From: "Berger, Daniel" <Daniel.Berger@...>
Date: 2006-08-26T06:49:17+09:00
Subject: Re: Can you temporarily turn off STDERR ??

> -----Original Message-----
> From: Stephen Veit [mailto:srveit@gmail.com] 
> Sent: Friday, August 25, 2006 3:32 PM
> To: ruby-talk ML
> Subject: Re: Can you temporarily turn off STDERR ??
> 
> 
> On 8/25/06, Berger, Daniel <Daniel.Berger@qwest.com> wrote:
> >
> > This comes up often enough that I wonder if allowing 
> IO#reopen to take 
> > a block would be a good idea:
> >
> > $stderr.reopen('/dev/null') do
> >    # Code here redirects to /dev/null
> > end
> >
> > # Code outside the block behaves normally
> >
> > I thought this idea had been brought up before, and that there was 
> > some downside to this, but I can't find any references to it now.
> >
> > Thoughts?
> >
> > - Dan
> 
> How about this?
> 
> #!/usr/bin/env ruby
> 
> # reopen_with_block.rb
> 
> class IO
> 
>   alias_method :_orig_reopen, :reopen
> 
>   def reopen(*args)
>     if block_given?
>       is_path = args.length == 2
>       path_or_io, mode_str = args
>       old_io = clone
>       path_or_io = File.open(path_or_io, mode_str || "w") if is_path
>       _orig_reopen(path_or_io)
>       begin
>         yield
>       ensure
>         _orig_reopen(old_io)
>         path_or_io.close if is_path
>       end
>     else
>       _orig_reopen(*args)
>     end
>   end
> 
> end
> 
> if $0 == __FILE__
>   $stderr.reopen('error_log', 'w') do
>     $stderr.puts "Stuff on error"
>     puts "normal stuff"
>   end
> 
>   File.open('error_log_2', "w") do |file|
>     $stderr.reopen(file) do
>       $stderr.puts "Stuff on error 2"
>       puts "normal stuff 2"
>     end
>   end
> 
>   $stderr.reopen('/dev/null') do
>     $stderr.puts "Stuff on error 3"
>     puts "normal stuff 3"
>   end
> 
>   # Make sure old way works
>   old_stderr = $stderr.clone
>   File.open('error_log_4', 'w') do |log_file|
>     $stderr.reopen(log_file)
>     begin
>       $stderr.puts "Stuff on error 4"
>       puts "normal stuff 4"
>     ensure
>       $stderr.reopen(old_stderr)
>     end
>   end
> 
>   begin
>     $stderr.reopen('error_log_5', 'w') do
>       $stderr.puts "Stuff on error 5"
>       puts "normal stuff 5"
>       raise "This message courtesy of raise"
>     end
>   rescue => e
>     puts e
>   end
> 
> end

Awesome.  Now, can we break this with threads?  Aredridel?

Of course, I wonder if IO#reopen is thread safe anyway, regardless of
the block. I've never seriously tested it.

Regards,

Dan 


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