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.