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 - Trying to keep it updated.
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10 |
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11 | When doing this you should consider using the latest git HEAD.
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12 | This is a good thing if you plan to getting it committed into mainline.
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13 |
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14 | Initial Write
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15 | -------------
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16 |
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17 | First, write your applet. Be sure to include copyright information at the top,
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18 | such as who you stole the code from and so forth. Also include the mini-GPL
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19 | boilerplate. Be sure to name the main function <applet>_main instead of main.
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20 | And be sure to put it in <applet>.c. Usage does not have to be taken care of by
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21 | your applet.
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22 | Make sure to #include "libbb.h" as the first include file in your applet.
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23 |
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24 | For a new applet mu, here is the code that would go in mu.c:
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25 |
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26 | (busybox.h already includes most usual header files. You do not need
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27 | #include <stdio.h> etc...)
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28 |
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29 |
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30 | ----begin example code------
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31 |
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32 | /* vi: set sw=4 ts=4: */
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33 | /*
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34 | * Mini mu implementation for busybox
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35 | *
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36 | * Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
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37 | *
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38 | * Licensed under GPLv2, see file LICENSE in this source tree.
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39 | */
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40 |
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41 | #include "libbb.h"
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42 | #include "other.h"
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43 |
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44 | int mu_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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45 | int mu_main(int argc, char **argv)
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46 | {
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47 | int fd;
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48 | ssize_t n;
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49 | char mu;
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50 |
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51 | fd = xopen("/dev/random", O_RDONLY);
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52 |
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53 | if ((n = safe_read(fd, &mu, 1)) < 1)
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54 | bb_perror_msg_and_die("/dev/random");
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55 |
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56 | return mu;
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57 | }
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58 |
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59 | ----end example code------
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60 |
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61 |
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62 | Coding Style
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63 | ------------
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64 |
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65 | Before you submit your applet for inclusion in BusyBox, (or better yet, before
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66 | you _write_ your applet) please read through the style guide in the docs
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67 | directory and make your program compliant.
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68 |
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69 |
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70 | Some Words on libbb
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71 | -------------------
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72 |
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73 | As you are writing your applet, please be aware of the body of pre-existing
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74 | useful functions in libbb. Use these instead of reinventing the wheel.
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75 |
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76 | Additionally, if you have any useful, general-purpose functions in your
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77 | applet that could be useful in other applets, consider putting them in libbb.
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78 |
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79 | And it may be possible that some of the other applets uses functions you
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80 | could use. If so, you have to rip the function out of the applet and make
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81 | a libbb function out of it.
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82 |
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83 | Adding a libbb function:
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84 | ------------------------
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85 |
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86 | Make a new file named <function_name>.c
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87 |
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88 | ----start example code------
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89 |
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90 | #include "libbb.h"
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91 | #include "other.h"
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92 |
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93 | int function(char *a)
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94 | {
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95 | return *a;
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96 | }
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97 |
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98 | ----end example code------
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99 |
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100 | Add <function_name>.o in the right alphabetically sorted place
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101 | in libbb/Kbuild.src. You should look at the conditional part of
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102 | libbb/Kbuild.src as well.
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103 |
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104 | You should also try to find a suitable place in include/libbb.h for
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105 | the function declaration. If not, add it somewhere anyway, with or without
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106 | ifdefs to include or not.
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107 |
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108 | You can look at libbb/Config.src and try to find out if the function is
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109 | tunable and add it there if it is.
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110 |
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111 |
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112 | Placement / Directory
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113 | ---------------------
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114 |
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115 | Find the appropriate directory for your new applet.
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116 |
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117 | Make sure you find the appropriate places in the files, the applets are
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118 | sorted alphabetically.
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119 |
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120 | Add the applet to Kbuild.src in the chosen directory:
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121 |
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122 | lib-$(CONFIG_MU) += mu.o
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123 |
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124 | Add the applet to Config.src in the chosen directory:
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125 |
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126 | config MU
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127 | bool "MU"
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128 | default n
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129 | help
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130 | Returns an indeterminate value.
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131 |
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132 |
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133 | Usage String(s)
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134 | ---------------
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135 |
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136 | Next, add usage information for you applet to include/usage.src.h.
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137 | This should look like the following:
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138 |
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139 | #define mu_trivial_usage \
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140 | "-[abcde] FILES"
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141 | #define mu_full_usage \
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142 | "Returns an indeterminate value.\n\n" \
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143 | "Options:\n" \
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144 | "\t-a\t\tfirst function\n" \
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145 | "\t-b\t\tsecond function\n" \
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146 | ...
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147 |
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148 | If your program supports flags, the flags should be mentioned on the first
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149 | line (-[abcde]) and a detailed description of each flag should go in the
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150 | mu_full_usage section, one flag per line. (Numerous examples of this
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151 | currently exist in usage.src.h.)
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152 |
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153 |
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154 | Header Files
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155 | ------------
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156 |
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157 | Next, add an entry to include/applets.src.h. Be *sure* to keep the list
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158 | in alphabetical order, or else it will break the binary-search lookup
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159 | algorithm in busybox.c and the Gods of BusyBox smite you. Yea, verily:
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160 |
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161 | Be sure to read the top of applets.src.h before adding your applet.
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162 |
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163 | /* all programs above here are alphabetically "less than" 'mu' */
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164 | IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
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165 | /* all programs below here are alphabetically "greater than" 'mu' */
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166 |
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167 |
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168 | The Grand Announcement
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169 | ----------------------
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170 |
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171 | Then create a diff by adding the new files to git (remember your libbb files)
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172 | git add <where you put it>/mu.c
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173 | eventually also:
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174 | git add libbb/function.c
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175 | then
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176 | git commit
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177 | git format-patch HEAD^
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178 | and send it to the mailing list:
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179 | busybox@busybox.net
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180 | http://busybox.net/mailman/listinfo/busybox
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181 |
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182 | Sending patches as attachments is preferred, but not required.
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