Re: sh compatibility issue

[Vincent Stemen <vince.lists@hightek.org>]

On Sun, Feb 20, 2011 at 12:05:40AM +0100, Jilles Tjoelker wrote:
> > !(...) without space
> 
> I think the POSIX spec requires this to work, but that may not be
> intentional. '(' is an operator and therefore it does not need a space
> between it and other characters (except to disambiguate between two
> adjacent operators and one two-character operator). It may not be
> intentional because it conflicts with ksh extended pattern matching.
> 
> More generally, this rule also means that things like
>   while(true)do(pwd)done
> do not need any spaces. Although this example is contrived, I can
> imagine there are real scripts that zsh fails to parse because of this;
> the other shells I tried execute it correctly.
> 
> The situation for '!{' is different. '{' is a reserved word and
> therefore it is not recognized. Instead, this describes a utility (or
> alias) that probably does not exist. I do not recommend making special
> allowances for it.
> 
> On a related note, here is another quite insidious sh compatibility
> issue:
>   sh -c 'exec </nonexistent/a; echo wrong'
> This should not print "wrong" because exec is a special builtin and
> redirection errors on special builtins are fatal. Most shells get this
> right nowadays (bash only in POSIX mode) but zsh gets it wrong. Even
>   set -o posixbuiltins
> does not help.
> 
> -- 
> Jilles Tjoelker

Interesting.

I ran these two tests tests with sh, ksh, bash, and zsh.

while(true)do(pwd)done
    This worked in sh, ksh, and bash.  It failed only in zsh.

sh -c 'exec </nonexistent/a; echo wrong'
    This did not print "wrong" in sh and ksh.

    Zsh prints wrong in both sh and zsh mode and bash only prints "wrong"
    without the --posix switch.


Vince