@c This is part of the Emacs manual. @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2001, 2002, @c 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. @c See file emacs.texi for copying conditions. @node Indentation, Text, Major Modes, Top @chapter Indentation @cindex indentation @cindex columns (indentation) This chapter describes the Emacs commands that add, remove, or adjust indentation. @table @kbd @item @key{TAB} Indent the current line ``appropriately'' in a mode-dependent fashion. @item @kbd{C-j} Perform @key{RET} followed by @key{TAB} (@code{newline-and-indent}). @item M-^ Merge the previous and the current line (@code{delete-indentation}). This would cancel the effect of a preceding @kbd{C-j}. @item C-M-o Split the current line at point; text on the line after point becomes a new line indented to the same column where point is located (@code{split-line}). @item M-m Move (forward or back) to the first nonblank character on the current line (@code{back-to-indentation}). @item C-M-\ Indent lines in the region to the same column (@code{indent-region}). @item C-x @key{TAB} Shift lines in the region rigidly right or left (@code{indent-rigidly}). @item M-i Indent from point to the next prespecified tab stop column (@code{tab-to-tab-stop}). @item M-x indent-relative Indent from point to under an indentation point in the previous line. @end table Emacs supports four general categories of operations that could all be called `indentation': @enumerate @item Insert a tab character. You can type @kbd{C-q @key{TAB}} to do this. A tab character is displayed as a stretch of whitespace which extends to the next display tab stop position, and the default width of a tab stop is eight. @xref{Text Display}, for more details. @item Insert whitespace up to the next tab stop. You can set tab stops at your choice of column positions, then type @kbd{M-i} to advance to the next tab stop. The default tab stop settings have a tab stop every eight columns, which means by default @kbd{M-i} inserts a tab character. To set the tab stops, use @kbd{M-x edit-tab-stops}. @item Align a line with the previous line. More precisely, the command @kbd{M-x indent-relative} indents the current line under the beginning of some word in the previous line. In Fundamental mode and in Text mode, @key{TAB} runs the command @code{indent-relative}. @item The most sophisticated method is @dfn{syntax-driven indentation}. Most programming languages have an indentation convention. For Lisp code, lines are indented according to their nesting in parentheses. C code uses the same general idea, but many details are different. @kindex TAB Type @key{TAB} to do syntax-driven indentation, in a mode that supports it. It realigns the current line according with the syntax of the preceding lines. No matter where in the line you are when you type @key{TAB}, it aligns the line as a whole. @end enumerate Normally, most of the above methods insert an optimal mix of tabs and spaces to align to the desired column. @xref{Just Spaces}, for how to disable use of tabs. However, @kbd{C-q @key{TAB}} always inserts a tab, even when tabs are disabled for the indentation commands. @menu * Indentation Commands:: Various commands and techniques for indentation. * Tab Stops:: You can set arbitrary "tab stops" and then indent to the next tab stop when you want to. * Just Spaces:: You can request indentation using just spaces. @end menu @node Indentation Commands, Tab Stops, Indentation, Indentation @section Indentation Commands and Techniques @kindex M-m @findex back-to-indentation To move over the indentation on a line, do @kbd{M-m} (@code{back-to-indentation}). This command, given anywhere on a line, positions point at the first nonblank character on the line, if any, or else at the end of the line. To insert an indented line before the current line, do @kbd{C-a C-o @key{TAB}}. To make an indented line after the current line, use @kbd{C-e C-j}. If you just want to insert a tab character in the buffer, you can type @kbd{C-q @key{TAB}}. @kindex C-M-o @findex split-line @kbd{C-M-o} (@code{split-line}) moves the text from point to the end of the line vertically down, so that the current line becomes two lines. @kbd{C-M-o} first moves point forward over any spaces and tabs. Then it inserts after point a newline and enough indentation to reach the same column point is on. Point remains before the inserted newline; in this regard, @kbd{C-M-o} resembles @kbd{C-o}. @kindex M-^ @findex delete-indentation To join two lines cleanly, use the @kbd{M-^} (@code{delete-indentation}) command. It deletes the indentation at the front of the current line, and the line boundary as well, replacing them with a single space. As a special case (useful for Lisp code) the single space is omitted if the characters to be joined are consecutive open parentheses or closing parentheses, or if the junction follows another newline. To delete just the