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6bf7aab6 | 1 | @c This is part of the Emacs manual. |
62eda0e2 | 2 | @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2001, 2002, |
114f9c96 | 3 | @c 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. |
6bf7aab6 DL |
4 | @c See file emacs.texi for copying conditions. |
5 | @node Indentation, Text, Major Modes, Top | |
6 | @chapter Indentation | |
7 | @cindex indentation | |
70a9af81 | 8 | @cindex tabs |
6bf7aab6 DL |
9 | @cindex columns (indentation) |
10 | ||
11 | This chapter describes the Emacs commands that add, remove, or | |
12 | adjust indentation. | |
13 | ||
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14 | @table @kbd |
15 | @item @key{TAB} | |
70a9af81 | 16 | Indent the current line appropriately, in a mode-dependent fashion. |
6bf7aab6 DL |
17 | @item @kbd{C-j} |
18 | Perform @key{RET} followed by @key{TAB} (@code{newline-and-indent}). | |
19 | @item M-^ | |
58fa012d | 20 | Merge the previous and the current line (@code{delete-indentation}). |
66375f06 | 21 | This would cancel the effect of a preceding @kbd{C-j}. |
6bf7aab6 | 22 | @item C-M-o |
4125ceb0 EZ |
23 | Split the current line at point; text on the line after point becomes a |
24 | new line indented to the same column where point is located | |
25 | (@code{split-line}). | |
6bf7aab6 DL |
26 | @item M-m |
27 | Move (forward or back) to the first nonblank character on the current | |
28 | line (@code{back-to-indentation}). | |
29 | @item C-M-\ | |
66375f06 | 30 | Indent lines in the region to the same column (@code{indent-region}). |
6bf7aab6 | 31 | @item C-x @key{TAB} |
66375f06 | 32 | Shift lines in the region rigidly right or left (@code{indent-rigidly}). |
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33 | @item M-i |
34 | Indent from point to the next prespecified tab stop column | |
35 | (@code{tab-to-tab-stop}). | |
36 | @item M-x indent-relative | |
37 | Indent from point to under an indentation point in the previous line. | |
38 | @end table | |
39 | ||
a0377cbf | 40 | In most major modes, the @key{TAB} key runs the command |
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41 | @code{indent-for-tab-command}, which either performs indentation or |
42 | inserts whitespace at point, depending on the situation. | |
43 | ||
a0377cbf | 44 | In programming modes such as Lisp mode and C mode, @key{TAB} indents |
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45 | the current line if the region is inactive. If the region is active, |
46 | it indents every line in the region (@pxref{Mark}). Indentation means | |
47 | adding or removing some combination of space and tab characters | |
48 | (@dfn{whitespace characters}) at the start of the line, in a way that | |
49 | makes sense given the text in the preceding lines. Exactly how | |
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50 | indentation is performed depends on the major mode. @xref{Program |
51 | Indent}. | |
70a9af81 | 52 | |
a0377cbf | 53 | In text modes, @key{TAB} inserts some whitespace characters to |
70a9af81 CY |
54 | advance point to the next tab stop (@pxref{Tab Stops}). For the |
55 | purposes of this command, the position of the first non-whitespace | |
56 | character on the preceding line is treated as an additional tab stop. | |
a0377cbf CY |
57 | You can therefore use @key{TAB} to ``align'' point with the preceding |
58 | line. If the region is active, @key{TAB} performs this action on | |
70a9af81 CY |
59 | every line in the region. |
60 | ||
61 | @vindex tab-width | |
62 | Indentation is often performed with the help of @dfn{tab characters} | |
7241fdc5 | 63 | (@acronym{ASCII} code 9), which are displayed as a stretch of empty space |
70a9af81 CY |
64 | extending to the next @dfn{display tab stop}. By default, there is |
65 | one display tab stop every eight columns; the number of columns is | |
66 | determined by the variable @code{tab-width}. You can insert a single | |
67 | tab character by typing @kbd{C-q @key{TAB}}. @xref{Text Display}. | |
68 | ||
69 | @findex edit-tab-stops | |
70 | @findex tab-to-tab-stop | |
71 | @kindex M-i | |
72 | The command @kbd{M-i} (@code{tab-to-tab-stop}) adjusts the | |
73 | whitespace characters around point, inserting just enough whitespace | |
74 | to advance point up to the next tab stop. By default, this involves | |
75 | deleting the existing whitespace and inserting a single tab character. | |
76 | ||
77 | Normally, most of these indentation commands insert an optimal mix | |
78 | of tabs and spaces to align to the desired column. @xref{Just | |
79 | Spaces}, for how to disable use of tabs. However, @kbd{C-q @key{TAB}} | |
80 | always inserts a tab, even when tabs are disabled for the indentation | |
81 | commands. | |
99ffa7da | 82 | |
6bf7aab6 DL |
83 | @menu |
