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How to Add a New Applet to BusyBox
==================================
This document details the steps you must take to add a new applet to BusyBox.
Credits:
Matt Kraai - initial writeup
Mark Whitley - the remix
Initial Write
-------------
First, write your applet. Be sure to include copyright information at the
top, such as who you stole the code from and so forth. Also include the
mini-GPL boilerplate. Be sure to name the main function <applet>_main instead
of main. And be sure to put it in <applet>.c. For a new applet mu, here is
the code that would go in mu.c:
----begin example code------
/* vi: set sw=4 ts=4: */
/*
* Mini mu implementation for busybox
*
*
* Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
* 02111-1307 USA
*
*/
#include "busybox.h"
int mu_main(int argc, char **argv)
{
int fd;
char mu;
if ((fd = open("/dev/random", O_RDONLY)) < 0)
perror_msg_and_die("/dev/random");
if ((n = safe_read(fd, &mu, 1)) < 1)
perror_msg_and_die("/dev/random");
return mu;
}
----end example code------
Coding Style
------------
Before you submit your applet for inclusion in BusyBox, (or better yet, before
you _write_ your applet) please read through the style guide in the docs
directory and make your program compliant.
Some Words on libbb
-------------------
As you are writing your applet, please be aware of the body of pre-existing
useful functions in libbb. Use these instead of reinventing the wheel.
Additionally, if you have any useful, general-purpose functions in your
program that could be useful in another program, consider putting them in
libbb.
Usage String(s)
---------------
Next, add usage information for you applet to usage.h. This should look like
the following:
#define mu_trivial_usage \
"-[abcde] FILES"
#define mu_full_usage \
"Returns an indeterminate value.\n\n" \
"Options:\n" \
"\t-a\t\tfirst function\n" \
"\t-b\t\tsecond function\n" \
If your program supports flags, the flags should be mentioned on the first
line (-[abcde]) and a detailed description of each flag should go in the
mu_full_usage section, one flag per line. (Numerous examples of this
currently exist in usage.h.)
Header Files
------------
Next, add an entry to applets.h. Be *sure* to keep the list in alphabetical
order, or else it will break the binary-search lookup algorithm in busybox.c
and the Gods of BusyBox smite you. Yea, verily:
/* all programs above here are alphabetically "less than" 'mu' */
#ifdef CONFIG_MU
APPLET("mu", mu_main, _BB_DIR_USR_BIN, mu_usage)
#endif
/* all programs below here are alphabetically "greater than" 'mu' */
Finally, add a define for your applet to Config.h:
#define CONFIG_MU
Documentation
-------------
If you're feeling especially nice, you should also document your applet in the
docs directory (but nobody ever does that).
The Grand Announcement
----------------------
Then create a diff -urN of the files you added (<applet>.c, usage.c,
applets.h, Config.h) and send it to the mailing list:
busybox@opensource.lineo.com. Sending patches as attachments is preferred, but
not required.
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