1 How to Add a New Applet to BusyBox
2 ==================================
4 This document details the steps you must take to add a new applet to BusyBox.
7 Matt Kraai - initial writeup
8 Mark Whitley - the remix
9 Thomas Lundquist - Trying to keep it updated.
11 When doing this you should consider using the latest svn trunk.
12 This is a good thing if you plan to getting it commited into mainline.
17 First, write your applet. Be sure to include copyright information at the top,
18 such as who you stole the code from and so forth. Also include the mini-GPL
19 boilerplate. Be sure to name the main function <applet>_main instead of main.
20 And be sure to put it in <applet>.c. Usage does not have to be taken care of by
22 Make sure to #include "libbb.h" as the first include file in your applet so
23 the bb_config.h and appropriate platform specific files are included properly.
25 For a new applet mu, here is the code that would go in mu.c:
27 (busybox.h already includes most usual header files. You do not need
28 #include <stdio.h> etc...)
31 ----begin example code------
33 /* vi: set sw=4 ts=4: */
35 * Mini mu implementation for busybox
37 * Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
39 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
45 int mu_main(int argc, char **argv);
46 int mu_main(int argc, char **argv)
51 fd = xopen("/dev/random", O_RDONLY);
53 if ((n = safe_read(fd, &mu, 1)) < 1)
54 bb_perror_msg_and_die("/dev/random");
59 ----end example code------
65 Before you submit your applet for inclusion in BusyBox, (or better yet, before
66 you _write_ your applet) please read through the style guide in the docs
67 directory and make your program compliant.
73 As you are writing your applet, please be aware of the body of pre-existing
74 useful functions in libbb. Use these instead of reinventing the wheel.
76 Additionally, if you have any useful, general-purpose functions in your
77 applet that could be useful in other applets, consider putting them in libbb.
79 And it may be possible that some of the other applets uses functions you
80 could use. If so, you have to rip the function out of the applet and make
81 a libbb function out of it.
83 Adding a libbb function:
84 ------------------------
86 Make a new file named <function_name>.c
88 ----start example code------
98 ----end example code------
100 Add <function_name>.o in the right alphabetically sorted place
101 in libbb/Kbuild. You should look at the conditional part of
104 You should also try to find a suitable place in include/libbb.h for
105 the function declaration. If not, add it somewhere anyway, with or without
106 ifdefs to include or not.
108 You can look at libbb/Config.in and try to find out if the function is
109 tuneable and add it there if it is.
112 Placement / Directory
113 ---------------------
115 Find the appropriate directory for your new applet.
117 Make sure you find the appropriate places in the files, the applets are
118 sorted alphabetically.
120 Add the applet to Kbuild in the chosen directory:
122 lib-$(CONFIG_MU) += mu.o
124 Add the applet to Config.in in the chosen directory:
130 Returns an indeterminate value.
136 Next, add usage information for you applet to include/usage.h.
137 This should look like the following:
139 #define mu_trivial_usage \
141 #define mu_full_usage \
142 "Returns an indeterminate value.\n\n" \
144 "\t-a\t\tfirst function\n" \
145 "\t-b\t\tsecond function\n" \
148 If your program supports flags, the flags should be mentioned on the first
149 line (-[abcde]) and a detailed description of each flag should go in the
150 mu_full_usage section, one flag per line. (Numerous examples of this
151 currently exist in usage.h.)
157 Next, add an entry to include/applets.h. Be *sure* to keep the list
158 in alphabetical order, or else it will break the binary-search lookup
159 algorithm in busybox.c and the Gods of BusyBox smite you. Yea, verily:
161 Be sure to read the top of applets.h before adding your applet.
163 /* all programs above here are alphabetically "less than" 'mu' */
164 USE_MU(APPLET(mu, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
165 /* all programs below here are alphabetically "greater than" 'mu' */
168 The Grand Announcement
169 ----------------------
171 Then create a diff by adding the new files with svn (remember your libbb files)
172 svn add <where you put it>/mu.c
174 svn add libbb/function.c
177 and send it to the mailing list:
179 http://busybox.net/mailman/listinfo/busybox
181 Sending patches as attachments is preferred, but not required.