1<html><head><title>toybox source code walkthrough</title></head> 2<!--#include file="header.html" --> 3 4<p><h1><a name="style" /><a href="#style">Code style</a></h1></p> 5 6<p>The primary goal of toybox is _simple_ code. Keeping the code small is 7second, 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> 9 10<p>A simple implementation usually takes up fewer lines of source code, 11meaning more code can fit on the screen at once, meaning the programmer can 12see more of it on the screen and thus keep more if in their head at once. 13This helps code auditing and thus reduces bugs. That said, sometimes being 14more explicit is preferable to being clever enough to outsmart yourself: 15don't be so terse your code is unreadable.</p> 16 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 19want the code to be consistent.</p> 20 21<p><h1><a name="building" /><a href="#building">Building Toybox</a></h1></p> 22 23<p>Toybox is configured using the 24<a href=https://github.com/torvalds/linux/blob/v2.6.16/Documentation/kbuild/kconfig-language.txt>Kconfig language</a> pioneered by the Linux 25kernel, and adopted by many other projects (buildroot, OpenEmbedded, etc). 26This generates a ".config" file containing the selected options, which 27controls which features are included when compiling toybox.</p> 28 29<p>Each configuration option has a default value. The defaults indicate the 30"maximum sane configuration", I.E. if the feature defaults to "n" then it 31either isn't complete or is a special-purpose option (such as debugging 32code) that isn't intended for general purpose use.</p> 33 34<p>For a more compact human-editable version .config files, you can use the 35<a href=http://landley.net/aboriginal/FAQ.html#dev_miniconfig>miniconfig</a> 36format.</p> 37 38<p>The standard build invocation is:</p> 39 40<ul> 41<li>make defconfig #(or menuconfig)</li> 42<li>make</li> 43<li>make install</li> 44</ul> 45 46<p>Type "make help" to see all available build options.</p> 47 48<p>The file "configure" contains a number of environment variable definitions 49which influence the build, such as specifying which compiler to use or where 50to install the resulting binaries. This file is included by the build, but 51accepts existing definitions of the environment variables, so it may be sourced 52or modified by the developer before building and the definitions exported 53to the environment will take precedence.</p> 54 55<p>(To clarify: ".config" lists the features selected by defconfig/menuconfig, 56I.E. "what to build", and "configure" describes the build and installation 57environment, I.E. "how to build it".)</p> 58 59<p>By default "make install" puts files in /usr/toybox. Adding this to the 60$PATH is up to you. The environment variable $PREFIX can change the 61install location, ala "PREFIX=/usr/local/bin make install".</p> 62 63<p>If you need an unstripped (debug) version of any of these binaries, 64look in generated/unstripped.</p> 65 66<p><h1><a name="running"><a href="#running">Running a command</a></h1></p> 67 68<h2>main</h2> 69 70<p>The toybox main() function is at the end of main.c at the top level. It has 71two possible codepaths, only one of which is configured into any given build 72of toybox.</p> 73 74<p>If CONFIG_SINGLE is selected, toybox is configured to contain only a single 75command, so most of the normal setup can be skipped. In this case the 76multiplexer isn't used, instead main() calls toy_singleinit() (also in main.c) 77to set up global state and parse command line arguments, calls the command's 78main 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 79it flushes stdout (detecting error) and returns toys.exitval.</p> 80 81<p>When CONFIG_SINGLE is not selected, main() uses basename() to find the 82name it was run as, shifts its argument list one to the right so it lines up 83with where the multiplexer function expects it, and calls toybox_main(). This 84leverages the multiplexer command's infrastructure to find and run the 85appropriate command. (A command name starting with "toybox" will 86recursively call toybox_main(); you can go "./toybox toybox toybox toybox ls" 87if you want to...)</p> 88 89<h2>toybox_main</h2> 90 91<p>The toybox_main() function is also in main,c. It handles a possible 92--help option ("toybox --help ls"), prints the list of available commands if no 93arguments were provided to the multiplexer (or with full path names if any 94other option is provided before a command name, ala "toybox --list"). 95Otherwise it calls toy_exec() on its argument list.</p> 96 97<p>Note that the multiplexer is the first entry in toy_list (the rest of the 98list is sorted alphabetically to allow binary search), so toybox_main can 99cheat and just grab the first entry to quickly set up its context without 100searching. Since all command names go through the multiplexer at least once 101in the non-TOYBOX_SINGLE case, this avoids a redundant search of 102the list.</p> 103 104<p>The toy_exec() function is also in main.c. It performs toy_find() to 105perform a binary search on the toy_list array to look up the command's 106entry by name and saves it in the global variable which, calls toy_init() 107to parse command line arguments and set up global state (using which->options), 108and calls the appropriate command's main() function (which->toy_main). On 109return it flushes all pending ansi FILE * I/O, detects if stdout had an 110error, and then calls xexit() (which uses toys.exitval).</p> 111 112<p><h1><a name="infrastructure" /><a href="#infrastructure">Infrastructure</a></h1></p> 113 114<p>The toybox source code is in following directories:</p> 115<ul> 116<li>The <a href="#top">top level directory</a> contains the file main.c (were 117execution starts), the header file toys.h (included by every command), and 118other global infrastructure.</li> 119<li>The <a href="#lib">lib directory</a> contains common functions shared by 120multiple commands:</li> 121<ul> 122<li><a href="#lib_lib">lib/lib.c</a></li> 123<li><a href="#lib_xwrap">lib/xwrap.c</a></li> 124<li><a href="#lib_llist">lib/llist.c</a></li> 125<li><a href="#lib_args">lib/args.c</a></li> 126<li><a href="#lib_dirtree">lib/dirtree.c</a></li> 127</ul> 128<li>The <a href="#toys">toys directory</a> contains the C files implementating 129each command. Currently it contains five subdirectories categorizing the 130commands: posix, lsb, other, example, and pending.</li> 131<li>The <a href="#scripts">scripts directory</a> contains the build and 132test infrastructure.</li> 133<li>The <a href="#kconfig">kconfig directory</a> contains the configuration 134infrastructure implementing menuconfig (copied from the Linux kernel).</li> 135<li>The <a href="#generated">generated directory</a> contains intermediate 136files generated from other parts of the source code.</li> 137<li>The <a href="#tests">tests directory</a> contains the test suite. 138NOSPACE=1 to allow tests to pass with diff -b</li> 139</ul> 140 141<a name="adding" /> 142<p><h1><a href="#adding">Adding a new command</a></h1></p> 143<p>To add a new command to toybox, add a C file implementing that command to 144one of the subdirectories under the toys directory. No other files need to 145be modified; the build extracts all the information it needs (such as command 146line arguments) from specially formatted comments and macros in the C file. 147(See the description of the <a href="#generated">"generated" directory</a> 148for details.)</p> 149 150<p>Currently there are five subdirectories under "toys", one for commands 151defined by the POSIX standard, one for commands defined by the Linux Standard 152Base, an "other" directory for commands not covered by an obvious standard, 153a directory of example commands (templates to use when starting new commands), 154and a "pending" directory of commands that need further review/cleanup 155before moving to one of the other directories (run these at your own risk, 156cleanup patches welcome). 157These directories are just for developer convenience sorting the commands, 158the directories are otherwise functionally identical. To add a new category, 159create the appropriate directory with a README file in it whose first line 160is the description menuconfig should use for the directory.)</p> 161 162<p>An easy way to start a new command is copy the file "toys/example/hello.c" 163to the name of the new command, and modify this copy to implement the new 164command (more or less by turning every instance of "hello" into the 165name of your command, updating the command line arguments, globals, and 166help data, and then filling out its "main" function with code that does 167something interesting).</p> 168 169<p>You could also start with "toys/example/skeleton.c", which provides a lot 170more example code (showing several variants of command line option 171parsing, how to implement multiple commands in the same file, and so on). 172But usually it's just more stuff to delete.</p> 173 174<p>Here's a checklist of steps to turn hello.c into another command:</p> 175 176<ul> 177<li><p>First "cp toys/example/hello.c toys/other/yourcommand.c" and open 178the new file in your preferred text editor.</p> 179<ul><li><p>Note that the 180name of the new file is significant: it's the name of the new command you're 181adding to toybox. The build includes all *.c files under toys/*/ whose 182names are a case insensitive match for an enabled config symbol. So 183toys/posix/cat.c only gets included if you have "CAT=y" in ".config".</p></li> 184</ul></p></li> 185 186<li><p>Change the one line comment at the top of the file (currently 187"hello.c - A hello world program") to describe your new file.</p></li> 188 189<li><p>Change the copyright notice to your name, email, and the current 190year.</p></li> 191 192<li><p>Give a URL to the relevant standards document, where applicable. 193(Sample links to SUSv4, LSB, IETF RFC, and man7.org are provided, feel free to 194link to other documentation or standards as appropriate.)</p></li> 195 196<li><p>Update the USE_YOURCOMMAND(NEWTOY(yourcommand,"blah",0)) line. 197The NEWTOY macro fills out this command's <a href="#toy_list">toy_list</a> 198structure. The arguments to the NEWTOY macro are:</p> 199 200<ol> 201<li><p>the name used to run your command</p></li> 202<li><p>the command line argument <a href="#lib_args">option parsing string</a> (0 if none)</p></li> 203<li><p>a bitfield of TOYFLAG values 204(defined in toys.h) providing additional information such as where your 205command should be installed on a running system, whether to blank umask 206before running, whether or not the command must run as root (and thus should 207retain root access if installed SUID), and so on.</p></li> 208</ol> 209</li> 210 211<li><p>Change the kconfig data (from "config YOURCOMMAND" to the end of the 212comment block) to supply your command's configuration and help 213information. The uppper case config symbols are used by menuconfig, and are 214also what the CFG_ and USE_() macros are generated from (see [TODO]). The 215help information here is used by menuconfig, and also by the "help" command to 216describe your new command. (See [TODO] for details.) By convention, 217unfinished commands default to "n" and finished commands default to "y", 218so "make defconfig" selects all finished commands. (Note, "finished" means 219"ready to be used", not that it'll never change again.)<p> 220 221<p>Each help block should start with a "usage: yourcommand" line explaining 222any command line arguments added by this config option. The "help" command 223outputs this text, and scripts/config2help.c in the build infrastructure 224collates these usage lines for commands with multiple configuration 225options when producing generated/help.h.</p> 226</li> 227 228<li><p>Change the "#define FOR_hello" line to "#define FOR_yourcommand" right 229before the "#include <toys.h>". (This selects the appropriate FLAG_ macros and 230does a "#define TT this.yourcommand" so you can access the global variables 231out of the space-saving union of structures. If you aren't using any command 232flag bits and aren't defining a GLOBAL block, you can delete this line.)</p></li> 233 234<li><p>Update the GLOBALS() macro to contain your command's global 235variables. If your command has no global variables, delete this macro.</p> 236 237<p>Variables in the GLOBALS() block are are stored in a space saving 238<a href="#toy_union">union of structures</a> format, which may be accessed 239using the TT macro as if TT were a global structure (so TT.membername). 240If you specified two-character command line arguments in 241NEWTOY(), the first few global variables will be initialized by the automatic 242argument parsing logic, and the type and order of these variables must 243correspond to the arguments specified in NEWTOY(). 244(See <a href="#lib_args">lib/args.c</a> for details.)</p> 245 246<blockquote><p>NOTE: the GLOBALS() block creates a "this.filename" entry 247in generated/globals.h. If your toys/*/filename.c does not match the first 248command name, you'll need to "#define TT this.filename" yourself before 249#including toys.h if you want to use TT globals</p></blockquote> 250</li> 251 252<li><p>Rename hello_main() to yourcommand_main(). This is the main() function 253where execution of your command starts. Your command line options are 254already sorted into this.optflags, this.optargs, this.optc, and the GLOBALS() 255as appropriate by the time this function is called. (See 256<a href="#lib_args">get_optflags()</a> for details.)</p></li> 257 258<li><p>Switch on TOYBOX_DEBUG in menuconfig (toybox global settings menu) 259the first time you build and run your new command. If anything is wrong 260with your option string, that will give you error messages.</p> 261 262<p>Otherwise it'll just segfault without 263explanation when it falls off the end because it didn't find a matching 264end parantheses for a longopt, or you put a nonexistent option in a square 265bracket grouping... Since these kind of errors can only be caused by a 266developer, not by end users, we don't normally want runtime checks for 267them. Once you're happy with your option string, you can switch TOYBOX_DEBUG 268back off.</p></li> 269</ul> 270 271<a name="headers" /><h2><a href="#headers">Headers.</a></h2> 272 273<p>Commands are implemented as self-contained .c files, and generally don't 274have their own .h files. If it's common code put it in lib/, and if it's 275something like a local structure definition just put it in the command's .c 276file. If it would only ever be #included from one place, inline it. 277(The line between implementing multiple commands in a C file via OLDTOY() 278to share infrastructure and moving that shared infrastructure to lib/ is a 279judgement call. Try to figure out which is simplest.)</p> 280 281<p>The top level toys.h should #include all the standard (posix) headers 282that any command uses. (Partly this is friendly to ccache and partly this 283makes the command implementations shorter.) Individual commands should only 284need to include nonstandard headers that might prevent that command from 285building in some context we'd care about (and thus requiring that command to 286be disabled to avoid a build break).</p> 287 288<p>Target-specific stuff (differences between compiler versions, libc versions, 289or operating systems) should be confined to lib/portability.h and 290lib/portability.c. (There's even some minimal compile-time environment probing 291that writes data to generated/portability.h, see scripts/genconfig.sh.)</p> 292 293<p>Only include <linux/*.h> headers from individual commands (not from other 294headers), and only if you really need to. Data that varies per architecture 295is a good reason to include a header. If you just need a couple constants 296that haven't changed since the 1990's, it's ok to #define them yourself or 297just use the constant inline with a comment explaining what it is. (A 298#define that's only used once isn't really helping.)</p> 299 300<p><a name="top" /><h1><a href="#top">Top level directory.</a></h1></p> 301 302<p>This directory contains global infrastructure.</p> 303 304<h3>toys.h</h3> 305<p>Each command #includes "toys.h" as part of its standard prolog. It 306may "#define FOR_commandname" before doing so to get some extra entries 307specific to this command.</p> 308 309<p>This file sucks in most of the commonly used standard #includes, so 310individual files can just #include "toys.h" and not have to worry about 311stdargs.h and so on. Individual commands still need to #include 312special-purpose headers that may not be present on all systems (and thus would 313prevent toybox from building that command on such a system with that command 314enabled). Examples include regex support, any "linux/" or "asm/" headers, mtab 315support (mntent.h and sys/mount.h), and so on.</p> 316 317<p>The toys.h header also defines structures for most of the global variables 318provided to each command by toybox_main(). These are described in 319detail in the description for main.c, where they are initialized.</p> 320 321<p>The global variables are grouped into structures (and a union) for space 322savings, to more easily track the amount of memory consumed by them, 323so that they may be automatically cleared/initialized as needed, and so 324that access to global variables is more easily distinguished from access to 325local variables.</p> 326 327<h3>main.c</h3> 328<p>Contains the main() function where execution starts, plus 329common infrastructure to initialize global variables and select which command 330to run. The "toybox" multiplexer command also lives here. (This is the 331only command defined outside of the toys directory.)</p> 332 333<p>Execution starts in main() which trims any path off of the first command 334name and calls toybox_main(), which calls toy_exec(), which calls toy_find() 335and toy_init() before calling the appropriate command's function from 336toy_list[] (via toys.which->toy_main()). 