From: Holden Glova <dsafari@...>
Date: 2000-12-30T12:31:17+09:00
Subject: [ruby-talk:8322] open3 woes [sort of long]

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Seems as though I can't seem to take any steps forward on this problem, only 
sideways. Maybe someone here can give me the push in the back needed to move 
me forwards.

Dave Thomas has recommended the use of open3 instead of using backquotes with 
stderr redirection enclosed within the backquotes for platform portability 
reasons, a wise recommendation might I add. So the previously backquoted 
command:
`ruby -w #{file} 2>&1`

Which for some reason didn't work when run through the testing framwork (this 
still bothers me as to why it didn't work) has changed into:
streams = Open3.popen3("ruby -w #{file}")

While this seems to be working so far, i have a new error (hence my mention 
of sideways steps). Now it seems to be appending the "file" to itself and 
copying the contents before it is running the command. Let me try and clarify.

i pass this file (useless.rb) into the previous command:
class Useless
 
        def meth
                puts "Useless method in a useless class"
        end
end
u = Useless.new()
u.meth()

I run this through another class called RuntimeInterpreter, here is it's 
contents:
require 'open3'
 
class RuntimeInterpreter
 
        def invoke(file)
                streams = Open3.popen3("ruby -w #{file}")
                streams.at(1).each() { |line|
                        puts line
                }
        end
end

I finally test this out through the testing framework as follows:
require 'runit/testcase'
require 'runtimeInterpreter'
 
class Test_RuntimeInterpreter < RUNIT::TestCase
 
  def testInvoke
    interpreter = RuntimeInterpreter.new()
    result = interpreter.invoke("../useless.rb")
 
    assert(result == "Useless method in a useless class")
  end
end

After I run my tests, it seems to have appended the entire contents of 
useless.rb to itself, so i end up with this after the first time I run it, 
each successive run appends the entire contents itself yet again.
class Useless
 
        def meth
                puts "Useless method in a useless class"
        end
end
u = Useless.new()
u.meth()
class Useless
 
        def meth
                puts "Useless method in a useless class"
        end
end
u = Useless.new()
u.meth()

What the heck is going on here? I can't find any real documentation on what 
open3 does, aside from looking at the code which honestly doesn't make too 
much sense to me. From what I gather so far it should simply return me 3 
separate file descriptors respectively for stdin, stdout, and stderr. Should 
it also copy the file contents to itself? How have i messed up? Can anyone 
please help me out before I commit myself to the funny farm?

- -- 
Signed,
Holden Glova
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