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 (see section 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 (see section Markers) or numeric
character positions (see section 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.
Many functions are provided to look at the characters around point.
Several simple functions are described here. See also looking-at
in section Regular Expression Searching.
nil.
In the following example, assume that the first character in the buffer is `@':
(char-to-string (char-after 1))
=> "@"
(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"
following-char, for an example. If
point is at the beginning of the buffer, preceding-char returns
0.
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
section Point.
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 See section Point.
t if point is at the beginning of a line.
See section Motion by Text Lines. The beginning of the buffer (or its accessible
portion always counts as the beginning of a line.
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.
This section describes two functions that allow a Lisp program to convert any portion of the text in the buffer into a string.
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.
---------- 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 "
(point-min) and (point-max) (see section Narrowing).
---------- Buffer: foo ----------
This is the contents of buffer foo
---------- Buffer: foo ----------
(buffer-string)
=> "This is the contents of buffer foo
"
This function lets you compare portions of the text in a buffer, without copying them into strings first.
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.
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
This function does not exist in Emacs version 18 and earlier.
Insertion means adding new text to a buffer. The inserted text goes at point--between the character before point and the character after point.
Insertion relocates markers that point at positions after the
insertion point, so that they stay with the surrounding text
(see section Markers). When a marker points at the place of insertion,
insertion normally doesn't relocate the marker, so that it points to the
beginning of the inserted text; however, certain special functions such
as insert-before-markers relocate such markers to point after the
inserted text.
Some insertion functions leave point before the inserted text, while other functions leave it after. We call the latter insertion before point.
Insertion functions signal an error if the current buffer is read-only.
nil.
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.
nil.
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 ----------
See section Stickiness of Text Properties, for other insertion functions that inherit text properties from the nearby text.
This section describes higher-level commands for inserting text, commands intended primarily for the user but useful also in Lisp programs.
nil.
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 function calls auto-fill-function if the current column number
is greater than the value of fill-column and the character
inserted is a space (see section Auto Filling).
This function performs abbrev expansion if Abbrev mode is enabled and the inserted character does not have word-constituent syntax. (See section Abbrevs And Abbrev Expansion, and section Table of Syntax Classes.)
This function is also responsible for calling
blink-paren-function when the inserted character has close
parenthesis syntax (see section Blinking Parentheses).
In Auto Fill mode, newline can break the preceding line if
number-of-newlines is not supplied. When this happens, it
actually inserts 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.
The value returned is nil. In an interactive call, count
is the numeric prefix argument.
indent-to function.
split-line returns the position of point.
Programs hardly ever use this function.
nil value enables the mode. It is automatically made
buffer-local when set in any fashion.
Deletion means removing part of the text in a buffer, without saving it in the kill ring (see section The Kill Ring). Deleted text can't be yanked, but can be reinserted using the undo mechanism (see section Undo). Some deletion functions save text in the kill ring in some cases but not in the usual case.
All of the deletion functions operate on the current buffer, and all
return a value of nil.
buffer-read-only
error. Otherwise, it deletes the text without asking for any
confirmation. It returns nil.
Normally, deleting a large amount of text from a buffer inhibits further
auto-saving of that buffer "because it has shrunk". However,
erase-buffer does not do this, the idea being that the future
text is not really related to the former text, and its size should not
be compared with that of the former text.
nil.
nil, then it saves the deleted characters in the kill ring.
In an interactive call, count is the numeric prefix argument, and killp is the unprocessed prefix argument. Therefore, if a prefix argument is supplied, the text is saved in the kill ring. If no prefix argument is supplied, then one character is deleted, but not saved in the kill ring.
The value returned is always nil.
nil, then it saves the deleted characters in the kill ring.
In an interactive call, count is the numeric prefix argument, and killp is the unprocessed prefix argument. Therefore, if a prefix argument is supplied, the text is saved in the kill ring. If no prefix argument is supplied, then one character is deleted, but not saved in the kill ring.
The value returned is always nil.
nil, then the command saves the deleted
characters in the kill ring.
Conversion of tabs to spaces happens only if count is positive. If it is negative, exactly -count characters after point are deleted.
In an interactive call, count is the numeric prefix argument, and killp is the unprocessed prefix argument. Therefore, if a prefix argument is supplied, the text is saved in the kill ring. If no prefix argument is supplied, then one character is deleted, but not saved in the kill ring.
The value returned is always nil.
This section describes higher-level commands for deleting text, commands intended primarily for the user but useful also in Lisp programs.
nil.
In the following examples, we call delete-horizontal-space four
times, once on each line, with point between the second and third
characters on the successive line.
---------- Buffer: foo ----------
I -!-thought
I -!- thought
We-!- thought
Yo-!-u thought
---------- Buffer: foo ----------
(delete-horizontal-space) ; Four times.
=> nil
---------- Buffer: foo ----------
Ithought
Ithought
Wethought
You thought
---------- Buffer: foo ----------
nil,
delete-indentation joins this line to the following line
instead. The value is nil.
If there is a fill prefix, and the second of the lines being joined
starts with the prefix, then delete-indentation deletes the
fill prefix before joining the lines.
In the example below, point is located on the line starting `events', and it makes no difference if there are trailing spaces in the preceding line.
---------- Buffer: foo ----------
When in the course of human
-!- events, it becomes necessary
---------- Buffer: foo ----------
(delete-indentation)
=> nil
---------- Buffer: foo ----------
When in the course of human-!- events, it becomes necessary
---------- Buffer: foo ----------
After the lines are joined, the function fixup-whitespace is
responsible for deciding whether to leave a space at the junction.
nil.
At the beginning or end of a line, the appropriate amount of space is none. Before a character with close parenthesis syntax, or after a character with open parenthesis or expression-prefix syntax, no space is also appropriate. Otherwise, one space is appropriate. See section Table of Syntax Classes.
