From: Mark Hubbart <discord@...>
Date: 2004-09-26T15:22:18+09:00
Subject: Re: Nuby: How do I find out what exception was thrown?


On Sep 25, 2004, at 9:19 PM, Roy Pardee wrote:

> Thanks all for the responses.  I think the exception is not
> Errno::EACCES tho.  If I throw this at the end of my script:
>
> rescue Errno::EACCESS => exp
>    puts "In rescue section"
> end
>
> Ruby comes back with:
>
> F:\>ruby KillOwnerLok.rb
> KillOwnerLok.rb:18: syntax error
> rescue Errno::EACCESS => exp
>       ^
>
> I must be doing something very wrong, b/c if I change that to:
>
> rescue StandardError
>    puts "In rescue section"
> end
>
> Ruby says:
>
> F:\>ruby KillOwnerLok.rb
> KillOwnerLok.rb:18: syntax error
> rescue StandardError
>       ^
>
> Any further advice?



The rescue keyword can be used in two and a half different ways:

1. As a statement modifier:
   puts 0/0 rescue puts 23 # prints 23

2. In a begin...end block:
   begin
     puts 0/0
   rescue ZeroDivisionError => err
     puts 42
   end  # prints 42

2.5. Within other certain supported code blocks:
   def foo(bar, baz)
     bar/baz
   rescue ZeroDivisionError
     23
   rescue Exception
     42
   end

If it isn't used in one of these ways, it gives a parse error.  I 
suspect that's what the problem is; you just need to enclose the 
error-causing part of the script in a begin...end block, with a rescue 
clause.

cheers,
Mark






>
> Thanks!
>
> -Roy
>
> Tim Hunter <cyclists@nc.rr.com> wrote in message 
> news:<Wjj5d.7990$zA3.1670742@twister.southeast.rr.com>...
>> Roy Pardee wrote:
>>
>>> If I try to run this while the file in question is opened by another
>>> process I get this output:
>>>
>>> ------------------------------------------
>>> F:\>ruby KillOwnerLok.rb
>>> \\blackula\Profiles\Laurel\Application Data\Qualcomm\Eudora\owner.lok
>>> found!
>>> KillOwnerLok.rb:9:in `delete': Permission denied -
>>> \\blackula\Profiles\Laurel\Ap
>>> plication Data\Qualcomm\Eudora\owner.lok (Errno::EACCES)
>>>         from KillOwnerLok.rb:9
>>> ------------------------------------------
>>>
>>> I'd like to print my "Could not delete..." message in a rescue
>>> section, but I don't know how to translate the error message from the
>>> output into something 'rescuable'.  How do I do that?
>>
>> Ruby's telling you: Errno::EACCES
>>
>> rescue Errno::EACCES => exp
>>    puts "Caught an exception: #{exp.message}"
>> end
>>
>> But you probably want to catch other Errno's, too. You can catch them 
>> all by
>> rescuing StandardError. If you need to know exactly which exception 
>> was
>> thrown you can call `exp.class' in your rescue clause.
>