From: "David J. Fiander" <david@golem.uucp>
To: Chris Siebenmann <cks@hawkwind.utcs.toronto.edu>
Cc: The rc user community <rc@archone.tamu.edu>
Subject: Re: A lighter read function
Date: Thu, 12 Dec 1991 18:58:56 -0600 [thread overview]
Message-ID: <26539.692585936@golem.UUCP> (raw)
In-Reply-To: Your message of "Wed, 11 Dec 91 14:28:23 EST." <91Dec11.142829est.2716@hawkwind.utcs.toronto.edu>
>From: Chris Siebenmann <hawkwind.utcs.toronto.edu!cks@rutgers.uucp>
> Here is my current version of read along with a couple of functions
>that it relies on:
It looks pretty good.
>
># A real read function, as in 'read var var var'. Returns failure
># on EOF. relies on the 'line' program.
>nl='
>'
>fn read { _v=() _i=() {
> _v=`` $nl {line; echo $status}
This is why byron added the "``ifs{}" extension, but the Plan 9
way is probably
ifs=$nl { _v=`{line; echo $status}}
which sets ifs for only the one command, but sets _v globally.
> if (! ~ $_v(2) 0) return $_v(2);
There's a small problem with this. If line sees an EOF, then
it will print a newline, and exit with status 1. _v is thus
set to "1", since there is nothing before the first nl. There
is no $_v(2), so the ~ fails, and read returns success.
I got around this by writing it as:
x = `{line || echo 1^$nl^1; echo 0}
Then, if line fails, we get
x = (1 1)
otherwise we get
x = ('the line' 0)
--
David J. Fiander |email [Fr., = enamel] Used attrib. in `email ink', ink
<david@golem.uucp> |used on glass, porcelain, etc.
next prev parent reply other threads:[~1991-12-13 1:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
1991-12-11 4:32 DaviD W. Sanderson
1991-12-11 12:28 ` David J. Fiander
1991-12-11 19:28 ` Chris Siebenmann
1991-12-13 0:58 ` David J. Fiander [this message]
1991-12-13 1:37 ` Chris Siebenmann
1991-12-13 1:47 ` David Hogan
1991-12-11 21:48 ` Ronald S H Khoo
1991-12-12 12:16 ` David J. Fiander
-- strict thread matches above, loose matches on Subject: below --
1991-12-11 3:53 David J. Fiander
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