From: lm@mcvoy.com (Larry McVoy)
Subject: [TUHS] Etymology of bc(1)
Date: Thu, 11 Sep 2014 20:33:17 -0700 [thread overview]
Message-ID: <20140912033317.GT633@mcvoy.com> (raw)
In-Reply-To: <20140912031555.02B3318C0A3@mercury.lcs.mit.edu>
On Thu, Sep 11, 2014 at 11:15:55PM -0400, Noel Chiappa wrote:
> > From: Mark Longridge <cubexyz at gmail.com>
>
> > I have a version of Unix v6 that has a file called /usr/doc/bc that
> > describes bc at length
>
> Oh, right, I missed that. I'm a source kind of person... :-)
>
> Speaking of using a pipe to an existing command, I originally mis-read the
> code to think there was only _one_ process involved, and that it was buffering
> its output into the pipe before doing the exec() itself - something like this:
>
> pipe(p);
> write_stuff(p[1]);
> close(0);
> dup(p[0]);
> close(p[0]);
> close(p[1]);
> execl("/bin/other", "other", arg, 0);
>
> Which is kind of a hack, but... it does avoid using a second process, although
> the amount of data that can be passed is limited. (IIRC, a pipe will hold at
> most 8 blocks, at least on V6.) Did this hack ever get used in anything?
Rob (different rob) and I made a command line expr like thing, can't
remember why that did the same trick of shoving stuff (in our case it
was argv) into a pipe and then running yyparse().
It's at www.mcvoy.com/lm/af.shar
Still builds though it is from 1988.
--
---
Larry McVoy lm at mcvoy.com http://www.mcvoy.com/lm
next prev parent reply other threads:[~2014-09-12 3:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-12 3:15 Noel Chiappa
2014-09-12 3:33 ` Larry McVoy [this message]
2014-09-12 6:10 ` Dave Horsfall
-- strict thread matches above, loose matches on Subject: below --
2014-09-12 1:54 Noel Chiappa
2014-09-12 2:35 ` Mark Longridge
2014-09-12 6:00 ` Dave Horsfall
2014-09-12 11:15 ` John Cowan
2014-09-12 11:36 ` Otto Moerbeek
2014-09-12 17:12 ` scj
2014-09-12 17:18 ` Warner Losh
2014-09-12 19:02 ` Clem Cole
2014-09-12 19:36 ` Dave Horsfall
2014-09-12 20:03 ` Warner Losh
2014-09-12 19:32 ` Dave Horsfall
2014-09-12 18:28 ` Tim Bradshaw
2014-09-13 2:52 ` Dave Horsfall
2014-09-11 21:24 Christian Neukirchen
2014-09-11 21:41 ` Warner Losh
2014-09-11 22:04 ` Dave Horsfall
2014-09-11 22:17 ` John Cowan
2014-09-11 23:34 ` scj
2014-09-12 1:03 ` Dave Horsfall
2014-09-12 13:37 ` random832
2014-09-12 14:18 ` Steve Nickolas
2014-09-12 20:02 ` Dave Horsfall
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