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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, |
3f548a7c | 3 | @c 2003, 2004, 2005, 2006, 2007, 2008 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 | |
8 | @cindex columns (indentation) | |
9 | ||
10 | This chapter describes the Emacs commands that add, remove, or | |
11 | adjust indentation. | |
12 | ||
6bf7aab6 DL |
13 | @table @kbd |
14 | @item @key{TAB} | |
58fa012d | 15 | Indent the current line ``appropriately'' in a mode-dependent fashion. |
6bf7aab6 DL |
16 | @item @kbd{C-j} |
17 | Perform @key{RET} followed by @key{TAB} (@code{newline-and-indent}). | |
18 | @item M-^ | |
58fa012d | 19 | Merge the previous and the current line (@code{delete-indentation}). |
66375f06 | 20 | This would cancel the effect of a preceding @kbd{C-j}. |
6bf7aab6 | 21 | @item C-M-o |
4125ceb0 EZ |
22 | Split the current line at point; text on the line after point becomes a |
23 | new line indented to the same column where point is located | |
24 | (@code{split-line}). | |
6bf7aab6 DL |
25 | @item M-m |
26 | Move (forward or back) to the first nonblank character on the current | |
27 | line (@code{back-to-indentation}). | |
28 | @item C-M-\ | |
66375f06 | 29 | Indent lines in the region to the same column (@code{indent-region}). |
6bf7aab6 | 30 | @item C-x @key{TAB} |
66375f06 | 31 | Shift lines in the region rigidly right or left (@code{indent-rigidly}). |
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32 | @item M-i |
33 | Indent from point to the next prespecified tab stop column | |
34 | (@code{tab-to-tab-stop}). | |
35 | @item M-x indent-relative | |
36 | Indent from point to under an indentation point in the previous line. | |
37 | @end table | |
38 | ||
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39 | Emacs supports four general categories of operations that could all |
40 | be called `indentation': | |
41 | ||
42 | @enumerate | |
43 | @item | |
5ba75c80 | 44 | Insert a tab character. You can type @kbd{C-q @key{TAB}} to do this. |
99ffa7da KG |
45 | |
46 | A tab character is displayed as a stretch of whitespace which extends | |
47 | to the next display tab stop position, and the default width of a tab | |
a3053e27 | 48 | stop is eight. @xref{Text Display}, for more details. |
99ffa7da KG |
49 | |
50 | @item | |
66375f06 RS |
51 | Insert whitespace up to the next tab stop. You can set tab stops at |
52 | your choice of column positions, then type @kbd{M-i} to advance to the | |
53 | next tab stop. The default tab stop settings have a tab stop every | |
54 | eight columns, which means by default @kbd{M-i} inserts a tab | |
55 | character. To set the tab stops, use @kbd{M-x edit-tab-stops}. | |
99ffa7da KG |
56 | |
57 | @item | |
5ba75c80 RS |
58 | Align a line with the previous line. More precisely, the command |
59 | @kbd{M-x indent-relative} indents the current line under the beginning | |
60 | of some word in the previous line. In Fundamental mode and in Text | |
61 | mode, @key{TAB} runs the command @code{indent-relative}. | |
99ffa7da KG |
62 | |
63 | @item | |
5ba75c80 RS |
64 | The most sophisticated method is @dfn{syntax-driven indentation}. |
65 | Most programming languages have an indentation convention. For Lisp | |
66 | code, lines are indented according to their nesting in parentheses. C | |
67 | code uses the same general idea, but many details are different. | |
99ffa7da | 68 | |
6bf7aab6 | 69 | @kindex TAB |
5ba75c80 RS |
70 | Type @key{TAB} to do syntax-driven indentation, in a mode that |
71 | supports it. It realigns the current line according with the syntax | |
72 | of the preceding lines. No matter where in the line you are when you | |
73 | type @key{TAB}, it aligns the line as a whole. | |
99ffa7da | 74 | @end enumerate |
6bf7aab6 | 75 | |
66375f06 | 76 | Normally, most of the above methods insert an optimal mix of tabs and |
5ba75c80 RS |
77 | spaces to align to the desired column. @xref{Just Spaces}, for how to |
78 | disable use of tabs. However, @kbd{C-q @key{TAB}} always inserts a | |
2aa2f8b8 | 79 | tab, even when tabs are disabled for the indentation commands. |
99ffa7da | 80 | |
6bf7aab6 DL |
81 | @menu |
82 | * Indentation Commands:: Various commands and techniques for indentation. | |
83 | * Tab Stops:: You can set arbitrary "tab stops" and then | |
84 | indent to the next tab stop when you want to. | |
