Denys Vlasenko
bb61205290
hush: fix handling of "cmd && &"
|
3 年 前 | |
|---|---|---|
| .. | ||
| ash_test | 3 年 前 | |
| hush_test | 3 年 前 | |
| Config.src | 4 年 前 | |
| Kbuild.src | 8 年 前 | |
| README | 14 年 前 | |
| README.job | 17 年 前 | |
| ash.c | 3 年 前 | |
| ash_doc.txt | 16 年 前 | |
| ash_ptr_hack.c | 14 年 前 | |
| brace.txt | 15 年 前 | |
| cttyhack.c | 6 年 前 | |
| hush.c | 3 年 前 | |
| hush_doc.txt | 16 年 前 | |
| hush_leaktool.sh | 15 年 前 | |
| match.c | 6 年 前 | |
| match.h | 14 年 前 | |
| math.c | 4 年 前 | |
| math.h | 5 年 前 | |
| random.c | 6 年 前 | |
| random.h | 10 年 前 | |
| shell_common.c | 4 年 前 | |
| shell_common.h | 5 年 前 | |
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.
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.