From: Bart Schaefer <schaefer@brasslantern.com>
To: zsh-users@zsh.org
Subject: Re: for loop question
Date: Mon, 03 Nov 2014 18:43:38 -0800 [thread overview]
Message-ID: <141103184338.ZM32221@torch.brasslantern.com> (raw)
In-Reply-To: <20141104015639.GA2871@localhost.localdomain>
On Nov 4, 9:56am, Han Pingtian wrote:
}
} > for ((i=1; (z[$([ -n "$TLC[i]" ])0]),$? == 0; i++))
} > print -ru2 -- $TLC[i]
} >
} What does the (z[$([ -n "$TLC[i]" ])0]) mean, please?
It's an overly-obfuscated way to write $([ -n "$TLC[i]" ]). The real
work is the ",$?" part.
z[...],$? is used to throw away the z[...] part and keep the value of $?.
The value of $? comes from the side-effect of the $(...) inside the
subscript of z[...].
The 0 is appended because [ -n "$TLC[i]" ] does not produce any output,
but there has to be a valid number as the subscript, hence z[0].
This could be written a LOT more plainly as
for ((i=1; $([ -n "$TLC[i]" ]; echo $?) == 0; i++))
without needing any more characters. If we're playing golf,
for ((i=1; ! $([ "$TLC[i]" ]; echo $?); i++))
works too.
Which, by the way, points out another reason you can't just use the
exit status of a command in a math context: command success/failure
are the reverse of true/false when taken as integer values.
next prev parent reply other threads:[~2014-11-04 2:44 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-02 20:47 Ray Andrews
2014-11-02 21:00 ` Bart Schaefer
[not found] ` <CAH+w=7aWS0xyS4CXRJBphDjesfUFQOsyJRMaG3RZRxmuj7xkOg__20885.3257158355$1414962125$gmane$org@mail.gmail.com>
2014-11-02 21:37 ` Stephane Chazelas
2014-11-02 22:44 ` Ray Andrews
2014-11-02 22:57 ` Bart Schaefer
2014-11-02 23:24 ` Oliver Kiddle
2014-11-03 0:07 ` Ray Andrews
2014-11-03 1:53 ` Mikael Magnusson
2014-11-03 2:22 ` Ray Andrews
2014-11-03 9:22 ` Mikael Magnusson
2014-11-03 17:26 ` Ray Andrews
2014-11-04 1:56 ` Han Pingtian
2014-11-04 2:29 ` Han Pingtian
2014-11-04 2:43 ` Bart Schaefer [this message]
2014-11-04 4:51 ` Han Pingtian
2014-11-04 6:37 ` Ray Andrews
2014-11-04 7:13 ` Bart Schaefer
2014-11-04 18:00 ` Ray Andrews
[not found] ` <141103184338.ZM32221__48957.5251042426$1415069142$gmane$org@torch.brasslantern.com>
2014-11-04 7:08 ` Stephane Chazelas
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