84 | * Indentation Commands:: Various commands and techniques for indentation. | |
85 | * Tab Stops:: You can set arbitrary "tab stops" and then | |
86 | indent to the next tab stop when you want to. | |
87 | * Just Spaces:: You can request indentation using just spaces. | |
88 | @end menu | |
89 | ||
90 | @node Indentation Commands, Tab Stops, Indentation, Indentation | |
91 | @section Indentation Commands and Techniques | |
92 | ||
93 | @kindex M-m | |
94 | @findex back-to-indentation | |
95 | To move over the indentation on a line, do @kbd{M-m} | |
96 | (@code{back-to-indentation}). This command, given anywhere on a line, | |
2aa2f8b8 LT |
97 | positions point at the first nonblank character on the line, if any, |
98 | or else at the end of the line. | |
6bf7aab6 DL |
99 | |
100 | To insert an indented line before the current line, do @kbd{C-a C-o | |
101 | @key{TAB}}. To make an indented line after the current line, use | |
102 | @kbd{C-e C-j}. | |
103 | ||
70a9af81 | 104 | If you just want to insert a tab character in the buffer, type |
6bf7aab6 DL |
105 | @kbd{C-q @key{TAB}}. |
106 | ||
107 | @kindex C-M-o | |
108 | @findex split-line | |
109 | @kbd{C-M-o} (@code{split-line}) moves the text from point to the end of | |
110 | the line vertically down, so that the current line becomes two lines. | |
111 | @kbd{C-M-o} first moves point forward over any spaces and tabs. Then it | |
112 | inserts after point a newline and enough indentation to reach the same | |
113 | column point is on. Point remains before the inserted newline; in this | |
114 | regard, @kbd{C-M-o} resembles @kbd{C-o}. | |
115 | ||
116 | @kindex M-^ | |
117 | @findex delete-indentation | |
118 | To join two lines cleanly, use the @kbd{M-^} | |
a3053e27 RS |
119 | (@code{delete-indentation}) command. It deletes the indentation at |
120 | the front of the current line, and the line boundary as well, | |
121 | replacing them with a single space. As a special case (useful for | |
122 | Lisp code) the single space is omitted if the characters to be joined | |
123 | are consecutive open parentheses or closing parentheses, or if the | |
124 | junction follows another newline. To delete just the indentation of a | |
125 | line, go to the beginning of the line and use @kbd{M-\} | |
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126 | (@code{delete-horizontal-space}), which deletes all spaces and tabs |
127 | around the cursor. | |
128 | ||
129 | If you have a fill prefix, @kbd{M-^} deletes the fill prefix if it | |
130 | appears after the newline that is deleted. @xref{Fill Prefix}. | |
131 | ||
132 | @kindex C-M-\ | |
133 | @kindex C-x TAB | |
134 | @findex indent-region | |
135 | @findex indent-rigidly | |
136 | There are also commands for changing the indentation of several lines | |
2aa2f8b8 LT |
137 | at once. They apply to all the lines that begin in the region. |
138 | @kbd{C-M-\} (@code{indent-region}) indents each line in the ``usual'' | |
139 | way, as if you had typed @key{TAB} at the beginning of the line. A | |
140 | numeric argument specifies the column to indent to, and each line is | |
141 | shifted left or right so that its first nonblank character appears in | |
142 | that column. @kbd{C-x @key{TAB}} (@code{indent-rigidly}) moves all of | |
143 | the lines in the region right by its argument (left, for negative | |
6bf7aab6 | 144 | arguments). The whole group of lines moves rigidly sideways, which is |
a3053e27 | 145 | how the command gets its name. |
6bf7aab6 | 146 | |
f98345fa | 147 | @cindex remove indentation |
a3053e27 RS |
148 | To remove all indentation from all of the lines in the region, |
149 | invoke @kbd{C-x @key{TAB}} with a large negative argument, such as | |
150 | -1000. | |
f98345fa | 151 | |
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152 | @findex indent-relative |
153 | @kbd{M-x indent-relative} indents at point based on the previous line | |
154 | (actually, the last nonempty line). It inserts whitespace at point, moving | |
2aa2f8b8 | 155 | point, until it is underneath the next indentation point in the previous line. |
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156 | An indentation point is the end of a sequence of whitespace or the end of |
157 | the line. If point is farther right than any indentation point in the | |
2aa2f8b8 | 158 | previous line, @code{indent-relative} runs @code{tab-to-tab-stop} |
29848974 | 159 | @ifnottex |
3b01b911 | 160 | (@pxref{Tab Stops}), |
29848974 | 161 | @end ifnottex |
6bf7aab6 | 162 | @iftex |
3b01b911 | 163 | (see next section), |
6bf7aab6 | 164 | @end iftex |
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165 | unless it is called with a numeric argument, in which case it does |
166 | nothing. | |
6bf7aab6 | 167 | |
