From: ara.t.howard@...
Date: 2007-02-23T12:07:16+09:00
Subject: Re: IO.popen on Windows to filter stdout

On Fri, 23 Feb 2007, Harold Hausman wrote:

>
> Hi Ara, thanks for taking the time to try and help me. What you're
> saying about stderr here sounds right to me, but I tried what you have
> above, and I'm still seeing the output I'm trying to 'squash' (read:
> block) ... Here is my code:
> #########################
> puts "ruby-link in the house!"
> the_cmd = "old-Link.exe "
> ARGV.each do |arg|
> 	the_cmd << "\"#{arg}\" "
> end
>
> the_cmd << "2>&1"
>
> puts "Calling: #{the_cmd}"
>
> IO.popen( the_cmd )
> #########################
>
> And here is the output that I see: (apologies for badly wrapped lines)
> ruby-link in the house!
> Calling: old-Link.exe "@C:\long\path\to\some.rsp" "/NOLOGO"
> "/ERRORREPORT:PROMPT" 2>&1
> OLD-LINK :
> <snip about 200k of nasty output from old-Link.exe>

hrrrm.  this is a windozing type thing, but is it perhaps manipulating the
console directly?  for instance, in unix, this can happen.

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

this should dump everything into a tempfile.  if it does, then you should be
able to manipulate the code with popen fine.


>
> ------
> So yeah, the output from old-Link.exe is still being filtered up to
> the top and seen. What I'm looking for is a way to shut it up... ;)
>
>> alternatively, you may want to use systemu
>> 
>>    http://codeforpeople.com/lib/ruby/systemu
>> 
> I looked at systemu and it's not clear how it would help with this
> problem. :| Apologies if I'm being dense.

   harp:~ > cat a.rb
   require 'systemu'

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

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

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


   harp:~ > ruby a.rb
   stdout: 42
   stderr: 42



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