) => nil  File: elisp, Node: Comparing Text, Next: Insertion, Prev: Buffer Contents, Up: Text Comparing Text ============== This function lets you compare portions of the text in a buffer, without copying them into strings first. - Function: compare-buffer-substrings BUFFER1 START1 END1 BUFFER2 START2 END2 This function lets you compare two substrings of the same buffer or two different buffers. The first three arguments specify one substring, giving a buffer and two positions within the buffer. The last three arguments specify the other substring in the same way. You can use `nil' for BUFFER1, BUFFER2, or both to stand for the current buffer. The value is negative if the first substring is less, positive if the first is greater, and zero if they are equal. The absolute value of the result is one plus the index of the first differing characters within the substrings. This function ignores case when comparing characters if `case-fold-search' is non-`nil'. It always ignores text properties. Suppose the current buffer contains the text `foobarbar haha!rara!'; then in this example the two substrings are `rbar ' and `rara!'. The value is 2 because the first substring is greater at the second character. (compare-buffer-substring nil 6 11 nil 16 21) => 2  File: elisp, Node: Insertion, Next: Commands for Insertion, Prev: Comparing Text, Up: Text Inserting Text ============== "Insertion" means adding new text to a buffer. The inserted text goes at point--between the character before point and the character after point. Some insertion functions leave point before the inserted text, while other functions leave it after. We call the former insertion "after point" and the latter insertion "before point". Insertion relocates markers that point at positions after the insertion point, so that they stay with the surrounding text (*note Markers::.). When a marker points at the place of insertion, insertion may or may not relocate the marker, depending on the marker's insertion type (*note Marker Insertion Types::.). Certain special functions such as `insert-before-markers' relocate all such markers to point after the inserted text, regardless of the markers' insertion type. Insertion functions signal an error if the current buffer is read-only. These functions copy text characters from strings and buffers along with their properties. The inserted characters have exactly the same properties as the characters they were copied from. By contrast, characters specified as separate arguments, not part of a string or buffer, inherit their text properties from the neighboring text. The insertion functions convert text from unibyte to multibyte in order to insert in a multibyte buffer, and vice versa--if the text comes from a string or from a buffer. However, they do not convert unibyte character codes 128 through 255 to multibyte characters, not even if the current buffer is a multibyte buffer. *Note Converting Representations::. - Function: insert &rest ARGS This function inserts the strings and/or characters ARGS into the current buffer, at point, moving point forward. In other words, it inserts the text before point. An error is signaled unless all ARGS are either strings or characters. The value is `nil'. - Function: insert-before-markers &rest ARGS This function inserts the strings and/or characters ARGS into the current buffer, at point, moving point forward. An error is signaled unless all ARGS are either strings or characters. The value is `nil'. This function is unlike the other insertion functions in that it relocates markers initially pointing at the insertion point, to point after the inserted text. If an overlay begins the insertion point, the inserted text falls outside the overlay; if a nonempty overlay ends at the insertion point, the inserted text falls inside that overlay. - Function: insert-char CHARACTER &optional COUNT INHERIT This function inserts COUNT instances of CHARACTER into the current buffer before point. The argument COUNT should be a number (`nil' means 1), and CHARACTER must be a character. The value is `nil'. This function does not convert unibyte character codes 128 through 255 to multibyte characters, not even if the current buffer is a multibyte buffer. *Note Converting Representations::. If INHERIT is non-`nil', then the inserted characters inherit sticky text properties from the two characters before and after the insertion point. *Note Sticky Properties::. - Function: insert-buffer-substring FROM-BUFFER-OR-NAME &optional START END This function inserts a portion of buffer FROM-BUFFER-OR-NAME (which must already exist) into the current buffer before point. The text inserted is the region from START and END. (These arguments default to the beginning and end of the accessible portion of that buffer.) This function returns `nil'. In this example, the form is executed with buffer `bar' as the current buffer. We assume that buffer `bar' is initially empty. ---------- Buffer: foo ---------- We hold these truths to be self-evident, that all ---------- Buffer: foo ---------- (insert-buffer-substring "foo" 1 20) => nil ---------- Buffer: bar ---------- We hold these truth-!- ---------- Buffer: bar ---------- *Note Sticky Properties::, for other insertion functions that inherit text properties from the nearby text in addition to inserting it. Whitespace inserted by indentation functions also inherits text properties.  File: elisp, Node: Commands for Insertion, Next: Deletion, Prev: Insertion, Up: Text User-Level Insertion Commands ============================= This section describes higher-level commands for inserting text, commands intended primarily for the user but useful also in Lisp programs. - Command: insert-buffer FROM-BUFFER-OR-NAME This command inserts the entire contents of FROM-BUFFER-OR-NAME (which must exist) into the current buffer after point. It leaves the mark after the inserted text. The value is `nil'. - Command: self-insert-command COUNT This command inserts the last character typed; it does so COUNT times, before point, and returns `nil'. Most printing characters are bound to this command. In routine use, `self-insert-command' is the most frequently called function in Emacs, but programs rarely use it except to install it on a keymap. In an interactive call, COUNT is the numeric prefix argument. This command calls `auto-fill-function' whenever that is non-`nil' and the character inserted is a space or a newline (*note Auto Filling::.). This command performs abbrev expansion if Abbrev mode is enabled and the inserted character does not have word-constituent syntax. (*Note Abbrevs::, and *Note Syntax Class Table::.) This is also responsible for calling `blink-paren-function' when the inserted character has close parenthesis syntax (*note Blinking::.). - Command: newline &optional NUMBER-OF-NEWLINES This command inserts newlines into the current buffer before point. If NUMBER-OF-NEWLINES is supplied, that many newline characters are inserted. This function calls `auto-fill-function' if the current column number is greater than the value of `fill-column' and NUMBER-OF-NEWLINES is `nil'. Typically what `auto-fill-function' does is insert a newline; thus, the overall result in this case is to insert two newlines at different places: one at point, and another earlier in the line. `newline' does not auto-fill if NUMBER-OF-NEWLINES is non-`nil'. This command indents to the left margin if that is not zero. *Note Margins::. The value returned is `nil'. In an interactive call, COUNT is the numeric prefix argument. - Command: split-line This command splits the current line, moving the portion of the line after point down vertically so that it is on the next line directly below where it was before. Whitespace is inserted as needed at the beginning of the lower line, using the `indent-to' function. `split-line' returns the position of point. Programs hardly ever use this function. - Variable: overwrite-mode This variable controls whether overwrite mode is in effect. The value should be `overwrite-mode-textual', `overwrite-mode-binary', or `nil'. `overwrite-mode-textual' specifies textual overwrite mode (treats newlines and tabs specially), and `overwrite-mode-binary' specifies binary overwrite mode (treats newlines and tabs like any other characters).