From: Joe Van Dyk <joevandyk@...>
Date: 2005-06-28T05:52:44+09:00
Subject: Re: redirecting STDOUT

Nevermind, it does work!  

My test application was the following Ruby application:

#!/bin/env ruby
while true
  puts "pid: #{Process.pid}, time: #{Time.now}"
  sleep 0.2
  puts 
end

Does #puts not write to STDOUT by default?


On 6/27/05, gwtmp01@mac.com <gwtmp01@mac.com> wrote:
> 
> On Jun 27, 2005, at 1:37 PM, Joe Van Dyk wrote:
> > Why doesn't this work?
> 
> Disclaimer: I'm pretty good with Unix System stuff
> but still learning on the Ruby so...
> 
> > (#executable is a function that returns a string that contains a test
> > application that spits out some data)
> >
> >   def start
> >     pid = fork
> >     if pid.nil?              # In child
> >       log = File.open(executable + ".log", "w")
> >       STDOUT.reopen(log)
> >       STDERR.reopen(log)
> >       exec executable        # Start program
> >       exit
> >     else                     # In parent
> >       @pid = pid             # Record new process id
> >       Process.detach @pid    # If the process dies, let it die
> >       monitor                # Start monitoring the process' status
> >     end
> >   end
> 
> This worked for me (Mac OS X 10.4, Ruby 1.8.2).  Check the permissions
> on the log file. If was created in earlier tests as a read-only file
> maybe
> that is why the program fails now.
> 
> If you have something like ktrace or truss on your system, trace
> the ruby program and then look at the dump.  You can see exactly
> what system calls are being made (open/read/write/etc) and also
> what errors, if any, are being returned.
> 
> Try using some standard program such as /bin/date instead of executable
> just to make sure it isn't a problem with your test program.  You'll
> probably want a different path for the log file in that case.
> 
> If 'monitor' is going to watch the child process then just incorporate
> calls to Process.wait(@pid) as part of 'monitor' instead of
> Process.detach.  If you have both Process.detach and monitor
> periodically
> calling Process.wait, you'll never be sure which thread is going to
> catch the exiting child.
> 
> 
> 
> Gary Wright
> 
> 
>