Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!uunet!mcsun!hp4nl!ruuinf!henkp
From: henkp@ruuinf.cs.ruu.nl (Henk P. Penning)
Newsgroups: comp.lang.perl
Subject: Re: pipe to sort and back
Message-ID: <3710@ruuinf.cs.ruu.nl>
Date: 29 Aug 90 00:00:35 GMT
References: <1990Aug24.145831.13299@DRD.Com> <3702@ruuinf.cs.ruu.nl> <3284@uniol.UUCP>
Organization: Utrecht University, Dept. of CS
Lines: 25

In article <3284@uniol.UUCP> henseler@uniol.UUCP (Herwig Henseler) writes:

> [ quotes original problem, my solution, and detects deadlock ]

>To really write and read independently you have to fork to split the process,
>and it will look like:

> [ fork ; child writes ; parent reads ]

This could also be achieved by prepending the program-to-exec with a
buffering process like "perl -e '@_ = <> ; print @_' |".

The problem is that this solution is inadequate in the situation where
the data that the main-prog sends to the sub-prog depends (also) on what
the sub-prog sends back.
I think there is no general solution to the deadlock problem.
To avoid it, you always have to be carefull with your buffering and flushing.

				===  HenkP  ===

-- 
Henk P. Penning, Dept of Computer Science, Utrecht University.
Padualaan 14, P.O. Box 80.089, 3508 TB Utrecht, The Netherlands.
Telephone: +31-30-534106
e-mail   : henkp@cs.ruu.nl (uucp to hp4nl!ruuinf!henkp)