1 | How to Add a New Applet to BusyBox
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2 | ==================================
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3 |
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4 | This document details the steps you must take to add a new applet to BusyBox.
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5 |
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6 | Credits:
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7 | Matt Kraai - initial writeup
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8 | Mark Whitley - the remix
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9 | Thomas Lundquist - Added stuff for the new directory layout.
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10 |
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11 | Initial Write
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12 | -------------
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13 |
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14 | First, write your applet. Be sure to include copyright information at the top,
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15 | such as who you stole the code from and so forth. Also include the mini-GPL
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16 | boilerplate. Be sure to name the main function <applet>_main instead of main.
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17 | And be sure to put it in <applet>.c. Usage does not have to be taken care of by
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18 | your applet.
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19 | Make sure to #include "busybox.h" as the first include file in your applet so
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20 | the bb_config.h and appropriate platform specific files are included properly.
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21 |
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22 | For a new applet mu, here is the code that would go in mu.c:
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23 |
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24 | ----begin example code------
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25 |
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26 | /* vi: set sw=4 ts=4: */
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27 | /*
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28 | * Mini mu implementation for busybox
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29 | *
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30 | * Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
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31 | *
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32 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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33 | */
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34 |
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35 | #include "busybox.h"
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36 | #include <other.h>
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37 |
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38 | int mu_main(int argc, char **argv)
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39 | {
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40 | int fd;
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41 | char mu;
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42 |
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43 | fd = bb_xopen("/dev/random", O_RDONLY);
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44 |
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45 | if ((n = safe_read(fd, &mu, 1)) < 1)
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46 | bb_perror_msg_and_die("/dev/random");
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47 |
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48 | return mu;
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49 | }
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50 |
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51 | ----end example code------
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52 |
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53 |
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54 | Coding Style
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55 | ------------
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56 |
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57 | Before you submit your applet for inclusion in BusyBox, (or better yet, before
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58 | you _write_ your applet) please read through the style guide in the docs
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59 | directory and make your program compliant.
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60 |
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61 |
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62 | Some Words on libbb
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63 | -------------------
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64 |
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65 | As you are writing your applet, please be aware of the body of pre-existing
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66 | useful functions in libbb. Use these instead of reinventing the wheel.
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67 |
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68 | Additionally, if you have any useful, general-purpose functions in your
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69 | applet that could be useful in other applets, consider putting them in libbb.
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70 |
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71 |
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72 | Placement / Directory
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73 | ---------------------
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74 |
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75 | Find the appropriate directory for your new applet.
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76 |
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77 | Make sure you find the appropriate places in the files, the applets are
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78 | sorted alphabetically.
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79 |
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80 | Add the applet to Makefile.in in the chosen directory:
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81 |
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82 | obj-$(CONFIG_MU) += mu.o
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83 |
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84 | Add the applet to Config.in in the chosen directory:
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85 |
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86 | config CONFIG_MU
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87 | bool "MU"
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88 | default n
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89 | help
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90 | Returns an indeterminate value.
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91 |
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92 |
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93 | Usage String(s)
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94 | ---------------
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95 |
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96 | Next, add usage information for you applet to include/usage.h.
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97 | This should look like the following:
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98 |
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99 | #define mu_trivial_usage \
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100 | "-[abcde] FILES"
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101 | #define mu_full_usage \
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102 | "Returns an indeterminate value.\n\n" \
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103 | "Options:\n" \
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104 | "\t-a\t\tfirst function\n" \
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105 | "\t-b\t\tsecond function\n" \
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106 | ...
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107 |
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108 | If your program supports flags, the flags should be mentioned on the first
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109 | line (-[abcde]) and a detailed description of each flag should go in the
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110 | mu_full_usage section, one flag per line. (Numerous examples of this
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111 | currently exist in usage.h.)
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112 |
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113 |
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114 | Header Files
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115 | ------------
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116 |
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117 | Next, add an entry to include/applets.h. Be *sure* to keep the list
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118 | in alphabetical order, or else it will break the binary-search lookup
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119 | algorithm in busybox.c and the Gods of BusyBox smite you. Yea, verily:
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120 |
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121 | /* all programs above here are alphabetically "less than" 'mu' */
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122 | #ifdef CONFIG_MU
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123 | APPLET("mu", mu_main, _BB_DIR_USR_BIN, mu_usage)
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124 | #endif
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125 | /* all programs below here are alphabetically "greater than" 'mu' */
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126 |
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127 |
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128 | Documentation
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129 | -------------
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130 |
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131 | If you're feeling especially nice, you should also document your applet in the
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132 | docs directory (but nobody ever does that).
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133 |
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134 | Adding some text to docs/Configure.help is a nice start.
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135 |
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136 |
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137 | The Grand Announcement
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138 | ----------------------
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139 |
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140 | Then create a diff -urN of the files you added and/or modified. Typically:
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141 | <appletdir>/<applet>.c
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142 | include/usage.c
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143 | include/applets.h
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144 | <appletdir>/Makefile.in
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145 | <appletdir>/config.in
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146 | and send it to the mailing list:
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147 | busybox@busybox.net
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148 | http://busybox.net/mailman/listinfo/busybox
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149 |
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150 | Sending patches as attachments is preferred, but not required.
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