[821] | 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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[3621] | 9 | Thomas Lundquist - trying to keep it updated
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[821] | 10 |
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[2725] | 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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[1765] | 13 |
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[821] | 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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[3621] | 19 | boilerplate and Config.in/Kbuild/usage/applet.h snippets (more on that below
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| 20 | in this document). Be sure to name the main function <applet>_main instead
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| 21 | of main. And be sure to put it in <applet>.c. Make sure to #include "libbb.h"
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| 22 | as the first include file in your applet.
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[821] | 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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[3621] | 26 | (libbb.h already includes most usual header files. You do not need
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[1765] | 27 | #include <stdio.h> etc...)
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| 28 |
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| 29 |
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[821] | 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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[2725] | 38 | * Licensed under GPLv2, see file LICENSE in this source tree.
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[821] | 39 | */
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| 40 |
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[1765] | 41 | #include "libbb.h"
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| 42 | #include "other.h"
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[821] | 43 |
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[3621] | 44 | //config:config MU
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| 45 | //config: bool "MU"
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| 46 | //config: default y
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| 47 | //config: help
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| 48 | //config: Returns an indeterminate value.
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| 49 |
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| 50 | //kbuild:lib-$(CONFIG_MU) += mu.o
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| 51 | //applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
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| 52 |
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| 53 | //usage:#define mu_trivial_usage
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| 54 | //usage: "[-abcde] FILE..."
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| 55 | //usage:#define mu_full_usage
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| 56 | //usage: "Returns an indeterminate value\n"
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| 57 | //usage: "\n -a First function"
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| 58 | //usage: "\n -b Second function"
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| 59 |
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[2725] | 60 | int mu_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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[821] | 61 | int mu_main(int argc, char **argv)
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| 62 | {
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| 63 | int fd;
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[2725] | 64 | ssize_t n;
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[821] | 65 | char mu;
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| 66 |
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[1765] | 67 | fd = xopen("/dev/random", O_RDONLY);
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[821] | 68 |
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| 69 | if ((n = safe_read(fd, &mu, 1)) < 1)
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| 70 | bb_perror_msg_and_die("/dev/random");
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| 71 |
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| 72 | return mu;
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| 73 | }
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| 74 |
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| 75 | ----end example code------
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| 76 |
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| 77 |
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| 78 | Coding Style
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| 79 | ------------
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| 80 |
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| 81 | Before you submit your applet for inclusion in BusyBox, (or better yet, before
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| 82 | you _write_ your applet) please read through the style guide in the docs
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| 83 | directory and make your program compliant.
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| 84 |
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| 85 |
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| 86 | Some Words on libbb
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| 87 | -------------------
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| 88 |
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| 89 | As you are writing your applet, please be aware of the body of pre-existing
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| 90 | useful functions in libbb. Use these instead of reinventing the wheel.
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| 91 |
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| 92 | Additionally, if you have any useful, general-purpose functions in your
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| 93 | applet that could be useful in other applets, consider putting them in libbb.
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| 94 |
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[1765] | 95 | And it may be possible that some of the other applets uses functions you
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| 96 | could use. If so, you have to rip the function out of the applet and make
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| 97 | a libbb function out of it.
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[821] | 98 |
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[1765] | 99 | Adding a libbb function:
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| 100 | ------------------------
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| 101 |
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| 102 | Make a new file named <function_name>.c
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| 103 |
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| 104 | ----start example code------
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| 105 |
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| 106 | #include "libbb.h"
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| 107 | #include "other.h"
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| 108 |
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[3621] | 109 | //kbuild:lib-y += function.o
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| 110 |
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[1765] | 111 | int function(char *a)
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| 112 | {
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| 113 | return *a;
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| 114 | }
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| 115 |
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| 116 | ----end example code------
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| 117 |
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[3621] | 118 | Remember about the kbuild snippet.
