Path: utzoo!attcan!uunet!lll-winken!csd4.milw.wisc.edu!bionet!ames!haven!adm!xadmx!rbj@dsys.icst.nbs.gov
From: rbj@dsys.icst.nbs.gov (Root Boy Jim)
Newsgroups: comp.unix.wizards
Subject: shell script puzzler
Message-ID: <19668@adm.BRL.MIL>
Date: 18 May 89 16:01:46 GMT
Sender: news@adm.BRL.MIL
Lines: 33

? From: Chris Torek <chris@mimsy.uucp>

? In article <995@etnibsd.UUCP> vsh@etnibsd.UUCP (Steve Harris) writes:
? >Here is one for the shell programming gurus:  given the following
? >shell script, how can I get the subshell to echo its true pid??
? >(I am running SunOS 3.4, if it matters).

I'm running SunOS 3.5.

? >#! /bin/sh
? >echo $$			# echos pid of parent shell
? >( echo $$ )		# echos same pid

? At least in 4BSD, you cannot.  `sh' sets up `$$' near the top of main()
? and never changes it (except when running a script, in lieu of starting
? a new /bin/sh to run it).
? -- 
? In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
? Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris

Chris hinted that you must run another sh. Here's how:

	#! /bin/sh
	echo shell pid $$
	(sh -c 'echo subshell pid $$')
	(echo 'echo another subshell pid $$' | sh)
	(eval 'echo why is $$ the parent pid?')
	echo shell pid $$

For some reason, the eval form doesn't work.

	Root Boy Jim is what I am
	Are you what you are or what?