From: Bart Schaefer <schaefer@brasslantern.com>
To: Ray Andrews <rayandrews@eastlink.ca>
Cc: Zsh Users <zsh-users@zsh.org>
Subject: Re: &&||
Date: Tue, 20 Feb 2018 12:28:07 -0800 [thread overview]
Message-ID: <CAH+w=7ar21AnR89XtbtaTQtqZYJUvGsQzxcfkDvd2UqJ70=xMw@mail.gmail.com> (raw)
In-Reply-To: <dd60f68c-dddd-1ea3-bc4a-ebcb83173cdf@eastlink.ca>
On Tue, Feb 20, 2018 at 11:24 AM, Ray Andrews <rayandrews@eastlink.ca> wrote:
> On 20/02/18 09:07 AM, Peter Stephenson wrote:
>>
>> You've now extended your demand so that it works with an else clause as
>
> Not 'extended' that is the entire point of my question. I'm expecting the
> '||' to be identical to a logical 'else', there is no other issue.
But "||" is not "else" and "&&" is not "if" -- rather they are "and" /
"or" (which is why they use the symbols they do).
first-statement AND second-statement OR third-statement
The implicit grouping is left-to-right, so that's the same as
{ first-statement AND second-statement } OR third-statement
Thus the first pair succeeds only when both succeed, and
third-statement occurs when the first pair fails. To express this
with if/else you would write
if first-statement;
then
if second-statement;
then
true;
else
false;
fi;
else
false;
fi;
if [[ $? -eq 0 ]];
then
if third-statement;
then
true;
else
false;
fi;
else
false;
fi
> Demand? I seek clarification
I believe PWS meant "demand" in the sense of what your statement asks
of the shell, not what you're asking him to explain.
> Braces are
> ignored as far as truth tests on the left of any && or ||.
No, that's entirely wrong. Braces always return the final status of
the enclosed list of statements. && and || always use the final
status of the entire chain of any && or || to their left. The two are
related only when the braces surround another chain of && or || but
only in so far as that affects the final status of the braces.
next prev parent reply other threads:[~2018-02-20 20:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-19 21:12 &&|| Ray Andrews
2018-02-19 21:57 ` &&|| Peter Stephenson
2018-02-19 22:47 ` &&|| Ray Andrews
2018-02-20 9:26 ` &&|| Peter Stephenson
2018-02-20 7:54 ` &&|| Ray Andrews
2018-02-20 17:07 ` &&|| Peter Stephenson
2018-02-20 19:24 ` &&|| Ray Andrews
2018-02-20 20:28 ` Bart Schaefer [this message]
2018-02-20 21:45 ` &&|| Ray Andrews
-- strict thread matches above, loose matches on Subject: below --
2004-11-16 13:45 !!:$ keef
2004-11-16 14:22 ` !!:$ Peter Stephenson
2004-11-16 14:31 ` !!:$ Stephane Chazelas
2004-11-16 15:37 ` !!:$ Bart Schaefer
2004-11-16 16:08 ` !!:$ Peter Stephenson
2004-11-17 0:03 ` !!:$ Bart Schaefer
2004-11-17 19:25 ` !!:$ Danek Duvall
2004-11-18 1:10 ` !!:$ Bart Schaefer
2003-07-02 15:06 ?????? JEFF BICKLEY
2003-07-02 19:56 ` ?????? Thorsten Haude
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