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1 files changed, 298 insertions, 33 deletions
diff --git a/www/code.html b/www/code.html index 531539de..541b1019 100644 --- a/www/code.html +++ b/www/code.html @@ -18,7 +18,7 @@ to spot as overrides to the normal flow of control, which they are.</p> <p>The primary goal of toybox is _simple_ code. Small is second, speed and lots of features come in somewhere after that. Note that environmental dependencies are a type of complexity, so needing other packages -to build or run is a downside. For example, don't use curses when you can +to build or run is a big downside. For example, don't use curses when you can output ansi escape sequences instead.</p> <p><h1>Infrastructure:</h1></p> @@ -70,18 +70,27 @@ to toybox. Open your new file in your favorite editor.</p></li> <li><p>Change the copyright notice to your name, email, and the current year.</p></li> -<li><p>Give a URL to the relevant standards document, or say "Not in SUSv3" if +<li><p>Give a URL to the relevant standards document, or say "Not in SUSv4" if there is no relevant standard. (Currently both lines are there, delete -whichever is appropriate.) The existing link goes to the directory of SUSv3 +whichever is inappropriate.) The existing link goes to the directory of SUSv4 command line utility standards on the Open Group's website, where there's often a relevant commandname.html file. Feel free to link to other documentation or standards as appropriate.</p></li> -<li><p>Update the USE_YOURCOMMAND(NEWTOY(yourcommand,"blah",0)) line. The -arguments to newtoy are: 1) the name used to run your command, 2) -the command line arguments (NULL if none), and additional information such -as where your command should be installed on a running system. See [TODO] for -details.</p></li> +<li><p>Update the USE_YOURCOMMAND(NEWTOY(yourcommand,"blah",0)) line. +The NEWTOY macro fills out this command's <a href="#toy_list">toy_list</a> +structure. The arguments to the NEWTOY macro are:</p> + +<ol> +<li><p>the name used to run your command</p></li> +<li><p>the command line argument <a href="#lib_args">option parsing string</a> (NULL if none)</p></li> +<li><p>a bitfield of TOYFLAG values +(defined in toys.h) providing additional information such as where your +command should be installed on a running system, whether to blank umask +before running, whether or not the command must run as root (and thus should +retain root access if installed SUID), and so on.</p></li> +</ol> +</li> <li><p>Change the kconfig data (from "config YOURCOMMAND" to the end of the comment block) to supply your command's configuration and help @@ -89,7 +98,16 @@ information. The uppper case config symbols are used by menuconfig, and are also what the CFG_ and USE_() macros are generated from (see [TODO]). The help information here is used by menuconfig, and also by the "help" command to describe your new command. (See [TODO] for details.) By convention, -unfinished commands default to "n" and finished commands default to "y".<p></li> +unfinished commands default to "n" and finished commands default to "y", +so "make defconfig" selects all finished commands. (Note, "finished" means +"ready to be used", not that it'll never change again.)<p> + +<p>Each help block should start with a "usage: yourcommand" line explaining +any command line arguments added by this config option. The "help" command +outputs this text, and scripts/config2help.c in the build infrastructure +collates these usage lines for commands with multiple configuration +options when producing generated/help.h.</p> +</li> <li><p>Update the DEFINE_GLOBALS() macro to contain your command's global variables, and also change the name "hello" in the #define TT line afterwards @@ -113,7 +131,28 @@ happened to your command line arguments and how to access them.</p></li> <p><a name="top" /><h2>Top level directory.</h2></p> -<p>This directory contains global infrastructure. +<p>This directory contains global infrastructure.</p> + +<h3>toys.h</h3> +<p>Each command #includes "toys.h" as part of its standard prolog.</p> + +<p>This file sucks in most of the commonly used standard #includes, so +individual files can just #include "toys.h" and not have to worry about +stdargs.h and so on. Individual commands still need to #include +special-purpose headers that may not be present on all systems (and thus would +prevent toybox from building that command on such a system with that command +enabled). Examples include regex support, any "linux/" or "asm/" headers, mtab +support (mntent.h and sys/mount.h), and so on.</p> + +<p>The toys.h header also defines structures for most of the global variables +provided to each command by toybox_main(). These are described in +detail in the description for main.c, where they are initialized.</p> + +<p>The global variables are grouped into structures (and a union) for space +savings, to more easily track the amount of memory consumed by them, +so that they may be automatically cleared/initialized as needed, and so +that access to global variables is more easily distinguished from access to +local variables.</p> <h3>main.c</h3> <p>Contains the main() function where execution starts, plus @@ -123,14 +162,16 @@ only command defined outside of the toys directory.)</p> <p>Execution starts in main() which trims any path off of the first command name and calls toybox_main(), which calls toy_exec(), which calls toy_find() -and toy_init() before calling the appropriate command's function from toy_list. +and toy_init() before calling the appropriate command's function from +toy_list[] (via toys.which->toy_main()). If the command is "toybox", execution recurses into toybox_main(), otherwise the call goes to the appropriate commandname_main() from a C file in the toys directory.</p> <p>The following global variables are defined in main.c:</p> <ul> -<li><p>struct toy_list <b>toy_list[]</b> - array describing all the +<a name="toy_list" /> +<li><p><b>struct toy_list toy_list[]</b> - array describing all the commands currently configured into toybox. The first entry (toy_list[0]) is for the "toybox" multiplexer command, which runs all the other built-in commands without symlinks by using its first argument as the name of the command to @@ -141,15 +182,15 @@ binary search).</p> <p>This is a read-only array initialized at compile time by defining macros and #including generated/newtoys.h.</p> -<p>Members of struct toy_list include:</p> +<p>Members of struct toy_list (defined in "toys.h") include:</p> <ul> <li><p>char *<b>name</b> - the name of this command.</p></li> <li><p>void (*<b>toy_main</b>)(void) - function pointer to run this command.</p></li> <li><p>char *<b>options</b> - command line option string (used by get_optflags() in lib/args.c to intialize toys.optflags, toys.optargs, and -entries in the toy union). If this is NULL, no option parsing is done before -calling toy_main().</p></li> +entries in the toy's DEFINE_GLOBALS struct). When this is NULL, no option +parsing is done before calling toy_main().</p></li> <li><p>int <b>flags</b> - Behavior flags for this command. The following flags are currently understood:</p> <ul> @@ -158,6 +199,8 @@ calling toy_main().</p></li> <li><b>TOYFLAG_SBIN</b> - Install this command under /sbin</li> <li><b>TOYFLAG_NOFORK</b> - This command can be used as a shell builtin.</li> <li><b>TOYFLAG_UMASK</b> - Call umask(0) before running this command.</li> +<li><b>TOYFLAG_STAYROOT</b> - Don't drop permissions for this command if toybox is installed SUID root.</li> +<li><b>TOYFLAG_NEEDROOT</b> - This command cannot function unless run with root access.</li> </ul> <br> @@ -166,9 +209,9 @@ in /usr/bin, or together TOYFLAG_USR|TOYFLAG_BIN.</p> </ul> </li> -<li><p>struct toy_context <b>toys</b> - global structure containing information -common to all commands, initializd by toy_init(). Members of this structure -include:</p> +<li><p><b>struct toy_context toys</b> - global structure containing information +common to all commands, initializd by toy_init() and defined in "toys.h". +Members of this structure include:</p> <ul> <li><p>struct toy_list *<b>which</b> - a pointer to this command's toy_list structure. Mostly used to grab the name of the running command @@ -179,12 +222,13 @@ error_exit() functions will return 1 if this is zero, otherwise they'll return this value.</p></li> <li><p>char **<b>argv</b> - "raw" command line options, I.E. the original unmodified string array passed in to main(). Note that modifying this changes -"ps" output, and is not recommended.</p> +"ps" output, and is not recommended. This array is null terminated; a NULL +entry indicates the end of the array.</p> <p>Most commands don't use this field, instead the use optargs, optflags, -and the fields in the toy union initialized by get_optflags().</p> +and the fields in the DEFINE_GLOBALS struct initialized by get_optflags().</p> </li> <li><p>unsigned <b>optflags</b> - Command line option flags, set by -get_optflags(). Indicates which of the command line options listed in +<a href="#lib_args">get_optflags()</a>. Indicates which of the command line options listed in toys->which.options occurred this time.</p> <p>The rightmost command line argument listed in toys->which.options sets bit @@ -197,7 +241,7 @@ the option string "abcd" would parse the command line "-c" to set optflags to 2, b=4, a=8. The punctuation after a letter initializes global variables (see [TODO] DECLARE_GLOBALS() for details).</p> -<p>For more information on option parsing, see [TODO] get_optflags().</p> +<p>For more information on option parsing, see <a href="#lib_args">get_optflags()</a>.</p> </li> <li><p>char **<b>optargs</b> - Null terminated array of arguments left over @@ -209,9 +253,9 @@ optargs[].<p></li> <li><p>int <b>exithelp</b> - Whether error_exit() should print a usage message via help_main() before exiting. (True during option parsing, defaults to false afterwards.)</p></li> -</ul><br> +</ul> -<li><p>union toy_union <b>this</b> - Union of structures containing each +<li><p><b>union toy_union this</b> - Union of structures containing each command's global variables.</p> <p>Global variables are useful: they reduce the overhead of passing extra @@ -224,19 +268,20 @@ space for global variables belonging to other commands you aren't currently running would be wasteful.</p> <p>Toybox handles this by encapsulating each command's global variables in -a structure, and declaring a union of those structures. The DECLARE_GLOBALS() -macro contains the global variables that should go in a command's global -structure. Each variable can then be accessed as "this.commandname.varname". +a structure, and declaring a union of those structures with a single global +instance (called "this"). The DEFINE_GLOBALS() macro contains the global +variables that should go in the current command's global structure. Each +variable can then be accessed as "this.commandname.varname". Generally, the macro TT is #defined to this.commandname so the variable -can then be accessed as "TT.variable".</p> +can then be accessed as "TT.variable". See toys/hello.c for an example.</p> -A command that needs global variables should declare a structure to +<p>A command that needs global variables should declare a structure to contain them all, and add that structure to this union. A command should never declare global variables outside of this, because such global variables would allocate memory when running other commands that don't use those global variables.</p> -<p>The first few fields of this structure can be intialized by get_optargs(), +<p>The first few fields of this structure can be intialized by <a href="#lib_args">get_optargs()</a>, as specified by the options field off this command's toy_list entry. See the get_optargs() description in lib/args.c for details.</p> </li> @@ -290,7 +335,7 @@ which commands (and options to commands) are currently enabled. Used to make generated/config.h and determine which toys/*.c files to build.</p> <p>You can create a human readable "miniconfig" version of this file using -<a href=http://landley.net/code/firmware/new_platform.html#miniconfig>these +<a href=http://landley.net/aboriginal/new_platform.html#miniconfig>these instructions</a>.</p> </li> </ul> @@ -333,12 +378,12 @@ configuration entries for each command.</p> <p>Each command has a configuration entry matching the command name (although configuration symbols are uppercase and command names are lower case). Options to commands start with the command name followed by an underscore and -the option name. Global options are attachd to the "toybox" command, +the option name. Global options are attached to the "toybox" command, and thus use the prefix "TOYBOX_". This organization is used by scripts/cfg2files to select which toys/*.c files to compile for a given .config.</p> -<p>A commands with multiple names (or multiple similar commands implemented in +<p>A command with multiple names (or multiple similar commands implemented in the same .c file) should have config symbols prefixed with the name of their C file. I.E. config symbol prefixes are NEWTOY() names. If OLDTOY() names have config symbols they're options (symbols with an underscore and suffix) @@ -388,7 +433,203 @@ in toys/help.c.</p> strlcpy(), xexec(), xopen()/xread(), xgetcwd(), xabspath(), find_in_path(), itoa().</p> +<a name="lib_args"><h3>lib/args.c</h3> + +<p>Toybox's main.c automatically parses command line options before calling the +command's main function. Option parsing starts in get_optflags(), which stores +results in the global structures "toys" (optflags and optargs) and "this".</p> + +<p>The option parsing infrastructure stores a bitfield in toys.optflags to +indicate which options the current command line contained. Arguments +attached to those options are saved into the command's global structure +("this"). Any remaining command line arguments are collected together into +the null-terminated array toys.optargs, with the length in toys.optc. (Note +that toys.optargs does not contain the current command name at position zero, +use "toys.which->name" for that.) The raw command line arguments get_optflags() +parsed are retained unmodified in toys.argv[].</p> + +<p>Toybox's option parsing logic is controlled by an "optflags" string, using +a format reminiscent of getopt's optargs but has several important differences. +Toybox does not use the getopt() +function out of the C library, get_optflags() is an independent implementation +which doesn't permute the original arguments (and thus doesn't change how the +command is displayed in ps and top), and has many features not present in +libc optargs() (such as the ability to describe long options in the same string +as normal options).</p> + +<p>Each command's NEWTOY() macro has an optflags string as its middle argument, +which sets toy_list.options for that command to tell get_optflags() what +command line arguments to look for, and what to do with them. +If a command has no option +definition string (I.E. the argument is NULL), option parsing is skipped +for that command, which must look at the raw data in toys.argv to parse its +own arguments. (If no currently enabled command uses option parsing, +get_optflags() is optimized out of the resulting binary by the compiler's +--gc-sections option.)</p> + +<p>You don't have to free the option strings, which point into the environment +space (I.E. the string data is not copied). A TOYFLAG_NOFORK command +that uses the linked list type "*" should free the list objects but not +the data they point to, via "llist_free(TT.mylist, NULL);". (If it's not +NOFORK, exit() will free all the malloced data anyway unless you want +to implement a CONFIG_TOYBOX_FREE cleanup for it.)</p> + +<h4>Optflags format string</h4> + +<p>Note: the optflags option description string format is much more +concisely described by a large comment at the top of lib/args.c.</p> + +<p>The general theory is that letters set optflags, and punctuation describes +other actions the option parsing logic should take.</p> + +<p>For example, suppose the command line <b>command -b fruit -d walrus -a 42</b> +is parsed using the optflags string "<b>a#b:c:d</b>". (I.E. +toys.which->options="a#b:c:d" and argv = ["command", "-b", "fruit", "-d", +"walrus", "-a", "42"]). When get_optflags() returns, the following data is +available to command_main(): + +<ul> +<li><p>In <b>struct toys</b>: +<ul> +<li>toys.optflags = 13; // -a = 8 | -b = 4 | -d = 1</li> +<li>toys.optargs[0] = "walrus"; // leftover argument</li> +<li>toys.optargs[1] = NULL; // end of list</li> +<li>toys.optc=1; // there was 1 leftover argument</li> +<li>toys.argv[] = {"-b", "fruit", "-d", "walrus", "-a", "42"}; // The original command line arguments +</ul> +<p></li> + +<li><p>In <b>union this</b> (treated as <b>long this[]</b>): +<ul> +<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> +<li>this[1] = (long)"fruit"; // argument to -b</li> +<li>this[2] = 42; // argument to -a</li> +</ul> +</p></li> +</ul> + +<p>If the command's globals are:</p> + +<blockquote><pre> +DECLARE_GLOBALS( + char *c; + char *b; + long a; +) +#define TT this.command +</pre></blockquote> +<p>That would mean TT.c == NULL, TT.b == "fruit", and TT.a == 42. (Remember, +each entry that receives an argument must be a long or pointer, to line up +with the array position. Right to left in the optflags string corresponds to +top to bottom in DECLARE_GLOBALS().</p> + +<p><b>long toys.optflags</b></p> + +<p>Each option in the optflags string corresponds to a bit position in +toys.optflags, with the same value as a corresponding binary digit. The +rightmost argument is (1<<0), the next to last is (1<<1) and so on. If +the option isn't encountered while parsing argv[], its bit remains 0. +(Since toys.optflags is a long, it's only guaranteed to store 32 bits.) +For example, +the optflags string "abcd" would parse the command line argument "-c" to set +optflags to 2, "-a" would set optflags to 8, "-bd" would set optflags to +6 (I.E. 4|2), and "-a -c" would set optflags to 10 (2|8).</p> + +<p>Only letters are relevant to optflags, punctuation is skipped: in the +string "a*b:c#d", d=1, c=2, b=4, a=8. The punctuation after a letter +usually indicate that the option takes an argument.</p> + +<p><b>Automatically setting global variables from arguments (union this)</b></p> + +<p>The following punctuation characters may be appended to an optflags +argument letter, indicating the option takes an additional argument:</p> + +<ul> +<li><b>:</b> - plus a string argument, keep most recent if more than one.</li> +<li><b>*</b> - plus a string argument, appended to a linked list.</li> +<li><b>#</b> - plus a singed long argument. A {LOW,HIGH} range can also be appended to restrict allowed values of argument.</li> +<li><b>@</b> - plus an occurrence counter (stored in a long)</li> +</ul> + +<p>Arguments may occur with or without a space (I.E. "-a 42" or "-a42"). +The command line argument "-abc" may be interepreted many different ways: +the optflags string "cba" sets toys.optflags = 7, "c:ba" sets toys.optflags=4 +and saves "ba" as the argument to -c, and "cb:a" sets optflags to 6 and saves +"c" as the argument to -b.</p> + +<p>Options which have an argument fill in the corresponding slot in the global +union "this" (see generated/globals.h), treating it as an array of longs +with the rightmost saved in this[0]. Again using "a*b:c#d", "-c 42" would set +this[0]=42; and "-b 42" would set this[1]="42"; each slot is left NULL if +the corresponding argument is not encountered.