From: "Ara.T.Howard" <ahoward@...>
Date: 2004-07-23T05:02:01+09:00
Subject: Re: [NUBY] Reading stderr, stdout and the exit status of a process

On Fri, 23 Jul 2004, Alexey Verkhovsky wrote:

> Problem: call an external process, wait till it finishes, get its stdout
> and stderr as Strings, as well as the exit status.
>
> My current approximation of the solution:
>
> stdout = IO.popen("myprocess.sh").readlines
> exitStatus = $?
>
> It doesn't work. exitStatus comes out as nil. I probably understand why.
>
> Naturally, one can always bite the bullet and write the whole story
> (open a Process, attach two reader threads, direct all output streams
> into Ruby strings, wait till the Process quits, etc). This would be a
> lot of code for a common scripting task, and from past experiences doing
> same thing with C and Java, there are a few interesting surprises.
>
> Can some enlightened soul please show me The Ruby Way to do it all in
> one line? Reference to an appropriate page in the Pickaxe that I should
> have RTFM'd not to ask this silly question would be even better :)
>
> Domo arigato in advance.
>
> Best regards,
> Alexey Verkhovsky


see http://raa.ruby-lang.org/project/session/

example:

   jib:~ > cat a.rb
   require 'session'

   sh = Session.new

   #
   # example 0
   #
   puts '---'
   stdout, stderr = sh.execute 'ls no-exist'
   puts "stdout     : #{ stdout }"
   puts "stderr     : #{ stderr }"
   puts "exitstatus : #{ sh.exitstatus }"

   #
   # example 1
   #
   puts '---'
   sh.execute("ls #{ __FILE__ }") do |stdout,stderr|
     puts "stdout     : #{ stdout }" if stdout
     puts "stderr     : #{ stderr }" if stderr
   end
   puts "exitstatus : #{ sh.exitstatus }"

   #
   # example 2
   #
   puts '---'
   sh.outproc = proc{|stdout| puts "stdout     : #{ stdout }"}
   sh.errproc = proc{|stderr| puts "stderr     : #{ stderr }"}
   sh.execute 'echo $$'
   puts "exitstatus : #{ sh.exitstatus }"


   jib:~ > ruby a.rb
   ---
   stdout     :
   stderr     : ls: no-exist: No such file or directory
   exitstatus : 1
   ---
   stdout     : a.rb
   exitstatus : 0
   ---
   stdout     : 16452
   exitstatus : 0


you can do almost all of this using open3, but not exitstatus.  it also
requires you to spawn a new process for every command if you want to
distinguish output.

regards.


-a
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