1 <html><head><title>toybox source code walkthrough</title></head>
2 <!--#include file="header.html" -->
4 <p><h1><a name="style" /><a href="#style">Code style</a></h1></p>
6 <p>The primary goal of toybox is _simple_ code. Keeping the code small is
7 second, with speed and lots of features coming in somewhere after that.
8 (For more on that, see the <a href=design.html>design</a> page.)</p>
10 <p>A simple implementation usually takes up fewer lines of source code,
11 meaning more code can fit on the screen at once, meaning the programmer can
12 see more of it on the screen and thus keep more if in their head at once.
13 This helps code auditing and thus reduces bugs. That said, sometimes being
14 more explicit is preferable to being clever enough to outsmart yourself:
15 don't be so terse your code is unreadable.</p>
17 <p>Toybox has an actual coding style guide over on
18 <a href=design.html#codestyle>the design page</a>, but in general we just
19 want the code to be consistent.</p>
21 <p><h1><a name="building" /><a href="#building">Building Toybox</a></h1></p>
23 <p>Toybox is configured using the Kconfig language pioneered by the Linux
24 kernel, and adopted by many other projects (uClibc, OpenEmbedded, etc).
25 This generates a ".config" file containing the selected options, which
26 controls which features are included when compiling toybox.</p>
28 <p>Each configuration option has a default value. The defaults indicate the
29 "maximum sane configuration", I.E. if the feature defaults to "n" then it
30 either isn't complete or is a special-purpose option (such as debugging
31 code) that isn't intended for general purpose use.</p>
33 <p>For a more compact human-editable version .config files, you can use the
34 <a href=http://landley.net/aboriginal/FAQ.html#dev_miniconfig>miniconfig</a>
37 <p>The standard build invocation is:</p>
40 <li>make defconfig #(or menuconfig)</li>
45 <p>Type "make help" to see all available build options.</p>
47 <p>The file "configure" contains a number of environment variable definitions
48 which influence the build, such as specifying which compiler to use or where
49 to install the resulting binaries. This file is included by the build, but
50 accepts existing definitions of the environment variables, so it may be sourced
51 or modified by the developer before building and the definitions exported
52 to the environment will take precedence.</p>
54 <p>(To clarify: ".config" lists the features selected by defconfig/menuconfig,
55 I.E. "what to build", and "configure" describes the build and installation
56 environment, I.E. "how to build it".)</p>
58 <p>By default "make install" puts files in /usr/toybox. Adding this to the
59 $PATH is up to you. The environment variable $PREFIX can change the
60 install location, ala "PREFIX=/usr/local/bin make install".</p>
62 <p>If you need an unstripped (debug) version of any of these binaries,
63 look in generated/unstripped.</p>
65 <p><h1><a name="running"><a href="#running">Running a command</a></h1></p>
69 <p>The toybox main() function is at the end of main.c at the top level. It has
70 two possible codepaths, only one of which is configured into any given build
73 <p>If CONFIG_SINGLE is selected, toybox is configured to contain only a single
74 command, so most of the normal setup can be skipped. In this case the
75 multiplexer isn't used, instead main() calls toy_singleinit() (also in main.c)
76 to set up global state and parse command line arguments, calls the command's
77 main function out of toy_list (in the CONFIG_SINGLE case the array has a single entry, no need to search), and if the function returns instead of exiting
78 it flushes stdout (detecting error) and returns toys.exitval.</p>
80 <p>When CONFIG_SINGLE is not selected, main() uses basename() to find the
81 name it was run as, shifts its argument list one to the right so it lines up
82 with where the multiplexer function expects it, and calls toybox_main(). This
83 leverages the multiplexer command's infrastructure to find and run the
84 appropriate command. (A command name starting with "toybox" will
85 recursively call toybox_main(); you can go "./toybox toybox toybox toybox ls"
86 if you want to...)</p>
90 <p>The toybox_main() function is also in main,c. It handles a possible
91 --help option ("toybox --help ls"), prints the list of available commands if no
92 arguments were provided to the multiplexer (or with full path names if any
93 other option is provided before a command name, ala "toybox --list").
94 Otherwise it calls toy_exec() on its argument list.</p>
96 <p>Note that the multiplexer is the first entry in toy_list (the rest of the
97 list is sorted alphabetically to allow binary search), so toybox_main can
98 cheat and just grab the first entry to quickly set up its context without
99 searching. Since all command names go through the multiplexer at least once
100 in the non-TOYBOX_SINGLE case, this avoids a redundant search of
103 <p>The toy_exec() function is also in main.c. It performs toy_find() to
104 perform a binary search on the toy_list array to look up the command's
105 entry by name and saves it in the global variable which, calls toy_init()
106 to parse command line arguments and set up global state (using which->options),
107 and calls the appropriate command's main() function (which->toy_main). On
108 return it flushes all pending ansi FILE * I/O, detects if stdout had an
109 error, and then calls xexit() (which uses toys.exitval).</p>
111 <p><h1><a name="infrastructure" /><a href="#infrastructure">Infrastructure</a></h1></p>
113 <p>The toybox source code is in following directories:</p>
115 <li>The <a href="#top">top level directory</a> contains the file main.c (were
116 execution starts), the header file toys.h (included by every command), and
117 other global infrastructure.</li>
118 <li>The <a href="#lib">lib directory</a> contains common functions shared by
119 multiple commands:</li>
121 <li><a href="#lib_lib">lib/lib.c</a></li>
122 <li><a href="#lib_xwrap">lib/xwrap.c</a></li>
123 <li><a href="#lib_llist">lib/llist.c</a></li>
124 <li><a href="#lib_args">lib/args.c</a></li>
125 <li><a href="#lib_dirtree">lib/dirtree.c</a></li>
127 <li>The <a href="#toys">toys directory</a> contains the C files implementating
128 each command. Currently it contains five subdirectories categorizing the
129 commands: posix, lsb, other, example, and pending.</li>
130 <li>The <a href="#scripts">scripts directory</a> contains the build and
131 test infrastructure.</li>
132 <li>The <a href="#kconfig">kconfig directory</a> contains the configuration
133 infrastructure implementing menuconfig (copied from the Linux kernel).</li>
134 <li>The <a href="#generated">generated directory</a> contains intermediate
135 files generated from other parts of the source code.</li>
139 <p><h1><a href="#adding">Adding a new command</a></h1></p>
140 <p>To add a new command to toybox, add a C file implementing that command to
141 one of the subdirectories under the toys directory. No other files need to
142 be modified; the build extracts all the information it needs (such as command
143 line arguments) from specially formatted comments and macros in the C file.
144 (See the description of the <a href="#generated">"generated" directory</a>
147 <p>Currently there are five subdirectories under "toys", one for commands
148 defined by the POSIX standard, one for commands defined by the Linux Standard
149 Base, an "other" directory for commands not covered by an obvious standard,
150 a directory of example commands (templates to use when starting new commands),
151 and a "pending" directory of commands that need further review/cleanup
152 before moving to one of the other directories (run these at your own risk,
153 cleanup patches welcome).
154 These directories are just for developer convenience sorting the commands,
155 the directories are otherwise functionally identical. To add a new category,
156 create the appropriate directory with a README file in it whose first line
157 is the description menuconfig should use for the directory.)</p>
159 <p>An easy way to start a new command is copy the file "toys/example/hello.c"
160 to the name of the new command, and modify this copy to implement the new
161 command (more or less by turning every instance of "hello" into the
162 name of your command, updating the command line arguments, globals, and
163 help data, and then filling out its "main" function with code that does
164 something interesting).</p>
166 <p>You could also start with "toys/example/skeleton.c", which provides a lot
167 more example code (showing several variants of command line option
168 parsing, how to implement multiple commands in the same file, and so on).
169 But usually it's just more stuff to delete.</p>
171 <p>Here's a checklist of steps to turn hello.c into another command:</p>
174 <li><p>First "cp toys/example/hello.c toys/other/yourcommand.c" and open
175 the new file in your preferred text editor.</p>
176 <ul><li><p>Note that the
177 name of the new file is significant: it's the name of the new command you're
178 adding to toybox. The build includes all *.c files under toys/*/ whose
179 names are a case insensitive match for an enabled config symbol. So
180 toys/posix/cat.c only gets included if you have "CAT=y" in ".config".</p></li>
183 <li><p>Change the one line comment at the top of the file (currently
184 "hello.c - A hello world program") to describe your new file.</p></li>
186 <li><p>Change the copyright notice to your name, email, and the current
189 <li><p>Give a URL to the relevant standards document, where applicable.
