From: ts <decoux@...>
Date: 2002-08-18T19:09:59+09:00
Subject: Re: How do I dup file descriptors in ruby?  (diverting STDERR)

>>>>> "R" == Richard Ryan <ryanr@12-253-103-174.client.attbi.com> writes:

R> Yes, those are right along the lines I was thinking, and that actually
R> was the first thing I tried but, and maybe I'm being too picky, if I
R> put that through irb and check $stderr.fileno I get something other
R> than 2.  That really  kind of bugs me for some reason.  It just don't
R> seem right.

 This is because you must use $stderr.reopen, something like this

pigeon% cat b.rb
#!/usr/bin/ruby
def redirect(*args)
   defout = $defout
   stdout = $stdout.clone
   stderr = $stderr.clone
   $defout = File.new *args
   $defout.sync = true
   $stdout.reopen($defout)
   $stderr.reopen($defout)
   yield
ensure
   $defout.close
   $stdout.reopen(stdout)
   $stderr.reopen(stderr)
   $defout = defout
end

redirect('aaa', 'w') do
   puts "hello world"
   puts $stdout.fileno
   puts $stderr.fileno
   system("ls -l nonexistent_file")
   system("ls /etc/passwd")
end
puts "Hello World"
puts $stdout.fileno
puts $stderr.fileno
system("ls -l nonexistent_file")
system("ls /etc/group")
pigeon% 

pigeon% b.rb
Hello World
1
2
ls: nonexistent_file: No such file or directory
/etc/group
pigeon% 

pigeon% cat aaa
hello world
1
2
ls: nonexistent_file: No such file or directory
/etc/passwd
pigeon% 

Guy Decoux