</p> + +<p>This behavior is useful because the LP64 standard ensures long and pointer +are the same size, and C99 guarantees structure members will occur in memory +in the +same order they're declared, and that padding won't be inserted between +consecutive variables of register size. Thus the first few entries can +be longs or pointers corresponding to the saved arguments.</p> + +<p><b>char *toys.optargs[]</b></p> +<p>Command line arguments in argv[] which are not consumed by option parsing +(I.E. not recognized either as -flags or arguments to -flags) will be copied +to toys.optargs[], with the length of that array in toys.optc. +(When toys.optc is 0, no unrecognized command line arguments remain.) +The order of entries is preserved, and as with argv[] this new array is also +terminated by a NULL entry.</p> + +<p>Option parsing can require a minimum or maximum number of optargs left +over, by adding "<1" (read "at least one") or ">9" ("at most nine") to the +start of the optflags string.</p> + +<p>The special argument "--" terminates option parsing, storing all remaining +arguments in optargs. The "--" itself is consumed.</p> + +<p><b>Other optflags control characters</b></p> + +<p>The following characters may occur at the start of each command's +optflags string, before any options that would set a bit in toys.optflags:</p> + +<ul> +<li><b>^</b> - stop at first nonoption argument (for nice, xargs...)</li> +<li><b>?</b> - allow unknown arguments (pass non-option arguments starting +with - through to optargs instead of erroring out).</li> +<li><b>&</b> - the first argument has imaginary dash (ala tar/ps. If given twice, all arguments have imaginary dash.)</li> +<li><b><</b> - must be followed by a decimal digit indicating at least this many leftover arguments are needed in optargs (default 0)</li> +<li><b>></b> - must be followed by a decimal digit indicating at most this many leftover arguments allowed (default MAX_INT)</li> +</ul> + +<p>The following characters may be appended to an option character, but do +not by themselves indicate an extra argument should be saved in this[]. +(Technically any character not recognized as a control character sets an +optflag, but letters are never control characters.)</p> + +<ul> +<li><b>^</b> - stop parsing options after encountering this option, everything else goes into optargs.</li> +<li><b>|</b> - this option is required. If more than one marked, only one is required.</li> +<li><b>+X</b> enabling this option also enables option X (switch bit on).</li> +<li><b>~X</b> enabling this option disables option X (switch bit off).</li> +<li><b>!X</b> this option cannot be used in combination with X (die with error).</li> +<li><b>[yz]</b> this option requires at least one of y or z to also be enabled.</li> +</ul> + +<p><b>--longopts</b></p> + +<p>The optflags string can contain long options, which are enclosed in +parentheses. They may be appended to an existing option character, in +which case the --longopt is a synonym for that option, ala "a:(--fred)" +which understands "-a blah" or "--fred blah" as synonyms.</p> + +<p>Longopts may also appear before any other options in the optflags string, +in which case they have no corresponding short argument, but instead set +their own bit based on position. So for "(walrus)#(blah)xy:z" "command +--walrus 42" would set toys.optflags = 16 (-z = 1, -y = 2, -x = 4, --blah = 8) +and would assign this[1] = 42;</p> + +<p>A short option may have multiple longopt synonyms, "a(one)(two)", but +each "bare longopt" (ala "(one)(two)abc" before any option characters) +always sets its own bit (although you can group them with +X).</p> <h2>Directory scripts/</h2> @@ -404,4 +645,28 @@ Makefile. <p>Menuconfig infrastructure copied from the Linux kernel. See the Linux kernel's Documentation/kbuild/kconfig-language.txt</p> +<a name="generated"> +<h2>Directory generated/</h2> + +<p>All the files in this directory except the README are generated by the +build. (See scripts/make.sh)</p> + +<ul> +<li><p><b>config.h</b> - CFG_COMMAND and USE_COMMAND() macros set by menuconfig via .config.</p></li> + +<li><p><b>Config.in</b> - Kconfig entries for each command. Included by top level Config.in. The help text in here is used to generated help.h</p></li> + +<li><p><b>help.h</b> - Help text strings for use by "help" command. Building +this file requires python on the host system, so the prebuilt file is shipped +in the build tarball to avoid requiring python to build toybox.</p></li> + +<li><p><b>newtoys.h</b> - List of NEWTOY() or OLDTOY() macros for all available +commands. Associates command_main() functions with command names, provides +option string for command line parsing (<a href="#lib_args">see lib/args.c</a>), +specifies where to install each command and whether toysh should fork before +calling it.</p></li> +</ul> + +<p>Everything in this directory is a derivative file produced from something +else. The entire directory is deleted by "make distclean".</p> <!--#include file="footer.html" --> |