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X-Authentication-Warning: slinky.cs.nyu.edu: pechtcha owned process doing -bs
Date: Fri, 18 Oct 2002 11:36:49 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: Andrew DeFaria <Andrew AT defaria DOT com>
cc: cygwin AT cygwin DOT com
Subject: Re: About ENV?
In-Reply-To: <3DB02737.7000406@DeFaria.com>
Message-ID: <Pine.GSO.4.44.0210181133510.6818-100000@slinky.cs.nyu.edu>
Importance: Normal
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

On Fri, 18 Oct 2002, Andrew DeFaria wrote:

> John Vincent wrote:
>
> > Hi,
> >
> > Not quite right there ... You can preceed a command with an
> > assignment, and the assigned variable is then put into the environment
> > of the command that is run. Thus the command
> > "echo" is run with an environment variable AAAA with the value aaaa.
> > However, this does not change the AAAA shell variable (which is
> > currently empty) so the echo prints a blank (it's empty argument) and
> > ignores the AAAA in it's environment.
> >
> > This syntax is useful for setting environment variables for one
> > command invocation only. They are not saved.
> >
> > I hope this fully explains what is going on.
>
> It doesn't. If "This syntax is useful for setting environment variables
> for one command invocation only" then the echo command should have
> echoed "aaa". Otherwise the syntax is not useful for setting environment
> variables for one command invocation. Perhaps what is meant is that this
> syntax is useful for overriding environment variables for one command
> invocation? However this leaves a glaring inconsistancy prone to error
> if the variable was not set already then no override takes place.

Andrew,

[pechtcha:~] AAAA=aaa && echo $AAAA
aaa
[pechtcha:~] AAAA=aaa echo $AAAA

[pechtcha:~] AAAA=aaa eval 'echo $AAAA'
aaa
[pechtcha:~] AAAA=aaa sh -c 'echo $AAAA'
aaa
[pechtcha:~]

Does this help?
	Igor
-- 
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ZZZzz /,`.-'`'    -.  ;-;;,_		igor AT watson DOT ibm DOT com
     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski
    '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!

"Water molecules expand as they grow warmer" (C) Popular Science, Oct'02, p.51


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