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183 lines
4.8 KiB
Plaintext
183 lines
4.8 KiB
Plaintext
How to Add a New Applet to BusyBox
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==================================
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This document details the steps you must take to add a new applet to BusyBox.
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Credits:
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Matt Kraai - initial writeup
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Mark Whitley - the remix
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Thomas Lundquist - Trying to keep it updated.
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When doing this you should consider using the latest svn trunk.
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This is a good thing if you plan to getting it commited into mainline.
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Initial Write
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-------------
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First, write your applet. Be sure to include copyright information at the top,
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such as who you stole the code from and so forth. Also include the mini-GPL
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boilerplate. Be sure to name the main function <applet>_main instead of main.
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And be sure to put it in <applet>.c. Usage does not have to be taken care of by
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your applet.
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Make sure to #include "libbb.h" as the first include file in your applet so
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the bb_config.h and appropriate platform specific files are included properly.
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For a new applet mu, here is the code that would go in mu.c:
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(busybox.h already includes most usual header files. You do not need
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#include <stdio.h> etc...)
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----begin example code------
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/* vi: set sw=4 ts=4: */
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/*
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* Mini mu implementation for busybox
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*
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* Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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*/
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#include "libbb.h"
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#include "other.h"
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int mu_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int mu_main(int argc, char **argv)
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{
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int fd;
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ssize_t n;
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char mu;
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fd = xopen("/dev/random", O_RDONLY);
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if ((n = safe_read(fd, &mu, 1)) < 1)
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bb_perror_msg_and_die("/dev/random");
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return mu;
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}
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----end example code------
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Coding Style
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------------
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Before you submit your applet for inclusion in BusyBox, (or better yet, before
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you _write_ your applet) please read through the style guide in the docs
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directory and make your program compliant.
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Some Words on libbb
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-------------------
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As you are writing your applet, please be aware of the body of pre-existing
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useful functions in libbb. Use these instead of reinventing the wheel.
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Additionally, if you have any useful, general-purpose functions in your
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applet that could be useful in other applets, consider putting them in libbb.
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And it may be possible that some of the other applets uses functions you
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could use. If so, you have to rip the function out of the applet and make
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a libbb function out of it.
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Adding a libbb function:
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------------------------
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Make a new file named <function_name>.c
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----start example code------
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#include "libbb.h"
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#include "other.h"
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int function(char *a)
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{
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return *a;
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}
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----end example code------
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Add <function_name>.o in the right alphabetically sorted place
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in libbb/Kbuild. You should look at the conditional part of
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libbb/Kbuild aswell.
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You should also try to find a suitable place in include/libbb.h for
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the function declaration. If not, add it somewhere anyway, with or without
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ifdefs to include or not.
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You can look at libbb/Config.in and try to find out if the function is
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tuneable and add it there if it is.
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Placement / Directory
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---------------------
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Find the appropriate directory for your new applet.
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Make sure you find the appropriate places in the files, the applets are
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sorted alphabetically.
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Add the applet to Kbuild in the chosen directory:
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lib-$(CONFIG_MU) += mu.o
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Add the applet to Config.in in the chosen directory:
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config MU
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bool "MU"
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default n
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help
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Returns an indeterminate value.
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Usage String(s)
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---------------
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Next, add usage information for you applet to include/usage.h.
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This should look like the following:
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#define mu_trivial_usage \
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"-[abcde] FILES"
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#define mu_full_usage \
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"Returns an indeterminate value.\n\n" \
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"Options:\n" \
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"\t-a\t\tfirst function\n" \
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"\t-b\t\tsecond function\n" \
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...
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If your program supports flags, the flags should be mentioned on the first
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line (-[abcde]) and a detailed description of each flag should go in the
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mu_full_usage section, one flag per line. (Numerous examples of this
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currently exist in usage.h.)
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Header Files
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------------
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Next, add an entry to include/applets.h. Be *sure* to keep the list
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in alphabetical order, or else it will break the binary-search lookup
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algorithm in busybox.c and the Gods of BusyBox smite you. Yea, verily:
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Be sure to read the top of applets.h before adding your applet.
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/* all programs above here are alphabetically "less than" 'mu' */
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IF_MU(APPLET(mu, _BB_DIR_USR_BIN, _BB_SUID_DROP))
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/* all programs below here are alphabetically "greater than" 'mu' */
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The Grand Announcement
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----------------------
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Then create a diff by adding the new files with svn (remember your libbb files)
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svn add <where you put it>/mu.c
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eventually also:
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svn add libbb/function.c
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then
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svn diff
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and send it to the mailing list:
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busybox@busybox.net
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http://busybox.net/mailman/listinfo/busybox
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Sending patches as attachments is preferred, but not required.
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