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Re: How to do? Possible?

From: Linda Walsh
Subject: Re: How to do? Possible?
Date: Mon, 25 Jul 2011 14:28:52 -0700
User-agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv: Gecko/20100228 Thunderbird/ Mnenhy/

Bob Proulx wrote:
> Linda Walsh wrote:
>> DJ Mills wrote:
>>>> Because a subshell cannot access the global variables of the parent.
>>> A subshell can access its parent's variables.  foo=bar; ( echo "$foo" )
>>> A sub process cannot, unless the variables are exported.  It does
>>> not sound like you need to do so here.
>>      I'm not sure about your terminology -- a subshell is a
>> subprocess.  By my understanding, "{}" defines a complex statement
>> and "()" defines both a subshell which is in a separate process,
> Yes, but it is a fork(2) of the parent shell and all of the variables
> from the parent are copied along with the fork into the child process
> and that includes non-exported variables.  Normally you would expect
> that a subprocess wouldn't have access to parent shell variables
> unless they were exported.  But with a subshell a copy of all
> variables are available.
> Bob

  Not really.
  It only seems that way because within () any "$xxxx" is usually
expanded BEFORE the () starts from the parent....

  You can see this by
  GLOBAL="hi there"
  (echo $GLOBAL)
prints out "hi there" as expected, but if we hide
$GLOBAL so it isn't seen by parent:
(foo=GLOBAL; echo ${!foo})
prints ""

So, they aren't really available in a subshell, only
that a subshell's contents are evaluated before the subshell is

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