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Re: typeset -r prevents local variable of same name.


From: Chet Ramey
Subject: Re: typeset -r prevents local variable of same name.
Date: Thu, 17 Feb 2011 22:18:20 -0500
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On 2/17/11 10:12 PM, Eric Blake wrote:
> On 02/17/2011 07:48 PM, Chet Ramey wrote:
>> Consider a quick, contrived example: an administrator writes a shell
>> package (library, set of functions, whatever) that includes, among
>> other things, ways to make sure that some other package is invoked with
>> a particular set of arguments and environment.  He does this in part by
>> declaring some variables readonly.  Programs invoked by this package
>> change their behavior depending on the value of environment variables,
>> so it's important to the correct operation of this script that the
>> variables don't change.  It should be harder to cirvumvent this, possibly
>> creating a security hole, than just declaring a shell function with a
>> local variable that then calls a public function that expects the variable
>> to have some other value.
> 
> Ah, so we're back to the debate of static vs. dynamic scoping.  

Not really.  The readonly variables could be declared at the global
scope.  Overriding a global variable can cause the same problem.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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