From: Gregory Millam <walker@...>
Date: 2004-04-28T16:51:09+09:00
Subject: Re: popen, popen3, and leftover processes

Received: Wed, 28 Apr 2004 16:43:35 +0900
And lo, nobu.nokada@softhome.net wrote:

> Hi,
> 
> At Wed, 28 Apr 2004 16:08:58 +0900,
> Hal Fulton wrote in [ruby-talk:98616]:
> > > No need for a pid
> > > 
> > > Process.wait
> > 
> > Hmm, but I don't want to wait for it. I want to make sure the process
> > dies. I think io.pid may be the way to go.
> 
> You don't need to wait for IO.popen, popen'ed IO waits the
> child process at close.  However, popen3 spawns child and
> grand-child process which the command is executed as, so you
> cannot wait the real command.  This restriction is to get rid
> of leaving a zombie process.

Hmm. .. right, I never knew that :D.

irb(main):001:0> f = IO.popen("fortune")
=> #<IO:0x402be42c>
irb(main):002:0> f.read
=> "Do not meddle in the affairs of wizards, for they become soggy and hard to\nlight.\n\nDo not throw cigarette butts in the urinal, for they are subtle and\nquick to anger.\n"

# ps aux with irb running shows fortune <defunct>

irb(main):003:0> f.close

# ps aux with irb still running shows no fortune.

Thanks, good to know.