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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. 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 |
21 | your applet. |
22 | Make sure to #include "libbb.h" 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 | (busybox.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 | int mu_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
45 | int mu_main(int argc, char **argv) |
46 | { |
47 | int fd; |
48 | ssize_t n; |
49 | char mu; |
50 | |
51 | fd = xopen("/dev/random", O_RDONLY); |
52 | |
53 | if ((n = safe_read(fd, &mu, 1)) < 1) |
54 | bb_perror_msg_and_die("/dev/random"); |
55 | |
56 | return mu; |
57 | } |
58 | |
59 | ----end example code------ |
60 | |
61 | |
62 | Coding Style |
63 | ------------ |
64 | |
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. |
68 | |
69 | |
70 | Some Words on libbb |
71 | ------------------- |
72 | |
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. |
75 | |
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. |
78 | |
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. |
82 | |
83 | Adding a libbb function: |
84 | ------------------------ |
85 | |
86 | Make a new file named <function_name>.c |
87 | |
88 | ----start example code------ |
89 | |
90 | #include "libbb.h" |
91 | #include "other.h" |
92 | |
93 | int function(char *a) |
94 | { |
95 | return *a; |
96 | } |
97 | |
98 | ----end example code------ |
99 | |
100 | Add <function_name>.o in the right alphabetically sorted place |
101 | in libbb/Kbuild.src. You should look at the conditional part of |
102 | libbb/Kbuild.src as well. |
103 | |
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. |
107 | |
108 | You can look at libbb/Config.src and try to find out if the function is |
109 | tunable and add it there if it is. |
110 | |
111 | |
112 | Placement / Directory |
113 | --------------------- |
114 | |
115 | Find the appropriate directory for your new applet. |
116 | |
117 | Make sure you find the appropriate places in the files, the applets are |
118 | sorted alphabetically. |
119 | |
120 | Add the applet to Kbuild.src in the chosen directory: |
121 | |
122 | lib-$(CONFIG_MU) += mu.o |
123 | |
124 | Add the applet to Config.src in the chosen directory: |
125 | |
126 | config MU |
127 | bool "MU" |
128 | default n |
129 | help |
130 | Returns an indeterminate value. |
131 | |
132 | |
133 | Usage String(s) |
134 | --------------- |
135 | |
136 | Next, add usage information for you applet to include/usage.src.h. |
137 | This should look like the following: |
138 | |
139 | #define mu_trivial_usage \ |
140 | "-[abcde] FILES" |
141 | #define mu_full_usage \ |
142 | "Returns an indeterminate value.\n\n" \ |
143 | "Options:\n" \ |
144 | "\t-a\t\tfirst function\n" \ |
145 | "\t-b\t\tsecond function\n" \ |
146 | ... |
147 | |
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.src.h.) |
152 | |
153 | |
154 | Header Files |
155 | ------------ |
156 | |
157 | Next, add an entry to include/applets.src.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: |
160 | |
161 | Be sure to read the top of applets.src.h before adding your applet. |
162 | |
163 | /* all programs above here are alphabetically "less than" 'mu' */ |
164 | IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP)) |
165 | /* all programs below here are alphabetically "greater than" 'mu' */ |
166 | |
167 | |
168 | The Grand Announcement |
169 | ---------------------- |
170 | |
171 | Then create a diff by adding the new files to git (remember your libbb files) |
172 | git add <where you put it>/mu.c |
173 | eventually also: |
174 | git add libbb/function.c |
175 | then |
176 | git commit |
177 | git format-patch HEAD^ |
178 | and send it to the mailing list: |
179 | busybox@busybox.net |
180 | http://busybox.net/mailman/listinfo/busybox |
181 | |
182 | Sending patches as attachments is preferred, but not required. |
183 |