busybox

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Denys Vlasenko 6c4f87e411 ash: exec: Stricter pathopt parsing Upstream comment: Date: Sat, 19 May 2018 02:39:50 +0800 exec: Stricter pathopt parsing This patch changes the parsing of pathopt. First of all only %builtin and %func (with arbitrary suffixes) will be recognised. Any other pathopt will be treated as a normal directory. Furthermore, pathopt can now be specified before the directory, rather than after it. In fact, a future version may remove support for pathopt suffixes. Wherever the pathopt is placed, an optional % may be placed after it to terminate the pathopt. This is so that it is less likely that a genuine directory containing a % sign is parsed as a pathopt. Users of padvance outside of exec.c have also been modified: 1) cd(1) will always treat % characters as part of the path. 2) chkmail will continue to accept arbitrary pathopt. 3) find_dot_file will ignore the %builtin pathopt instead of trying to do a stat in the accompanying directory (which is usually the current directory). The patch also removes the clearcmdentry optimisation where we attempt to only partially flush the table where possible. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>		2020-02-17 16:02:40 +01:00
..
ash_test	ash: expand: Fix trailing newlines processing in backquote expanding	2020-02-17 10:24:32 +01:00
hush_test	ash: expand: Fix trailing newlines processing in backquote expanding	2020-02-17 10:24:32 +01:00
ash_doc.txt
ash_ptr_hack.c
ash.c	ash: exec: Stricter pathopt parsing	2020-02-17 16:02:40 +01:00
brace.txt
Config.src	shell: implement optional "BASE#nnnn" numeric literals	2019-05-19 17:23:31 +02:00
cttyhack.c	config: update size information	2018-12-28 03:20:17 +01:00
hush_doc.txt
hush_leaktool.sh
hush.c	ash,hush: allow builtins to be tab-completed, closes 7532	2020-01-29 15:23:17 +01:00
Kbuild.src
match.c
match.h
math.c	shell: better comments in BASE#nn code	2019-10-22 14:25:43 +02:00
math.h	shell: move all definitions of strto_arith_t() together	2019-05-26 14:02:10 +02:00
random.c	whitespace fixes	2018-07-17 15:04:17 +02:00
random.h
README
README.job
shell_common.c	shell/ulimit: code shrink	2019-10-21 16:47:09 +02:00
shell_common.h	hush: fix "export PS1=xyz" and "local PS1=xyz" messing up prompt	2019-05-14 18:56:04 +02:00

README

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.