From: Martin Hansen <mail@...>
Date: 2010-08-06T18:58:45+09:00
Subject: Re: Abstracting exception handling

> What do you want the exception handler to do? Will the program still 
> terminate afterwards?

I want to write the exception type to a log file and terminate the 
script. $! does not tell the difference between interrupt, terminate, 
and quit (perhaps that could be fixed? - just a thought).

> If so, why not just add an at_exit handler?

 I have been messing around with this for a while, but I have failed to 
get it right - and now I am utterly confused.

If I have test.rb:

#!/usr/bin/env ruby

require 'my_aux_class'

Greet.new

raise "raise from main"


And my_aux_class.rb:

class Greet
  def initialize
    puts "Hello World"
  end
end

at_exit {
  puts "Last exception was #{$!.inspect}" if $!
}

begin
  exit_status = "OK"

  %w( INT TERM QUIT ).each do |signal|
    Signal.trap(signal) do
      exit_status = signal
      exit
    end
  end

  raise "raise from aux"
rescue Exception => exception
  puts "rescuing #{exception}"
  puts exception.backtrace
ensure
  puts "exit status: #{exit_status}"
end

Running this I get the following output:

rescuing raise from aux
/Users/maasha/my_aux_class.rb:21:in `<top (required)>'
./test.rb:3:in `require'
./test.rb:3:in `<main>'
exit status: OK
Hello World
Last exception was #<RuntimeError: raise from main>
./test.rb:7:in `<main>': raise from main (RuntimeError)


I actually wanted the raise from main rescued, but the 
begin/rescue/ensure is misplaced/misused :o(



Martin

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