Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!maverick.ksu.ksu.edu!unmvax!uokmax!alliant.backbone.uoknor.edu!jay
From: jay@alliant.backbone.uoknor.edu (Jay Liang)
Newsgroups: comp.unix.questions
Subject: Csh pipe/fork syncronization
Keywords: csh, pipe, fork
Message-ID: <1990Jul12.222235.15827@uokmax.uucp>
Date: 12 Jul 90 22:22:35 GMT
Sender: news@uokmax.uucp (Nets)
Reply-To: jay@alliant.backbone.uoknor.edu
Distribution: na
Organization: University of Oklahoma, Norman,OK 73019
Lines: 31


I am curious to know the correct sequence of csh pipes and forks
implementation.  Please look at the following script on machine A:

A% ps | grep ps
 4769 pc Run     0:00  ps 
 4798 pc Slp     0:00  grep ps 
A% ps | grep ps | grep ps
 2742 pc Slp     0:00  grep ps 
10085 pc Slp     0:00  grep ps
14611 pc Run     0:00  ps

and on machine B:

B% ps | grep ps
 8524  p3  R     0:01 ps
B% ps | grep ps | grep ps
 7657  p3  R     0:01 ps
B%

Machine A forks out subshells BEFORE processing the first command
where machine B processes the command line input in sequence.
All of the UNIX machines that I have access to acts like machine B
except one.  What is the _correct_ implementation if there is any?
Have you seen this before?  Am I missing something here?


Jay Liang (jay@alliant.backbone.uoknor.edu)
Geosciences Computing Network
University of Oklahoma
Norman, OK 73019