From owner-freebsd-hackers  Fri Apr 26 17:47:22 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.3/8.7.3) id RAA14751
          for hackers-outgoing; Fri, 26 Apr 1996 17:47:22 -0700 (PDT)
Received: from vent.pipex.net (root@vent.pipex.net [158.43.128.5])
          by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id RAA14737
          for <hackers@freebsd.org>; Fri, 26 Apr 1996 17:47:20 -0700 (PDT)
Received:  from dial.pipex.com by vent.pipex.net (8.6.12/PIPEX simple 1.20)
	id BAA05937; Sat, 27 Apr 1996 01:46:54 +0100
Received: (from jraynard@localhost) by dial.pipex.com (8.6.12/8.6.12) id AAA01874; Sat, 27 Apr 1996 00:04:01 GMT
Date: Sat, 27 Apr 1996 00:04:01 GMT
From: James Raynard <jraynard@dial.pipex.com>
Message-Id: <199604270004.AAA01874@dial.pipex.com>
To: bde@zeta.org.au
CC: julian@ref.tfs.com, hackers@freebsd.org
In-reply-to: <199604250044.KAA29532@godzilla.zeta.org.au> (message from Bruce Evans on Thu, 25 Apr 1996 10:44:43 +1000)
Subject: Re: Flaws in system() implementation?
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk


> >>  If "command" is a null pointer, the system() function returns non-zero
> >>  only if a command processor is available.
> 
> >OK (Out of interest, what kind of circumstances would result in a
> >command processor not being available?)
> 
> Non-POSIX ones.  system((char *)NULL) is about the only aspect of system()
> that is specified by ANSI.  It returns 0 to tell you that system() is
> completely useless on the current system :-).

I see. 8-)

> >>  If a child process cannot be  created,
> >>  or if the termination status of hte command interpretter cannot be obtained
> >>  system() returns -1
> >>  and sets errno to indicate the error.
> 
> >Doesn't that imply that system() should return -1 if fork() fails?
> >(Forgive me if I'm being obtuse, I'm not very experienced at reading
> >standardese).
> 
> It's less ambiguous than julianese :-).  It completely specifies the
> return value after a fork failure, at least in my copy, which says
> "shall return -1" instead of "returns -1".  "shall" is standardese that
> means that the implementation is non-conforming if it does anything
> else.  "should" would allow the implementation to screw up.

OK, that was what I thought it meant - I was using "should" with its
colloquial meaning rather than the standardese meaning (I did warn you
I wasn't very experienced at this 8-)

Thanks for answering all my questions,
James

-- 
James Raynard, Edinburgh, Scotland
mail:	jraynard@dial.pipex.com