In the example below, fixup-whitespace is called the first time
with point before the word `spaces' in the first line. for the
second invocation, Point is directly after the `('.
---------- Buffer: foo ----------
This has too many -!-spaces
This has too many spaces at the start of (-!- this list)
---------- Buffer: foo ----------
(fixup-whitespace)
=> nil
(fixup-whitespace)
=> nil
---------- Buffer: foo ----------
This has too many spaces
This has too many spaces at the start of (this list)
---------- Buffer: foo ----------
nil.
A blank line is defined as a line containing only tabs and spaces.
delete-blank-lines returns nil.
Kill functions delete text like the deletion functions, but save it so that the user can reinsert it by yanking. Most of these functions have `kill-' in their name. By contrast, the functions whose names start with `delete-' normally do not save text for yanking (though they can still be undone); these are "deletion" functions.
Most of the kill commands are primarily for interactive use, and are not described here. What we do describe are the functions provided for use in writing such commands. You can use these functions to write commands for killing text. When you need to deleting text for internal purposes within a Lisp function, you should normally use deletion functions, so as not to disturb the kill ring contents. See section Deletion of Text.
Killed text is saved for later yanking in the kill ring. This
is a list which holds, not just the last text kill, but a number of
recent kills. We call this a "ring" because yanking treats it as a
cyclic order. The list is kept in the variable kill-ring, and
can be operated on with the usual functions for lists; there are also
specialized functions, described in this section, which treat it as a
ring.
Some people think this use of the word "kill" is unfortunate, since it refers to operations which specifically do not destroy the entities "killed". This is in sharp contrast to ordinary life, in which death is permanent and "killed" entities do not come back to life. Therefore, other metaphors have been proposed. For example, the term "cut ring" makes sense to people who, in pre-computer days, used scissors and paste to cut up and rearrange manuscripts. However, it would be difficult to change the terminology now.
The kill ring records killed text as strings in a list, most recent first. A short kill ring, for example, might look like this:
("some text" "a different piece of text" "even older text")
When the list reaches kill-ring-max entries in length, adding a
new entry automatically deletes the last entry.
When kill commands are interwoven with other commands, each kill command makes a new entry in the kill ring. Multiple kill commands in succession build up a single entry in the kill ring, which would be yanked as a unit. The second and subsequent consecutive kill commands add text to the entry made by the first one.
For yanking, one entry in the kill ring is designated the "front" of the ring. Some yank commands "rotate" the ring by designating a different element as the "front." But this virtual rotation doesn't change the list itself--the most recent entry always comes first in the list.
kill-region is the usual subroutine for killing text. Any
command that calls this function is a "kill command" (and should
probably have `kill' in its name). kill-region puts the
newly killed text in a new element at the beginning of the kill ring or
adds it to the most recent element. It uses the last-command
variable to determine whether the previous was a kill command, and if so
appends the killed text to the most recent entry.
nil.
In an interactive call, start and end are point and the mark.
If the buffer is read-only, kill-region modifies the kill ring
just the same, then signals an error without modifying the buffer. This
is convenient because it lets the user use all the kill commands to copy
text into the kill ring from a read-only buffer.
nil. It also indicates the extent of the text copied by moving
the cursor momentarily, or by displaying a message in the echo area.
Don't call copy-region-as-kill in Lisp programs unless you aim to
support Emacs 18. For Emacs 19, it is better to use kill-new or
kill-append instead. See section Low Level Kill Ring.
Yanking means reinserting an entry of previously killed text from the kill ring.
If arg is a list (which occurs interactively when the user
types C-u with no digits), then yank inserts the text as
described above, but puts point before the yanked text and puts the mark
after it.
If arg is a number, then yank inserts the argth most
recently killed text--the argth element of the kill ring list.
yank does not alter the contents of the kill ring or rotate it.
It returns nil.
This is allowed only immediately after a yank or another
yank-pop. At such a time, the region contains text that was just
inserted by yanking. yank-pop deletes that text and inserts in
its place a different piece of killed text. It does not add the deleted
text to the kill ring, since it is already in the kill ring somewhere.
If arg is nil, then the replacement text is the previous
element of the kill ring. If arg is numeric, the replacement is
the argth previous kill. If arg is negative, a more recent
kill is the replacement.
The sequence of kills in the kill ring wraps around, so that after the oldest one comes the newest one, and before the newest one goes the oldest.
The value is always nil.
These functions and variables provide access to the kill ring at a lower level, but still convenient for use in Lisp programs. They take care of interaction with X Window selections. They do not exist in Emacs version 18.
current-kill rotates the yanking pointer in the
kill ring by n places, and returns the text at that place in the
ring.
If the optional second argument do-not-move is non-nil,
then current-kill doesn't alter the yanking pointer; it just
returns the nth kill forward from the current yanking pointer.
If n is zero, indicating a request for the latest kill,
current-kill calls the value of
interprogram-paste-function (documented below) before consulting
the kill ring.
interprogram-cut-function (see below).
nil, it goes at the beginning. This
function also invokes the value of interprogram-cut-function (see
below).
nil or a function of no arguments.
If the value is a function, current-kill calls it to get the
"most recent kill". If the function returns a non-nil value,
then that value is used as the "most recent kill". If it returns
nil, then the first element of kill-ring is used.
The normal use of this hook is to get the X server's primary selection as the most recent kill, even if the selection belongs to another X client. See section X Selections.
nil or a function of one argument.
If the value is a function, kill-new and kill-append call
it with the new first element of the kill ring as an argument.
The normal use of this hook is to set the X server's primary selection to the newly killed text.
The variable kill-ring holds the kill ring contents, in the
form of a list of strings. The most recent kill is always at the front
of the list.