190 (Sample links to SUSv4 and LSB are provided, feel free to link to other
191 documentation or standards as appropriate.)</p></li>
193 <li><p>Update the USE_YOURCOMMAND(NEWTOY(yourcommand,"blah",0)) line.
194 The NEWTOY macro fills out this command's <a href="#toy_list">toy_list</a>
195 structure. The arguments to the NEWTOY macro are:</p>
198 <li><p>the name used to run your command</p></li>
199 <li><p>the command line argument <a href="#lib_args">option parsing string</a> (0 if none)</p></li>
200 <li><p>a bitfield of TOYFLAG values
201 (defined in toys.h) providing additional information such as where your
202 command should be installed on a running system, whether to blank umask
203 before running, whether or not the command must run as root (and thus should
204 retain root access if installed SUID), and so on.</p></li>
208 <li><p>Change the kconfig data (from "config YOURCOMMAND" to the end of the
209 comment block) to supply your command's configuration and help
210 information. The uppper case config symbols are used by menuconfig, and are
211 also what the CFG_ and USE_() macros are generated from (see [TODO]). The
212 help information here is used by menuconfig, and also by the "help" command to
213 describe your new command. (See [TODO] for details.) By convention,
214 unfinished commands default to "n" and finished commands default to "y",
215 so "make defconfig" selects all finished commands. (Note, "finished" means
216 "ready to be used", not that it'll never change again.)<p>
218 <p>Each help block should start with a "usage: yourcommand" line explaining
219 any command line arguments added by this config option. The "help" command
220 outputs this text, and scripts/config2help.c in the build infrastructure
221 collates these usage lines for commands with multiple configuration
222 options when producing generated/help.h.</p>
225 <li><p>Change the "#define FOR_hello" line to "#define FOR_yourcommand" right
226 before the "#include <toys.h>". (This selects the appropriate FLAG_ macros and
227 does a "#define TT this.yourcommand" so you can access the global variables
228 out of the space-saving union of structures. If you aren't using any command
229 flag bits and aren't defining a GLOBAL block, you can delete this line.)</p></li>
231 <li><p>Update the GLOBALS() macro to contain your command's global
232 variables. If your command has no global variables, delete this macro.</p>
234 <p>Variables in the GLOBALS() block are are stored in a space saving
235 <a href="#toy_union">union of structures</a> format, which may be accessed
236 using the TT macro as if TT were a global structure (so TT.membername).
237 If you specified two-character command line arguments in
238 NEWTOY(), the first few global variables will be initialized by the automatic
239 argument parsing logic, and the type and order of these variables must
240 correspond to the arguments specified in NEWTOY().
241 (See <a href="#lib_args">lib/args.c</a> for details.)</p></li>
243 <li><p>Rename hello_main() to yourcommand_main(). This is the main() function
244 where execution of your command starts. Your command line options are
245 already sorted into this.optflags, this.optargs, this.optc, and the GLOBALS()
246 as appropriate by the time this function is called. (See
247 <a href="#lib_args">get_optflags()</a> for details.)</p></li>
249 <li><p>Switch on TOYBOX_DEBUG in menuconfig (toybox global settings menu)
250 the first time you build and run your new command. If anything is wrong
251 with your option string, that will give you error messages.</p>
253 <p>Otherwise it'll just segfault without
254 explanation when it falls off the end because it didn't find a matching
255 end parantheses for a longopt, or you put a nonexistent option in a square
256 bracket grouping... Since these kind of errors can only be caused by a
257 developer, not by end users, we don't normally want runtime checks for
258 them. Once you're happy with your option string, you can switch TOYBOX_DEBUG
262 <a name="headers" /><h2><a href="#headers">Headers.</a></h2>
264 <p>Commands generally don't have their own headers. If it's common code
265 it can live in lib/, if it isn't put it in the command's .c file. (The line
266 between implementing multiple commands in a C file via OLDTOY() to share
267 infrastructure and moving that shared infrastructure to lib/ is a judgement
268 call. Try to figure out which is simplest.)</p>
270 <p>The top level toys.h should #include all the standard (posix) headers
271 that any command uses. (Partly this is friendly to ccache and partly this
272 makes the command implementations shorter.) Individual commands should only
273 need to include nonstandard headers that might prevent that command from
274 building in some context we'd care about (and thus requiring that command to
275 be disabled to avoid a build break).</p>
277 <p>Target-specific stuff (differences between compiler versions, libc versions,
278 or operating systems) should be confined to lib/portability.h and
279 lib/portability.c. (There's even some minimal compile-time environment probing
280 that writes data to generated/portability.h, see scripts/genconfig.sh.)</p>
282 <p>Only include linux/*.h headers from individual commands (not from other
283 headers), and only if you really need to. Data that varies per architecture
284 is a good reason to include a header. If you just need a couple constants
285 that haven't changed since the 1990's, it's ok to #define them yourself or
286 just use the constant inline with a comment explaining what it is. (A
287 #define that's only used once isn't really helping.)</p>
289 <p><a name="top" /><h1><a href="#top">Top level directory.</a></h1></p>
291 <p>This directory contains global infrastructure.</p>
294 <p>Each command #includes "toys.h" as part of its standard prolog. It
295 may "#define FOR_commandname" before doing so to get some extra entries
296 specific to this command.</p>
298 <p>This file sucks in most of the commonly used standard #includes, so
299 individual files can just #include "toys.h" and not have to worry about
300 stdargs.h and so on. Individual commands still need to #include
301 special-purpose headers that may not be present on all systems (and thus would
302 prevent toybox from building that command on such a system with that command
303 enabled). Examples include regex support, any "linux/" or "asm/" headers, mtab
304 support (mntent.h and sys/mount.h), and so on.</p>
306 <p>The toys.h header also defines structures for most of the global variables
307 provided to each command by toybox_main(). These are described in
308 detail in the description for main.c, where they are initialized.</p>
310 <p>The global variables are grouped into structures (and a union) for space
311 savings, to more easily track the amount of memory consumed by them,
312 so that they may be automatically cleared/initialized as needed, and so
313 that access to global variables is more easily distinguished from access to
317 <p>Contains the main() function where execution starts, plus
318 common infrastructure to initialize global variables and select which command
319 to run. The "toybox" multiplexer command also lives here. (This is the
320 only command defined outside of the toys directory.)</p>
322 <p>Execution starts in main() which trims any path off of the first command
323 name and calls toybox_main(), which calls toy_exec(), which calls toy_find()
324 and toy_init() before calling the appropriate command's function from
325 toy_list[] (via toys.which->toy_main()).
326 If the command is "toybox", execution recurses into toybox_main(), otherwise
327 the call goes to the appropriate commandname_main() from a C file in the toys
330 <p>The following global variables are defined in main.c:</p>
332 <a name="toy_list" />
333 <li><p><b>struct toy_list toy_list[]</b> - array describing all the
334 commands currently configured into toybox. The first entry (toy_list[0]) is
335 for the "toybox" multiplexer command, which runs all the other built-in commands
336 without symlinks by using its first argument as the name of the command to
337 run and the rest as that command's argument list (ala "./toybox echo hello").
338 The remaining entries are the commands in alphabetical order (for efficient
341 <p>This is a read-only array initialized at compile time by
342 defining macros and #including generated/newtoys.h.</p>
344 <p>Members of struct toy_list (defined in "toys.h") include:</p>
346 <li><p>char *<b>name</b> - the name of this command.</p></li>
347 <li><p>void (*<b>toy_main</b>)(void) - function pointer to run this
349 <li><p>char *<b>options</b> - command line option string (used by
350 get_optflags() in lib/args.c to intialize toys.optflags, toys.optargs, and
351 entries in the toy's GLOBALS struct). When this is NULL, no option
352 parsing is done before calling toy_main().</p></li>
353 <li><p>int <b>flags</b> - Behavior flags for this command. The following flags are currently understood:</p>
356 <li><b>TOYFLAG_USR</b> - Install this command under /usr</li>
357 <li><b>TOYFLAG_BIN</b> - Install this command under /bin</li>
358 <li><b>TOYFLAG_SBIN</b> - Install this command under /sbin</li>
359 <li><b>TOYFLAG_NOFORK</b> - This command can be used as a shell builtin.</li>
360 <li><b>TOYFLAG_UMASK</b> - Call umask(0) before running this command.</li>
361 <li><b>TOYFLAG_STAYROOT</b> - Don't drop permissions for this command if toybox is installed SUID root.</li>
362 <li><b>TOYFLAG_NEEDROOT</b> - This command cannot function unless run with root access.</li>
366 <p>These flags are combined with | (or). For example, to install a command
367 in /usr/bin, or together TOYFLAG_USR|TOYFLAG_BIN.</p>
371 <li><p><b>struct toy_context toys</b> - global structure containing information
372 common to all commands, initializd by toy_init() and defined in "toys.h".
