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BusyBox has support for embedded shell scripts. Two types can be distinguished: custom scripts and scripts implementing applets. Custom scripts should be placed in the 'embed' directory at build time. They are given a default applet configuration and appear as applets to the user but no further configuration is possible. Applet scripts are integrated with the BusyBox build system and are intended to be used to ship standard applets that just happen to be implemented as scripts. They can be configured at build time and appear just like native applets. Such scripts should be placed in the 'applets_sh' directory. A stub C program should be written to provide the usual applet configuration details and placed in a suitable subsystem directory. It may be helpful to have a configuration option to enable any dependencies the script requires: see the 'nologin' applet for an example. function old new delta scripted_main - 41 +41 applet_names 2773 2781 +8 applet_main 1600 1604 +4 i2cdetect_main 672 674 +2 applet_suid 100 101 +1 applet_install_loc 200 201 +1 applet_flags 100 101 +1 packed_usage 33180 33179 -1 tryexec 159 152 -7 evalcommand 1661 1653 -8 script_names 9 - -9 packed_scripts 123 114 -9 complete_cmd_dir_file 826 811 -15 shellexec 271 254 -17 find_command 1007 990 -17 busybox_main 642 624 -18 run_applet_and_exit 100 78 -22 find_script_by_name 51 - -51 ------------------------------------------------------------------------------ (add/remove: 1/2 grow/shrink: 6/9 up/down: 58/-174) Total: -116 bytes text data bss dec hex filename 950034 477 7296 957807 e9d6f busybox_old 949918 477 7296 957691 e9cfb busybox_unstripped Signed-off-by: Ron Yorston <rmy@pobox.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com> |
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| .. | ||
| ash_test | ||
| hush_test | ||
| ash_doc.txt | ||
| ash_ptr_hack.c | ||
| ash.c | ||
| brace.txt | ||
| Config.src | ||
| cttyhack.c | ||
| hush_doc.txt | ||
| hush_leaktool.sh | ||
| hush.c | ||
| Kbuild.src | ||
| match.c | ||
| match.h | ||
| math.c | ||
| math.h | ||
| random.c | ||
| random.h | ||
| README | ||
| README.job | ||
| shell_common.c | ||
| shell_common.h | ||
http://www.opengroup.org/onlinepubs/9699919799/ Open Group Base Specifications Issue 7 http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap01.html Shell & Utilities It says that any of the standard utilities may be implemented as a regular shell built-in. It gives a list of utilities which are usually implemented that way (and some of them can only be implemented as built-ins, like "alias"): alias bg cd command false fc fg getopts jobs kill newgrp pwd read true umask unalias wait http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html Shell Command Language It says that shell must implement special built-ins. Special built-ins differ from regular ones by the fact that variable assignments done on special builtin are *PRESERVED*. That is, VAR=VAL special_builtin; echo $VAR should print VAL. (Another distinction is that an error in special built-in should abort the shell, but this is not such a critical difference, and moreover, at least bash's "set" does not follow this rule, which is even codified in autoconf configure logic now...) List of special builtins: . file : [argument...] break [n] continue [n] eval [argument...] exec [command [argument...]] exit [n] export name[=word]... export -p readonly name[=word]... readonly -p return [n] set [-abCefhmnuvx] [-o option] [argument...] set [+abCefhmnuvx] [+o option] [argument...] set -- [argument...] set -o set +o shift [n] times trap n [condition...] trap [action condition...] unset [-fv] name... In practice, no one uses this obscure feature - none of these builtins gives any special reasons to play such dirty tricks. However. This section also says that *function invocation* should act similar to special built-in. That is, variable assignments done on function invocation should be preserved after function invocation. This is significant: it is not unthinkable to want to run a function with some variables set to special values. But because of the above, it does not work: variable will "leak" out of the function.