busybox/shell
Denys Vlasenko c0663c7cd2 ash: [SIGNAL] Remove EXSIG
Upstream commit 1:

    Date: Sun, 22 Feb 2009 18:16:13 +0800
    [SIGNAL] Remove EXSIG

    Now that waitcmd no longer uses EXSIG we can remove it.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Upstream commit 2:

    Date: Thu, 2 Oct 2014 21:07:55 +0800
    [ERROR] Set exitstatus in onint

    Currently the exit status when we receive SIGINT is set in evalcommand
    which means that it doesn't always get set.  For example, if you press
    CTRL-C at the prompt of an interactive dash, the exit status is not
    set to 130 as it is in many other Bourne shells.

    This patch fixes this by moving the setting of the exit status into
    onint which also simplifies evalcommand.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Upstream commit 3:

    Date: Fri, 3 Oct 2014 14:07:07 +0800
    [EVAL] Do not clobber exitstatus in evalcommand

    All originators of EXERROR have been setting the exitstatus for
    a while now.  So it is no longer appropriate to set it explicitly
    in evalcommand.

    In fact doing so may cause the original exitstatus to be lost.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Last three coomits:
function                                             old     new   delta
waitcmd                                              186     224     +38
dowait                                               276     284      +8
waitforjob                                           104     107      +3
localcmd                                             348     350      +2
showjobs                                              64      61      -3
forkshell                                            263     260      -3
raise_interrupt                                       93      67     -26
blocking_wait_with_raise_on_sig                       40       -     -40
evalcommand                                         1264    1208     -56
evaltree                                             809     498    -311

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-10-27 21:13:49 +02:00
..
ash_test ash: [PARSER] Recognise here-doc delimiters terminated by EOF 2016-10-26 16:26:45 +02:00
hush_test ash: [PARSER] Recognise here-doc delimiters terminated by EOF 2016-10-26 16:26:45 +02:00
ash_doc.txt
ash_ptr_hack.c *: make GNU licensing statement forms more regular 2010-08-16 20:14:46 +02:00
ash.c ash: [SIGNAL] Remove EXSIG 2016-10-27 21:13:49 +02:00
brace.txt
Config.src config: disentangle PREFER_APPLETS from SH_STANDALONE and SH_NOFORK 2016-07-22 18:48:38 +02:00
cttyhack.c cttyhack: handle multiple consoles found in sysfs 2012-02-04 21:55:01 +01:00
hush_doc.txt
hush_leaktool.sh
hush.c ash: [SHELL] Expand ENV before using it 2016-10-27 11:28:59 +02:00
Kbuild.src *: make GNU licensing statement forms more regular 2010-08-16 20:14:46 +02:00
match.c shell/match.c: shrink by dropping double bool inversion 2010-09-12 15:06:42 +02:00
match.h hush: optimize #[#] and %[%] for speed. size -2 bytes. 2010-09-04 21:21:07 +02:00
math.c typo fix in comment 2014-11-20 01:43:30 +01:00
math.h move endofname() to libbb 2013-02-26 00:36:53 +01:00
random.c ash,hush: fix a thinko about 2^64-1 factorization 2014-03-15 09:25:46 +01:00
random.h ash,hush: improve randomness of $RANDOM, add easy-ish way to test it 2014-03-13 12:52:43 +01:00
README
README.job
shell_common.c ash: [VAR] Initialise OPTIND after importing environment 2016-09-30 14:46:41 +02:00
shell_common.h ash: [VAR] Initialise OPTIND after importing environment 2016-09-30 14:46:41 +02:00

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.