373 Members of this structure include:</p>
375 <li><p>struct toy_list *<b>which</b> - a pointer to this command's toy_list
376 structure. Mostly used to grab the name of the running command
377 (toys->which.name).</p>
379 <li><p>int <b>exitval</b> - Exit value of this command. Defaults to zero. The
380 error_exit() functions will return 1 if this is zero, otherwise they'll
381 return this value.</p></li>
382 <li><p>char **<b>argv</b> - "raw" command line options, I.E. the original
383 unmodified string array passed in to main(). Note that modifying this changes
384 "ps" output, and is not recommended. This array is null terminated; a NULL
385 entry indicates the end of the array.</p>
386 <p>Most commands don't use this field, instead the use optargs, optflags,
387 and the fields in the GLOBALS struct initialized by get_optflags().</p>
389 <li><p>unsigned <b>optflags</b> - Command line option flags, set by
390 <a href="#lib_args">get_optflags()</a>. Indicates which of the command line options listed in
391 toys->which.options occurred this time.</p>
393 <p>The rightmost command line argument listed in toys->which.options sets bit
394 1, the next one sets bit 2, and so on. This means the bits are set in the same
395 order the binary digits would be listed if typed out as a string. For example,
396 the option string "abcd" would parse the command line "-c" to set optflags to 2,
397 "-a" would set optflags to 8, and "-bd" would set optflags to 6 (4|2).</p>
399 <p>Only letters are relevant to optflags. In the string "a*b:c#d", d=1, c=2,
400 b=4, a=8. Punctuation after a letter initializes global variables at the
401 start of the GLOBALS() block (see <a href="#toy_union">union toy_union this</a>
404 <p>The build infrastructure creates FLAG_ macros for each option letter,
405 corresponding to the bit position, so you can check (toys.optflags & FLAG_x)
406 to see if a flag was specified. (The correct set of FLAG_ macros is selected
407 by defining FOR_mycommand before #including toys.h. The macros live in
408 toys/globals.h which is generated by scripts/make.sh.)</p>
410 <p>For more information on option parsing, see <a href="#lib_args">get_optflags()</a>.</p>
413 <li><p>char **<b>optargs</b> - Null terminated array of arguments left over
414 after get_optflags() removed all the ones it understood. Note: optarg[0] is
415 the first argument, not the command name. Use toys.which->name for the command
417 <li><p>int <b>optc</b> - Optarg count, equivalent to argc but for
421 <a name="toy_union" />
422 <li><p><b>union toy_union this</b> - Union of structures containing each
423 command's global variables.</p>
425 <p>Global variables are useful: they reduce the overhead of passing extra
426 command line arguments between functions, they conveniently start prezeroed to
427 save initialization costs, and the command line argument parsing infrastructure
428 can also initialize global variables with its results.</p>
430 <p>But since each toybox process can only run one command at a time, allocating
431 space for global variables belonging to other commands you aren't currently
432 running would be wasteful.</p>
434 <p>Toybox handles this by encapsulating each command's global variables in
435 a structure, and declaring a union of those structures with a single global
436 instance (called "this"). The GLOBALS() macro contains the global
437 variables that should go in the current command's global structure. Each
438 variable can then be accessed as "this.commandname.varname".
439 If you #defined FOR_commandname before including toys.h, the macro TT is
440 #defined to this.commandname so the variable can then be accessed as
441 "TT.variable". See toys/hello.c for an example.</p>
443 <p>A command that needs global variables should declare a structure to
444 contain them all, and add that structure to this union. A command should never
445 declare global variables outside of this, because such global variables would
446 allocate memory when running other commands that don't use those global
449 <p>The first few fields of this structure can be intialized by <a href="#lib_args">get_optargs()</a>,
450 as specified by the options field off this command's toy_list entry. See
451 the get_optargs() description in lib/args.c for details.</p>
454 <li><b>char toybuf[4096]</b> - a common scratch space buffer guaranteed
455 to start zeroed, so commands don't need to allocate/initialize their own.
456 Any command is free to use this, and it should never be directly referenced
457 by functions in lib/ (although commands are free to pass toybuf in to a
458 library function as an argument).</li>
460 <li><b>char libbuf[4096]</b> - like toybuf, but for use by common code in
461 lib/*.c. Commands should never directly reference libbuf, and library
462 could should nnever directly reference toybuf.</li>
465 <p>The following functions are defined in main.c:</p>
467 <li><p>struct toy_list *<b>toy_find</b>(char *name) - Return the toy_list
468 structure for this command name, or NULL if not found.</p></li>
469 <li><p>void <b>toy_init</b>(struct toy_list *which, char *argv[]) - fill out
470 the global toys structure, calling get_optargs() if necessary.</p></li>
471 <li><p>void <b>toy_exec</b>(char *argv[]) - Run a built-in command with
473 <p>Calls toy_find() on argv[0] (which must be just a command name
474 without path). Returns if it can't find this command, otherwise calls
475 toy_init(), toys->which.toy_main(), and exit() instead of returning.</p>
477 <p>Use the library function xexec() to fall back to external executables
478 in $PATH if toy_exec() can't find a built-in command. Note that toy_exec()
479 does not strip paths before searching for a command, so "./command" will
480 never match an internal command.</li>
482 <li><p>void <b>toybox_main</b>(void) - the main function for the multiplexer
483 command (I.E. "toybox"). Given a command name as its first argument, calls
484 toy_exec() on its arguments. With no arguments, it lists available commands.
485 If the first argument starts with "-" it lists each command with its default
486 install path prepended.</p></li>
492 <p>Top level configuration file in a stylized variant of
493 <a href=http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt>kconfig</a> format. Includes generated/Config.in.</p>
495 <p>These files are directly used by "make menuconfig" to select which commands
496 to build into toybox (thus generating a .config file), and by
497 scripts/config2help.py to create generated/help.h.</p>
499 <a name="generated" />
500 <h1><a href="#generated">Temporary files:</a></h1>
502 <p>There is one temporary file in the top level source directory:</p>
504 <li><p><b>.config</b> - Configuration file generated by kconfig, indicating
505 which commands (and options to commands) are currently enabled. Used
506 to make generated/config.h and determine which toys/*/*.c files to build.</p>
508 <p>You can create a human readable "miniconfig" version of this file using
509 <a href=http://landley.net/aboriginal/new_platform.html#miniconfig>these
510 instructions</a>.</p>
514 <p><h2>Directory generated/</h2></p>
516 <p>The remaining temporary files live in the "generated/" directory,
517 which is for files generated at build time from other source files.</p>
520 <li><p><b>generated/Config.in</b> - Kconfig entries for each command, included
521 from the top level Config.in. The help text here is used to generate
524 <p>Each command has a configuration entry with an upper case version of
525 the command name. Options to commands start with the command
526 name followed by an underscore and the option name. Global options are attached
527 to the "toybox" command, and thus use the prefix "TOYBOX_". This organization
528 is used by scripts/cfg2files to select which toys/*/*.c files to compile for a
532 <li><p><b>generated/config.h</b> - list of CFG_SYMBOL and USE_SYMBOL() macros,
533 generated from .config by a sed invocation in scripts/make.sh.</p>
535 <p>CFG_SYMBOL is a comple time constant set to 1 for enabled symbols and 0 for
536 disabled symbols. This allows the use of normal if() statements to remove
537 code at compile time via the optimizer's dead code elimination (which removes
538 from the binary any code that cannot be reached). This saves space without
539 cluttering the code with #ifdefs or leading to configuration dependent build
540 breaks. (See the 1992 Usenix paper
541 <a href=http://doc.cat-v.org/henry_spencer/ifdef_considered_harmful.pdf>#ifdef
542 Considered Harmful</a> for more information.)</p>
544 <p>When you can't entirely avoid an #ifdef, the USE_SYMBOL(code) macro
545 provides a less intrusive alternative, evaluating to the code in parentheses
546 when the symbol is enabled, and nothing when the symbol is disabled. This
547 is most commonly used around NEWTOY() declarations (so only the enabled
548 commands show up in toy_list), and in option strings. This can also be used
549 for things like varargs or structure members which can't always be
550 eliminated by a simple test on CFG_SYMBOL. Remember, unlike CFG_SYMBOL
551 this is really just a variant of #ifdef, and can still result in configuration
552 dependent build breaks. Use with caution.</p>
555 <li><p><b>generated/flags.h</b> - FLAG_? macros indicating which command
556 line options were seen. The option parsing in lib/args.c sets bits in
557 toys.optflags, which can be tested by anding with the appropriate FLAG_
558 macro. (Bare longopts, which have no corresponding short option, will
559 have the longopt name after FLAG_. All others use the single letter short
562 <p>To get the appropriate macros for your command, #define FOR_commandname
563 before #including toys.h. To switch macro sets (because you have an OLDTOY()
564 with different options in the same .c file), #define CLEANUP_oldcommand
565 and also #define FOR_newcommand, then #include "generated/flags.h" to switch.