The kill-ring-yank-pointer variable points to a link in the
kill ring list, whose CAR is the text to yank next. Moving
kill-ring-yank-pointer to a different link is called
rotating the kill ring; we say it identifies the "front" of the
ring. We call the kill ring a "ring" because the functions that move
the yank pointer wrap around from the end of the list to the beginning,
or vice-versa. Rotation of the kill ring is virtual; it does not change
the value of kill-ring.
Both kill-ring and kill-ring-yank-pointer are Lisp
variables whose values are normally lists. The word "pointer" in the
name of the kill-ring-yank-pointer indicates that the variable's
purpose is to identify one element of the list for use by the next yank
command.
The value of kill-ring-yank-pointer is always eq to one
of the links in the kill ring list. The element it identifies is the
CAR of that link. Kill commands, which change the kill ring, also
set this variable from kill-ring. The effect is to rotate the
ring so that the newly killed text is at front.
Here is a diagram that shows the variable kill-ring-yank-pointer
pointing to the second entry in the kill ring ("some text" "a
different piece of text" "yet older text").
kill-ring kill-ring-yank-pointer
| |
| ___ ___ ---> ___ ___ ___ ___
--> |___|___|------> |___|___|--> |___|___|--> nil
| | |
| | |
| | -->"yet older text"
| |
| --> "a different piece of text"
|
--> "some text"
This state of affairs might occur after C-y (yank)
immediately followed by M-y (yank-pop).
kill-ring, and its CAR is the kill string
that C-y should yank.
kill-ring-max is 30.
Most buffers have an undo list which records all changes made to
the buffer's text so that they can be undone. (The buffers which don't
have one are usually special-purpose buffers for which Emacs assumes
that undoing is not useful.) All the primitives which modify the text
in the buffer automatically add elements to the front of the undo list,
which is in the variable buffer-undo-list.
t disables the recording of undo information.
Here are the kinds of elements an undo list can have:
integer
(beg . end)
(pos . deleted)
(t high . low)
primitive-undo uses those
values to determine whether to mark the buffer as unmodified once again;
it does so only if the file's modification time matches those numbers.
(nil property value beg . end)
(put-text-property beg end property value)
nil
nil.
The editor command loop automatically creates an undo boundary between
keystroke commands. Thus, each undo normally undoes the effects of one
command. Calling this function explicitly is useful for splitting the
effects of a command into more than one unit. For example,
query-replace calls this function after each replacement so that
the user can undo individual replacements one by one.
primitive-undo adds elements to the buffer's undo list when it
changes the buffer. Undo commands avoid confusion by saving the undo
list value at the beginning of a sequence of undo operations. Then the
undo operations use and update the saved value. The new elements added
by undoing are not part of the saved value, so they don't interfere with
continuing to undo.
This section describes how to enable and disable undo information for a given buffer. It also explains how the undo list is truncated automatically so it doesn't get too big.
Recording of undo information in a newly created buffer is normally
enabled to start with; but if the buffer name starts with a space, the
undo recording is initially disabled. You can explicitly enable or
disable undo recording with the following two functions, or by setting
buffer-undo-list yourself.
nil.
In an interactive call, buffer-or-name is the current buffer. You cannot specify any other buffer.
This function returns nil. It cannot be called interactively.
The name buffer-flush-undo is not considered obsolete, but the
preferred name buffer-disable-undo is new as of Emacs versions
19.
As editing continues, undo lists get longer and longer. To prevent
them from using up all available memory space, garbage collection trims
them back to size limits you can set. (For this purpose, the "size"
of an undo list measures the cons cells that make up the list, plus the
strings of deleted text.) Two variables control the range of acceptable
sizes: undo-limit and undo-strong-limit.
Filling means adjusting the lengths of lines (by moving the line
breaks) so that they are nearly (but no greater than) a specified
maximum width. Additionally, lines can be justified, which means
that spaces are inserted between words to make the line exactly the
specified width. The width is controlled by the variable
fill-column. For ease of reading, lines should be no longer than
70 or so columns.
You can use Auto Fill mode (see section Auto Filling) to fill text automatically as you insert it, but changes to existing text may leave it improperly filled. Then you must fill the text explicitly.
Most of the functions in this section return values that are not meaningful.
nil, each line is justified as well.
It uses the ordinary paragraph motion commands to find paragraph
boundaries. See section `Paragraphs' in The Emacs Manual.
nil.
The variable paragraph-separate controls how to distinguish
paragraphs. See section Standard Regular Expressions Used in Editing.
The first two arguments, start and end, are the beginning
and end of the region to be filled. The third and fourth arguments,
justify-flag and mail-flag, are optional. If
justify-flag is non-nil, the paragraphs are justified as
well as filled. If mail-flag is non-nil, it means the
function is operating on a mail message and therefore should not fill
the header lines.
Ordinarily, fill-individual-paragraphs regards each change in
indentation as starting a new paragraph. If
fill-individual-varying-indent is non-nil, then only
separator lines separate paragraphs. That mode can handle paragraphs
with extra indentation on the first line.
fill-individual-paragraphs as
described above.
nil. In an interactive call, any
prefix argument requests justification.
In Adaptive Fill mode, which is enabled by default,
fill-region-as-paragraph on an indented paragraph when there is
no fill prefix uses the indentation of the second line of the paragraph
as the fill prefix.
fill-column. It returns
nil.
As a practical matter, if you are writing text for other people to
read, you should set fill-column to no more than 70. Otherwise
the line will be too long for people to read comfortably, and this can
make the text seem clumsy.
fill-column in
buffers that do not override it. This is the same as
(default-value 'fill-column).
The default value for default-fill-column is 70.
Auto Fill mode is a minor mode which fills lines automatically as text as inserted. This section describes the hook and the two variables used by Auto Fill mode. For a description of functions that you can call explicitly to fill and justify existing text, see section Filling.
fill-column. It may be nil, in which case nothing
special is done.