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168 | @xref{Format Indentation}, for another way of specifying the |
169 | indentation for part of your text. | |
170 | ||
171 | @node Tab Stops, Just Spaces, Indentation Commands, Indentation | |
172 | @section Tab Stops | |
173 | ||
177c0ea7 | 174 | @cindex tab stops |
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175 | @cindex using tab stops in making tables |
176 | @cindex tables, indentation for | |
177 | @kindex M-i | |
178 | @findex tab-to-tab-stop | |
2aa2f8b8 LT |
179 | For typing in tables, you can use @kbd{M-i} (@code{tab-to-tab-stop}). |
180 | This command inserts indentation before point, enough to reach the | |
181 | next tab stop column. | |
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182 | |
183 | @findex edit-tab-stops | |
184 | @findex edit-tab-stops-note-changes | |
185 | @kindex C-c C-c @r{(Edit Tab Stops)} | |
186 | @vindex tab-stop-list | |
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187 | You can change the tab stops used by @kbd{M-i} and other indentation |
188 | commands, so that they need not be spaced every eight characters, or | |
189 | even regularly spaced. The tab stops are stored in the variable | |
190 | @code{tab-stop-list}, as a list of column numbers in increasing order. | |
6bf7aab6 | 191 | |
70a9af81 | 192 | A convenient way to set the tab stops is with @kbd{M-x |
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193 | edit-tab-stops}, which creates and selects a buffer containing a |
194 | description of the tab stop settings. You can edit this buffer to | |
195 | specify different tab stops, and then type @kbd{C-c C-c} to make those | |
2aa2f8b8 LT |
196 | new tab stops take effect. The buffer uses Overwrite mode |
197 | (@pxref{Minor Modes}). @code{edit-tab-stops} records which buffer was | |
198 | current when you invoked it, and stores the tab stops back in that | |
199 | buffer; normally all buffers share the same tab stops and changing | |
200 | them in one buffer affects all, but if you happen to make | |
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201 | @code{tab-stop-list} local in one buffer then @code{edit-tab-stops} in |
202 | that buffer will edit the local settings. | |
203 | ||
204 | Here is what the text representing the tab stops looks like for ordinary | |
205 | tab stops every eight columns. | |
206 | ||
207 | @example | |
208 | : : : : : : | |
209 | 0 1 2 3 4 | |
210 | 0123456789012345678901234567890123456789012345678 | |
211 | To install changes, type C-c C-c | |
212 | @end example | |
213 | ||
214 | The first line contains a colon at each tab stop. The remaining lines | |
215 | are present just to help you see where the colons are and know what to do. | |
216 | ||
70a9af81 CY |
217 | Note that the tab stops that control @code{tab-to-tab-stop} have |
218 | nothing to do with how tab characters are displayed in the buffer. | |
219 | Tab characters are always displayed as empty spaces extending to the | |
220 | next display tab stop, which occurs every @code{tab-width} columns | |
221 | regardless of the contents of @code{tab-stop-list}. @xref{Text | |
222 | Display}. | |
6bf7aab6 DL |
223 | |
224 | @node Just Spaces,, Tab Stops, Indentation | |
225 | @section Tabs vs. Spaces | |
226 | ||
227 | @vindex indent-tabs-mode | |
2e4a0639 RS |
228 | Emacs normally uses both tabs and spaces to indent lines. If you |
229 | prefer, all indentation can be made from spaces only. To request | |
230 | this, set @code{indent-tabs-mode} to @code{nil}. This is a per-buffer | |
231 | variable, so altering the variable affects only the current buffer, | |
232 | but there is a default value which you can change as well. | |
233 | @xref{Locals}. | |
6bf7aab6 | 234 | |
99ffa7da | 235 | A tab is not always displayed in the same way. By default, tabs are |
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236 | eight columns wide, but some people like to customize their editors to |
237 | use a different tab width (e.g., by changing the variable | |
238 | @code{tab-width} in Emacs). By using spaces only, you can make sure | |
99ffa7da KG |
239 | that your file looks the same regardless of the tab width setting. |
240 | ||
6bf7aab6 DL |
241 | @findex tabify |
242 | @findex untabify | |
243 | There are also commands to convert tabs to spaces or vice versa, always | |
244 | preserving the columns of all nonblank text. @kbd{M-x tabify} scans the | |
2aa2f8b8 | 245 | region for sequences of spaces, and converts sequences of at least two |
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246 | spaces to tabs if that can be done without changing indentation. @kbd{M-x |
247 | untabify} changes all tabs in the region to appropriate numbers of spaces. | |
ab5796a9 MB |
248 | |
249 | @ignore | |
250 | arch-tag: acc07de7-ae11-4ee8-a159-cb59c473f0fb | |
251 | @end ignore |