Re: For loop bug

[Philippe Troin <phil@fifi.org>]

"Bart Schaefer" <schaefer@brasslantern.com> writes:

> [Excerpts reordered for clarity.]
> 
> On Sep 15,  9:58pm, Philippe Troin wrote:
> } Subject: Re: For loop bug
> }
> } "Bart Schaefer" <schaefer@brasslantern.com> writes:
> } 
> } > On Sep 13,  5:58pm, Philippe Troin wrote:
> } > } 
> } > }   % for i in 1 2 3; do { {echo $i; [[ $i == 2 ]] && exit 1; } || break };
> } > }   > done && echo X
> } > }   1
> } > }   X
> } > }   % 
> } > 
> } > That is not a bug.
> }
> } But shouldn't it print:
> } 
> }   1
> }   2
> }   X
> 
> No, it shouldn't.  "for i in 1 2 3 ..."
> 
> OK, so the first time around the loop i=1, and zsh echoes 1.
> 
> Now we're testing [[ $i == 2 ]], which is [[ 1 == 2 ]] which is false;
> hence we have { false && exit 1; } which doesn't call exit but also
> doesn't evaluate as true, because the first branch of the && is false.
> 
> So the outer expression becomes { { false } || break }; and the loop ends
> immediately.
> 
> } The echo $i with i set to 2 occurs before the exit and break
> } statements.
> 
> $i never has a chance to get set to 2.

Got that part. Thanks for the clarifications.
 
> } > Further, { } is not a subshell, so { [[ 2 == 2 ]] && exit 1; } would most
> } > likely produce something like
> } > 
> } > login:
> } > 
> } > which might surprise you even more.
> } 
> } I'm not sure I get this part.
> 
> If you call { exit 1 } from an interactive zsh, the shell will exit and
> you'll end up back at your login prompt (or your xterm will disappear or
> your remote connection will drop or whatever).  Expressions in { } are
> evaluated in the current shell.  If it were ( exit 1 ) with parens, that's
> evaluated in a subshell and the interactive shell would keep running.

Indeed. However my version of zsh does not exit: it goes on happily as
if nothing happened.

Phil.