Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watnot!watmath!clyde!mcdchg!usenet
From: usenet@mcdchg.UUCP
Newsgroups: mod.os.unix
Subject: How does close() make dup() work in getty??
Message-ID: <233@mcdchg.UUCP>
Date: Fri, 13-Mar-87 10:11:52 EST
Article-I.D.: mcdchg.233
Posted: Fri Mar 13 10:11:52 1987
Date-Received: Sat, 14-Mar-87 07:06:59 EST
Sender: usenet@mcdchg.UUCP
Organization: Univ. of Central Florida, Orlando
Lines: 46
Keywords: close dup getty /dev/tty
Approved: usenet@falkor.UUCP

I recently wrote a new getty for a RT built around curses.

My question is about why one version works and another not.
The following code out lines the differences in the two versions.
Version 1 does not work while Version 2 does.

Version 1.

		main(tty)
			char *tty;				/* tty to use */
			{
			set_ioctl();			/* put in known mode */
			close(0);
			close(1);
			close(2);
			dup(dup(open(tty,2)));
			write_utmp(tty);		/* do utmp stuff */
			get_logid(logid);			/* prompt for logid */
			execle("/bin/login",logid,NULL);
			}

Version 2.
		main(tty)
			char *tty;				/* tty to use */
			{
			set_ioctl();			/* put in known mode */
			close(0);
			close(1);
			open(tty,2);
			close(2);
			dup(0);
			dup(1);
			write_utmp(tty);		/* do utmp stuff */
			get_logid(logid);			/* prompt for logid */
			execle("/bin/login",logid,NULL);
			}

Does close() cause something to settle that dup() needes from the open()?
The problem with Version one is that /dev/tty does not get attached to
the control group.

Any idea's that might explain this mystery would be greatly appreciated!!
-- 
Larry Baird 					Dept. of Computer Science
uucp: {ihnp4!decvax,peora}!ucf-cs!baird		University of Central Florida
						Orlando, FL  32816