569 <li><p><b>generated/globals.h</b> -
570 Declares structures to hold the contents of each command's GLOBALS(),
571 and combines them into "global_union this". (Yes, the name was
572 chosen to piss off C++ developers who think that C
573 is merely a subset of C++, not a language in its own right.)</p>
575 <p>The union reuses the same memory for each command's global struct:
576 since only one command's globals are in use at any given time, collapsing
577 them together saves space. The headers #define TT to the appropriate
578 "this.commandname", so you can refer to the current command's global
579 variables out of "this" as TT.variablename.</p>
581 <p>The globals start zeroed, and the first few are filled out by the
582 lib/args.c argument parsing code called from main.c.</p>
585 <li><p><b>toys/help.h</b> - Help strings for use by the "help" command and
586 --help options. This file #defines a help_symbolname string for each
587 symbolname, but only the symbolnames matching command names get used
588 by show_help() in lib/help.c to display help for commands.</p>
590 <p>This file is created by scripts/make.sh, which compiles scripts/config2help.c
591 into the binary generated/config2help, and then runs it against the top
592 level .config and Config.in files to extract the help text from each config
593 entry and collate together dependent options.</p>
595 <p>This file contains help text for all commands, regardless of current
596 configuration, but only the ones currently enabled in the .config file
597 wind up in the help_data[] array, and only the enabled dependent options
598 have their help text added to the command they depend on.</p>
601 <li><p><b>generated/newtoys.h</b> -
602 All the NEWTOY() and OLDTOY() macros from toys/*/*.c. The "toybox" multiplexer
603 is the first entry, the rest are in alphabetical order. Each line should be
604 inside an appropriate USE_ macro, so code that #includes this file only sees
605 the currently enabled commands.</p>
607 <p>By #definining NEWTOY() to various things before #including this file,
608 it may be used to create function prototypes (in toys.h), initialize the
609 help_data array (in lib/help.c), initialize the toy_list array (in main.c,
610 the alphabetical order lets toy_find() do a binary search, the exception to
611 the alphabetical order lets it use the multiplexer without searching), and so
612 on. (It's even used to initialize the NEED_OPTIONS macro, which produces a 1
613 or 0 for each command using command line option parsing, which is ORed together
614 to allow compile-time dead code elimination to remove the whole of
615 lib/args.c if nothing currently enabled is using it.)<p>
617 <p>Each NEWTOY and OLDTOY macro contains the command name, command line
618 option string (telling lib/args.c how to parse command line options for
619 this command), recommended install location, and miscelaneous data such
620 as whether this command should retain root permissions if installed suid.</p>
623 <li><p><b>toys/oldtoys.h</b> - Macros with the command line option parsing
624 string for each NEWTOY. This allows an OLDTOY that's just an alias for an
625 existing command to refer to the existing option string instead of
626 having to repeat it.</p>
631 <h2>Directory lib/</h2>
633 <p>TODO: document lots more here.</p>
635 <p>lib: getmountlist(), error_msg/error_exit, xmalloc(),
636 strlcpy(), xexec(), xopen()/xread(), xgetcwd(), xabspath(), find_in_path(),
641 <a name="lib_xwrap"><h3>lib/xwrap.c</h3>
643 <p>Functions prefixed with the letter x call perror_exit() when they hit
644 errors, to eliminate common error checking. This prints an error message
645 and the strerror() string for the errno encountered.</p>
647 <p>We replaced exit(), _exit(), and atexit() with xexit(), _xexit(), and
648 sigatexit(). This gives _xexit() the option to siglongjmp(toys.rebound, 1)
649 instead of exiting, lets xexit() report stdout flush failures to stderr
650 and change the exit code to indicate error, lets our toys.exit function
651 change happen for signal exit paths and lets us remove the functions
652 after we've called them.</p>
654 <p>You can intercept our exit by assigning a setjmp/longjmp buffer to
655 toys.rebound (set it back to zero to restore the default behavior).
656 If you do this, cleaning up resource leaks is your problem.</p>
659 <li><b>void xstrncpy(char *dest, char *src, size_t size)</b></li>
660 <li><p><b><p>void _xexit(void)</b></p>
661 <p>Calls siglongjmp(toys.rebound, 1), or else _exit(toys.exitval). This
662 lets you ignore errors with the NO_EXIT() macro wrapper, or intercept
663 them with WOULD_EXIT().</p>
664 <li><b><p>void xexit(void)</b></p>
665 <p>Calls toys.xexit functions (if any) and flushes stdout/stderr (reporting
666 failure to write to stdout both to stderr and in the exit code), then
669 <li><b>void *xmalloc(size_t size)</b></li>
670 <li><b>void *xzalloc(size_t size)</b></li>
671 <li><b>void *xrealloc(void *ptr, size_t size)</b></li>
672 <li><b>char *xstrndup(char *s, size_t n)</b></li>
673 <li><b>char *xstrdup(char *s)</b></li>
674 <li><b>char *xmprintf(char *format, ...)</b></li>
675 <li><b>void xprintf(char *format, ...)</b></li>
676 <li><b>void xputs(char *s)</b></li>
677 <li><b>void xputc(char c)</b></li>
678 <li><b>void xflush(void)</b></li>
679 <li><b>pid_t xfork(void)</b></li>
680 <li><b>void xexec_optargs(int skip)</b></li>
681 <li><b>void xexec(char **argv)</b></li>
682 <li><b>pid_t xpopen(char **argv, int *pipes)</b></li>
683 <li><b>int xpclose(pid_t pid, int *pipes)</b></li>
684 <li><b>void xaccess(char *path, int flags)</b></li>
685 <li><b>void xunlink(char *path)</b></li>
686 <li><p><b>int xcreate(char *path, int flags, int mode)<br />
687 int xopen(char *path, int flags)</b></p>
689 <p>The xopen() and xcreate() functions open an existing file (exiting if
690 it's not there) and create a new file (exiting if it can't).</p>
692 <p>They default to O_CLOEXEC so the filehandles aren't passed on to child
693 processes. Feed in O_CLOEXEC to disable this.</p>
695 <li><p><b>void xclose(int fd)</b></p>
697 <p>Because NFS is broken, and won't necessarily perform the requested
698 operation (and report the error) until you close the file. Of course, this
699 being NFS, it's not guaranteed to report the error there either, but it
702 <p>Nothing else ever reports an error on close, everywhere else it's just a
703 VFS operation freeing some resources. NFS is _special_, in a way that
704 other network filesystems like smbfs and v9fs aren't..</p>
706 <li><b>int xdup(int fd)</b></li>
707 <li><p><b>size_t xread(int fd, void *buf, size_t len)</b></p>
709 <p>Can return 0, but not -1.</p>
711 <li><p><b>void xreadall(int fd, void *buf, size_t len)</b></p>
713 <p>Reads the entire len-sized buffer, retrying to complete short
714 reads. Exits if it can't get enough data.</p></li>
716 <li><p><b>void xwrite(int fd, void *buf, size_t len)</b></p>
718 <p>Retries short writes, exits if can't write the entire buffer.</p></li>
720 <li><b>off_t xlseek(int fd, off_t offset, int whence)</b></li>
721 <li><b>char *xgetcwd(void)</b></li>
722 <li><b>void xstat(char *path, struct stat *st)</b></li>
723 <li><p><b>char *xabspath(char *path, int exact) </b></p>
725 <p>After several years of
726 <a href=http://landley.net/notes-2007.html#18-06-2007>wrestling</a>
727 <a href=http://landley.net/notes-2008.html#19-01-2008>with</a> realpath(),
