From: "Cai I." <cai.inception@...>
Date: 2010-11-11T03:38:09+09:00
Subject: Re: Can I run windows command line app interactively?

Jeremy Bopp wrote in post #959348:
> On 11/4/2010 3:52 AM, Cai I. wrote:
>>
>>     # run a command line application
>>     @session.puts('robocopy.exe ......')
>>     @session.each do |line|
>>       p line
>>     end
>>
>> The issue is that "@session.each" never stop. It waits when cmd.exe
>> waiting for input. So the scripts hang.
>
> The problem is that @session.each will run until the input stream is
> closed, in this case until cmd.exe exits.  What you want to do is have
> it run only until you get the next prompt waiting for input.  For that
> you need to use something like the expect module:
>
> require 'expect'
> session = IO.popen('cmd.exe', 'r+')
> session.puts('dir')
> session.expect(/[CD]:\\.*>/) do
>   session.puts('robocopy.exe ......')
> end
> session.expect(/[CD]:\\.*>/) do
>   session.puts('exit')
> end
> session.close
>
>
> The only problem with this solution is that you won't be able to see the
> output of the commands you run this way.  That output is consumed by
> #expect, and I don't know of a way to make it print what it consumes.
> Of course another way to handle your exact example is something like
> this:
>
> system('dir && robocopy.exe .......')
>
>
> As long as you don't intend to process the output of commands along the
> way in order to change how you run the subsequent commands, this should
> work for you.  If you *do* want to process the output then you could run
> each command in a separate session and read the output in between each
> session:
>
> session = IO.popen('dir')
> session.each do |line|
>   puts line
> end
> session.close
>
> session = IO.popen('robocopy.exe .....')
> session.each do |line|
>   puts line
> end
> session.close
>
>
> -Jeremy

Thanks a lot Jeremy for reply.

I have to get the output for parsing in my scenario, and I finally got 
it done by monitoring the output and stop read when the prompt found, I 
guess it likes what the "expect" does. If no prompt found, I will parse 
out each line and get it processed.

I found the function ios.readpartial() very useful in this scenario. I 
use it to read output from cmd.exe. It won't get blocked at the end of 
output as long as it has read something. I guess it just read what in 
the system buffer and return and it only block when nothing left in 
buffer to read.

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