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144 lines
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144 lines
4.0 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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Initial Write
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-------------
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First, write your applet. Be sure to include copyright information at the
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top, such as who you stole the code from and so forth. Also include the
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mini-GPL boilerplate. 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. For a new applet mu, here is
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the code that would go in mu.c:
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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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*
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* Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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* 02111-1307 USA
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*
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*/
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#include "busybox.h"
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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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char mu;
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if ((fd = open("/dev/random", O_RDONLY)) < 0)
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perror_msg_and_die("/dev/random");
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if ((n = safe_read(fd, &mu, 1)) < 1)
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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 utility.c
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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 utility.c. Use these instead of reinventing the wheel.
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If you use functions from utility.c, you may need to add to the preprocessor
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conditionals in that file, to make sure the routines you need are included.
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So, since your mu implementation used safe_read(), append "|| defined BB_MU" to
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the #if instruction that precedes the safe_read() function in utility.c .
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Additionally, if you have any useful, general-purpose functions in your
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program that could be useful in another program, consider putting them in
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utility.c.
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Usage String(s)
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---------------
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Next, add usage information for you applet to usage.c. This should look like
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the following:
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#if defined BB_MU
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const char mu_usage[] =
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"mu\n"
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#ifndef BB_FEATURE_TRIVIAL_HELP
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"\nReturns an indeterminate value.\n"
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#endif
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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 (mu -[bcRovma]) and a detailed description of each flag should go in the
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BB_FEATURE_TRIVIAL_HELP section, one flag per line. (Numerous examples of this
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currently exist in usage.c.)
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Header Files
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------------
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Next, add an entry to applets.h. Be *sure* to keep the list in alphabetical
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order, or else it will break the binary-search lookup algorithm in busybox.c
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and the Gods of BusyBox smite you. Yea, verily:
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/* all programs above here are alphabetically "less than" 'mu' */
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#ifdef BB_MU
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APPLET("mu", mu_main, _BB_DIR_USR_BIN, mu_usage)
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#endif
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/* all programs below here are alphabetically "greater than" 'mu' */
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Finally, add a define for your applet to Config.h:
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#define BB_MU
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Documentation
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-------------
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If you're feeling especially nice, you should also document your applet in the
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docs directory (but nobody ever does that).
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The Grand Announcement
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----------------------
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Then create a diff -urN of the files you added (<applet>.c, usage.c,
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applets.h, Config.h) and send it to the mailing list:
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busybox@opensource.lineo.com. Sending patches as attachments is preferred, but
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not required.
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