From: Robert Klemme <shortcutter@...>
Date: 2009-08-25T15:25:07+09:00
Subject: Re: Asynchronous process to process pipe IO

On 24.08.2009 22:54, Pito Salas wrote:
> Robert Klemme wrote:
>> On 24.08.2009 22:16, Joel VanderWerf wrote:
>>>>         i = 0
>>>>
>>>>
>>>        i = i+1
>>>      end
>>>    else
>>>      exec("ruby -e '3.times {|i| p i; sleep 1}'")
>>>    end
>>> end
>>>
>>> Does it work that way for you?
>> Why are you guys using such a complex construction?  If you just want to
>> see the output when it comes why not just:
>>
>> system "./iacommand.rb"
>>
>> Or maybe this, if you need to process the output:
>>
>> IO.popen "./iacommand.rb" do |io|
>>    io.each_line do |line|
>>      puts line
>>    end
>> end
>>
>> Note, you may have to do $stdout.sync = true in "iacommand.rb".
>>
>> Kind regards
>>
>>   robert
> 
> Robert,
> 
> Thanks, the $stdout.sync = true was the magic bullet.
> 
> Now, I am not exactly clear (reading the doc) about the difference 
> between exec and system... I do need to be able to send command line 
> arguments to iacommand.rb and I do indeed need to process the output 'as 
> it appears.'

Then you'll want to use one of the popen family of functions.  Even with 
IO.popen you can pass arguments:

IO.popen ["./iacommand.rb", "arg", "arg"] do |io|
   ...
end

Note, if you also want to write to the process's stdin, you need to 
provide a file mode as second argument.  See docs.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/