337If the command is "toybox", execution recurses into toybox_main(), otherwise 338the call goes to the appropriate commandname_main() from a C file in the toys 339directory.</p> 340 341<p>The following global variables are defined in main.c:</p> 342<ul> 343<a name="toy_list" /> 344<li><p><b>struct toy_list toy_list[]</b> - array describing all the 345commands currently configured into toybox. The first entry (toy_list[0]) is 346for the "toybox" multiplexer command, which runs all the other built-in commands 347without symlinks by using its first argument as the name of the command to 348run and the rest as that command's argument list (ala "./toybox echo hello"). 349The remaining entries are the commands in alphabetical order (for efficient 350binary search).</p> 351 352<p>This is a read-only array initialized at compile time by 353defining macros and #including generated/newtoys.h.</p> 354 355<p>Members of struct toy_list (defined in "toys.h") include:</p> 356<ul> 357<li><p>char *<b>name</b> - the name of this command.</p></li> 358<li><p>void (*<b>toy_main</b>)(void) - function pointer to run this 359command.</p></li> 360<li><p>char *<b>options</b> - command line option string (used by 361get_optflags() in lib/args.c to intialize toys.optflags, toys.optargs, and 362entries in the toy's GLOBALS struct). When this is NULL, no option 363parsing is done before calling toy_main().</p></li> 364<li><p>int <b>flags</b> - Behavior flags for this command. The following flags are currently understood:</p> 365 366<ul> 367<li><b>TOYFLAG_USR</b> - Install this command under /usr</li> 368<li><b>TOYFLAG_BIN</b> - Install this command under /bin</li> 369<li><b>TOYFLAG_SBIN</b> - Install this command under /sbin</li> 370<li><b>TOYFLAG_NOFORK</b> - This command can be used as a shell builtin.</li> 371<li><b>TOYFLAG_UMASK</b> - Call umask(0) before running this command.</li> 372<li><b>TOYFLAG_STAYROOT</b> - Don't drop permissions for this command if toybox is installed SUID root.</li> 373<li><b>TOYFLAG_NEEDROOT</b> - This command cannot function unless run with root access.</li> 374</ul> 375<br> 376 377<p>These flags are combined with | (or). For example, to install a command 378in /usr/bin, or together TOYFLAG_USR|TOYFLAG_BIN.</p> 379</ul> 380</li> 381 382<li><p><b>struct toy_context toys</b> - global structure containing information 383common to all commands, initializd by toy_init() and defined in "toys.h". 384Members of this structure include:</p> 385<ul> 386<li><p>struct toy_list *<b>which</b> - a pointer to this command's toy_list 387structure. Mostly used to grab the name of the running command 388(toys->which.name).</p> 389</li> 390<li><p>int <b>exitval</b> - Exit value of this command. Defaults to zero. The 391error_exit() functions will return 1 if this is zero, otherwise they'll 392return this value.</p></li> 393<li><p>char **<b>argv</b> - "raw" command line options, I.E. the original 394unmodified string array passed in to main(). Note that modifying this changes 395"ps" output, and is not recommended. This array is null terminated; a NULL 396entry indicates the end of the array.</p> 397<p>Most commands don't use this field, instead the use optargs, optflags, 398and the fields in the GLOBALS struct initialized by get_optflags().</p> 399</li> 400<li><p>unsigned <b>optflags</b> - Command line option flags, set by 401<a href="#lib_args">get_optflags()</a>. Indicates which of the command line options listed in 402toys->which.options occurred this time.</p> 403 404<p>The rightmost command line argument listed in toys->which.options sets bit 4051, the next one sets bit 2, and so on. This means the bits are set in the same 406order the binary digits would be listed if typed out as a string. For example, 407the option string "abcd" would parse the command line "-c" to set optflags to 2, 408"-a" would set optflags to 8, and "-bd" would set optflags to 6 (4|2).</p> 409 410<p>Only letters are relevant to optflags. In the string "a*b:c#d", d=1, c=2, 411b=4, a=8. Punctuation after a letter initializes global variables at the 412start of the GLOBALS() block (see <a href="#toy_union">union toy_union this</a> 413for details).</p> 414 415<p>The build infrastructure creates FLAG_ macros for each option letter, 416corresponding to the bit position, so you can check (toys.optflags & FLAG_x) 417to see if a flag was specified. (The correct set of FLAG_ macros is selected 418by defining FOR_mycommand before #including toys.h. The macros live in 419toys/globals.h which is generated by scripts/make.sh.)</p> 420 421<p>For more information on option parsing, see <a href="#lib_args">get_optflags()</a>.</p> 422 423</li> 424<li><p>char **<b>optargs</b> - Null terminated array of arguments left over 425after get_optflags() removed all the ones it understood. Note: optarg[0] is 426the first argument, not the command name. Use toys.which->name for the command 427name.</p></li> 428<li><p>int <b>optc</b> - Optarg count, equivalent to argc but for 429optargs[].<p></li> 430</ul> 431 432<a name="toy_union" /> 433<li><p><b>union toy_union this</b> - Union of structures containing each 434command's global variables.</p> 435 436<p>Global variables are useful: they reduce the overhead of passing extra 437command line arguments between functions, they conveniently start prezeroed to 438save initialization costs, and the command line argument parsing infrastructure 439can also initialize global variables with its results.</p> 440 441<p>But since each toybox process can only run one command at a time, allocating 442space for global variables belonging to other commands you aren't currently 443running would be wasteful.</p> 444 445<p>Toybox handles this by encapsulating each command's global variables in 446a structure, and declaring a union of those structures with a single global 447instance (called "this"). The GLOBALS() macro contains the global 448variables that should go in the current command's global structure. Each 449variable can then be accessed as "this.commandname.varname". 450If you #defined FOR_commandname before including toys.h, the macro TT is 451#defined to this.commandname so the variable can then be accessed as 452"TT.variable". See toys/hello.c for an example.</p> 453 454<p>A command that needs global variables should declare a structure to 455contain them all, and add that structure to this union. A command should never 456declare global variables outside of this, because such global variables would 457allocate memory when running other commands that don't use those global 458variables.</p> 459 460<p>The first few fields of this structure can be intialized by <a href="#lib_args">get_optargs()</a>, 461as specified by the options field off this command's toy_list entry. See 462the get_optargs() description in lib/args.c for details.</p> 463</li> 464 465<li><b>char toybuf[4096]</b> - a common scratch space buffer guaranteed 466to start zeroed, so commands don't need to allocate/initialize their own. 467Any command is free to use this, and it should never be directly referenced 468by functions in lib/ (although commands are free to pass toybuf in to a 469library function as an argument).</li> 470 471<li><b>char libbuf[4096]</b> - like toybuf, but for use by common code in 472lib/*.c. Commands should never directly reference libbuf, and library 473could should nnever directly reference toybuf.</li> 474</ul> 475 476<p>The following functions are defined in main.c:</p> 477<ul> 478<li><p>struct toy_list *<b>toy_find</b>(char *name) - Return the toy_list 479structure for this command name, or NULL if not found.</p></li> 480<li><p>void <b>toy_init</b>(struct toy_list *which, char *argv[]) - fill out 481the global toys structure, calling get_optargs() if necessary.</p></li> 482<li><p>void <b>toy_exec</b>(char *argv[]) - Run a built-in command with 483arguments.</p> 484<p>Calls toy_find() on argv[0] (which must be just a command name 485without path). Returns if it can't find this command, otherwise calls 486toy_init(), toys->which.toy_main(), and exit() instead of returning.</p> 487 488<p>Use the library function xexec() to fall back to external executables 489in $PATH if toy_exec() can't find a built-in command. Note that toy_exec() 490does not strip paths before searching for a command, so "./command" will 491never match an internal command.</li> 492 493<li><p>void <b>toybox_main</b>(void) - the main function for the multiplexer 494command (I.E. "toybox"). Given a command name as its first argument, calls 495toy_exec() on its arguments. With no arguments, it lists available commands. 496If the first argument starts with "-" it lists each command with its default 497install path prepended.</p></li> 498 499</ul> 500 501<h3>Config.in</h3> 502 503<p>Top level configuration file in a stylized variant of 504<a href=http://kernel.org/doc/Documentation/kbuild/kconfig-language.txt>kconfig</a> format. Includes generated/Config.in.</p> 505 506<p>These files are directly used by "make menuconfig" to select which commands 507to build into toybox (thus generating a .config file), and by 508scripts/config2help.py to create generated/help.h.