Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ico!vail!dougm
From: dougm@ico.ISC.COM (Doug McCallum)
Newsgroups: comp.unix.wizards
Subject: Re: STREAMS module / dup question
Message-ID: <15757@vail.ICO.ISC.COM>
Date: 14 May 89 22:22:55 GMT
References: <569@lehi3b15.csee.Lehigh.EDU>
Reply-To: dougm@ico.ISC.COM (Doug McCallum,violet,114,)
Organization: Interactive Systems Corp., Boulder CO
Lines: 10

In article <569@lehi3b15.csee.Lehigh.EDU> murrey@lehi3b15.csee.Lehigh.EDU (Erik Murrey) writes:
...
>Questions:
>	1. Do both of those fd's have that module pushed on it?
>	2. What happens during a fork()?
Both fd's refer to the same stream so both have the module pushed on it.
A file descriptor refers to a kernel file structure that points to the
stream.  When you dup the descriptor you inherit the same stream.
It is the same principle that when you dup a tty descriptor the new one
refers to the same device so later ioctl calls have an effect on both.