From: JamesBritt <james@...>
Date: 2002-07-19T10:42:30+09:00
Subject: RE: Can you only catch errors one level deep?


>
> I guess you could examine the backtrace:
>
>   rescue LoadError => e
>   b = e.backtrace
>
>   # now look at the size of b ...
>
> I'm sort of winging it here -- not sure if there are conditions under
> which this would or wouldn't work.

Some quick empirical study suggests that if the immediate require fails, the
backtrace is of size 2, the first item giving
  filename:line_number:message,
the second giving
  filename:line number

If the required file itself has a require problem, then backtrace is of size
4.

e.g., where faketest.rb is the main script, requiring 'fake1' (which in turn
requires a nonexistent file, the root cause of the error)


  begin
    require 'fake1'
  rescue LoadError
    puts $!.backtrace.size
    print $!.backtrace.each_index{ |x| puts "backtrace #{x} =
#{$!.backtrace[x]}"}
  end

  # prints
  4
  backtrace 0 = ./fake1.rb:1:in `require'
  backtrace 1 = ./fake1.rb:1
  backtrace 2 = faketest.rb:2:in `require'
  backtrace 3 = faketest.rb:2


James


>
>
> David
>
> --
> David Alan Black
> home: dblack@candle.superlink.net
> work: blackdav@shu.edu
> Web:  http://pirate.shu.edu/~blackdav
>