From: Robert Klemme <bob.news@...>
Date: 2005-11-03T04:27:08+09:00
Subject: Re: Trapping errors.

Hugh Sasse <hgs@dmu.ac.uk> wrote:
> On Thu, 3 Nov 2005, Robert Klemme wrote:
>
>> Hugh Sasse wrote:
>>> On Thu, 3 Nov 2005, Robert Klemme wrote:
>>>
>>>> Hugh Sasse wrote:
>>>>> I see my changes to fileutils are now in the Ruby CVS.
>>>>> However, even with
>>>>>   rescue Exception, SystemCallError => e
>>>>> or
>>>>>   rescue Exception, Errno::EACCES, Errno::EBUSY => e
>>>>>
>>>>> I still cannot trap this error.  From the call stack this part of
>>>>> the code is being used, so why won't the error cause ruby to go
>>>>> back up the callstack until it finds this rescue clause?
>>>>
>>>> Maybe there's another rescue clause that is closer to the place
>>>> where the exception is thrown...
>>>
>>> But unless I have completely misunderstood the point of rescue, even
>>> if that calls raise, the exception will still be caught by my
>>> enclosing rescue.
>>
>> But who guarantees that the other rescue clause actually throws
>> again?  If it doesn't you can't catch it.
>>
>> ....
>> rescue Exception => e
>>   puts "Catch me if you can >:-}"
>> end
>>
>> ;-)
>>
>
> Then it's already caught, and I should never see the error.

Why not?  If it's printed in the other rescue clause you would see it.  Or 
am I missing something here?

    robert

>
> neelix hgs 58 %> irb
> irb(main):001:0> begin
> irb(main):002:1*   begin
> irb(main):003:2*     raise StandardError
> irb(main):004:2>   rescue => e
> irb(main):005:2>     puts "catch me if you can #{e}"
> irb(main):006:2>   end
> irb(main):007:1> rescue
> irb(main):008:1>   puts "caught something"
> irb(main):009:1> end
> catch me if you can StandardError
> => nil
> irb(main):010:0>
>
> i.e. that's a normal exit.
>
> So, I have an error that is not already caught, and I can't catch
> it.
>
>> Cheers
>>
>>     robert
>>
>
>        Hugh