31.3.1 Basic Program Indentation Commands
The basic indentation commands indent a single line according to the
usual conventions of the language you are editing.
- <TAB>
- Adjust indentation of current line.
- C-j
- Equivalent to <RET> followed by <TAB> (
newline-and-indent).
- <LINEFEED>
- This key, if the keyboard has it, is another way to enter C-j.
The basic indentation command is <TAB>, which gives the current line
the correct indentation as determined from the previous lines. The
function that <TAB> runs depends on the major mode; it is
lisp-indent-line
in Lisp mode, c-indent-command in C mode, etc. These functions
understand the syntax and conventions of different languages, but they all do
conceptually the same job: <TAB> in any programming-language major mode
inserts or deletes whitespace at the beginning of the current line,
independent of where point is in the line. If point was inside the
whitespace at the beginning of the line, <TAB> puts it at the end of
that whitespace; otherwise, <TAB> keeps point fixed with respect to
the characters around it.
Use C-q <TAB> to insert a tab character at point.
When entering lines of new code, use C-j
(newline-and-indent), which is equivalent to a <RET>
followed by a <TAB>. C-j at the end of a line creates a
blank line and then gives it the appropriate indentation.
<TAB> indents a line that starts within a parenthetical grouping
under the preceding line within the grouping, or the text after the
parenthesis. Therefore, if you manually give one of these lines a
nonstandard indentation, the lines below will tend to follow it. This
behavior is convenient in cases where you have overridden the standard
result of <TAB> because you find it unaesthetic for a particular
line.
By default, an open-parenthesis, open-brace or other opening
delimiter at the left margin is assumed by Emacs (including the
indentation routines) to be the start of a function. This speeds up
indentation commands. If you will be editing text which contains
opening delimiters in column zero that aren't the beginning of a
functions, even inside strings or comments, you must set
open-paren-in-column-0-is-defun-start. See Left Margin Paren, for more information on this.
Normally, lines are indented with tabs and spaces. If you want Emacs
to use spaces only, see Just Spaces.
