From: Jan Svitok <jan.svitok@...>
Date: 2006-11-24T01:44:47+09:00
Subject: Re: invoke system command from within a method

On 11/22/06, Moritz Reiter <mreiter@agrav.org> wrote:
> Hi all,
>
> I am new to Ruby and want to make a Ruby script for the network
> configuration of my notebook as an exercise. Now I encountered a problem
> which is pretty strange to me:
>
> I want to invoke '/etc/init.d/networking restart' from within my Ruby
> program. If I create a file with the line
>
> %x{ /etc/init.d/networking restart }
>
> it works like I would expect. The networking init script gets invoked
> and correctly processed.
>
> But if I do something like this:
>
> - -->8--
> class Netconf
>         def restart
>                 puts %x{ /etc/init.d/networking restart }
>         end
> end
>
> netconf = Netconf.new
> netconf.restart
> - --8<--
>
> I get some output from the init script but it doesn't seem to actually
> do anything. It does not reconfigure my eth's in oppostion to the
> behaviour described above if don't make the system call from within a
> method.
>
> I would be very glad if anyone could give me a hint or point me to some
> documentation to enlighten me.

More blind tips:

1. try adding code to that %x{...} in smaller chunks:
(without class & puts, add method) def restart ; %x{...} ; end
(without method and class, add puts)
(add puts and method)

2. I suspect stderr might be a problem. Try adding 2>/dev/null
3. Try adding sh before the command
4. Have a look at the actual script and see what could be a problem.
Optionally add some traces there to see how far does it get.
5. The documentation is at Kernel#`, and the ultimate documentation is
in /usr/local/src/ruby/io.c, function rb_f_backquote() ;-)