</p> 509 510<a name="generated" /> 511<h1><a href="#generated">Temporary files:</a></h1> 512 513<p>There is one temporary file in the top level source directory:</p> 514<ul> 515<li><p><b>.config</b> - Configuration file generated by kconfig, indicating 516which commands (and options to commands) are currently enabled. Used 517to make generated/config.h and determine which toys/*/*.c files to build.</p> 518 519<p>You can create a human readable "miniconfig" version of this file using 520<a href=http://landley.net/aboriginal/new_platform.html#miniconfig>these 521instructions</a>.</p> 522</li> 523</ul> 524 525<p><h2>Directory generated/</h2></p> 526 527<p>The remaining temporary files live in the "generated/" directory, 528which is for files generated at build time from other source files.</p> 529 530<ul> 531<li><p><b>generated/Config.in</b> - Kconfig entries for each command, included 532from the top level Config.in. The help text here is used to generate 533help.h.</p> 534 535<p>Each command has a configuration entry with an upper case version of 536the command name. Options to commands start with the command 537name followed by an underscore and the option name. Global options are attached 538to the "toybox" command, and thus use the prefix "TOYBOX_". This organization 539is used by scripts/cfg2files to select which toys/*/*.c files to compile for a 540given .config.</p> 541</li> 542 543<li><p><b>generated/config.h</b> - list of CFG_SYMBOL and USE_SYMBOL() macros, 544generated from .config by a sed invocation in scripts/make.sh.</p> 545 546<p>CFG_SYMBOL is a comple time constant set to 1 for enabled symbols and 0 for 547disabled symbols. This allows the use of normal if() statements to remove 548code at compile time via the optimizer's dead code elimination (which removes 549from the binary any code that cannot be reached). This saves space without 550cluttering the code with #ifdefs or leading to configuration dependent build 551breaks. (See the 1992 Usenix paper 552<a href=http://doc.cat-v.org/henry_spencer/ifdef_considered_harmful.pdf>#ifdef 553Considered Harmful</a> for more information.)</p> 554 555<p>When you can't entirely avoid an #ifdef, the USE_SYMBOL(code) macro 556provides a less intrusive alternative, evaluating to the code in parentheses 557when the symbol is enabled, and nothing when the symbol is disabled. This 558is most commonly used around NEWTOY() declarations (so only the enabled 559commands show up in toy_list), and in option strings. This can also be used 560for things like varargs or structure members which can't always be 561eliminated by a simple test on CFG_SYMBOL. Remember, unlike CFG_SYMBOL 562this is really just a variant of #ifdef, and can still result in configuration 563dependent build breaks. Use with caution.</p> 564</li> 565 566<li><p><b>generated/flags.h</b> - FLAG_? macros indicating which command 567line options were seen. The option parsing in lib/args.c sets bits in 568toys.optflags, which can be tested by anding with the appropriate FLAG_ 569macro. (Bare longopts, which have no corresponding short option, will 570have the longopt name after FLAG_. All others use the single letter short 571option.)</p> 572 573<p>To get the appropriate macros for your command, #define FOR_commandname 574before #including toys.h. To switch macro sets (because you have an OLDTOY() 575with different options in the same .c file), #define CLEANUP_oldcommand 576and also #define FOR_newcommand, then #include "generated/flags.h" to switch. 577</p> 578</li> 579 580<li><p><b>generated/globals.h</b> - 581Declares structures to hold the contents of each command's GLOBALS(), 582and combines them into "global_union this". (Yes, the name was 583chosen to piss off C++ developers who think that C 584is merely a subset of C++, not a language in its own right.)</p> 585 586<p>The union reuses the same memory for each command's global struct: 587since only one command's globals are in use at any given time, collapsing 588them together saves space. The headers #define TT to the appropriate 589"this.commandname", so you can refer to the current command's global 590variables out of "this" as TT.variablename.</p> 591 592<p>The globals start zeroed, and the first few are filled out by the 593lib/args.c argument parsing code called from main.c.</p> 594</li> 595 596<li><p><b>toys/help.h</b> - Help strings for use by the "help" command and 597--help options. This file #defines a help_symbolname string for each 598symbolname, but only the symbolnames matching command names get used 599by show_help() in lib/help.c to display help for commands.</p> 600 601<p>This file is created by scripts/make.sh, which compiles scripts/config2help.c 602into the binary generated/config2help, and then runs it against the top 603level .config and Config.in files to extract the help text from each config 604entry and collate together dependent options.</p> 605 606<p>This file contains help text for all commands, regardless of current 607configuration, but only the ones currently enabled in the .config file 608wind up in the help_data[] array, and only the enabled dependent options 609have their help text added to the command they depend on.</p> 610</li> 611 612<li><p><b>generated/newtoys.h</b> - 613All the NEWTOY() and OLDTOY() macros from toys/*/*.c. The "toybox" multiplexer 614is the first entry, the rest are in alphabetical order. Each line should be 615inside an appropriate USE_ macro, so code that #includes this file only sees 616the currently enabled commands.</p> 617 618<p>By #definining NEWTOY() to various things before #including this file, 619it may be used to create function prototypes (in toys.h), initialize the 620help_data array (in lib/help.c), initialize the toy_list array (in main.c, 621the alphabetical order lets toy_find() do a binary search, the exception to 622the alphabetical order lets it use the multiplexer without searching), and so 623on. (It's even used to initialize the NEED_OPTIONS macro, which produces a 1 624or 0 for each command using command line option parsing, which is ORed together 625to allow compile-time dead code elimination to remove the whole of 626lib/args.c if nothing currently enabled is using it.)<p> 627 628<p>Each NEWTOY and OLDTOY macro contains the command name, command line 629option string (telling lib/args.c how to parse command line options for 630this command), recommended install location, and miscelaneous data such 631as whether this command should retain root permissions if installed suid.</p> 632</li> 633 634<li><p><b>toys/oldtoys.h</b> - Macros with the command line option parsing 635string for each NEWTOY. This allows an OLDTOY that's just an alias for an 636existing command to refer to the existing option string instead of 637having to repeat it.</p> 638</li> 639</ul> 640 641<a name="lib"> 642<h2>Directory lib/</h2> 643 644<p>TODO: document lots more here.</p> 645 646<p>lib: getmountlist(), error_msg/error_exit, xmalloc(), 647strlcpy(), xexec(), xopen()/xread(), xgetcwd(), xabspath(), find_in_path(), 648itoa().</p> 649 650 651 652<a name="lib_xwrap"><h3>lib/xwrap.c</h3> 653 654<p>Functions prefixed with the letter x call perror_exit() when they hit 655errors, to eliminate common error checking. This prints an error message 656and the strerror() string for the errno encountered.</p> 657 658<p>We replaced exit(), _exit(), and atexit() with xexit(), _xexit(), and 659sigatexit(). This gives _xexit() the option to siglongjmp(toys.rebound, 1) 660instead of exiting, lets xexit() report stdout flush failures to stderr 661and change the exit code to indicate error, lets our toys.exit function 662change happen for signal exit paths and lets us remove the functions 663after we've called them.</p> 664 665<p>You can intercept our exit by assigning a sigsetjmp/siglongjmp buffer to 666toys.rebound (set it back to zero to restore the default behavior). 667If you do this, cleaning up resource leaks is your problem.</p> 668 669<ul> 670<li><b>void xstrncpy(char *dest, char *src, size_t size)</b></li> 671<li><p><b><p>void _xexit(void)</b></p> 672<p>Calls siglongjmp(toys.rebound, 1), or else _exit(toys.exitval). This 673lets you ignore errors with the NO_EXIT() macro wrapper, or intercept 674them with WOULD_EXIT().</p> 675<li><b><p>void xexit(void)</b></p> 676<p>Calls toys.xexit functions (if any) and flushes stdout/stderr (reporting 677failure to write to stdout both to stderr and in the exit code), then 678calls _xexit().</p> 679</li> 680<li><b>void *xmalloc(size_t size)</b></li> 681<li><b>void *xzalloc(size_t size)</b></li> 682<li><b>void *xrealloc(void *ptr, size_t size)</b></li> 683<li><b>char *xstrndup(char *s, size_t n)</b></li> 684<li><b>char *xstrdup(char *s)</b></li> 685<li><b>char *xmprintf(char *format, ...)</b></li> 686<li><b>void xprintf(char *format, ...)