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207 lines
5.5 KiB
Plaintext
207 lines
5.5 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 git HEAD.
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This is a good thing if you plan to getting it committed 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 and Config.in/Kbuild/usage/applet.h snippets (more on that below
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in this document). Be sure to name the main function <applet>_main instead
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of main. And be sure to put it in <applet>.c. Make sure to #include "libbb.h"
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as the first include file in your applet.
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For a new applet mu, here is the code that would go in mu.c:
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(libbb.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, see file LICENSE in this source tree.
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*/
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#include "libbb.h"
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#include "other.h"
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//config:config MU
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//config: bool "MU"
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//config: default y
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//config: help
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//config: Returns an indeterminate value.
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//kbuild:lib-$(CONFIG_MU) += mu.o
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//applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
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//usage:#define mu_trivial_usage
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//usage: "[-abcde] FILE..."
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//usage:#define mu_full_usage
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//usage: "Returns an indeterminate value\n"
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//usage: "\n -a First function"
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//usage: "\n -b Second function"
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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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//kbuild:lib-y += function.o
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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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Remember about the kbuild snippet.
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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.src and try to find out if the function is
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tunable and add it there if it is.
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Kbuild/Config.in/usage/applets.h snippets in .c files
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-----------------------------------------------------
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The old way of adding new applets was to put all the information needed by the
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configuration and build system into appropriate files (namely: Kbuild.src and
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Config.src in new applet's directory) and to add the applet declaration and
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usage info text to include/applets.src.h and include/usage.src.h respectively.
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Since the scripts/gen_build_files.sh script had been introduced, the preferred
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way is to have all these declarations contained within the applet .c files.
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Every line intended to be processed by gen_build_files.sh should start as a
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comment without any preceding whitespaces and be followed by an appropriate
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keyword - kbuild, config, usage or applet - and a colon, just like shown in the
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first example above.
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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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Add the kbuild snippet to the .c file:
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//kbuild:lib-$(CONFIG_MU) += mu.o
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Add the config snippet to the .c file:
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//config:config MU
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//config: bool "MU"
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//config: default y
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//config: help
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//config: Returns an indeterminate value.
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Usage String(s)
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---------------
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Next, add usage information for your applet to the .c file.
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This should look like the following:
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//usage:#define mu_trivial_usage
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//usage: "[-abcde] FILE..."
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//usage:#define mu_full_usage
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//usage: "Returns an indeterminate value\n"
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//usage: "\n -a First function"
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//usage: "\n -b Second function"
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//usage: ...
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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.
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Header Files
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------------
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Finally add the applet declaration snippet. Be sure to read the top of
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applets.src.h before adding your applet - it contains important info
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on applet macros and conventions.
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//applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
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The Grand Announcement
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----------------------
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Then create a diff by adding the new files to git (remember your libbb files)
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git add <where you put it>/mu.c
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eventually also:
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git add libbb/function.c
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then
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git commit
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git format-patch HEAD^
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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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