728 I broke down and <a href=http://landley.net/notes-2012.html#20-11-2012>wrote
729 my own</a> implementation that doesn't use the one in libc. As I explained:
731 <blockquote><p>If the path ends with a broken link,
732 readlink -f should show where the link points to, not where the broken link
733 lives. (The point of readlink -f is "if I write here, where would it attempt
734 to create a file".) The problem is, realpath() returns NULL for a path ending
735 with a broken link, and I can't beat different behavior out of code locked
736 away in libc.</p></blockquote>
740 <li><b>void xchdir(char *path)</b></li>
741 <li><b>void xchroot(char *path)</b></li>
743 <li><p><b>struct passwd *xgetpwuid(uid_t uid)<br />
744 struct group *xgetgrgid(gid_t gid)<br />
745 struct passwd *xgetpwnam(char *name)</b></p>
752 <li><b>void xsetuser(struct passwd *pwd)</b></li>
753 <li><b>char *xreadlink(char *name)</b></li>
754 <li><b>char *xreadfile(char *name, char *buf, off_t len)</b></li>
755 <li><b>int xioctl(int fd, int request, void *data)</b></li>
756 <li><b>void xpidfile(char *name)</b></li>
757 <li><b>void xsendfile(int in, int out)</b></li>
758 <li><b>long xparsetime(char *arg, long units, long *fraction)</b></li>
759 <li><b>void xregcomp(regex_t *preg, char *regex, int cflags)</b></li>
762 <a name="lib_lib"><h3>lib/lib.c</h3>
763 <p>Eight gazillion common functions:</p>
766 <li><b>void verror_msg(char *msg, int err, va_list va)</b></li>
767 <li><b>void error_msg(char *msg, ...)</b></li>
768 <li><b>void perror_msg(char *msg, ...)</b></li>
769 <li><b>void error_exit(char *msg, ...)</b></li>
770 <li><b>void perror_exit(char *msg, ...)</b></li>
771 <li><b>ssize_t readall(int fd, void *buf, size_t len)</b></li>
772 <li><b>ssize_t writeall(int fd, void *buf, size_t len)</b></li>
773 <li><b>off_t lskip(int fd, off_t offset)</b></li>
774 <li><b>int mkpathat(int atfd, char *dir, mode_t lastmode, int flags)</b></li>
775 <li><b>struct string_list **splitpath(char *path, struct string_list **list)</b></li>
776 <li><b>struct string_list *find_in_path(char *path, char *filename)</b></li>
777 <li><b>long atolx(char *numstr)</b></li>
778 <li><b>long atolx_range(char *numstr, long low, long high)</b></li>
779 <li><b>int numlen(long l)</b></li>
780 <li><b>int stridx(char *haystack, char needle)</b></li>
781 <li><b>int strstart(char **a, char *b)</b></li>
782 <li><b>off_t fdlength(int fd)</b></li>
783 <li><b>char *readfile(char *name, char *ibuf, off_t len)</b></li>
784 <li><b>void msleep(long miliseconds)</b></li>
785 <li><b>int64_t peek_le(void *ptr, unsigned size)</b></li>
786 <li><b>int64_t peek_be(void *ptr, unsigned size)</b></li>
787 <li><b>int64_t peek(void *ptr, unsigned size)</b></li>
788 <li><b>void poke(void *ptr, uint64_t val, int size)</b></li>
789 <li><b>void loopfiles_rw(char **argv, int flags, int permissions, int failok,</b></li>
790 <li><b>void loopfiles(char **argv, void (*function)(int fd, char *name))</b></li>
791 <li><b>char *get_rawline(int fd, long *plen, char end)</b></li>
792 <li><b>char *get_line(int fd)</b></li>
793 <li><b>int wfchmodat(int fd, char *name, mode_t mode)</b></li>
794 <li><b>static void tempfile_handler(int i)</b></li>
795 <li><b>int copy_tempfile(int fdin, char *name, char **tempname)</b></li>
796 <li><b>void delete_tempfile(int fdin, int fdout, char **tempname)</b></li>
797 <li><b>void replace_tempfile(int fdin, int fdout, char **tempname)</b></li>
798 <li><b>void crc_init(unsigned int *crc_table, int little_endian)</b></li>
799 <li><b>int terminal_size(unsigned *xx, unsigned *yy)</b></li>
800 <li><b>int yesno(char *prompt, int def)</b></li>
801 <li><b>void generic_signal(int sig)</b></li>
802 <li><b>void sigatexit(void *handler)</b></li>
803 <li><b>int sig_to_num(char *pidstr)</b></li>
804 <li><b>char *num_to_sig(int sig)</b></li>
805 <li><b>mode_t string_to_mode(char *modestr, mode_t mode)</b></li>
806 <li><b>void mode_to_string(mode_t mode, char *buf)</b></li>
807 <li><b>void names_to_pid(char **names, int (*callback)(pid_t pid, char *name))</b></li>
808 <li><b>int human_readable(char *buf, unsigned long long num)</b></li>
811 <h3>lib/portability.h</h3>
813 <p>This file is automatically included from the top of toys.h, and smooths
814 over differences between platforms (hardware targets, compilers, C libraries,
815 operating systems, etc).</p>
817 <p>This file provides SWAP macros (SWAP_BE16(x) and SWAP_LE32(x) and so on).</p>
819 <p>A macro like SWAP_LE32(x) means "The value in x is stored as a little
820 endian 32 bit value, so perform the translation to/from whatever the native
821 32-bit format is". You do the swap once on the way in, and once on the way
822 out. If your target is already little endian, the macro is a NOP.</p>
824 <p>The SWAP macros come in BE and LE each with 16, 32, and 64 bit versions.
825 In each case, the name of the macro refers to the _external_ representation,
826 and converts to/from whatever your native representation happens to be (which
827 can vary depending on what you're currently compiling for).</p>
829 <a name="lib_llist"><h3>lib/llist.c</h3>
831 <p>Some generic single and doubly linked list functions, which take
832 advantage of a couple properties of C:</p>
835 <li><p>Structure elements are laid out in memory in the order listed, and
836 the first element has no padding. This means you can always treat (typecast)
837 a pointer to a structure as a pointer to the first element of the structure,
838 even if you don't know anything about the data following it.</p></li>
840 <li><p>An array of length zero at the end of a structure adds no space
841 to the sizeof() the structure, but if you calculate how much extra space
842 you want when you malloc() the structure it will be available at the end.
843 Since C has no bounds checking, this means each struct can have one variable
844 length array.</p></li>
847 <p>Toybox's list structures always have their <b>next</b> pointer as
848 the first entry of each struct, and singly linked lists end with a NULL pointer.
849 This allows generic code to traverse such lists without knowing anything
850 else about the specific structs composing them: if your pointer isn't NULL
851 typecast it to void ** and dereference once to get the next entry.</p>
853 <p><b>lib/lib.h</b> defines three structure types:</p>
855 <li><p><b>struct string_list</b> - stores a single string (<b>char str[0]</b>),
856 memory for which is allocated as part of the node. (I.E. llist_traverse(list,
857 free); can clean up after this type of list.)</p></li>
859 <li><p><b>struct arg_list</b> - stores a pointer to a single string
860 (<b>char *arg</b>) which is stored in a separate chunk of memory.</p></li>
862 <li><p><b>struct double_list</b> - has a second pointer (<b>struct double_list
863 *prev</b> along with a <b>char *data</b> for payload.</p></li>
866 <b>List Functions</b>
869 <li><p>void *<b>llist_pop</b>(void **list) - advances through a list ala
870 <b>node = llist_pop(&list);</b> This doesn't modify the list contents,
871 but does advance the pointer you feed it (which is why you pass the _address_
872 of that pointer, not the pointer itself).</p></li>
874 <li><p>void <b>llist_traverse</b>(void *list, void (*using)(void *data)) -
875 iterate through a list calling a function on each node.</p></li>
877 <li><p>struct double_list *<b>dlist_add</b>(struct double_list **llist, char *data)
878 - append an entry to a circular linked list.
