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From: Peter Andersen <datpete@mjolner.com>
Newsgroups: comp.lang.beta
Subject: Re: Programm Trace
Date: Fri, 19 Jan 2001 10:29:03 +0100
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In-Reply-To: <20010118160649.26709.qmail@noatun.mjolner.dk>; from wolfgang.beutner@cityweb.de on Mon, Jan 15, 2001 at 09:55:09PM +0100
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Wolfgang Beutner writes:

> Hello everybody.
> 
> I am let me say a total newcomer with beta. I learned about the
> existence of it by incident. I am a software engineer and earn the daily
> living by writing software for unix-systems using pure C. Each of our
> programs opens a tracefile at start and the different routines write
> into this file. The level of detail is controlled via
> environment-variables.
> I would like to have something similar for my beta experiments, but
> there is no convnient way of doing this. I either have to generate an
> object and pass it around as parameter or each invocation of my
> tracefunction has to open the file again and do the initialisation each
> time. That seems quite inefficent to me. I would appreciate a stream
> like screen, for instance, which can be used from every object once the
> stream is opened and set up with it's associated variables. I have been
> busy reading the betabook and the documentation, but did not get the
> real idea. Maybe there is a possibilty I did not discover so far ;-)
> 
> Your advice would be very much appreaciated.
> 
> Wolfgang Beutner, Dortmund.

How about (haven't tried it - just an idea):

   trace: @file(# ... #);
   stdout: ^stream;
do (* Setup trace file *)
   '...' -> trace.path;
   trace.openWrite;
   (* Save reference to original screen object *)
   screen[] -> stdout[];
   (* Replace screen reference with trace file object *)
   trace[] -> screen[]
   ...
   'Hello, ' -> screen.putline; (* Ends up in file *)
   'World' -> putline;        (* Ends up in file too *)
   'Goodbye, World' -> stdout.putline; (* Ends in shell *)
   ...
   trace.close;

Sincerely,

Peter Andersen, Mjolner Informatics