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[1765] | 119 |
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| 120 | You should also try to find a suitable place in include/libbb.h for
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| 121 | the function declaration. If not, add it somewhere anyway, with or without
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| 122 | ifdefs to include or not.
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| 123 |
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[2725] | 124 | You can look at libbb/Config.src and try to find out if the function is
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| 125 | tunable and add it there if it is.
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[1765] | 126 |
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| 127 |
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[3621] | 128 | Kbuild/Config.in/usage/applets.h snippets in .c files
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| 129 | -----------------------------------------------------
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| 130 |
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| 131 | The old way of adding new applets was to put all the information needed by the
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| 132 | configuration and build system into appropriate files (namely: Kbuild.src and
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| 133 | Config.src in new applet's directory) and to add the applet declaration and
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| 134 | usage info text to include/applets.src.h and include/usage.src.h respectively.
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| 135 |
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| 136 | Since the scripts/gen_build_files.sh script had been introduced, the preferred
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| 137 | way is to have all these declarations contained within the applet .c files.
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| 138 |
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| 139 | Every line intended to be processed by gen_build_files.sh should start as a
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| 140 | comment without any preceding whitespaces and be followed by an appropriate
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| 141 | keyword - kbuild, config, usage or applet - and a colon, just like shown in the
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| 142 | first example above.
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| 143 |
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| 144 |
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[821] | 145 | Placement / Directory
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| 146 | ---------------------
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| 147 |
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| 148 | Find the appropriate directory for your new applet.
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| 149 |
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[3621] | 150 | Add the kbuild snippet to the .c file:
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[821] | 151 |
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[3621] | 152 | //kbuild:lib-$(CONFIG_MU) += mu.o
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[821] | 153 |
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[3621] | 154 | Add the config snippet to the .c file:
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[821] | 155 |
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[3621] | 156 | //config:config MU
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| 157 | //config: bool "MU"
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| 158 | //config: default y
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| 159 | //config: help
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| 160 | //config: Returns an indeterminate value.
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[821] | 161 |
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| 162 |
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| 163 | Usage String(s)
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| 164 | ---------------
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| 165 |
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[3621] | 166 | Next, add usage information for your applet to the .c file.
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[821] | 167 | This should look like the following:
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| 168 |
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[3621] | 169 | //usage:#define mu_trivial_usage
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| 170 | //usage: "[-abcde] FILE..."
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| 171 | //usage:#define mu_full_usage
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| 172 | //usage: "Returns an indeterminate value\n"
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| 173 | //usage: "\n -a First function"
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| 174 | //usage: "\n -b Second function"
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| 175 | //usage: ...
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[821] | 176 |
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| 177 | If your program supports flags, the flags should be mentioned on the first
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[3621] | 178 | line ([-abcde]) and a detailed description of each flag should go in the
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| 179 | mu_full_usage section, one flag per line.
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[821] | 180 |
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| 181 |
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| 182 | Header Files
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| 183 | ------------
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| 184 |
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[3621] | 185 | Finally add the applet declaration snippet. Be sure to read the top of
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| 186 | applets.src.h before adding your applet - it contains important info
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| 187 | on applet macros and conventions.
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[821] | 188 |
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[3621] | 189 | //applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
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[1765] | 190 |
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[821] | 191 |
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| 192 | The Grand Announcement
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| 193 | ----------------------
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| 194 |
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[2725] | 195 | Then create a diff by adding the new files to git (remember your libbb files)
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| 196 | git add <where you put it>/mu.c
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[1765] | 197 | eventually also:
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[2725] | 198 | git add libbb/function.c
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[1765] | 199 | then
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[2725] | 200 | git commit
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| 201 | git format-patch HEAD^
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[821] | 202 | and send it to the mailing list:
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| 203 | busybox@busybox.net
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| 204 | http://busybox.net/mailman/listinfo/busybox
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| 205 |
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| 206 | Sending patches as attachments is preferred, but not required.
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