Different behaviour of zsh with two input redirections compared to all other POSIX shells I have installed

Different behaviour of zsh with two input redirections compared to all other POSIX shells I have installed

[Axel Beckert]

Hi,

while I was debugging some non-zsh related issue with "yes '' |
sometool", I noticed that zsh behaves differently in the following
(possibly neither common nor useful, likely esoteric :-) case:

~ → cat /tmp/bar.txt
bar
~ → zsh -c 'echo foo | cat -v < /tmp/bar.txt'
foo
bar
~ → bash -c 'echo foo | cat -v < /tmp/bar.txt'
bar
~ → dash -c 'echo foo | cat -v < /tmp/bar.txt'
bar
~ → ksh -c 'echo foo | cat -v < /tmp/bar.txt'
bar
~ → mksh -c 'echo foo | cat -v < /tmp/bar.txt'
bar

Interestingly some non-POSIX shells have the probably sanest approach:

~ → tcsh -c 'echo foo | cat -v < /tmp/bar.txt'
Ambiguous input redirect.
~ → csh -c 'echo foo | cat -v < /tmp/bar.txt'
Ambiguous input redirect.

(And yes, csh is _not_ a symlink to tcsh on that system. :-)

Is this expected/wanted zsh behaviour? Is this something we should fix
in zsh? And if so, should it rather behave like bash or like tcsh? :-)

I tend to tcsh's variant although I suspect that this could cause more
breakage than bash's behaviour.

		Kind regards, Axel
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Re: Different behaviour of zsh with two input redirections compared to all other POSIX shells I have installed

[Peter Stephenson]

On Mon, 15 Dec 2014 12:33:14 +0100
Axel Beckert <abe@deuxchevaux.org> wrote:
> Is this expected/wanted zsh behaviour? Is this something we should fix
> in zsh? And if so, should it rather behave like bash or like tcsh? :-)

You'll need to try with "unsetopt multios" before comparing with other
shells.  (I'm not suggesting that necessarily removes all issues...)

pws

Re: Different behaviour of zsh with two input redirections compared to all other POSIX shells I have installed

[Axel Beckert]

Hi Peter,

On Mon, Dec 15, 2014 at 11:46:57AM +0000, Peter Stephenson wrote:
> On Mon, 15 Dec 2014 12:33:14 +0100
> Axel Beckert <abe@deuxchevaux.org> wrote:
> > Is this expected/wanted zsh behaviour? Is this something we should fix
> > in zsh? And if so, should it rather behave like bash or like tcsh? :-)
> 
> You'll need to try with "unsetopt multios" before comparing with other
> shells.  (I'm not suggesting that necessarily removes all issues...)

Thanks for that hint. I knew about multiple output redirection being a
zsh-only feature, but I didn't expect that this also affects input
redirection in the same way despite it makes sense (now).

And indeed:

~ → zsh -o nomultios -c 'echo foo | cat -v < /tmp/bar.txt'
bar

So it's not a bug, it's a feature! Thanks again. :-)

		Kind regards, Axel
-- 
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