The value of auto-fill-function is do-auto-fill when
Auto-Fill mode is enabled. That is a function whose sole purpose is to
implement the usual strategy for breaking a line.
In older Emacs versions, this variable was named
auto-fill-hook, but since it is not called with the standard convention for hooks, it was renamed toauto-fill-functionin version 19.
The sorting functions described in this section all rearrange text in
a buffer. This is in contrast to the function sort, which
rearranges the order of the elements of a list (see section Functions that Rearrange Lists).
The values returned by these functions are not meaningful.
To understand how sort-subr works, consider the whole accessible
portion of the buffer as being divided into disjoint pieces called
sort records. The records may or may not be contiguous; they may
not overlap. A portion of each sort record (perhaps all of it) is
designated as the sort key. Sorting rearranges the records in order by
their sort keys.
Usually, the records are rearranged in order of ascending sort key.
If the first argument to the sort-subr function, reverse,
is non-nil, the sort records are rearranged in order of
descending sort key.
The next four arguments to sort-subr are functions that are
called to move point across a sort record. They are called many times
from within sort-subr.
sort-subr is
called. Therefore, you should usually move point to the beginning of
the buffer before calling sort-subr.
This function can indicate there are no more sort records by leaving
point at the end of the buffer.
nil value to be used as the sort key, or
return nil to indicate that the sort key is in the buffer
starting at point. In the latter case, endkeyfun is called to
find the end of the sort key.
nil and this argument is omitted (or
nil), then the sort key extends to the end of the record. There
is no need for endkeyfun if startkeyfun returns a
non-nil value.
As an example of sort-subr, here is the complete function
definition for sort-lines:
;; Note that the first two lines of doc string
;; are effectively one line when viewed by a user.
(defun sort-lines (reverse beg end)
"Sort lines in region alphabetically.
Called from a program, there are three arguments:
REVERSE (non-nil means reverse order),
and BEG and END (the region to sort)."
(interactive "P\nr")
(save-restriction
(narrow-to-region beg end)
(goto-char (point-min))
(sort-subr reverse
'forward-line
'end-of-line)))
Here forward-line moves point to the start of the next record,
and end-of-line moves point to the end of record. We do not pass
the arguments startkeyfun and endkeyfun, because the entire
record is used as the sort key.
The sort-paragraphs function is very much the same, except that
its sort-subr call looks like this:
(sort-subr reverse
(function
(lambda ()
(skip-chars-forward "\n \t\f")))
'forward-paragraph)
Alphabetical sorting means that two sort keys are compared by comparing the first characters of each, the second characters of each, and so on. If a mismatch is found, it means that the sort keys are unequal; the sort key whose character is less at the point of first mismatch is the lesser sort key. The individual characters are compared according to their numerical values. Since Emacs uses the ASCII character set, the ordering in that set determines alphabetical order.
The value of the record-regexp argument specifies how to divide the buffer into sort records. At the end of each record, a search is done for this regular expression, and the text that matches it is the next record. For example, the regular expression `^.+$', which matches lines with at least one character besides a newline, would make each such line into a sort record. See section Regular Expressions, for a description of the syntax and meaning of regular expressions.
The value of the key-regexp argument specifies what part of each record is the sort key. The key-regexp could match the whole record, or only a part. In the latter case, the rest of the record has no effect on the sorted order of records, but it is carried along when the record moves to its new position.
The key-regexp argument can refer to the text matched by a subexpression of record-regexp, or it can be a regular expression on its own.
If key-regexp is:
sort-regexp-fields searches for a match for the regular
expression within the record. If such a match is found, it is the sort
key. If there is no match for key-regexp within a record then
that record is ignored, which means its position in the buffer is not
changed. (The other records may move around it.)
For example, if you plan to sort all the lines in the region by the first word on each line starting with the letter `f', you should set record-regexp to `^.*$' and set key-regexp to `\<f\w*\>'. The resulting expression looks like this:
(sort-regexp-fields nil "^.*$" "\\<f\\w*\\>"
(region-beginning)
(region-end))
If you call sort-regexp-fields interactively, it prompts for
record-regexp and key-regexp in the minibuffer.
nil, the sort
is in reverse order.
nil, the sort
is in reverse order.
nil, the sort
is in reverse order.
If reverse is non-nil, the sort is in reverse order.
One unusual thing about this command is that the entire line containing position beg, and the entire line containing position end, are included in the region sorted.
Note that sort-columns uses the sort utility program,
and so cannot work properly on text containing tab characters. Use
M-x untabify to convert tabs to spaces before sorting.
The sort-columns function did not work on VMS prior to Emacs 19.
The column functions convert between a character position (counting characters from the beginning of the buffer) and a column position (counting screen characters from the beginning of a line).
A character counts according to the number of columns it occupies on
the screen. This means control characters count as occupying 2 or 4
columns, depending upon the value of ctl-arrow, and tabs count as
occupying a number of columns that depends on the value of
tab-width and on the column where the tab begins. See section Usual Display Conventions.
Column number computations ignore the width of the window and the amount of horizontal scrolling. Consequently, a column value can be arbitrarily high. The first (or leftmost) column is numbered 0.
For an example of using current-column, see the description of
count-lines in section Motion by Text Lines.
If column column is beyond the end of the line, point moves to the end of the line. If column is negative, point moves to the beginning of the line.
If it is impossible to move to column column because that is in
the middle of a multicolumn character such as a tab, point moves to the
end of that character. However, if force is non-nil, and
column is in the middle of a tab, then move-to-column
converts the tab into spaces so that it can move precisely to column
column. Other multicolumn characters can cause anomalies despite
force, since there is no way to split them.
The argument force also has an effect if the line isn't long enough to reach column column; in that case, it says to indent at the end of the line to reach that column.
