Batch Indentation with Emacs
Author: Stan Warford
Email: Message to Warford
Most visual text editors for programmers have a re-indent feature.
However, for large projects with many C/C++/Java files, I frequently
need a script that I can execute from the command line that will
indent the code in a source file without manually opening the file
in the text editor. Emacs has two versatile commands,
indent-region, that are useful when you are editing your
program with Emacs. This page describes how to apply these commands in
batch mode from the command line without ever getting into Emacs.
The Emacs script
You only need one file with the following content:
;;; File: emacs-format-file
;;; Stan Warford
;;; 17 May 2006
(defun emacs-format-function ()
"Format the whole buffer."
(indent-region (point-min) (point-max) nil)
(untabify (point-min) (point-max))
I recommend that you put a copy of this script in your
directory in a file named
The first command is
c-set-style. Emacs has a large number
of predefined styles including
My current favorite is
stroustrup as in the above script.
You can replace
stroustrup with your own choice of style.
The second command indents the entire file. The third command replaces
tabs with spaces to make the file printer-friendly. If you want tabs
in your file, omit the
untabify command. The fourth
command saves the re-indented file if necessary, that is, if the previous
commands actually changed the file.
You might wind up with the usual Emacs
~ backup file as well.
To execute the script issue the following command:
emacs -batch file-to-indent -l ~/bin/emacs-format-file -f emacs-format-function
assuming you have put the script in your
Emacs will echo the actions it is taking. If the indentation is taking a long
time it will even echo its progress.
A Bourne shell script
Of course, you probably don't want to type that long command every time
you need to indent a source file. So, here is a Bourne shell script that
wraps the command up with all the fancy error checking
bells and whistles.
I recommend that you put a copy of this script in your directory
in a file named
my-indent, or whatever else you want to call
it. Thanks to Michael Jensen for improving the script to provide multiple file
# File: my-indent
# Opens a set of files in emacs and executes the emacs-format-function.
# Assumes the function named emacs-format-function is defined in the
# file named emacs-format-file.
if [ $# == 0 ]
echo "my-indent requires at least one argument." 1>&2
echo "Usage: my-indent files-to-indent" 1>&2
while [ $# -ge 1 ]
if [ -d $1 ]
echo "Argument of my-indent $1 cannot be a directory." 1>&2
# Check for existence of file:
ls $1 2> /dev/null | grep $1 > /dev/null
if [ $? != 0 ]
echo "my-indent: $1 not found." 1>&2
echo "Indenting $1 with emacs in batch mode"
emacs -batch $1 -l ~/bin/emacs-format-file -f emacs-format-function