Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!slxsys!ibmpcug!dylan
From: dylan@ibmpcug.co.uk (Matthew Farwell)
Newsgroups: comp.unix.programmer
Subject: Re: how to put a program into .plan file
Message-ID: <1990Sep28.172315.23153@ibmpcug.co.uk>
Date: 28 Sep 90 17:23:15 GMT
References: <1990Sep26.155456.1656@agate.berkeley.edu> <10511@panix.UUCP>
Reply-To: dylan@ibmpcug.CO.UK (Matthew Farwell)
Organization: The IBM PC User Group, UK.
Lines: 23

In article <10511@panix.UUCP> jsb@panix.UUCP (J. S. B'ach) writes:
>In article <2782@idunno.Princeton.EDU> subbarao@phoenix.Princeton.EDU (Kartik Subbarao) writes:
>)Then you simply write a C program that checks the status of the file,
>)to see whether someone (the fingerer) has opened it. Then simply
>)write your message to the named pipe. You can do many fancy things with this.
>
>And does this C program run all the time checking?  Or does it sleep
>until fingered?  Even in the latter case some system resources are 
>permanently tied up.  Now (as Emanuel Kant might say) if everyone were
>to do this, the entire process table would fill up!

No. If you write on a pipe with noone at the other end, then the process
blocks (doesn't do anything), until someone starts reading from the pipe.
I had a similar version to r$'s running on this machine for about 8 hours
and it consumed 0.00 cpu seconds (according to ps). The process only takes
up cpu if someone fingers you.

Dylan.
-- 
Matthew J Farwell                 | Email: dylan@ibmpcug.co.uk
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