from the desk of stinkpot

how to auto-indent in emacs

February 8th, 2006 by Lawrence David

one of the reasons why i use emacs, as opposed to just a vanilla text editor, is that it auto-indents your code. all you’ve got to do is ask it to do so nicely.

just highlight the region of code you want indented (control-space at the beginning of the text block, then move the blinking cursor to the end of the text block) and hit:

>> C-M-\

or, “control-meta-backslash.”

Posted in Emacs | 10 Comments »

if that was helpful ...

check out the other tips and tricks i've compiled on these pages. you might learn something else interesting!

10 Responses to “how to auto-indent in emacs”

1. on 23 Sep 2007 at 9:23 am   x

   Not always working, maybe i’m dull on this …
   Ctrl+M just gives a newline, before hitting \

2. on 27 Sep 2007 at 6:44 pm   y

   It’s not control + M (as in shift+m) it’s control + meta, usually alt or escape. So, depending on your settings it might be control+alt+\

3. on 20 Jan 2008 at 8:05 am   noshir

   thank you

   and thank you emacs so nice this auto indent

4. on 16 Feb 2009 at 4:12 pm   me

   You’re confusing auto-indent with auto code formatting. auto-indent means that it inserts the same space before a new line as it did on the previous line.

   Automatic code formatter is a different thing entirely. Ctrl+Alt+\ is an auto code formatter. Your article caused me hours of confusion before I found out what the VI equivalent of :set ai was on emacs….

5. on 12 Mar 2009 at 6:49 am   john doe

   And could you write what is the VI equivalent od :set ai in emacs?

6. on 17 Jun 2009 at 5:55 am   Amit

   Thanks a lot !
   I used to hit tabs per line before. This is awesome. Is there a way to remove multiple blank lines and keep only one blank line ?

7. on 13 Jul 2009 at 11:09 am   octoberdan

   Thank you for the tip! Quite useful. If indent-tabs-mode is nil, will tabs be converted to spaces?

8. on 03 Aug 2009 at 5:27 pm   verma

   Works great! thanks for the tip.

9. on 29 Nov 2010 at 8:45 am   Rob Stewart

   @john doe

   There is no Emacs equivalent of vi’s :set autoindent. Instead, Emacs references a variable, indent-line-function, to determine the function to call to handle indentation. Setting indent-line-function to indent-relative or indent-relative-maybe, for example, will replicate the previous line’s indentation, according to the function’s algorithm. Normally, you don’t set indent-line-function but rather leave that to a buffer’s mode.

   For example, in an Elisp buffer, the mode is Emacs-Lisp and indent-line-function is set to list-indent-line. In a C++ file’s buffer, the mode is C++ and indent-line-function is set to c-indent-line. In a Fundamental mode buffer, indent-line-function is set to indent-line.

10. on 29 Nov 2010 at 8:47 am   Rob Stewart

    @octoberdan

    Setting indent-tabs-mode to nil will insert spaces to fill the columns a tab would have filled, but it will not convert tabs to spaces. For that you need M-x untabify.