Credits:
Matt Kraai - initial writeup
Mark Whitley - the remix
-Thomas Lundquist - Added stuff for the new directory layout.
+Thomas Lundquist - trying to keep it updated
+
+When doing this you should consider using the latest git HEAD.
+This is a good thing if you plan to getting it committed into mainline.
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 do not have to be taken care of by your applet.
+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 and Config.in/Kbuild/usage/applet.h snippets (more on that below
+in this document). Be sure to name the main function <applet>_main instead
+of main. And be sure to put it in <applet>.c. Make sure to #include "libbb.h"
+as the first include file in your applet.
For a new applet mu, here is the code that would go in mu.c:
+(libbb.h already includes most usual header files. You do not need
+#include <stdio.h> etc...)
+
+
----begin example code------
/* vi: set sw=4 ts=4: */
/*
* Mini mu implementation for busybox
*
- *
* Copyright (C) [YEAR] by [YOUR NAME] <YOUR EMAIL>
*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
- * 02111-1307 USA
- *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
*/
-#include "busybox.h"
+#include "libbb.h"
+#include "other.h"
+
+//config:config MU
+//config: bool "MU"
+//config: default y
+//config: help
+//config: Returns an indeterminate value.
+
+//kbuild:lib-$(CONFIG_MU) += mu.o
+//applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//usage:#define mu_trivial_usage
+//usage: "[-abcde] FILE..."
+//usage:#define mu_full_usage
+//usage: "Returns an indeterminate value\n"
+//usage: "\n -a First function"
+//usage: "\n -b Second function"
+int mu_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mu_main(int argc, char **argv)
{
int fd;
+ ssize_t n;
char mu;
- if ((fd = open("/dev/random", O_RDONLY)) < 0)
- bb_perror_msg_and_die("/dev/random");
+ fd = xopen("/dev/random", O_RDONLY);
if ((n = safe_read(fd, &mu, 1)) < 1)
bb_perror_msg_and_die("/dev/random");
useful functions in libbb. Use these instead of reinventing the wheel.
Additionally, if you have any useful, general-purpose functions in your
-program that could be useful in another program, consider putting them in
-libbb.
+applet that could be useful in other applets, consider putting them in libbb.
+
+And it may be possible that some of the other applets uses functions you
+could use. If so, you have to rip the function out of the applet and make
+a libbb function out of it.
+
+Adding a libbb function:
+------------------------
+
+Make a new file named <function_name>.c
+
+----start example code------
+
+#include "libbb.h"
+#include "other.h"
+
+//kbuild:lib-y += function.o
+
+int function(char *a)
+{
+ return *a;
+}
+
+----end example code------
+
+Remember about the kbuild snippet.
+
+You should also try to find a suitable place in include/libbb.h for
+the function declaration. If not, add it somewhere anyway, with or without
+ifdefs to include or not.
+
+You can look at libbb/Config.src and try to find out if the function is
+tunable and add it there if it is.
+
+
+Kbuild/Config.in/usage/applets.h snippets in .c files
+-----------------------------------------------------
+
+The old way of adding new applets was to put all the information needed by the
+configuration and build system into appropriate files (namely: Kbuild.src and
+Config.src in new applet's directory) and to add the applet declaration and
+usage info text to include/applets.src.h and include/usage.src.h respectively.
+
+Since the scripts/gen_build_files.sh script had been introduced, the preferred
+way is to have all these declarations contained within the applet .c files.
+
+Every line intended to be processed by gen_build_files.sh should start as a
+comment without any preceding whitespaces and be followed by an appropriate
+keyword - kbuild, config, usage or applet - and a colon, just like shown in the
+first example above.
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 applet directory:
+Add the kbuild snippet to the .c file:
-obj-$(CONFIG_MU) += mu.o
+//kbuild:lib-$(CONFIG_MU) += mu.o
-Add the applet to Config.in in the chosen applet directory:
+Add the config snippet to the .c file:
-config CONFIG_MU
- bool "MU"
- default n
- help
- Returns an indeterminate value.
+//config:config MU
+//config: bool "MU"
+//config: default y
+//config: help
+//config: Returns an indeterminate value.
Usage String(s)
---------------
-Next, add usage information for you applet to include/usage.h.
+Next, add usage information for your applet to the .c file.
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" \
+//usage:#define mu_trivial_usage
+//usage: "[-abcde] FILE..."
+//usage:#define mu_full_usage
+//usage: "Returns an indeterminate value\n"
+//usage: "\n -a First function"
+//usage: "\n -b Second function"
+//usage: ...
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.)
+line ([-abcde]) and a detailed description of each flag should go in the
+mu_full_usage section, one flag per line.
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:
+Finally add the applet declaration snippet. Be sure to read the top of
+applets.src.h before adding your applet - it contains important info
+on applet macros and conventions.
- /* 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.
+//applet:IF_MU(APPLET(mu, BB_DIR_USR_BIN, BB_SUID_DROP))
The Grand Announcement
----------------------
-Then create a diff -urN of the files you added (<appletdir/><applet>.c,
-include/usage.c, include/applets.h, include/config.h, <appletdir>/Makefile.in, <appletdir>/config.in)
+Then create a diff by adding the new files to git (remember your libbb files)
+ git add <where you put it>/mu.c
+eventually also:
+ git add libbb/function.c
+then
+ git commit
+ git format-patch HEAD^
and send it to the mailing list:
-busybox@busybox.net.
+ busybox@busybox.net
+ http://busybox.net/mailman/listinfo/busybox
Sending patches as attachments is preferred, but not required.
-
projects / oweals / busybox.git / blobdiff