1 | How to Add a New Applet to BusyBox
|
---|
2 | ==================================
|
---|
3 |
|
---|
4 | This document details the steps you must take to add a new applet to BusyBox.
|
---|
5 |
|
---|
6 | Credits:
|
---|
7 | Matt Kraai - initial writeup
|
---|
8 | Mark Whitley - the remix
|
---|
9 | Thomas Lundquist - trying to keep it updated
|
---|
10 |
|
---|
11 | When doing this you should consider using the latest git HEAD.
|
---|
12 | This is a good thing if you plan to getting it committed into mainline.
|
---|
13 |
|
---|
14 | Initial Write
|
---|
15 | -------------
|
---|
16 |
|
---|
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 and Config.in/Kbuild/usage/applet.h snippets (more on that below
|
---|
20 | in this document). Be sure to name the main function <applet>_main instead
|
---|
21 | of main. And be sure to put it in <applet>.c. Make sure to #include "libbb.h"
|
---|
22 | as the first include file in your applet.
|
---|
23 |
|
---|
24 | For a new applet mu, here is the code that would go in mu.c:
|
---|
25 |
|
---|
26 | (libbb.h already includes most usual header files. You do not need
|
---|
27 | #include <stdio.h> etc...)
|
---|
28 |
|
---|
29 |
|
---|
30 | ----begin example code------
|
---|
31 |
|
---|
32 | /* vi: set sw=4 ts=4: */
|
---|
33 | /*
|
---|
34 | * Mini mu implementation for busybox
|
---|
35 | *
|
---|
36 | * Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
|
---|
37 | *
|
---|
38 | * Licensed under GPLv2, see file LICENSE in this source tree.
|
---|
39 | */
|
---|
40 |
|
---|
41 | #include "libbb.h"
|
---|
42 | #include "other.h"
|
---|
43 |
|
---|
44 | //config:config MU
|
---|
45 | //config: bool "MU"
|
---|
46 | //config: default y
|
---|
47 | //config: help
|
---|
48 | //config: Returns an indeterminate value.
|
---|
49 |
|
---|
50 | //kbuild:lib-$(CONFIG_MU) += mu.o
|
---|
51 | //applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
|
---|
52 |
|
---|
53 | //usage:#define mu_trivial_usage
|
---|
54 | //usage: "[-abcde] FILE..."
|
---|
55 | //usage:#define mu_full_usage
|
---|
56 | //usage: "Returns an indeterminate value\n"
|
---|
57 | //usage: "\n -a First function"
|
---|
58 | //usage: "\n -b Second function"
|
---|
59 |
|
---|
60 | int mu_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
61 | int mu_main(int argc, char **argv)
|
---|
62 | {
|
---|
63 | int fd;
|
---|
64 | ssize_t n;
|
---|
65 | char mu;
|
---|
66 |
|
---|
67 | fd = xopen("/dev/random", O_RDONLY);
|
---|
68 |
|
---|
69 | if ((n = safe_read(fd, &mu, 1)) < 1)
|
---|
70 | bb_perror_msg_and_die("/dev/random");
|
---|
71 |
|
---|
72 | return mu;
|
---|
73 | }
|
---|
74 |
|
---|
75 | ----end example code------
|
---|
76 |
|
---|
77 |
|
---|
78 | Coding Style
|
---|
79 | ------------
|
---|
80 |
|
---|
81 | Before you submit your applet for inclusion in BusyBox, (or better yet, before
|
---|
82 | you _write_ your applet) please read through the style guide in the docs
|
---|
83 | directory and make your program compliant.
|
---|
84 |
|
---|
85 |
|
---|
86 | Some Words on libbb
|
---|
87 | -------------------
|
---|
88 |
|
---|
89 | As you are writing your applet, please be aware of the body of pre-existing
|
---|
90 | useful functions in libbb. Use these instead of reinventing the wheel.
|
---|
91 |
|
---|
92 | Additionally, if you have any useful, general-purpose functions in your
|
---|
93 | applet that could be useful in other applets, consider putting them in libbb.
|
---|
94 |
|
---|
95 | And it may be possible that some of the other applets uses functions you
|
---|
96 | could use. If so, you have to rip the function out of the applet and make
|
---|
97 | a libbb function out of it.