If column is not an integer, an error is signaled.
The return value is the column number actually moved to.
The indentation functions are used to examine, move to, and change whitespace that is at the beginning of a line. Some of the functions can also change whitespace elsewhere on a line. Columns and indentation count from zero at the left margin.
This section describes the primitive functions used to count and insert indentation. The functions in the following sections use these primitives.
nil, then at least that many spaces are inserted even if this
requires going beyond column. The value is the column at which
the inserted indentation ends.
nil, indentation functions can insert
tabs as well as spaces. Otherwise, they insert only spaces. Setting
this variable automatically makes it local to the current buffer.
An important function of each major mode is to customize the TAB key to indent properly for the language being edited. This section describes the mechanism of the TAB key and how to control it. The functions in this section return unpredictable values.
indent-according-to-mode does no more than call this function.
In Lisp mode, the value is the symbol lisp-indent-line; in C
mode, c-indent-line; in Fortran mode, fortran-indent-line.
In Fundamental mode, Text mode, and many other modes with no standard
for indentation, the value is indent-to-left-margin (which is the
default value).
indent-line-function to
indent the current line in a way appropriate for the current major mode.
indent-line-function to indent
the current line; except that if that function is
indent-to-left-margin, it calls insert-tab instead. (That
is a trivial command which inserts a tab character.)
indent-line-function will indent. (That function is
indent-to-left-margin.) In Fundamental mode, LFD indents
to this column. This variable automatically becomes buffer-local when
set in any fashion.
indent-line-function, used in Fundamental
mode, Text mode, etc. Its effect is to adjust the indentation at the
beginning of the current line to the value specified by the variable
left-margin. This may involve either inserting or deleting
whitespace.
It does indentation by calling the current indent-line-function.
In programming language modes, this is the same thing TAB does,
but in some text modes, where TAB inserts a tab,
newline-and-indent indents to the column specified by
left-margin.
This command does indentation on both lines according to the current
major mode, by calling the current value of indent-line-function.
In programming language modes, this is the same thing TAB does,
but in some text modes, where TAB inserts a tab,
reindent-then-newline-and-indent indents to the column specified
by left-margin.
This section describes commands which indent all the lines in the region. They return unpredictable values.
nil, indent-region indents each nonblank line by calling
the current mode's indentation function, the value of
indent-line-function.
If to-column is non-nil, it should be an integer
specifying the number of columns of indentation; then this function
gives each line exactly that much indentation, by either adding or
deleting whitespace.
If there is a fill prefix, indent-region indents each line
by making it start with the fill prefix.
indent-region as a short cut. You should design the function so
that it will produce the same results as indenting the lines of the
region one by one, but presumably faster.
If the value is nil, there is no short cut, and
indent-region actually works line by line.
A short cut function is useful in modes such as C mode and Lisp mode,
where the indent-line-function must scan from the beginning of
the function: applying it to each line would be quadratic in time. The
short cut can update the scan information as it moves through the lines
indenting them; this takes linear time. In a mode where indenting a
line individually is fast, there is no need for a short cut.
indent-region with a non-nil argument has a different
meaning and does not use this variable.
For example, if count is 3, this command adds 3 columns of indentation to each of the lines beginning in the region specified.
In Mail mode, C-c C-y (mail-yank-original) uses
indent-rigidly to indent the text copied from the message being
replied to.
indent-rigidly, except that it doesn't alter lines
that start within strings or comments.
In addition, it doesn't alter a line if nochange-regexp matches at
the beginning of the line (if nochange-regexp is non-nil).
This section describes two commands which indent the current line based on the contents of previous lines.
If the previous nonblank line has no next indent point (i.e., none at a
great enough column position), indent-relative either does
nothing (if unindented-ok is non-nil) or calls
tab-to-tab-stop. Thus, if point is underneath and to the right
of the last column of a short line of text, this command ordinarily
moves point to the next tab stop by inserting whitespace.
The return value of indent-relative is unpredictable.
In the following example, point is at the beginning of the second line:
This line is indented twelve spaces.
-!-The quick brown fox jumped.
Evaluation of the expression (indent-relative nil) produces the
following:
This line is indented twelve spaces.
-!-The quick brown fox jumped.
In this example, point is between the `m' and `p' of `jumped':
This line is indented twelve spaces.
The quick brown fox jum-!-ped.
Evaluation of the expression (indent-relative nil) produces the
following:
This line is indented twelve spaces.
The quick brown fox jum -!-ped.
indent-relative with t as the unindented-ok
argument. The return value is unpredictable.
If the previous nonblank line has no indent points beyond the current column, this command does nothing.
This section explains the mechanism for user-specified "tab stops" and the mechanisms which use and set them. The name "tab stops" is used because the feature is similar to that of the tab stops on a typewriter. The feature works by inserting an appropriate number of spaces and tab characters to reach the next tab stop column; it does not affect the display of tab characters in the buffer (see section Usual Display Conventions). Note that the TAB character as input uses this tab stop feature only in a few major modes, such as Text mode.
tab-stop-list. It searches the list for an element
greater than the current column number, and uses that element as the
column to indent to. It does nothing if no such element is found.
tab-to-tab-stops. The elements should be integers in increasing
order. The tab stop columns need not be evenly spaced.
Use M-x edit-tab-stops to edit the location of tab stops interactively.
These commands, primarily for interactive use, act based on the indentation in the text.
nil.
nil.
nil.
The case change commands described here work on text in the current buffer. See section Character Case, for case conversion commands that work on strings and characters. See section The Case Table, for how to customize which characters are upper or lower case and how to convert them.
nil.
If one end of the region is in the middle of a word, the part of the word within the region is treated as an entire word.
When capitalize-region is called interactively, start and
end are point and the mark, with the smallest first.
