From: Moritz Reiter <mreiter@...>
Date: 2006-11-24T17:16:30+09:00
Subject: Re: invoke system command from within a method

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Jan Svitok wrote:
 > 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)

Okay, I tried a few cases: The init script does not get processed
correctly no matter if it's in a class or just in a method or just at
very end of my whole script without puts or anything. BUT if put the
very same statment ( %x{ /etc/init.d/networking restart } into a
separate file as the only statement of the file (besides the hash
bang...) and execute this file, the init script does reconfigure my eth
correctly. I am mostly greatly confused...

> 2. I suspect stderr might be a problem. Try adding 2>/dev/null

That does not change the behaviour.

> 3. Try adding sh before the command

Neither does this.

> 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.

I looked into the script already. It does not much more than calling

ifdown -a --exclude=lo
ifup -a --exclude=lo

and some logging.

I added 'set -x' to the beginning of the init script and the output does
not look different. Only difference is that in once case my eth gets the
new IP, in the other it doesn't. So I suspect that the problem is
connected more to the ifdown/ifup binaries than to the init script itself.

> 5. The documentation is at Kernel#`, and the ultimate documentation is
> in /usr/local/src/ruby/io.c, function rb_f_backquote() ;-)

ri Kernel#\` does not reveal much info. Will have a look into API
documentation or something.
I don't have much hope to understand much of io.c as I never coded a
single line of C :-/

Maybe you or someone else have another idea after my information update?

- --
Moritz Reiter <mreiter@agrav.org>

GPG key fingerprint:
https://luna.agrav.org/~mo/gpg/

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