[devel] Re: bash vs sh policy
Alexey Tourbin
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Чт Окт 9 19:36:09 MSD 2003
On Thu, Oct 09, 2003 at 02:02:04PM +0400, Alexey Tourbin wrote:
> Some more modern operating systems talk about `the POSIX shell'.
> This is an attempt to standardize UNIX shells; it's most like
> the Korn shell, although, a bit confusingly, it's often just
> called sh, because the standard says that it should be.
> Usually, this just means you get a bit extra free with your sh
> and it still does what you expect.
Интересно. Google показывает, что на самом деле всё ещё сложнее:
Also on Digital Unix you may way to use /usr/bin/posix/sh rather
than the DEC special bourne shell. Alternatively (from the man page):
[Digital] Subsequent shells spawned from the initial shell
depend on the value in the environment variable BIN_SH. If this
variable is set to xpg4, the POSIX shell is started. If this
variable is set to svr4, an SVR4 compliant version of the
shell is started. If this variable is unset, the Bourne shell
is started. If this variable is set to any other value, an error
is reported and the results are unpredicatable.
http://www.greatcircle.com/lists/majordomo-workers/mhonarc/majordomo-workers.199610/msg00159.html
If you graft on some interactive productivity enhancements
onto the Bourne shell, the result is the POSIX (Portable
Operating System Interface) shell. The POSIX shell is very
similar to the Korn shell in terms of the interactive features
provided, right down to the keystroke in most cases. The Korn
shell is not standardized, so there are annoying differences
between various vendor's versions; the POSIX shell attempts to
raise the bar for a universally available shell.
The current POSIX shells are based on POSIX.2 of the IEEE
POSIX Shell and Tools specification (IEEE Working Group
1003.2). The POSIX shell is a superset of the Bourne shell.
...
The POSIX shell offers many shortcuts, such as aliases, cd
path searches, filename completion and job control.
http://216.239.59.104/search?q=cache:xXuCYqFChlsJ:www.unix.kg/eng/misc/unix_unleashed/page014.shtml+posix+shell+sh5
Короче SystemV shell (aka sh5) != Bourne shell != POSIX shell != Bash.
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