</b></li> 687<li><b>void xputs(char *s)</b></li> 688<li><b>void xputc(char c)</b></li> 689<li><b>pid_t xfork(void)</b></li> 690<li><b>void xexec_optargs(int skip)</b></li> 691<li><b>void xexec(char **argv)</b></li> 692<li><b>pid_t xpopen(char **argv, int *pipes)</b></li> 693<li><b>int xpclose(pid_t pid, int *pipes)</b></li> 694<li><b>void xaccess(char *path, int flags)</b></li> 695<li><b>void xunlink(char *path)</b></li> 696<li><p><b>int xcreate(char *path, int flags, int mode)<br /> 697int xopen(char *path, int flags)</b></p> 698 699<p>The xopen() and xcreate() functions open an existing file (exiting if 700it's not there) and create a new file (exiting if it can't).</p> 701 702<p>They default to O_CLOEXEC so the filehandles aren't passed on to child 703processes. Feed in O_CLOEXEC to disable this.</p> 704</li> 705<li><p><b>void xclose(int fd)</b></p> 706 707<p>Because NFS is broken, and won't necessarily perform the requested 708operation (and report the error) until you close the file. Of course, this 709being NFS, it's not guaranteed to report the error there either, but it 710_can_.</p> 711 712<p>Nothing else ever reports an error on close, everywhere else it's just a 713VFS operation freeing some resources. NFS is _special_, in a way that 714other network filesystems like smbfs and v9fs aren't..</p> 715</li> 716<li><b>int xdup(int fd)</b></li> 717<li><p><b>size_t xread(int fd, void *buf, size_t len)</b></p> 718 719<p>Can return 0, but not -1.</p> 720</li> 721<li><p><b>void xreadall(int fd, void *buf, size_t len)</b></p> 722 723<p>Reads the entire len-sized buffer, retrying to complete short 724reads. Exits if it can't get enough data.</p></li> 725 726<li><p><b>void xwrite(int fd, void *buf, size_t len)</b></p> 727 728<p>Retries short writes, exits if can't write the entire buffer.</p></li> 729 730<li><b>off_t xlseek(int fd, off_t offset, int whence)</b></li> 731<li><b>char *xgetcwd(void)</b></li> 732<li><b>void xstat(char *path, struct stat *st)</b></li> 733<li><p><b>char *xabspath(char *path, int exact) </b></p> 734 735<p>After several years of 736<a href=http://landley.net/notes-2007.html#18-06-2007>wrestling</a> 737<a href=http://landley.net/notes-2008.html#19-01-2008>with</a> realpath(), 738I broke down and <a href=http://landley.net/notes-2012.html#20-11-2012>wrote 739my own</a> implementation that doesn't use the one in libc. As I explained: 740 741<blockquote><p>If the path ends with a broken link, 742readlink -f should show where the link points to, not where the broken link 743lives. (The point of readlink -f is "if I write here, where would it attempt 744to create a file".) The problem is, realpath() returns NULL for a path ending 745with a broken link, and I can't beat different behavior out of code locked 746away in libc.</p></blockquote> 747 748<p> 749</li> 750<li><b>void xchdir(char *path)</b></li> 751<li><b>void xchroot(char *path)</b></li> 752 753<li><p><b>struct passwd *xgetpwuid(uid_t uid)<br /> 754struct group *xgetgrgid(gid_t gid)<br /> 755struct passwd *xgetpwnam(char *name)</b></p> 756</li> 757 758<li><b>void xsetuser(struct passwd *pwd)</b></li> 759<li><b>char *xreadlink(char *name)</b></li> 760<li><b>char *xreadfile(char *name, char *buf, off_t len)</b></li> 761<li><b>int xioctl(int fd, int request, void *data)</b></li> 762<li><b>void xpidfile(char *name)</b></li> 763<li><b>void xsendfile(int in, int out)</b></li> 764<li><b>long xparsetime(char *arg, long units, long *fraction)</b></li> 765<li><b>void xregcomp(regex_t *preg, char *regex, int cflags)</b></li> 766</ul> 767 768<a name="lib_lib"><h3>lib/lib.c</h3> 769<p>Eight gazillion common functions, see lib/lib.h for the moment:</p> 770 771<h3>lib/portability.h</h3> 772 773<p>This file is automatically included from the top of toys.h, and smooths 774over differences between platforms (hardware targets, compilers, C libraries, 775operating systems, etc).</p> 776 777<p>This file provides SWAP macros (SWAP_BE16(x) and SWAP_LE32(x) and so on).</p> 778 779<p>A macro like SWAP_LE32(x) means "The value in x is stored as a little 780endian 32 bit value, so perform the translation to/from whatever the native 78132-bit format is". You do the swap once on the way in, and once on the way 782out. If your target is already little endian, the macro is a NOP.</p> 783 784<p>The SWAP macros come in BE and LE each with 16, 32, and 64 bit versions. 785In each case, the name of the macro refers to the _external_ representation, 786and converts to/from whatever your native representation happens to be (which 787can vary depending on what you're currently compiling for).</p> 788 789<a name="lib_llist"><h3>lib/llist.c</h3> 790 791<p>Some generic single and doubly linked list functions, which take 792advantage of a couple properties of C:</p> 793 794<ul> 795<li><p>Structure elements are laid out in memory in the order listed, and 796the first element has no padding. This means you can always treat (typecast) 797a pointer to a structure as a pointer to the first element of the structure, 798even if you don't know anything about the data following it.</p></li> 799 800<li><p>An array of length zero at the end of a structure adds no space 801to the sizeof() the structure, but if you calculate how much extra space 802you want when you malloc() the structure it will be available at the end. 803Since C has no bounds checking, this means each struct can have one variable 804length array.</p></li> 805</ul> 806 807<p>Toybox's list structures always have their <b>next</b> pointer as 808the first entry of each struct, and singly linked lists end with a NULL pointer. 809This allows generic code to traverse such lists without knowing anything 810else about the specific structs composing them: if your pointer isn't NULL 811typecast it to void ** and dereference once to get the next entry.</p> 812 813<p><b>lib/lib.h</b> defines three structure types:</p> 814<ul> 815<li><p><b>struct string_list</b> - stores a single string (<b>char str[0]</b>), 816memory for which is allocated as part of the node. (I.E. llist_traverse(list, 817free); can clean up after this type of list.)</p></li> 818 819<li><p><b>struct arg_list</b> - stores a pointer to a single string 820(<b>char *arg</b>) which is stored in a separate chunk of memory.</p></li> 821 822<li><p><b>struct double_list</b> - has a second pointer (<b>struct double_list 823*prev</b> along with a <b>char *data</b> for payload.</p></li> 824</ul> 825 826<b>List Functions</b> 827 828<ul> 829<li><p>void *<b>llist_pop</b>(void **list) - advances through a list ala 830<b>node = llist_pop(&list);</b> This doesn't modify the list contents, 831but does advance the pointer you feed it (which is why you pass the _address_ 832of that pointer, not the pointer itself).</p></li> 833 834<li><p>void <b>llist_traverse</b>(void *list, void (*using)(void *data)) - 835iterate through a list calling a function on each node.</p></li> 836 837<li><p>struct double_list *<b>dlist_add</b>(struct double_list **llist, char *data) 838- append an entry to a circular linked list. 839This function allocates a new struct double_list wrapper and returns the 840pointer to the new entry (which you can usually ignore since it's llist->prev, 841but if llist was NULL you need it). The argument is the ->data field for the 842new node.</p></li> 843<ul><li><p>void <b>dlist_add_nomalloc</b>(struct double_list **llist, 844struct double_list *new) - append existing struct double_list to 845list, does not allocate anything.</p></li></ul> 846</ul> 847 848<b>List code trivia questions:</b> 849 850<ul> 851<li><p><b>Why do arg_list and double_list contain a char * payload instead of 852a void *?</b> - Because you always have to typecast a void * to use it, and 853typecasting a char * does no harm. Since strings are the most common 854payload, and doing math on the pointer ala 855"(type *)(ptr+sizeof(thing)+sizeof(otherthing))" requires ptr to be char * 856anyway (at least according to the C standard), defaulting to char * saves 857a typecast.</p> 858</li> 859 860<li><p><b>Why do the names ->str, ->arg, and ->data differ?</b> - To force 861you to keep track of which one you're using, calling free(node->str) would 862be bad, and _failing_ to free(node->arg) leaks memory.</p></li> 863 864<li><p><b>Why does llist_pop() take a void * instead of void **?</b> - 865because the stupid compiler complains about "type punned pointers" when 866you typecast and dereference on the same line, 867due to insane FSF developers hardwiring limitations of their optimizer 868into gcc's warning system. Since C automatically typecasts any other 869pointer type to and from void *, the current code works fine. It's sad that it 870won't warn you if you forget the &, but the code crashes pretty quickly in 871that case.</p></li> 872 873<li><p><b>How do I assemble a singly-linked-list in order?</b> - use 874a double_list, dlist_add() your entries, and then call dlist_terminate(list) 875to break the circle when done (turning the last ->next and the first ->prev 876into NULLs).