Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!snorkelwacker!bloom-beacon!eru!luth!sunic!mcsun!unido!laura!heike!klute
From: klute@heike.informatik.uni-dortmund.de (Rainer Klute)
Newsgroups: comp.sys.atari.st
Subject: Re: re-direction
Message-ID: <2094@laura.UUCP>
Date: 11 Apr 90 08:14:44 GMT
References: <1602@electro.UUCP>
Sender: news@laura.UUCP
Reply-To: klute@heike.informatik.uni-dortmund.de (Rainer Klute)
Organization: University of Dortmund, FRG
Lines: 48

In article <1602@electro.UUCP>, ignac@electro.UUCP (Ignac Kolenko) writes:
|>
|>what is the "official" method of doing io-redirection in software.
|>what i want is for program A to run. It prints to the screen using Cconws();.
|>In the course of running A, it will invoke B, which also prints with Cconws.
|>Before B is called, the user has the option of redirecting B's 
|>output anywhere (screen, printer, file, modem). After B runs, control is
|>returned to A, which will then continue printing to the screen as before.


Here is what I use in Arcgsh for io redirection to call Zoo (hence 
some names) as a dependend program (partly cited). "zoo_stdin" and 
"zoo_stdout" are filenames, the "...descriptors" are ints, STDIN is 0 
and STDOUT is 1.

/*	redirect standard input:	*/
save_stdin_descriptor = Fdup (STDIN);
my_stdin_descriptor = Fopen (zoo_stdin, 0);
if (my_stdin_descriptor >= 0)
	Fforce (STDIN, my_stdin_descriptor);

/*	redirect standard output:	*/
save_stdout_descriptor = Fdup (STDOUT);
if (append_to_stdout_file)
	{
	my_stdout_descriptor = Fopen (zoo_stdout, 2);
	if (my_stdout_descriptor >= 0)
	   Fseek (0L, my_stdout_descriptor, 2);
	else
	   my_stdout_descriptor = Fcreate (zoo_stdout, 0);
	}
else
	my_stdout_descriptor = Fcreate (zoo_stdout, 0);
if (my_stdout_descriptor >= 0)
	Fforce (STDOUT, my_stdout_descriptor);

/*	call the program now...	*/

/*	undo the redirections:	*/
Fforce (STDIN, save_stdin_descriptor);
Fclose (my_stdin_descriptor);
Fforce (STDOUT, save_stdout_descriptor);
Fclose (my_stdout_descriptor);
                     
  Dipl.-Inform. Rainer Klute      klute@heike.informatik.uni-dortmund.de
  Univ. Dortmund, IRB             klute@unido.uucp, klute@unido.bitnet
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