---------- Buffer: foo ---------- This is the contents of the 5th foo. ---------- Buffer: foo ---------- (capitalize-region 1 44) => nil ---------- Buffer: foo ---------- This Is The Contents Of The 5th Foo. ---------- Buffer: foo ----------
nil.
When downcase-region is called interactively, start and
end are point and the mark, with the smallest first.
nil.
When upcase-region is called interactively, start and
end are point and the mark, with the smallest first.
nil.
If point is in the middle of a word, the part of word the before point (if moving forward) or after point (if operating backward) is ignored. The rest is treated as an entire word.
When capitalize-word is called interactively, count is
set to the numeric prefix argument.
nil.
When downcase-word is called interactively, count is set
to the numeric prefix argument.
nil.
When upcase-word is called interactively, count is set to
the numeric prefix argument.
Each character position in a buffer or a string can have a text property list, much like the property list of a symbol (see section Property Lists). The properties belong to a particular character at a particular place, such as, the letter `T' at the beginning of this sentence or the first `o' in `foo'---if the same character occurs in two different places, the two occurrences generally have different properties.
Each property has a name and a value. Both of these can be any Lisp object, but the name is normally a symbol. The usual way to access the property list is to specify a name and ask what value corresponds to it.
If a character has a category property, we call it the
category of the character. It should be a symbol. The properties
of the symbol serve as defaults for the properties of the character.
Copying text between strings and buffers preserves the properties
along with the characters; this includes such diverse functions as
substring, insert, and buffer-substring.
The simplest way to examine text properties is to ask for the value of
a particular property of a particular character. For that, use
get-text-property. Use text-properties-at to get the
entire property list of a character. See section Property Search Functions, for
functions to examine the properties of a number of characters at once.
These functions handle both strings and buffers. Keep in mind that positions in a string start from 0, whereas positions in a buffer start from 1.
If there is no prop property strictly speaking, but the character
has a category which is a symbol, then get-text-property returns
the prop property of that symbol.
get-text-property, except that it checks
overlays first and then text properties. See section Overlays.
The argument object may be a string, a buffer, or a window. If it is a window, then the buffer displayed in that window is used for text properties and overlays, but only the overlays active for that window are considered. If object is a buffer, then all overlays in that buffer are considered, as well as text properties. If object is a string, only text properties are considered, since strings never have overlays.
nil, it defaults to the current buffer.
The primitives for changing properties apply to a specified range of
text. The function set-text-properties (see end of section) sets
the entire property list of the text in that range; more often, it is
useful to add, change, or delete just certain properties specified by
name.
Since text properties are considered part of the buffer's contents, and can affect how the buffer looks on the screen, any change in the text properties is considered a buffer modification. Buffer text property changes are undoable (see section Undo).
nil, it defaults to the current buffer.
The argument props specifies which properties to change. It should have the form of a property list (see section Property Lists): a list whose elements include the property names followed alternately by the corresponding values.
The return value is t if the function actually changed some
property's value; nil otherwise (if props is nil or
its values agree with those in the text).
For example, here is how to set the comment and face
properties of a range of text:
(add-text-properties start end
'(comment t face highlight))
nil, it defaults to the current buffer.
nil, it defaults to the current buffer.
The argument props specifies which properties to delete. It
should have the form of a property list (see section Property Lists): a list
whose elements are property names alternating with corresponding values.
But only the names matter--the values that accompany them are ignored.
For example, here's how to remove the face property.
(remove-text-properties start end '(face nil))
The return value is t if the function actually changed some
property's value; nil otherwise (if props is nil or
if no character in the specified text had any of those properties).
nil, it defaults to the current buffer.
The argument props is the new property list. It should be a list whose elements are property names alternating with corresponding values.
After set-text-properties returns, all the characters in the
specified range have identical properties.
If props is nil, the effect is to get rid of all properties
from the specified range of text. Here's an example:
(set-text-properties start end nil)
In typical use of text properties, most of the time several or many consecutive characters have the same value for a property. Rather than writing your programs to examine characters one by one, it is much faster to process chunks of text that have the same property value.
Here are functions you can use to do this. In all cases, object defaults to the current buffer.
For high performance, it's very important to use the limit argument to these functions, especially the ones that search for a single property--otherwise, they may spend a long time considering changes in other properties while scanning to the end of the buffer.
If limit is non-nil, then the scan ends at position
limit. If there is no property change before that point,
next-property-change returns limit.
The value is nil if the properties remain unchanged all the way
to the end of object and limit is nil.
If the value is non-nil, it is a position greater than or equal
to pos. The value equals pos only when limit equals
pos.
Here is an example of how to scan the buffer by chunks of text within which all properties are constant:
(while (not (eobp))
(let ((plist (text-properties-at (point)))
(next-change
(or (next-property-change (point) (current-buffer))
(point-max))))
Process text from point to next-change...
(goto-char next-change)))
If limit is non-nil, then the scan ends at position
limit. If there is no property change before that point,
next-single-property-change returns limit.
The value is nil if the property remains unchanged all the way to
the end of object and limit is nil. If the value is
non-nil, it is a position greater than or equal to pos; it
equals pos only if limit equals pos.
next-property-change, but scans back from pos
instead of forward. If the value is non-nil, it is a position
less than or equal to pos; it equals pos only if limit
equals pos.
Remember that a position is always between two characters; the position returned by this function is between two characters with different properties.
next-property-change, but scans back from pos
instead of forward. If the value is non-nil, it is a position
less than or equal to pos; it equals pos only if limit
equals pos.
nil if at least one character between
start and end has a property prop whose value is
value. More precisely, it returns the position of the first such
character. Otherwise, it returns nil.
The optional fifth argument, object, specifies the string or buffer to scan. Positions are relative to object. The default for object is the current buffer.
nil if at least one character between
start and end has a property prop whose value differs
from value. More precisely, it returns the position of the
first such character. Otherwise, it returns nil.