</p> 877</ul> 878 879<a name="lib_args"><h3>lib/args.c</h3> 880 881<p>Toybox's main.c automatically parses command line options before calling the 882command's main function. Option parsing starts in get_optflags(), which stores 883results in the global structures "toys" (optflags and optargs) and "this".</p> 884 885<p>The option parsing infrastructure stores a bitfield in toys.optflags to 886indicate which options the current command line contained, and defines FLAG 887macros code can use to check whether each argument's bit is set. Arguments 888attached to those options are saved into the command's global structure 889("this"). Any remaining command line arguments are collected together into 890the null-terminated array toys.optargs, with the length in toys.optc. (Note 891that toys.optargs does not contain the current command name at position zero, 892use "toys.which->name" for that.) The raw command line arguments get_optflags() 893parsed are retained unmodified in toys.argv[].</p> 894 895<p>Toybox's option parsing logic is controlled by an "optflags" string, using 896a format reminiscent of getopt's optargs but with several important differences. 897Toybox does not use the getopt() 898function out of the C library, get_optflags() is an independent implementation 899which doesn't permute the original arguments (and thus doesn't change how the 900command is displayed in ps and top), and has many features not present in 901libc optargs() (such as the ability to describe long options in the same string 902as normal options).</p> 903 904<p>Each command's NEWTOY() macro has an optflags string as its middle argument, 905which sets toy_list.options for that command to tell get_optflags() what 906command line arguments to look for, and what to do with them. 907If a command has no option 908definition string (I.E. the argument is NULL), option parsing is skipped 909for that command, which must look at the raw data in toys.argv to parse its 910own arguments. (If no currently enabled command uses option parsing, 911get_optflags() is optimized out of the resulting binary by the compiler's 912--gc-sections option.)</p> 913 914<p>You don't have to free the option strings, which point into the environment 915space (I.E. the string data is not copied). A TOYFLAG_NOFORK command 916that uses the linked list type "*" should free the list objects but not 917the data they point to, via "llist_free(TT.mylist, NULL);". (If it's not 918NOFORK, exit() will free all the malloced data anyway unless you want 919to implement a CONFIG_TOYBOX_FREE cleanup for it.)</p> 920 921<h4>Optflags format string</h4> 922 923<p>Note: the optflags option description string format is much more 924concisely described by a large comment at the top of lib/args.c.</p> 925 926<p>The general theory is that letters set optflags, and punctuation describes 927other actions the option parsing logic should take.</p> 928 929<p>For example, suppose the command line <b>command -b fruit -d walrus -a 42</b> 930is parsed using the optflags string "<b>a#b:c:d</b>". (I.E. 931toys.which->options="a#b:c:d" and argv = ["command", "-b", "fruit", "-d", 932"walrus", "-a", "42"]). When get_optflags() returns, the following data is 933available to command_main(): 934 935<ul> 936<li><p>In <b>struct toys</b>: 937<ul> 938<li>toys.optflags = 13; // FLAG_a = 8 | FLAG_b = 4 | FLAG_d = 1</li> 939<li>toys.optargs[0] = "walrus"; // leftover argument</li> 940<li>toys.optargs[1] = NULL; // end of list</li> 941<li>toys.optc = 1; // there was 1 leftover argument</li> 942<li>toys.argv[] = {"-b", "fruit", "-d", "walrus", "-a", "42"}; // The original command line arguments 943</ul> 944<p></li> 945 946<li><p>In <b>union this</b> (treated as <b>long this[]</b>): 947<ul> 948<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> 949<li>this[1] = (long)"fruit"; // argument to -b</li> 950<li>this[2] = 42; // argument to -a</li> 951</ul> 952</p></li> 953</ul> 954 955<p>If the command's globals are:</p> 956 957<blockquote><pre> 958GLOBALS( 959 char *c; 960 char *b; 961 long a; 962) 963</pre></blockquote> 964 965<p>That would mean TT.c == NULL, TT.b == "fruit", and TT.a == 42. (Remember, 966each entry that receives an argument must be a long or pointer, to line up 967with the array position. Right to left in the optflags string corresponds to 968top to bottom in GLOBALS().</p> 969 970<p>Put globals not filled out by the option parsing logic at the end of the 971GLOBALS block. Common practice is to list the options one per line (to 972make the ordering explicit, first to last in globals corresponds to right 973to left in the option string), then leave a blank line before any non-option 974globals.</p> 975 976<p><b>long toys.optflags</b></p> 977 978<p>Each option in the optflags string corresponds to a bit position in 979toys.optflags, with the same value as a corresponding binary digit. The 980rightmost argument is (1<<0), the next to last is (1<<1) and so on. If 981the option isn't encountered while parsing argv[], its bit remains 0.</p> 982 983<p>Each option -x has a FLAG_x macro for the command letter. Bare --longopts 984with no corresponding short option have a FLAG_longopt macro for the long 985optionname. Commands enable these macros by #defining FOR_commandname before 986#including <toys.h>. When multiple commands are implemented in the same 987source file, you can switch flag contexts later in the file by 988#defining CLEANUP_oldcommand and #defining FOR_newcommand, then 989#including <generated/flags.h>.</p> 990 991<p>Options disabled in the current configuration (wrapped in 992a USE_BLAH() macro for a CONFIG_BLAH that's switched off) have their 993corresponding FLAG macro set to zero, so code checking them ala 994if (toys.optargs & FLAG_x) gets optimized out via dead code elimination. 995#defining FORCE_FLAGS when switching flag context disables this 996behavior: the flag is never zero even if the config is disabled. This 997allows code shared between multiple commands to use the same flag 998values, as long as the common flags match up right to left in both option 999strings.</p> 1000
1001<p>For example, 1002the optflags string "abcd" would parse the command line argument "-c" to set 1003optflags to 2, "-a" would set optflags to 8, "-bd" would set optflags to 10046 (I.E. 4|2), and "-a -c" would set optflags to 10 (2|8). To check if -c 1005was encountered, code could test: if (toys.optflags & FLAG_c) printf("yup"); 1006(See the toys/examples directory for more.)</p> 1007 1008<p>Only letters are relevant to optflags, punctuation is skipped: in the 1009string "a*b:c#d", d=1, c=2, b=4, a=8. The punctuation after a letter 1010usually indicate that the option takes an argument.</p> 1011 1012<p>Since toys.optflags is an unsigned int, it only stores 32 bits. (Which is 1013the amount a long would have on 32-bit platforms anyway; 64 bit code on 101432 bit platforms is too expensive to require in common code used by almost 1015all commands.) Bit positions beyond the 1<<31 aren't recorded, but 1016parsing higher options can still set global variables.</p> 1017 1018<p><b>Automatically setting global variables from arguments (union this)</b></p> 1019 1020<p>The following punctuation characters may be appended to an optflags 1021argument letter, indicating the option takes an additional argument:</p> 1022 1023<ul> 1024<li><b>:</b> - plus a string argument, keep most recent if more than one.</li> 1025<li><b>*</b> - plus a string argument, appended to a linked list.</li> 1026<li><b>@</b> - plus an occurrence counter (stored in a long)</li> 1027<li><b>#</b> - plus a signed long argument. 1028<li><b>-</b> - plus a signed long argument defaulting to negative (start argument with + to force a positive value).</li> 1029<li><b>.</b> - plus a floating point argument (if CFG_TOYBOX_FLOAT).</li> 1030<ul>The following can be appended to a float or double: 1031<li><b><123</b> - error if argument is less than this</li> 1032<li><b>>123</b> - error if argument is greater than this</li> 1033<li><b>=123</b> - default value if argument not supplied</li> 1034</ul> 1035</ul> 1036 1037<p><b>GLOBALS</b></p> 1038 1039<p>Options which have an argument fill in the corresponding slot in the global 1040union "this" (see generated/globals.h), treating it as an array of longs 1041with the rightmost saved in this[0]. As described above, using "a*b:c#d", 1042"-c 42" would set this[0] = 42; and "-b 42" would set this[1] = "42"; each 1043slot is left NULL if the corresponding argument is not encountered.</p> 1044 1045<p>This behavior is useful because the LP64 standard ensures long and pointer 1046are the same size. C99 guarantees structure members will occur in memory 1047in the same order they're declared, and that padding won't be inserted between 1048consecutive variables of register size. Thus the first few entries can 1049be longs or pointers corresponding to the saved arguments.