From: ara.t.howard@...
Date: 2007-02-23T23:54:54+09:00
Subject: Re: IO.popen on Windows to filter stdout

On Fri, 23 Feb 2007, Harold Hausman wrote:

>
> I believe that the underlying executable that I'm dealing with, namely
> VC8's "link.exe" is doing something very dastardly.
>

it sure looks like it!

>> it's hard to say without seeing your code, and the old code, but you could
>> try this to prove to yourself that stdout and stderr can be diverted:
>> 
>>    require 'tempfile'
>> 
>>    tmp = Tempfile.new Process.pid
>>    puts tmp.path
>> 
>>    cmd = "put the exact command here"
>> 
>>    STDOUT.reopen tmp.path
>>    STDERR.reopen tmp.path
>> 
>>    exec cmd
>> 
>
> When I integrate the above code, a tempfile is indeed created, but it
> remains empty. And what's more? I *still* see the output in the
> console! (:
>
> However, the following irb session indeed proves that stdout can be
> redirected. (as well as makes me laugh out loud)
>
> irb(main):001:0> require 'tempfile'
> => true
> irb(main):002:0> tmp = Tempfile.new Process.pid
> => #<File:C:/DOCUME~1/Harold/LOCALS~1/Temp/484.484.0>
> irb(main):003:0> STDOUT.reopen tmp.path

hmm.  then it looks like what's happening might depend on the nature of stdin,
i'd try one last thing

     require 'tempfile'

     i = Tempfile.new Process.pid
     o = Tempfile.new Process.pid
     e = Tempfile.new Process.pid
     puts i.path
     puts o.path
     puts e.path

     cmd = "put the exact command here"

     STDIN.reopen i.path
     STDOUT.reopen o.path
     STDERR.reopen e.path

     system cmd

alternatively


     require 'systemu'

     class Filter
       def initialize prefix, io
         @prefix = prefix
         @io = io
       end
       def << line
         @io << "#{ @prefix }: #{ line }"
       end
     end

     i = ''
     o = Filter.new 'stdout', STDOUT
     e = Filter.new 'stderr', STDERR

     systemu 'ruby -e"STDOUT.puts 42; STDERR.puts 42"', :stdin=>i, :stdout=>o, :stderr=>e

sorry i couldn't help more.

cheers.

-a
-- 
be kind whenever possible... it is always possible.
- the dalai lama