From: Dave Burt <dave@...>
Date: 2006-06-03T18:14:27+09:00
Subject: Re: Exceptions inside loops...

darren kirby wrote:
> begin telnetPorts.each do |port|
>    puts "Port " + port.to_s + ":"
>    t = TCPSocket.new(host,port)
>    banner = t.gets
>    t.close
> end
> 
> rescue SystemCallError
>    puts "Unable to connect to port: " + $!
> end

I see the question has been answered; let me just explain a little further.

Here's the code you posted above with standard indentation:

begin
  telnetPorts.each do |port|
    puts "Port " + port.to_s + ":"
    t = TCPSocket.new(host,port)
    banner = t.gets
    t.close
  end
rescue SystemCallError
   puts "Unable to connect to port: " + $!
end

The first "end" closes the do..end block given to the each method. The
second end closes the begin..end block. The rescue clause applies to the
begin..end block.

(Obviously) begin..end is used to introduce a new scope, often for
exception handling like you're doing here, but you can see that if an
exception is caught, you end up outside the loop. If you added a "retry"
or "redo" to the rescue clause, you'd simply start the loop again from
the top.

You can add rescue clauses inside begin..end blocks and also def..end
method bodies:

def barf
  raise "some exception"
rescue RuntimeError
  puts "some exception was raised"
end

Now you can go back to your already-working solution from Mike
Fletcher's post.

Cheers,
Dave