</p> 1050 1051<p>The main downside is that numeric arguments ("#" and "-" format) 1052are limited to +- 2 billion on 32 bit platforms (the "truncate -s 8G" 1053problem), because long is only 64 bits on 64 bit hosts, so the capabilities 1054of some tools differ when built in 32 bit vs 64 bit mode. Fixing this 1055kind of ugly and even embedded designs are slowly moving to 64 bits, 1056so our current plan is to document the problem and wait it out. (If 1057"x32 mode" and similar becomes popular enough, we may revisit this 1058decision.)</p> 1059 1060<p>See toys/example/*.c for longer examples of parsing options into the 1061GLOBALS block.</p> 1062 1063<p><b>char *toys.optargs[]</b></p> 1064 1065<p>Command line arguments in argv[] which are not consumed by option parsing 1066(I.E. not recognized either as -flags or arguments to -flags) will be copied 1067to toys.optargs[], with the length of that array in toys.optc. 1068(When toys.optc is 0, no unrecognized command line arguments remain.) 1069The order of entries is preserved, and as with argv[] this new array is also 1070terminated by a NULL entry.</p> 1071 1072<p>Option parsing can require a minimum or maximum number of optargs left 1073over, by adding "<1" (read "at least one") or ">9" ("at most nine") to the 1074start of the optflags string.</p> 1075 1076<p>The special argument "--" terminates option parsing, storing all remaining 1077arguments in optargs. The "--" itself is consumed.</p> 1078 1079<p><b>Other optflags control characters</b></p> 1080 1081<p>The following characters may occur at the start of each command's 1082optflags string, before any options that would set a bit in toys.optflags:</p> 1083 1084<ul> 1085<li><b>^</b> - stop at first nonoption argument (for nice, xargs...)</li> 1086<li><b>?</b> - allow unknown arguments (pass non-option arguments starting 1087with - through to optargs instead of erroring out).</li> 1088<li><b>&</b> - the first argument has imaginary dash (ala tar/ps. If given twice, all arguments have imaginary dash.)</li> 1089<li><b><</b> - must be followed by a decimal digit indicating at least this many leftover arguments are needed in optargs (default 0)</li> 1090<li><b>></b> - must be followed by a decimal digit indicating at most this many leftover arguments allowed (default MAX_INT)</li> 1091</ul> 1092 1093<p>The following characters may be appended to an option character, but do 1094not by themselves indicate an extra argument should be saved in this[]. 1095(Technically any character not recognized as a control character sets an 1096optflag, but letters are never control characters.)</p> 1097 1098<ul> 1099<li><b>^</b> - stop parsing options after encountering this option, everything else goes into optargs.</li> 1100<li><b>|</b> - this option is required. If more than one marked, only one is required.</li> 1101</ul> 1102 1103<p>The following may be appended to a float or double:</p> 1104 1105<ul> 1106<li><b><123</b> - error if argument is less than this</li> 1107<li><b>>123</b> - error if argument is greater than this</li> 1108<li><b>=123</b> - default value if argument not supplied</li> 1109</ul> 1110 1111<p>Option parsing only understands <>= after . when CFG_TOYBOX_FLOAT 1112is enabled. (Otherwise the code to determine where floating point constants 1113end drops out. When disabled, it can reserve a global data slot for the 1114argument so offsets won't change, but will never fill it out.) You can handle 1115this by using the USE_BLAH() macros with C string concatenation, ala:</p> 1116 1117<blockquote>"abc." USE_TOYBOX_FLOAT("<1.23>4.56=7.89") "def"</blockquote> 1118 1119<p><b>--longopts</b></p> 1120 1121<p>The optflags string can contain long options, which are enclosed in 1122parentheses. They may be appended to an existing option character, in 1123which case the --longopt is a synonym for that option, ala "a:(--fred)" 1124which understands "-a blah" or "--fred blah" as synonyms.</p> 1125 1126<p>Longopts may also appear before any other options in the optflags string, 1127in which case they have no corresponding short argument, but instead set 1128their own bit based on position. So for "(walrus)#(blah)xy:z", "command 1129--walrus 42" would set toys.optflags = 16 (-z = 1, -y = 2, -x = 4, --blah = 8) 1130and would assign this[1] = 42;</p> 1131 1132<p>A short option may have multiple longopt synonyms, "a(one)(two)", but 1133each "bare longopt" (ala "(one)(two)abc" before any option characters) 1134always sets its own bit (although you can group them with +X).</p> 1135 1136<p>Only bare longopts have a FLAG_ macro with the longopt name 1137(ala --fred would #define FLAG_fred). Other longopts use the short 1138option's FLAG macro to test the toys.optflags bit.</p> 1139 1140<p>Options with a semicolon ";" after their data type can only set their 1141corresponding GLOBALS() entry via "--longopt=value". For example, option 1142string "x(boing): y" would set TT.x if it saw "--boing=value", but would 1143treat "--boing value" as setting FLAG_x in toys.optargs, leaving TT.x NULL, 1144and keeping "value" in toys.optargs[]. (This lets "ls --color" and 1145"ls --color=auto" both work.)</p> 1146 1147<p><b>[groups]</b></p> 1148 1149<p>At the end of the option string, square bracket groups can define 1150relationships between existing options. (This only applies to short 1151options, bare --longopts can't participate.)</p> 1152 1153<p>The first character of the group defines the type, the remaining 1154characters are options it applies to:</p> 1155 1156<ul> 1157<li><b>-</b> - Exclusive, switch off all others in this group.</li> 1158<li><b>+</b> - Inclusive, switch on all others in this group.</li> 1159<li><b>!</b> - Error, fail if more than one defined.</li> 1160</ul> 1161 1162<p>So "abc[-abc]" means -ab = -b, -ba = -a, -abc = -c. "abc[+abc]" 1163means -ab=-abc, -c=-abc, and "abc[!abc] means -ab calls error_exit("no -b 1164with -a"). Note that [-] groups clear the GLOBALS option slot of 1165options they're switching back off, but [+] won't set options it didn't see 1166(just the optflags).</p> 1167 1168<p><b>whitespace</b></p> 1169 1170<p>Arguments may occur with or without a space (I.E. "-a 42" or "-a42"). 1171The command line argument "-abc" may be interepreted many different ways: 1172the optflags string "cba" sets toys.optflags = 7, "c:ba" sets toys.optflags=4 1173and saves "ba" as the argument to -c, and "cb:a" sets optflags to 6 and saves 1174"c" as the argument to -b.</p> 1175 1176<p>Note that & changes whitespace handling, so that the command line 1177"tar cvfCj outfile.tar.bz2 topdir filename" is parsed the same as 1178"tar filename -c -v -j -f outfile.tar.bz2 -C topdir". Note that "tar -cvfCj 1179one two three" would equal "tar -c -v -f Cj one two three". (This matches 1180historical usage.)</p> 1181 1182<p>Appending a space to the option in the option string ("a: b") makes it 1183require a space, I.E. "-ab" is interpreted as "-a" "-b". That way "kill -stop" 1184differs from "kill -s top".</p> 1185 1186<p>Appending ; to a longopt in the option string makes its argument optional, 1187and only settable with =, so in ls "(color):;" can accept "ls --color" and 1188"ls --color=auto" without complaining that the first has no argument.</p> 1189 1190<a name="lib_dirtree"><h3>lib/dirtree.c</h3> 1191 1192<p>The directory tree traversal code should be sufficiently generic 1193that commands never need to use readdir(), scandir(), or the fts.h family 1194of functions.</p> 1195 1196<p>These functions do not call chdir() or rely on PATH_MAX. Instead they 1197use openat() and friends, using one filehandle per directory level to 1198recurse into subdirectories. (I.E. they can descend 1000 directories deep 1199if setrlimit(RLIMIT_NOFILE) allows enough open filehandles, and the default 1200in /proc/self/limits is generally 1024.)</p> 1201 1202<p>There are two main ways to use dirtree: 1) assemble a tree of nodes 1203representing a snapshot of directory state and traverse them using the 1204->next and ->child pointers, or 2) traverse the tree calling a callback 1205function on each entry, and freeing its node afterwards. (You can also 1206combine the two, using the callback as a filter to determine which nodes 1207to keep.)</p> 1208 1209<p>The basic dirtree functions are:</p> 1210 1211<ul> 1212<li><p><b>struct dirtree *dirtree_read(char *path, int (*callback)(struct 1213dirtree node))</b> - recursively read files and directories, calling 1214callback() on each, and returning a tree of saved nodes (if any). 1215If path doesn't exist, returns DIRTREE_ABORTVAL. If callback is NULL, 1216returns a single node at that path.</p> 1217 1218<li><p><b>dirtree_notdotdot(struct dirtree *new)</b> - standard callback 1219which discards "." and ".." entries and returns DIRTREE_SAVE|DIRTREE_RECURSE 1220for everything else. Used directly, this assembles a snapshot tree of 1221the contents of this directory and its subdirectories 1222to be processed after dirtree_read() returns (by traversing the 1223struct dirtree's ->next and ->child pointers from the returned root node).</p> 1224 1225<li><p><b>dirtree_path(struct dirtree *node, int *plen)</b> - malloc() a 1226string containing the path from the root of this tree to this node. If 1227plen isn't NULL then *plen is how many extra bytes to malloc at the end 1228of string.