|
---|
98 |
|
---|
99 | Adding a libbb function:
|
---|
100 | ------------------------
|
---|
101 |
|
---|
102 | Make a new file named <function_name>.c
|
---|
103 |
|
---|
104 | ----start example code------
|
---|
105 |
|
---|
106 | #include "libbb.h"
|
---|
107 | #include "other.h"
|
---|
108 |
|
---|
109 | //kbuild:lib-y += function.o
|
---|
110 |
|
---|
111 | int function(char *a)
|
---|
112 | {
|
---|
113 | return *a;
|
---|
114 | }
|
---|
115 |
|
---|
116 | ----end example code------
|
---|
117 |
|
---|
118 | Remember about the kbuild snippet.
|
---|
119 |
|
---|
120 | You should also try to find a suitable place in include/libbb.h for
|
---|
121 | the function declaration. If not, add it somewhere anyway, with or without
|
---|
122 | ifdefs to include or not.
|
---|
123 |
|
---|
124 | You can look at libbb/Config.src and try to find out if the function is
|
---|
125 | tunable and add it there if it is.
|
---|
126 |
|
---|
127 |
|
---|
128 | Kbuild/Config.in/usage/applets.h snippets in .c files
|
---|
129 | -----------------------------------------------------
|
---|
130 |
|
---|
131 | The old way of adding new applets was to put all the information needed by the
|
---|
132 | configuration and build system into appropriate files (namely: Kbuild.src and
|
---|
133 | Config.src in new applet's directory) and to add the applet declaration and
|
---|
134 | usage info text to include/applets.src.h and include/usage.src.h respectively.
|
---|
135 |
|
---|
136 | Since the scripts/gen_build_files.sh script had been introduced, the preferred
|
---|
137 | way is to have all these declarations contained within the applet .c files.
|
---|
138 |
|
---|
139 | Every line intended to be processed by gen_build_files.sh should start as a
|
---|
140 | comment without any preceding whitespaces and be followed by an appropriate
|
---|
141 | keyword - kbuild, config, usage or applet - and a colon, just like shown in the
|
---|
142 | first example above.
|
---|
143 |
|
---|
144 |
|
---|
145 | Placement / Directory
|
---|
146 | ---------------------
|
---|
147 |
|
---|
148 | Find the appropriate directory for your new applet.
|
---|
149 |
|
---|
150 | Add the kbuild snippet to the .c file:
|
---|
151 |
|
---|
152 | //kbuild:lib-$(CONFIG_MU) += mu.o
|
---|
153 |
|
---|
154 | Add the config snippet to the .c file:
|
---|
155 |
|
---|
156 | //config:config MU
|
---|
157 | //config: bool "MU"
|
---|
158 | //config: default y
|
---|
159 | //config: help
|
---|
160 | //config: Returns an indeterminate value.
|
---|
161 |
|
---|
162 |
|
---|
163 | Usage String(s)
|
---|
164 | ---------------
|
---|
165 |
|
---|
166 | Next, add usage information for your applet to the .c file.
|
---|
167 | This should look like the following:
|
---|
168 |
|
---|
169 | //usage:#define mu_trivial_usage
|
---|
170 | //usage: "[-abcde] FILE..."
|
---|
171 | //usage:#define mu_full_usage
|
---|
172 | //usage: "Returns an indeterminate value\n"
|
---|
173 | //usage: "\n -a First function"
|
---|
174 | //usage: "\n -b Second function"
|
---|
175 | //usage: ...
|
---|
176 |
|
---|
177 | If your program supports flags, the flags should be mentioned on the first
|
---|
178 | line ([-abcde]) and a detailed description of each flag should go in the
|
---|
179 | mu_full_usage section, one flag per line.
|
---|
180 |
|
---|
181 |
|
---|
182 | Header Files
|
---|
183 | ------------
|
---|
184 |
|
---|
185 | Finally add the applet declaration snippet. Be sure to read the top of
|
---|
186 | applets.src.h before adding your applet - it contains important info
|
---|
187 | on applet macros and conventions.
|
---|
188 |
|
---|
189 | //applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
|
---|
190 |
|
---|
191 |
|
---|
192 | The Grand Announcement
|
---|
193 | ----------------------
|
---|
194 |
|
---|
195 | Then create a diff by adding the new files to git (remember your libbb files)
|
---|
196 | git add <where you put it>/mu.c
|
---|
197 | eventually also:
|
---|
198 | git add libbb/function.c
|
---|
199 | then
|
---|
200 | git commit
|
---|
201 | git format-patch HEAD^
|
---|
202 | and send it to the mailing list:
|
---|
203 | busybox@busybox.net
|
---|
204 | http://busybox.net/mailman/listinfo/busybox
|
---|
205 |
|
---|
206 | Sending patches as attachments is preferred, but not required.
|
---|