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Re: Second trap invocation is ignored?


From: Chet Ramey
Subject: Re: Second trap invocation is ignored?
Date: Sat, 11 Apr 2015 13:23:43 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

On 4/10/15 5:27 PM, Scott Bronson wrote:
> On Fri, Apr 10, 2015 at 8:16 AM, Chet Ramey <address@hidden> wrote:
>> On 4/6/15 11:58 AM, Greg Wooledge wrote:
>>> I'd be fine with that, but then why does "source ./foo" create a DEBUG
>>> trap at the global scope the *first* time?
>>
>> Because there's nothing to save and restore.
> 
> Just curious: why not restore the state of emptiness that
> existed before?  Why treat these two states differently?
> (presence of trap vs. absence of trap)

Two reasons: it worked better with the common case of sourcing a file that
provided a trap definition, and it paralleled how the -T option worked
with shell functions.

It's a bug that a DEBUG trap definition in a sourced file gets discarded
when an existing old value is restored.  That's inconsistent with how
source is supposed to work, since the shell doesn't have local trap
scoping.

Chet

-- 
``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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