</p></li> 1229 1230<li><p><b>dirtree_parentfd(struct dirtree *node)</b> - return fd of 1231directory containing this node, for use with openat() and such.</p></li> 1232</ul> 1233 1234<p>The <b>dirtree_read()</b> function is the standard way to start 1235directory traversal. It takes two arguments: a starting path for 1236the root of the tree, and a callback function. The callback() is called 1237on each directory entry, its argument is a fully populated 1238<b>struct dirtree *</b> (from lib/lib.h) describing the node, and its 1239return value tells the dirtree infrastructure what to do next.</p> 1240 1241<p>(There's also a three argument version, 1242<b>dirtree_flagread(char *path, int flags, int (*callback)(struct 1243dirtree node))</b>, which lets you apply flags like DIRTREE_SYMFOLLOW and 1244DIRTREE_SHUTUP to reading the top node, but this only affects the top node. 1245Child nodes use the flags returned by callback().</p> 1246 1247<p><b>struct dirtree</b></p> 1248 1249<p>Each struct dirtree node contains <b>char name[]</b> and <b>struct stat 1250st</b> entries describing a file, plus a <b>char *symlink</b> 1251which is NULL for non-symlinks.</p> 1252 1253<p>During a callback function, the <b>int dirfd</b> field of directory nodes 1254contains a directory file descriptor (for use with the openat() family of 1255functions). This isn't usually used directly, intstead call dirtree_parentfd() 1256on the callback's node argument. The <b>char again</b> field is 0 for the 1257first callback on a node, and 1 on the second callback (triggered by returning 1258DIRTREE_COMEAGAIN on a directory, made after all children have been processed). 1259</p> 1260 1261<p>Users of this code may put anything they like into the <b>long extra</b> 1262field. For example, "cp" and "mv" use this to store a dirfd for the destination 1263directory (and use DIRTREE_COMEAGAIN to get the second callback so they can 1264close(node->extra) to avoid running out of filehandles). 1265This field is not directly used by the dirtree code, and 1266thanks to LP64 it's large enough to store a typecast pointer to an 1267arbitrary struct.</p> 1268 1269<p>The return value of the callback combines flags (with boolean or) to tell 1270the traversal infrastructure how to behave:</p> 1271 1272<ul> 1273<li><p><b>DIRTREE_SAVE</b> - Save this node, assembling a tree. (Without 1274this the struct dirtree is freed after the callback returns. Filtering out 1275siblings is fine, but discarding a parent while keeping its child leaks 1276memory.)</p></li> 1277<li><p><b>DIRTREE_ABORT</b> - Do not examine any more entries in this 1278directory. (Does not propagate up tree: to abort entire traversal, 1279return DIRTREE_ABORT from parent callbacks too.)</p></li> 1280<li><p><b>DIRTREE_RECURSE</b> - Examine directory contents. Ignored for 1281non-directory entries. The remaining flags only take effect when 1282recursing into the children of a directory.</p></li> 1283<li><p><b>DIRTREE_COMEAGAIN</b> - Call the callback on this node a second time 1284after examining all directory contents, allowing depth-first traversal. 1285On the second call, dirtree->again is nonzero.</p></li> 1286<li><p><b>DIRTREE_SYMFOLLOW</b> - follow symlinks when populating children's 1287<b>struct stat st</b> (by feeding a nonzero value to the symfollow argument of 1288dirtree_add_node()), which means DIRTREE_RECURSE treats symlinks to 1289directories as directories. (Avoiding infinite recursion is the callback's 1290problem: the non-NULL dirtree->symlink can still distinguish between 1291them. The "find" command follows ->parent up the tree to the root node 1292each time, checking to make sure that stat's dev and inode pair don't 1293match any ancestors.)</p></li> 1294</ul> 1295 1296<p>Each struct dirtree contains three pointers (next, parent, and child) 1297to other struct dirtree.</p> 1298 1299<p>The <b>parent</b> pointer indicates the directory 1300containing this entry; even when not assembling a persistent tree of 1301nodes the parent entries remain live up to the root of the tree while 1302child nodes are active. At the top of the tree the parent pointer is 1303NULL, meaning the node's name[] is either an absolute path or relative 1304to cwd. The function dirtree_parentfd() gets the directory file descriptor 1305for use with openat() and friends, returning AT_FDCWD at the top of tree.</p> 1306 1307<p>The <b>child</b> pointer points to the first node of the list of contents of 1308this directory. If the directory contains no files, or the entry isn't 1309a directory, child is NULL.</p> 1310 1311<p>The <b>next</b> pointer indicates sibling nodes in the same directory as this 1312node, and since it's the first entry in the struct the llist.c traversal 1313mechanisms work to iterate over sibling nodes. Each dirtree node is a 1314single malloc() (even char *symlink points to memory at the end of the node), 1315so llist_free() works but its callback must descend into child nodes (freeing 1316a tree, not just a linked list), plus whatever the user stored in extra.</p> 1317 1318<p>The <b>dirtree_flagread</b>() function is a simple wrapper, calling <b>dirtree_add_node</b>() 1319to create a root node relative to the current directory, then calling 1320<b>dirtree_handle_callback</b>() on that node (which recurses as instructed by the callback 1321return flags). The flags argument primarily lets you 1322control whether or not to follow symlinks to the root node; symlinks 1323listed on the command line are often treated differently than symlinks 1324encountered during recursive directory traversal. 1325 1326<p>The ls command not only bypasses this wrapper, but never returns 1327<b>DIRTREE_RECURSE</b> from the callback, instead calling <b>dirtree_recurse</b>() manually 1328from elsewhere in the program. This gives ls -lR manual control 1329of traversal order, which is neither depth first nor breadth first but 1330instead a sort of FIFO order requried by the ls standard.</p> 1331 1332<a name="toys"> 1333<h1><a href="#toys">Directory toys/</a></h1> 1334 1335<p>This directory contains command implementations. Each command is a single 1336self-contained file. Adding a new command involves adding a single 1337file, and removing a command involves removing that file. Commands use 1338shared infrastructure from the lib/ and generated/ directories.</p> 1339 1340<p>Currently there are five subdirectories under "toys/" containing "posix" 1341commands described in POSIX-2008, "lsb" commands described in the Linux 1342Standard Base 4.1, "other" commands not described by either standard, 1343"pending" commands awaiting cleanup (which default to "n" in menuconfig 1344because they don't necessarily work right yet), and "example" code showing 1345how toybox infrastructure works and providing template/skeleton files to 1346start new commands.</p> 1347 1348<p>The only difference directory location makes is which menu the command 1349shows up in during "make menuconfig", the directories are otherwise identical. 1350Note that the commands exist within a single namespace at runtime, so you can't 1351have the same command in multiple subdirectories. (The build tries to fail 1352informatively when you do that.)</p> 1353 1354<p>There is one more sub-menus in "make menuconfig" containing global 1355configuration options for toybox. This menu is defined in the top level 1356Config.in.</p> 1357 1358<p>See <a href="#adding">adding a new command</a> for details on the 1359layout of a command file.</p> 1360 1361<a name="scripts"> 1362<h2>Directory scripts/</h2> 1363 1364<p>Build infrastructure. The makefile calls scripts/make.sh for "make" 1365and scripts/install.sh for "make install".</p> 1366 1367<p>There's also a test suite, "make test" calls make/test.sh, which runs all 1368the tests in make/test/*. You can run individual tests via 1369"scripts/test.sh command", or "TEST_HOST=1 scripts/test.sh command" to run 1370that test against the host implementation instead of the toybox one.</p> 1371 1372<h3>scripts/cfg2files.sh</h3> 1373 1374<p>Run .config through this filter to get a list of enabled commands, which 1375is turned into a list of files in toys via a sed invocation in the top level 1376Makefile. 1377</p> 1378 1379<h2>Directory kconfig/</h2> 1380 1381<p>Menuconfig infrastructure copied from the Linux kernel a long time ago 1382(version 2.6.16). See the 1383Linux kernel's Documentation/kbuild/kconfig-language.txt</p> 1384 1385<!-- todo 1386 1387Better OLDTOY and multiple command explanation. From Config.in: 1388 1389<p>A command with multiple names (or multiple similar commands implemented in 1390the same .c file) should have config symbols prefixed with the name of their 1391C file. I.E. config symbol prefixes are NEWTOY() names. If OLDTOY() names 1392have config symbols they must be options (symbols with an underscore and 1393suffix) to the NEWTOY() name. (See generated/toylist.h)</p> 1394--> 1395 1396<!--#include file="footer.html" --> 1397