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diff --git a/docs/new-applet-HOWTO.txt b/docs/new-applet-HOWTO.txt new file mode 100644 index 0000000..1c2383f --- /dev/null +++ b/docs/new-applet-HOWTO.txt @@ -0,0 +1,150 @@ +How to Add a New Applet to BusyBox +================================== + +This document details the steps you must take to add a new applet to BusyBox. + +Credits: +Matt Kraai - initial writeup +Mark Whitley - the remix +Thomas Lundquist - Added stuff for the new directory layout. + +Initial Write +------------- + +First, write your applet. Be sure to include copyright information at the top, +such as who you stole the code from and so forth. Also include the mini-GPL +boilerplate. Be sure to name the main function <applet>_main instead of main. +And be sure to put it in <applet>.c. Usage does not have to be taken care of by +your applet. +Make sure to #include "busybox.h" as the first include file in your applet so +the bb_config.h and appropriate platform specific files are included properly. + +For a new applet mu, here is the code that would go in mu.c: + +----begin example code------ + +/* vi: set sw=4 ts=4: */ +/* + * Mini mu implementation for busybox + * + * Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL> + * + * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. + */ + +#include "busybox.h" +#include <other.h> + +int mu_main(int argc, char **argv) +{ + int fd; + char mu; + + fd = xopen("/dev/random", O_RDONLY); + + if ((n = safe_read(fd, &mu, 1)) < 1) + bb_perror_msg_and_die("/dev/random"); + + return mu; +} + +----end example code------ + + +Coding Style +------------ + +Before you submit your applet for inclusion in BusyBox, (or better yet, before +you _write_ your applet) please read through the style guide in the docs +directory and make your program compliant. + + +Some Words on libbb +------------------- + +As you are writing your applet, please be aware of the body of pre-existing +useful functions in libbb. Use these instead of reinventing the wheel. + +Additionally, if you have any useful, general-purpose functions in your +applet that could be useful in other applets, consider putting them in libbb. + + +Placement / Directory +--------------------- + +Find the appropriate directory for your new applet. + +Make sure you find the appropriate places in the files, the applets are +sorted alphabetically. + +Add the applet to Makefile.in in the chosen directory: + +obj-$(CONFIG_MU) += mu.o + +Add the applet to Config.in in the chosen directory: + +config CONFIG_MU + bool "MU" + default n + help + Returns an indeterminate value. + + +Usage String(s) +--------------- + +Next, add usage information for you applet to include/usage.h. +This should look like the following: + + #define mu_trivial_usage \ + "-[abcde] FILES" + #define mu_full_usage \ + "Returns an indeterminate value.\n\n" \ + "Options:\n" \ + "\t-a\t\tfirst function\n" \ + "\t-b\t\tsecond function\n" \ + ... + +If your program supports flags, the flags should be mentioned on the first +line (-[abcde]) and a detailed description of each flag should go in the +mu_full_usage section, one flag per line. (Numerous examples of this +currently exist in usage.h.) + + +Header Files +------------ + +Next, add an entry to include/applets.h. Be *sure* to keep the list +in alphabetical order, or else it will break the binary-search lookup +algorithm in busybox.c and the Gods of BusyBox smite you. Yea, verily: + + /* all programs above here are alphabetically "less than" 'mu' */ + #ifdef CONFIG_MU + APPLET("mu", mu_main, _BB_DIR_USR_BIN, mu_usage) + #endif + /* all programs below here are alphabetically "greater than" 'mu' */ + + +Documentation +------------- + +If you're feeling especially nice, you should also document your applet in the +docs directory (but nobody ever does that). + +Adding some text to docs/Configure.help is a nice start. + + +The Grand Announcement +---------------------- + +Then create a diff -urN of the files you added and/or modified. Typically: + <appletdir>/<applet>.c + include/usage.c + include/applets.h + <appletdir>/Makefile.in + <appletdir>/config.in +and send it to the mailing list: + busybox@busybox.net + http://busybox.net/mailman/listinfo/busybox + +Sending patches as attachments is preferred, but not required. |