2011/3/2 Albert Schlef <albertschlef / gmail.com>:
> Ruby tells the shell to execute the command (that's why you see "sh -c")
> [...]

Thanks for your explanations, but this is along the lines of what I
already understood.
I mentionned top to explain the problem more directly but I know that
the problem is not due do top; in fact, I already use htop on both
machines and the tree view showed me what I stated in my original
post.

To be more precise, the output of my script, on my Debian and Gentoo
machines, looks like this:
6750
1

These numbers are respectively the PID and parent PID of my process...init !

But on my Ubuntu machine, it's something like:
16055
16050

The first is the Ruby script's PID and the second is the PID of "sh -c".

-- 
Xavier NOELLE