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From: chris@mimsy.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: /dev/stdin for 4.3?
Message-ID: <6881@mimsy.UUCP>
Date: Tue, 2-Jun-87 03:11:52 EDT
Article-I.D.: mimsy.6881
Posted: Tue Jun  2 03:11:52 1987
Date-Received: Thu, 4-Jun-87 01:32:01 EDT
References: <7359@brl-adm.ARPA> <5856@brl-smoke.ARPA> <15318@onfcanim.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 35

>In article <5856@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>>...All you need is the open() entry, which should simply snarf
>>up the process's corresponding file table index, just
>>like a dup() except you don't allocate anything.

In article <15318@onfcanim.UUCP> dave@onfcanim.UUCP writes:
>I believe it's better to do the equivalent of a full dup(), returning
>a newly-opened descriptor.  You still need only an open() entry,
>but you have to alloc an ofile table slot and increment the reference
>count on the file struct.

All that is done for you by `open'; you need only discard the inode.
Specifically:

fdopen(dev, flag)
	dev_t dev;
	int flag;
{
	register struct file *fp, *wfp;
	int rwmode;

	fp = getf(u.u_r.r_val1);	/* never fails */
	if ((wfp = getf(minor(dev))) == NULL || fp == wfp)
		return (EBADF);
	rwmode = flag & (FREAD|FWRITE);
	if ((fp->f_flag & rwmode) != rwmode)
		return (EACCES);
	irele((struct inode *)fp->f_data);
	fp->f_count = 0;
	dupit(u.u_r.r_val1, wfp, u.u_pofile[minor(dev)]);
	return (0);
}
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris