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From: hamilton@osiris.cso.uiuc.edu
Newsgroups: comp.lang.c
Subject: Re: File descriptors and streams and co
Message-ID: <1239500006@osiris.cso.uiuc.edu>
Date: 25 Apr 89 23:23:00 GMT
References: <1743@leah.Albany.Edu>
Lines: 42
Nf-ID: #R:leah.Albany.Edu:1743:osiris.cso.uiuc.edu:1239500006:000:865
Nf-From: osiris.cso.uiuc.edu!hamilton    Apr 25 18:23:00 1989


rds95@leah.Albany.Edu says:

> I want to be able to make "stdin" read from someplace besides, well,
> standard input in the middle of my program, and then go back to where
> it was again.

i would do it like this:

	void fexchange(a, b)
	FILE *a;
	FILE *b;
	{
		FILE tmp;

		tmp = *a;
		*a = *b;
		*b = tmp;
	}

	FILE *my_file;

	/* open my_file */

	/* exchange stdin & my_file */
	fexchange(stdin, my_file);

	/* ... use stdin ... */

	/* restore stdin */
	fexchange(stdin, my_file);

	fclose(my_file);

i've been using this technique for years in an application where i
wanted a nested "#include" capability for interactive input.

	wayne hamilton
	U of Il and US Army Corps of Engineers CERL
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