The optional fifth argument, object, specifies the string or buffer to scan. Positions are relative to object. The default for object is the current buffer.
category
category property, we call it the
category of the character. It should be a symbol. The properties
of the symbol serve as defaults for the properties of the character.
face
face to control the font and color of
text. See section Faces, for more information. This feature is temporary;
in the future, we may replace it with other ways of specifying how to
display text.
mouse-face
mouse-face is used instead of face when the
mouse is on or near the character. For this purpose, "near" means
that all text between the character and where the mouse is have the same
mouse-face property value.
local-map
local-map property. The property's value, for the character
after point, replaces the buffer's local map. See section Active Keymaps.
read-only
read-only, then modifying that
character is not allowed. Any command that would do so gets an error.
Insertion next to a read-only character is an error if inserting
ordinary text there would inherit the read-only property due to
stickiness. Thus, you can control permission to insert next to
read-only text by controlling the stickiness. See section Stickiness of Text Properties.
Since changing properties counts as modifying the buffer, it is not
possible to remove a read-only property unless you know the
special trick: bind inhibit-read-only to a non-nil value
and then remove the property. See section Read-Only Buffers.
invisible
nil invisible property means a character does not
appear on the screen. This works much like selective display. Details
of this feature are likely to change in future versions, so check the
`etc/NEWS' file in the version you are using.
intangible
nil intangible property on a character prevents
putting point before that character. If you try, point actually goes
after the character (and after all succeeding intangible characters).
modification-hooks
modification-hooks, then its
value should be a list of functions; modifying that character calls all
of those functions. Each function receives two arguments: the beginning
and end of the part of the buffer being modified. Note that if a
particular modification hook function appears on several characters
being modified by a single primitive, you can't predict how many times
the function will be called.
insert-in-front-hooks
insert-behind-hooks
insert-in-front-hooks property of the following
character and in the insert-behind-hooks property of the
preceding character. These functions receive two arguments, the
beginning and end of the inserted text.
See also section Change Hooks, for other hooks that are called
when you change text in a buffer.
point-entered
point-left
point-entered and point-left
record hook functions that report motion of point. Each time point
moves, Emacs compares these two property values:
point-left property of the character after the old location,
and
point-entered property of the character after the new
location.
nil)
with two arguments: the old value of point, and the new one.
The same comparison is made for the characters before the old and new
locations. The result may be to execute two point-left functions
(which may be the same function) and/or two point-entered
functions (which may be the same function). The point-left
functions are always called before the point-entered functions.
A primitive function may examine characters at various positions
without moving point to those positions. Only an actual change in the
value of point runs these hook functions.
nil, point-left and
point-entered hooks are not run.
Self-inserting characters normally take on the same properties as the preceding character. This is called inheritance of properties.
In a Lisp program, you can do insertion with inheritance or without,
depending on your choice of insertion primitive. The ordinary text
insertion functions such as insert do not inherit any properties.
They insert text with precisely the properties of the string being
inserted, and no others. This is correct for programs that copy text
from one context to another--for example, into or out of the kill
ring. To insert with inheritance, use the special primatives described
in this section.
When you do insertion with inheritance, which properties are
inherited depends on two specific properties: front-sticky and
rear-nonsticky.
Insertion after a character inherits those of its properties that are rear-sticky. Insertion before a character inherits those of its properties that are front-sticky. By default, a text property is rear-sticky but not front-sticky. Thus, the default is to inherit all the properties of the preceding character, and nothing from the following character. You can request different behavior by specifying the stickiness of certain properties.
If a character's front-sticky property is t, then all
its properties are front-sticky. If the front-sticky property is
a list, then the sticky properties of the character are those whose
names are in the list. For example, if a character has a
front-sticky property whose value is (face read-only),
then insertion before the character can inherit its face property
and its read-only property, but no others.
The rear-nonsticky works the opposite way. Every property is
rear-sticky by default, so the rear-nonsticky property says which
properties are not rear-sticky. If a character's
rear-nonsticky property is t, then none of its properties
are rear-sticky. If the rear-nonsticky property is a list,
properties are rear-sticky unless their names are in the list.
When you insert text with inheritance, it inherits all the rear-sticky properties of the preceding character, and all the front-sticky properties of the following character. The previous character's properties take precedence when both sides offer different sticky values for the same property.
Here are the functions that insert text with inheritance of properties:
insert,
but inherit any sticky properties from the adjoining text.
insert-before-markers, but inherit any sticky properties from the
adjoining text.
You can save text properties in files, and restore text properties when inserting the files, using these two hooks:
write-region to
run to encode text properties in some fashion as annotations to the text
being written in the file. See section Writing to Files.
Each function in the list is called with two arguments: the start and end of the region to be written. These functions should not alter the contents of the buffer. Instead, they should return lists indicating annotations to write in the file in addition to the text in the buffer.
Each function should return a list of elements of the form
(position . string), where position is an
integer specifying the relative position in the text to be written, and
string is the annotation to add there.
Each list returned by one of these functions must be already sorted in
increasing order by position. If there is more than one function,
write-region merges the lists destructively into one sorted list.
When write-region actually writes the text from the buffer to the
file, it intermixes the specified annotations at the corresponding
positions. All this takes place without modifying the buffer.
insert-file-contents
to call after inserting a file's contents. These functions should scan
the inserted text for annotations, and convert them to the text
properties they stand for.
Each function receives one argument, the length of the inserted text; point indicates the start of that text. The function should scan that text for annotations, delete them, and create the text properties that the annotations specify. The function should return the updated length of the inserted text, as it stands after those changes. The value returned by one function becomes the argument to the next function.
These functions should always return with point at the beginning of the inserted text.
The intended use of after-insert-file-functions is for converting
some sort of textual annotations into actual text properties. But other
uses may be possible.