879 This function allocates a new struct double_list wrapper and returns the
880 pointer to the new entry (which you can usually ignore since it's llist->prev,
881 but if llist was NULL you need it). The argument is the ->data field for the
883 <ul><li><p>void <b>dlist_add_nomalloc</b>(struct double_list **llist,
884 struct double_list *new) - append existing struct double_list to
885 list, does not allocate anything.</p></li></ul>
888 <b>List code trivia questions:</b>
891 <li><p><b>Why do arg_list and double_list contain a char * payload instead of
892 a void *?</b> - Because you always have to typecast a void * to use it, and
893 typecasting a char * does no harm. Since strings are the most common
894 payload, and doing math on the pointer ala
895 "(type *)(ptr+sizeof(thing)+sizeof(otherthing))" requires ptr to be char *
896 anyway (at least according to the C standard), defaulting to char * saves
900 <li><p><b>Why do the names ->str, ->arg, and ->data differ?</b> - To force
901 you to keep track of which one you're using, calling free(node->str) would
902 be bad, and _failing_ to free(node->arg) leaks memory.</p></li>
904 <li><p><b>Why does llist_pop() take a void * instead of void **?</b> -
905 because the stupid compiler complains about "type punned pointers" when
906 you typecast and dereference on the same line,
907 due to insane FSF developers hardwiring limitations of their optimizer
908 into gcc's warning system. Since C automatically typecasts any other
909 pointer type to and from void *, the current code works fine. It's sad that it
910 won't warn you if you forget the &, but the code crashes pretty quickly in
913 <li><p><b>How do I assemble a singly-linked-list in order?</b> - use
914 a double_list, dlist_add() your entries, and then break the circle with
915 <b>list->prev->next = NULL;</b> when done.</li>
918 <a name="lib_args"><h3>lib/args.c</h3>
920 <p>Toybox's main.c automatically parses command line options before calling the
921 command's main function. Option parsing starts in get_optflags(), which stores
922 results in the global structures "toys" (optflags and optargs) and "this".</p>
924 <p>The option parsing infrastructure stores a bitfield in toys.optflags to
925 indicate which options the current command line contained, and defines FLAG
926 macros code can use to check whether each argument's bit is set. Arguments
927 attached to those options are saved into the command's global structure
928 ("this"). Any remaining command line arguments are collected together into
929 the null-terminated array toys.optargs, with the length in toys.optc. (Note
930 that toys.optargs does not contain the current command name at position zero,
931 use "toys.which->name" for that.) The raw command line arguments get_optflags()
932 parsed are retained unmodified in toys.argv[].</p>
934 <p>Toybox's option parsing logic is controlled by an "optflags" string, using
935 a format reminiscent of getopt's optargs but with several important differences.
936 Toybox does not use the getopt()
937 function out of the C library, get_optflags() is an independent implementation
938 which doesn't permute the original arguments (and thus doesn't change how the
939 command is displayed in ps and top), and has many features not present in
940 libc optargs() (such as the ability to describe long options in the same string
941 as normal options).</p>
943 <p>Each command's NEWTOY() macro has an optflags string as its middle argument,
944 which sets toy_list.options for that command to tell get_optflags() what
945 command line arguments to look for, and what to do with them.
946 If a command has no option
947 definition string (I.E. the argument is NULL), option parsing is skipped
948 for that command, which must look at the raw data in toys.argv to parse its
949 own arguments. (If no currently enabled command uses option parsing,
950 get_optflags() is optimized out of the resulting binary by the compiler's
951 --gc-sections option.)</p>
953 <p>You don't have to free the option strings, which point into the environment
954 space (I.E. the string data is not copied). A TOYFLAG_NOFORK command
955 that uses the linked list type "*" should free the list objects but not
956 the data they point to, via "llist_free(TT.mylist, NULL);". (If it's not
957 NOFORK, exit() will free all the malloced data anyway unless you want
958 to implement a CONFIG_TOYBOX_FREE cleanup for it.)</p>
960 <h4>Optflags format string</h4>
962 <p>Note: the optflags option description string format is much more
963 concisely described by a large comment at the top of lib/args.c.</p>
965 <p>The general theory is that letters set optflags, and punctuation describes
966 other actions the option parsing logic should take.</p>
968 <p>For example, suppose the command line <b>command -b fruit -d walrus -a 42</b>
969 is parsed using the optflags string "<b>a#b:c:d</b>". (I.E.
970 toys.which->options="a#b:c:d" and argv = ["command", "-b", "fruit", "-d",
971 "walrus", "-a", "42"]). When get_optflags() returns, the following data is
972 available to command_main():
975 <li><p>In <b>struct toys</b>:
977 <li>toys.optflags = 13; // FLAG_a = 8 | FLAG_b = 4 | FLAG_d = 1</li>
978 <li>toys.optargs[0] = "walrus"; // leftover argument</li>
979 <li>toys.optargs[1] = NULL; // end of list</li>
980 <li>toys.optc = 1; // there was 1 leftover argument</li>
981 <li>toys.argv[] = {"-b", "fruit", "-d", "walrus", "-a", "42"}; // The original command line arguments
985 <li><p>In <b>union this</b> (treated as <b>long this[]</b>):
987 <li>this[0] = NULL; // -c didn't get an argument this time, so get_optflags() didn't change it and toys_init() zeroed "this" during setup.)</li>
988 <li>this[1] = (long)"fruit"; // argument to -b</li>
989 <li>this[2] = 42; // argument to -a</li>
994 <p>If the command's globals are:</p>
1004 <p>That would mean TT.c == NULL, TT.b == "fruit", and TT.a == 42. (Remember,
1005 each entry that receives an argument must be a long or pointer, to line up
1006 with the array position. Right to left in the optflags string corresponds to
1007 top to bottom in GLOBALS().</p>
1009 <p>Put globals not filled out by the option parsing logic at the end of the
1010 GLOBALS block. Common practice is to list the options one per line (to
1011 make the ordering explicit, first to last in globals corresponds to right
1012 to left in the option string), then leave a blank line before any non-option
1015 <p><b>long toys.optflags</b></p>
1017 <p>Each option in the optflags string corresponds to a bit position in
1018 toys.optflags, with the same value as a corresponding binary digit. The
1019 rightmost argument is (1<<0), the next to last is (1<<1) and so on. If
1020 the option isn't encountered while parsing argv[], its bit remains 0.</p>
1022 <p>Each option -x has a FLAG_x macro for the command letter. Bare --longopts
1023 with no corresponding short option have a FLAG_longopt macro for the long
1024 optionname. Commands enable these macros by #defining FOR_commandname before
1025 #including <toys.h>. When multiple commands are implemented in the same
1026 source file, you can switch flag contexts later in the file by
1027 #defining CLEANUP_oldcommand and #defining FOR_newcommand, then
1028 #including <generated/flags.h>.</p>
1030 <p>Options disabled in the current configuration (wrapped in
1031 a USE_BLAH() macro for a CONFIG_BLAH that's switched off) have their
1032 corresponding FLAG macro set to zero, so code checking them ala
1033 if (toys.optargs & FLAG_x) gets optimized out via dead code elimination.
1034 #defining FORCE_FLAGS when switching flag context disables this
1035 behavior: the flag is never zero even if the config is disabled. This
1036 allows code shared between multiple commands to use the same flag
1037 values, as long as the common flags match up right to left in both option
1041 the optflags string "abcd" would parse the command line argument "-c" to set
1042 optflags to 2, "-a" would set optflags to 8, "-bd" would set optflags to
1043 6 (I.E. 4|2), and "-a -c" would set optflags to 10 (2|8). To check if -c
1044 was encountered, code could test: if (toys.optflags & FLAG_c) printf("yup");
1045 (See the toys/examples directory for more.)</p>
1047 <p>Only letters are relevant to optflags, punctuation is skipped: in the
1048 string "a*b:c#d", d=1, c=2, b=4, a=8. The punctuation after a letter
1049 usually indicate that the option takes an argument.</p>
1051 <p>Since toys.optflags is an unsigned int, it only stores 32 bits. (Which is
1052 the amount a long would have on 32-bit platforms anyway; 64 bit code on
1053 32 bit platforms is too expensive to require in common code used by almost
1054 all commands.) Bit positions beyond the 1<<31 aren't recorded, but
1055 parsing higher options can still set global variables.</p>
1057 <p><b>Automatically setting global variables from arguments (union this)</b></p>
1059 <p>The following punctuation characters may be appended to an optflags
1060 argument letter, indicating the option takes an additional argument:</p>
1063 <li><b>:</b> - plus a string argument, keep most recent if more than one.</li>
1064 <li><b>*</b> - plus a string argument, appended to a linked list.</li>
1065 <li><b>@</b> - plus an occurrence counter (stored in a long)</li>
1066 <li><b>#</b> - plus a signed long argument.
1067 <li><b>-</b> - plus a signed long argument defaulting to negative (start argument with + to force a positive value).</li>
1068 <li><b>.</b> - plus a floating point argument (if CFG_TOYBOX_FLOAT).</li>
1069 <ul>The following can be appended to a float or double:
1070 <li><b><123</b> - error if argument is less than this</li>
1071 <li><b>>123</b> - error if argument is greater than this</li>
1072 <li><b>=123</b> - default value if argument not supplied</li>
1076 <p><b>GLOBALS</b></p>
1078 <p>Options which have an argument fill in the corresponding slot in the global
1079 union "this" (see generated/globals.h), treating it as an array of longs
1080 with the rightmost saved in this[0]. As described above, using "a*b:c#d",
1081 "-c 42" would set this[0] = 42; and "-b 42" would set this[1] = "42"; each
1082 slot is left NULL if the corresponding argument is not encountered.</p>
1084 <p>This behavior is useful because the LP64 standard ensures long and pointer
1085 are the same size. C99 guarantees structure members will occur in memory
1086 in the same order they're declared, and that padding won't be inserted between
1087 consecutive variables of register size. Thus the first few entries can
1088 be longs or pointers corresponding to the saved arguments.</p>
1090 <p>See toys/example/*.c for longer examples of parsing options into the
1093 <p><b>char *toys.optargs[]</b></p>
1095 <p>Command line arguments in argv[] which are not consumed by option parsing
1096 (I.E. not recognized either as -flags or arguments to -flags) will be copied
1097 to toys.optargs[], with the length of that array in toys.optc.
