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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 | |||
10 | |||
11 | Initial Write | ||
12 | ------------- | ||
13 | |||
14 | First, write your applet. Be sure to include copyright information at the | ||
15 | top, such as who you stole the code from and so forth. Also include the | ||
16 | mini-GPL boilerplate. Be sure to name the main function <applet>_main instead | ||
17 | of main. And be sure to put it in <applet>.c. For a new applet mu, here is | ||
18 | the code that would go in mu.c: | ||
19 | |||
20 | ----begin example code------ | ||
21 | |||
22 | /* vi: set sw=4 ts=4: */ | ||
23 | /* | ||
24 | * Mini mu implementation for busybox | ||
25 | * | ||
26 | * | ||
27 | * Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL> | ||
28 | * | ||
29 | * This program is free software; you can redistribute it and/or modify | ||
30 | * it under the terms of the GNU General Public License as published by | ||
31 | * the Free Software Foundation; either version 2 of the License, or | ||
32 | * (at your option) any later version. | ||
33 | * | ||
34 | * This program is distributed in the hope that it will be useful, | ||
35 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
36 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
37 | * General Public License for more details. | ||
38 | * | ||
39 | * You should have received a copy of the GNU General Public License | ||
40 | * along with this program; if not, write to the Free Software | ||
41 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | ||
42 | * 02111-1307 USA | ||
43 | * | ||
44 | */ | ||
45 | |||
46 | #include "busybox.h" | ||
47 | |||
48 | int mu_main(int argc, char **argv) | ||
49 | { | ||
50 | int fd; | ||
51 | char mu; | ||
52 | |||
53 | if ((fd = open("/dev/random", O_RDONLY)) < 0) | ||
54 | perror_msg_and_die("/dev/random"); | ||
55 | |||
56 | if ((n = safe_read(fd, &mu, 1)) < 1) | ||
57 | perror_msg_and_die("/dev/random"); | ||
58 | |||
59 | return mu; | ||
60 | } | ||
61 | |||
62 | ----end example code------ | ||
63 | |||
64 | As you are writing your applet, please be aware of the body of pre-existing | ||
65 | useful functions in utility.c. Use these instead of reinventing the wheel. | ||
66 | Additionally, if you have any useful, general-purpose functions in your | ||
67 | program that could be useful in another program, consider putting them in | ||
68 | utility.c. | ||
69 | |||
70 | Furthermore, please read through the style guide in the docs directory and | ||
71 | make your program compliant. | ||
72 | |||
73 | |||
74 | Usage String(s) | ||
75 | --------------- | ||
76 | |||
77 | Next, add usage information for you applet to usage.c. This should look like | ||
78 | the following: | ||
79 | |||
80 | #if defined BB_MU | ||
81 | const char mu_usage[] = | ||
82 | "mu\n" | ||
83 | #ifndef BB_FEATURE_TRIVIAL_HELP | ||
84 | "\nReturns an indeterminate value.\n" | ||
85 | #endif | ||
86 | ; | ||
87 | |||
88 | If your program supports flags, the flags should be mentioned on the first | ||
89 | line (mu -[bcRovma]) and a detailed description of each flag should go in the | ||
90 | BB_FEATURE_TRIVIAL_HELP section, one flag per line. (Numerous examples of this | ||
91 | currently exist in utility.c.) | ||
92 | |||
93 | |||
94 | Header Files | ||
95 | ------------ | ||
96 | |||
97 | Next, add an entry to applets.h. Be *sure* to keep the list in alphabetical | ||
98 | order, or else it will break the binary-search lookup algorithm in busybox.c | ||
99 | and the Gods of BusyBox smite you. Yea, verily: | ||
100 | |||
101 | /* all programs above here are alphabetically "less than" 'mu' */ | ||
102 | #ifdef BB_MU | ||
103 | APPLET("mu", mu_main, _BB_DIR_USR_BIN, mu_usage) | ||
104 | #endif | ||
105 | /* all programs below here are alphabetically "greater than" 'mu' */ | ||
106 | |||
107 | |||
108 | Finally, add a define for your applet to Config.h: | ||
109 | |||
110 | #define BB_MU | ||
111 | |||
112 | |||
113 | Documentation | ||
114 | ------------- | ||
115 | |||
116 | If you're feeling especially nice, you should also document your applet in the | ||
117 | docs directory (but nobody ever does that). | ||
118 | |||
119 | |||
120 | The Grand Announcement | ||
121 | ---------------------- | ||
122 | |||
123 | Then create a diff -urN of the files you added (<applet>.c, usage.c, | ||
124 | applets.h, Config.h) and send it to the mailing list: | ||
125 | busybox@opensource.lineo.com. Sending patches as attachments is preferred, but | ||
126 | not required. | ||
127 | |||
128 | |||