We invite users to write Lisp programs to store and retrieve text properties in files, using these hooks, and thus to experiment with various data formats and find good ones. Eventually we hope users will produce good, general extensions we can install in Emacs.
We suggest not trying to handle arbitrary Lisp objects as property names or property values--because a program that general is probably difficult to write, and slow. Instead, choose a set of possible data types that are reasonably flexible, and not too hard to encode.
Some editors that support adding attributes to text in the buffer do so by letting the user specify "intervals" within the text, and adding the properties to the intervals. Those editors permit the user or the programmer to determine where individual intervals start and end. We deliberately provided a different sort of interface in Emacs Lisp to avoid certain paradoxical behavior associated with text modification.
If the actual subdivision into intervals is meaningful, that means you can distinguish between a buffer that is just one interval with a certain property, and a buffer containing the same text subdivided into two intervals, both of which have that property.
Suppose you take the buffer with just one interval and kill part of the text. The text remaining in the buffer is one interval, and the copy in the kill ring (and the undo list) becomes a separate interval. Then if you yank back the killed text, you get two intervals with the same properties. Thus, editing does not preserve the distinction between one interval and two.
Suppose we "fix" this problem by coalescing the two intervals when the text is inserted. That works fine if the buffer originally was a single interval. But suppose instead that we have two adjacent intervals with the same properties, and we kill the text of one interval and yank it back. The same interval-coalescence feature that rescues the other case causes trouble in this one: after yanking, we have just one interval. One again, editing does not preserve the distinction between one interval and two.
Insertion of text at the border between intervals also raises questions that have no satisfactory answer.
However, it is easy to arrange for editing to behave consistently for questions of the form, "What are the properties of this character?" So we have decided these are the only questions that make sense; we have not implemented asking questions about where intervals start or end.
In practice, you can usually use the property search functions in place of explicit interval boundaries. You can think of them as finding the boundaries of intervals, assuming that intervals are always coalesced whenever possible. See section Property Search Functions.
Emacs also provides explicit intervals as a presentation feature; see section Overlays.
The following functions replace characters within a specified region based on their character codes.
If noundo is non-nil, then subst-char-in-region
does not record the change for undo and does not mark the buffer as
modified. This feature is useful for changes which are not considered
significant, such as when Outline mode changes visible lines to
invisible lines and vice versa.
subst-char-in-region does not move point and returns
nil.
---------- Buffer: foo ----------
This is the contents of the buffer before.
---------- Buffer: foo ----------
(subst-char-in-region 1 20 ?i ?X)
=> nil
---------- Buffer: foo ----------
ThXs Xs the contents of the buffer before.
---------- Buffer: foo ----------
The translation table table is a string; (aref table
ochar) gives the translated character corresponding to
ochar. If the length of table is less than 256, any
characters with codes larger than the length of table are not
altered by the translation.
The return value of translate-region is the number of
characters which were actually changed by the translation. This does
not count characters which were mapped into themselves in the
translation table.
This function is available in Emacs versions 19 and later.
A register is a sort of variable used in Emacs editing that can hold a marker, a string, a rectangle, a window configuration (of one frame), or a frame configuration (of all frames). Each register is named by a single character. All characters, including control and meta characters (but with the exception of C-g), can be used to name registers. Thus, there are 255 possible registers. A register is designated in Emacs Lisp by a character which is its name.
The functions in this section return unpredictable values unless otherwise stated.
(name .
contents). Normally, there is one element for each Emacs
register that has been used.
The object name is a character (an integer) identifying the register. The object contents is a string, marker, or list representing the register contents. A string represents text stored in the register. A marker represents a position. A list represents a rectangle; its elements are strings, one per line of the rectangle.
nil if it has no contents.
Normally, this command puts point before the inserted text, and the
mark after it. However, if the optional second argument beforep
is non-nil, it puts the mark before and point after.
You can pass a non-nil second argument beforep to this
function interactively by supplying any prefix argument.
If the register contains a rectangle, then the rectangle is inserted with its upper left corner at point. This means that text is inserted in the current line and underneath it on successive lines.
If the register contains something other than saved text (a string) or a rectangle (a list), currently useless things happen. This may be changed in the future.
This subroutine is used by the transposition commands.
Normally, transpose-regions relocates markers with the transposed
text; a marker previously positioned within one of the two transposed
portions moves along with that portion, thus remaining between the same
two characters in their new position. However, if leave-markers
is non-nil, transpose-regions does not do this--it leaves
all markers unrelocated.
These hook variables let you arrange to take notice of all changes in all buffers (or in a particular buffer, if you make them buffer-local). See also section Properties with Special Meanings, for how to detect changes to specific parts of the text.
The functions you use in these hooks should save and restore the match data if they do anything that uses regular expressions; otherwise, they will interfere in bizarre ways with the editing operations that call them.
nil for no function). It is called just like the functions
in before-change-functions.
nil for no function). It is called just like the functions in
after-change-functions.
The four variables above are temporarily bound to nil during the
time that any of these functions is running. This means that if one of
these functions changes the buffer, that change won't run these
functions. If you do want a hook function to make changes that run
these functions, make it bind these variables back to their usual
values.
One inconvenient result of this protective feature is that you cannot
have a function in after-change-functions or
before-change-functions which changes the value of that variable.
But that's not a real limitation. If you want those functions to change
the list of functions to run, simply add one fixed function to the hook,
and code that function to look in another variable for other functions
to call. Here is an example:
(setq my-own-after-change-functions nil)
(defun indirect-after-change-function (beg end len)
(let ((list my-own-after-change-functions))
(while list
(funcall (car list) beg end len)
(setq list (cdr list)))))
(add-hooks 'after-change-functions
'indirect-after-change-function)
The variables described in this section are meaningful only starting with Emacs version 19.