1098 (When toys.optc is 0, no unrecognized command line arguments remain.)
1099 The order of entries is preserved, and as with argv[] this new array is also
1100 terminated by a NULL entry.</p>
1102 <p>Option parsing can require a minimum or maximum number of optargs left
1103 over, by adding "<1" (read "at least one") or ">9" ("at most nine") to the
1104 start of the optflags string.</p>
1106 <p>The special argument "--" terminates option parsing, storing all remaining
1107 arguments in optargs. The "--" itself is consumed.</p>
1109 <p><b>Other optflags control characters</b></p>
1111 <p>The following characters may occur at the start of each command's
1112 optflags string, before any options that would set a bit in toys.optflags:</p>
1115 <li><b>^</b> - stop at first nonoption argument (for nice, xargs...)</li>
1116 <li><b>?</b> - allow unknown arguments (pass non-option arguments starting
1117 with - through to optargs instead of erroring out).</li>
1118 <li><b>&</b> - the first argument has imaginary dash (ala tar/ps. If given twice, all arguments have imaginary dash.)</li>
1119 <li><b><</b> - must be followed by a decimal digit indicating at least this many leftover arguments are needed in optargs (default 0)</li>
1120 <li><b>></b> - must be followed by a decimal digit indicating at most this many leftover arguments allowed (default MAX_INT)</li>
1123 <p>The following characters may be appended to an option character, but do
1124 not by themselves indicate an extra argument should be saved in this[].
1125 (Technically any character not recognized as a control character sets an
1126 optflag, but letters are never control characters.)</p>
1129 <li><b>^</b> - stop parsing options after encountering this option, everything else goes into optargs.</li>
1130 <li><b>|</b> - this option is required. If more than one marked, only one is required.</li>
1133 <p>The following may be appended to a float or double:</p>
1136 <li><b><123</b> - error if argument is less than this</li>
1137 <li><b>>123</b> - error if argument is greater than this</li>
1138 <li><b>=123</b> - default value if argument not supplied</li>
1141 <p>Option parsing only understands <>= after . when CFG_TOYBOX_FLOAT
1142 is enabled. (Otherwise the code to determine where floating point constants
1143 end drops out. When disabled, it can reserve a global data slot for the
1144 argument so offsets won't change, but will never fill it out.) You can handle
1145 this by using the USE_BLAH() macros with C string concatenation, ala:</p>
1147 <blockquote>"abc." USE_TOYBOX_FLOAT("<1.23>4.56=7.89") "def"</blockquote>
1149 <p><b>--longopts</b></p>
1151 <p>The optflags string can contain long options, which are enclosed in
1152 parentheses. They may be appended to an existing option character, in
1153 which case the --longopt is a synonym for that option, ala "a:(--fred)"
1154 which understands "-a blah" or "--fred blah" as synonyms.</p>
1156 <p>Longopts may also appear before any other options in the optflags string,
1157 in which case they have no corresponding short argument, but instead set
1158 their own bit based on position. So for "(walrus)#(blah)xy:z", "command
1159 --walrus 42" would set toys.optflags = 16 (-z = 1, -y = 2, -x = 4, --blah = 8)
1160 and would assign this[1] = 42;</p>
1162 <p>A short option may have multiple longopt synonyms, "a(one)(two)", but
1163 each "bare longopt" (ala "(one)(two)abc" before any option characters)
1164 always sets its own bit (although you can group them with +X).</p>
1166 <p>Only bare longopts have a FLAG_ macro with the longopt name
1167 (ala --fred would #define FLAG_fred). Other longopts use the short
1168 option's FLAG macro to test the toys.optflags bit.</p>
1170 <p>Options with a semicolon ";" after their data type can only set their
1171 corresponding GLOBALS() entry via "--longopt=value". For example, option
1172 string "x(boing): y" would set TT.x if it saw "--boing=value", but would
1173 treat "--boing value" as setting FLAG_x in toys.optargs, leaving TT.x NULL,
1174 and keeping "value" in toys.optargs[]. (This lets "ls --color" and
1175 "ls --color=auto" both work.)</p>
1177 <p><b>[groups]</b></p>
1179 <p>At the end of the option string, square bracket groups can define
1180 relationships between existing options. (This only applies to short
1181 options, bare --longopts can't participate.)</p>
1183 <p>The first character of the group defines the type, the remaining
1184 characters are options it applies to:</p>
1187 <li><b>-</b> - Exclusive, switch off all others in this group.</li>
1188 <li><b>+</b> - Inclusive, switch on all others in this group.</li>
1189 <li><b>!</b> - Error, fail if more than one defined.</li>
1192 <p>So "abc[-abc]" means -ab = -b, -ba = -a, -abc = -c. "abc[+abc]"
1193 means -ab=-abc, -c=-abc, and "abc[!abc] means -ab calls error_exit("no -b
1194 with -a"). Note that [-] groups clear the GLOBALS option slot of
1195 options they're switching back off, but [+] won't set options it didn't see
1196 (just the optflags).</p>
1198 <p><b>whitespace</b></p>
1200 <p>Arguments may occur with or without a space (I.E. "-a 42" or "-a42").
1201 The command line argument "-abc" may be interepreted many different ways:
1202 the optflags string "cba" sets toys.optflags = 7, "c:ba" sets toys.optflags=4
1203 and saves "ba" as the argument to -c, and "cb:a" sets optflags to 6 and saves
1204 "c" as the argument to -b.</p>
1206 <p>Note that & changes whitespace handling, so that the command line
1207 "tar cvfCj outfile.tar.bz2 topdir filename" is parsed the same as
1208 "tar filename -c -v -j -f outfile.tar.bz2 -C topdir". Note that "tar -cvfCj
1209 one two three" would equal "tar -c -v -f Cj one two three". (This matches
1210 historical usage.)</p>
1212 <p>Appending a space to the option in the option string ("a: b") makes it
1213 require a space, I.E. "-ab" is interpreted as "-a" "-b". That way "kill -stop"
1214 differs from "kill -s top".</p>
1216 <p>Appending ; to a longopt in the option string makes its argument optional,
1217 and only settable with =, so in ls "(color):;" can accept "ls --color" and
1218 "ls --color=auto" without complaining that the first has no argument.</p>
1220 <a name="lib_dirtree"><h3>lib/dirtree.c</h3>
1222 <p>The directory tree traversal code should be sufficiently generic
1223 that commands never need to use readdir(), scandir(), or the fts.h family
1226 <p>These functions do not call chdir() or rely on PATH_MAX. Instead they
1227 use openat() and friends, using one filehandle per directory level to
1228 recurse into subdirectories. (I.E. they can descend 1000 directories deep
1229 if setrlimit(RLIMIT_NOFILE) allows enough open filehandles, and the default
1230 in /proc/self/limits is generally 1024.)</p>
1232 <p>There are two main ways to use dirtree: 1) assemble a tree of nodes
1233 representing a snapshot of directory state and traverse them using the
1234 ->next and ->child pointers, or 2) traverse the tree calling a callback
1235 function on each entry, and freeing its node afterwards. (You can also
1236 combine the two, using the callback as a filter to determine which nodes
1239 <p>The basic dirtree functions are:</p>
1242 <li><p><b>struct dirtree *dirtree_read(char *path, int (*callback)(struct
1243 dirtree node))</b> - recursively read files and directories, calling
1244 callback() on each, and returning a tree of saved nodes (if any).