85 | * Just Spaces:: You can request indentation using just spaces. | |
86 | @end menu | |
87 | ||
88 | @node Indentation Commands, Tab Stops, Indentation, Indentation | |
89 | @section Indentation Commands and Techniques | |
90 | ||
91 | @kindex M-m | |
92 | @findex back-to-indentation | |
93 | To move over the indentation on a line, do @kbd{M-m} | |
94 | (@code{back-to-indentation}). This command, given anywhere on a line, | |
2aa2f8b8 LT |
95 | positions point at the first nonblank character on the line, if any, |
96 | or else at the end of the line. | |
6bf7aab6 DL |
97 | |
98 | To insert an indented line before the current line, do @kbd{C-a C-o | |
99 | @key{TAB}}. To make an indented line after the current line, use | |
100 | @kbd{C-e C-j}. | |
101 | ||
102 | If you just want to insert a tab character in the buffer, you can type | |
103 | @kbd{C-q @key{TAB}}. | |
104 | ||
105 | @kindex C-M-o | |
106 | @findex split-line | |
107 | @kbd{C-M-o} (@code{split-line}) moves the text from point to the end of | |
108 | the line vertically down, so that the current line becomes two lines. | |
109 | @kbd{C-M-o} first moves point forward over any spaces and tabs. Then it | |
110 | inserts after point a newline and enough indentation to reach the same | |
111 | column point is on. Point remains before the inserted newline; in this | |
112 | regard, @kbd{C-M-o} resembles @kbd{C-o}. | |
113 | ||
114 | @kindex M-^ | |
115 | @findex delete-indentation | |
116 | To join two lines cleanly, use the @kbd{M-^} | |
a3053e27 RS |
117 | (@code{delete-indentation}) command. It deletes the indentation at |
118 | the front of the current line, and the line boundary as well, | |
119 | replacing them with a single space. As a special case (useful for | |
120 | Lisp code) the single space is omitted if the characters to be joined | |
121 | are consecutive open parentheses or closing parentheses, or if the | |
122 | junction follows another newline. To delete just the indentation of a | |
123 | line, go to the beginning of the line and use @kbd{M-\} | |
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124 | (@code{delete-horizontal-space}), which deletes all spaces and tabs |
125 | around the cursor. | |
126 | ||
127 | If you have a fill prefix, @kbd{M-^} deletes the fill prefix if it | |
128 | appears after the newline that is deleted. @xref{Fill Prefix}. | |
129 | ||
130 | @kindex C-M-\ | |
131 | @kindex C-x TAB | |
132 | @findex indent-region | |
133 | @findex indent-rigidly | |
134 | There are also commands for changing the indentation of several lines | |
2aa2f8b8 LT |
135 | at once. They apply to all the lines that begin in the region. |
136 | @kbd{C-M-\} (@code{indent-region}) indents each line in the ``usual'' | |
137 | way, as if you had typed @key{TAB} at the beginning of the line. A | |
138 | numeric argument specifies the column to indent to, and each line is | |
139 | shifted left or right so that its first nonblank character appears in | |
140 | that column. @kbd{C-x @key{TAB}} (@code{indent-rigidly}) moves all of | |
141 | the lines in the region right by its argument (left, for negative | |
6bf7aab6 | 142 | arguments). The whole group of lines moves rigidly sideways, which is |
a3053e27 | 143 | how the command gets its name. |
6bf7aab6 | 144 | |
f98345fa | 145 | @cindex remove indentation |
a3053e27 RS |
146 | To remove all indentation from all of the lines in the region, |
147 | invoke @kbd{C-x @key{TAB}} with a large negative argument, such as | |
148 | -1000. | |
f98345fa | 149 | |
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150 | @findex indent-relative |
151 | @kbd{M-x indent-relative} indents at point based on the previous line | |
152 | (actually, the last nonempty line). It inserts whitespace at point, moving | |
2aa2f8b8 | 153 | point, until it is underneath the next indentation point in the previous line. |
6bf7aab6 DL |
154 | An indentation point is the end of a sequence of whitespace or the end of |
155 | the line. If point is farther right than any indentation point in the | |
2aa2f8b8 | 156 | previous line, @code{indent-relative} runs @code{tab-to-tab-stop} |
29848974 | 157 | @ifnottex |
3b01b911 | 158 | (@pxref{Tab Stops}), |
29848974 | 159 | @end ifnottex |
6bf7aab6 | 160 | @iftex |
3b01b911 | 161 | (see next section), |
6bf7aab6 | 162 | @end iftex |
3b01b911 EZ |
