4f2ef4a836
To assist in the deployment of shell scripts it may be convenient to embed them in the BusyBox binary. 'Embed scripts in the binary' takes any files in the directory 'embed', concatenates them with null separators, compresses them and embeds them in the binary. When scripts are embedded in the binary, scripts can be run as 'busybox SCRIPT [ARGS]' or by usual (sym)link mechanism. embed/nologin is provided as an example. function old new delta packed_scripts - 123 +123 unpack_scripts - 87 +87 ash_main 1103 1171 +68 run_applet_and_exit 78 128 +50 get_script_content - 32 +32 script_names - 10 +10 expmeta 663 659 -4 ------------------------------------------------------------------------------ (add/remove: 4/0 grow/shrink: 2/1 up/down: 370/-4) Total: 366 bytes 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.