1245 If path doesn't exist, returns DIRTREE_ABORTVAL. If callback is NULL,
1246 returns a single node at that path.</p>
1248 <li><p><b>dirtree_notdotdot(struct dirtree *new)</b> - standard callback
1249 which discards "." and ".." entries and returns DIRTREE_SAVE|DIRTREE_RECURSE
1250 for everything else. Used directly, this assembles a snapshot tree of
1251 the contents of this directory and its subdirectories
1252 to be processed after dirtree_read() returns (by traversing the
1253 struct dirtree's ->next and ->child pointers from the returned root node).</p>
1255 <li><p><b>dirtree_path(struct dirtree *node, int *plen)</b> - malloc() a
1256 string containing the path from the root of this tree to this node. If
1257 plen isn't NULL then *plen is how many extra bytes to malloc at the end
1260 <li><p><b>dirtree_parentfd(struct dirtree *node)</b> - return fd of
1261 directory containing this node, for use with openat() and such.</p></li>
1264 <p>The <b>dirtree_read()</b> function is the standard way to start
1265 directory traversal. It takes two arguments: a starting path for
1266 the root of the tree, and a callback function. The callback() is called
1267 on each directory entry, its argument is a fully populated
1268 <b>struct dirtree *</b> (from lib/lib.h) describing the node, and its
1269 return value tells the dirtree infrastructure what to do next.</p>
1271 <p>(There's also a three argument version,
1272 <b>dirtree_flagread(char *path, int flags, int (*callback)(struct
1273 dirtree node))</b>, which lets you apply flags like DIRTREE_SYMFOLLOW and
1274 DIRTREE_SHUTUP to reading the top node, but this only affects the top node.
1275 Child nodes use the flags returned by callback().</p>
1277 <p><b>struct dirtree</b></p>
1279 <p>Each struct dirtree node contains <b>char name[]</b> and <b>struct stat
1280 st</b> entries describing a file, plus a <b>char *symlink</b>
1281 which is NULL for non-symlinks.</p>
1283 <p>During a callback function, the <b>int dirfd</b> field of directory nodes
1284 contains a directory file descriptor (for use with the openat() family of
1285 functions). This isn't usually used directly, intstead call dirtree_parentfd()
1286 on the callback's node argument. The <b>char again</a> field is 0 for the
1287 first callback on a node, and 1 on the second callback (triggered by returning
1288 DIRTREE_COMEAGAIN on a directory, made after all children have been processed).
1291 <p>Users of this code may put anything they like into the <b>long extra</b>
1292 field. For example, "cp" and "mv" use this to store a dirfd for the destination
1293 directory (and use DIRTREE_COMEAGAIN to get the second callback so they can
1294 close(node->extra) to avoid running out of filehandles).
1295 This field is not directly used by the dirtree code, and
1296 thanks to LP64 it's large enough to store a typecast pointer to an
1297 arbitrary struct.</p>
1299 <p>The return value of the callback combines flags (with boolean or) to tell
1300 the traversal infrastructure how to behave:</p>
1303 <li><p><b>DIRTREE_SAVE</b> - Save this node, assembling a tree. (Without
1304 this the struct dirtree is freed after the callback returns. Filtering out
1305 siblings is fine, but discarding a parent while keeping its child leaks
1307 <li><p><b>DIRTREE_ABORT</b> - Do not examine any more entries in this
1308 directory. (Does not propagate up tree: to abort entire traversal,
1309 return DIRTREE_ABORT from parent callbacks too.)</p></li>
1310 <li><p><b>DIRTREE_RECURSE</b> - Examine directory contents. Ignored for
1311 non-directory entries. The remaining flags only take effect when
1312 recursing into the children of a directory.</p></li>
1313 <li><p><b>DIRTREE_COMEAGAIN</b> - Call the callback on this node a second time
1314 after examining all directory contents, allowing depth-first traversal.
1315 On the second call, dirtree->again is nonzero.</p></li>
1316 <li><p><b>DIRTREE_SYMFOLLOW</b> - follow symlinks when populating children's
1317 <b>struct stat st</b> (by feeding a nonzero value to the symfollow argument of
1318 dirtree_add_node()), which means DIRTREE_RECURSE treats symlinks to
1319 directories as directories. (Avoiding infinite recursion is the callback's
1320 problem: the non-NULL dirtree->symlink can still distinguish between
1321 them. The "find" command follows ->parent up the tree to the root node
1322 each time, checking to make sure that stat's dev and inode pair don't
1323 match any ancestors.)</p></li>
1326 <p>Each struct dirtree contains three pointers (next, parent, and child)
1327 to other struct dirtree.</p>
1329 <p>The <b>parent</b> pointer indicates the directory
1330 containing this entry; even when not assembling a persistent tree of
1331 nodes the parent entries remain live up to the root of the tree while
1332 child nodes are active. At the top of the tree the parent pointer is
1333 NULL, meaning the node's name[] is either an absolute path or relative
1334 to cwd. The function dirtree_parentfd() gets the directory file descriptor
1335 for use with openat() and friends, returning AT_FDCWD at the top of tree.</p>
1337 <p>The <b>child</b> pointer points to the first node of the list of contents of
1338 this directory. If the directory contains no files, or the entry isn't
1339 a directory, child is NULL.</p>
1341 <p>The <b>next</b> pointer indicates sibling nodes in the same directory as this
1342 node, and since it's the first entry in the struct the llist.c traversal
1343 mechanisms work to iterate over sibling nodes. Each dirtree node is a
1344 single malloc() (even char *symlink points to memory at the end of the node),
1345 so llist_free() works but its callback must descend into child nodes (freeing
1346 a tree, not just a linked list), plus whatever the user stored in extra.</p>
1348 <p>The <b>dirtree_flagread</b>() function is a simple wrapper, calling <b>dirtree_add_node</b>()
1349 to create a root node relative to the current directory, then calling
1350 <b>dirtree_handle_callback</b>() on that node (which recurses as instructed by the callback
1351 return flags). The flags argument primarily lets you
1352 control whether or not to follow symlinks to the root node; symlinks
1353 listed on the command line are often treated differently than symlinks
1354 encountered during recursive directory traversal.
1356 <p>The ls command not only bypasses this wrapper, but never returns
1357 <b>DIRTREE_RECURSE</b> from the callback, instead calling <b>dirtree_recurse</b>() manually
1358 from elsewhere in the program. This gives ls -lR manual control
1359 of traversal order, which is neither depth first nor breadth first but
1360 instead a sort of FIFO order requried by the ls standard.</p>
1363 <h1><a href="#toys">Directory toys/</a></h1>
1365 <p>This directory contains command implementations. Each command is a single
1366 self-contained file. Adding a new command involves adding a single
1367 file, and removing a command involves removing that file. Commands use
1368 shared infrastructure from the lib/ and generated/ directories.</p>
1370 <p>Currently there are five subdirectories under "toys/" containing "posix"
1371 commands described in POSIX-2008, "lsb" commands described in the Linux
1372 Standard Base 4.1, "other" commands not described by either standard,
1373 "pending" commands awaiting cleanup (which default to "n" in menuconfig
1374 because they don't necessarily work right yet), and "example" code showing
1375 how toybox infrastructure works and providing template/skeleton files to
1376 start new commands.</p>
1378 <p>The only difference directory location makes is which menu the command
1379 shows up in during "make menuconfig", the directories are otherwise identical.
1380 Note that the commands exist within a single namespace at runtime, so you can't
1381 have the same command in multiple subdirectories. (The build tries to fail
1382 informatively when you do that.)</p>
1384 <p>There is one more sub-menus in "make menuconfig" containing global
1385 configuration options for toybox. This menu is defined in the top level
1388 <p>See <a href="#adding">adding a new command</a> for details on the
1389 layout of a command file.</p>
1391 <h2>Directory scripts/</h2>
1393 <p>Build infrastructure. The makefile calls scripts/make.sh for "make"
1394 and scripts/install.sh for "make install".</p>
1396 <p>There's also a test suite, "make test" calls make/test.sh, which runs all
1397 the tests in make/test/*. You can run individual tests via
1398 "scripts/test.sh command", or "TEST_HOST=1 scripts/test.sh command" to run
1399 that test against the host implementation instead of the toybox one.</p>
1401 <h3>scripts/cfg2files.sh</h3>
1403 <p>Run .config through this filter to get a list of enabled commands, which
1404 is turned into a list of files in toys via a sed invocation in the top level
1408 <h2>Directory kconfig/</h2>
1410 <p>Menuconfig infrastructure copied from the Linux kernel. See the
1411 Linux kernel's Documentation/kbuild/kconfig-language.txt</p>
1415 Better OLDTOY and multiple command explanation. From Config.in:
1417 <p>A command with multiple names (or multiple similar commands implemented in
1418 the same .c file) should have config symbols prefixed with the name of their
1419 C file. I.E. config symbol prefixes are NEWTOY() names. If OLDTOY() names
1420 have config symbols they must be options (symbols with an underscore and
1421 suffix) to the NEWTOY() name. (See generated/toylist.h)</p>
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