163 | unless it is called with a numeric argument, in which case it does |
164 | nothing. | |
6bf7aab6 | 165 | |
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166 | @xref{Format Indentation}, for another way of specifying the |
167 | indentation for part of your text. | |
168 | ||
169 | @node Tab Stops, Just Spaces, Indentation Commands, Indentation | |
170 | @section Tab Stops | |
171 | ||
177c0ea7 | 172 | @cindex tab stops |
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173 | @cindex using tab stops in making tables |
174 | @cindex tables, indentation for | |
175 | @kindex M-i | |
176 | @findex tab-to-tab-stop | |
2aa2f8b8 LT |
177 | For typing in tables, you can use @kbd{M-i} (@code{tab-to-tab-stop}). |
178 | This command inserts indentation before point, enough to reach the | |
179 | next tab stop column. | |
6bf7aab6 DL |
180 | |
181 | @findex edit-tab-stops | |
182 | @findex edit-tab-stops-note-changes | |
183 | @kindex C-c C-c @r{(Edit Tab Stops)} | |
184 | @vindex tab-stop-list | |
185 | You can specify the tab stops used by @kbd{M-i}. They are stored in a | |
186 | variable called @code{tab-stop-list}, as a list of column-numbers in | |
187 | increasing order. | |
188 | ||
189 | The convenient way to set the tab stops is with @kbd{M-x | |
190 | edit-tab-stops}, which creates and selects a buffer containing a | |
191 | description of the tab stop settings. You can edit this buffer to | |
192 | specify different tab stops, and then type @kbd{C-c C-c} to make those | |
2aa2f8b8 LT |
193 | new tab stops take effect. The buffer uses Overwrite mode |
194 | (@pxref{Minor Modes}). @code{edit-tab-stops} records which buffer was | |
195 | current when you invoked it, and stores the tab stops back in that | |
196 | buffer; normally all buffers share the same tab stops and changing | |
197 | them in one buffer affects all, but if you happen to make | |
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198 | @code{tab-stop-list} local in one buffer then @code{edit-tab-stops} in |
199 | that buffer will edit the local settings. | |
200 | ||
201 | Here is what the text representing the tab stops looks like for ordinary | |
202 | tab stops every eight columns. | |
203 | ||
204 | @example | |
205 | : : : : : : | |
206 | 0 1 2 3 4 | |
207 | 0123456789012345678901234567890123456789012345678 | |
208 | To install changes, type C-c C-c | |
209 | @end example | |
210 | ||
211 | The first line contains a colon at each tab stop. The remaining lines | |
212 | are present just to help you see where the colons are and know what to do. | |
213 | ||
214 | Note that the tab stops that control @code{tab-to-tab-stop} have nothing | |
d5943da3 | 215 | to do with displaying tab characters in the buffer. @xref{Text Display}, |
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216 | for more information on that. |
217 | ||
218 | @node Just Spaces,, Tab Stops, Indentation | |
219 | @section Tabs vs. Spaces | |
220 | ||
221 | @vindex indent-tabs-mode | |
2e4a0639 RS |
222 | Emacs normally uses both tabs and spaces to indent lines. If you |
223 | prefer, all indentation can be made from spaces only. To request | |
224 | this, set @code{indent-tabs-mode} to @code{nil}. This is a per-buffer | |
225 | variable, so altering the variable affects only the current buffer, | |
226 | but there is a default value which you can change as well. | |
227 | @xref{Locals}. | |
6bf7aab6 | 228 | |
99ffa7da KG |
229 | A tab is not always displayed in the same way. By default, tabs are |
230 | eight columns wide, but some people like to customize their tools to | |
231 | use a different tab width. So by using spaces only, you can make sure | |
232 | that your file looks the same regardless of the tab width setting. | |
233 | ||
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234 | @findex tabify |
235 | @findex untabify | |
236 | There are also commands to convert tabs to spaces or vice versa, always | |
237 | preserving the columns of all nonblank text. @kbd{M-x tabify} scans the | |
2aa2f8b8 | 238 | region for sequences of spaces, and converts sequences of at least two |
6bf7aab6 DL |
239 | spaces to tabs if that can be done without changing indentation. @kbd{M-x |
240 | untabify} changes all tabs in the region to appropriate numbers of spaces. | |
ab5796a9 MB |
241 | |
242 | @ignore | |
243 | arch-tag: acc07de7-ae11-4ee8-a159-cb59c473f0fb | |
244 | @end ignore |