indentation of a line, go to the beginning of the line and use @kbd{M-\} (@code{delete-horizontal-space}), which deletes all spaces and tabs around the cursor. If you have a fill prefix, @kbd{M-^} deletes the fill prefix if it appears after the newline that is deleted. @xref{Fill Prefix}. @kindex C-M-\ @kindex C-x TAB @findex indent-region @findex indent-rigidly There are also commands for changing the indentation of several lines at once. They apply to all the lines that begin in the region. @kbd{C-M-\} (@code{indent-region}) indents each line in the ``usual'' way, as if you had typed @key{TAB} at the beginning of the line. A numeric argument specifies the column to indent to, and each line is shifted left or right so that its first nonblank character appears in that column. @kbd{C-x @key{TAB}} (@code{indent-rigidly}) moves all of the lines in the region right by its argument (left, for negative arguments). The whole group of lines moves rigidly sideways, which is how the command gets its name. @cindex remove indentation To remove all indentation from all of the lines in the region, invoke @kbd{C-x @key{TAB}} with a large negative argument, such as -1000. @findex indent-relative @kbd{M-x indent-relative} indents at point based on the previous line (actually, the last nonempty line). It inserts whitespace at point, moving point, until it is underneath the next indentation point in the previous line. An indentation point is the end of a sequence of whitespace or the end of the line. If point is farther right than any indentation point in the previous line, @code{indent-relative} runs @code{tab-to-tab-stop} @ifnottex (@pxref{Tab Stops}), @end ifnottex @iftex (see next section), @end iftex unless it is called with a numeric argument, in which case it does nothing. @xref{Format Indentation}, for another way of specifying the indentation for part of your text. @node Tab Stops, Just Spaces, Indentation Commands, Indentation @section Tab Stops @cindex tab stops @cindex using tab stops in making tables @cindex tables, indentation for @kindex M-i @findex tab-to-tab-stop For typing in tables, you can use @kbd{M-i} (@code{tab-to-tab-stop}). This command inserts indentation before point, enough to reach the next tab stop column. @findex edit-tab-stops @findex edit-tab-stops-note-changes @kindex C-c C-c @r{(Edit Tab Stops)} @vindex tab-stop-list You can specify the tab stops used by @kbd{M-i}. They are stored in a variable called @code{tab-stop-list}, as a list of column-numbers in increasing order. The convenient way to set the tab stops is with @kbd{M-x edit-tab-stops}, which creates and selects a buffer containing a description of the tab stop settings. You can edit this buffer to specify different tab stops, and then type @kbd{C-c C-c} to make those new tab stops take effect. The buffer uses Overwrite mode (@pxref{Minor Modes}). @code{edit-tab-stops} records which buffer was current when you invoked it, and stores the tab stops back in that buffer; normally all buffers share the same tab stops and changing them in one buffer affects all, but if you happen to make @code{tab-stop-list} local in one buffer then @code{edit-tab-stops} in that buffer will edit the local settings. Here is what the text representing the tab stops looks like for ordinary tab stops every eight columns. @example : : : : : : 0 1 2 3 4 0123456789012345678901234567890123456789012345678 To install changes, type C-c C-c @end example The first line contains a colon at each tab stop. The remaining lines are present just to help you see where the colons are and know what to do. Note that the tab stops that control @code{tab-to-tab-stop} have nothing to do with displaying tab characters in the buffer. @xref{Text Display}, for more information on that. @node Just Spaces,, Tab Stops, Indentation @section Tabs vs. Spaces @vindex indent-tabs-mode Emacs normally uses both tabs and spaces to indent lines. If you prefer, all indentation can be made from spaces only. To request this, set @code{indent-tabs-mode} to @code{nil}. This is a per-buffer variable, so altering the variable affects only the current buffer, but there is a default value which you can change as well. @xref{Locals}. A tab is not always displayed in the same way. By default, tabs are eight columns wide, but some people like to customize their tools to use a different tab width. So by using spaces only, you can make sure that your file looks the same regardless of the tab width setting. @findex tabify @findex untabify There are also commands to convert tabs to spaces or vice versa, always preserving the columns of all nonblank text. @kbd{M-x tabify} scans the region for sequences of spaces, and converts sequences of at least two spaces to tabs if that can be done without changing indentation. @kbd{M-x untabify} changes all tabs in the region to appropriate numbers of spaces. @ignore arch-tag: acc07de7-ae11-4ee8-a159-cb59c473f0fb @end ignore